Run clang-tidy’s modernize-use-nullptr pass.

This replaces all NULL or 0 with nullptr when assigned to or returned as
a pointer.

85 files changed, 1024 insertions, 1024 deletions

diff --git a/src/extension/db.cpp b/src/extension/db.cpp
index e885d3531..8d6ad7e0e 100644
--- a/src/extension/db.cpp
+++ b/src/extension/db.cpp
@@ -112,8 +112,8 @@ struct ModuleOutputCmp {
 void
 DB::register_ext (Extension *module)
 {
-	g_return_if_fail(module != NULL);
-	g_return_if_fail(module->get_id() != NULL);
+	g_return_if_fail(module != nullptr);
+	g_return_if_fail(module->get_id() != nullptr);
 
 	// only add to list if it's a never-before-seen module
         bool add_to_list = 
@@ -134,8 +134,8 @@ DB::register_ext (Extension *module)
 void
 DB::unregister_ext (Extension * module)
 {
-	g_return_if_fail(module != NULL);
-	g_return_if_fail(module->get_id() != NULL);
+	g_return_if_fail(module != nullptr);
+	g_return_if_fail(module->get_id() != nullptr);
 
 	// printf("Extension DB: removing %s\n", module->get_id());
 	moduledict.erase(moduledict.find(module->get_id()));
@@ -157,11 +157,11 @@ DB::unregister_ext (Extension * module)
 Extension *
 DB::get (const gchar *key)
 {
-        if (key == NULL) return NULL;
+        if (key == nullptr) return nullptr;
 
 	Extension *mod = moduledict[key];
 	if ( !mod || mod->deactivated() )
-		return NULL;
+		return nullptr;
 
 	return mod;
 }
diff --git a/src/extension/db.h b/src/extension/db.h
index 0014f4449..73e735ac0 100644
--- a/src/extension/db.h
+++ b/src/extension/db.h
@@ -36,9 +36,9 @@ private:
         to find the different extensions in the hash map. */
     struct ltstr {
         bool operator()(const char* s1, const char* s2) const {
-            if ( (s1 == NULL) && (s2 != NULL) ) {
+            if ( (s1 == nullptr) && (s2 != nullptr) ) {
                 return true;
-            } else if (s1 == NULL || s2 == NULL) {
+            } else if (s1 == nullptr || s2 == nullptr) {
                 return false;
             } else {
                 return strcmp(s1, s2) < 0;
diff --git a/src/extension/dependency.cpp b/src/extension/dependency.cpp
index 5e843ee11..07462e5e7 100644
--- a/src/extension/dependency.cpp
+++ b/src/extension/dependency.cpp
@@ -51,20 +51,20 @@ Dependency::Dependency (Inkscape::XML::Node * in_repr)
     _type = TYPE_FILE;
     _location = LOCATION_PATH;
     _repr = in_repr;
-    _string = NULL;
-    _description = NULL;
+    _string = nullptr;
+    _description = nullptr;
 
     Inkscape::GC::anchor(_repr);
 
     if (const gchar * location = _repr->attribute("location")) {
-        for (int i = 0; i < LOCATION_CNT && location != NULL; i++) {
+        for (int i = 0; i < LOCATION_CNT && location != nullptr; i++) {
             if (!strcmp(location, _location_str[i])) {
                 _location = (location_t)i;
                 break;
             }
         }
     } else if (const gchar * location = _repr->attribute("reldir")) {
-        for (int i = 0; i < LOCATION_CNT && location != NULL; i++) {
+        for (int i = 0; i < LOCATION_CNT && location != nullptr; i++) {
             if (!strcmp(location, _location_str[i])) {
                 _location = (location_t)i;
                 break;
@@ -73,7 +73,7 @@ Dependency::Dependency (Inkscape::XML::Node * in_repr)
     }
     
     const gchar * type = _repr->attribute("type");
-    for (int i = 0; i < TYPE_CNT && type != NULL; i++) {
+    for (int i = 0; i < TYPE_CNT && type != nullptr; i++) {
         if (!strcmp(type, _type_str[i])) {
             _type = (type_t)i;
             break;
@@ -83,7 +83,7 @@ Dependency::Dependency (Inkscape::XML::Node * in_repr)
     _string = _repr->firstChild()->content();
 
     _description = _repr->attribute("description");
-    if (_description == NULL)
+    if (_description == nullptr)
         _description = _repr->attribute("_description");
 
     return;
@@ -133,12 +133,12 @@ bool Dependency::check (void) const
 {
     // std::cout << "Checking: " << *this << std::endl;
 
-    if (_string == NULL) return FALSE;
+    if (_string == nullptr) return FALSE;
 
     switch (_type) {
         case TYPE_EXTENSION: {
             Extension * myext = db.get(_string);
-            if (myext == NULL) return FALSE;
+            if (myext == nullptr) return FALSE;
             if (myext->deactivated()) return FALSE;
             break;
         }
@@ -171,7 +171,7 @@ bool Dependency::check (void) const
                 default: {
                     gchar * path = g_strdup(g_getenv("PATH"));
 
-                    if (path == NULL) {
+                    if (path == nullptr) {
                         /* There is no `PATH' in the environment.
                            The default search path is the current directory */
                         path = g_strdup(G_SEARCHPATH_SEPARATOR_S);
@@ -179,7 +179,7 @@ bool Dependency::check (void) const
 
                     gchar * orig_path = path;
 
-                    for (; path != NULL;) {
+                    for (; path != nullptr;) {
                         gchar * local_path; // to have the path after detection of the separator
                         Glib::ustring final_name;
 
@@ -188,7 +188,7 @@ bool Dependency::check (void) const
                         /* Not sure whether this is UTF8 happy, but it would seem
                            like it considering that I'm searching (and finding)
                            the ':' character */
-                        if (path != NULL) {
+                        if (path != nullptr) {
                             path[0] = '\0';
                             path++;
                         }
@@ -255,7 +255,7 @@ operator<< (std::ostream &out_file, const Dependency & in_dep)
     out_file << _("  location: ") << _(in_dep._location_str[in_dep._location]) << '\n';
     out_file << _("  string: ") << in_dep._string << '\n';
 
-    if (in_dep._description != NULL) {
+    if (in_dep._description != nullptr) {
         out_file << _("  description: ") << _(in_dep._description) << '\n';
     }
 
diff --git a/src/extension/effect.cpp b/src/extension/effect.cpp
index 0a9b56ed6..8be5287a2 100644
--- a/src/extension/effect.cpp
+++ b/src/extension/effect.cpp
@@ -26,9 +26,9 @@
 namespace Inkscape {
 namespace Extension {
 
-Effect * Effect::_last_effect = NULL;
-Inkscape::XML::Node * Effect::_effects_list = NULL;
-Inkscape::XML::Node * Effect::_filters_list = NULL;
+Effect * Effect::_last_effect = nullptr;
+Inkscape::XML::Node * Effect::_effects_list = nullptr;
+Inkscape::XML::Node * Effect::_filters_list = nullptr;
 
 #define  EFFECTS_LIST  "effects-list"
 #define  FILTERS_LIST  "filters-list"
@@ -37,12 +37,12 @@ Effect::Effect (Inkscape::XML::Node * in_repr, Implementation::Implementation *
     : Extension(in_repr, in_imp),
       _id_noprefs(Glib::ustring(get_id()) + ".noprefs"),
       _name_noprefs(Glib::ustring(_(get_name())) + _(" (No preferences)")),
-      _verb(get_id(), get_name(), NULL, NULL, this, true),
-      _verb_nopref(_id_noprefs.c_str(), _name_noprefs.c_str(), NULL, NULL, this, false),
-      _menu_node(NULL), _workingDialog(true),
-      _prefDialog(NULL)
+      _verb(get_id(), get_name(), nullptr, nullptr, this, true),
+      _verb_nopref(_id_noprefs.c_str(), _name_noprefs.c_str(), nullptr, nullptr, this, false),
+      _menu_node(nullptr), _workingDialog(true),
+      _prefDialog(nullptr)
 {
-    Inkscape::XML::Node * local_effects_menu = NULL;
+    Inkscape::XML::Node * local_effects_menu = nullptr;
 
     // This is a weird hack
     if (!strcmp(this->get_id(), "org.inkscape.filter.dropshadow"))
@@ -53,9 +53,9 @@ Effect::Effect (Inkscape::XML::Node * in_repr, Implementation::Implementation *
     no_doc = false;
     no_live_preview = false;
 
-    if (repr != NULL) {
+    if (repr != nullptr) {
 
-        for (Inkscape::XML::Node *child = repr->firstChild(); child != NULL; child = child->next()) {
+        for (Inkscape::XML::Node *child = repr->firstChild(); child != nullptr; child = child->next()) {
             if (!strcmp(child->name(), INKSCAPE_EXTENSION_NS "effect")) {
                 if (child->attribute("needs-document") && !strcmp(child->attribute("needs-document"), "false")) {
                   no_doc = true;
@@ -63,7 +63,7 @@ Effect::Effect (Inkscape::XML::Node * in_repr, Implementation::Implementation *
                 if (child->attribute("needs-live-preview") && !strcmp(child->attribute("needs-live-preview"), "false")) {
                   no_live_preview = true;
                 }
-                for (Inkscape::XML::Node *effect_child = child->firstChild(); effect_child != NULL; effect_child = effect_child->next()) {
+                for (Inkscape::XML::Node *effect_child = child->firstChild(); effect_child != nullptr; effect_child = effect_child->next()) {
                     if (!strcmp(effect_child->name(), INKSCAPE_EXTENSION_NS "effects-menu")) {
                         // printf("Found local effects menu in %s\n", this->get_name());
                         local_effects_menu = effect_child->firstChild();
@@ -90,13 +90,13 @@ Effect::Effect (Inkscape::XML::Node * in_repr, Implementation::Implementation *
     // \TODO this gets called from the Inkscape::Application constructor, where it initializes the menus.
     // But in the constructor, our object isn't quite there yet!
     if (Inkscape::Application::exists() && INKSCAPE.use_gui()) {
-        if (_effects_list == NULL)
+        if (_effects_list == nullptr)
             _effects_list = find_menu(INKSCAPE.get_menus(), EFFECTS_LIST);
-        if (_filters_list == NULL)
+        if (_filters_list == nullptr)
             _filters_list = find_menu(INKSCAPE.get_menus(), FILTERS_LIST);
     }
 
-    if ((_effects_list != NULL || _filters_list != NULL)) {
+    if ((_effects_list != nullptr || _filters_list != nullptr)) {
         Inkscape::XML::Document *xml_doc;
         xml_doc = _effects_list->document();
         _menu_node = xml_doc->createElement("verb");
@@ -123,22 +123,22 @@ Effect::merge_menu (Inkscape::XML::Node * base,
                     Inkscape::XML::Node * pattern,
                     Inkscape::XML::Node * merge) {
     Glib::ustring mergename;
-    Inkscape::XML::Node * tomerge = NULL;
-    Inkscape::XML::Node * submenu = NULL;
+    Inkscape::XML::Node * tomerge = nullptr;
+    Inkscape::XML::Node * submenu = nullptr;
 
     /* printf("Merge menu with '%s' '%s' '%s'\n",
             base != NULL ? base->name() : "NULL",
             pattern != NULL ? pattern->name() : "NULL",
             merge != NULL ? merge->name() : "NULL"); */
 
-    if (pattern == NULL) {
+    if (pattern == nullptr) {
         // Merge the verb name
         tomerge = merge;
         mergename = _(this->get_name());
     } else {
         gchar const * menuname = pattern->attribute("name");
-        if (menuname == NULL) menuname = pattern->attribute("_name");
-        if (menuname == NULL) return;
+        if (menuname == nullptr) menuname = pattern->attribute("_name");
+        if (menuname == nullptr) return;
         
         Inkscape::XML::Document *xml_doc;
         xml_doc = base->document();
@@ -150,28 +150,28 @@ Effect::merge_menu (Inkscape::XML::Node * base,
 
     int position = -1;
 
-    if (start != NULL) {
+    if (start != nullptr) {
         Inkscape::XML::Node * menupass;
-        for (menupass = start; menupass != NULL && strcmp(menupass->name(), "separator"); menupass = menupass->next()) {
-            gchar const * compare_char = NULL;
+        for (menupass = start; menupass != nullptr && strcmp(menupass->name(), "separator"); menupass = menupass->next()) {
+            gchar const * compare_char = nullptr;
             if (!strcmp(menupass->name(), "verb")) {
                 gchar const * verbid = menupass->attribute("verb-id");
                 Inkscape::Verb * verb = Inkscape::Verb::getbyid(verbid);
-                if (verb == NULL) {
+                if (verb == nullptr) {
 					g_warning("Unable to find verb '%s' which is referred to in the menus.", verbid);
                     continue;
                 }
                 compare_char = verb->get_name();
             } else if (!strcmp(menupass->name(), "submenu")) {
                 compare_char = menupass->attribute("name");
-                if (compare_char == NULL)
+                if (compare_char == nullptr)
                     compare_char = menupass->attribute("_name");
             }
 
             position = menupass->position() + 1;
 
             /* This will cause us to skip tags we don't understand */
-            if (compare_char == NULL) {
+            if (compare_char == nullptr) {
                 continue;
             }
 
@@ -179,7 +179,7 @@ Effect::merge_menu (Inkscape::XML::Node * base,
 
             if (mergename == compare) {
                 Inkscape::GC::release(tomerge);
-                tomerge = NULL;
+                tomerge = nullptr;
                 submenu = menupass;
                 break;
             }
@@ -191,15 +191,15 @@ Effect::merge_menu (Inkscape::XML::Node * base,
         } // for menu items
     } // start != NULL
 
-    if (tomerge != NULL) {
+    if (tomerge != nullptr) {
         base->appendChild(tomerge);
         Inkscape::GC::release(tomerge);
         if (position != -1)
             tomerge->setPosition(position);
     }
 
-    if (pattern != NULL) {
-        if (submenu == NULL)
+    if (pattern != nullptr) {
+        if (submenu == nullptr)
             submenu = tomerge;
         merge_menu(submenu, submenu->firstChild(), pattern->firstChild(), merge);
     }
@@ -210,7 +210,7 @@ Effect::merge_menu (Inkscape::XML::Node * base,
 Effect::~Effect (void)
 {
     if (get_last_effect() == this)
-        set_last_effect(NULL);
+        set_last_effect(nullptr);
     if (_menu_node)
         Inkscape::GC::release(_menu_node);
     return;
@@ -222,9 +222,9 @@ Effect::check (void)
     if (!Extension::check()) {
         /** \todo  Check to see if parent has this as its only child,
                    if so, delete it too */
-        if (_menu_node != NULL)
+        if (_menu_node != nullptr)
             sp_repr_unparent(_menu_node);
-        _menu_node = NULL;
+        _menu_node = nullptr;
         return false;
     }
     return true;
@@ -233,7 +233,7 @@ Effect::check (void)
 bool
 Effect::prefs (Inkscape::UI::View::View * doc)
 {
-    if (_prefDialog != NULL) {
+    if (_prefDialog != nullptr) {
         _prefDialog->raise();
         return true;
     }
@@ -247,7 +247,7 @@ Effect::prefs (Inkscape::UI::View::View * doc)
         set_state(Extension::STATE_LOADED);
     if (!loaded()) return false;
 
-    _prefDialog = new PrefDialog(this->get_name(), this->get_help(), NULL, this);
+    _prefDialog = new PrefDialog(this->get_name(), this->get_help(), nullptr, this);
     _prefDialog->show();
 
     return true;
@@ -312,12 +312,12 @@ Effect::set_last_effect (Effect * in_effect)
         if (strncmp(verb_id, help_id_prefix, strlen(help_id_prefix)) == 0) return;
     }
 
-    if (in_effect == NULL) {
-        Inkscape::Verb::get(SP_VERB_EFFECT_LAST)->sensitive(NULL, false);
-        Inkscape::Verb::get(SP_VERB_EFFECT_LAST_PREF)->sensitive(NULL, false);
-    } else if (_last_effect == NULL) {
-        Inkscape::Verb::get(SP_VERB_EFFECT_LAST)->sensitive(NULL, true);
-        Inkscape::Verb::get(SP_VERB_EFFECT_LAST_PREF)->sensitive(NULL, true);
+    if (in_effect == nullptr) {
+        Inkscape::Verb::get(SP_VERB_EFFECT_LAST)->sensitive(nullptr, false);
+        Inkscape::Verb::get(SP_VERB_EFFECT_LAST_PREF)->sensitive(nullptr, false);
+    } else if (_last_effect == nullptr) {
+        Inkscape::Verb::get(SP_VERB_EFFECT_LAST)->sensitive(nullptr, true);
+        Inkscape::Verb::get(SP_VERB_EFFECT_LAST_PREF)->sensitive(nullptr, true);
     }
 
     _last_effect = in_effect;
@@ -327,21 +327,21 @@ Effect::set_last_effect (Effect * in_effect)
 Inkscape::XML::Node *
 Effect::find_menu (Inkscape::XML::Node * menustruct, const gchar *name)
 {
-    if (menustruct == NULL) return NULL;
+    if (menustruct == nullptr) return nullptr;
     for (Inkscape::XML::Node * child = menustruct;
-            child != NULL;
+            child != nullptr;
             child = child->next()) {
         if (!strcmp(child->name(), name)) {
             return child;
         }
         Inkscape::XML::Node * firstchild = child->firstChild();
-        if (firstchild != NULL) {
+        if (firstchild != nullptr) {
             Inkscape::XML::Node *found = find_menu (firstchild, name);
             if (found)
                 return found;
         }
     }
-    return NULL;
+    return nullptr;
 }
 
 
@@ -380,7 +380,7 @@ Effect::EffectVerb::perform( SPAction *action, void * data )
     Effect::EffectVerb * ev = reinterpret_cast<Effect::EffectVerb *>(data);
     Effect * effect = ev->_effect;
 
-    if (effect == NULL) return;
+    if (effect == nullptr) return;
 
     if (ev->_showPrefs) {
         effect->prefs(current_view);
diff --git a/src/extension/effect.h b/src/extension/effect.h
index a0f478978..5481d420a 100644
--- a/src/extension/effect.h
+++ b/src/extension/effect.h
@@ -70,10 +70,10 @@ class Effect : public Extension {
                     Verb(id, _(name), _(tip), image, _("Extensions")),
                     _effect(effect), 
                     _showPrefs(showPrefs),
-                    _elip_name(NULL) {
+                    _elip_name(nullptr) {
                 /* No clue why, but this is required */
                 this->set_default_sensitive(true);
-                if (_showPrefs && effect != NULL && effect->param_visible_count() != 0) {
+                if (_showPrefs && effect != nullptr && effect->param_visible_count() != 0) {
                     _elip_name = g_strdup_printf("%s...", _(name));
                     set_name(_elip_name);
                 }
@@ -81,7 +81,7 @@ class Effect : public Extension {
             
             /** \brief  Destructor */
             ~EffectVerb() override {
-                if (_elip_name != NULL) {
+                if (_elip_name != nullptr) {
                     g_free(_elip_name);
                 }
             }
diff --git a/src/extension/execution-env.cpp b/src/extension/execution-env.cpp
index 0c979660d..0e0688f44 100644
--- a/src/extension/execution-env.cpp
+++ b/src/extension/execution-env.cpp
@@ -46,8 +46,8 @@ namespace Extension {
 */
 ExecutionEnv::ExecutionEnv (Effect * effect, Inkscape::UI::View::View * doc, Implementation::ImplementationDocumentCache * docCache, bool show_working, bool show_errors) :
     _state(ExecutionEnv::INIT),
-    _visibleDialog(NULL),
-    _mainloop(NULL),
+    _visibleDialog(nullptr),
+    _mainloop(nullptr),
     _doc(doc),
     _docCache(docCache),
     _effect(effect),
@@ -64,10 +64,10 @@ ExecutionEnv::ExecutionEnv (Effect * effect, Inkscape::UI::View::View * doc, Imp
     Destroys the dialog if created and the document cache.
 */
 ExecutionEnv::~ExecutionEnv (void) {
-    if (_visibleDialog != NULL) {
+    if (_visibleDialog != nullptr) {
         _visibleDialog->hide();
         delete _visibleDialog;
-        _visibleDialog = NULL;
+        _visibleDialog = nullptr;
     }
     killDocCache();
     return;
@@ -80,7 +80,7 @@ ExecutionEnv::~ExecutionEnv (void) {
 */
 void
 ExecutionEnv::genDocCache (void) {
-    if (_docCache == NULL) {
+    if (_docCache == nullptr) {
         // printf("Gen Doc Cache\n");
         _docCache = _effect->get_imp()->newDocCache(_effect, _doc);
     }
@@ -93,10 +93,10 @@ ExecutionEnv::genDocCache (void) {
 */
 void
 ExecutionEnv::killDocCache (void) {
-    if (_docCache != NULL) {
+    if (_docCache != nullptr) {
         // printf("Killed Doc Cache\n");
         delete _docCache;
-        _docCache = NULL;
+        _docCache = nullptr;
     }
     return;
 }
@@ -108,10 +108,10 @@ ExecutionEnv::killDocCache (void) {
 */
 void
 ExecutionEnv::createWorkingDialog (void) {
-    if (_visibleDialog != NULL) {
+    if (_visibleDialog != nullptr) {
         _visibleDialog->hide();
         delete _visibleDialog;
-        _visibleDialog = NULL;
+        _visibleDialog = nullptr;
     }
 
     SPDesktop *desktop = (SPDesktop *)_doc;
diff --git a/src/extension/execution-env.h b/src/extension/execution-env.h
index f75e97efa..5ae7beb42 100644
--- a/src/extension/execution-env.h
+++ b/src/extension/execution-env.h
@@ -78,7 +78,7 @@ public:
     */
     ExecutionEnv (Effect * effect,
                   Inkscape::UI::View::View * doc,
-                  Implementation::ImplementationDocumentCache * docCache = NULL,
+                  Implementation::ImplementationDocumentCache * docCache = nullptr,
                   bool show_working = true,
                   bool show_errors = true);
     virtual ~ExecutionEnv (void);
diff --git a/src/extension/extension.cpp b/src/extension/extension.cpp
index f07d334af..55b5f68fc 100644
--- a/src/extension/extension.cpp
+++ b/src/extension/extension.cpp
@@ -54,29 +54,29 @@ std::ofstream Extension::error_file;
     a name and an ID the module will be left in an errored state.
 */
 Extension::Extension (Inkscape::XML::Node * in_repr, Implementation::Implementation * in_imp)
-    : _help(NULL)
+    : _help(nullptr)
     , silent(false)
     , _gui(true)
-    , execution_env(NULL)
+    , execution_env(nullptr)
 {
     repr = in_repr;
     Inkscape::GC::anchor(in_repr);
 
-    id = NULL;
-    name = NULL;
+    id = nullptr;
+    name = nullptr;
     _state = STATE_UNLOADED;
 
-    if (in_imp == NULL) {
+    if (in_imp == nullptr) {
         imp = new Implementation::Implementation();
     } else {
         imp = in_imp;
     }
 
     // printf("Extension Constructor: ");
-    if (repr != NULL) {
+    if (repr != nullptr) {
         Inkscape::XML::Node *child_repr = repr->firstChild();
         /* TODO: Handle what happens if we don't have these two */
-        while (child_repr != NULL) {
+        while (child_repr != nullptr) {
             char const * chname = child_repr->name();
 			if (!strncmp(chname, INKSCAPE_EXTENSION_NS_NC, strlen(INKSCAPE_EXTENSION_NS_NC))) {
 				chname += strlen(INKSCAPE_EXTENSION_NS);
@@ -96,14 +96,14 @@ Extension::Extension (Inkscape::XML::Node * in_repr, Implementation::Implementat
             if (!strcmp(chname, "param") || !strcmp(chname, "_param")) {
                 Parameter * param;
                 param = Parameter::make(child_repr, this);
-                if (param != NULL)
+                if (param != nullptr)
                     parameters.push_back(param);
             } /* param || _param */
             if (!strcmp(chname, "dependency")) {
                 _deps.push_back(new Dependency(child_repr));
             } /* dependency */
             if (!strcmp(chname, "script")) {
-                for (Inkscape::XML::Node *child = child_repr->firstChild(); child != NULL ; child = child->next()) {
+                for (Inkscape::XML::Node *child = child_repr->firstChild(); child != nullptr ; child = child->next()) {
                     if (child->type() == Inkscape::XML::ELEMENT_NODE) {
                         _deps.push_back(new Dependency(child));
                         break;
@@ -119,7 +119,7 @@ Extension::Extension (Inkscape::XML::Node * in_repr, Implementation::Implementat
         db.register_ext (this);
     }
     // printf("%s\n", name);
-    timer = NULL;
+    timer = nullptr;
 
     return;
 }
@@ -142,7 +142,7 @@ Extension::~Extension (void)
     g_free(id);
     g_free(name);
     delete timer;
-    timer = NULL;
+    timer = nullptr;
     /** \todo Need to do parameters here */
 
     // delete parameters:
@@ -180,7 +180,7 @@ Extension::set_state (state_t in_state)
                 if (imp->load(this))
                     _state = STATE_LOADED;
 
-                if (timer != NULL) {
+                if (timer != nullptr) {
                     delete timer;
                 }
                 timer = new ExpirationTimer(this);
@@ -191,17 +191,17 @@ Extension::set_state (state_t in_state)
                 imp->unload(this);
                 _state = STATE_UNLOADED;
 
-                if (timer != NULL) {
+                if (timer != nullptr) {
                     delete timer;
-                    timer = NULL;
+                    timer = nullptr;
                 }
                 break;
             case STATE_DEACTIVATED:
                 _state = STATE_DEACTIVATED;
 
-                if (timer != NULL) {
+                if (timer != nullptr) {
                     delete timer;
-                    timer = NULL;
+                    timer = nullptr;
                 }
                 break;
             default:
@@ -270,19 +270,19 @@ Extension::check (void)
         retval = false;
     }
 #endif
-    if (id == NULL) {
+    if (id == nullptr) {
         printFailure(Glib::ustring(_("an ID was not defined for it.")) + inx_failure);
         retval = false;
     }
-    if (name == NULL) {
+    if (name == nullptr) {
         printFailure(Glib::ustring(_("there was no name defined for it.")) + inx_failure);
         retval = false;
     }
-    if (repr == NULL) {
+    if (repr == nullptr) {
         printFailure(Glib::ustring(_("the XML description of it got lost.")) + inx_failure);
         retval = false;
     }
-    if (imp == NULL) {
+    if (imp == nullptr) {
         printFailure(Glib::ustring(_("no implementation was defined for the extension.")) + inx_failure);
         retval = false;
     }
@@ -396,7 +396,7 @@ Extension::deactivated (void)
 
 Parameter *Extension::get_param(gchar const *name)
 {
-    if (name == NULL) {
+    if (name == nullptr) {
         throw Extension::param_not_exist();
     }
     if (this->parameters.empty()) {
@@ -653,7 +653,7 @@ void
 Extension::error_file_open (void)
 {
     gchar * ext_error_file = Inkscape::IO::Resource::log_path(EXTENSION_ERROR_LOG_FILENAME);
-    gchar * filename = g_filename_from_utf8( ext_error_file, -1, NULL, NULL, NULL );
+    gchar * filename = g_filename_from_utf8( ext_error_file, -1, nullptr, nullptr, nullptr );
     error_file.open(filename);
     if (!error_file.is_open()) {
         g_warning(_("Could not create extension error log file '%s'"),
@@ -717,7 +717,7 @@ public:
 Gtk::Widget *
 Extension::autogui (SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
-    if (!_gui || param_visible_count() == 0) return NULL;
+    if (!_gui || param_visible_count() == 0) return nullptr;
 
     AutoGUI * agui = Gtk::manage(new AutoGUI());
     agui->set_border_width(Parameter::GUI_BOX_MARGIN);
@@ -798,7 +798,7 @@ Extension::get_help_widget(void)
 {
     Gtk::VBox * retval = Gtk::manage(new Gtk::VBox());
 
-    if (_help == NULL) {
+    if (_help == nullptr) {
         Gtk::Label * content = Gtk::manage(new Gtk::Label(_("Currently there is no help available for this Extension.  Please look on the Inkscape website or ask on the mailing lists if you have questions regarding this extension.")));
         retval->pack_start(*content, true, true, 5);
         content->set_line_wrap(true);
diff --git a/src/extension/extension.h b/src/extension/extension.h
index d66399d59..e927e1431 100644
--- a/src/extension/extension.h
+++ b/src/extension/extension.h
@@ -204,16 +204,16 @@ private:
 
 public:
     bool             get_param_bool   (const gchar * name,
-                                       const SPDocument *   doc = NULL,
-                                       const Inkscape::XML::Node * node = NULL);
+                                       const SPDocument *   doc = nullptr,
+                                       const Inkscape::XML::Node * node = nullptr);
 
     int              get_param_int    (const gchar * name,
-                                       const SPDocument *   doc = NULL,
-                                       const Inkscape::XML::Node * node = NULL);
+                                       const SPDocument *   doc = nullptr,
+                                       const Inkscape::XML::Node * node = nullptr);
 
     float            get_param_float  (const gchar * name,
-                                       const SPDocument *   doc = NULL,
-                                       const Inkscape::XML::Node * node = NULL);
+                                       const SPDocument *   doc = nullptr,
+                                       const Inkscape::XML::Node * node = nullptr);
 
     /**
      * Gets a parameter identified by name with the string placed in value.
@@ -226,60 +226,60 @@ public:
      * @return A constant pointer to the string held by the parameters.
      */
     gchar const *get_param_string(gchar const *name,
-                                  SPDocument const *doc = NULL,
-                                  Inkscape::XML::Node const *node = NULL) const;
+                                  SPDocument const *doc = nullptr,
+                                  Inkscape::XML::Node const *node = nullptr) const;
 
     guint32          get_param_color  (const gchar * name,
-                                       const SPDocument *   doc = NULL,
-                                       const Inkscape::XML::Node * node = NULL) const;
+                                       const SPDocument *   doc = nullptr,
+                                       const Inkscape::XML::Node * node = nullptr) const;
 
     const gchar *    get_param_enum   (const gchar * name,
-                                       const SPDocument *   doc = NULL,
-                                       const Inkscape::XML::Node * node = NULL) const;
+                                       const SPDocument *   doc = nullptr,
+                                       const Inkscape::XML::Node * node = nullptr) const;
 
     gchar const *get_param_optiongroup( gchar const * name,
-                                        SPDocument const *   doc = 0,
-                                        Inkscape::XML::Node const * node = 0) const;
+                                        SPDocument const *   doc = nullptr,
+                                        Inkscape::XML::Node const * node = nullptr) const;
 
     bool             get_param_enum_contains(gchar const * name,
                                              gchar const * value,
-                                             SPDocument  * doc = 0x0,
-                                             Inkscape::XML::Node * node = 0x0) const;
+                                             SPDocument  * doc = nullptr,
+                                             Inkscape::XML::Node * node = nullptr) const;
 
     bool             set_param_bool   (const gchar * name,
                                        bool          value,
-                                       SPDocument *   doc = NULL,
-                                       Inkscape::XML::Node *       node = NULL);
+                                       SPDocument *   doc = nullptr,
+                                       Inkscape::XML::Node *       node = nullptr);
 
     int              set_param_int    (const gchar * name,
                                        int           value,
-                                       SPDocument *   doc = NULL,
-                                       Inkscape::XML::Node *       node = NULL);
+                                       SPDocument *   doc = nullptr,
+                                       Inkscape::XML::Node *       node = nullptr);
 
     float            set_param_float  (const gchar * name,
                                        float         value,
-                                       SPDocument *   doc = NULL,
-                                       Inkscape::XML::Node *       node = NULL);
+                                       SPDocument *   doc = nullptr,
+                                       Inkscape::XML::Node *       node = nullptr);
 
     const gchar *    set_param_string (const gchar * name,
                                        const gchar * value,
-                                       SPDocument *   doc = NULL,
-                                       Inkscape::XML::Node *       node = NULL);
+                                       SPDocument *   doc = nullptr,
+                                       Inkscape::XML::Node *       node = nullptr);
 
     gchar const * set_param_optiongroup(gchar const * name,
                                         gchar const * value,
-                                        SPDocument * doc = 0,
-                                        Inkscape::XML::Node * node = 0);
+                                        SPDocument * doc = nullptr,
+                                        Inkscape::XML::Node * node = nullptr);
 
     gchar const *    set_param_enum   (gchar const * name,
                                        gchar const * value,
-                                       SPDocument * doc = 0x0,
-                                       Inkscape::XML::Node * node = 0x0);
+                                       SPDocument * doc = nullptr,
+                                       Inkscape::XML::Node * node = nullptr);
 
     guint32          set_param_color  (const gchar * name,
                                        guint32 color,
-                                       SPDocument *   doc = NULL,
-                                       Inkscape::XML::Node *       node = NULL);
+                                       SPDocument *   doc = nullptr,
+                                       Inkscape::XML::Node *       node = nullptr);
 
     /* Error file handling */
 public:
@@ -287,7 +287,7 @@ public:
     static void      error_file_close (void);
 
 public:
-    Gtk::Widget *    autogui (SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal = NULL);
+    Gtk::Widget *    autogui (SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal = nullptr);
     void paramListString (std::list <std::string> & retlist);
     void set_gui(bool s) { _gui = s; }
 
diff --git a/src/extension/implementation/implementation.cpp b/src/extension/implementation/implementation.cpp
index 6e6100d2b..2a6a76ff4 100644
--- a/src/extension/implementation/implementation.cpp
+++ b/src/extension/implementation/implementation.cpp
@@ -29,24 +29,24 @@ namespace Implementation {
 
 Gtk::Widget *
 Implementation::prefs_input(Inkscape::Extension::Input *module, gchar const */*filename*/) {
-    return module->autogui(NULL, NULL);
+    return module->autogui(nullptr, nullptr);
 }
 
 Gtk::Widget *
 Implementation::prefs_output(Inkscape::Extension::Output *module) {
-    return module->autogui(NULL, NULL);
+    return module->autogui(nullptr, nullptr);
 }
 
 Gtk::Widget *Implementation::prefs_effect(Inkscape::Extension::Effect *module, Inkscape::UI::View::View * view, sigc::signal<void> * changeSignal, ImplementationDocumentCache * /*docCache*/)
 {
     if (module->param_visible_count() == 0) {
-        return NULL;
+        return nullptr;
     }
 
     SPDocument * current_document = view->doc();
 
     auto selected = ((SPDesktop *) view)->getSelection()->items();
-    Inkscape::XML::Node const* first_select = NULL;
+    Inkscape::XML::Node const* first_select = nullptr;
     if (!selected.empty()) {
         const SPItem * item = selected.front();
         first_select = item->getRepr();
diff --git a/src/extension/implementation/implementation.h b/src/extension/implementation/implementation.h
index cf41e5517..52542064b 100644
--- a/src/extension/implementation/implementation.h
+++ b/src/extension/implementation/implementation.h
@@ -88,7 +88,7 @@ public:
      * @return A new document cache that is valid as long as the document
      *         is not changed.
      */
-    virtual ImplementationDocumentCache * newDocCache (Inkscape::Extension::Extension * /*ext*/, Inkscape::UI::View::View * /*doc*/) { return NULL; }
+    virtual ImplementationDocumentCache * newDocCache (Inkscape::Extension::Extension * /*ext*/, Inkscape::UI::View::View * /*doc*/) { return nullptr; }
 
     /** Verify any dependencies. */
     virtual bool check(Inkscape::Extension::Extension * /*module*/) { return true; }
@@ -103,7 +103,7 @@ public:
                              gchar const *filename);
 
     virtual SPDocument *open(Inkscape::Extension::Input * /*module*/,
-                             gchar const * /*filename*/) { return NULL; }
+                             gchar const * /*filename*/) { return nullptr; }
 
     // ----- Output functions -----
     /** Find out information about the file. */
diff --git a/src/extension/implementation/script.cpp b/src/extension/implementation/script.cpp
index 6b629934f..a8490fe73 100644
--- a/src/extension/implementation/script.cpp
+++ b/src/extension/implementation/script.cpp
@@ -93,7 +93,7 @@ Script::interpreter_t const Script::interpreterTab[] = {
 #endif
         {"ruby",   "ruby-interpreter",   "ruby"   },
         {"shell",  "shell-interpreter",  "sh"     },
-        { NULL,    NULL,                  NULL    }
+        { nullptr,    nullptr,                  nullptr    }
 };
 
 
@@ -105,7 +105,7 @@ Script::interpreter_t const Script::interpreterTab[] = {
 */
 std::string Script::resolveInterpreterExecutable(const Glib::ustring &interpNameArg)
 {
-    interpreter_t const *interp = 0;
+    interpreter_t const *interp = nullptr;
     bool foundInterp = false;
     for (interp =  interpreterTab ; interp->identity ; interp++ ){
         if (interpNameArg == interp->identity) {
@@ -156,7 +156,7 @@ std::string Script::resolveInterpreterExecutable(const Glib::ustring &interpName
 Script::Script()
     : Implementation()
     , _canceled(false)
-    , parent_window(NULL)
+    , parent_window(nullptr)
 {
 }
 
@@ -294,12 +294,12 @@ bool Script::load(Inkscape::Extension::Extension *module)
 
     /* This should probably check to find the executable... */
     Inkscape::XML::Node *child_repr = module->get_repr()->firstChild();
-    while (child_repr != NULL) {
+    while (child_repr != nullptr) {
         if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "script")) {
-            for (child_repr = child_repr->firstChild(); child_repr != NULL; child_repr = child_repr->next()) {
+            for (child_repr = child_repr->firstChild(); child_repr != nullptr; child_repr = child_repr->next()) {
                 if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "command")) {
                     const gchar *interpretstr = child_repr->attribute("interpreter");
-                    if (interpretstr != NULL) {
+                    if (interpretstr != nullptr) {
                         std::string interpString = resolveInterpreterExecutable(interpretstr);
                         if (interpString.empty()) {
                             continue; // can't have a script extension with empty interpreter
@@ -353,11 +353,11 @@ bool Script::check(Inkscape::Extension::Extension *module)
 {
     int script_count = 0;
     Inkscape::XML::Node *child_repr = module->get_repr()->firstChild();
-    while (child_repr != NULL) {
+    while (child_repr != nullptr) {
         if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "script")) {
             script_count++;
             child_repr = child_repr->firstChild();
-            while (child_repr != NULL) {
+            while (child_repr != nullptr) {
                 if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "check")) {
                     std::string command_text = solve_reldir(child_repr);
                     if (!command_text.empty()) {
@@ -373,7 +373,7 @@ bool Script::check(Inkscape::Extension::Extension *module)
 
                 if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "helper_extension")) {
                     gchar const *helper = child_repr->firstChild()->content();
-                    if (Inkscape::Extension::db.get(helper) == NULL) {
+                    if (Inkscape::Extension::db.get(helper) == nullptr) {
                         return false;
                     }
                 }
@@ -449,7 +449,7 @@ ImplementationDocumentCache *Script::newDocCache( Inkscape::Extension::Extension
 Gtk::Widget *Script::prefs_input(Inkscape::Extension::Input *module,
                     const gchar */*filename*/)
 {
-    return module->autogui(NULL, NULL);
+    return module->autogui(nullptr, nullptr);
 }
 
 
@@ -463,7 +463,7 @@ Gtk::Widget *Script::prefs_input(Inkscape::Extension::Input *module,
 */
 Gtk::Widget *Script::prefs_output(Inkscape::Extension::Output *module)
 {
-    return module->autogui(NULL, NULL);
+    return module->autogui(nullptr, nullptr);
 }
 
 /**
@@ -499,7 +499,7 @@ SPDocument *Script::open(Inkscape::Extension::Input *module,
         tempfd_out = Glib::file_open_tmp(tempfilename_out, "ink_ext_XXXXXX.svg");
     } catch (...) {
         /// \todo Popup dialog here
-        return NULL;
+        return nullptr;
     }
 
     std::string lfilename = Glib::filename_from_utf8(filenameArg);
@@ -508,7 +508,7 @@ SPDocument *Script::open(Inkscape::Extension::Input *module,
     int data_read = execute(command, params, lfilename, fileout);
     fileout.toFile(tempfilename_out);
 
-    SPDocument * mydoc = NULL;
+    SPDocument * mydoc = nullptr;
     if (data_read > 10) {
         if (helper_extension.size()==0) {
             mydoc = Inkscape::Extension::open(
@@ -521,8 +521,8 @@ SPDocument *Script::open(Inkscape::Extension::Input *module,
         }
     } // data_read
 
-    if (mydoc != NULL) {
-        mydoc->setBase(0);
+    if (mydoc != nullptr) {
+        mydoc->setBase(nullptr);
         mydoc->changeUriAndHrefs(filenameArg);
     }
 
@@ -646,15 +646,15 @@ void Script::effect(Inkscape::Extension::Effect *module,
                Inkscape::UI::View::View *doc,
                ImplementationDocumentCache * docCache)
 {
-    if (docCache == NULL) {
+    if (docCache == nullptr) {
         docCache = newDocCache(module, doc);
     }
     ScriptDocCache * dc = dynamic_cast<ScriptDocCache *>(docCache);
-    if (dc == NULL) {
+    if (dc == nullptr) {
         printf("TOO BAD TO LIVE!!!");
         exit(1);
     }
-    if (doc == NULL)
+    if (doc == nullptr)
     {
         g_warning("Script::effect: View not defined");
         return;
@@ -709,7 +709,7 @@ void Script::effect(Inkscape::Extension::Effect *module,
 
     pump_events();
 
-    SPDocument * mydoc = NULL;
+    SPDocument * mydoc = nullptr;
     if (data_read > 10) {
         try {
             mydoc = Inkscape::Extension::open(
@@ -734,23 +734,23 @@ void Script::effect(Inkscape::Extension::Effect *module,
 
     if (mydoc) {
         SPDocument* vd=doc->doc();
-        if (vd != NULL)
+        if (vd != nullptr)
         {
             vd->emitReconstructionStart();
             copy_doc(vd->rroot, mydoc->rroot);
             vd->emitReconstructionFinish();
 
             // Getting the named view from the document generated by the extension
-            SPNamedView *nv = sp_document_namedview(mydoc, NULL);
+            SPNamedView *nv = sp_document_namedview(mydoc, nullptr);
             
             //Check if it has a default layer set up
-            SPObject *layer = NULL;
-            if ( nv != NULL)
+            SPObject *layer = nullptr;
+            if ( nv != nullptr)
             {
                 if( nv->default_layer_id != 0 ) {
                     SPDocument *document = desktop->doc();
                     //If so, get that layer
-                    if (document != NULL)
+                    if (document != nullptr)
                     {
                         layer = document->getObjectById(g_quark_to_string(nv->default_layer_id));
                     }
@@ -800,7 +800,7 @@ void Script::effect(Inkscape::Extension::Effect *module,
 */
 void Script::copy_doc (Inkscape::XML::Node * oldroot, Inkscape::XML::Node * newroot)
 {
-    if ((oldroot == NULL) ||(newroot == NULL))
+    if ((oldroot == nullptr) ||(newroot == nullptr))
     {
         g_warning("Error on copy_doc: NULL pointer input.");
         return;
@@ -822,7 +822,7 @@ void Script::copy_doc (Inkscape::XML::Node * oldroot, Inkscape::XML::Node * newr
 
     // Delete the attributes of the old root node.
     for (std::vector<gchar const *>::const_iterator it = attribs.begin(); it != attribs.end(); ++it) {
-        oldroot->setAttribute(*it, NULL);
+        oldroot->setAttribute(*it, nullptr);
     }
 
     // Set the new attributes.
@@ -840,11 +840,11 @@ void Script::copy_doc (Inkscape::XML::Node * oldroot, Inkscape::XML::Node * newr
 
     // Make list
     for (Inkscape::XML::Node * child = oldroot->firstChild();
-            child != NULL;
+            child != nullptr;
             child = child->next()) {
         if (!strcmp("sodipodi:namedview", child->name())) {
             for (Inkscape::XML::Node * oldroot_namedview_child = child->firstChild();
-                    oldroot_namedview_child != NULL;
+                    oldroot_namedview_child != nullptr;
                     oldroot_namedview_child = oldroot_namedview_child->next()) {
                 delete_list.push_back(oldroot_namedview_child);
             }
@@ -1014,7 +1014,7 @@ int Script::execute (const std::list<std::string> &in_command,
                                      static_cast<Glib::SpawnFlags>(0), // no flags
                                      sigc::slot<void>(),
                                      &_pid,          // Pid
-                                     NULL,           // STDIN
+                                     nullptr,           // STDIN
                                      &stdout_pipe,   // STDOUT
                                      &stderr_pipe);  // STDERR
     } catch (Glib::Error &e) {
diff --git a/src/extension/implementation/xslt.cpp b/src/extension/implementation/xslt.cpp
index d11283db7..9e4a45483 100644
--- a/src/extension/implementation/xslt.cpp
+++ b/src/extension/implementation/xslt.cpp
@@ -48,8 +48,8 @@ namespace Implementation {
 XSLT::XSLT(void) :
     Implementation(),
     _filename(""),
-    _parsedDoc(NULL),
-    _stylesheet(NULL)
+    _parsedDoc(nullptr),
+    _stylesheet(nullptr)
 {
 }
 
@@ -87,10 +87,10 @@ bool XSLT::load(Inkscape::Extension::Extension *module)
     if (module->loaded()) { return true; }
 
     Inkscape::XML::Node *child_repr = module->get_repr()->firstChild();
-    while (child_repr != NULL) {
+    while (child_repr != nullptr) {
         if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "xslt")) {
             child_repr = child_repr->firstChild();
-            while (child_repr != NULL) {
+            while (child_repr != nullptr) {
                 if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "file")) {
                     _filename = solve_reldir(child_repr);
                 }
@@ -103,7 +103,7 @@ bool XSLT::load(Inkscape::Extension::Extension *module)
     }
 
     _parsedDoc = xmlParseFile(_filename.c_str());
-    if (_parsedDoc == NULL) { return false; }
+    if (_parsedDoc == nullptr) { return false; }
 
     _stylesheet = xsltParseStylesheetDoc(_parsedDoc);
 
@@ -122,10 +122,10 @@ SPDocument * XSLT::open(Inkscape::Extension::Input */*module*/,
                         gchar const *filename)
 {
     xmlDocPtr filein = xmlParseFile(filename);
-    if (filein == NULL) { return NULL; }
+    if (filein == nullptr) { return nullptr; }
 
     const char * params[1];
-    params[0] = NULL;
+    params[0] = nullptr;
 
     xmlDocPtr result = xsltApplyStylesheet(_stylesheet, filein, params);
     xmlFreeDoc(filein);
@@ -133,17 +133,17 @@ SPDocument * XSLT::open(Inkscape::Extension::Input */*module*/,
     Inkscape::XML::Document * rdoc = sp_repr_do_read( result, SP_SVG_NS_URI);
     xmlFreeDoc(result);
 
-    if (rdoc == NULL) {
-        return NULL;
+    if (rdoc == nullptr) {
+        return nullptr;
     }
 
     if (strcmp(rdoc->root()->name(), "svg:svg") != 0) {
-        return NULL;
+        return nullptr;
     }
 
-    gchar * base = NULL;
-    gchar * name = NULL;
-    gchar * s = NULL, * p = NULL;
+    gchar * base = nullptr;
+    gchar * name = nullptr;
+    gchar * s = nullptr, * p = nullptr;
     s = g_strdup(filename);
     p = strrchr(s, '/');
     if (p) {
@@ -151,12 +151,12 @@ SPDocument * XSLT::open(Inkscape::Extension::Input */*module*/,
         p[1] = '\0';
         base = g_strdup(s);
     } else {
-        base = NULL;
+        base = nullptr;
         name = g_strdup(filename);
     }
     g_free(s);
 
-    SPDocument * doc = SPDocument::createDoc(rdoc, filename, base, name, true, NULL);
+    SPDocument * doc = SPDocument::createDoc(rdoc, filename, base, name, true, nullptr);
 
     g_free(base); g_free(name);
 
@@ -167,8 +167,8 @@ void XSLT::save(Inkscape::Extension::Output *module, SPDocument *doc, gchar cons
 {
     /* TODO: Should we assume filename to be in utf8 or to be a raw filename?
      * See JavaFXOutput::save for discussion. */
-    g_return_if_fail(doc != NULL);
-    g_return_if_fail(filename != NULL);
+    g_return_if_fail(doc != nullptr);
+    g_return_if_fail(filename != nullptr);
 
     Inkscape::XML::Node *repr = doc->getReprRoot();
 
@@ -188,7 +188,7 @@ void XSLT::save(Inkscape::Extension::Output *module, SPDocument *doc, gchar cons
 
     xmlDocPtr svgdoc = xmlParseFile(tempfilename_out.c_str());
     close(tempfd_out);
-    if (svgdoc == NULL) {
+    if (svgdoc == nullptr) {
         return;
     }
 
@@ -207,7 +207,7 @@ void XSLT::save(Inkscape::Extension::Output *module, SPDocument *doc, gchar cons
         xslt_params[count++] = g_strdup_printf("%s", parameter.str().c_str());
         xslt_params[count++] = g_strdup_printf("'%s'", value.str().c_str());
     }
-    xslt_params[count] = NULL;
+    xslt_params[count] = nullptr;
 
     xmlDocPtr newdoc = xsltApplyStylesheet(_stylesheet, svgdoc, xslt_params);
     //xmlSaveFile(filename, newdoc);
diff --git a/src/extension/init.cpp b/src/extension/init.cpp
index 17c07ae1d..d0487d473 100644
--- a/src/extension/init.cpp
+++ b/src/extension/init.cpp
@@ -260,7 +260,7 @@ check_extensions_internal(Extension *in_plug, gpointer in_data)
 {
     int *count = (int *)in_data;
 
-    if (in_plug == NULL) return;
+    if (in_plug == nullptr) return;
     if (!in_plug->deactivated() && !in_plug->check()) {
          in_plug->deactivate();
         (*count)++;
diff --git a/src/extension/input.cpp b/src/extension/input.cpp
index 862d4a4d3..3fb330998 100644
--- a/src/extension/input.cpp
+++ b/src/extension/input.cpp
@@ -38,21 +38,21 @@ namespace Extension {
 */
 Input::Input (Inkscape::XML::Node * in_repr, Implementation::Implementation * in_imp) : Extension(in_repr, in_imp)
 {
-    mimetype = NULL;
-    extension = NULL;
-    filetypename = NULL;
-    filetypetooltip = NULL;
-    output_extension = NULL;
+    mimetype = nullptr;
+    extension = nullptr;
+    filetypename = nullptr;
+    filetypetooltip = nullptr;
+    output_extension = nullptr;
 
-    if (repr != NULL) {
+    if (repr != nullptr) {
         Inkscape::XML::Node * child_repr;
 
         child_repr = repr->firstChild();
 
-        while (child_repr != NULL) {
+        while (child_repr != nullptr) {
             if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "input")) {
                 child_repr = child_repr->firstChild();
-                while (child_repr != NULL) {
+                while (child_repr != nullptr) {
                     char const * chname = child_repr->name();
 					if (!strncmp(chname, INKSCAPE_EXTENSION_NS_NC, strlen(INKSCAPE_EXTENSION_NS_NC))) {
 						chname += strlen(INKSCAPE_EXTENSION_NS);
@@ -119,9 +119,9 @@ Input::~Input (void)
 bool
 Input::check (void)
 {
-    if (extension == NULL)
+    if (extension == nullptr)
         return FALSE;
-    if (mimetype == NULL)
+    if (mimetype == nullptr)
         return FALSE;
 
     return Extension::check();
@@ -144,7 +144,7 @@ Input::open (const gchar *uri)
         set_state(Extension::STATE_LOADED);
     }
     if (!loaded()) {
-        return NULL;
+        return nullptr;
     }
     timer->touch();
 
@@ -184,7 +184,7 @@ Input::get_extension(void)
 gchar *
 Input::get_filetypename(void)
 {
-    if (filetypename != NULL)
+    if (filetypename != nullptr)
         return filetypename;
     else
         return get_name();
@@ -218,7 +218,7 @@ Input::prefs (const gchar *uri)
 
     Gtk::Widget * controls;
     controls = imp->prefs_input(this, uri);
-    if (controls == NULL) {
+    if (controls == nullptr) {
         // std::cout << "No preferences for Input" << std::endl;
         return true;
     }
diff --git a/src/extension/internal/bluredge.cpp b/src/extension/internal/bluredge.cpp
index f04007d00..808023c7c 100644
--- a/src/extension/internal/bluredge.cpp
+++ b/src/extension/internal/bluredge.cpp
@@ -96,10 +96,10 @@ BlurEdge::effect (Inkscape::Extension::Effect *module, Inkscape::UI::View::View
                 /* Doing an inset here folks */
                 offset *= -1.0;
                 prefs->setDoubleUnit("/options/defaultoffsetwidth/value", offset, "px");
-                sp_action_perform(Inkscape::Verb::get(SP_VERB_SELECTION_INSET)->get_action(Inkscape::ActionContext(desktop)), NULL);
+                sp_action_perform(Inkscape::Verb::get(SP_VERB_SELECTION_INSET)->get_action(Inkscape::ActionContext(desktop)), nullptr);
             } else if (offset > 0.0) {
                 prefs->setDoubleUnit("/options/defaultoffsetwidth/value", offset, "px");
-                sp_action_perform(Inkscape::Verb::get(SP_VERB_SELECTION_OFFSET)->get_action(Inkscape::ActionContext(desktop)), NULL);
+                sp_action_perform(Inkscape::Verb::get(SP_VERB_SELECTION_OFFSET)->get_action(Inkscape::ActionContext(desktop)), nullptr);
             }
 
             selection->clear();
@@ -119,7 +119,7 @@ BlurEdge::effect (Inkscape::Extension::Effect *module, Inkscape::UI::View::View
 Gtk::Widget *
 BlurEdge::prefs_effect(Inkscape::Extension::Effect * module, Inkscape::UI::View::View * /*view*/, sigc::signal<void> * changeSignal, Inkscape::Extension::Implementation::ImplementationDocumentCache * /*docCache*/)
 {
-    return module->autogui(NULL, NULL, changeSignal);
+    return module->autogui(nullptr, nullptr, changeSignal);
 }
 
 #include "clear-n_.h"
diff --git a/src/extension/internal/cairo-png-out.cpp b/src/extension/internal/cairo-png-out.cpp
index 3cdbee8c1..c3261fdce 100644
--- a/src/extension/internal/cairo-png-out.cpp
+++ b/src/extension/internal/cairo-png-out.cpp
@@ -66,7 +66,7 @@ png_render_document_to_file(SPDocument *doc, gchar const *filename)
     ctx = renderer->createContext();
 
     /* Render document */
-    bool ret = renderer->setupDocument(ctx, doc, TRUE, 0., NULL);
+    bool ret = renderer->setupDocument(ctx, doc, TRUE, 0., nullptr);
     if (ret) {
         renderer->renderItem(ctx, base);
         ctx->saveAsPng(filename);
diff --git a/src/extension/internal/cairo-ps-out.cpp b/src/extension/internal/cairo-ps-out.cpp
index 287cf636f..9815088de 100644
--- a/src/extension/internal/cairo-ps-out.cpp
+++ b/src/extension/internal/cairo-ps-out.cpp
@@ -46,7 +46,7 @@ namespace Internal {
 
 bool CairoPsOutput::check (Inkscape::Extension::Extension * /*module*/)
 {
-    if (NULL == Inkscape::Extension::db.get(SP_MODULE_KEY_PRINT_CAIRO_PS)) {
+    if (nullptr == Inkscape::Extension::db.get(SP_MODULE_KEY_PRINT_CAIRO_PS)) {
         return FALSE;
     } else {
         return TRUE;
@@ -55,7 +55,7 @@ bool CairoPsOutput::check (Inkscape::Extension::Extension * /*module*/)
 
 bool CairoEpsOutput::check (Inkscape::Extension::Extension * /*module*/)
 {
-    if (NULL == Inkscape::Extension::db.get(SP_MODULE_KEY_PRINT_CAIRO_EPS)) {
+    if (nullptr == Inkscape::Extension::db.get(SP_MODULE_KEY_PRINT_CAIRO_EPS)) {
         return FALSE;
     } else {
         return TRUE;
@@ -68,7 +68,7 @@ ps_print_document_to_file(SPDocument *doc, gchar const *filename, unsigned int l
 {
     doc->ensureUpToDate();
 
-    SPItem *base = NULL;
+    SPItem *base = nullptr;
 
     bool pageBoundingBox = TRUE;
     if (exportId && strcmp(exportId, "")) {
@@ -134,13 +134,13 @@ CairoPsOutput::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar con
     unsigned int ret;
 
     ext = Inkscape::Extension::db.get(SP_MODULE_KEY_PRINT_CAIRO_PS);
-    if (ext == NULL)
+    if (ext == nullptr)
         return;
 
     int level = CAIRO_PS_LEVEL_2;
     try {
         const gchar *new_level = mod->get_param_enum("PSlevel");
-        if((new_level != NULL) && (g_ascii_strcasecmp("PS3", new_level) == 0)) {
+        if((new_level != nullptr) && (g_ascii_strcasecmp("PS3", new_level) == 0)) {
             level = CAIRO_PS_LEVEL_3;
         }
     } catch(...) {}
@@ -180,7 +180,7 @@ CairoPsOutput::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar con
         bleedmargin_px = mod->get_param_float("bleed");
     } catch(...) {}
 
-    const gchar *new_exportId = NULL;
+    const gchar *new_exportId = nullptr;
     try {
         new_exportId = mod->get_param_string("exportId");
     } catch(...) {}
@@ -223,13 +223,13 @@ CairoEpsOutput::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar co
     unsigned int ret;
 
     ext = Inkscape::Extension::db.get(SP_MODULE_KEY_PRINT_CAIRO_EPS);
-    if (ext == NULL)
+    if (ext == nullptr)
         return;
 
     int level = CAIRO_PS_LEVEL_2;
     try {
         const gchar *new_level = mod->get_param_enum("PSlevel");
-        if((new_level != NULL) && (g_ascii_strcasecmp("PS3", new_level) == 0)) {
+        if((new_level != nullptr) && (g_ascii_strcasecmp("PS3", new_level) == 0)) {
             level = CAIRO_PS_LEVEL_3;
         }
     } catch(...) {}
@@ -269,7 +269,7 @@ CairoEpsOutput::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar co
         bleedmargin_px = mod->get_param_float("bleed");
     } catch(...) {}
 
-    const gchar *new_exportId = NULL;
+    const gchar *new_exportId = nullptr;
     try {
         new_exportId = mod->get_param_string("exportId");
     } catch(...) {}
diff --git a/src/extension/internal/cairo-render-context.cpp b/src/extension/internal/cairo-render-context.cpp
index 23c20b968..36f73136b 100644
--- a/src/extension/internal/cairo-render-context.cpp
+++ b/src/extension/internal/cairo-render-context.cpp
@@ -119,15 +119,15 @@ CairoRenderContext::CairoRenderContext(CairoRenderer *parent) :
     _is_omittext(FALSE),
     _is_filtertobitmap(FALSE),
     _bitmapresolution(72),
-    _stream(NULL),
+    _stream(nullptr),
     _is_valid(FALSE),
     _vector_based_target(FALSE),
-    _cr(NULL), // Cairo context
-    _surface(NULL),
+    _cr(nullptr), // Cairo context
+    _surface(nullptr),
     _target(CAIRO_SURFACE_TYPE_IMAGE),
     _target_format(CAIRO_FORMAT_ARGB32),
-    _layout(NULL),
-    _state(NULL),
+    _layout(nullptr),
+    _state(nullptr),
     _renderer(parent),
     _render_mode(RENDER_MODE_NORMAL),
     _clip_mode(CLIP_MODE_MASK),
@@ -251,12 +251,12 @@ bool CairoRenderContext::setPdfTarget(gchar const *utf8_fn)
     _vector_based_target = TRUE;
 #endif
 
-    FILE *osf = NULL;
-    FILE *osp = NULL;
+    FILE *osf = nullptr;
+    FILE *osp = nullptr;
 
     gsize bytesRead = 0;
     gsize bytesWritten = 0;
-    GError *error = NULL;
+    GError *error = nullptr;
     gchar *local_fn = g_filename_from_utf8(utf8_fn,
                                            -1,  &bytesRead,  &bytesWritten, &error);
     gchar const *fn = local_fn;
@@ -266,7 +266,7 @@ bool CairoRenderContext::setPdfTarget(gchar const *utf8_fn)
     * the callers (sp_print_document_to_file, "ret = mod->begin(doc)") wrongly ignores the
     * return code.
     */
-    if (fn != NULL) {
+    if (fn != nullptr) {
         if (*fn == '|') {
             fn += 1;
             while (isspace(*fn)) fn += 1;
@@ -333,12 +333,12 @@ bool CairoRenderContext::setPsTarget(gchar const *utf8_fn)
     _vector_based_target = TRUE;
 #endif
 
-    FILE *osf = NULL;
-    FILE *osp = NULL;
+    FILE *osf = nullptr;
+    FILE *osp = nullptr;
 
     gsize bytesRead = 0;
     gsize bytesWritten = 0;
-    GError *error = NULL;
+    GError *error = nullptr;
     gchar *local_fn = g_filename_from_utf8(utf8_fn,
                                            -1,  &bytesRead,  &bytesWritten, &error);
     gchar const *fn = local_fn;
@@ -348,7 +348,7 @@ bool CairoRenderContext::setPsTarget(gchar const *utf8_fn)
     * the callers (sp_print_document_to_file, "ret = mod->begin(doc)") wrongly ignores the
     * return code.
     */
-    if (fn != NULL) {
+    if (fn != nullptr) {
         if (*fn == '|') {
             fn += 1;
             while (isspace(*fn)) fn += 1;
@@ -522,7 +522,7 @@ CairoRenderContext::getClipMode(void) const
 CairoRenderState* CairoRenderContext::_createState(void)
 {
     CairoRenderState *state = static_cast<CairoRenderState*>(g_try_malloc(sizeof(CairoRenderState)));
-    g_assert( state != NULL );
+    g_assert( state != nullptr );
 
     state->has_filtereffect = FALSE;
     state->merge_opacity = TRUE;
@@ -530,8 +530,8 @@ CairoRenderState* CairoRenderContext::_createState(void)
     state->need_layer = FALSE;
     state->has_overflow = FALSE;
     state->parent_has_userspace = FALSE;
-    state->clip_path = NULL;
-    state->mask = NULL;
+    state->clip_path = nullptr;
+    state->mask = nullptr;
 
     return state;
 }
@@ -579,14 +579,14 @@ CairoRenderContext::popLayer(void)
     SPMask *mask = _state->mask;
     if (clip_path || mask) {
 
-        CairoRenderContext *clip_ctx = 0;
-        cairo_surface_t *clip_mask = 0;
+        CairoRenderContext *clip_ctx = nullptr;
+        cairo_surface_t *clip_mask = nullptr;
 
         // Apply any clip path first
         if (clip_path) {
             TRACE(("  Applying clip\n"));
             if (_render_mode == RENDER_MODE_CLIP)
-                mask = NULL;    // disable mask when performing nested clipping
+                mask = nullptr;    // disable mask when performing nested clipping
 
             if (_vector_based_target) {
                 setClipMode(CLIP_MODE_PATH); // Vector
@@ -783,7 +783,7 @@ CairoRenderContext::setupSurface(double width, double height)
     if (_is_valid)
         return true;
 
-    if (_vector_based_target && _stream == NULL)
+    if (_vector_based_target && _stream == nullptr)
         return false;
 
     _width = width;
@@ -796,7 +796,7 @@ CairoRenderContext::setupSurface(double width, double height)
     os_bbox << "%%BoundingBox: 0 0 " << (int)ceil(width) << (int)ceil(height);  // apparently, the numbers should be integers. (see bug 380501)
     os_pagebbox << "%%PageBoundingBox: 0 0 " << (int)ceil(width) << (int)ceil(height);
 
-    cairo_surface_t *surface = NULL;
+    cairo_surface_t *surface = nullptr;
     cairo_matrix_t ctm;
     cairo_matrix_init_identity (&ctm);
     char buffer[25];
@@ -889,7 +889,7 @@ CairoRenderContext::setSurfaceTarget(cairo_surface_t *surface, bool is_vector, c
 bool
 CairoRenderContext::_finishSurfaceSetup(cairo_surface_t *surface, cairo_matrix_t *ctm)
 {
-    if(surface == NULL) {
+    if(surface == nullptr) {
         return false;
     }
     if(CAIRO_STATUS_SUCCESS != cairo_surface_status(surface)) {
@@ -932,13 +932,13 @@ CairoRenderContext::finish(bool finish_surface)
         g_critical("error while rendering output: %s", cairo_status_to_string(status));
 
     cairo_destroy(_cr);
-    _cr = NULL;
+    _cr = nullptr;
     
     if (finish_surface)
         cairo_surface_finish(_surface);
     status = cairo_surface_status(_surface);
     cairo_surface_destroy(_surface);
-    _surface = NULL;
+    _surface = nullptr;
 
     if (_layout)
         g_object_unref(_layout);
@@ -950,7 +950,7 @@ CairoRenderContext::finish(bool finish_surface)
         (void) fflush(_stream);
 
         fclose(_stream);
-        _stream = NULL;
+        _stream = nullptr;
     }
 
     if (status == CAIRO_STATUS_SUCCESS)
@@ -1133,7 +1133,7 @@ CairoRenderContext::_createPatternPainter(SPPaintServer const *const paintserver
     unsigned dkey = SPItem::display_key_new(1);
 
     // show items and render them
-    for (SPPattern *pat_i = pat; pat_i != NULL; pat_i = pat_i->ref ? pat_i->ref->getObject() : NULL) {
+    for (SPPattern *pat_i = pat; pat_i != nullptr; pat_i = pat_i->ref ? pat_i->ref->getObject() : nullptr) {
         if (pat_i && SP_IS_OBJECT(pat_i) && pattern_hasItemChildren(pat_i)) { // find the first one with item children
             for (auto& child: pat_i->children) {
                 if (SP_IS_ITEM(&child)) {
@@ -1162,7 +1162,7 @@ CairoRenderContext::_createPatternPainter(SPPaintServer const *const paintserver
     delete pattern_ctx;
 
     // hide all items
-    for (SPPattern *pat_i = pat; pat_i != NULL; pat_i = pat_i->ref ? pat_i->ref->getObject() : NULL) {
+    for (SPPattern *pat_i = pat; pat_i != nullptr; pat_i = pat_i->ref ? pat_i->ref->getObject() : nullptr) {
         if (pat_i && SP_IS_OBJECT(pat_i) && pattern_hasItemChildren(pat_i)) { // find the first one with item children
             for (auto& child: pat_i->children) {
                 if (SP_IS_ITEM(&child)) {
@@ -1257,7 +1257,7 @@ cairo_pattern_t*
 CairoRenderContext::_createPatternForPaintServer(SPPaintServer const *const paintserver,
                                                  Geom::OptRect const &pbox, float alpha)
 {
-    cairo_pattern_t *pattern = NULL;
+    cairo_pattern_t *pattern = nullptr;
     bool apply_bbox2user = FALSE;
 
     if (SP_IS_LINEARGRADIENT (paintserver)) {
@@ -1315,7 +1315,7 @@ CairoRenderContext::_createPatternForPaintServer(SPPaintServer const *const pain
     } else if ( dynamic_cast<SPHatch const *>(paintserver) ) {
         pattern = _createHatchPainter(paintserver, pbox);
     } else {
-        return NULL;
+        return nullptr;
     }
 
     if (pattern && SP_IS_GRADIENT(paintserver)) {
@@ -1441,7 +1441,7 @@ CairoRenderContext::_setStrokeStyle(SPStyle const *style, Geom::OptRect const &p
         cairo_set_dash(_cr, dashes, ndashes, style->stroke_dashoffset.value);
         free(dashes);
     } else {
-        cairo_set_dash(_cr, NULL, 0, 0.0);  // disable dashing
+        cairo_set_dash(_cr, nullptr, 0, 0.0);  // disable dashing
     }
 
     cairo_set_line_width(_cr, style->stroke_width.computed);
@@ -1567,7 +1567,7 @@ CairoRenderContext::renderPathVector(Geom::PathVector const & pathv, SPStyle con
         return true;
 
     bool need_layer = ( !_state->merge_opacity && !_state->need_layer &&
-                        ( _state->opacity != 1.0 || _state->clip_path != NULL || _state->mask != NULL ) );
+                        ( _state->opacity != 1.0 || _state->clip_path != nullptr || _state->mask != nullptr ) );
 
     if (!need_layer)
         cairo_save(_cr);
@@ -1689,7 +1689,7 @@ unsigned int CairoRenderContext::_showGlyphs(cairo_t *cr, PangoFont * /*font*/,
     unsigned int num_glyphs = glyphtext.size();
     if (num_glyphs > GLYPH_ARRAY_SIZE) {
         glyphs = (cairo_glyph_t*)g_try_malloc(sizeof(cairo_glyph_t) * num_glyphs);
-        if(glyphs == NULL) {
+        if(glyphs == nullptr) {
             g_warning("CairorenderContext::_showGlyphs: can not allocate memory for %d glyphs.", num_glyphs);
             return 0;
         }
@@ -1737,11 +1737,11 @@ CairoRenderContext::renderGlyphtext(PangoFont *font, Geom::Affine const &font_ma
     // create a cairo_font_face from PangoFont
     // double size = style->font_size.computed; /// \fixme why is this variable never used?
     gpointer fonthash = (gpointer)font;
-    cairo_font_face_t *font_face = NULL;
+    cairo_font_face_t *font_face = nullptr;
     if(font_table.find(fonthash)!=font_table.end())
         font_face = font_table[fonthash];
 
-    FcPattern *fc_pattern = NULL;
+    FcPattern *fc_pattern = nullptr;
 
 #ifdef USE_PANGO_WIN32
 # ifdef CAIRO_HAS_WIN32_FONT
@@ -1761,7 +1761,7 @@ CairoRenderContext::renderGlyphtext(PangoFont *font, Geom::Affine const &font_ma
 # ifdef CAIRO_HAS_FT_FONT
     PangoFcFont *fc_font = PANGO_FC_FONT(font);
     fc_pattern = fc_font->font_pattern;
-    if(font_face == NULL) {
+    if(font_face == nullptr) {
         font_face = cairo_ft_font_face_create_for_pattern(fc_pattern);
         font_table[fonthash] = font_face;
     }
diff --git a/src/extension/internal/cairo-render-context.h b/src/extension/internal/cairo-render-context.h
index 401b06885..2cefb297d 100644
--- a/src/extension/internal/cairo-render-context.h
+++ b/src/extension/internal/cairo-render-context.h
@@ -91,7 +91,7 @@ public:
     bool setPdfTarget(gchar const *utf8_fn);
     bool setPsTarget(gchar const *utf8_fn);
     /** Set the cairo_surface_t from an external source */
-    bool setSurfaceTarget(cairo_surface_t *surface, bool is_vector, cairo_matrix_t *ctm=NULL);
+    bool setSurfaceTarget(cairo_surface_t *surface, bool is_vector, cairo_matrix_t *ctm=nullptr);
 
     void setPSLevel(unsigned int level);
     void setEPS(bool eps);
@@ -215,7 +215,7 @@ protected:
 
     unsigned int _showGlyphs(cairo_t *cr, PangoFont *font, std::vector<CairoGlyphInfo> const &glyphtext, bool is_stroke);
 
-    bool _finishSurfaceSetup(cairo_surface_t *surface, cairo_matrix_t *ctm = NULL);
+    bool _finishSurfaceSetup(cairo_surface_t *surface, cairo_matrix_t *ctm = nullptr);
     void _setFillStyle(SPStyle const *style, Geom::OptRect const &pbox);
     void _setStrokeStyle(SPStyle const *style, Geom::OptRect const &pbox);
 
diff --git a/src/extension/internal/cairo-renderer-pdf-out.cpp b/src/extension/internal/cairo-renderer-pdf-out.cpp
index 5b9759c15..333c0eb42 100644
--- a/src/extension/internal/cairo-renderer-pdf-out.cpp
+++ b/src/extension/internal/cairo-renderer-pdf-out.cpp
@@ -49,7 +49,7 @@ bool CairoRendererPdfOutput::check(Inkscape::Extension::Extension * /*module*/)
 {
     bool result = true;
 
-    if (NULL == Inkscape::Extension::db.get("org.inkscape.output.pdf.cairorenderer")) {
+    if (nullptr == Inkscape::Extension::db.get("org.inkscape.output.pdf.cairorenderer")) {
         result = false;
     }
 
@@ -65,7 +65,7 @@ pdf_render_document_to_file(SPDocument *doc, gchar const *filename, unsigned int
 
 /* Start */
 
-    SPItem *base = NULL;
+    SPItem *base = nullptr;
 
     bool pageBoundingBox = TRUE;
     if (exportId && strcmp(exportId, "")) {
@@ -136,13 +136,13 @@ CairoRendererPdfOutput::save(Inkscape::Extension::Output *mod, SPDocument *doc,
     unsigned int ret;
 
     ext = Inkscape::Extension::db.get("org.inkscape.output.pdf.cairorenderer");
-    if (ext == NULL)
+    if (ext == nullptr)
         return;
 
     int level = 0;
     try {
         const gchar *new_level = mod->get_param_enum("PDFversion");
-        if((new_level != NULL) && (g_ascii_strcasecmp("PDF-1.5", new_level) == 0)) {
+        if((new_level != nullptr) && (g_ascii_strcasecmp("PDF-1.5", new_level) == 0)) {
             level = 1;
         }
     }
@@ -182,7 +182,7 @@ CairoRendererPdfOutput::save(Inkscape::Extension::Output *mod, SPDocument *doc,
         g_warning("Parameter <resolution> might not exist");
     }
 
-    const gchar *new_exportId = NULL;
+    const gchar *new_exportId = nullptr;
     try {
         new_exportId = mod->get_param_string("exportId");
     }
diff --git a/src/extension/internal/cairo-renderer.cpp b/src/extension/internal/cairo-renderer.cpp
index b48be2ed7..05605a9d9 100644
--- a/src/extension/internal/cairo-renderer.cpp
+++ b/src/extension/internal/cairo-renderer.cpp
@@ -117,9 +117,9 @@ CairoRenderContext*
 CairoRenderer::createContext(void)
 {
     CairoRenderContext *new_context = new CairoRenderContext(this);
-    g_assert( new_context != NULL );
+    g_assert( new_context != nullptr );
 
-    new_context->_state = NULL;
+    new_context->_state = nullptr;
 
     // create initial render state
     CairoRenderState *state = new_context->_createState();
@@ -516,7 +516,7 @@ static void sp_asbitmap_render(SPItem *item, CairoRenderContext *ctx)
     SPDocument *document = item->document;
 
     std::unique_ptr<Inkscape::Pixbuf> pb(
-        sp_generate_internal_bitmap(document, NULL,
+        sp_generate_internal_bitmap(document, nullptr,
             bbox->min()[Geom::X], bbox->min()[Geom::Y], bbox->max()[Geom::X], bbox->max()[Geom::Y], 
             width, height, res, res, (guint32) 0xffffff00, item ));
 
@@ -653,7 +653,7 @@ CairoRenderer::setupDocument(CairoRenderContext *ctx, SPDocument *doc, bool page
 {
 // PLEASE note when making changes to the boundingbox and transform calculation, corresponding changes should be made to PDFLaTeXRenderer::setupDocument !!!
 
-    g_assert( ctx != NULL );
+    g_assert( ctx != nullptr );
 
     if (!base) {
         base = doc->getRoot();
@@ -710,9 +710,9 @@ CairoRenderer::setupDocument(CairoRenderContext *ctx, SPDocument *doc, bool page
 void
 CairoRenderer::applyClipPath(CairoRenderContext *ctx, SPClipPath const *cp)
 {
-    g_assert( ctx != NULL && ctx->_is_valid );
+    g_assert( ctx != nullptr && ctx->_is_valid );
 
-    if (cp == NULL)
+    if (cp == nullptr)
         return;
 
     CairoRenderContext::CairoRenderMode saved_mode = ctx->getRenderMode();
@@ -766,9 +766,9 @@ CairoRenderer::applyClipPath(CairoRenderContext *ctx, SPClipPath const *cp)
 void
 CairoRenderer::applyMask(CairoRenderContext *ctx, SPMask const *mask)
 {
-    g_assert( ctx != NULL && ctx->_is_valid );
+    g_assert( ctx != nullptr && ctx->_is_valid );
 
-    if (mask == NULL)
+    if (mask == nullptr)
         return;
 
     // FIXME: the access to the first mask view to obtain the bbox is completely bogus
diff --git a/src/extension/internal/cdr-input.cpp b/src/extension/internal/cdr-input.cpp
index e6e7d4ed4..bf573cfac 100644
--- a/src/extension/internal/cdr-input.cpp
+++ b/src/extension/internal/cdr-input.cpp
@@ -245,7 +245,7 @@ SPDocument *CdrInput::open(Inkscape::Extension::Input * /*mod*/, const gchar * u
      #endif
 
      if (!libcdr::CDRDocument::isSupported(&input)) {
-          return NULL;
+          return nullptr;
      }
 
      RVNGStringVector output;
@@ -256,11 +256,11 @@ SPDocument *CdrInput::open(Inkscape::Extension::Input * /*mod*/, const gchar * u
 #else
      if (!libcdr::CDRDocument::generateSVG(&input, output)) {
 #endif
-          return NULL;
+          return nullptr;
      }
 
      if (output.empty()) {
-          return NULL;
+          return nullptr;
      }
 
      std::vector<RVNGString> tmpSVGOutput;
@@ -274,12 +274,12 @@ SPDocument *CdrInput::open(Inkscape::Extension::Input * /*mod*/, const gchar * u
 
      // If only one page is present, import that one without bothering user
      if (tmpSVGOutput.size() > 1) {
-          CdrImportDialog *dlg = 0;
+          CdrImportDialog *dlg = nullptr;
           if (INKSCAPE.use_gui()) {
                dlg = new CdrImportDialog(tmpSVGOutput);
                if (!dlg->showDialog()) {
                     delete dlg;
-                    return NULL;
+                    return nullptr;
                }
           }
 
diff --git a/src/extension/internal/emf-inout.cpp b/src/extension/internal/emf-inout.cpp
index 54099271b..f8cedcb50 100644
--- a/src/extension/internal/emf-inout.cpp
+++ b/src/extension/internal/emf-inout.cpp
@@ -80,7 +80,7 @@ Emf::~Emf (void) //The destructor
 bool
 Emf::check (Inkscape::Extension::Extension * /*module*/)
 {
-    if (NULL == Inkscape::Extension::db.get(PRINT_EMF))
+    if (nullptr == Inkscape::Extension::db.get(PRINT_EMF))
         return FALSE;
     return TRUE;
 }
@@ -121,8 +121,8 @@ Emf::print_document_to_file(SPDocument *doc, const gchar *filename)
     (void) mod->finish();
     /* Release arena */
     mod->base->invoke_hide(mod->dkey);
-    mod->base = NULL;
-    mod->root = NULL; // deleted by invoke_hide
+    mod->base = nullptr;
+    mod->root = nullptr; // deleted by invoke_hide
 /* end */
 
     mod->set_param_string("destination", oldoutput);
@@ -138,7 +138,7 @@ Emf::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar const *filena
     Inkscape::Extension::Extension * ext;
 
     ext = Inkscape::Extension::db.get(PRINT_EMF);
-    if (ext == NULL)
+    if (ext == nullptr)
         return;
 
     bool new_val                  = mod->get_param_bool("textToPath");
@@ -166,7 +166,7 @@ Emf::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar const *filena
     ext->set_param_bool("textToPath", new_val);
 
     // ensure usage of dot as decimal separator in scanf/printf functions (indepentendly of current locale)
-    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, NULL));
+    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, nullptr));
     setlocale(LC_NUMERIC, "C");
 
     print_document_to_file(doc, filename);
@@ -479,11 +479,11 @@ uint32_t Emf::add_image(PEMF_CALLBACK_DATA d,  void *pEmr, uint32_t cbBits, uint
     int  dibparams = U_BI_UNKNOWN;  // type of image not yet determined
 
     MEMPNG mempng; // PNG in memory comes back in this
-    mempng.buffer = NULL;
+    mempng.buffer = nullptr;
 
-    char            *rgba_px = NULL;     // RGBA pixels
-    const char      *px      = NULL;     // DIB pixels
-    const U_RGBQUAD *ct      = NULL;     // DIB color table
+    char            *rgba_px = nullptr;     // RGBA pixels
+    const char      *px      = nullptr;     // DIB pixels
+    const U_RGBQUAD *ct      = nullptr;     // DIB color table
     U_RGBQUAD        ct2[2];
     uint32_t width, height, colortype, numCt, invert; // if needed these values will be set in get_DIB_params
     if(cbBits && cbBmi  && (iUsage == U_DIB_RGB_COLORS)){
@@ -524,7 +524,7 @@ uint32_t Emf::add_image(PEMF_CALLBACK_DATA d,  void *pEmr, uint32_t cbBits, uint
         }
     }
 
-    gchar *base64String=NULL;
+    gchar *base64String=nullptr;
     if(dibparams == U_BI_JPEG || dibparams==U_BI_PNG){  // image was binary png or jpg in source file
         base64String = g_base64_encode((guchar*) px, numCt );
     }
@@ -749,7 +749,7 @@ int Emf::in_clips(PEMF_CALLBACK_DATA d, const char *test){
 void Emf::add_clips(PEMF_CALLBACK_DATA d, const char *clippath, unsigned int logic){
     int op = combine_ops_to_livarot(logic);
     Geom::PathVector combined_vect;
-    char *combined = NULL;
+    char *combined = nullptr;
     if (op >= 0 && d->dc[d->level].clip_id) {
         unsigned int real_idx = d->dc[d->level].clip_id - 1;
         Geom::PathVector old_vect = sp_svg_read_pathv(d->clips.strings[real_idx]);
@@ -1080,7 +1080,7 @@ std::string Emf::pix_to_xy(PEMF_CALLBACK_DATA d, double x, double y){
 void
 Emf::select_pen(PEMF_CALLBACK_DATA d, int index)
 {
-    PU_EMRCREATEPEN pEmr = NULL;
+    PU_EMRCREATEPEN pEmr = nullptr;
 
     if (index >= 0 && index < d->n_obj){
         pEmr = (PU_EMRCREATEPEN) d->emf_obj[index].lpEMFR;
@@ -1167,7 +1167,7 @@ Emf::select_pen(PEMF_CALLBACK_DATA d, int index)
 void
 Emf::select_extpen(PEMF_CALLBACK_DATA d, int index)
 {
-    PU_EMREXTCREATEPEN pEmr = NULL;
+    PU_EMREXTCREATEPEN pEmr = nullptr;
 
     if (index >= 0 && index < d->n_obj)
         pEmr = (PU_EMREXTCREATEPEN) d->emf_obj[index].lpEMFR;
@@ -1379,7 +1379,7 @@ Emf::select_brush(PEMF_CALLBACK_DATA d, int index)
 void
 Emf::select_font(PEMF_CALLBACK_DATA d, int index)
 {
-    PU_EMREXTCREATEFONTINDIRECTW pEmr = NULL;
+    PU_EMREXTCREATEFONTINDIRECTW pEmr = nullptr;
 
     if (index >= 0 && index < d->n_obj)
         pEmr = (PU_EMREXTCREATEFONTINDIRECTW) d->emf_obj[index].lpEMFR;
@@ -1423,7 +1423,7 @@ Emf::select_font(PEMF_CALLBACK_DATA d, int index)
     d->dc[d->level].style.text_decoration_line.set          = true;
     d->dc[d->level].style.text_decoration_line.inherit      = false;
     // malformed  EMF with empty filename may exist, ignore font change if encountered
-    char *ctmp = U_Utf16leToUtf8((uint16_t *) (pEmr->elfw.elfLogFont.lfFaceName), U_LF_FACESIZE, NULL);
+    char *ctmp = U_Utf16leToUtf8((uint16_t *) (pEmr->elfw.elfLogFont.lfFaceName), U_LF_FACESIZE, nullptr);
     if(ctmp){
         if (d->dc[d->level].font_name){ free(d->dc[d->level].font_name); }
         if(*ctmp){
@@ -1448,7 +1448,7 @@ Emf::delete_object(PEMF_CALLBACK_DATA d, int index)
 // files too big to fit into memory.
         if (d->emf_obj[index].lpEMFR)
             free(d->emf_obj[index].lpEMFR);
-        d->emf_obj[index].lpEMFR = NULL;
+        d->emf_obj[index].lpEMFR = nullptr;
     }
 }
 
@@ -1472,8 +1472,8 @@ int Emf::AI_hack(PU_EMRHEADER pEmr){
   char *ptr;
   ptr = (char *)pEmr;
   PU_EMRSETMAPMODE nEmr = (PU_EMRSETMAPMODE) (ptr + pEmr->emr.nSize);
-  char *string = NULL;
-  if(pEmr->nDescription)string = U_Utf16leToUtf8((uint16_t *)((char *) pEmr + pEmr->offDescription), pEmr->nDescription, NULL);
+  char *string = nullptr;
+  if(pEmr->nDescription)string = U_Utf16leToUtf8((uint16_t *)((char *) pEmr + pEmr->offDescription), pEmr->nDescription, nullptr);
   if(string){
      if((pEmr->nDescription >= 13) &&
         (0==strcmp("Adobe Systems",string)) &&
@@ -1526,12 +1526,12 @@ void Emf::common_image_extraction(PEMF_CALLBACK_DATA d, void *pEmr,
     tmp_image << " y=\"" << dy << "\"\n x=\"" << dx <<"\"\n ";
 
     MEMPNG mempng; // PNG in memory comes back in this
-    mempng.buffer = NULL;
+    mempng.buffer = nullptr;
 
-    char             *rgba_px = NULL;     // RGBA pixels
-    char             *sub_px  = NULL;     // RGBA pixels, subarray
-    const char       *px      = NULL;     // DIB pixels
-    const U_RGBQUAD  *ct      = NULL;     // DIB color table
+    char             *rgba_px = nullptr;     // RGBA pixels
+    char             *sub_px  = nullptr;     // RGBA pixels, subarray
+    const char       *px      = nullptr;     // DIB pixels
+    const U_RGBQUAD  *ct      = nullptr;     // DIB color table
     uint32_t width, height, colortype, numCt, invert; // if needed these values will be set in get_DIB_params
     if(cbBits && cbBmi && (iUsage == U_DIB_RGB_COLORS)){
         // next call returns pointers and values, but allocates no memory
@@ -1573,7 +1573,7 @@ void Emf::common_image_extraction(PEMF_CALLBACK_DATA d, void *pEmr,
         }
     }
 
-    gchar *base64String=NULL;
+    gchar *base64String=nullptr;
     if(dibparams == U_BI_JPEG){    // image was binary jpg in source file
         tmp_image << " xlink:href=\"data:image/jpeg;base64,";
         base64String = g_base64_encode((guchar*) px, numCt );
@@ -1630,14 +1630,14 @@ int Emf::myEnhMetaFileProc(char *contents, unsigned int length, PEMF_CALLBACK_DA
     int  eDbgComment=0;
     int  eDbgFinal=0;
     char const* eDbgString = getenv( "INKSCAPE_DBG_EMF" );
-    if ( eDbgString != NULL ) {
+    if ( eDbgString != nullptr ) {
         if(strstr(eDbgString,"RECORD")){  eDbgRecord  = 1; }
         if(strstr(eDbgString,"COMMENT")){ eDbgComment = 1; }
         if(strstr(eDbgString,"FINAL")){   eDbgFinal   = 1; }
     }
 
     /* initialize the tsp for text reassembly */
-    tsp.string     = NULL;
+    tsp.string     = nullptr;
     tsp.ori        = 0.0;  /* degrees */
     tsp.fs         = 12.0; /* font size */
     tsp.x          = 0.0;
@@ -1874,14 +1874,14 @@ std::cout << "BEFORE DRAW"
 
                 // Init the new emf_obj list elements to null, provided the
                 // dynamic allocation succeeded.
-                if ( d->emf_obj != NULL )
+                if ( d->emf_obj != nullptr )
                 {
                     for( int i=0; i < d->n_obj; ++i )
-                        d->emf_obj[i].lpEMFR = NULL;
+                        d->emf_obj[i].lpEMFR = nullptr;
                 } //if
 
             } else {
-                d->emf_obj = NULL;
+                d->emf_obj = nullptr;
             }
 
             break;
@@ -2352,7 +2352,7 @@ std::cout << "BEFORE DRAW"
                 }
                 if(d->dc[old_level].font_name){
                     free(d->dc[old_level].font_name); // else memory leak
-                    d->dc[old_level].font_name = NULL;
+                    d->dc[old_level].font_name = nullptr;
                 }
                 old_level--;
             }
@@ -3095,7 +3095,7 @@ std::cout << "BEFORE DRAW"
 
             /* Rotation issues are handled entirely in libTERE now */
 
-            uint32_t *dup_wt = NULL;
+            uint32_t *dup_wt = nullptr;
 
             if(       lpEMFR->iType==U_EMR_EXTTEXTOUTA){
                 /*  These should be JUST ASCII, but they might not be...
@@ -3103,20 +3103,20 @@ std::cout << "BEFORE DRAW"
                     If not, assume that it holds Latin1.
                     If that fails then something is really screwed up!
                 */
-                dup_wt = U_Utf8ToUtf32le((char *) pEmr + pEmr->emrtext.offString, pEmr->emrtext.nChars, NULL);
-                if(!dup_wt)dup_wt = U_Latin1ToUtf32le((char *) pEmr + pEmr->emrtext.offString, pEmr->emrtext.nChars, NULL);
+                dup_wt = U_Utf8ToUtf32le((char *) pEmr + pEmr->emrtext.offString, pEmr->emrtext.nChars, nullptr);
+                if(!dup_wt)dup_wt = U_Latin1ToUtf32le((char *) pEmr + pEmr->emrtext.offString, pEmr->emrtext.nChars, nullptr);
                 if(!dup_wt)dup_wt = unknown_chars(pEmr->emrtext.nChars);
             }
             else if(  lpEMFR->iType==U_EMR_EXTTEXTOUTW){
-                dup_wt = U_Utf16leToUtf32le((uint16_t *)((char *) pEmr + pEmr->emrtext.offString), pEmr->emrtext.nChars, NULL);
+                dup_wt = U_Utf16leToUtf32le((uint16_t *)((char *) pEmr + pEmr->emrtext.offString), pEmr->emrtext.nChars, nullptr);
                 if(!dup_wt)dup_wt = unknown_chars(pEmr->emrtext.nChars);
             }
             else { // U_EMR_SMALLTEXTOUT
                 if(pEmrS->fuOptions & U_ETO_SMALL_CHARS){
-                    dup_wt = U_Utf8ToUtf32le((char *) pEmrS + roff, cChars, NULL);
+                    dup_wt = U_Utf8ToUtf32le((char *) pEmrS + roff, cChars, nullptr);
                 }
                 else {
-                    dup_wt = U_Utf16leToUtf32le((uint16_t *)((char *) pEmrS + roff), cChars, NULL);
+                    dup_wt = U_Utf16leToUtf32le((uint16_t *)((char *) pEmrS + roff), cChars, nullptr);
                 }
                 if(!dup_wt)dup_wt = unknown_chars(cChars);
             }
@@ -3129,12 +3129,12 @@ std::cout << "BEFORE DRAW"
             }
 
             char *ansi_text;
-            ansi_text = (char *) U_Utf32leToUtf8((uint32_t *)dup_wt, 0, NULL);
+            ansi_text = (char *) U_Utf32leToUtf8((uint32_t *)dup_wt, 0, nullptr);
             free(dup_wt);
             // Empty string or starts with an invalid escape/control sequence, which is bogus text.  Throw it out before g_markup_escape_text can make things worse
             if(*((uint8_t *)ansi_text) <= 0x1F){
                 free(ansi_text);
-                ansi_text=NULL;
+                ansi_text=nullptr;
             }
 
             if (ansi_text) {
@@ -3528,18 +3528,18 @@ void Emf::free_emf_strings(EMF_STRINGS name){
 SPDocument *
 Emf::open( Inkscape::Extension::Input * /*mod*/, const gchar *uri )
 {
-    if (uri == NULL) {
-        return NULL;
+    if (uri == nullptr) {
+        return nullptr;
     }
 
     // ensure usage of dot as decimal separator in scanf/printf functions (indepentendly of current locale)
-    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, NULL));
+    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, nullptr));
     setlocale(LC_NUMERIC, "C");
 
     EMF_CALLBACK_DATA d;
 
     d.n_obj   = 0;     //these might not be set otherwise if the input file is corrupt
-    d.emf_obj = NULL; 
+    d.emf_obj = nullptr; 
     d.dc[0].font_name = strdup("Arial"); // Default font, set only on lowest level, it copies up from there EMF spec says device can pick whatever it wants
 
     // set up the size default for patterns in defs.  This might not be referenced if there are no patterns defined in the drawing.
@@ -3556,12 +3556,12 @@ Emf::open( Inkscape::Extension::Input * /*mod*/, const gchar *uri )
 
     size_t length;
     char *contents;
-    if(emf_readdata(uri, &contents, &length))return(NULL);
+    if(emf_readdata(uri, &contents, &length))return(nullptr);
 
-    d.pDesc = NULL;
+    d.pDesc = nullptr;
 
     // set up the text reassembly system
-    if(!(d.tri = trinfo_init(NULL)))return(NULL);
+    if(!(d.tri = trinfo_init(nullptr)))return(nullptr);
     (void) trinfo_load_ft_opts(d.tri, 1,
       FT_LOAD_NO_SCALE | FT_LOAD_NO_HINTING  | FT_LOAD_NO_BITMAP,
       FT_KERNING_UNSCALED);
@@ -3573,7 +3573,7 @@ Emf::open( Inkscape::Extension::Input * /*mod*/, const gchar *uri )
 
 //    std::cout << "SVG Output: " << std::endl << d.outsvg << std::endl;
 
-    SPDocument *doc = NULL;
+    SPDocument *doc = nullptr;
     if (good) {
         doc = SPDocument::createNewDocFromMem(d.outsvg.c_str(), strlen(d.outsvg.c_str()), TRUE);
     }
diff --git a/src/extension/internal/emf-inout.h b/src/extension/internal/emf-inout.h
index 3c2a814aa..bef58b612 100644
--- a/src/extension/internal/emf-inout.h
+++ b/src/extension/internal/emf-inout.h
@@ -33,7 +33,7 @@ typedef struct emf_object {
     emf_object() :
         type(0),
         level(0),
-        lpEMFR(NULL)
+        lpEMFR(nullptr)
     {};
     int type;
     int level;
@@ -44,7 +44,7 @@ typedef struct emf_strings {
     emf_strings() :
         size(0),
         count(0),
-        strings(NULL)
+        strings(nullptr)
     {};
     int size;         // number of slots allocated in strings
     int count;        // number of slots used in strings
@@ -54,7 +54,7 @@ typedef struct emf_strings {
 typedef struct emf_device_context {
     emf_device_context() :
         // SPStyle: class with constructor
-        font_name(NULL),
+        font_name(nullptr),
         clip_id(0),
         stroke_set(false), stroke_mode(0), stroke_idx(0), stroke_recidx(0),
         fill_set(false),   fill_mode(0),   fill_idx(0),   fill_recidx(0),
@@ -67,7 +67,7 @@ typedef struct emf_device_context {
         textAlign(0)
         // worldTransform, cur
     {
-        font_name = NULL;
+        font_name = nullptr;
         sizeWnd  = sizel_set( 0.0, 0.0 );
         sizeView = sizel_set( 0.0, 0.0 );
         winorg  = point32_set( 0.0, 0.0 );
@@ -127,9 +127,9 @@ typedef struct emf_callback_data {
         dwRop2(U_R2_COPYPEN), dwRop3(0),
         MMX(0),MMY(0),
         drawtype(0),
-        pDesc(NULL),
+        pDesc(nullptr),
         // hatches, images, gradients,  struct w/ constructor
-        tri(NULL),
+        tri(nullptr),
         n_obj(0)
         // emf_obj;
     {};
diff --git a/src/extension/internal/emf-print.cpp b/src/extension/internal/emf-print.cpp
index 0b005f8da..ec4594eea 100644
--- a/src/extension/internal/emf-print.cpp
+++ b/src/extension/internal/emf-print.cpp
@@ -75,8 +75,8 @@ namespace Internal {
 /* globals */
 static double       PX2WORLD;
 static bool         FixPPTCharPos, FixPPTDashLine, FixPPTGrad2Polys, FixPPTLinGrad, FixPPTPatternAsHatch, FixImageRot;
-static EMFTRACK    *et               = NULL;
-static EMFHANDLES  *eht              = NULL;
+static EMFTRACK    *et               = nullptr;
+static EMFHANDLES  *eht              = nullptr;
 
 void PrintEmf::smuggle_adxkyrtl_out(const char *string, uint32_t **adx, double *ky, int *rtl, int *ndx, float scale)
 {
@@ -85,7 +85,7 @@ void PrintEmf::smuggle_adxkyrtl_out(const char *string, uint32_t **adx, double *
     uint32_t   *ladx;
     const char *cptr = &string[strlen(string) + 1]; // this works because of the first fake terminator
 
-    *adx = NULL;
+    *adx = nullptr;
     *ky  = 0.0;       // set a default value
     sscanf(cptr, "%7d", ndx);
     if (!*ndx) {
@@ -207,12 +207,12 @@ unsigned int PrintEmf::begin(Inkscape::Extension::Print *mod, SPDocument *doc)
         p = ansi_uri;
     }
     snprintf(buff, sizeof(buff) - 1, "Inkscape %s \1%s\1", Inkscape::version_string, p);
-    uint16_t *Description = U_Utf8ToUtf16le(buff, 0, NULL);
+    uint16_t *Description = U_Utf8ToUtf16le(buff, 0, nullptr);
     int cbDesc = 2 + wchar16len(Description);      // also count the final terminator
     (void) U_Utf16leEdit(Description, '\1', '\0'); // swap the temporary \1 characters for nulls
 
     // construct the EMRHEADER record and append it to the EMF in memory
-    rec = U_EMRHEADER_set(rclBounds,  rclFrame,  NULL, cbDesc, Description, szlDev, szlMm, 0);
+    rec = U_EMRHEADER_set(rclBounds,  rclFrame,  nullptr, cbDesc, Description, szlDev, szlMm, 0);
     free(Description);
     if (!rec || emf_append((PU_ENHMETARECORD)rec, et, U_REC_FREE)) {
         g_error("Fatal programming error in PrintEmf::begin at EMRHEADER");
@@ -301,7 +301,7 @@ unsigned int PrintEmf::begin(Inkscape::Extension::Print *mod, SPDocument *doc)
 
 unsigned int PrintEmf::finish(Inkscape::Extension::Print * /*mod*/)
 {
-    do_clip_if_present(NULL);  // Terminate any open clip.
+    do_clip_if_present(nullptr);  // Terminate any open clip.
     char *rec;
     if (!et) {
         return 0;
@@ -310,7 +310,7 @@ unsigned int PrintEmf::finish(Inkscape::Extension::Print * /*mod*/)
 
     // earlier versions had flush of fill here, but it never executed and was removed
 
-    rec = U_EMREOF_set(0, NULL, et); // generate the EOF record
+    rec = U_EMREOF_set(0, nullptr, et); // generate the EOF record
     if (!rec || emf_append((PU_ENHMETARECORD)rec, et, U_REC_FREE)) {
         g_error("Fatal programming error in PrintEmf::finish");
     }
@@ -410,8 +410,8 @@ int PrintEmf::create_brush(SPStyle const *style, PU_COLORREF fcolor)
         } else if (SP_IS_GRADIENT(SP_STYLE_FILL_SERVER(style))) { // must be a gradient
             // currently we do not do anything with gradients, the code below just sets the color to the average of the stops
             SPPaintServer *paintserver = style->fill.value.href->getObject();
-            SPLinearGradient *lg = NULL;
-            SPRadialGradient *rg = NULL;
+            SPLinearGradient *lg = nullptr;
+            SPRadialGradient *rg = nullptr;
 
             if (SP_IS_LINEARGRADIENT(paintserver)) {
                 lg = SP_LINEARGRADIENT(paintserver);
@@ -533,8 +533,8 @@ int PrintEmf::create_pen(SPStyle const *style, const Geom::Affine &transform)
 {
     U_EXTLOGPEN         *elp;
     U_NUM_STYLEENTRY     n_dash    = 0;
-    U_STYLEENTRY        *dash      = NULL;
-    char                *rec       = NULL;
+    U_STYLEENTRY        *dash      = nullptr;
+    char                *rec       = nullptr;
     int                  linestyle = U_PS_SOLID;
     int                  linecap   = 0;
     int                  linejoin  = 0;
@@ -545,14 +545,14 @@ int PrintEmf::create_pen(SPStyle const *style, const Geom::Affine &transform)
     U_COLORREF           hatchColor;
     U_COLORREF           bkColor;
     uint32_t             width, height;
-    char                *px = NULL;
+    char                *px = nullptr;
     char                *rgba_px;
     uint32_t             cbPx = 0;
     uint32_t             colortype;
-    PU_RGBQUAD           ct = NULL;
+    PU_RGBQUAD           ct = nullptr;
     int                  numCt = 0;
     U_BITMAPINFOHEADER   Bmih;
-    PU_BITMAPINFO        Bmi = NULL;
+    PU_BITMAPINFO        Bmi = nullptr;
 
     if (!et) {
         return 0;
@@ -729,7 +729,7 @@ int PrintEmf::create_pen(SPStyle const *style, const Geom::Affine &transform)
                   U_RGB(0, 0, 0),
                   U_HS_HORIZONTAL,
                   0,
-                  NULL);
+                  nullptr);
     }
 
     rec = extcreatepen_set(&pen, eht,  Bmi, cbPx, px, elp);
@@ -772,7 +772,7 @@ int PrintEmf::create_pen(SPStyle const *style, const Geom::Affine &transform)
 // set the current pen to the stock object NULL_PEN and then delete the defined pen object, if there is one.
 void PrintEmf::destroy_pen()
 {
-    char *rec = NULL;
+    char *rec = nullptr;
     // before an object may be safely deleted it must no longer be selected
     // select in a stock object to deselect this one, the stock object should
     // never be used because we always select in a new one before drawing anythingrestore previous brush, necessary??? Would using a default stock object not work?
@@ -987,14 +987,14 @@ U_TRIVERTEX PrintEmf::make_trivertex(Geom::Point Pt, U_COLORREF uc){
 */
 void  PrintEmf::do_clip_if_present(SPStyle const *style){
     char *rec;
-    static SPClipPath *scpActive = NULL;
+    static SPClipPath *scpActive = nullptr;
     if(!style){
         if(scpActive){  // clear the existing clip
             rec = U_EMRRESTOREDC_set(-1);
             if (!rec || emf_append((PU_ENHMETARECORD)rec, et, U_REC_FREE)) {
                 g_error("Fatal programming error in PrintEmf::fill at U_EMRRESTOREDC_set");
             }
-            scpActive=NULL;
+            scpActive=nullptr;
         }
     } else {
         /* The current implementation converts only one level of clipping.  If there were more
@@ -1005,10 +1005,10 @@ void  PrintEmf::do_clip_if_present(SPStyle const *style){
            Note, to debug this section of code use print statements on sp_svg_write_path(combined_pathvector).
         */
         /*  find the first clip_ref at object or up the stack.  There may not be one. */
-        SPClipPath *scp = NULL;
+        SPClipPath *scp = nullptr;
         SPItem *item = SP_ITEM(style->object);
         while(1) {
-            scp = (item->clip_ref ? item->clip_ref->getObject() : NULL);
+            scp = (item->clip_ref ? item->clip_ref->getObject() : nullptr);
             if(scp)break;
             item = SP_ITEM(item->parent);
             if(!item || SP_IS_ROOT(item))break; // this will never be a clipping path
@@ -1020,7 +1020,7 @@ void  PrintEmf::do_clip_if_present(SPStyle const *style){
                 if (!rec || emf_append((PU_ENHMETARECORD)rec, et, U_REC_FREE)) {
                     g_error("Fatal programming error in PrintEmf::fill at U_EMRRESTOREDC_set");
                 }
-                scpActive = NULL;
+                scpActive = nullptr;
             }
 
             if (scp) {  // set the new clip
@@ -1067,7 +1067,7 @@ void  PrintEmf::do_clip_if_present(SPStyle const *style){
                     }
                 }
                 else {
-                    scpActive = NULL; // no valid path available to draw, so no DC was saved, so no signal to restore
+                    scpActive = nullptr; // no valid path available to draw, so no DC was saved, so no signal to restore
                 }
             } // change or remove clipping
         } // scp exists
@@ -1133,7 +1133,7 @@ unsigned int PrintEmf::fill(
 
     fill_transform = tf;
     
-    int brush_stat = create_brush(style, NULL);
+    int brush_stat = create_brush(style, nullptr);
     
     /* native linear gradients are only used if the object is a rectangle AND the gradient is parallel to the sides of the object */
     bool is_Rect = false;
@@ -1428,7 +1428,7 @@ unsigned int PrintEmf::stroke(
     Geom::OptRect const &/*pbox*/, Geom::OptRect const &/*dbox*/, Geom::OptRect const &/*bbox*/)
 {
 
-    char *rec = NULL;
+    char *rec = nullptr;
     Geom::Affine tf = m_tr_stack.top();
     do_clip_if_present(style);  // If clipping is needed set it up
 
@@ -1508,7 +1508,7 @@ bool PrintEmf::print_simple_shape(Geom::PathVector const &pathv, const Geom::Aff
     int moves  = 0;
     int lines  = 0;
     int curves = 0;
-    char *rec  = NULL;
+    char *rec  = nullptr;
 
     for (Geom::PathVector::iterator pit = pv.begin(); pit != pv.end(); ++pit) {
         moves++;
@@ -1718,7 +1718,7 @@ unsigned int PrintEmf::image(
     SPStyle const *style)  /** provides indirect link to image object */
 {
     double x1, y1, dw, dh;
-    char *rec = NULL;
+    char *rec = nullptr;
     Geom::Affine tf = m_tr_stack.top();
 
     do_clip_if_present(style);  // If clipping is needed set it up
@@ -1923,7 +1923,7 @@ unsigned int PrintEmf::draw_pathv_to_EMF(Geom::PathVector const &pathv, const Ge
 unsigned int PrintEmf::print_pathv(Geom::PathVector const &pathv, const Geom::Affine &transform)
 {
     Geom::Affine tf = transform;
-    char *rec = NULL;
+    char *rec = nullptr;
 
     simple_shape = print_simple_shape(pathv, tf);
     if (simple_shape || pathv.empty()) {
@@ -1976,7 +1976,7 @@ unsigned int PrintEmf::text(Inkscape::Extension::Print * /*mod*/, char const *te
     }
 
     do_clip_if_present(style);  // If clipping is needed set it up
-    char *rec = NULL;
+    char *rec = nullptr;
     int ccount, newfont;
     int fix90n = 0;
     uint32_t hfont = 0;
@@ -2006,7 +2006,7 @@ unsigned int PrintEmf::text(Inkscape::Extension::Print * /*mod*/, char const *te
     }
 
     char *text2 = strdup(text);  // because U_Utf8ToUtf16le calls iconv which does not like a const char *
-    uint16_t *unicode_text = U_Utf8ToUtf16le(text2, 0, NULL);
+    uint16_t *unicode_text = U_Utf8ToUtf16le(text2, 0, nullptr);
     free(text2);
     //translates Unicode to NonUnicode, if possible.  If any translate, all will, and all to
     //the same font, because of code in Layout::print
@@ -2058,9 +2058,9 @@ unsigned int PrintEmf::text(Inkscape::Extension::Print * /*mod*/, char const *te
         // of the special fonts.
         uint16_t *wfacename;
         if (!newfont) {
-            wfacename = U_Utf8ToUtf16le(style->font_family.value, 0, NULL);
+            wfacename = U_Utf8ToUtf16le(style->font_family.value, 0, nullptr);
         } else {
-            wfacename = U_Utf8ToUtf16le(FontName(newfont), 0, NULL);
+            wfacename = U_Utf8ToUtf16le(FontName(newfont), 0, nullptr);
         }
 
         // Scale the text to the minimum stretch. (It tends to stay within bounding rectangles even if
@@ -2084,7 +2084,7 @@ unsigned int PrintEmf::text(Inkscape::Extension::Print * /*mod*/, char const *te
                            wfacename);
         free(wfacename);
 
-        rec  = extcreatefontindirectw_set(&hfont, eht, (char *) &lf, NULL);
+        rec  = extcreatefontindirectw_set(&hfont, eht, (char *) &lf, nullptr);
         if (!rec || emf_append((PU_ENHMETARECORD)rec, et, U_REC_FREE)) {
             g_error("Fatal programming error in PrintEmf::text at extcreatefontindirectw_set");
         }
diff --git a/src/extension/internal/filter/bevels.h b/src/extension/internal/filter/bevels.h
index 91fe2f8cf..4c2ddc719 100644
--- a/src/extension/internal/filter/bevels.h
+++ b/src/extension/internal/filter/bevels.h
@@ -45,7 +45,7 @@ protected:
 
 public:
     DiffuseLight ( ) : Filter() { };
-    ~DiffuseLight ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~DiffuseLight ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -73,7 +73,7 @@ public:
 gchar const *
 DiffuseLight::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream smooth;
     std::ostringstream elevation;
@@ -125,7 +125,7 @@ protected:
 
 public:
     MatteJelly ( ) : Filter() { };
-    ~MatteJelly ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~MatteJelly ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -154,7 +154,7 @@ public:
 gchar const *
 MatteJelly::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream smooth;
     std::ostringstream bright;
@@ -209,7 +209,7 @@ protected:
 
 public:
     SpecularLight ( ) : Filter() { };
-    ~SpecularLight ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~SpecularLight ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -238,7 +238,7 @@ public:
 gchar const *
 SpecularLight::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream smooth;
     std::ostringstream bright;
diff --git a/src/extension/internal/filter/blurs.h b/src/extension/internal/filter/blurs.h
index 0956b23b6..c99b9efac 100644
--- a/src/extension/internal/filter/blurs.h
+++ b/src/extension/internal/filter/blurs.h
@@ -46,7 +46,7 @@ protected:
 
 public:
     Blur ( ) : Filter() { };
-    ~Blur ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Blur ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -73,7 +73,7 @@ public:
 gchar const *
 Blur::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream bbox;
     std::ostringstream hblur;
@@ -117,7 +117,7 @@ protected:
 
 public:
     CleanEdges ( ) : Filter() { };
-    ~CleanEdges ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~CleanEdges ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -142,7 +142,7 @@ public:
 gchar const *
 CleanEdges::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream blur;
 
@@ -177,7 +177,7 @@ protected:
 
 public:
     CrossBlur ( ) : Filter() { };
-    ~CrossBlur ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~CrossBlur ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -211,7 +211,7 @@ public:
 gchar const *
 CrossBlur::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream bright;
     std::ostringstream fade;
@@ -252,7 +252,7 @@ protected:
 
 public:
     Feather ( ) : Filter() { };
-    ~Feather ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Feather ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -277,7 +277,7 @@ public:
 gchar const *
 Feather::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream blur;
 
@@ -317,7 +317,7 @@ protected:
 
 public:
     ImageBlur ( ) : Filter() { };
-    ~ImageBlur ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~ImageBlur ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -361,7 +361,7 @@ public:
 gchar const *
 ImageBlur::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream hblur;
     std::ostringstream vblur;
diff --git a/src/extension/internal/filter/bumps.h b/src/extension/internal/filter/bumps.h
index 95f6170f3..0eaee7a5f 100644
--- a/src/extension/internal/filter/bumps.h
+++ b/src/extension/internal/filter/bumps.h
@@ -72,7 +72,7 @@ protected:
 
 public:
     Bump ( ) : Filter() { };
-    ~Bump ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Bump ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -152,7 +152,7 @@ public:
 gchar const *
 Bump::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream simplifyImage;
     std::ostringstream simplifyBump;
@@ -301,7 +301,7 @@ protected:
 
 public:
     WaxBump ( ) : Filter() { };
-    ~WaxBump ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~WaxBump ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -372,7 +372,7 @@ public:
 gchar const *
 WaxBump::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream simplifyImage;
     std::ostringstream simplifyBump;
diff --git a/src/extension/internal/filter/color.h b/src/extension/internal/filter/color.h
index 063073267..ae6bc718c 100644
--- a/src/extension/internal/filter/color.h
+++ b/src/extension/internal/filter/color.h
@@ -66,7 +66,7 @@ protected:
 
 public:
     Brilliance ( ) : Filter() { };
-    ~Brilliance ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Brilliance ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -93,7 +93,7 @@ public:
 gchar const *
 Brilliance::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream brightness;
     std::ostringstream sat;
@@ -146,7 +146,7 @@ protected:
 
 public:
     ChannelPaint ( ) : Filter() { };
-    ~ChannelPaint ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~ChannelPaint ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
     
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -182,7 +182,7 @@ public:
 gchar const *
 ChannelPaint::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream saturation;
     std::ostringstream red;
@@ -247,7 +247,7 @@ protected:
 
 public:
     ColorBlindness ( ) : Filter() { };
-    ~ColorBlindness ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~ColorBlindness ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
     
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -293,7 +293,7 @@ public:
 gchar const *
 ColorBlindness::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream type;
     type << ext->get_param_enum("type");
@@ -322,7 +322,7 @@ protected:
 
 public:
     ColorShift ( ) : Filter() { };
-    ~ColorShift ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~ColorShift ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -348,7 +348,7 @@ public:
 gchar const *
 ColorShift::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream shift;
     std::ostringstream sat;
@@ -385,7 +385,7 @@ protected:
 
 public:
     Colorize ( ) : Filter() { };
-    ~Colorize ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Colorize ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -433,7 +433,7 @@ public:
 gchar const *
 Colorize::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream a;
     std::ostringstream r;
@@ -492,7 +492,7 @@ protected:
 
 public:
     ComponentTransfer ( ) : Filter() { };
-    ~ComponentTransfer ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~ComponentTransfer ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -522,7 +522,7 @@ public:
 gchar const *
 ComponentTransfer::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream CTfunction;
     const gchar *type = ext->get_param_enum("type");
@@ -577,7 +577,7 @@ protected:
 
 public:
     Duochrome ( ) : Filter() { };
-    ~Duochrome ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Duochrome ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -618,7 +618,7 @@ public:
 gchar const *
 Duochrome::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream a1;
     std::ostringstream r1;
@@ -702,7 +702,7 @@ protected:
 
 public:
     ExtractChannel ( ) : Filter() { };
-    ~ExtractChannel ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~ExtractChannel ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -739,7 +739,7 @@ public:
 gchar const *
 ExtractChannel::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream blend;
     std::ostringstream colors;
@@ -808,7 +808,7 @@ protected:
 
 public:
     FadeToBW ( ) : Filter() { };
-    ~FadeToBW ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~FadeToBW ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -836,7 +836,7 @@ public:
 gchar const *
 FadeToBW::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream level;
     std::ostringstream wlevel;
@@ -887,7 +887,7 @@ protected:
 
 public:
     Greyscale ( ) : Filter() { };
-    ~Greyscale ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Greyscale ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -915,7 +915,7 @@ public:
 gchar const *
 Greyscale::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream red;
     std::ostringstream green;
@@ -973,7 +973,7 @@ protected:
 
 public:
     Invert ( ) : Filter() { };
-    ~Invert ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Invert ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1007,7 +1007,7 @@ public:
 gchar const *
 Invert::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream line1;
     std::ostringstream line2;
@@ -1108,7 +1108,7 @@ protected:
 
 public:
     Lighting ( ) : Filter() { };
-    ~Lighting ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Lighting ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1134,7 +1134,7 @@ public:
 gchar const *
 Lighting::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream amplitude;
     std::ostringstream exponent;
@@ -1179,7 +1179,7 @@ protected:
 
 public:
     LightnessContrast ( ) : Filter() { };
-    ~LightnessContrast ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~LightnessContrast ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1204,7 +1204,7 @@ public:
 gchar const *
 LightnessContrast::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream lightness;
     std::ostringstream contrast;
@@ -1258,7 +1258,7 @@ protected:
 
 public:
     NudgeRGB ( ) : Filter() { };
-    ~NudgeRGB ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~NudgeRGB ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1297,7 +1297,7 @@ public:
 gchar const *
 NudgeRGB::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream rx;
     std::ostringstream ry;
@@ -1370,7 +1370,7 @@ protected:
 
 public:
     NudgeCMY ( ) : Filter() { };
-    ~NudgeCMY ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~NudgeCMY ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1409,7 +1409,7 @@ public:
 gchar const *
 NudgeCMY::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream cx;
     std::ostringstream cy;
@@ -1476,7 +1476,7 @@ protected:
 
 public:
     Quadritone ( ) : Filter() { };
-    ~Quadritone ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Quadritone ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1515,7 +1515,7 @@ public:
 gchar const *
 Quadritone::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream dist;
     std::ostringstream colors;
@@ -1559,7 +1559,7 @@ protected:
 
 public:
     SimpleBlend ( ) : Filter() { };
-    ~SimpleBlend ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~SimpleBlend ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
     
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1600,7 +1600,7 @@ public:
 gchar const *
 SimpleBlend::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream a;
     std::ostringstream r;
@@ -1645,7 +1645,7 @@ protected:
 
 public:
     Solarize ( ) : Filter() { };
-    ~Solarize ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Solarize ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1674,7 +1674,7 @@ public:
 gchar const *
 Solarize::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream rotate;
     std::ostringstream blend1;
@@ -1732,7 +1732,7 @@ protected:
 
 public:
     Tritone ( ) : Filter() { };
-    ~Tritone ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Tritone ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -1785,7 +1785,7 @@ public:
 gchar const *
 Tritone::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
     
     std::ostringstream dist;
     std::ostringstream a;
diff --git a/src/extension/internal/filter/distort.h b/src/extension/internal/filter/distort.h
index 6d1fc0a75..f1654d075 100644
--- a/src/extension/internal/filter/distort.h
+++ b/src/extension/internal/filter/distort.h
@@ -59,7 +59,7 @@ protected:
 
 public:
     FeltFeather ( ) : Filter() { };
-    ~FeltFeather ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~FeltFeather ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -106,7 +106,7 @@ public:
 gchar const *
 FeltFeather::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
 
     std::ostringstream hblur;
@@ -182,7 +182,7 @@ protected:
 
 public:
     Roughen ( ) : Filter() { };
-    ~Roughen ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Roughen ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -215,7 +215,7 @@ public:
 gchar const *
 Roughen::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
   
     std::ostringstream type;
     std::ostringstream hfreq;
diff --git a/src/extension/internal/filter/filter-file.cpp b/src/extension/internal/filter/filter-file.cpp
index 07a7eb0af..241f0f52c 100644
--- a/src/extension/internal/filter/filter-file.cpp
+++ b/src/extension/internal/filter/filter-file.cpp
@@ -34,7 +34,7 @@ void
 filters_load_file (Glib::ustring filename, gchar * menuname)
 {
     Inkscape::XML::Document *doc = sp_repr_read_file(filename.c_str(), INKSCAPE_EXTENSION_URI);
-	if (doc == NULL) {
+	if (doc == nullptr) {
 		g_warning("File (%s) is not parseable as XML.  Ignored.", filename.c_str());
 		return;
 	}
@@ -47,10 +47,10 @@ filters_load_file (Glib::ustring filename, gchar * menuname)
 	}
 
 	for (Inkscape::XML::Node * child = root->firstChild();
-			child != NULL; child = child->next()) {
+			child != nullptr; child = child->next()) {
 		if (!strcmp(child->name(), "svg:defs")) {
 			for (Inkscape::XML::Node * defs = child->firstChild();
-					defs != NULL; defs = defs->next()) {
+					defs != nullptr; defs = defs->next()) {
 				if (!strcmp(defs->name(), "svg:filter")) {
                                     Filter::filters_load_node(defs, menuname);
 				} // oh!  a filter
@@ -97,7 +97,7 @@ Filter::filters_load_node (Inkscape::XML::Node * node, gchar * menuname)
 	gchar const * menu_tooltip = node->attribute("inkscape:menu-tooltip");
 	gchar const * id = node->attribute("id");
 
-	if (label == NULL) {
+	if (label == nullptr) {
 		label = id;
 	}
 
diff --git a/src/extension/internal/filter/filter.cpp b/src/extension/internal/filter/filter.cpp
index 166e5406f..8e32bc05d 100644
--- a/src/extension/internal/filter/filter.cpp
+++ b/src/extension/internal/filter/filter.cpp
@@ -27,7 +27,7 @@ namespace Filter {
 
 Filter::Filter() :
 		Inkscape::Extension::Implementation::Implementation(),
-		_filter(NULL) {
+		_filter(nullptr) {
 	return;
 }
 
@@ -38,8 +38,8 @@ Filter::Filter(gchar const * filter) :
 }
 
 Filter::~Filter (void) {
-	if (_filter != NULL) {
-		_filter = NULL;
+	if (_filter != nullptr) {
+		_filter = nullptr;
 	}
 
 	return;
@@ -53,7 +53,7 @@ bool Filter::load(Inkscape::Extension::Extension * /*module*/)
 Inkscape::Extension::Implementation::ImplementationDocumentCache *Filter::newDocCache(Inkscape::Extension::Extension * /*ext*/,
 										      Inkscape::UI::View::View * /*doc*/)
 {
-    return NULL;
+    return nullptr;
 }
 
 gchar const *Filter::get_filter_text(Inkscape::Extension::Extension * /*ext*/)
@@ -64,7 +64,7 @@ gchar const *Filter::get_filter_text(Inkscape::Extension::Extension * /*ext*/)
 Inkscape::XML::Document *
 Filter::get_filter (Inkscape::Extension::Extension * ext) {
 	gchar const * filter = get_filter_text(ext);
-	return sp_repr_read_mem(filter, strlen(filter), NULL);
+	return sp_repr_read_mem(filter, strlen(filter), nullptr);
 }
 
 void
@@ -72,7 +72,7 @@ Filter::merge_filters( Inkscape::XML::Node * to, Inkscape::XML::Node * from,
 		       Inkscape::XML::Document * doc,
 		       gchar const * srcGraphic, gchar const * srcGraphicAlpha)
 {
-	if (from == NULL) return;
+	if (from == nullptr) return;
 
 	// copy attributes
     for ( Inkscape::Util::List<Inkscape::XML::AttributeRecord const> iter = from->attributeList() ;
@@ -83,11 +83,11 @@ Filter::merge_filters( Inkscape::XML::Node * to, Inkscape::XML::Node * from,
 		to->setAttribute(attr, from->attribute(attr));
 
 		if (!strcmp(attr, "in") || !strcmp(attr, "in2") || !strcmp(attr, "in3")) {
-			if (srcGraphic != NULL && !strcmp(from->attribute(attr), "SourceGraphic")) {
+			if (srcGraphic != nullptr && !strcmp(from->attribute(attr), "SourceGraphic")) {
 				to->setAttribute(attr, srcGraphic);
 			}
 
-			if (srcGraphicAlpha != NULL && !strcmp(from->attribute(attr), "SourceAlpha")) {
+			if (srcGraphicAlpha != nullptr && !strcmp(from->attribute(attr), "SourceAlpha")) {
 				to->setAttribute(attr, srcGraphicAlpha);
 			}
 		}
@@ -95,7 +95,7 @@ Filter::merge_filters( Inkscape::XML::Node * to, Inkscape::XML::Node * from,
 
 	// for each child call recursively
 	for (Inkscape::XML::Node * from_child = from->firstChild();
-	          from_child != NULL ; from_child = from_child->next()) {
+	          from_child != nullptr ; from_child = from_child->next()) {
 		Glib::ustring name = "svg:";
 		name += from_child->name();
 
@@ -103,7 +103,7 @@ Filter::merge_filters( Inkscape::XML::Node * to, Inkscape::XML::Node * from,
 		to->appendChild(to_child);
 		merge_filters(to_child, from_child, doc, srcGraphic, srcGraphicAlpha);
 
-		if (from_child == from->firstChild() && !strcmp("filter", from->name()) && srcGraphic != NULL && to_child->attribute("in") == NULL) {
+		if (from_child == from->firstChild() && !strcmp("filter", from->name()) && srcGraphic != nullptr && to_child->attribute("in") == nullptr) {
 			to_child->setAttribute("in", srcGraphic);
 		}
     Inkscape::GC::release(to_child);
@@ -117,7 +117,7 @@ void Filter::effect(Inkscape::Extension::Effect *module, Inkscape::UI::View::Vie
 		    Inkscape::Extension::Implementation::ImplementationDocumentCache * /*docCache*/)
 {
 	Inkscape::XML::Document *filterdoc = get_filter(module);
-	if (filterdoc == NULL) {
+	if (filterdoc == nullptr) {
 		return; // could not parse the XML source of the filter; typically parser will stderr a warning
 	}
 
@@ -136,9 +136,9 @@ void Filter::effect(Inkscape::Extension::Effect *module, Inkscape::UI::View::Vie
 	Inkscape::XML::Node * node = spitem->getRepr();
 
 		SPCSSAttr * css = sp_repr_css_attr(node, "style");
-		gchar const * filter = sp_repr_css_property(css, "filter", NULL);
+		gchar const * filter = sp_repr_css_property(css, "filter", nullptr);
 
-		if (filter == NULL) {
+		if (filter == nullptr) {
 
 			Inkscape::XML::Node * newfilterroot = xmldoc->createElement("svg:filter");
 			merge_filters(newfilterroot, filterdoc->root(), xmldoc);
@@ -159,8 +159,8 @@ void Filter::effect(Inkscape::Extension::Effect *module, Inkscape::UI::View::Vie
 			}
 
 			gchar * lfilter = g_strndup(filter + 5, strlen(filter) - 6);
-			Inkscape::XML::Node * filternode = NULL;
-			for (Inkscape::XML::Node * child = defsrepr->firstChild(); child != NULL; child = child->next()) {
+			Inkscape::XML::Node * filternode = nullptr;
+			for (Inkscape::XML::Node * child = defsrepr->firstChild(); child != nullptr; child = child->next()) {
 				if (!strcmp(lfilter, child->attribute("id"))) {
 					filternode = child;
 					break;
@@ -169,12 +169,12 @@ void Filter::effect(Inkscape::Extension::Effect *module, Inkscape::UI::View::Vie
 			g_free(lfilter);
 
 			// no filter
-			if (filternode == NULL) {
+			if (filternode == nullptr) {
 				g_warning("no assigned filter found!");
 				continue;
 			}
 
-			if (filternode->lastChild() == NULL) {
+			if (filternode->lastChild() == nullptr) {
                 // empty filter, we insert
                 merge_filters(filternode, filterdoc->root(), xmldoc);
 			} else {
diff --git a/src/extension/internal/filter/filter.h b/src/extension/internal/filter/filter.h
index ea4ae2302..3a5b8a811 100644
--- a/src/extension/internal/filter/filter.h
+++ b/src/extension/internal/filter/filter.h
@@ -37,7 +37,7 @@ protected:
 
 private:
 	Inkscape::XML::Document * get_filter (Inkscape::Extension::Extension * ext);
-	void merge_filters (Inkscape::XML::Node * to, Inkscape::XML::Node * from, Inkscape::XML::Document * doc, gchar const * srcGraphic = NULL, gchar const * srcGraphicAlpha = NULL);
+	void merge_filters (Inkscape::XML::Node * to, Inkscape::XML::Node * from, Inkscape::XML::Document * doc, gchar const * srcGraphic = nullptr, gchar const * srcGraphicAlpha = nullptr);
 
 public:
 	Filter();
diff --git a/src/extension/internal/filter/image.h b/src/extension/internal/filter/image.h
index 9cbe05e2f..592e41b9f 100644
--- a/src/extension/internal/filter/image.h
+++ b/src/extension/internal/filter/image.h
@@ -41,7 +41,7 @@ protected:
 
 public:
     EdgeDetect ( ) : Filter() { };
-    ~EdgeDetect ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~EdgeDetect ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -72,7 +72,7 @@ public:
 gchar const *
 EdgeDetect::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream matrix;
     std::ostringstream inverted;
diff --git a/src/extension/internal/filter/morphology.h b/src/extension/internal/filter/morphology.h
index 025cca8fe..905e71e67 100644
--- a/src/extension/internal/filter/morphology.h
+++ b/src/extension/internal/filter/morphology.h
@@ -50,7 +50,7 @@ protected:
 
 public:
     Crosssmooth ( ) : Filter() { };
-    ~Crosssmooth ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Crosssmooth ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -86,7 +86,7 @@ public:
 gchar const *
 Crosssmooth::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream type;
     std::ostringstream width;
@@ -158,7 +158,7 @@ protected:
 
 public:
     Outline ( ) : Filter() { };
-    ~Outline ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Outline ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -213,7 +213,7 @@ public:
 gchar const *
 Outline::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream width1;
     std::ostringstream dilat1;
diff --git a/src/extension/internal/filter/overlays.h b/src/extension/internal/filter/overlays.h
index a0436e2ad..e0f78be9c 100644
--- a/src/extension/internal/filter/overlays.h
+++ b/src/extension/internal/filter/overlays.h
@@ -48,7 +48,7 @@ protected:
 
 public:
     NoiseFill ( ) : Filter() { };
-    ~NoiseFill ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~NoiseFill ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -90,7 +90,7 @@ public:
 gchar const *
 NoiseFill::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream type;
     std::ostringstream hfreq;
diff --git a/src/extension/internal/filter/paint.h b/src/extension/internal/filter/paint.h
index 653008fc6..aae71fcf3 100644
--- a/src/extension/internal/filter/paint.h
+++ b/src/extension/internal/filter/paint.h
@@ -63,7 +63,7 @@ protected:
 
 public:
     Chromolitho ( ) : Filter() { };
-    ~Chromolitho ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Chromolitho ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -122,7 +122,7 @@ public:
 gchar const *
 Chromolitho::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
     
     std::ostringstream b1in;
     std::ostringstream b2in;
@@ -224,7 +224,7 @@ protected:
 
 public:
     CrossEngraving ( ) : Filter() { };
-    ~CrossEngraving ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~CrossEngraving ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -253,7 +253,7 @@ public:
 gchar const *
 CrossEngraving::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream clean;
     std::ostringstream dilat;
@@ -323,7 +323,7 @@ protected:
 
 public:
     Drawing ( ) : Filter() { };
-    ~Drawing ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Drawing ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -372,7 +372,7 @@ public:
 gchar const *
 Drawing::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream simply;
     std::ostringstream clean;
@@ -486,7 +486,7 @@ protected:
 
 public:
     Electrize ( ) : Filter() { };
-    ~Electrize ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Electrize ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -516,7 +516,7 @@ public:
 gchar const *
 Electrize::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream blur;
     std::ostringstream type;
@@ -576,7 +576,7 @@ protected:
 
 public:
     NeonDraw ( ) : Filter() { };
-    ~NeonDraw ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~NeonDraw ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -611,7 +611,7 @@ public:
 gchar const *
 NeonDraw::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream blend;
     std::ostringstream simply;
@@ -679,7 +679,7 @@ protected:
 
 public:
     PointEngraving ( ) : Filter() { };
-    ~PointEngraving ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~PointEngraving ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -735,7 +735,7 @@ public:
 gchar const *
 PointEngraving::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
   
     std::ostringstream type;
     std::ostringstream hfreq;
@@ -842,7 +842,7 @@ protected:
 
 public:
     Posterize ( ) : Filter() { };
-    ~Posterize ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Posterize ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -886,7 +886,7 @@ public:
 gchar const *
 Posterize::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream table;
     std::ostringstream blendmode;
@@ -965,7 +965,7 @@ protected:
 
 public:
     PosterizeBasic ( ) : Filter() { };
-    ~PosterizeBasic ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~PosterizeBasic ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -990,7 +990,7 @@ public:
 gchar const *
 PosterizeBasic::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream blur;
     std::ostringstream transf;
diff --git a/src/extension/internal/filter/protrusions.h b/src/extension/internal/filter/protrusions.h
index c4cd2a688..0abac91e7 100644
--- a/src/extension/internal/filter/protrusions.h
+++ b/src/extension/internal/filter/protrusions.h
@@ -39,7 +39,7 @@ protected:
 
 public:
 	Snow ( ) : Filter() { };
-	~Snow ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+	~Snow ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
 public:
 	static void init (void) {
@@ -65,7 +65,7 @@ public:
 gchar const *
 Snow::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-	if (_filter != NULL) g_free((void *)_filter);
+	if (_filter != nullptr) g_free((void *)_filter);
 
         std::ostringstream drift;
         drift << ext->get_param_float("drift");
diff --git a/src/extension/internal/filter/shadows.h b/src/extension/internal/filter/shadows.h
index cca34e2a2..19cfdaba7 100644
--- a/src/extension/internal/filter/shadows.h
+++ b/src/extension/internal/filter/shadows.h
@@ -49,7 +49,7 @@ protected:
 
 public:
     ColorizableDropShadow ( ) : Filter() { };
-    ~ColorizableDropShadow ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~ColorizableDropShadow ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -91,7 +91,7 @@ public:
 gchar const *
 ColorizableDropShadow::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream blur;
     std::ostringstream a;
diff --git a/src/extension/internal/filter/textures.h b/src/extension/internal/filter/textures.h
index 39b1789b3..3340643a5 100644
--- a/src/extension/internal/filter/textures.h
+++ b/src/extension/internal/filter/textures.h
@@ -53,7 +53,7 @@ protected:
 
 public:
 	InkBlot ( ) : Filter() { };
-	~InkBlot ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+	~InkBlot ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
 public:
 	static void init (void) {
@@ -101,7 +101,7 @@ public:
 gchar const *
 InkBlot::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-	if (_filter != NULL) g_free((void *)_filter);
+	if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream type;
     std::ostringstream freq;
diff --git a/src/extension/internal/filter/transparency.h b/src/extension/internal/filter/transparency.h
index b3498a638..1239c1fac 100644
--- a/src/extension/internal/filter/transparency.h
+++ b/src/extension/internal/filter/transparency.h
@@ -45,7 +45,7 @@ protected:
 
 public:
     Blend ( ) : Filter() { };
-    ~Blend ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Blend ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -80,7 +80,7 @@ public:
 gchar const *
 Blend::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream source;
     std::ostringstream mode;
@@ -122,7 +122,7 @@ protected:
 
 public:
     ChannelTransparency ( ) : Filter() { };
-    ~ChannelTransparency ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~ChannelTransparency ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
     
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -150,7 +150,7 @@ public:
 gchar const *
 ChannelTransparency::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream red;
     std::ostringstream green;
@@ -197,7 +197,7 @@ protected:
 
 public:
     LightEraser ( ) : Filter() { };
-    ~LightEraser ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~LightEraser ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
     
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -224,7 +224,7 @@ public:
 gchar const *
 LightEraser::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream expand;
     std::ostringstream erode;
@@ -271,7 +271,7 @@ protected:
 
 public:
     Opacity ( ) : Filter() { };
-    ~Opacity ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Opacity ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
     
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -297,7 +297,7 @@ public:
 gchar const *
 Opacity::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream matrix;
     std::ostringstream opacity;
@@ -333,7 +333,7 @@ protected:
 
 public:
     Silhouette ( ) : Filter() { };
-    ~Silhouette ( ) override { if (_filter != NULL) g_free((void *)_filter); return; }
+    ~Silhouette ( ) override { if (_filter != nullptr) g_free((void *)_filter); return; }
 
     static void init (void) {
         Inkscape::Extension::build_from_mem(
@@ -360,7 +360,7 @@ public:
 gchar const *
 Silhouette::get_filter_text (Inkscape::Extension::Extension * ext)
 {
-    if (_filter != NULL) g_free((void *)_filter);
+    if (_filter != nullptr) g_free((void *)_filter);
 
     std::ostringstream a;
     std::ostringstream r;
diff --git a/src/extension/internal/gdkpixbuf-input.cpp b/src/extension/internal/gdkpixbuf-input.cpp
index efac1a02e..ba90c747e 100644
--- a/src/extension/internal/gdkpixbuf-input.cpp
+++ b/src/extension/internal/gdkpixbuf-input.cpp
@@ -64,14 +64,14 @@ GdkpixbufInput::open(Inkscape::Extension::Input *mod, char const *uri)
     }
     bool embed = ( link.compare( "embed" ) == 0 );
  
-    SPDocument *doc = NULL;
+    SPDocument *doc = nullptr;
     std::unique_ptr<Inkscape::Pixbuf> pb(Inkscape::Pixbuf::create_from_file(uri));
 
     // TODO: the pixbuf is created again from the base64-encoded attribute in SPImage.
     // Find a way to create the pixbuf only once.
 
     if (pb) {
-        doc = SPDocument::createNewDoc(NULL, TRUE, TRUE);
+        doc = SPDocument::createNewDoc(nullptr, TRUE, TRUE);
         bool saved = DocumentUndo::getUndoSensitive(doc);
         DocumentUndo::setUndoSensitive(doc, false); // no need to undo in this temporary document
 
@@ -79,7 +79,7 @@ GdkpixbufInput::open(Inkscape::Extension::Input *mod, char const *uri)
         double height = pb->height();
         double defaultxdpi = prefs->getDouble("/dialogs/import/defaultxdpi/value", Inkscape::Util::Quantity::convert(1, "in", "px"));
         //bool forcexdpi = prefs->getBool("/dialogs/import/forcexdpi");
-        ImageResolution *ir = 0;
+        ImageResolution *ir = nullptr;
         double xscale = 1;
         double yscale = 1;
 
@@ -126,7 +126,7 @@ GdkpixbufInput::open(Inkscape::Extension::Input *mod, char const *uri)
             sp_embed_image(image_node, pb.get());
         } else {
             // convert filename to uri
-            gchar* _uri = g_filename_to_uri(uri, NULL, NULL);
+            gchar* _uri = g_filename_to_uri(uri, nullptr, nullptr);
             if(_uri) {
                 image_node->setAttribute("xlink:href", _uri);
                 g_free(_uri);
@@ -174,8 +174,8 @@ GdkpixbufInput::init(void)
         gchar **extensions =  gdk_pixbuf_format_get_extensions(pixformat);
         gchar **mimetypes =   gdk_pixbuf_format_get_mime_types(pixformat);
 
-        for (int i = 0; extensions[i] != NULL; i++) {
-        for (int j = 0; mimetypes[j] != NULL; j++) {
+        for (int i = 0; extensions[i] != nullptr; i++) {
+        for (int j = 0; mimetypes[j] != nullptr; j++) {
 
             /* thanks but no thanks, we'll handle SVG extensions... */
             if (strcmp(extensions[i], "svg") == 0) {
diff --git a/src/extension/internal/gimpgrad.cpp b/src/extension/internal/gimpgrad.cpp
index e6a429d34..1323ca7bc 100644
--- a/src/extension/internal/gimpgrad.cpp
+++ b/src/extension/internal/gimpgrad.cpp
@@ -133,13 +133,13 @@ GimpGrad::open (Inkscape::Extension::Input */*module*/, gchar const *filename)
 {
     Inkscape::IO::dump_fopen_call(filename, "I");
     FILE *gradient = Inkscape::IO::fopen_utf8name(filename, "r");
-    if (gradient == NULL) {
-        return NULL;
+    if (gradient == nullptr) {
+        return nullptr;
     }
 
     {
         char tempstr[1024];
-        if (fgets(tempstr, 1024, gradient) == 0) {
+        if (fgets(tempstr, 1024, gradient) == nullptr) {
             // std::cout << "Seems that the read failed" << std::endl;
             goto error;
         }
@@ -149,7 +149,7 @@ GimpGrad::open (Inkscape::Extension::Input */*module*/, gchar const *filename)
         }
 
         /* Name field. */
-        if (fgets(tempstr, 1024, gradient) == 0) {
+        if (fgets(tempstr, 1024, gradient) == nullptr) {
             // std::cout << "Seems that the second read failed" << std::endl;
             goto error;
         }
@@ -157,18 +157,18 @@ GimpGrad::open (Inkscape::Extension::Input */*module*/, gchar const *filename)
             goto error;
         }
         /* Handle very long names.  (And also handle nul bytes gracefully: don't use strlen.) */
-        while (memchr(tempstr, '\n', sizeof(tempstr) - 1) == NULL) {
-            if (fgets(tempstr, sizeof(tempstr), gradient) == 0) {
+        while (memchr(tempstr, '\n', sizeof(tempstr) - 1) == nullptr) {
+            if (fgets(tempstr, sizeof(tempstr), gradient) == nullptr) {
                 goto error;
             }
         }
 
         /* n. segments */
-        if (fgets(tempstr, 1024, gradient) == 0) {
+        if (fgets(tempstr, 1024, gradient) == nullptr) {
             // std::cout << "Seems that the third read failed" << std::endl;
             goto error;
         }
-        char *endptr = NULL;
+        char *endptr = nullptr;
         long const n_segs = strtol(tempstr, &endptr, 10);
         if ((*endptr != '\n')
             || n_segs < 1) {
@@ -183,11 +183,11 @@ GimpGrad::open (Inkscape::Extension::Input */*module*/, gchar const *filename)
         Glib::ustring outsvg("<svg><defs><linearGradient>\n");
         long n_segs_found = 0;
         double prev_right = 0.0;
-        while (fgets(tempstr, 1024, gradient) != 0) {
+        while (fgets(tempstr, 1024, gradient) != nullptr) {
             double dbls[3 + 4 + 4];
             gchar *p = tempstr;
             for (unsigned i = 0; i < G_N_ELEMENTS(dbls); ++i) {
-                gchar *end = NULL;
+                gchar *end = nullptr;
                 double const xi = g_ascii_strtod(p, &end);
                 if (!end || end == p || !g_ascii_isspace(*end)) {
                     goto error;
@@ -260,7 +260,7 @@ GimpGrad::open (Inkscape::Extension::Input */*module*/, gchar const *filename)
 
 error:
     fclose(gradient);
-    return NULL;
+    return nullptr;
 }
 
 #include "clear-n_.h"
diff --git a/src/extension/internal/grid.cpp b/src/extension/internal/grid.cpp
index c7ebf2494..5347eaa86 100644
--- a/src/extension/internal/grid.cpp
+++ b/src/extension/internal/grid.cpp
@@ -180,7 +180,7 @@ Grid::prefs_effect(Inkscape::Extension::Effect *module, Inkscape::UI::View::View
     SPDocument * current_document = view->doc();
 
     auto selected = ((SPDesktop *) view)->getSelection()->items();
-    Inkscape::XML::Node * first_select = NULL;
+    Inkscape::XML::Node * first_select = nullptr;
     if (!selected.empty()) {
         first_select = selected.front()->getRepr();
     }
diff --git a/src/extension/internal/image-resolution.cpp b/src/extension/internal/image-resolution.cpp
index 558276999..e5b1e4619 100644
--- a/src/extension/internal/image-resolution.cpp
+++ b/src/extension/internal/image-resolution.cpp
@@ -110,18 +110,18 @@ void ImageResolution::readpng(char const *fn) {
         return;
     }
 
-    png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
+    png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
     if (!png_ptr) 
         return;
     
     png_infop info_ptr = png_create_info_struct(png_ptr);
     if (!info_ptr) {
-        png_destroy_read_struct(&png_ptr, 0, 0);
+        png_destroy_read_struct(&png_ptr, nullptr, nullptr);
         return;
     }
     
     if (setjmp(png_jmpbuf(png_ptr))) {
-        png_destroy_read_struct(&png_ptr, &info_ptr, 0);
+        png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
         fclose(fp);
         return;
     }
@@ -153,7 +153,7 @@ void ImageResolution::readpng(char const *fn) {
     }
 #endif
 
-    png_destroy_read_struct(&png_ptr, &info_ptr, 0);
+    png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
     fclose(fp);
 
     if (ok_) {
diff --git a/src/extension/internal/javafx-out.cpp b/src/extension/internal/javafx-out.cpp
index d4666fcee..5646eeefd 100644
--- a/src/extension/internal/javafx-out.cpp
+++ b/src/extension/internal/javafx-out.cpp
@@ -65,11 +65,11 @@ namespace Internal
 static void err(const char *fmt, ...)
 {
     va_list args;
-    g_log(NULL,  G_LOG_LEVEL_WARNING, "javafx-out err: ");
+    g_log(nullptr,  G_LOG_LEVEL_WARNING, "javafx-out err: ");
     va_start(args, fmt);
-    g_logv(NULL, G_LOG_LEVEL_WARNING, fmt, args);
+    g_logv(nullptr, G_LOG_LEVEL_WARNING, fmt, args);
     va_end(args);
-    g_log(NULL,  G_LOG_LEVEL_WARNING, "\n");
+    g_log(nullptr,  G_LOG_LEVEL_WARNING, "\n");
 }
 
 
@@ -222,7 +222,7 @@ void JavaFXOutput::out(const char *fmt, ...)
  */
 bool JavaFXOutput::doHeader()
 {
-    time_t tim = time(NULL);
+    time_t tim = time(nullptr);
     out("/*###################################################################\n");
     out("### This JavaFX document was generated by Inkscape\n");
     out("### http://www.inkscape.org\n");
diff --git a/src/extension/internal/latex-pstricks-out.cpp b/src/extension/internal/latex-pstricks-out.cpp
index 0581f8edd..e1da0bab6 100644
--- a/src/extension/internal/latex-pstricks-out.cpp
+++ b/src/extension/internal/latex-pstricks-out.cpp
@@ -40,7 +40,7 @@ LatexOutput::~LatexOutput (void) //The destructor
 
 bool LatexOutput::check(Inkscape::Extension::Extension * /*module*/)
 {
-    bool result = Inkscape::Extension::db.get("org.inkscape.print.latex") != NULL;
+    bool result = Inkscape::Extension::db.get("org.inkscape.print.latex") != nullptr;
     return result;
 }
 
@@ -69,8 +69,8 @@ void LatexOutput::save(Inkscape::Extension::Output * /*mod2*/, SPDocument *doc,
     mod->finish();
     // Release things
     (mod->base)->invoke_hide(mod->dkey);
-    mod->base = NULL;
-    mod->root = NULL; // should have been deleted by invoke_hide
+    mod->base = nullptr;
+    mod->root = nullptr; // should have been deleted by invoke_hide
     // end
 
     mod->set_param_string("destination", oldoutput);
diff --git a/src/extension/internal/latex-pstricks.cpp b/src/extension/internal/latex-pstricks.cpp
index 83100d11e..aa90c4f59 100644
--- a/src/extension/internal/latex-pstricks.cpp
+++ b/src/extension/internal/latex-pstricks.cpp
@@ -39,7 +39,7 @@ namespace Internal {
 PrintLatex::PrintLatex (void):
     _width(0),
     _height(0),
-    _stream(NULL)
+    _stream(nullptr)
 {
 }
 
@@ -63,11 +63,11 @@ unsigned int PrintLatex::begin (Inkscape::Extension::Print *mod, SPDocument *doc
 {
     Inkscape::SVGOStringStream os;
     int res;
-    FILE *osf = NULL;
-    const gchar * fn = NULL;
+    FILE *osf = nullptr;
+    const gchar * fn = nullptr;
     gsize bytesRead = 0;
     gsize bytesWritten = 0;
-    GError* error = NULL;
+    GError* error = nullptr;
 
     os.setf(std::ios::fixed);
     fn = mod->get_param_string("destination");
@@ -80,7 +80,7 @@ unsigned int PrintLatex::begin (Inkscape::Extension::Print *mod, SPDocument *doc
      * the callers (sp_print_document_to_file, "ret = mod->begin(doc)") wrongly ignores the
      * return code.
      */
-    if (fn != NULL) {
+    if (fn != nullptr) {
         while (isspace(*fn)) fn += 1;
         Inkscape::IO::dump_fopen_call(fn, "K");
         osf = Inkscape::IO::fopen_utf8name(fn, "w+");
@@ -110,7 +110,7 @@ unsigned int PrintLatex::begin (Inkscape::Extension::Print *mod, SPDocument *doc
         g_print("Printing failed\n");
         /* fixme: should use pclose() for pipes */
         fclose(_stream);
-        _stream = NULL;
+        _stream = nullptr;
         fflush(stdout);
         return 0;
     }
@@ -144,7 +144,7 @@ unsigned int PrintLatex::finish(Inkscape::Extension::Print * /*mod*/)
         fflush(_stream);
 
         fclose(_stream);
-        _stream = NULL;
+        _stream = nullptr;
     }
     return 0;
 }
diff --git a/src/extension/internal/latex-text-renderer.cpp b/src/extension/internal/latex-text-renderer.cpp
index 85426e376..c61a95922 100644
--- a/src/extension/internal/latex-text-renderer.cpp
+++ b/src/extension/internal/latex-text-renderer.cpp
@@ -64,7 +64,7 @@ latex_render_document_text_to_file( SPDocument *doc, gchar const *filename,
 {
     doc->ensureUpToDate();
 
-    SPItem *base = NULL;
+    SPItem *base = nullptr;
 
     bool pageBoundingBox = true;
     if (exportId && strcmp(exportId, "")) {
@@ -102,8 +102,8 @@ latex_render_document_text_to_file( SPDocument *doc, gchar const *filename,
 }
 
 LaTeXTextRenderer::LaTeXTextRenderer(bool pdflatex)
-  : _stream(NULL),
-    _filename(NULL),
+  : _stream(nullptr),
+    _filename(nullptr),
     _pdflatex(pdflatex),
     _omittext_state(EMPTY),
     _omittext_page(1)
@@ -136,7 +136,7 @@ LaTeXTextRenderer::~LaTeXTextRenderer(void)
  */
 bool
 LaTeXTextRenderer::setTargetFile(gchar const *filename) {
-    if (filename != NULL) {
+    if (filename != nullptr) {
         while (isspace(*filename)) filename += 1;
 
         _filename = g_path_get_basename(filename);
@@ -171,7 +171,7 @@ LaTeXTextRenderer::setTargetFile(gchar const *filename) {
         g_print("Output to LaTeX file failed\n");
         /* fixme: should use pclose() for pipes */
         fclose(_stream);
-        _stream = NULL;
+        _stream = nullptr;
         fflush(stdout);
         return false;
     }
@@ -281,8 +281,8 @@ void LaTeXTextRenderer::sp_text_render(SPText *textobj)
     // get position and alignment
     // Align vertically on the baseline of the font (retrieved from the anchor point)
     // Align horizontally on anchorpoint
-    gchar const *alignment = NULL;
-    gchar const *aligntabular = NULL;
+    gchar const *alignment = nullptr;
+    gchar const *aligntabular = nullptr;
     switch (style->text_anchor.computed) {
     case SP_CSS_TEXT_ANCHOR_START:
         alignment = "[lt]";
@@ -437,7 +437,7 @@ Flowing in rectangle is possible, not in arb shape.
 
     SPStyle *style = flowtext->style;
 
-    SPItem *frame_item = flowtext->get_frame(NULL);
+    SPItem *frame_item = flowtext->get_frame(nullptr);
     SPRect *frame = dynamic_cast<SPRect *>(frame_item);
     if (!frame_item || !frame) {
         g_warning("LaTeX export: non-rectangular flowed text shapes are not supported, skipping text.");
diff --git a/src/extension/internal/metafile-inout.cpp b/src/extension/internal/metafile-inout.cpp
index ae79c8a8a..b90af9529 100644
--- a/src/extension/internal/metafile-inout.cpp
+++ b/src/extension/internal/metafile-inout.cpp
@@ -93,32 +93,32 @@ Metafile::my_png_write_data(png_structp png_ptr, png_bytep data, png_size_t leng
 void Metafile::toPNG(PMEMPNG accum, int width, int height, const char *px){
     bitmap_t bmStore;
     bitmap_t *bitmap = &bmStore;
-    accum->buffer=NULL;  // PNG constructed in memory will end up here, caller must free().
+    accum->buffer=nullptr;  // PNG constructed in memory will end up here, caller must free().
     accum->size=0;
     bitmap->pixels=(pixel_t *)px;
     bitmap->width  = width;
     bitmap->height = height;
 
-    png_structp png_ptr = NULL;
-    png_infop info_ptr = NULL;
+    png_structp png_ptr = nullptr;
+    png_infop info_ptr = nullptr;
     size_t x, y;
-    png_byte ** row_pointers = NULL;
+    png_byte ** row_pointers = nullptr;
     /*  The following number is set by trial and error only. I cannot
         see where it it is documented in the libpng manual.
     */
     int pixel_size = 3;
     int depth = 8;
 
-    png_ptr = png_create_write_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
-    if (png_ptr == NULL){
-        accum->buffer=NULL;
+    png_ptr = png_create_write_struct (PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
+    if (png_ptr == nullptr){
+        accum->buffer=nullptr;
         return;
     }
 
     info_ptr = png_create_info_struct (png_ptr);
-    if (info_ptr == NULL){
+    if (info_ptr == nullptr){
         png_destroy_write_struct (&png_ptr, &info_ptr);
-        accum->buffer=NULL;
+        accum->buffer=nullptr;
         return;
     }
 
@@ -126,7 +126,7 @@ void Metafile::toPNG(PMEMPNG accum, int width, int height, const char *px){
 
     if (setjmp (png_jmpbuf (png_ptr))) {
         png_destroy_write_struct (&png_ptr, &info_ptr);
-        accum->buffer=NULL;
+        accum->buffer=nullptr;
         return;
     }
 
@@ -163,9 +163,9 @@ void Metafile::toPNG(PMEMPNG accum, int width, int height, const char *px){
 
     png_set_rows (png_ptr, info_ptr, row_pointers);
 
-    png_set_write_fn(png_ptr, accum, my_png_write_data, NULL);
+    png_set_write_fn(png_ptr, accum, my_png_write_data, nullptr);
 
-    png_write_png (png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
+    png_write_png (png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, nullptr);
 
     for (y = 0; y < bitmap->height; y++) {
         png_free (png_ptr, row_pointers[y]);
@@ -186,7 +186,7 @@ void Metafile::setViewBoxIfMissing(SPDocument *doc) {
         doc->ensureUpToDate();
         
         // Set document unit
-        Inkscape::XML::Node *repr = sp_document_namedview(doc, 0)->getRepr();
+        Inkscape::XML::Node *repr = sp_document_namedview(doc, nullptr)->getRepr();
         Inkscape::SVGOStringStream os;
         Inkscape::Util::Unit const* doc_unit = doc->getWidth().unit;
         os << doc_unit->abbr;
diff --git a/src/extension/internal/metafile-print.cpp b/src/extension/internal/metafile-print.cpp
index fb44f8499..4bb8eae32 100644
--- a/src/extension/internal/metafile-print.cpp
+++ b/src/extension/internal/metafile-print.cpp
@@ -89,7 +89,7 @@ bool PrintMetafile::_load_ppt_fontfix_data()   //this is not called by any other
         return (ppt_fontfix_available = false);
     }
 
-    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, NULL));
+    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, nullptr));
     setlocale(LC_NUMERIC, "C");
 
     std::string instr;
@@ -271,7 +271,7 @@ void PrintMetafile::hatch_classify(char *name, int *hatchType, U_COLORREF *hatch
 void PrintMetafile::brush_classify(SPObject *parent, int depth, Inkscape::Pixbuf **epixbuf, int *hatchType, U_COLORREF *hatchColor, U_COLORREF *bkColor)
 {
     if (depth == 0) {
-        *epixbuf    = NULL;
+        *epixbuf    = nullptr;
         *hatchType  = -1;
         *hatchColor = U_RGB(0, 0, 0);
         *bkColor    = U_RGB(255, 255, 255);
@@ -279,7 +279,7 @@ void PrintMetafile::brush_classify(SPObject *parent, int depth, Inkscape::Pixbuf
     depth++;
     // first look along the pattern chain, if there is one
     if (SP_IS_PATTERN(parent)) {
-        for (SPPattern *pat_i = SP_PATTERN(parent); pat_i != NULL; pat_i = pat_i->ref ? pat_i->ref->getObject() : NULL) {
+        for (SPPattern *pat_i = SP_PATTERN(parent); pat_i != nullptr; pat_i = pat_i->ref ? pat_i->ref->getObject() : nullptr) {
             if (SP_IS_IMAGE(pat_i)) {
                 *epixbuf = ((SPImage *)pat_i)->pixbuf;
                 return;
diff --git a/src/extension/internal/odf.cpp b/src/extension/internal/odf.cpp
index 42c2bbae3..2c25ea1f4 100644
--- a/src/extension/internal/odf.cpp
+++ b/src/extension/internal/odf.cpp
@@ -218,7 +218,7 @@ private:
     virtual void init()
         {
         badval = 0.0;
-        d      = NULL;
+        d      = nullptr;
         rows   = 0;
         cols   = 0;
         size   = 0;
@@ -229,7 +229,7 @@ private:
         if (d)
             {
             delete[] d;
-            d = 0;
+            d = nullptr;
             }
         rows = other.rows;
         cols = other.cols;
@@ -289,7 +289,7 @@ public:
     SingularValueDecomposition (const SVDMatrix &mat) :
         A (mat),
         U (),
-        s (NULL),
+        s (nullptr),
         s_size (0),
         V ()
         {
@@ -1010,7 +1010,7 @@ static void gatherText(Inkscape::XML::Node *node, Glib::ustring &buf)
         }
 
     for (Inkscape::XML::Node *child = node->firstChild() ;
-                child != NULL; child = child->next())
+                child != nullptr; child = child->next())
         {
         gatherText(child, buf);
         }
@@ -1466,7 +1466,7 @@ bool OdfOutput::processGradient(SPItem *item,
     //## Gradient
     SPGradient *gradient = SP_GRADIENT((checkFillGradient?(SP_STYLE_FILL_SERVER(style)) :(SP_STYLE_STROKE_SERVER(style))));
 
-    if (gradient == NULL)
+    if (gradient == nullptr)
     {
         return false;
     }
@@ -1644,7 +1644,7 @@ bool OdfOutput::writeTree(Writer &couts, Writer &souts,
     analyzeTransform(tf, rotate, xskew, yskew, xscale, yscale);
 
     //# Do our stuff
-    SPCurve *curve = NULL;
+    SPCurve *curve = nullptr;
 
     if (nodeName == "svg" || nodeName == "svg:svg")
     {
@@ -2038,7 +2038,7 @@ bool OdfOutput::writeContent(ZipFile &zf, Inkscape::XML::Node *node)
 
     //# Descend into the tree, doing all of our conversions
     //# to both files at the same time
-    char *oldlocale = g_strdup (setlocale (LC_NUMERIC, NULL));
+    char *oldlocale = g_strdup (setlocale (LC_NUMERIC, nullptr));
     setlocale (LC_NUMERIC, "C");
     if (!writeTree(couts, souts, node))
     {
diff --git a/src/extension/internal/pdfinput/pdf-input.cpp b/src/extension/internal/pdfinput/pdf-input.cpp
index 552051eed..d078b5a9b 100644
--- a/src/extension/internal/pdfinput/pdf-input.cpp
+++ b/src/extension/internal/pdfinput/pdf-input.cpp
@@ -357,7 +357,7 @@ PdfImportDialog::PdfImportDialog(PDFDoc *doc, const gchar */*uri*/)
     _preview_height = 300;
 
     // Init preview
-    _thumb_data = NULL;
+    _thumb_data = nullptr;
     _pageNumberSpin_adj->set_value(1.0);
     _current_page = 1;
     _setPreviewPage(_current_page);
@@ -594,7 +594,7 @@ void PdfImportDialog::_setPreviewPage(int page) {
     if (!_render_thumb) {
         if (_thumb_data) {
             gfree(_thumb_data);
-            _thumb_data = NULL;
+            _thumb_data = nullptr;
         }
         if (!_previewed_page->loadThumb(&_thumb_data,
              &_thumb_width, &_thumb_height, &_thumb_rowstride)) {
@@ -714,7 +714,7 @@ PdfInput::open(::Inkscape::Extension::Input * /*mod*/, const gchar * uri) {
     // poppler does not use glib g_open. So on win32 we must use unicode call. code was copied from
     // glib gstdio.c
     GooString *filename_goo = new GooString(uri);
-    PDFDoc *pdf_doc = new PDFDoc(filename_goo, NULL, NULL, NULL);   // TODO: Could ask for password
+    PDFDoc *pdf_doc = new PDFDoc(filename_goo, nullptr, nullptr, nullptr);   // TODO: Could ask for password
     //delete filename_goo;
 #else
     wchar_t *wfilename = reinterpret_cast<wchar_t*>(g_utf8_to_utf16 (uri, -1, NULL, NULL, NULL));
@@ -754,17 +754,17 @@ PdfInput::open(::Inkscape::Extension::Input * /*mod*/, const gchar * uri) {
             g_message("Failed to load document from data (error %d)", error);
         }
 
-        return NULL;
+        return nullptr;
     }
 
-    PdfImportDialog *dlg = NULL;
+    PdfImportDialog *dlg = nullptr;
     if (INKSCAPE.use_gui()) {
         dlg = new PdfImportDialog(pdf_doc, uri);
         if (!dlg->showDialog()) {
             _cancelled = true;
             delete dlg;
             delete pdf_doc;
-            return NULL;
+            return nullptr;
         }
     }
 
@@ -779,12 +779,12 @@ PdfInput::open(::Inkscape::Extension::Input * /*mod*/, const gchar * uri) {
 #endif
     }
 
-    SPDocument *doc = NULL;
+    SPDocument *doc = nullptr;
     bool saved = false;
     if(!is_importvia_poppler)
     {
         // native importer
-        doc = SPDocument::createNewDoc(NULL, TRUE, TRUE);
+        doc = SPDocument::createNewDoc(nullptr, TRUE, TRUE);
         saved = DocumentUndo::getUndoSensitive(doc);
         DocumentUndo::setUndoSensitive(doc, false); // No need to undo in this temporary document
 
@@ -802,7 +802,7 @@ PdfInput::open(::Inkscape::Extension::Input * /*mod*/, const gchar * uri) {
             dlg->getImportSettings(prefs);
 
         // Apply crop settings
-        PDFRectangle *clipToBox = NULL;
+        PDFRectangle *clipToBox = nullptr;
         double crop_setting;
         sp_repr_get_double(prefs, "cropTo", &crop_setting);
 
diff --git a/src/extension/internal/pdfinput/pdf-parser.cpp b/src/extension/internal/pdfinput/pdf-parser.cpp
index caaeca18e..fbcb708fe 100644
--- a/src/extension/internal/pdfinput/pdf-parser.cpp
+++ b/src/extension/internal/pdfinput/pdf-parser.cpp
@@ -264,13 +264,13 @@ GfxPatch blankPatch()
 class ClipHistoryEntry {
 public:
 
-    ClipHistoryEntry(GfxPath *clipPath = NULL, GfxClipType clipType = clipNormal);
+    ClipHistoryEntry(GfxPath *clipPath = nullptr, GfxClipType clipType = clipNormal);
     virtual ~ClipHistoryEntry();
 
     // Manipulate clip path stack
     ClipHistoryEntry *save();
     ClipHistoryEntry *restore();
-    GBool hasSaves() { return saved != NULL; }
+    GBool hasSaves() { return saved != nullptr; }
     void setClip(GfxPath *newClipPath, GfxClipType newClipType = clipNormal);
     GfxPath *getClipPath() { return clipPath; }
     GfxClipType getClipType() { return clipType; }
@@ -300,18 +300,18 @@ PdfParser::PdfParser(XRef *xrefA,
     builder(builderA),
     subPage(gFalse),
     printCommands(false),
-    res(new GfxResources(xref, resDict, NULL)), // start the resource stack
+    res(new GfxResources(xref, resDict, nullptr)), // start the resource stack
     state(new GfxState(72.0, 72.0, box, rotate, gTrue)),
     fontChanged(gFalse),
     clip(clipNone),
     ignoreUndef(0),
     baseMatrix(),
     formDepth(0),
-    parser(NULL),
+    parser(nullptr),
     colorDeltas(),
     maxDepths(),
     clipHistory(new ClipHistoryEntry()),
-    operatorHistory(NULL)
+    operatorHistory(nullptr)
 {
   setDefaultApproximationPrecision();
   builder->setDocumentSize(Inkscape::Util::Quantity::convert(state->getPageWidth(), "pt", "px"),
@@ -357,18 +357,18 @@ PdfParser::PdfParser(XRef *xrefA,
     builder(builderA),
     subPage(gTrue),
     printCommands(false),
-    res(new GfxResources(xref, resDict, NULL)), // start the resource stack
+    res(new GfxResources(xref, resDict, nullptr)), // start the resource stack
     state(new GfxState(72, 72, box, 0, gFalse)),
     fontChanged(gFalse),
     clip(clipNone),
     ignoreUndef(0),
     baseMatrix(),
     formDepth(0),
-    parser(NULL),
+    parser(nullptr),
     colorDeltas(),
     maxDepths(),
     clipHistory(new ClipHistoryEntry()),
-    operatorHistory(NULL)
+    operatorHistory(nullptr)
 {
   setDefaultApproximationPrecision();
   
@@ -399,12 +399,12 @@ PdfParser::~PdfParser() {
 
   if (state) {
     delete state;
-    state = NULL;
+    state = nullptr;
   }
 
   if (clipHistory) {
     delete clipHistory;
-    clipHistory = NULL;
+    clipHistory = nullptr;
   }
 }
 
@@ -436,7 +436,7 @@ void PdfParser::parse(Object *obj, GBool topLevel) {
   parser = new Parser(xref, new Lexer(xref, obj), gFalse);
   go(topLevel);
   delete parser;
-  parser = NULL;
+  parser = nullptr;
 }
 
 void PdfParser::go(GBool /*topLevel*/)
@@ -531,38 +531,38 @@ void PdfParser::pushOperator(const char *name)
 {
     OpHistoryEntry *newEntry = new OpHistoryEntry;
     newEntry->name = name;
-    newEntry->state = NULL;
-    newEntry->depth = (operatorHistory != NULL ? (operatorHistory->depth+1) : 0);
+    newEntry->state = nullptr;
+    newEntry->depth = (operatorHistory != nullptr ? (operatorHistory->depth+1) : 0);
     newEntry->next = operatorHistory;
     operatorHistory = newEntry;
 
     // Truncate list if needed
     if (operatorHistory->depth > maxOperatorHistoryDepth) {
         OpHistoryEntry *curr = operatorHistory;
-        OpHistoryEntry *prev = NULL;
-        while (curr && curr->next != NULL) {
+        OpHistoryEntry *prev = nullptr;
+        while (curr && curr->next != nullptr) {
             curr->depth--;
             prev = curr;
             curr = curr->next;
         }
         if (prev) {
-            if (curr->state != NULL)
+            if (curr->state != nullptr)
                 delete curr->state;
             delete curr;
-            prev->next = NULL;
+            prev->next = nullptr;
         }
     }
 }
 
 const char *PdfParser::getPreviousOperator(unsigned int look_back) {
-    OpHistoryEntry *prev = NULL;
-    if (operatorHistory != NULL && look_back > 0) {
+    OpHistoryEntry *prev = nullptr;
+    if (operatorHistory != nullptr && look_back > 0) {
         prev = operatorHistory->next;
-        while (--look_back > 0 && prev != NULL) {
+        while (--look_back > 0 && prev != nullptr) {
             prev = prev->next;
         }
     }
-    if (prev != NULL) {
+    if (prev != nullptr) {
         return prev->name;
     } else {
         return "";
@@ -635,7 +635,7 @@ PdfOperator* PdfParser::findOp(char *name) {
       a = b = m;
   }
   if (cmp != 0)
-    return NULL;
+    return nullptr;
   return &opTab[a];
 }
 
@@ -712,7 +712,7 @@ void PdfParser::opConcat(Object args[], int /*numArgs*/)
 // TODO not good that numArgs is ignored but args[] is used:
 void PdfParser::opSetDash(Object args[], int /*numArgs*/)
 {
-  double *dash = 0;
+  double *dash = nullptr;
 
   Array *a = args[0].getArray();
   int length = a->getLength();
@@ -770,7 +770,7 @@ void PdfParser::opSetLineWidth(Object args[], int /*numArgs*/)
 void PdfParser::opSetExtGState(Object args[], int /*numArgs*/)
 {
   Object obj1, obj2, obj3, obj4, obj5;
-  Function *funcs[4] = {0, 0, 0, 0};
+  Function *funcs[4] = {nullptr, nullptr, nullptr, nullptr};
   GfxColor backdropColor;
   GBool haveBackdropColor = gFalse;
   GBool alpha = gFalse;
@@ -876,7 +876,7 @@ void PdfParser::opSetExtGState(Object args[], int /*numArgs*/)
   }
   if (obj2.isName(const_cast<char*>("Default")) ||
       obj2.isName(const_cast<char*>("Identity"))) {
-    funcs[0] = funcs[1] = funcs[2] = funcs[3] = NULL;
+    funcs[0] = funcs[1] = funcs[2] = funcs[3] = nullptr;
     state->setTransfer(funcs);
   } else if (obj2.isArray() && obj2.arrayGetLength() == 4) {
     int pos = 4;
@@ -900,7 +900,7 @@ void PdfParser::opSetExtGState(Object args[], int /*numArgs*/)
     }
   } else if (obj2.isName() || obj2.isDict() || obj2.isStream()) {
     if ((funcs[0] = Function::parse(&obj2))) {
-      funcs[1] = funcs[2] = funcs[3] = NULL;
+      funcs[1] = funcs[2] = funcs[3] = nullptr;
       state->setTransfer(funcs);
     }
   } else if (!obj2.isNull()) {
@@ -931,7 +931,7 @@ void PdfParser::opSetExtGState(Object args[], int /*numArgs*/)
 #if !defined(POPPLER_NEW_OBJECT_API)
       obj3.free();
 #endif
-      funcs[0] = NULL;
+      funcs[0] = nullptr;
 #if defined(POPPLER_NEW_OBJECT_API)
       if (!((obj3 = obj2.dictLookup(const_cast<char*>("TR"))).isNull())) {
 #else
@@ -942,7 +942,7 @@ void PdfParser::opSetExtGState(Object args[], int /*numArgs*/)
 	    funcs[0]->getOutputSize() != 1) {
 	  error(errSyntaxError, getPos(), "Invalid transfer function in soft mask in ExtGState");
 	  delete funcs[0];
-	  funcs[0] = NULL;
+	  funcs[0] = nullptr;
 	}
       }
 #if defined(POPPLER_NEW_OBJECT_API)
@@ -976,7 +976,7 @@ void PdfParser::opSetExtGState(Object args[], int /*numArgs*/)
       if (obj2.dictLookup(const_cast<char*>("G"), &obj3)->isStream()) {
 	if (obj3.streamGetDict()->lookup(const_cast<char*>("Group"), &obj4)->isDict()) {
 #endif
-	  GfxColorSpace *blendingColorSpace = 0;
+	  GfxColorSpace *blendingColorSpace = nullptr;
 	  GBool isolated = gFalse;
 	  GBool knockout = gFalse;
 #if defined(POPPLER_NEW_OBJECT_API)
@@ -985,7 +985,7 @@ void PdfParser::opSetExtGState(Object args[], int /*numArgs*/)
 	  if (!obj4.dictLookup(const_cast<char*>("CS"), &obj5)->isNull()) {
 #endif
 #if defined(POPPLER_EVEN_NEWER_NEW_COLOR_SPACE_API)
-	    blendingColorSpace = GfxColorSpace::parse(NULL, &obj5, NULL, NULL);
+	    blendingColorSpace = GfxColorSpace::parse(nullptr, &obj5, nullptr, nullptr);
 #elif defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
 	    blendingColorSpace = GfxColorSpace::parse(&obj5, NULL, NULL);
 #else
@@ -1140,7 +1140,7 @@ void PdfParser::doSoftMask(Object *str, GBool alpha,
 #else
   dict->lookup(const_cast<char*>("Resources"), &obj1);
 #endif
-  resDict = obj1.isDict() ? obj1.getDict() : (Dict *)NULL;
+  resDict = obj1.isDict() ? obj1.getDict() : (Dict *)nullptr;
 
   // draw it
   ++formDepth;
@@ -1170,7 +1170,7 @@ void PdfParser::opSetFillGray(Object args[], int /*numArgs*/)
 {
   GfxColor color;
 
-  state->setFillPattern(NULL);
+  state->setFillPattern(nullptr);
   state->setFillColorSpace(new GfxDeviceGrayColorSpace());
   color.c[0] = dblToCol(args[0].getNum());
   state->setFillColor(&color);
@@ -1182,7 +1182,7 @@ void PdfParser::opSetStrokeGray(Object args[], int /*numArgs*/)
 {
   GfxColor color;
 
-  state->setStrokePattern(NULL);
+  state->setStrokePattern(nullptr);
   state->setStrokeColorSpace(new GfxDeviceGrayColorSpace());
   color.c[0] = dblToCol(args[0].getNum());
   state->setStrokeColor(&color);
@@ -1195,7 +1195,7 @@ void PdfParser::opSetFillCMYKColor(Object args[], int /*numArgs*/)
   GfxColor color;
   int i;
 
-  state->setFillPattern(NULL);
+  state->setFillPattern(nullptr);
   state->setFillColorSpace(new GfxDeviceCMYKColorSpace());
   for (i = 0; i < 4; ++i) {
     color.c[i] = dblToCol(args[i].getNum());
@@ -1209,7 +1209,7 @@ void PdfParser::opSetStrokeCMYKColor(Object args[], int /*numArgs*/)
 {
   GfxColor color;
 
-  state->setStrokePattern(NULL);
+  state->setStrokePattern(nullptr);
   state->setStrokeColorSpace(new GfxDeviceCMYKColorSpace());
   for (int i = 0; i < 4; ++i) {
     color.c[i] = dblToCol(args[i].getNum());
@@ -1223,7 +1223,7 @@ void PdfParser::opSetFillRGBColor(Object args[], int /*numArgs*/)
 {
   GfxColor color;
 
-  state->setFillPattern(NULL);
+  state->setFillPattern(nullptr);
   state->setFillColorSpace(new GfxDeviceRGBColorSpace());
   for (int i = 0; i < 3; ++i) {
     color.c[i] = dblToCol(args[i].getNum());
@@ -1236,7 +1236,7 @@ void PdfParser::opSetFillRGBColor(Object args[], int /*numArgs*/)
 void PdfParser::opSetStrokeRGBColor(Object args[], int /*numArgs*/) {
   GfxColor color;
 
-  state->setStrokePattern(NULL);
+  state->setStrokePattern(nullptr);
   state->setStrokeColorSpace(new GfxDeviceRGBColorSpace());
   for (int i = 0; i < 3; ++i) {
     color.c[i] = dblToCol(args[i].getNum());
@@ -1250,19 +1250,19 @@ void PdfParser::opSetFillColorSpace(Object args[], int /*numArgs*/)
 {
   Object obj;
 
-  state->setFillPattern(NULL);
+  state->setFillPattern(nullptr);
 #if defined(POPPLER_NEW_OBJECT_API)
   obj = res->lookupColorSpace(args[0].getName());
 #else
   res->lookupColorSpace(args[0].getName(), &obj);
 #endif
 
-  GfxColorSpace *colorSpace = 0;
+  GfxColorSpace *colorSpace = nullptr;
 #if defined(POPPLER_EVEN_NEWER_NEW_COLOR_SPACE_API)
   if (obj.isNull()) {
-    colorSpace = GfxColorSpace::parse(NULL, &args[0], NULL, NULL);
+    colorSpace = GfxColorSpace::parse(nullptr, &args[0], nullptr, nullptr);
   } else {
-    colorSpace = GfxColorSpace::parse(NULL, &obj, NULL, NULL);
+    colorSpace = GfxColorSpace::parse(nullptr, &obj, nullptr, nullptr);
   }
 #elif defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
   if (obj.isNull()) {
@@ -1295,9 +1295,9 @@ void PdfParser::opSetFillColorSpace(Object args[], int /*numArgs*/)
 void PdfParser::opSetStrokeColorSpace(Object args[], int /*numArgs*/)
 {
   Object obj;
-  GfxColorSpace *colorSpace = 0;
+  GfxColorSpace *colorSpace = nullptr;
 
-  state->setStrokePattern(NULL);
+  state->setStrokePattern(nullptr);
 #if defined(POPPLER_NEW_OBJECT_API)
   obj = res->lookupColorSpace(args[0].getName());
 #else
@@ -1305,9 +1305,9 @@ void PdfParser::opSetStrokeColorSpace(Object args[], int /*numArgs*/)
 #endif
 #if defined(POPPLER_EVEN_NEWER_NEW_COLOR_SPACE_API)
   if (obj.isNull()) {
-    colorSpace = GfxColorSpace::parse(NULL, &args[0], NULL, NULL);
+    colorSpace = GfxColorSpace::parse(nullptr, &args[0], nullptr, nullptr);
   } else {
-    colorSpace = GfxColorSpace::parse(NULL, &obj, NULL, NULL);
+    colorSpace = GfxColorSpace::parse(nullptr, &obj, nullptr, nullptr);
   }
 #elif defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
   if (obj.isNull()) {
@@ -1344,7 +1344,7 @@ void PdfParser::opSetFillColor(Object args[], int numArgs) {
     error(errSyntaxError, getPos(), "Incorrect number of arguments in 'sc' command");
     return;
   }
-  state->setFillPattern(NULL);
+  state->setFillPattern(nullptr);
   for (i = 0; i < numArgs; ++i) {
     color.c[i] = dblToCol(args[i].getNum());
   }
@@ -1360,7 +1360,7 @@ void PdfParser::opSetStrokeColor(Object args[], int numArgs) {
     error(errSyntaxError, getPos(), "Incorrect number of arguments in 'SC' command");
     return;
   }
-  state->setStrokePattern(NULL);
+  state->setStrokePattern(nullptr);
   for (i = 0; i < numArgs; ++i) {
     color.c[i] = dblToCol(args[i].getNum());
   }
@@ -1391,7 +1391,7 @@ void PdfParser::opSetFillColorN(Object args[], int numArgs) {
     GfxPattern *pattern;
 #if defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
     if (args[numArgs-1].isName() &&
-	(pattern = res->lookupPattern(args[numArgs-1].getName(), NULL, NULL))) {
+	(pattern = res->lookupPattern(args[numArgs-1].getName(), nullptr, nullptr))) {
       state->setFillPattern(pattern);
       builder->updateStyle(state);
     }
@@ -1408,7 +1408,7 @@ void PdfParser::opSetFillColorN(Object args[], int numArgs) {
       error(errSyntaxError, getPos(), "Incorrect number of arguments in 'scn' command");
       return;
     }
-    state->setFillPattern(NULL);
+    state->setFillPattern(nullptr);
     for (i = 0; i < numArgs && i < gfxColorMaxComps; ++i) {
       if (args[i].isNum()) {
 	color.c[i] = dblToCol(args[i].getNum());
@@ -1443,7 +1443,7 @@ void PdfParser::opSetStrokeColorN(Object args[], int numArgs) {
     GfxPattern *pattern;
 #if defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
     if (args[numArgs-1].isName() &&
-	(pattern = res->lookupPattern(args[numArgs-1].getName(), NULL, NULL))) {
+	(pattern = res->lookupPattern(args[numArgs-1].getName(), nullptr, nullptr))) {
       state->setStrokePattern(pattern);
       builder->updateStyle(state);
     }
@@ -1460,7 +1460,7 @@ void PdfParser::opSetStrokeColorN(Object args[], int numArgs) {
       error(errSyntaxError, getPos(), "Incorrect number of arguments in 'SCN' command");
       return;
     }
-    state->setStrokePattern(NULL);
+    state->setStrokePattern(nullptr);
     for (i = 0; i < numArgs && i < gfxColorMaxComps; ++i) {
       if (args[i].isNum()) {
 	color.c[i] = dblToCol(args[i].getNum());
@@ -1856,16 +1856,16 @@ void PdfParser::doShadingPatternFillFallback(GfxShadingPattern *sPat,
 // TODO not good that numArgs is ignored but args[] is used:
 void PdfParser::opShFill(Object args[], int /*numArgs*/)
 {
-  GfxShading *shading = 0;
-  GfxPath *savedPath = NULL;
+  GfxShading *shading = nullptr;
+  GfxPath *savedPath = nullptr;
   double xMin, yMin, xMax, yMax;
   double xTemp, yTemp;
   double gradientTransform[6];
-  double *matrix = NULL;
+  double *matrix = nullptr;
   GBool savedState = gFalse;
 
 #if defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
-  if (!(shading = res->lookupShading(args[0].getName(), NULL, NULL))) {
+  if (!(shading = res->lookupShading(args[0].getName(), nullptr, nullptr))) {
     return;
   }
 #else
@@ -1883,7 +1883,7 @@ void PdfParser::opShFill(Object args[], int /*numArgs*/)
       // check proper operator sequence
       // first there should be one W(*) and then one 'cm' somewhere before 'sh'
       GBool seenClip, seenConcat;
-      seenClip = (clipHistory->getClipPath() != NULL);
+      seenClip = (clipHistory->getClipPath() != nullptr);
       seenConcat = gFalse;
       int i = 1;
       while (i <= maxOperatorHistoryDepth) {
@@ -1909,7 +1909,7 @@ void PdfParser::opShFill(Object args[], int /*numArgs*/)
   // clip to bbox
   if (shading->getHasBBox()) {
     shading->getBBox(&xMin, &yMin, &xMax, &yMax);
-    if (matrix != NULL) {
+    if (matrix != nullptr) {
         xTemp = matrix[0]*xMin + matrix[2]*yMin + matrix[4];
         yTemp = matrix[1]*xMin + matrix[3]*yMin + matrix[5];
         state->moveTo(xTemp, yTemp);
@@ -2374,7 +2374,7 @@ void PdfParser::opSetFont(Object args[], int /*numArgs*/)
   if (!font) {
     // unsetting the font (drawing no text) is better than using the
     // previous one and drawing random glyphs from it
-    state->setFont(NULL, args[1].getNum());
+    state->setFont(nullptr, args[1].getNum());
     fontChanged = gTrue;
     return;
   }
@@ -2539,7 +2539,7 @@ void PdfParser::opMoveSetShowText(Object args[], int /*numArgs*/)
 // TODO not good that numArgs is ignored but args[] is used:
 void PdfParser::opShowSpaceText(Object args[], int /*numArgs*/)
 {
-  Array *a = 0;
+  Array *a = nullptr;
   Object obj;
   int wMode = 0;
 
@@ -2586,7 +2586,7 @@ void PdfParser::doShowText(const GooString *s) {
   int wMode;
   double riseX, riseY;
   CharCode code;
-  Unicode *u = NULL;
+  Unicode *u = nullptr;
   double x, y, dx, dy, tdx, tdy;
   double originX, originY, tOriginX, tOriginY;
   double oldCTM[6], newCTM[6];
@@ -3009,7 +3009,7 @@ void PdfParser::doImage(Object * /*ref*/, Stream *str, GBool inlineImg)
         }
         if (!obj1.isNull()) {
 #if defined(POPPLER_EVEN_NEWER_NEW_COLOR_SPACE_API)
-            colorSpace = GfxColorSpace::parse(NULL, &obj1, NULL, NULL);
+            colorSpace = GfxColorSpace::parse(nullptr, &obj1, nullptr, nullptr);
 #elif defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
             colorSpace = GfxColorSpace::parse(&obj1, NULL, NULL);
 #else
@@ -3022,7 +3022,7 @@ void PdfParser::doImage(Object * /*ref*/, Stream *str, GBool inlineImg)
         } else if (csMode == streamCSDeviceCMYK) {
             colorSpace = new GfxDeviceCMYKColorSpace();
         } else {
-            colorSpace = NULL;
+            colorSpace = nullptr;
         }
 #if !defined(POPPLER_NEW_OBJECT_API)
         obj1.free();
@@ -3055,11 +3055,11 @@ void PdfParser::doImage(Object * /*ref*/, Stream *str, GBool inlineImg)
         // get the mask
         int maskColors[2*gfxColorMaxComps];
         haveColorKeyMask = haveExplicitMask = haveSoftMask = gFalse;
-        Stream *maskStr = NULL;
+        Stream *maskStr = nullptr;
         int maskWidth = 0;
         int maskHeight = 0;
         maskInvert = gFalse;
-        GfxImageColorMap *maskColorMap = NULL;
+        GfxImageColorMap *maskColorMap = nullptr;
 #if defined(POPPLER_NEW_OBJECT_API)
         maskObj = dict->lookup(const_cast<char*>("Mask"));
         smaskObj = dict->lookup(const_cast<char*>("SMask"));
@@ -3180,7 +3180,7 @@ void PdfParser::doImage(Object * /*ref*/, Stream *str, GBool inlineImg)
 	            }
             }
 #if defined(POPPLER_EVEN_NEWER_NEW_COLOR_SPACE_API)
-            GfxColorSpace *maskColorSpace = GfxColorSpace::parse(NULL, &obj1, NULL, NULL);
+            GfxColorSpace *maskColorSpace = GfxColorSpace::parse(nullptr, &obj1, nullptr, nullptr);
 #elif defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
             GfxColorSpace *maskColorSpace = GfxColorSpace::parse(&obj1, NULL, NULL);
 #else
@@ -3355,7 +3355,7 @@ void PdfParser::doImage(Object * /*ref*/, Stream *str, GBool inlineImg)
 				maskStr, maskWidth, maskHeight, maskInvert, maskInterpolate);
         } else {
 	    builder->addImage(state, str, width, height, colorMap, interpolate,
-		        haveColorKeyMask ? maskColors : static_cast<int *>(NULL));
+		        haveColorKeyMask ? maskColors : static_cast<int *>(nullptr));
         }
         delete colorMap;
         
@@ -3468,11 +3468,11 @@ void PdfParser::doForm(Object *str) {
 #else
   dict->lookup(const_cast<char*>("Resources"), &resObj);
 #endif
-  resDict = resObj.isDict() ? resObj.getDict() : (Dict *)NULL;
+  resDict = resObj.isDict() ? resObj.getDict() : (Dict *)nullptr;
 
   // check for a transparency group
   transpGroup = isolated = knockout = gFalse;
-  blendingColorSpace = NULL;
+  blendingColorSpace = nullptr;
 #if defined(POPPLER_NEW_OBJECT_API)
   if ((obj1 = dict->lookup(const_cast<char*>("Group"))).isDict()) {
     if ((obj2 = obj1.dictLookup(const_cast<char*>("S"))).isName(const_cast<char*>("Transparency"))) {
@@ -3487,7 +3487,7 @@ void PdfParser::doForm(Object *str) {
       if (!obj1.dictLookup(const_cast<char*>("CS"), &obj3)->isNull()) {
 #endif
 #if defined(POPPLER_EVEN_NEWER_NEW_COLOR_SPACE_API)
-	blendingColorSpace = GfxColorSpace::parse(NULL, &obj3, NULL, NULL);
+	blendingColorSpace = GfxColorSpace::parse(nullptr, &obj3, nullptr, nullptr);
 #elif defined(POPPLER_EVEN_NEWER_COLOR_SPACE_API)
 	blendingColorSpace = GfxColorSpace::parse(&obj3, NULL, NULL);
 #else
@@ -3640,7 +3640,7 @@ void PdfParser::opBeginImage(Object /*args*/[], int /*numArgs*/)
 
   // display the image
   if (str) {
-    doImage(NULL, str, gTrue);
+    doImage(nullptr, str, gTrue);
   
     // skip 'EI' tag
     int c1 = str->getUndecodedStream()->getChar();
@@ -3701,7 +3701,7 @@ Stream *PdfParser::buildImageStream() {
     obj.free();
     dict.free();
 #endif
-    return NULL;
+    return nullptr;
   }
 #if !defined(POPPLER_NEW_OBJECT_API)
   obj.free();
@@ -3806,7 +3806,7 @@ void PdfParser::saveState() {
   bool is_radial = false;
 
   GfxPattern *pattern = state->getFillPattern();
-  if (pattern != NULL)
+  if (pattern != nullptr)
     if (pattern->getType() == 2 ) {
         GfxShadingPattern *shading_pattern = static_cast<GfxShadingPattern *>(pattern);
         GfxShading *shading = shading_pattern->getShading();
@@ -3861,8 +3861,8 @@ void PdfParser::setApproximationPrecision(int shadingType, double colorDelta,
 //------------------------------------------------------------------------
 
 ClipHistoryEntry::ClipHistoryEntry(GfxPath *clipPathA, GfxClipType clipTypeA) :
-  saved(NULL),
-  clipPath((clipPathA) ? clipPathA->copy() : NULL),
+  saved(nullptr),
+  clipPath((clipPathA) ? clipPathA->copy() : nullptr),
   clipType(clipTypeA)
 {
 }
@@ -3871,7 +3871,7 @@ ClipHistoryEntry::~ClipHistoryEntry()
 {
     if (clipPath) {
         delete clipPath;
-	clipPath = NULL;
+	clipPath = nullptr;
     }
 }
 
@@ -3884,7 +3884,7 @@ void ClipHistoryEntry::setClip(GfxPath *clipPathA, GfxClipType clipTypeA) {
         clipPath = clipPathA->copy();
         clipType = clipTypeA;
     } else {
-        clipPath = NULL;
+        clipPath = nullptr;
 	clipType = clipNormal;
     }
 }
@@ -3901,7 +3901,7 @@ ClipHistoryEntry *ClipHistoryEntry::restore() {
 
     if (saved) {
         oldEntry = saved;
-        saved = NULL;
+        saved = nullptr;
         delete this; // TODO really should avoid deleting from inside.
     } else {
         oldEntry = this;
@@ -3915,10 +3915,10 @@ ClipHistoryEntry::ClipHistoryEntry(ClipHistoryEntry *other) {
         this->clipPath = other->clipPath->copy();
         this->clipType = other->clipType;
     } else {
-        this->clipPath = NULL;
+        this->clipPath = nullptr;
 	this->clipType = clipNormal;
     }
-    saved = NULL;
+    saved = nullptr;
 }
 
 #endif /* HAVE_POPPLER */
diff --git a/src/extension/internal/pdfinput/pdf-parser.h b/src/extension/internal/pdfinput/pdf-parser.h
index f985b15ca..755e6741b 100644
--- a/src/extension/internal/pdfinput/pdf-parser.h
+++ b/src/extension/internal/pdfinput/pdf-parser.h
@@ -295,10 +295,10 @@ private:
   void doForm(Object *str);
   void doForm1(Object *str, Dict *resDict, double *matrix, double *bbox,
 	       GBool transpGroup = gFalse, GBool softMask = gFalse,
-	       GfxColorSpace *blendingColorSpace = NULL,
+	       GfxColorSpace *blendingColorSpace = nullptr,
 	       GBool isolated = gFalse, GBool knockout = gFalse,
-	       GBool alpha = gFalse, Function *transferFunc = NULL,
-	       GfxColor *backdropColor = NULL);
+	       GBool alpha = gFalse, Function *transferFunc = nullptr,
+	       GfxColor *backdropColor = nullptr);
 
   // in-line image operators
   void opBeginImage(Object args[], int numArgs);
diff --git a/src/extension/internal/pdfinput/svg-builder.cpp b/src/extension/internal/pdfinput/svg-builder.cpp
index 8e5a5f639..59481b9eb 100644
--- a/src/extension/internal/pdfinput/svg-builder.cpp
+++ b/src/extension/internal/pdfinput/svg-builder.cpp
@@ -109,14 +109,14 @@ SvgBuilder::~SvgBuilder() {
 }
 
 void SvgBuilder::_init() {
-    _font_style = NULL;
-    _current_font = NULL;
-    _font_specification = NULL;
+    _font_style = nullptr;
+    _current_font = nullptr;
+    _font_specification = nullptr;
     _font_scaling = 1;
     _need_font_update = true;
     _in_text_object = false;
     _invalidated_style = true;
-    _current_state = NULL;
+    _current_state = nullptr;
     _width = 0;
     _height = 0;
 
@@ -128,9 +128,9 @@ void SvgBuilder::_init() {
         _availableFontNames.push_back(pango_font_family_get_name(*iter));
     }
 
-    _transp_group_stack = NULL;
+    _transp_group_stack = nullptr;
     SvgGraphicsState initial_state;
-    initial_state.softmask = NULL;
+    initial_state.softmask = nullptr;
     initial_state.group_depth = 0;
     _state_stack.push_back(initial_state);
     _node_stack.push_back(_container);
@@ -186,7 +186,7 @@ Inkscape::XML::Node *SvgBuilder::pushNode(const char *name) {
 }
 
 Inkscape::XML::Node *SvgBuilder::popNode() {
-    Inkscape::XML::Node *node = NULL;
+    Inkscape::XML::Node *node = nullptr;
     if ( _node_stack.size() > 1 ) {
         node = _node_stack.back();
         _node_stack.pop_back();
@@ -215,7 +215,7 @@ Inkscape::XML::Node *SvgBuilder::pushGroup() {
             setAsLayer(_docname);
         }
     }
-    if (_container->parent()->attribute("inkscape:groupmode") != NULL) {
+    if (_container->parent()->attribute("inkscape:groupmode") != nullptr) {
         _ttm[0] = _ttm[3] = 1.0;    // clear ttm if parent is a layer
         _ttm[1] = _ttm[2] = _ttm[4] = _ttm[5] = 0.0;
         _ttm_is_set = false;
@@ -379,7 +379,7 @@ void SvgBuilder::_setStrokeStyle(SPCSSAttr *css, GfxState *state) {
         sp_repr_css_set_property(css, "stroke-dashoffset", os_offset.str().c_str());
     } else {
         sp_repr_css_set_property(css, "stroke-dasharray", "none");
-        sp_repr_css_set_property(css, "stroke-dashoffset", NULL);
+        sp_repr_css_set_property(css, "stroke-dashoffset", nullptr);
     }
 }
 
@@ -503,7 +503,7 @@ void SvgBuilder::addShadedFill(GfxShading *shading, double *matrix, GfxPath *pat
             SPObject *clip_obj = _doc->getObjectById(clip_path_id);
             if (clip_obj) {
                 clip_obj->deleteObject();
-                node->setAttribute("clip-path", NULL);
+                node->setAttribute("clip-path", nullptr);
                 TRACE(("removed clipping path: %s\n", clip_path_id));
             }
             break;
@@ -570,7 +570,7 @@ bool SvgBuilder::getTransform(double *transform) {
 void SvgBuilder::setTransform(double c0, double c1, double c2, double c3,
                               double c4, double c5) {
     // do not remember the group which is a layer
-    if ((_container->attribute("inkscape:groupmode") == NULL) && !_ttm_is_set) {
+    if ((_container->attribute("inkscape:groupmode") == nullptr) && !_ttm_is_set) {
         _ttm[0] = c0;
         _ttm[1] = c1;
         _ttm[2] = c2;
@@ -581,7 +581,7 @@ void SvgBuilder::setTransform(double c0, double c1, double c2, double c3,
     }
 
     // Avoid transforming a group with an already set clip-path
-    if ( _container->attribute("clip-path") != NULL ) {
+    if ( _container->attribute("clip-path") != nullptr ) {
         pushGroup();
     }
     TRACE(("setTransform: %f %f %f %f %f %f\n", c0, c1, c2, c3, c4, c5));
@@ -598,7 +598,7 @@ void SvgBuilder::setTransform(double const *transform) {
  * Used by PdfParser to decide when to do fallback operations.
  */
 bool SvgBuilder::isPatternTypeSupported(GfxPattern *pattern) {
-    if ( pattern != NULL ) {
+    if ( pattern != nullptr ) {
         if ( pattern->getType() == 2 ) {    // shading pattern
             GfxShading *shading = (static_cast<GfxShadingPattern *>(pattern))->getShading();
             int shadingType = shading->getType();
@@ -622,8 +622,8 @@ bool SvgBuilder::isPatternTypeSupported(GfxPattern *pattern) {
  * \return a url pointing to the created pattern
  */
 gchar *SvgBuilder::_createPattern(GfxPattern *pattern, GfxState *state, bool is_stroke) {
-    gchar *id = NULL;
-    if ( pattern != NULL ) {
+    gchar *id = nullptr;
+    if ( pattern != nullptr ) {
         if ( pattern->getType() == 2 ) {  // Shading pattern
             GfxShadingPattern *shading_pattern = static_cast<GfxShadingPattern *>(pattern);
             double *ptm;
@@ -656,7 +656,7 @@ gchar *SvgBuilder::_createPattern(GfxPattern *pattern, GfxState *state, bool is_
             id = _createTilingPattern(static_cast<GfxTilingPattern*>(pattern), state, is_stroke);
         }
     } else {
-        return NULL;
+        return nullptr;
     }
     gchar *urltext = g_strdup_printf ("url(#%s)", id);
     g_free(id);
@@ -719,7 +719,7 @@ gchar *SvgBuilder::_createTilingPattern(GfxTilingPattern *tiling_pattern,
     GfxPatternColorSpace *pat_cs = (GfxPatternColorSpace *)( is_stroke ? state->getStrokeColorSpace()
                                                             : state->getFillColorSpace() );
     // Set fill/stroke colors if this is an uncolored tiling pattern
-    GfxColorSpace *cs = NULL;
+    GfxColorSpace *cs = nullptr;
     if ( tiling_pattern->getPaintType() == 2 && ( cs = pat_cs->getUnder() ) ) {
         GfxState *pattern_state = pdf_parser->getState();
         pattern_state->setFillColorSpace(cs->copy());
@@ -785,7 +785,7 @@ gchar *SvgBuilder::_createGradient(GfxShading *shading, double *matrix, bool for
         num_funcs = radial_shading->getNFuncs();
         func = radial_shading->getFunc(0);
     } else {    // Unsupported shading type
-        return NULL;
+        return nullptr;
     }
     gradient->setAttribute("gradientUnits", "userSpaceOnUse");
     // If needed, flip the gradient transform around the y axis
@@ -807,7 +807,7 @@ gchar *SvgBuilder::_createGradient(GfxShading *shading, double *matrix, bool for
 
     if ( num_funcs > 1 || !_addGradientStops(gradient, shading, func) ) {
         Inkscape::GC::release(gradient);
-        return NULL;
+        return nullptr;
     }
 
     Inkscape::XML::Node *defs = _doc->getDefs()->getRepr();
@@ -827,8 +827,8 @@ void SvgBuilder::_addStopToGradient(Inkscape::XML::Node *gradient, double offset
     Inkscape::XML::Node *stop = _xml_doc->createElement("svg:stop");
     SPCSSAttr *css = sp_repr_css_attr_new();
     Inkscape::CSSOStringStream os_opacity;
-    gchar *color_text = NULL;
-    if ( _transp_group_stack != NULL && _transp_group_stack->for_softmask ) {
+    gchar *color_text = nullptr;
+    if ( _transp_group_stack != nullptr && _transp_group_stack->for_softmask ) {
         double gray = (double)color->r / 65535.0;
         gray = CLAMP(gray, 0.0, 1.0);
         os_opacity << gray;
@@ -1028,9 +1028,9 @@ void SvgBuilder::updateFont(GfxState *state) {
 
     // Prune the font name to get the correct font family name
     // In a PDF font names can look like this: IONIPB+MetaPlusBold-Italic
-    char *font_family = NULL;
-    char *font_style = NULL;
-    char *font_style_lowercase = NULL;
+    char *font_family = nullptr;
+    char *font_style = nullptr;
+    char *font_style_lowercase = nullptr;
     char *plus_sign = strstr(_font_specification, "+");
     if (plus_sign) {
         font_family = g_strdup(plus_sign + 1);
@@ -1038,7 +1038,7 @@ void SvgBuilder::updateFont(GfxState *state) {
     } else {
         font_family = g_strdup(_font_specification);
     }
-    char *style_delim = NULL;
+    char *style_delim = nullptr;
     if ( ( style_delim = g_strrstr(font_family, "-") ) ||
          ( style_delim = g_strrstr(font_family, ",") ) ) {
         font_style = style_delim + 1;
@@ -1077,7 +1077,7 @@ void SvgBuilder::updateFont(GfxState *state) {
 
     // Font weight
     GfxFont::Weight font_weight = font->getWeight();
-    char *css_font_weight = NULL;
+    char *css_font_weight = nullptr;
     if ( font_weight != GfxFont::WeightNotDefined ) {
         if ( font_weight == GfxFont::W400 ) {
             css_font_weight = (char*) "normal";
@@ -1109,7 +1109,7 @@ void SvgBuilder::updateFont(GfxState *state) {
 
     // Font stretch
     GfxFont::Stretch font_stretch = font->getStretch();
-    gchar *stretch_value = NULL;
+    gchar *stretch_value = nullptr;
     switch (font_stretch) {
         case GfxFont::UltraCondensed:
             stretch_value = (char*) "ultra-condensed";
@@ -1141,7 +1141,7 @@ void SvgBuilder::updateFont(GfxState *state) {
         default:
             break;
     }
-    if ( stretch_value != NULL ) {
+    if ( stretch_value != nullptr ) {
         sp_repr_css_set_property(_font_style, "font-stretch", stretch_value);
     }
 
@@ -1250,7 +1250,7 @@ void SvgBuilder::_flushText() {
     bool same_coords[2] = {true, true};
     Geom::Point last_delta_pos;
     unsigned int glyphs_in_a_row = 0;
-    Inkscape::XML::Node *tspan_node = NULL;
+    Inkscape::XML::Node *tspan_node = nullptr;
     Glib::ustring x_coords;
     Glib::ustring y_coords;
     Glib::ustring text_buffer;
@@ -1415,7 +1415,7 @@ void SvgBuilder::addChar(GfxState *state, double x, double y,
             uu[i] = u[i];
         }
 
-        gchar *tmp = g_utf16_to_utf8(uu, uLen, NULL, NULL, NULL);
+        gchar *tmp = g_utf16_to_utf8(uu, uLen, nullptr, nullptr, nullptr);
         if ( tmp && *tmp ) {
             new_glyph.code = tmp;
         } else {
@@ -1492,20 +1492,20 @@ Inkscape::XML::Node *SvgBuilder::_createImage(Stream *str, int width, int height
                                               bool invert_alpha) {
 
     // Create PNG write struct
-    png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
-    if ( png_ptr == NULL ) {
-        return NULL;
+    png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
+    if ( png_ptr == nullptr ) {
+        return nullptr;
     }
     // Create PNG info struct
     png_infop info_ptr = png_create_info_struct(png_ptr);
-    if ( info_ptr == NULL ) {
-        png_destroy_write_struct(&png_ptr, NULL);
-        return NULL;
+    if ( info_ptr == nullptr ) {
+        png_destroy_write_struct(&png_ptr, nullptr);
+        return nullptr;
     }
     // Set error handler
     if (setjmp(png_jmpbuf(png_ptr))) {
         png_destroy_write_struct(&png_ptr, &info_ptr);
-        return NULL;
+        return nullptr;
     }
     // Decide whether we should embed this image
     int attr_value = 1;
@@ -1514,8 +1514,8 @@ Inkscape::XML::Node *SvgBuilder::_createImage(Stream *str, int width, int height
     // Set read/write functions
     Inkscape::IO::StringOutputStream base64_string;
     Inkscape::IO::Base64OutputStream base64_stream(base64_string);
-    FILE *fp = NULL;
-    gchar *file_name = NULL;
+    FILE *fp = nullptr;
+    gchar *file_name = nullptr;
     if (embed_image) {
         base64_stream.setColumnWidth(0);   // Disable line breaks
         png_set_write_fn(png_ptr, &base64_stream, png_write_base64stream, png_flush_base64stream);
@@ -1523,10 +1523,10 @@ Inkscape::XML::Node *SvgBuilder::_createImage(Stream *str, int width, int height
         static int counter = 0;
         file_name = g_strdup_printf("%s_img%d.png", _docname, counter++);
         fp = fopen(file_name, "wb");
-        if ( fp == NULL ) {
+        if ( fp == nullptr ) {
             png_destroy_write_struct(&png_ptr, &info_ptr);
             g_free(file_name);
-            return NULL;
+            return nullptr;
         }
         png_init_io(png_ptr, fp);
     }
@@ -1646,7 +1646,7 @@ Inkscape::XML::Node *SvgBuilder::_createImage(Stream *str, int width, int height
             fclose(fp);
             g_free(file_name);
         }
-        return NULL;
+        return nullptr;
     }
     delete image_stream;
     str->close();
@@ -1712,7 +1712,7 @@ Inkscape::XML::Node *SvgBuilder::_createMask(double width, double height) {
         if ( !( defs && !strcmp(defs->name(), "svg:defs") ) ) {
             // Create <defs> node
             defs = _xml_doc->createElement("svg:defs");
-            _root->addChild(defs, NULL);
+            _root->addChild(defs, nullptr);
             Inkscape::GC::release(defs);
             defs = _root->firstChild();
         }
@@ -1754,12 +1754,12 @@ void SvgBuilder::addImageMask(GfxState *state, Stream *str, int width, int heigh
     // Scaling 1x1 surfaces might not work so skip setting a mask with this size
     if ( width > 1 || height > 1 ) {
         Inkscape::XML::Node *mask_image_node =
-            _createImage(str, width, height, NULL, interpolate, NULL, true, invert);
+            _createImage(str, width, height, nullptr, interpolate, nullptr, true, invert);
         if (mask_image_node) {
             // Create the mask
             Inkscape::XML::Node *mask_node = _createMask(1.0, 1.0);
             // Remove unnecessary transformation from the mask image
-            mask_image_node->setAttribute("transform", NULL);
+            mask_image_node->setAttribute("transform", nullptr);
             mask_node->appendChild(mask_image_node);
             Inkscape::GC::release(mask_image_node);
             gchar *mask_url = g_strdup_printf("url(#%s)", mask_node->attribute("id"));
@@ -1779,13 +1779,13 @@ void SvgBuilder::addMaskedImage(GfxState * /*state*/, Stream *str, int width, in
                                 bool invert_mask, bool mask_interpolate) {
 
     Inkscape::XML::Node *mask_image_node = _createImage(mask_str, mask_width, mask_height,
-                                          NULL, mask_interpolate, NULL, true, invert_mask);
-    Inkscape::XML::Node *image_node = _createImage(str, width, height, color_map, interpolate, NULL);
+                                          nullptr, mask_interpolate, nullptr, true, invert_mask);
+    Inkscape::XML::Node *image_node = _createImage(str, width, height, color_map, interpolate, nullptr);
     if ( mask_image_node && image_node ) {
         // Create mask for the image
         Inkscape::XML::Node *mask_node = _createMask(1.0, 1.0);
         // Remove unnecessary transformation from the mask image
-        mask_image_node->setAttribute("transform", NULL);
+        mask_image_node->setAttribute("transform", nullptr);
         mask_node->appendChild(mask_image_node);
         // Scale the mask to the size of the image
         Geom::Affine mask_transform((double)width, 0.0, 0.0, (double)height, 0.0, 0.0);
@@ -1812,13 +1812,13 @@ void SvgBuilder::addSoftMaskedImage(GfxState * /*state*/, Stream *str, int width
                                     GfxImageColorMap *mask_color_map, bool mask_interpolate) {
 
     Inkscape::XML::Node *mask_image_node = _createImage(mask_str, mask_width, mask_height,
-                                                        mask_color_map, mask_interpolate, NULL, true);
-    Inkscape::XML::Node *image_node = _createImage(str, width, height, color_map, interpolate, NULL);
+                                                        mask_color_map, mask_interpolate, nullptr, true);
+    Inkscape::XML::Node *image_node = _createImage(str, width, height, color_map, interpolate, nullptr);
     if ( mask_image_node && image_node ) {
         // Create mask for the image
         Inkscape::XML::Node *mask_node = _createMask(1.0, 1.0);
         // Remove unnecessary transformation from the mask image
-        mask_image_node->setAttribute("transform", NULL);
+        mask_image_node->setAttribute("transform", nullptr);
         mask_node->appendChild(mask_image_node);
         // Set mask and add image
         gchar *mask_url = g_strdup_printf("url(#%s)", mask_node->attribute("id"));
@@ -1902,7 +1902,7 @@ void SvgBuilder::setSoftMask(GfxState * /*state*/, double * /*bbox*/, bool /*alp
 
 void SvgBuilder::clearSoftMask(GfxState * /*state*/) {
     if (_state_stack.back().softmask) {
-        _state_stack.back().softmask = NULL;
+        _state_stack.back().softmask = nullptr;
         popGroup();
     }
 }
diff --git a/src/extension/internal/pdfinput/svg-builder.h b/src/extension/internal/pdfinput/svg-builder.h
index ed2a4d48e..499724a4c 100644
--- a/src/extension/internal/pdfinput/svg-builder.h
+++ b/src/extension/internal/pdfinput/svg-builder.h
@@ -94,7 +94,7 @@ public:
 
     // Property setting
     void setDocumentSize(double width, double height);  // Document size in px
-    void setAsLayer(char *layer_name=NULL);
+    void setAsLayer(char *layer_name=nullptr);
     void setGroupOpacity(double opacity);
     Inkscape::XML::Node *getPreferences() {
         return _preferences;
diff --git a/src/extension/internal/pov-out.cpp b/src/extension/internal/pov-out.cpp
index 15acb97ec..2215fbb3e 100644
--- a/src/extension/internal/pov-out.cpp
+++ b/src/extension/internal/pov-out.cpp
@@ -59,11 +59,11 @@ namespace Internal
 static void err(const char *fmt, ...)
 {
     va_list args;
-    g_log(NULL,  G_LOG_LEVEL_WARNING, "Pov-out err: ");
+    g_log(nullptr,  G_LOG_LEVEL_WARNING, "Pov-out err: ");
     va_start(args, fmt);
-    g_logv(NULL, G_LOG_LEVEL_WARNING, fmt, args);
+    g_logv(nullptr, G_LOG_LEVEL_WARNING, fmt, args);
     va_end(args);
-    g_log(NULL,  G_LOG_LEVEL_WARNING, "\n");
+    g_log(nullptr,  G_LOG_LEVEL_WARNING, "\n");
 }
 
 
@@ -211,7 +211,7 @@ void PovOutput::segment(int segNr,
  */
 bool PovOutput::doHeader()
 {
-    time_t tim = time(NULL);
+    time_t tim = time(nullptr);
     out("/*###################################################################\n");
     out("### This PovRay document was generated by Inkscape\n");
     out("### http://www.inkscape.org\n");
diff --git a/src/extension/internal/svg.cpp b/src/extension/internal/svg.cpp
index c4e12c174..f4e28e7ed 100644
--- a/src/extension/internal/svg.cpp
+++ b/src/extension/internal/svg.cpp
@@ -76,7 +76,7 @@ static void pruneExtendedNamespaces( Inkscape::XML::Node *repr )
             }
             // Can't change the set we're interating over while we are iterating.
             for ( std::vector<gchar const*>::iterator it = attrsRemoved.begin(); it != attrsRemoved.end(); ++it ) {
-                repr->setAttribute(*it, 0);
+                repr->setAttribute(*it, nullptr);
             }
         }
 
@@ -225,11 +225,11 @@ Svg::open (Inkscape::Extension::Input *mod, const gchar *uri)
         prefs->setBool("/dialogs/import/ask", !mod->get_param_bool("do_not_ask") );
     }
     
-    SPDocument * doc = SPDocument::createNewDoc (NULL, TRUE, TRUE);
+    SPDocument * doc = SPDocument::createNewDoc (nullptr, TRUE, TRUE);
     if (link_svg.compare("include") != 0 && is_import) {
         bool embed = ( link_svg.compare( "embed" ) == 0 );
         SPDocument * ret = SPDocument::createNewDoc(uri, TRUE);
-        SPNamedView *nv = sp_document_namedview(doc, NULL);
+        SPNamedView *nv = sp_document_namedview(doc, nullptr);
         Glib::ustring display_unit = nv->display_units->abbr;
         if (display_unit.empty()) {
             display_unit = "px";
@@ -259,7 +259,7 @@ Svg::open (Inkscape::Extension::Input *mod, const gchar *uri)
                 sp_embed_svg(image_node, uri);
             }
         } else {
-            gchar* _uri = g_filename_to_uri(uri, NULL, NULL);
+            gchar* _uri = g_filename_to_uri(uri, nullptr, nullptr);
             if(_uri) {
                 image_node->setAttribute("xlink:href", _uri);
                 g_free(_uri);
@@ -292,7 +292,7 @@ Svg::open (Inkscape::Extension::Input *mod, const gchar *uri)
                 return SPDocument::createNewDocFromMem(contents, length, 1);
             } catch (Gio::Error &e) {
                 g_warning("Could not load contents of non-local URI %s\n", uri);
-                return NULL;
+                return nullptr;
             }
         } else {
             uri = path.c_str();
@@ -329,8 +329,8 @@ Svg::open (Inkscape::Extension::Input *mod, const gchar *uri)
 void
 Svg::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar const *filename)
 {
-    g_return_if_fail(doc != NULL);
-    g_return_if_fail(filename != NULL);
+    g_return_if_fail(doc != nullptr);
+    g_return_if_fail(filename != nullptr);
     Inkscape::XML::Document *rdoc = doc->rdoc;
 
     bool const exportExtensions = ( !mod->get_id()
diff --git a/src/extension/internal/vsd-input.cpp b/src/extension/internal/vsd-input.cpp
index b650e2876..765e67648 100644
--- a/src/extension/internal/vsd-input.cpp
+++ b/src/extension/internal/vsd-input.cpp
@@ -245,7 +245,7 @@ SPDocument *VsdInput::open(Inkscape::Extension::Input * /*mod*/, const gchar * u
      #endif
 
      if (!libvisio::VisioDocument::isSupported(&input)) {
-          return NULL;
+          return nullptr;
      }
 
      RVNGStringVector output;
@@ -256,11 +256,11 @@ SPDocument *VsdInput::open(Inkscape::Extension::Input * /*mod*/, const gchar * u
 #else
      if (!libvisio::VisioDocument::generateSVG(&input, output)) {
 #endif
-          return NULL;
+          return nullptr;
      }
 
      if (output.empty()) {
-          return NULL;
+          return nullptr;
      }
 
      std::vector<RVNGString> tmpSVGOutput;
@@ -274,12 +274,12 @@ SPDocument *VsdInput::open(Inkscape::Extension::Input * /*mod*/, const gchar * u
 
      // If only one page is present, import that one without bothering user
      if (tmpSVGOutput.size() > 1) {
-          VsdImportDialog *dlg = 0;
+          VsdImportDialog *dlg = nullptr;
           if (INKSCAPE.use_gui()) {
                dlg = new VsdImportDialog(tmpSVGOutput);
                if (!dlg->showDialog()) {
                     delete dlg;
-                    return NULL;
+                    return nullptr;
                }
           }
 
diff --git a/src/extension/internal/wmf-inout.cpp b/src/extension/internal/wmf-inout.cpp
index 45f59ec03..5941aaf1e 100644
--- a/src/extension/internal/wmf-inout.cpp
+++ b/src/extension/internal/wmf-inout.cpp
@@ -82,7 +82,7 @@ Wmf::~Wmf (void) //The destructor
 bool
 Wmf::check (Inkscape::Extension::Extension * /*module*/)
 {
-    if (NULL == Inkscape::Extension::db.get(PRINT_WMF))
+    if (nullptr == Inkscape::Extension::db.get(PRINT_WMF))
         return FALSE;
     return TRUE;
 }
@@ -121,8 +121,8 @@ Wmf::print_document_to_file(SPDocument *doc, const gchar *filename)
     mod->finish();
     /* Release arena */
     mod->base->invoke_hide(mod->dkey);
-    mod->base = NULL;
-    mod->root = NULL; // deleted by invoke_hide
+    mod->base = nullptr;
+    mod->root = nullptr; // deleted by invoke_hide
 /* end */
 
     mod->set_param_string("destination", oldoutput);
@@ -138,7 +138,7 @@ Wmf::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar const *filena
     Inkscape::Extension::Extension * ext;
 
     ext = Inkscape::Extension::db.get(PRINT_WMF);
-    if (ext == NULL)
+    if (ext == nullptr)
         return;
 
     bool new_val         = mod->get_param_bool("textToPath");
@@ -162,7 +162,7 @@ Wmf::save(Inkscape::Extension::Output *mod, SPDocument *doc, gchar const *filena
     ext->set_param_bool("textToPath", new_val);
 
     // ensure usage of dot as decimal separator in scanf/printf functions (indepentendly of current locale)
-    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, NULL));
+    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, nullptr));
     setlocale(LC_NUMERIC, "C");
 
     print_document_to_file(doc, filename);
@@ -452,11 +452,11 @@ uint32_t Wmf::add_dib_image(PWMF_CALLBACK_DATA d, const char *dib, uint32_t iUsa
     int  dibparams = U_BI_UNKNOWN;  // type of image not yet determined
 
     MEMPNG mempng; // PNG in memory comes back in this
-    mempng.buffer = NULL;
+    mempng.buffer = nullptr;
 
-    char            *rgba_px = NULL;     // RGBA pixels
-    const char      *px      = NULL;     // DIB pixels
-    const U_RGBQUAD *ct      = NULL;     // DIB color table
+    char            *rgba_px = nullptr;     // RGBA pixels
+    const char      *px      = nullptr;     // DIB pixels
+    const U_RGBQUAD *ct      = nullptr;     // DIB color table
     uint32_t numCt;
     int32_t  width, height, colortype, invert; // if needed these values will be set by wget_DIB_params
     if(iUsage == U_DIB_RGB_COLORS){
@@ -484,7 +484,7 @@ uint32_t Wmf::add_dib_image(PWMF_CALLBACK_DATA d, const char *dib, uint32_t iUsa
         }
     }
 
-    gchar *base64String=NULL;
+    gchar *base64String=nullptr;
     if(dibparams == U_BI_JPEG || dibparams==U_BI_PNG){  // image was binary png or jpg in source file
         base64String = g_base64_encode((guchar*) px, numCt );
     }
@@ -551,10 +551,10 @@ uint32_t Wmf::add_bm16_image(PWMF_CALLBACK_DATA d, U_BITMAP16 Bm16, const char *
     char xywh[64]; // big enough
 
     MEMPNG mempng; // PNG in memory comes back in this
-    mempng.buffer = NULL;
+    mempng.buffer = nullptr;
 
-    char            *rgba_px = NULL;     // RGBA pixels
-    const U_RGBQUAD *ct      = NULL;     // color table, always NULL here
+    char            *rgba_px = nullptr;     // RGBA pixels
+    const U_RGBQUAD *ct      = nullptr;     // color table, always NULL here
     int32_t    width, height, colortype, numCt, invert;
     numCt     = 0;
     width     = Bm16.Width;              //  bitmap width in pixels.
@@ -582,7 +582,7 @@ uint32_t Wmf::add_bm16_image(PWMF_CALLBACK_DATA d, U_BITMAP16 Bm16, const char *
         free(rgba_px);
     }
 
-    gchar *base64String=NULL;
+    gchar *base64String=nullptr;
     if(mempng.buffer){             // image was Bm16 in source file, converted to png in this routine
         base64String = g_base64_encode((guchar*) mempng.buffer, mempng.size );
         free(mempng.buffer);
@@ -658,7 +658,7 @@ int Wmf::in_clips(PWMF_CALLBACK_DATA d, const char *test){
 void Wmf::add_clips(PWMF_CALLBACK_DATA d, const char *clippath, unsigned int logic){
     int op = combine_ops_to_livarot(logic);
     Geom::PathVector combined_vect;
-    char *combined = NULL;
+    char *combined = nullptr;
     if (op >= 0 && d->dc[d->level].clip_id) {
         unsigned int real_idx = d->dc[d->level].clip_id - 1;
         Geom::PathVector old_vect = sp_svg_read_pathv(d->clips.strings[real_idx]);
@@ -967,7 +967,7 @@ void
 Wmf::select_pen(PWMF_CALLBACK_DATA d, int index)
 {
     int width;
-    char *record = NULL;
+    char *record = nullptr;
     U_PEN up;
 
     if (index < 0 && index >= d->n_obj){ return; }
@@ -1153,7 +1153,7 @@ Wmf::select_brush(PWMF_CALLBACK_DATA d, int index)
 void
 Wmf::select_font(PWMF_CALLBACK_DATA d, int index)
 {
-    char         *record = NULL;
+    char         *record = nullptr;
     const char   *memfont;
     const char   *facename;
     U_FONT        font;
@@ -1221,7 +1221,7 @@ Wmf::select_font(PWMF_CALLBACK_DATA d, int index)
 int Wmf::insertable_object(PWMF_CALLBACK_DATA d)
 {
     int index = d->low_water;  // Start looking from here, it may already have been filled
-    while(index < d->n_obj &&  d->wmf_obj[index].record != NULL){ index++; }
+    while(index < d->n_obj &&  d->wmf_obj[index].record != nullptr){ index++; }
     if(index >= d->n_obj)return(-1);  // this is a big problem, percolate it back up so the program can get out of this gracefully
     d->low_water = index; // Could probably be index+1
     return(index);
@@ -1265,7 +1265,7 @@ Wmf::delete_object(PWMF_CALLBACK_DATA d, int index)
 // files too big to fit into memory.
         if (d->wmf_obj[index].record)
             free(d->wmf_obj[index].record);
-        d->wmf_obj[index].record = NULL;
+        d->wmf_obj[index].record = nullptr;
         if(index < d->low_water)d->low_water = index;
     }
 }
@@ -1321,12 +1321,12 @@ void Wmf::common_dib_to_image(PWMF_CALLBACK_DATA d, const char *dib,
     tmp_image << " y=\"" << dy << "\"\n x=\"" << dx <<"\"\n ";
 
     MEMPNG mempng; // PNG in memory comes back in this
-    mempng.buffer = NULL;
+    mempng.buffer = nullptr;
 
-    char            *rgba_px = NULL;        // RGBA pixels
-    char            *sub_px  = NULL;        // RGBA pixels, subarray
-    const char      *px      = NULL;        // DIB pixels
-    const U_RGBQUAD *ct      = NULL;        // color table
+    char            *rgba_px = nullptr;        // RGBA pixels
+    char            *sub_px  = nullptr;        // RGBA pixels, subarray
+    const char      *px      = nullptr;        // DIB pixels
+    const U_RGBQUAD *ct      = nullptr;        // color table
     uint32_t numCt;
     int32_t width, height, colortype, invert;  // if needed these values will be set in wget_DIB_params
     if(iUsage == U_DIB_RGB_COLORS){
@@ -1367,7 +1367,7 @@ void Wmf::common_dib_to_image(PWMF_CALLBACK_DATA d, const char *dib,
         }
     }
 
-    gchar *base64String=NULL;
+    gchar *base64String=nullptr;
     if(dibparams == U_BI_JPEG){    // image was binary jpg in source file
         tmp_image << " xlink:href=\"data:image/jpeg;base64,";
         base64String = g_base64_encode((guchar*) px, numCt );
@@ -1422,11 +1422,11 @@ void Wmf::common_bm16_to_image(PWMF_CALLBACK_DATA d, U_BITMAP16 Bm16, const char
     tmp_image << " y=\"" << dy << "\"\n x=\"" << dx <<"\"\n ";
 
     MEMPNG mempng; // PNG in memory comes back in this
-    mempng.buffer = NULL;
+    mempng.buffer = nullptr;
 
-    char            *rgba_px = NULL;        // RGBA pixels
-    char            *sub_px  = NULL;        // RGBA pixels, subarray
-    const U_RGBQUAD *ct      = NULL;        // color table
+    char            *rgba_px = nullptr;        // RGBA pixels
+    char            *sub_px  = nullptr;        // RGBA pixels, subarray
+    const U_RGBQUAD *ct      = nullptr;        // color table
     int32_t width, height, colortype, numCt, invert;
 
     numCt     = 0;
@@ -1470,7 +1470,7 @@ void Wmf::common_bm16_to_image(PWMF_CALLBACK_DATA d, U_BITMAP16 Bm16, const char
         free(sub_px);
     }
 
-    gchar *base64String=NULL;
+    gchar *base64String=nullptr;
     if(mempng.buffer){             // image was Bm16 in source file, converted to png in this routine
         tmp_image << " xlink:href=\"data:image/png;base64,";
         base64String = g_base64_encode((guchar*) mempng.buffer, mempng.size );
@@ -1541,14 +1541,14 @@ int Wmf::myMetaFileProc(const char *contents, unsigned int length, PWMF_CALLBACK
     int  wDbgComment=0;
     int  wDbgFinal=0;
     char const* wDbgString = getenv( "INKSCAPE_DBG_WMF" );
-    if ( wDbgString != NULL ) {
+    if ( wDbgString != nullptr ) {
         if(strstr(wDbgString,"RECORD")){  wDbgRecord  = 1; }
         if(strstr(wDbgString,"COMMENT")){ wDbgComment = 1; }
         if(strstr(wDbgString,"FINAL")){   wDbgFinal   = 1; }
     }
 
     /* initialize the tsp for text reassembly */
-    tsp.string     = NULL;
+    tsp.string     = nullptr;
     tsp.ori        = 0.0;  /* degrees */
     tsp.fs         = 12.0; /* font size */
     tsp.x          = 0.0;
@@ -1592,10 +1592,10 @@ int Wmf::myMetaFileProc(const char *contents, unsigned int length, PWMF_CALLBACK
 
         // Init the new wmf_obj list elements to null, provided the
         // dynamic allocation succeeded.
-        if ( d->wmf_obj != NULL )
+        if ( d->wmf_obj != nullptr )
         {
             for( int i=0; i < d->n_obj; ++i )
-                d->wmf_obj[i].record = NULL;
+                d->wmf_obj[i].record = nullptr;
         } //if
 
         if(!Placeable.Inch){ Placeable.Inch= 1440; }
@@ -2445,7 +2445,7 @@ std::cout << "BEFORE DRAW"
                 }
                 if(d->dc[old_level].font_name){
                     free(d->dc[old_level].font_name); // else memory leak
-                    d->dc[old_level].font_name = NULL;
+                    d->dc[old_level].font_name = nullptr;
                 }
                 old_level--;
             }
@@ -2557,9 +2557,9 @@ std::cout << "BEFORE DRAW"
 
             /* Rotation issues are handled entirely in libTERE now */
 
-            uint32_t *dup_wt = NULL;
+            uint32_t *dup_wt = nullptr;
 
-            dup_wt = U_Latin1ToUtf32le(text, cChars, NULL);
+            dup_wt = U_Latin1ToUtf32le(text, cChars, nullptr);
             if(!dup_wt)dup_wt = unknown_chars(cChars);
 
             msdepua(dup_wt); //convert everything in Microsoft's private use area.  For Symbol, Wingdings, Dingbats
@@ -2570,12 +2570,12 @@ std::cout << "BEFORE DRAW"
             }
 
             char *ansi_text;
-            ansi_text = (char *) U_Utf32leToUtf8((uint32_t *)dup_wt, 0, NULL);
+            ansi_text = (char *) U_Utf32leToUtf8((uint32_t *)dup_wt, 0, nullptr);
             free(dup_wt);
             // Empty text or starts with an invalid escape/control sequence, which is bogus text.  Throw it out before g_markup_escape_text can make things worse
             if(*((uint8_t *)ansi_text) <= 0x1F){
                 free(ansi_text);
-                ansi_text=NULL;
+                ansi_text=nullptr;
             }
 
             if (ansi_text) {
@@ -3101,18 +3101,18 @@ SPDocument *
 Wmf::open( Inkscape::Extension::Input * /*mod*/, const gchar *uri )
 {
 
-    if (uri == NULL) {
-        return NULL;
+    if (uri == nullptr) {
+        return nullptr;
     }
 
     // ensure usage of dot as decimal separator in scanf/printf functions (indepentendly of current locale)
-    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, NULL));
+    char *oldlocale = g_strdup(setlocale(LC_NUMERIC, nullptr));
     setlocale(LC_NUMERIC, "C");
 
     WMF_CALLBACK_DATA d;
     
     d.n_obj = 0;     //these might not be set otherwise if the input file is corrupt
-    d.wmf_obj=NULL; 
+    d.wmf_obj=nullptr; 
 
     // Default font, WMF spec says device can pick whatever it wants. 
     // WMF files that do not specify a  font are unlikely to look very good!
@@ -3150,10 +3150,10 @@ Wmf::open( Inkscape::Extension::Input * /*mod*/, const gchar *uri )
 
     size_t length;
     char *contents;
-    if(wmf_readdata(uri, &contents, &length))return(NULL);
+    if(wmf_readdata(uri, &contents, &length))return(nullptr);
 
     // set up the text reassembly system
-    if(!(d.tri = trinfo_init(NULL)))return(NULL);
+    if(!(d.tri = trinfo_init(nullptr)))return(nullptr);
     (void) trinfo_load_ft_opts(d.tri, 1,
       FT_LOAD_NO_SCALE | FT_LOAD_NO_HINTING  | FT_LOAD_NO_BITMAP,
       FT_KERNING_UNSCALED);
@@ -3163,7 +3163,7 @@ Wmf::open( Inkscape::Extension::Input * /*mod*/, const gchar *uri )
 
 //    std::cout << "SVG Output: " << std::endl << d.outsvg << std::endl;
 
-    SPDocument *doc = NULL;
+    SPDocument *doc = nullptr;
     if (good) {
         doc = SPDocument::createNewDocFromMem(d.outsvg.c_str(), strlen(d.outsvg.c_str()), TRUE);
     }
diff --git a/src/extension/internal/wmf-inout.h b/src/extension/internal/wmf-inout.h
index 02280f6d8..a9831a7c6 100644
--- a/src/extension/internal/wmf-inout.h
+++ b/src/extension/internal/wmf-inout.h
@@ -30,7 +30,7 @@ typedef struct wmf_object {
     wmf_object() :
         type(0),
         level(0),
-        record(NULL)
+        record(nullptr)
     {};
     int type;
     int level;
@@ -41,7 +41,7 @@ typedef struct wmf_strings {
     wmf_strings() :
         size(0),
         count(0),
-        strings(NULL)
+        strings(nullptr)
     {};
     int size;         // number of slots allocated in strings
     int count;        // number of slots used in strings
@@ -51,7 +51,7 @@ typedef struct wmf_strings {
 typedef struct wmf_device_context {
     wmf_device_context() :
         // SPStyle: class with constructor
-        font_name(NULL),
+        font_name(nullptr),
         clip_id(0),
         stroke_set(false), stroke_mode(0), stroke_idx(0), stroke_recidx(0),
         fill_set(false),   fill_mode(0),   fill_idx(0),   fill_recidx(0),
@@ -65,7 +65,7 @@ typedef struct wmf_device_context {
         textAlign(0)
         // worldTransform, cur
     {
-        font_name = NULL;
+        font_name = nullptr;
         sizeWnd = point16_set( 0.0, 0.0 );
         sizeView = point16_set( 0.0, 0.0 );
         winorg = point16_set( 0.0, 0.0 );
@@ -126,7 +126,7 @@ typedef struct wmf_callback_data {
         dwRop2(U_R2_COPYPEN), dwRop3(0),
         id(0), drawtype(0),
         // hatches, images, gradients,  struct w/ constructor
-        tri(NULL),
+        tri(nullptr),
         n_obj(0),
         low_water(0)
         //wmf_obj
diff --git a/src/extension/internal/wmf-print.cpp b/src/extension/internal/wmf-print.cpp
index cdc59298b..d98d28b09 100644
--- a/src/extension/internal/wmf-print.cpp
+++ b/src/extension/internal/wmf-print.cpp
@@ -77,8 +77,8 @@ namespace Internal {
 /* globals */
 static double       PX2WORLD;   // value set in begin()
 static bool         FixPPTCharPos, FixPPTDashLine, FixPPTGrad2Polys, FixPPTPatternAsHatch;
-static WMFTRACK    *wt               = NULL;
-static WMFHANDLES  *wht              = NULL;
+static WMFTRACK    *wt               = nullptr;
+static WMFHANDLES  *wht              = nullptr;
 
 void PrintWmf::smuggle_adxky_out(const char *string, int16_t **adx, double *ky, int *rtl, int *ndx, float scale)
 {
@@ -87,7 +87,7 @@ void PrintWmf::smuggle_adxky_out(const char *string, int16_t **adx, double *ky,
     int16_t   *ladx;
     const char *cptr = &string[strlen(string) + 1]; // this works because of the first fake terminator
 
-    *adx = NULL;
+    *adx = nullptr;
     *ky  = 0.0;       // set a default value
     sscanf(cptr, "%7d", ndx);
     if (!*ndx) {
@@ -403,8 +403,8 @@ int PrintWmf::create_brush(SPStyle const *style, U_COLORREF *fcolor)
         } else if (SP_IS_GRADIENT(SP_STYLE_FILL_SERVER(style))) { // must be a gradient
             // currently we do not do anything with gradients, the code below just sets the color to the average of the stops
             SPPaintServer *paintserver = style->fill.value.href->getObject();
-            SPLinearGradient *lg = NULL;
-            SPRadialGradient *rg = NULL;
+            SPLinearGradient *lg = nullptr;
+            SPRadialGradient *rg = nullptr;
 
             if (SP_IS_LINEARGRADIENT(paintserver)) {
                 lg = SP_LINEARGRADIENT(paintserver);
@@ -524,7 +524,7 @@ void PrintWmf::destroy_brush()
 
 int PrintWmf::create_pen(SPStyle const *style, const Geom::Affine &transform)
 {
-    char                *rec       = NULL;
+    char                *rec       = nullptr;
     uint32_t             pen;
     uint32_t             penstyle;
     U_COLORREF           penColor;
@@ -642,7 +642,7 @@ int PrintWmf::create_pen(SPStyle const *style, const Geom::Affine &transform)
 //  delete the defined pen object
 void PrintWmf::destroy_pen()
 {
-    char *rec = NULL;
+    char *rec = nullptr;
     // WMF lets any object be deleted whenever, and the chips fall where they may...
     if (hpen) {
         rec = wdeleteobject_set(&hpen, wht);
@@ -676,7 +676,7 @@ unsigned int PrintWmf::fill(
 
     fill_transform = tf;
 
-    if (create_brush(style, NULL)) {
+    if (create_brush(style, nullptr)) {
         /*
             Handle gradients.  Uses modified livarot as 2geom boolops is currently broken.
             Can handle gradients with multiple stops.
@@ -861,7 +861,7 @@ unsigned int PrintWmf::stroke(
     Geom::OptRect const &/*pbox*/, Geom::OptRect const &/*dbox*/, Geom::OptRect const &/*bbox*/)
 {
 
-    char *rec = NULL;
+    char *rec = nullptr;
     Geom::Affine tf = m_tr_stack.top();
 
     use_stroke = true;
@@ -940,7 +940,7 @@ bool PrintWmf::print_simple_shape(Geom::PathVector const &pathv, const Geom::Aff
     int moves  = 0;
     int lines  = 0;
     int curves = 0;
-    char *rec  = NULL;
+    char *rec  = nullptr;
 
     for (Geom::PathVector::const_iterator pit = pv.begin(); pit != pv.end(); ++pit) {
         moves++;
@@ -1126,7 +1126,7 @@ unsigned int PrintWmf::image(
     SPStyle const * /*style*/)  /** provides indirect link to image object */
 {
     double x1, y1, dw, dh;
-    char *rec = NULL;
+    char *rec = nullptr;
     Geom::Affine tf = m_tr_stack.top();
 
     rec = U_WMRSETSTRETCHBLTMODE_set(U_COLORONCOLOR);
@@ -1189,7 +1189,7 @@ unsigned int PrintWmf::image(
 // may also be called with a simple_shape or an empty path, whereupon it just returns without doing anything
 unsigned int PrintWmf::print_pathv(Geom::PathVector const &pathv, const Geom::Affine &transform)
 {
-    char       *rec = NULL;
+    char       *rec = nullptr;
     U_POINT16  *pt16hold, *pt16ptr;
     uint16_t   *n16hold;
     uint16_t   *n16ptr;
@@ -1349,7 +1349,7 @@ unsigned int PrintWmf::text(Inkscape::Extension::Print * /*mod*/, char const *te
         return 0;
     }
 
-    char *rec = NULL;
+    char *rec = nullptr;
     int ccount, newfont;
     int fix90n = 0;
     uint32_t hfont = 0;
@@ -1379,14 +1379,14 @@ unsigned int PrintWmf::text(Inkscape::Extension::Print * /*mod*/, char const *te
     }
 
     char *text2 = strdup(text);  // because U_Utf8ToUtf16le calls iconv which does not like a const char *
-    uint16_t *unicode_text = U_Utf8ToUtf16le(text2, 0, NULL);
+    uint16_t *unicode_text = U_Utf8ToUtf16le(text2, 0, nullptr);
     free(text2);
     //translates Unicode  as Utf16le to NonUnicode, if possible.  If any translate, all will, and all to
     //the same font, because of code in Layout::print
     UnicodeToNon(unicode_text, &ccount, &newfont);
     // The preceding hopefully handled conversions to symbol, wingdings or zapf dingbats.  Now slam everything
     // else down into latin1, which is all WMF can handle.  If the language isn't English expect terrible results.
-    char *latin1_text = U_Utf16leToLatin1(unicode_text, 0, NULL);
+    char *latin1_text = U_Utf16leToLatin1(unicode_text, 0, nullptr);
     free(unicode_text);
 
     // in some cases a UTF string may reduce to NO latin1 characters, which returns NULL
@@ -1439,9 +1439,9 @@ unsigned int PrintWmf::text(Inkscape::Extension::Print * /*mod*/, char const *te
         // of the special fonts.
         char *facename;
         if (!newfont) {
-            facename = U_Utf8ToLatin1(style->font_family.value, 0, NULL);
+            facename = U_Utf8ToLatin1(style->font_family.value, 0, nullptr);
         } else {
-            facename = U_Utf8ToLatin1(FontName(newfont), 0, NULL);
+            facename = U_Utf8ToLatin1(FontName(newfont), 0, nullptr);
         }
 
         // Scale the text to the minimum stretch. (It tends to stay within bounding rectangles even if
diff --git a/src/extension/internal/wpg-input.cpp b/src/extension/internal/wpg-input.cpp
index 2f3bfe27b..0953e5696 100644
--- a/src/extension/internal/wpg-input.cpp
+++ b/src/extension/internal/wpg-input.cpp
@@ -111,7 +111,7 @@ SPDocument *WpgInput::open(Inkscape::Extension::Input * /*mod*/, const gchar * u
         // fprintf(stderr, "ERROR: Unsupported file format (unsupported version) or file is encrypted!\n");
         // printf("I'm giving up not supported\n");
         delete input;
-        return NULL;
+        return nullptr;
     }
 
 #if WITH_LIBWPG03
@@ -120,7 +120,7 @@ SPDocument *WpgInput::open(Inkscape::Extension::Input * /*mod*/, const gchar * u
 
     if (!libwpg::WPGraphics::parse(input, &generator) || vec.empty() || vec[0].empty()) {
         delete input;
-        return NULL;
+        return nullptr;
     }
 
     RVNGString output("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n");
diff --git a/src/extension/loader.cpp b/src/extension/loader.cpp
index 164a5cecf..7761b79bd 100644
--- a/src/extension/loader.cpp
+++ b/src/extension/loader.cpp
@@ -26,9 +26,9 @@ typedef const gchar *(*_getInkscapeVersion)(void);
 
 bool Loader::load_dependency(Dependency *dep)
 {
-    GModule *module = NULL;
+    GModule *module = nullptr;
     module = g_module_open(dep->get_name(), (GModuleFlags)0);
-    if (module == NULL) {
+    if (module == nullptr) {
         return false;
     }
     return true;
@@ -47,7 +47,7 @@ Implementation::Implementation *Loader::load_implementation(Inkscape::XML::Docum
         Inkscape::XML::Node *child_repr = repr->firstChild();
         
         // Iterate over the xml content
-        while (child_repr != NULL) {
+        while (child_repr != nullptr) {
             char const *chname = child_repr->name();
             if (!strncmp(chname, INKSCAPE_EXTENSION_NS_NC, strlen(INKSCAPE_EXTENSION_NS_NC))) {
                 chname += strlen(INKSCAPE_EXTENSION_NS);
@@ -62,7 +62,7 @@ Implementation::Implementation *Loader::load_implementation(Inkscape::XML::Docum
                     // Could not load dependency, we abort
                     const char *res = g_module_error();
                     g_warning("Unable to load dependency %s of plugin %s.\nDetails: %s\n", dep.get_name(), "<todo>", res);
-                    return NULL;
+                    return nullptr;
                 }
             } 
 
@@ -71,20 +71,20 @@ Implementation::Implementation *Loader::load_implementation(Inkscape::XML::Docum
                 
                 // The name of the plugin is actually the library file we want to load
                 if (const gchar *name = child_repr->attribute("name")) {
-                    GModule *module = NULL;
-                    _getImplementation GetImplementation = NULL;
-                    _getInkscapeVersion GetInkscapeVersion = NULL;
+                    GModule *module = nullptr;
+                    _getImplementation GetImplementation = nullptr;
+                    _getInkscapeVersion GetInkscapeVersion = nullptr;
                     
                     // build the path where to look for the plugin
-                    gchar *path = g_build_filename(_baseDirectory.c_str(), name, (char *) NULL);
+                    gchar *path = g_build_filename(_baseDirectory.c_str(), name, (char *) nullptr);
                     module = g_module_open(path, G_MODULE_BIND_LOCAL);
                     g_free(path);
                     
-                    if (module == NULL) {
+                    if (module == nullptr) {
                         // we were not able to load the plugin, write warning and abort
                         const char *res = g_module_error();
                         g_warning("Unable to load extension %s.\nDetails: %s\n", name, res);
-                        return NULL;
+                        return nullptr;
                     }
 
                     // Get a handle to the version function of the module
@@ -92,7 +92,7 @@ Implementation::Implementation *Loader::load_implementation(Inkscape::XML::Docum
                         // This didn't work, write warning and abort
                         const char *res = g_module_error();
                         g_warning("Unable to load extension %s.\nDetails: %s\n", name, res);
-                        return NULL;
+                        return nullptr;
                     }
                     
                     // Get a handle to the function that delivers the implementation
@@ -100,7 +100,7 @@ Implementation::Implementation *Loader::load_implementation(Inkscape::XML::Docum
                         // This didn't work, write warning and abort
                         const char *res = g_module_error();
                         g_warning("Unable to load extension %s.\nDetails: %s\n", name, res);
-                        return NULL;
+                        return nullptr;
                     }
                     
                     // Get version and test against this version
@@ -121,7 +121,7 @@ Implementation::Implementation *Loader::load_implementation(Inkscape::XML::Docum
     } catch (std::exception &e) {
         g_warning("Unable to load extension.");
     }
-    return NULL;
+    return nullptr;
 }
 
 } // namespace Extension
diff --git a/src/extension/output.cpp b/src/extension/output.cpp
index 50b00f972..d6f95c19a 100644
--- a/src/extension/output.cpp
+++ b/src/extension/output.cpp
@@ -37,21 +37,21 @@ namespace Extension {
 */
 Output::Output (Inkscape::XML::Node * in_repr, Implementation::Implementation * in_imp) : Extension(in_repr, in_imp)
 {
-    mimetype = NULL;
-    extension = NULL;
-    filetypename = NULL;
-    filetypetooltip = NULL;
+    mimetype = nullptr;
+    extension = nullptr;
+    filetypename = nullptr;
+    filetypetooltip = nullptr;
 	dataloss = TRUE;
 
-    if (repr != NULL) {
+    if (repr != nullptr) {
         Inkscape::XML::Node * child_repr;
 
         child_repr = repr->firstChild();
 
-        while (child_repr != NULL) {
+        while (child_repr != nullptr) {
             if (!strcmp(child_repr->name(), INKSCAPE_EXTENSION_NS "output")) {
                 child_repr = child_repr->firstChild();
-                while (child_repr != NULL) {
+                while (child_repr != nullptr) {
                     char const * chname = child_repr->name();
 					if (!strncmp(chname, INKSCAPE_EXTENSION_NS_NC, strlen(INKSCAPE_EXTENSION_NS_NC))) {
 						chname += strlen(INKSCAPE_EXTENSION_NS);
@@ -115,9 +115,9 @@ Output::~Output (void)
 bool
 Output::check (void)
 {
-	if (extension == NULL)
+	if (extension == nullptr)
 		return FALSE;
-	if (mimetype == NULL)
+	if (mimetype == nullptr)
 		return FALSE;
 
 	return Extension::check();
@@ -150,7 +150,7 @@ Output::get_extension(void)
 gchar *
 Output::get_filetypename(void)
 {
-    if (filetypename != NULL)
+    if (filetypename != nullptr)
         return filetypename;
     else
         return get_name();
@@ -181,7 +181,7 @@ Output::prefs (void)
 
     Gtk::Widget * controls;
     controls = imp->prefs_output(this);
-    if (controls == NULL) {
+    if (controls == nullptr) {
         // std::cout << "No preferences for Output" << std::endl;
         return true;
     }
diff --git a/src/extension/output.h b/src/extension/output.h
index c28706cf4..4f2924852 100644
--- a/src/extension/output.h
+++ b/src/extension/output.h
@@ -34,7 +34,7 @@ public:
     class export_id_not_found {  /**< The object ID requested for export could not be found in the document */
         public:
             const gchar * const id;
-            export_id_not_found(const gchar * const id = NULL) : id{id} {};
+            export_id_not_found(const gchar * const id = nullptr) : id{id} {};
     };
 
                  Output (Inkscape::XML::Node * in_repr,
diff --git a/src/extension/param/bool.cpp b/src/extension/param/bool.cpp
index 80bc89138..eea660f69 100644
--- a/src/extension/param/bool.cpp
+++ b/src/extension/param/bool.cpp
@@ -33,12 +33,12 @@ ParamBool::ParamBool(const gchar * name,
     : Parameter(name, text, description, hidden, indent, ext)
     , _value(false)
 {
-    const char * defaultval = NULL;
-    if (xml->firstChild() != NULL) {
+    const char * defaultval = nullptr;
+    if (xml->firstChild() != nullptr) {
         defaultval = xml->firstChild()->content();
     }
 
-    if (defaultval != NULL && (!strcmp(defaultval, "true") || !strcmp(defaultval, "1"))) {
+    if (defaultval != nullptr && (!strcmp(defaultval, "true") || !strcmp(defaultval, "1"))) {
         _value = true;
     } else {
         _value = false;
@@ -85,7 +85,7 @@ public:
      */
     ParamBoolCheckButton (ParamBool * param, gchar * label, SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal) :
             Gtk::CheckButton(label), _pref(param), _doc(doc), _node(node), _changeSignal(changeSignal) {
-        this->set_active(_pref->get(NULL, NULL) /**\todo fix */);
+        this->set_active(_pref->get(nullptr, nullptr) /**\todo fix */);
         this->signal_toggled().connect(sigc::mem_fun(this, &ParamBoolCheckButton::on_toggle));
         return;
     }
@@ -106,8 +106,8 @@ private:
 
 void ParamBoolCheckButton::on_toggle(void)
 {
-    _pref->set(this->get_active(), NULL /**\todo fix this */, NULL);
-    if (_changeSignal != NULL) {
+    _pref->set(this->get_active(), nullptr /**\todo fix this */, nullptr);
+    if (_changeSignal != nullptr) {
         _changeSignal->emit();
     }
     return;
@@ -127,7 +127,7 @@ void ParamBool::string(std::string &string) const
 Gtk::Widget *ParamBool::get_widget(SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
 
     auto hbox = Gtk::manage(new Gtk::Box(Gtk::ORIENTATION_HORIZONTAL, Parameter::GUI_PARAM_WIDGETS_SPACING));
diff --git a/src/extension/param/color.cpp b/src/extension/param/color.cpp
index 035c43ba8..1e3b1dc4c 100644
--- a/src/extension/param/color.cpp
+++ b/src/extension/param/color.cpp
@@ -60,10 +60,10 @@ ParamColor::ParamColor(const gchar * name,
                        Inkscape::Extension::Extension * ext,
                        Inkscape::XML::Node * xml)
     : Parameter(name, text, description, hidden, indent, ext)
-    , _changeSignal(0)
+    , _changeSignal(nullptr)
 {
-    const char * defaulthex = NULL;
-    if (xml->firstChild() != NULL)
+    const char * defaulthex = nullptr;
+    if (xml->firstChild() != nullptr)
         defaulthex = xml->firstChild()->content();
 
     gchar * pref_name = this->pref_name();
@@ -92,7 +92,7 @@ Gtk::Widget *ParamColor::get_widget( SPDocument * /*doc*/, Inkscape::XML::Node *
 {
     using Inkscape::UI::Widget::ColorNotebook;
 
-    if (_hidden) return NULL;
+    if (_hidden) return nullptr;
 
     if (changeSignal) {
         _changeSignal = new sigc::signal<void>(*changeSignal);
diff --git a/src/extension/param/description.cpp b/src/extension/param/description.cpp
index cf94918f7..d795514c3 100644
--- a/src/extension/param/description.cpp
+++ b/src/extension/param/description.cpp
@@ -37,15 +37,15 @@ ParamDescription::ParamDescription(const gchar * name,
                                    Inkscape::XML::Node * xml,
                                    AppearanceMode mode)
     : Parameter(name, text, description, hidden, indent, ext)
-    , _value(NULL)
+    , _value(nullptr)
     , _mode(mode)
 {
     // construct the text content by concatenating all (non-empty) text nodes,
     // removing all other nodes (e.g. comment nodes) and replacing <extension:br> elements with "<br/>"
     Glib::ustring value;
     Inkscape::XML::Node * cur_child = xml->firstChild();
-    while (cur_child != NULL) {
-        if (cur_child->type() == XML::TEXT_NODE && cur_child->content() != NULL) {
+    while (cur_child != nullptr) {
+        if (cur_child->type() == XML::TEXT_NODE && cur_child->content() != nullptr) {
             value += cur_child->content();
         } else if (cur_child->type() == XML::ELEMENT_NODE && !g_strcmp0(cur_child->name(), "extension:br")) {
             value += "<br/>";
@@ -71,8 +71,8 @@ ParamDescription::ParamDescription(const gchar * name,
     // translate if underscored version (_param) was used
     if (g_str_has_prefix(xml->name(), "extension:_")) {
         const gchar * context = xml->attribute("msgctxt");
-        if (context != NULL) {
-            value = g_dpgettext2(NULL, context, value.c_str());
+        if (context != nullptr) {
+            value = g_dpgettext2(nullptr, context, value.c_str());
         } else {
             value = _(value.c_str());
         }
@@ -91,10 +91,10 @@ Gtk::Widget *
 ParamDescription::get_widget (SPDocument * /*doc*/, Inkscape::XML::Node * /*node*/, sigc::signal<void> * /*changeSignal*/)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
-    if (_value == NULL) {
-        return NULL;
+    if (_value == nullptr) {
+        return nullptr;
     }
 
     Glib::ustring newtext = _value;
diff --git a/src/extension/param/enum.cpp b/src/extension/param/enum.cpp
index ddcbb358b..c5ee5f6b9 100644
--- a/src/extension/param/enum.cpp
+++ b/src/extension/param/enum.cpp
@@ -39,27 +39,27 @@ ParamComboBox::ParamComboBox(const gchar * name,
                              Inkscape::Extension::Extension * ext,
                              Inkscape::XML::Node * xml)
     : Parameter(name, text, description, hidden, indent, ext)
-    , _value(NULL)
+    , _value(nullptr)
 {
-    const char *xmlval = NULL; // the value stored in XML
+    const char *xmlval = nullptr; // the value stored in XML
 
-    if (xml != NULL) {
+    if (xml != nullptr) {
         // Read XML tree to add enumeration items:
         for (Inkscape::XML::Node *node = xml->firstChild(); node; node = node->next()) {
             char const * chname = node->name();
             if (!strcmp(chname, INKSCAPE_EXTENSION_NS "item") || !strcmp(chname, INKSCAPE_EXTENSION_NS "_item")) {
                 Glib::ustring newtext, newvalue;
-                const char * contents = NULL;
+                const char * contents = nullptr;
                 if (node->firstChild()) {
                     contents = node->firstChild()->content();
                 }
-                if (contents != NULL) {
+                if (contents != nullptr) {
                     // don't translate when 'item' but do translate when '_item'
                     // NOTE: internal extensions use build_from_mem and don't need _item but
                     //       still need to include if are to be localized
                     if (!strcmp(chname, INKSCAPE_EXTENSION_NS "_item")) {
-                        if (node->attribute("msgctxt") != NULL) {
-                            newtext =  g_dpgettext2(NULL, node->attribute("msgctxt"), contents);
+                        if (node->attribute("msgctxt") != nullptr) {
+                            newtext =  g_dpgettext2(nullptr, node->attribute("msgctxt"), contents);
                         } else {
                             newtext =  _(contents);
                         }
@@ -70,7 +70,7 @@ ParamComboBox::ParamComboBox(const gchar * name,
                     continue;
 
                 const char * val = node->attribute("value");
-                if (val != NULL) {
+                if (val != nullptr) {
                     newvalue = val;
                 } else {
                     newvalue = contents;
@@ -128,8 +128,8 @@ ParamComboBox::~ParamComboBox (void)
  */
 const gchar *ParamComboBox::set(const gchar * in, SPDocument * /*doc*/, Inkscape::XML::Node * /*node*/)
 {
-    if (in == NULL) {
-        return NULL; /* Can't have NULL string */
+    if (in == nullptr) {
+        return nullptr; /* Can't have NULL string */
     }
 
     Glib::ustring settext;
@@ -140,7 +140,7 @@ const gchar *ParamComboBox::set(const gchar * in, SPDocument * /*doc*/, Inkscape
         }
     }
     if (!settext.empty()) {
-        if (_value != NULL) {
+        if (_value != nullptr) {
             g_free(_value);
         }
         _value = g_strdup(settext.data());
@@ -158,7 +158,7 @@ const gchar *ParamComboBox::set(const gchar * in, SPDocument * /*doc*/, Inkscape
  */
 bool ParamComboBox::contains(const gchar * text, SPDocument const * /*doc*/, Inkscape::XML::Node const * /*node*/) const
 {
-    if (text == NULL) {
+    if (text == nullptr) {
         return false; /* Can't have NULL string */
     }
 
@@ -214,7 +214,7 @@ ParamComboBoxEntry::changed (void)
 {
     Glib::ustring data = this->get_active_text();
     _pref->set(data.c_str(), _doc, _node);
-    if (_changeSignal != NULL) {
+    if (_changeSignal != nullptr) {
         _changeSignal->emit();
     }
 }
@@ -225,7 +225,7 @@ ParamComboBoxEntry::changed (void)
 Gtk::Widget *ParamComboBox::get_widget(SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
 
     Gtk::HBox * hbox = Gtk::manage(new Gtk::HBox(false, Parameter::GUI_PARAM_WIDGETS_SPACING));
diff --git a/src/extension/param/float.cpp b/src/extension/param/float.cpp
index 1dd3f073b..aaf871068 100644
--- a/src/extension/param/float.cpp
+++ b/src/extension/param/float.cpp
@@ -40,27 +40,27 @@ ParamFloat::ParamFloat(const gchar * name,
     , _min(0.0)
     , _max(10.0)
 {
-    const gchar * defaultval = NULL;
-    if (xml->firstChild() != NULL) {
+    const gchar * defaultval = nullptr;
+    if (xml->firstChild() != nullptr) {
         defaultval = xml->firstChild()->content();
     }
-    if (defaultval != NULL) {
-        _value = g_ascii_strtod (defaultval,NULL);
+    if (defaultval != nullptr) {
+        _value = g_ascii_strtod (defaultval,nullptr);
     }
 
     const char * maxval = xml->attribute("max");
-    if (maxval != NULL) {
-        _max = g_ascii_strtod (maxval,NULL);
+    if (maxval != nullptr) {
+        _max = g_ascii_strtod (maxval,nullptr);
     }
 
     const char * minval = xml->attribute("min");
-    if (minval != NULL) {
-        _min = g_ascii_strtod (minval,NULL);
+    if (minval != nullptr) {
+        _min = g_ascii_strtod (minval,nullptr);
     }
 
     _precision = 1;
     const char * precision = xml->attribute("precision");
-    if (precision != NULL) {
+    if (precision != nullptr) {
         _precision = atoi(precision);
     }
 
@@ -136,7 +136,7 @@ public:
                 describing the parameter. */
     ParamFloatAdjustment (ParamFloat * param, SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal) :
             Gtk::Adjustment(0.0, param->min(), param->max(), 0.1, 1.0, 0), _pref(param), _doc(doc), _node(node), _changeSignal(changeSignal) {
-        this->set_value(_pref->get(NULL, NULL) /* \todo fix */);
+        this->set_value(_pref->get(nullptr, nullptr) /* \todo fix */);
         this->signal_value_changed().connect(sigc::mem_fun(this, &ParamFloatAdjustment::val_changed));
         return;
     };
@@ -154,7 +154,7 @@ void ParamFloatAdjustment::val_changed(void)
 {
     //std::cout << "Value Changed to: " << this->get_value() << std::endl;
     _pref->set(this->get_value(), _doc, _node);
-    if (_changeSignal != NULL) {
+    if (_changeSignal != nullptr) {
         _changeSignal->emit();
     }
     return;
@@ -168,7 +168,7 @@ void ParamFloatAdjustment::val_changed(void)
 Gtk::Widget * ParamFloat::get_widget(SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
 
     Gtk::HBox * hbox = Gtk::manage(new Gtk::HBox(false, Parameter::GUI_PARAM_WIDGETS_SPACING));
@@ -179,7 +179,7 @@ Gtk::Widget * ParamFloat::get_widget(SPDocument * doc, Inkscape::XML::Node * nod
     if (_mode == FULL) {
 
         Glib::ustring text;
-        if (_text != NULL)
+        if (_text != nullptr)
             text = _text;
         UI::Widget::SpinScale *scale = new UI::Widget::SpinScale(text, fadjust, _precision);
         scale->set_size_request(400, -1);
diff --git a/src/extension/param/int.cpp b/src/extension/param/int.cpp
index 9ad9b591c..1c946d8b8 100644
--- a/src/extension/param/int.cpp
+++ b/src/extension/param/int.cpp
@@ -40,21 +40,21 @@ ParamInt::ParamInt(const gchar * name,
     , _min(0)
     , _max(10)
 {
-    const char * defaultval = NULL;
-    if (xml->firstChild() != NULL) {
+    const char * defaultval = nullptr;
+    if (xml->firstChild() != nullptr) {
         defaultval = xml->firstChild()->content();
     }
-    if (defaultval != NULL) {
+    if (defaultval != nullptr) {
         _value = atoi(defaultval);
     }
 
     const char * maxval = xml->attribute("max");
-    if (maxval != NULL) {
+    if (maxval != nullptr) {
         _max = atoi(maxval);
     }
 
     const char * minval = xml->attribute("min");
-    if (minval != NULL) {
+    if (minval != nullptr) {
         _min = atoi(minval);
     }
     /* We're handling this by just killing both values */
@@ -118,7 +118,7 @@ public:
         describing the parameter. */
     ParamIntAdjustment (ParamInt * param, SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal) :
             Gtk::Adjustment(0.0, param->min(), param->max(), 1.0, 10.0, 0), _pref(param), _doc(doc), _node(node), _changeSignal(changeSignal) {
-        this->set_value(_pref->get(NULL, NULL) /* \todo fix */);
+        this->set_value(_pref->get(nullptr, nullptr) /* \todo fix */);
         this->signal_value_changed().connect(sigc::mem_fun(this, &ParamIntAdjustment::val_changed));
     };
 
@@ -135,7 +135,7 @@ void ParamIntAdjustment::val_changed(void)
 {
     //std::cout << "Value Changed to: " << this->get_value() << std::endl;
     _pref->set((int)this->get_value(), _doc, _node);
-    if (_changeSignal != NULL) {
+    if (_changeSignal != nullptr) {
         _changeSignal->emit();
     }
 }
@@ -149,7 +149,7 @@ Gtk::Widget *
 ParamInt::get_widget (SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
 
     Gtk::HBox * hbox = Gtk::manage(new Gtk::HBox(false, Parameter::GUI_PARAM_WIDGETS_SPACING));
@@ -160,7 +160,7 @@ ParamInt::get_widget (SPDocument * doc, Inkscape::XML::Node * node, sigc::signal
     if (_mode == FULL) {
 
         Glib::ustring text;
-        if (_text != NULL)
+        if (_text != nullptr)
             text = _text;
         UI::Widget::SpinScale *scale = new UI::Widget::SpinScale(text, fadjust, 0);
         scale->set_size_request(400, -1);
diff --git a/src/extension/param/notebook.cpp b/src/extension/param/notebook.cpp
index e47644f45..d00693db4 100644
--- a/src/extension/param/notebook.cpp
+++ b/src/extension/param/notebook.cpp
@@ -51,9 +51,9 @@ ParamNotebook::ParamNotebookPage::ParamNotebookPage(const gchar * name,
 {
 
     // Read XML to build page
-    if (xml != NULL) {
+    if (xml != nullptr) {
         Inkscape::XML::Node *child_repr = xml->firstChild();
-        while (child_repr != NULL) {
+        while (child_repr != nullptr) {
             char const * chname = child_repr->name();
             if (!strncmp(chname, INKSCAPE_EXTENSION_NS_NC, strlen(INKSCAPE_EXTENSION_NS_NC))) {
                 chname += strlen(INKSCAPE_EXTENSION_NS);
@@ -63,7 +63,7 @@ ParamNotebook::ParamNotebookPage::ParamNotebookPage(const gchar * name,
             if (!strcmp(chname, "param") || !strcmp(chname, "_param")) {
                 Parameter * param;
                 param = Parameter::make(child_repr, ext);
-                if (param != NULL) parameters.push_back(param);
+                if (param != nullptr) parameters.push_back(param);
             }
             child_repr = child_repr->next();
         }
@@ -122,13 +122,13 @@ ParamNotebook::ParamNotebookPage::makepage (Inkscape::XML::Node * in_repr, Inksc
 
     name = in_repr->attribute("name");
     text = in_repr->attribute("gui-text");
-    if (text == NULL)
+    if (text == nullptr)
         text = in_repr->attribute("_gui-text");
     description = in_repr->attribute("gui-description");
-    if (description == NULL)
+    if (description == nullptr)
         description = in_repr->attribute("_gui-description");
     hide = in_repr->attribute("gui-hidden");
-    if (hide != NULL) {
+    if (hide != nullptr) {
         if (strcmp(hide, "1") == 0 ||
             strcmp(hide, "true") == 0) {
                 hidden = true;
@@ -137,8 +137,8 @@ ParamNotebook::ParamNotebookPage::makepage (Inkscape::XML::Node * in_repr, Inksc
     }
 
     /* In this case we just don't have enough information */
-    if (name == NULL) {
-        return NULL;
+    if (name == nullptr) {
+        return nullptr;
     }
 
     ParamNotebookPage * page = new ParamNotebookPage(name, text, description, hidden, in_ext, in_repr);
@@ -157,7 +157,7 @@ ParamNotebook::ParamNotebookPage::makepage (Inkscape::XML::Node * in_repr, Inksc
 Gtk::Widget * ParamNotebook::ParamNotebookPage::get_widget(SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
 
     Gtk::VBox * vbox = Gtk::manage(new Gtk::VBox);
@@ -194,7 +194,7 @@ Gtk::Widget * ParamNotebook::ParamNotebookPage::get_widget(SPDocument * doc, Ink
 /** Search the parameter's name in the page content. */
 Parameter *ParamNotebook::ParamNotebookPage::get_param(const gchar * name)
 {
-    if (name == NULL) {
+    if (name == nullptr) {
         throw Extension::param_not_exist();
     }
     if (this->parameters.empty()) {
@@ -208,7 +208,7 @@ Parameter *ParamNotebook::ParamNotebookPage::get_param(const gchar * name)
         }
     }
 
-    return NULL;
+    return nullptr;
 }
 
 /** End ParamNotebookPage **/
@@ -224,9 +224,9 @@ ParamNotebook::ParamNotebook(const gchar * name,
     : Parameter(name, text, description, hidden, indent, ext)
 {
     // Read XML tree to add pages:
-    if (xml != NULL) {
+    if (xml != nullptr) {
         Inkscape::XML::Node *child_repr = xml->firstChild();
-        while (child_repr != NULL) {
+        while (child_repr != nullptr) {
             char const * chname = child_repr->name();
             if (!strncmp(chname, INKSCAPE_EXTENSION_NS_NC, strlen(INKSCAPE_EXTENSION_NS_NC))) {
                 chname += strlen(INKSCAPE_EXTENSION_NS);
@@ -236,14 +236,14 @@ ParamNotebook::ParamNotebook(const gchar * name,
             if (!strcmp(chname, "page")) {
                 ParamNotebookPage * page;
                 page = ParamNotebookPage::makepage(child_repr, ext);
-                if (page != NULL) pages.push_back(page);
+                if (page != nullptr) pages.push_back(page);
             }
             child_repr = child_repr->next();
         }
     }
 
     // Initialize _value with the current page
-    const char * defaultval = NULL;
+    const char * defaultval = nullptr;
     // set first page as default
     if (!pages.empty()) {
         defaultval = pages[0]->name();
@@ -256,7 +256,7 @@ ParamNotebook::ParamNotebook(const gchar * name,
 
     if (!paramval.empty())
         defaultval = paramval.data();
-    if (defaultval != NULL)
+    if (defaultval != nullptr)
         _value = g_strdup(defaultval);  // allocate space for _value
 }
 
@@ -290,9 +290,9 @@ const gchar *ParamNotebook::set(const int in, SPDocument * /*doc*/, Inkscape::XM
     int i = in < pages.size() ? in : pages.size()-1;
     ParamNotebookPage * page = pages[i];
 
-    if (page == NULL) return _value;
+    if (page == nullptr) return _value;
 
-    if (_value != NULL) g_free(_value);
+    if (_value != nullptr) g_free(_value);
     _value = g_strdup(page->name());
 
     gchar * prefname = this->pref_name();
@@ -359,7 +359,7 @@ void ParamNotebookWdg::changed_page(Gtk::Widget * /*page*/, guint pagenum)
 /** Search the parameter's name in the notebook content. */
 Parameter *ParamNotebook::get_param(const gchar * name)
 {
-    if (name == NULL) {
+    if (name == nullptr) {
         throw Extension::param_not_exist();
     }
     for (auto page:pages) {
@@ -369,7 +369,7 @@ Parameter *ParamNotebook::get_param(const gchar * name)
         }
     }
 
-    return NULL;
+    return nullptr;
 }
 
 
@@ -381,7 +381,7 @@ Parameter *ParamNotebook::get_param(const gchar * name)
 Gtk::Widget * ParamNotebook::get_widget(SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
 
     ParamNotebookWdg * nb = Gtk::manage(new ParamNotebookWdg(this, doc, node));
diff --git a/src/extension/param/parameter.cpp b/src/extension/param/parameter.cpp
index f9a69de05..d897903cb 100644
--- a/src/extension/param/parameter.cpp
+++ b/src/extension/param/parameter.cpp
@@ -52,37 +52,37 @@ Parameter *Parameter::make(Inkscape::XML::Node *in_repr, Inkscape::Extension::Ex
 
     // we can't create a parameter without type
     if (!type) {
-        return NULL;
+        return nullptr;
     }
     // also require name unless it's a pure UI element that does not store its value
     if (!name) {
         static std::vector<std::string> ui_elements = {"description"};
         if (std::find(ui_elements.begin(), ui_elements.end(), type) == ui_elements.end()) {
-            return NULL;
+            return nullptr;
         }
     }
 
     const char *text = in_repr->attribute("gui-text");
-    if (text == NULL) {
+    if (text == nullptr) {
         text = in_repr->attribute("_gui-text");
-        if (text == NULL) {
+        if (text == nullptr) {
             // text = ""; // probably better to require devs to explicitly set an empty gui-text if this is what they want
         } else {
             const char *context = in_repr->attribute("msgctxt");
-            if (context != NULL) {
-                text = g_dpgettext2(NULL, context, text);
+            if (context != nullptr) {
+                text = g_dpgettext2(nullptr, context, text);
             } else {
                 text = _(text);
             }
         }
     }
     const char *description = in_repr->attribute("gui-description");
-    if (description == NULL) {
+    if (description == nullptr) {
         description = in_repr->attribute("_gui-description");
-        if (description != NULL) {
+        if (description != nullptr) {
             const char *context = in_repr->attribute("msgctxt");
-            if (context != NULL) {
-                description = g_dpgettext2(NULL, context, description);
+            if (context != nullptr) {
+                description = g_dpgettext2(nullptr, context, description);
             } else {
                 description = _(description);
             }
@@ -91,7 +91,7 @@ Parameter *Parameter::make(Inkscape::XML::Node *in_repr, Inkscape::Extension::Ex
     bool hidden = false;
     {
         const char *gui_hide = in_repr->attribute("gui-hidden");
-        if (gui_hide != NULL) {
+        if (gui_hide != nullptr) {
             if (strcmp(gui_hide, "1") == 0 ||
                 strcmp(gui_hide, "true") == 0) {
                 hidden = true;
@@ -102,7 +102,7 @@ Parameter *Parameter::make(Inkscape::XML::Node *in_repr, Inkscape::Extension::Ex
     int indent = 0;
     {
         const char *indent_attr = in_repr->attribute("indent");
-        if (indent_attr != NULL) {
+        if (indent_attr != nullptr) {
             if (strcmp(indent_attr, "true") == 0) {
                 indent = 1;
             } else {
@@ -112,7 +112,7 @@ Parameter *Parameter::make(Inkscape::XML::Node *in_repr, Inkscape::Extension::Ex
     }
     const gchar* appearance = in_repr->attribute("appearance");
 
-    Parameter * param = NULL;
+    Parameter * param = nullptr;
     if (!strcmp(type, "boolean")) {
         param = new ParamBool(name, text, description, hidden, indent, in_ext, in_repr);
     } else if (!strcmp(type, "int")) {
@@ -130,7 +130,7 @@ Parameter *Parameter::make(Inkscape::XML::Node *in_repr, Inkscape::Extension::Ex
     } else if (!strcmp(type, "string")) {
         param = new ParamString(name, text, description, hidden, indent, in_ext, in_repr);
         gchar const * max_length = in_repr->attribute("max_length");
-        if (max_length != NULL) {
+        if (max_length != nullptr) {
             ParamString * ps = dynamic_cast<ParamString *>(param);
             ps->setMaxLength(atoi(max_length));
         }
@@ -237,7 +237,7 @@ guint32 Parameter::get_color(const SPDocument* doc, Inkscape::XML::Node const *n
 bool Parameter::set_bool(bool in, SPDocument * doc, Inkscape::XML::Node * node)
 {
     ParamBool * boolpntr = dynamic_cast<ParamBool *>(this);
-    if (boolpntr == NULL)
+    if (boolpntr == nullptr)
         throw Extension::param_not_bool_param();
     return boolpntr->set(in, doc, node);
 }
@@ -245,7 +245,7 @@ bool Parameter::set_bool(bool in, SPDocument * doc, Inkscape::XML::Node * node)
 int Parameter::set_int(int in, SPDocument * doc, Inkscape::XML::Node * node)
 {
     ParamInt * intpntr = dynamic_cast<ParamInt *>(this);
-    if (intpntr == NULL)
+    if (intpntr == nullptr)
         throw Extension::param_not_int_param();
     return intpntr->set(in, doc, node);
 }
@@ -256,7 +256,7 @@ Parameter::set_float (float in, SPDocument * doc, Inkscape::XML::Node * node)
 {
     ParamFloat * floatpntr;
     floatpntr = dynamic_cast<ParamFloat *>(this);
-    if (floatpntr == NULL)
+    if (floatpntr == nullptr)
         throw Extension::param_not_float_param();
     return floatpntr->set(in, doc, node);
 }
@@ -266,7 +266,7 @@ gchar const *
 Parameter::set_string (gchar const * in, SPDocument * doc, Inkscape::XML::Node * node)
 {
     ParamString * stringpntr = dynamic_cast<ParamString *>(this);
-    if (stringpntr == NULL)
+    if (stringpntr == nullptr)
         throw Extension::param_not_string_param();
     return stringpntr->set(in, doc, node);
 }
@@ -295,7 +295,7 @@ guint32
 Parameter::set_color (guint32 in, SPDocument * doc, Inkscape::XML::Node * node)
 {
     ParamColor* param = dynamic_cast<ParamColor *>(this);
-    if (param == NULL)
+    if (param == nullptr)
         throw Extension::param_not_color_param();
     return param->set(in, doc, node);
 }
@@ -303,22 +303,22 @@ Parameter::set_color (guint32 in, SPDocument * doc, Inkscape::XML::Node * node)
 
 /** Oop, now that we need a parameter, we need it's name. */
 Parameter::Parameter(gchar const * name, gchar const * text, gchar const * description, bool hidden, int indent, Inkscape::Extension::Extension * ext) :
-    _description(0),
-    _text(0),
+    _description(nullptr),
+    _text(nullptr),
     _hidden(hidden),
     _indent(indent),
     _extension(ext),
-    _name(0)
+    _name(nullptr)
 {
-    if (name != NULL) {
+    if (name != nullptr) {
         _name = g_strdup(name);
     }
 
-    if (description != NULL) {
+    if (description != nullptr) {
         _description = g_strdup(description);
     }
 
-    if (text != NULL) {
+    if (text != nullptr) {
         _text = g_strdup(text);
     } else {
         _text = g_strdup(name);
@@ -329,17 +329,17 @@ Parameter::Parameter(gchar const * name, gchar const * text, gchar const * descr
 
 /** Oop, now that we need a parameter, we need it's name. */
 Parameter::Parameter (gchar const * name, gchar const * text, Inkscape::Extension::Extension * ext) :
-    _description(0),
-    _text(0),
+    _description(nullptr),
+    _text(nullptr),
     _hidden(false),
     _indent(0),
     _extension(ext),
-    _name(0)
+    _name(nullptr)
 {
-    if (name != NULL) {
+    if (name != nullptr) {
         _name = g_strdup(name);
     }
-    if (text != NULL) {
+    if (text != nullptr) {
         _text = g_strdup(text);
     } else {
         _text = g_strdup(name);
@@ -351,13 +351,13 @@ Parameter::Parameter (gchar const * name, gchar const * text, Inkscape::Extensio
 Parameter::~Parameter(void)
 {
     g_free(_name);
-    _name = 0;
+    _name = nullptr;
 
     g_free(_text);
-    _text = 0;
+    _text = nullptr;
 
     g_free(_description);
-    _description = 0;
+    _description = nullptr;
 }
 
 gchar *Parameter::pref_name(void) const
@@ -387,12 +387,12 @@ Inkscape::XML::Node *Parameter::document_param_node(SPDocument * doc)
 {
     Inkscape::XML::Document *xml_doc = doc->getReprDoc();
     Inkscape::XML::Node * defs = doc->getDefs()->getRepr();
-    Inkscape::XML::Node * params = NULL;
+    Inkscape::XML::Node * params = nullptr;
 
     GQuark const name_quark = g_quark_from_string("inkscape:extension-params");
 
     for (Inkscape::XML::Node * child = defs->firstChild();
-            child != NULL;
+            child != nullptr;
             child = child->next()) {
         if ((GQuark)child->code() == name_quark &&
                 !strcmp(child->attribute("extension"), _extension->get_id())) {
@@ -401,7 +401,7 @@ Inkscape::XML::Node *Parameter::document_param_node(SPDocument * doc)
         }
     }
 
-    if (params == NULL) {
+    if (params == nullptr) {
         params = xml_doc->createElement("inkscape:extension-param");
         params->setAttribute("extension", _extension->get_id());
         defs->appendChild(params);
@@ -415,7 +415,7 @@ Inkscape::XML::Node *Parameter::document_param_node(SPDocument * doc)
 Gtk::Widget *
 Parameter::get_widget (SPDocument * /*doc*/, Inkscape::XML::Node * /*node*/, sigc::signal<void> * /*changeSignal*/)
 {
-    return NULL;
+    return nullptr;
 }
 
 /** If I'm not sure which it is, just don't return a value. */
@@ -441,7 +441,7 @@ void Parameter::string(std::list <std::string> &list) const
 
 Parameter *Parameter::get_param(gchar const * /*name*/)
 {
-    return NULL;
+    return nullptr;
 }
 
 Glib::ustring const extension_pref_root = "/extensions/";
diff --git a/src/extension/param/radiobutton.cpp b/src/extension/param/radiobutton.cpp
index 5598081f3..45869378a 100644
--- a/src/extension/param/radiobutton.cpp
+++ b/src/extension/param/radiobutton.cpp
@@ -51,25 +51,25 @@ ParamRadioButton::ParamRadioButton(const gchar * name,
                                    Inkscape::XML::Node * xml,
                                    AppearanceMode mode)
     : Parameter(name, text, description, hidden, indent, ext)
-    , _value(0)
+    , _value(nullptr)
     , _mode(mode)
 {
     // Read XML tree to add enumeration items:
     // printf("Extension Constructor: ");
-    if (xml != NULL) {
+    if (xml != nullptr) {
         Inkscape::XML::Node *child_repr = xml->firstChild();
-        while (child_repr != NULL) {
+        while (child_repr != nullptr) {
             char const * chname = child_repr->name();
             if (!strcmp(chname, INKSCAPE_EXTENSION_NS "option") || !strcmp(chname, INKSCAPE_EXTENSION_NS "_option")) {
-                Glib::ustring * newtext = NULL;
-                Glib::ustring * newvalue = NULL;
+                Glib::ustring * newtext = nullptr;
+                Glib::ustring * newvalue = nullptr;
                 const char * contents = child_repr->firstChild()->content();
 
-                if (contents != NULL) {
+                if (contents != nullptr) {
                     // don't translate when 'item' but do translate when '_option'
                     if (!strcmp(chname, INKSCAPE_EXTENSION_NS "_option")) {
-                        if (child_repr->attribute("msgctxt") != NULL) {
-                            newtext =  new Glib::ustring(g_dpgettext2(NULL, child_repr->attribute("msgctxt"), contents));
+                        if (child_repr->attribute("msgctxt") != nullptr) {
+                            newtext =  new Glib::ustring(g_dpgettext2(nullptr, child_repr->attribute("msgctxt"), contents));
                         } else {
                             newtext =  new Glib::ustring(_(contents));
                         }
@@ -82,7 +82,7 @@ ParamRadioButton::ParamRadioButton(const gchar * name,
 
 
                 const char * val = child_repr->attribute("value");
-                if (val != NULL) {
+                if (val != nullptr) {
                     newvalue = new Glib::ustring(val);
                 } else {
                     newvalue = new Glib::ustring(contents);
@@ -98,7 +98,7 @@ ParamRadioButton::ParamRadioButton(const gchar * name,
 
     // Initialize _value with the default value from xml
     // for simplicity : default to the contents of the first xml-child
-    const char * defaultval = NULL;
+    const char * defaultval = nullptr;
     if (!choices.empty()) {
         defaultval = (static_cast<optionentry*> (choices[0]))->value->c_str();
     }
@@ -111,7 +111,7 @@ ParamRadioButton::ParamRadioButton(const gchar * name,
     if (!paramval.empty()) {
         defaultval = paramval.data();
     }
-    if (defaultval != NULL) {
+    if (defaultval != nullptr) {
         _value = g_strdup(defaultval);  // allocate space for _value
     }
 }
@@ -143,11 +143,11 @@ ParamRadioButton::~ParamRadioButton (void)
  */
 const gchar *ParamRadioButton::set(const gchar * in, SPDocument * /*doc*/, Inkscape::XML::Node * /*node*/)
 {
-    if (in == NULL) {
-        return NULL; /* Can't have NULL string */
+    if (in == nullptr) {
+        return nullptr; /* Can't have NULL string */
     }
 
-    Glib::ustring * settext = NULL;
+    Glib::ustring * settext = nullptr;
     for (auto entr:choices) {
         if ( !entr->value->compare(in) ) {
             settext = entr->value;
@@ -155,7 +155,7 @@ const gchar *ParamRadioButton::set(const gchar * in, SPDocument * /*doc*/, Inksc
         }
     }
     if (settext) {
-        if (_value != NULL) {
+        if (_value != nullptr) {
             g_free(_value);
         }
         _value = g_strdup(settext->c_str());
@@ -215,7 +215,7 @@ void ParamRadioButtonWdg::changed(void)
         Glib::ustring value = _pref->value_from_label(this->get_label());
         _pref->set(value.c_str(), _doc, _node);
     }
-    if (_changeSignal != NULL) {
+    if (_changeSignal != nullptr) {
         _changeSignal->emit();
     }
 }
@@ -247,7 +247,7 @@ void ComboWdg::changed(void)
             Glib::ustring value = _base->value_from_label(get_active_text());
             _base->set(value.c_str(), _doc, _node);
     }
-    if (_changeSignal != NULL) {
+    if (_changeSignal != nullptr) {
         _changeSignal->emit();
     }
 }
@@ -276,7 +276,7 @@ Glib::ustring ParamRadioButton::value_from_label(const Glib::ustring label)
 Gtk::Widget * ParamRadioButton::get_widget(SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
 
     auto hbox = Gtk::manage(new Gtk::Box(Gtk::ORIENTATION_HORIZONTAL, Parameter::GUI_PARAM_WIDGETS_SPACING));
@@ -288,7 +288,7 @@ Gtk::Widget * ParamRadioButton::get_widget(SPDocument * doc, Inkscape::XML::Node
     label->show();
     hbox->pack_start(*label, false, false);
 
-    Gtk::ComboBoxText* cbt = 0;
+    Gtk::ComboBoxText* cbt = nullptr;
     bool comboSet = false;
     if (_mode == MINIMAL) {
         cbt = Gtk::manage(new ComboWdg(this, doc, node, changeSignal));
diff --git a/src/extension/param/string.cpp b/src/extension/param/string.cpp
index 51b5dfdf3..775bf62ee 100644
--- a/src/extension/param/string.cpp
+++ b/src/extension/param/string.cpp
@@ -30,7 +30,7 @@ namespace Extension {
 ParamString::~ParamString(void)
 {
     g_free(_value);
-    _value = 0;
+    _value = nullptr;
 }
 
 /**
@@ -50,11 +50,11 @@ ParamString::~ParamString(void)
  */
 const gchar * ParamString::set(const gchar * in, SPDocument * /*doc*/, Inkscape::XML::Node * /*node*/)
 {
-    if (in == NULL) {
-        return NULL; /* Can't have NULL string */
+    if (in == nullptr) {
+        return nullptr; /* Can't have NULL string */
     }
 
-    if (_value != NULL) {
+    if (_value != nullptr) {
         g_free(_value);
     }
 
@@ -84,10 +84,10 @@ ParamString::ParamString(const gchar * name,
                          Inkscape::Extension::Extension * ext,
                          Inkscape::XML::Node * xml)
     : Parameter(name, text, description, hidden, indent, ext)
-    , _value(NULL)
+    , _value(nullptr)
 {
-    const char * defaultval = NULL;
-    if (xml->firstChild() != NULL) {
+    const char * defaultval = nullptr;
+    if (xml->firstChild() != nullptr) {
         defaultval = xml->firstChild()->content();
     }
 
@@ -99,11 +99,11 @@ ParamString::ParamString(const gchar * name,
     if (!paramval.empty()) {
         defaultval = paramval.data();
     }
-    if (defaultval != NULL) {
+    if (defaultval != nullptr) {
         char const * chname = xml->name();
         if (!strcmp(chname, INKSCAPE_EXTENSION_NS "_param")) {
-            if (xml->attribute("msgctxt") != NULL) {
-                _value =  g_strdup(g_dpgettext2(NULL, xml->attribute("msgctxt"), defaultval));
+            if (xml->attribute("msgctxt") != nullptr) {
+                _value =  g_strdup(g_dpgettext2(nullptr, xml->attribute("msgctxt"), defaultval));
             } else {
                 _value = g_strdup(_(defaultval));
             }
@@ -130,8 +130,8 @@ public:
      */
     ParamStringEntry (ParamString * pref, SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal) :
         Gtk::Entry(), _pref(pref), _doc(doc), _node(node), _changeSignal(changeSignal) {
-        if (_pref->get(NULL, NULL) != NULL) {
-            this->set_text(Glib::ustring(_pref->get(NULL, NULL)));
+        if (_pref->get(nullptr, nullptr) != nullptr) {
+            this->set_text(Glib::ustring(_pref->get(nullptr, nullptr)));
         }
         this->set_max_length(_pref->getMaxLength()); //Set the max length - default zero means no maximum
         this->signal_changed().connect(sigc::mem_fun(this, &ParamStringEntry::changed_text));
@@ -150,7 +150,7 @@ void ParamStringEntry::changed_text(void)
 {
     Glib::ustring data = this->get_text();
     _pref->set(data.c_str(), _doc, _node);
-    if (_changeSignal != NULL) {
+    if (_changeSignal != nullptr) {
         _changeSignal->emit();
     }
 }
@@ -163,7 +163,7 @@ void ParamStringEntry::changed_text(void)
 Gtk::Widget * ParamString::get_widget(SPDocument * doc, Inkscape::XML::Node * node, sigc::signal<void> * changeSignal)
 {
     if (_hidden) {
-        return NULL;
+        return nullptr;
     }
 
     Gtk::HBox * hbox = Gtk::manage(new Gtk::HBox(false, Parameter::GUI_PARAM_WIDGETS_SPACING));
diff --git a/src/extension/patheffect.cpp b/src/extension/patheffect.cpp
index 1e9e093ef..82d75dcb3 100644
--- a/src/extension/patheffect.cpp
+++ b/src/extension/patheffect.cpp
@@ -39,33 +39,33 @@ void
 PathEffect::processPathEffects (SPDocument * doc, Inkscape::XML::Node * path)
 {
     gchar const * patheffectlist = path->attribute("inkscape:path-effects");
-    if (patheffectlist == NULL)
+    if (patheffectlist == nullptr)
         return;
 
     gchar ** patheffects = g_strsplit(patheffectlist, ";", 128);
     Inkscape::XML::Node * defs = doc->getDefs()->getRepr();
 
-    for (int i = 0; (i < 128) && (patheffects[i] != NULL); i++) {
+    for (int i = 0; (i < 128) && (patheffects[i] != nullptr); i++) {
         gchar * patheffect = patheffects[i];
 
         // This is weird, they should all be references... but anyway
         if (patheffect[0] != '#') continue;
 
         Inkscape::XML::Node * prefs = sp_repr_lookup_child(defs, "id", &(patheffect[1]));
-        if (prefs == NULL) {
+        if (prefs == nullptr) {
 
             continue;
         }
 
         gchar const * ext_id = prefs->attribute("extension");
-        if (ext_id == NULL) {
+        if (ext_id == nullptr) {
 
             continue;
         }
 
         Inkscape::Extension::PathEffect * peffect;
         peffect = dynamic_cast<Inkscape::Extension::PathEffect *>(Inkscape::Extension::db.get(ext_id));
-        if (peffect != NULL) {
+        if (peffect != nullptr) {
             peffect->processPath(doc, path, prefs);
         }
     }
diff --git a/src/extension/plugins/grid2/grid.cpp b/src/extension/plugins/grid2/grid.cpp
index 256bb8dc2..3ebe85b3e 100644
--- a/src/extension/plugins/grid2/grid.cpp
+++ b/src/extension/plugins/grid2/grid.cpp
@@ -187,7 +187,7 @@ Grid::prefs_effect(Inkscape::Extension::Effect *module, Inkscape::UI::View::View
     SPDocument * current_document = view->doc();
 
     auto selected = ((SPDesktop *) view)->getSelection()->items();
-    Inkscape::XML::Node * first_select = NULL;
+    Inkscape::XML::Node * first_select = nullptr;
     if (!selected.empty()) {
         first_select = selected.front()->getRepr();
     }
diff --git a/src/extension/prefdialog.cpp b/src/extension/prefdialog.cpp
index b5b1f9bfe..47ed14405 100644
--- a/src/extension/prefdialog.cpp
+++ b/src/extension/prefdialog.cpp
@@ -45,22 +45,22 @@ PrefDialog::PrefDialog (Glib::ustring name, gchar const * help, Gtk::Widget * co
     Gtk::Dialog(_(name.c_str()), true),
     _help(help),
     _name(name),
-    _button_ok(NULL),
-    _button_cancel(NULL),
-    _button_preview(NULL),
-    _param_preview(NULL),
+    _button_ok(nullptr),
+    _button_cancel(nullptr),
+    _button_preview(nullptr),
+    _param_preview(nullptr),
     _effect(effect),
-    _exEnv(NULL)
+    _exEnv(nullptr)
 {
     this->set_default_size(0,0);  // we want the window to be as small as possible instead of clobbering up space
 
     Gtk::HBox * hbox = Gtk::manage(new Gtk::HBox());
-    if (controls == NULL) {
-        if (_effect == NULL) {
+    if (controls == nullptr) {
+        if (_effect == nullptr) {
             std::cout << "AH!!!  No controls and no effect!!!" << std::endl;
             return;
         }
-        controls = _effect->get_imp()->prefs_effect(_effect, SP_ACTIVE_DESKTOP, &_signal_param_change, NULL);
+        controls = _effect->get_imp()->prefs_effect(_effect, SP_ACTIVE_DESKTOP, &_signal_param_change, nullptr);
         _signal_param_change.connect(sigc::mem_fun(this, &PrefDialog::param_change));
     }
 
@@ -74,15 +74,15 @@ PrefDialog::PrefDialog (Glib::ustring name, gchar const * help, Gtk::Widget * co
     if (_help == NULL)
         help_button->set_sensitive(false);
     */
-    _button_cancel = add_button(_effect == NULL ? _("_Cancel") : _("_Close"), Gtk::RESPONSE_CANCEL);
-    _button_ok     = add_button(_effect == NULL ? _("_OK")     : _("_Apply"), Gtk::RESPONSE_OK);
+    _button_cancel = add_button(_effect == nullptr ? _("_Cancel") : _("_Close"), Gtk::RESPONSE_CANCEL);
+    _button_ok     = add_button(_effect == nullptr ? _("_OK")     : _("_Apply"), Gtk::RESPONSE_OK);
     set_default_response(Gtk::RESPONSE_OK);
     _button_ok->grab_focus();
 
-    if (_effect != NULL && !_effect->no_live_preview) {
-        if (_param_preview == NULL) {
-            XML::Document * doc = sp_repr_read_mem(live_param_xml, strlen(live_param_xml), NULL);
-            if (doc == NULL) {
+    if (_effect != nullptr && !_effect->no_live_preview) {
+        if (_param_preview == nullptr) {
+            XML::Document * doc = sp_repr_read_mem(live_param_xml, strlen(live_param_xml), nullptr);
+            if (doc == nullptr) {
                 std::cout << "Error encountered loading live parameter XML !!!" << std::endl;
                 return;
             }
@@ -96,7 +96,7 @@ PrefDialog::PrefDialog (Glib::ustring name, gchar const * help, Gtk::Widget * co
 
         hbox = Gtk::manage(new Gtk::HBox());
         hbox->set_border_width(Parameter::GUI_BOX_MARGIN);
-        _button_preview = _param_preview->get_widget(NULL, NULL, &_signal_preview);
+        _button_preview = _param_preview->get_widget(nullptr, nullptr, &_signal_preview);
         _button_preview->show();
         hbox->pack_start(*_button_preview, true, true, 0);
         hbox->show();
@@ -104,7 +104,7 @@ PrefDialog::PrefDialog (Glib::ustring name, gchar const * help, Gtk::Widget * co
         this->get_content_area()->pack_start(*hbox, false, false, 0);
 
         Gtk::Box * hbox = dynamic_cast<Gtk::Box *>(_button_preview);
-        if (hbox != NULL) {
+        if (hbox != nullptr) {
             _checkbox_preview = dynamic_cast<Gtk::CheckButton *>(hbox->get_children().front());
         }
 
@@ -113,7 +113,7 @@ PrefDialog::PrefDialog (Glib::ustring name, gchar const * help, Gtk::Widget * co
     }
 
     // Set window modality for effects that don't use live preview
-    if (_effect != NULL && _effect->no_live_preview) {
+    if (_effect != nullptr && _effect->no_live_preview) {
         set_modal(false);
     }
 
@@ -125,20 +125,20 @@ PrefDialog::PrefDialog (Glib::ustring name, gchar const * help, Gtk::Widget * co
 
 PrefDialog::~PrefDialog ( )
 {
-    if (_param_preview != NULL) {
+    if (_param_preview != nullptr) {
         delete _param_preview;
-        _param_preview = NULL;
+        _param_preview = nullptr;
     }
 
-    if (_exEnv != NULL) {
+    if (_exEnv != nullptr) {
         _exEnv->cancel();
         delete _exEnv;
-        _exEnv = NULL;
+        _exEnv = nullptr;
         _effect->set_execution_env(_exEnv);
     }
 
-    if (_effect != NULL) {
-        _effect->set_pref_dialog(NULL);
+    if (_effect != nullptr) {
+        _effect->set_pref_dialog(nullptr);
     }
 
     return;
@@ -176,21 +176,21 @@ PrefDialog::preview_toggle (void) {
     SPDesktop *desktop = SP_ACTIVE_DESKTOP;
     SPDocument *document = SP_ACTIVE_DOCUMENT;
     bool modified = document->isModifiedSinceSave();
-    if(_param_preview->get_bool(NULL, NULL)) {
-        if (_exEnv == NULL) {
+    if(_param_preview->get_bool(nullptr, nullptr)) {
+        if (_exEnv == nullptr) {
             set_modal(true);
-            _exEnv = new ExecutionEnv(_effect, SP_ACTIVE_DESKTOP, NULL, false, false);
+            _exEnv = new ExecutionEnv(_effect, SP_ACTIVE_DESKTOP, nullptr, false, false);
             _effect->set_execution_env(_exEnv);
             _exEnv->run();
         }
     } else {
         set_modal(false);
-        if (_exEnv != NULL) {
+        if (_exEnv != nullptr) {
             _exEnv->cancel();
             _exEnv->undo();
             _exEnv->reselect();
             delete _exEnv;
-            _exEnv = NULL;
+            _exEnv = nullptr;
             _effect->set_execution_env(_exEnv);
         }
     }
@@ -199,7 +199,7 @@ PrefDialog::preview_toggle (void) {
 
 void
 PrefDialog::param_change (void) {
-    if (_exEnv != NULL) {
+    if (_exEnv != nullptr) {
         if (!_effect->loaded()) {
             _effect->set_state(Extension::STATE_LOADED);
         }
@@ -214,7 +214,7 @@ PrefDialog::param_change (void) {
 
 bool
 PrefDialog::param_timer_expire (void) {
-    if (_exEnv != NULL) {
+    if (_exEnv != nullptr) {
         _exEnv->cancel();
         _exEnv->undo();
         _exEnv->run();
@@ -226,8 +226,8 @@ PrefDialog::param_timer_expire (void) {
 void
 PrefDialog::on_response (int signal) {
     if (signal == Gtk::RESPONSE_OK) {
-        if (_exEnv == NULL) {
-			if (_effect != NULL) {
+        if (_exEnv == nullptr) {
+			if (_effect != nullptr) {
 				_effect->effect(SP_ACTIVE_DESKTOP);
 			} else {
 				// Shutdown run()
@@ -241,16 +241,16 @@ PrefDialog::on_response (int signal) {
                 _exEnv->reselect();
             }
             delete _exEnv;
-            _exEnv = NULL;
+            _exEnv = nullptr;
             _effect->set_execution_env(_exEnv);
         }
     }
 
-    if (_param_preview != NULL) {
+    if (_param_preview != nullptr) {
         _checkbox_preview->set_active(false);
     }
 
-    if ((signal == Gtk::RESPONSE_CANCEL || signal == Gtk::RESPONSE_DELETE_EVENT) && _effect != NULL) {
+    if ((signal == Gtk::RESPONSE_CANCEL || signal == Gtk::RESPONSE_DELETE_EVENT) && _effect != nullptr) {
         delete this;
     }
     return;
diff --git a/src/extension/prefdialog.h b/src/extension/prefdialog.h
index 0c0bfcb88..f2ff60770 100644
--- a/src/extension/prefdialog.h
+++ b/src/extension/prefdialog.h
@@ -71,8 +71,8 @@ class PrefDialog : public Gtk::Dialog {
 public:
     PrefDialog (Glib::ustring name,
                 gchar const * help,
-                Gtk::Widget * controls = NULL,
-                Effect * effect = NULL);
+                Gtk::Widget * controls = nullptr,
+                Effect * effect = nullptr);
     ~PrefDialog () override;
 };
 
diff --git a/src/extension/print.cpp b/src/extension/print.cpp
index c37e9425c..ad9836a66 100644
--- a/src/extension/print.cpp
+++ b/src/extension/print.cpp
@@ -17,9 +17,9 @@ namespace Extension {
 
 Print::Print (Inkscape::XML::Node *in_repr, Implementation::Implementation *in_imp)
     : Extension(in_repr, in_imp)
-    , base(NULL)
-    , drawing(NULL)
-    , root(NULL)
+    , base(nullptr)
+    , drawing(nullptr)
+    , root(nullptr)
     , dkey(0)
 {
 }
diff --git a/src/extension/system.cpp b/src/extension/system.cpp
index 5b039948a..6802050b0 100644
--- a/src/extension/system.cpp
+++ b/src/extension/system.cpp
@@ -70,9 +70,9 @@ static Extension *build_from_reprdoc(Inkscape::XML::Document *doc, Implementatio
  */
 SPDocument *open(Extension *key, gchar const *filename)
 {
-    Input *imod = NULL;
+    Input *imod = nullptr;
 
-    if (key == NULL) {
+    if (key == nullptr) {
         gpointer parray[2];
         parray[0] = (gpointer)filename;
         parray[1] = (gpointer)&imod;
@@ -82,12 +82,12 @@ SPDocument *open(Extension *key, gchar const *filename)
     }
 
     bool last_chance_svg = false;
-    if (key == NULL && imod == NULL) {
+    if (key == nullptr && imod == nullptr) {
         last_chance_svg = true;
         imod = dynamic_cast<Input *>(db.get(SP_MODULE_KEY_INPUT_SVG));
     }
 
-    if (imod == NULL) {
+    if (imod == nullptr) {
         throw Input::no_extension_found();
     }
 
@@ -119,7 +119,7 @@ SPDocument *open(Extension *key, gchar const *filename)
     }
 
     if (!imod->prefs(filename)) {
-        return NULL;
+        return nullptr;
     }
 
     SPDocument *doc = imod->open(filename);
@@ -219,21 +219,21 @@ save(Extension *key, SPDocument *doc, gchar const *filename, bool setextension,
     Inkscape::Extension::FileSaveMethod save_method)
 {
     Output *omod;
-    if (key == NULL) {
+    if (key == nullptr) {
         gpointer parray[2];
         parray[0] = (gpointer)filename;
         parray[1] = (gpointer)&omod;
-        omod = NULL;
+        omod = nullptr;
         db.foreach(save_internal, (gpointer)&parray);
 
         /* This is a nasty hack, but it is required to ensure that
            autodetect will always save with the Inkscape extensions
            if they are available. */
-        if (omod != NULL && !strcmp(omod->get_id(), SP_MODULE_KEY_OUTPUT_SVG)) {
+        if (omod != nullptr && !strcmp(omod->get_id(), SP_MODULE_KEY_OUTPUT_SVG)) {
             omod = dynamic_cast<Output *>(db.get(SP_MODULE_KEY_OUTPUT_SVG_INKSCAPE));
         }
         /* If autodetect fails, save as Inkscape SVG */
-        if (omod == NULL) {
+        if (omod == nullptr) {
             // omod = dynamic_cast<Output *>(db.get(SP_MODULE_KEY_OUTPUT_SVG_INKSCAPE)); use exception and let user choose
         }
     } else {
@@ -254,7 +254,7 @@ save(Extension *key, SPDocument *doc, gchar const *filename, bool setextension,
         throw Output::save_cancelled();
     }
 
-    gchar *fileName = NULL;
+    gchar *fileName = nullptr;
     if (setextension) {
         gchar *lowerfile = g_utf8_strdown(filename, -1);
         gchar *lowerext = g_utf8_strdown(omod->get_extension(), -1);
@@ -267,7 +267,7 @@ save(Extension *key, SPDocument *doc, gchar const *filename, bool setextension,
         g_free(lowerext);
     }
 
-    if (fileName == NULL) {
+    if (fileName == nullptr) {
         fileName = g_strdup(filename);
     }
 
@@ -288,8 +288,8 @@ save(Extension *key, SPDocument *doc, gchar const *filename, bool setextension,
 
     // remember attributes in case this is an unofficial save and/or overwrite fails
     gchar *saved_uri = g_strdup(doc->getURI());
-    gchar *saved_output_extension = NULL;
-    gchar *saved_dataloss = NULL;
+    gchar *saved_output_extension = nullptr;
+    gchar *saved_dataloss = nullptr;
     bool saved_modified = doc->isModifiedSinceSave();
     saved_output_extension = g_strdup(get_file_save_extension(save_method).c_str());
     saved_dataloss = g_strdup(repr->attribute("inkscape:dataloss"));
@@ -306,7 +306,7 @@ save(Extension *key, SPDocument *doc, gchar const *filename, bool setextension,
             // also save the extension for next use
             store_file_extension_in_prefs (omod->get_id(), save_method);
             // set the "dataloss" attribute if the chosen extension is lossy
-            repr->setAttribute("inkscape:dataloss", NULL);
+            repr->setAttribute("inkscape:dataloss", nullptr);
             if (omod->causes_dataloss()) {
                 repr->setAttribute("inkscape:dataloss", "true");
             }
@@ -446,17 +446,17 @@ build_from_reprdoc(Inkscape::XML::Document *doc, Implementation::Implementation
         MODULE_UNKNOWN_FUNC
     } module_functional_type = MODULE_UNKNOWN_FUNC;
 
-    g_return_val_if_fail(doc != NULL, NULL);
+    g_return_val_if_fail(doc != nullptr, NULL);
 
     Inkscape::XML::Node *repr = doc->root();
 
     if (strcmp(repr->name(), INKSCAPE_EXTENSION_NS "inkscape-extension")) {
         g_warning("Extension definition started with <%s> instead of <" INKSCAPE_EXTENSION_NS "inkscape-extension>.  Extension will not be created. See http://wiki.inkscape.org/wiki/index.php/Extensions for reference.\n", repr->name());
-        return NULL;
+        return nullptr;
     }
 
     Inkscape::XML::Node *child_repr = repr->firstChild();
-    while (child_repr != NULL) {
+    while (child_repr != nullptr) {
         char const *element_name = child_repr->name();
         /* printf("Child: %s\n", child_repr->name()); */
         if (!strcmp(element_name, INKSCAPE_EXTENSION_NS "input")) {
@@ -483,7 +483,7 @@ build_from_reprdoc(Inkscape::XML::Document *doc, Implementation::Implementation
     }
 
     Implementation::Implementation *imp;
-    if (in_imp == NULL) {
+    if (in_imp == nullptr) {
         switch (module_implementation_type) {
             case MODULE_EXTENSION: {
                 Implementation::Script *script = new Implementation::Script();
@@ -497,14 +497,14 @@ build_from_reprdoc(Inkscape::XML::Document *doc, Implementation::Implementation
             }
             case MODULE_PLUGIN: {
                 Inkscape::Extension::Loader loader = Inkscape::Extension::Loader();
-                if( baseDir != NULL){
+                if( baseDir != nullptr){
                     loader.set_base_directory ( *baseDir );
                 }
                 imp = loader.load_implementation(doc);
                 break;
             }
             default: {
-                imp = NULL;
+                imp = nullptr;
                 break;
             }
         }
@@ -512,7 +512,7 @@ build_from_reprdoc(Inkscape::XML::Document *doc, Implementation::Implementation
         imp = in_imp;
     }
 
-    Extension *module = NULL;
+    Extension *module = nullptr;
     switch (module_functional_type) {
         case MODULE_INPUT: {
             module = new Input(repr, imp);
@@ -556,8 +556,8 @@ build_from_file(gchar const *filename)
 {
     Inkscape::XML::Document *doc = sp_repr_read_file(filename, INKSCAPE_EXTENSION_URI);
     std::string dir = Glib::path_get_dirname(filename);
-    Extension *ext = build_from_reprdoc(doc, NULL, &dir);
-    if (ext != NULL)
+    Extension *ext = build_from_reprdoc(doc, nullptr, &dir);
+    if (ext != nullptr)
         Inkscape::GC::release(doc);
     else
         g_warning("Unable to create extension from definition file %s.\n", filename);
@@ -577,8 +577,8 @@ Extension *
 build_from_mem(gchar const *buffer, Implementation::Implementation *in_imp)
 {
     Inkscape::XML::Document *doc = sp_repr_read_mem(buffer, strlen(buffer), INKSCAPE_EXTENSION_URI);
-    g_return_val_if_fail(doc != NULL, NULL);
-    Extension *ext = build_from_reprdoc(doc, in_imp, NULL);
+    g_return_val_if_fail(doc != nullptr, NULL);
+    Extension *ext = build_from_reprdoc(doc, in_imp, nullptr);
     Inkscape::GC::release(doc);
     return ext;
 }
diff --git a/src/extension/timer.cpp b/src/extension/timer.cpp
index b32c04f30..5fb727409 100644
--- a/src/extension/timer.cpp
+++ b/src/extension/timer.cpp
@@ -20,8 +20,8 @@ namespace Extension {
 
 #define TIMER_SCALE_VALUE  20
 
-ExpirationTimer * ExpirationTimer::timer_list = NULL;
-ExpirationTimer * ExpirationTimer::idle_start = NULL;
+ExpirationTimer * ExpirationTimer::timer_list = nullptr;
+ExpirationTimer * ExpirationTimer::idle_start = nullptr;
 long ExpirationTimer::timeout = 240;
 bool ExpirationTimer::timer_started = false;
 
@@ -38,7 +38,7 @@ ExpirationTimer::ExpirationTimer (Extension * in_extension):
     extension(in_extension)
 {
     /* Fix Me! */
-    if (timer_list == NULL) {
+    if (timer_list == nullptr) {
         next = this;
         timer_list = this;
     } else {
@@ -86,8 +86,8 @@ ExpirationTimer::~ExpirationTimer(void)
     } else {
         /* If we're the only entry in the list, the list needs to go
            to NULL */
-        timer_list = NULL;
-        idle_start = NULL;
+        timer_list = nullptr;
+        idle_start = nullptr;
     }
 
     return;
@@ -151,7 +151,7 @@ ExpirationTimer::idle_func (void)
     // std::cout << "Idle func pass: " << idle_cnt++ << "  timer list: " << timer_list << std::endl;
 
     /* see if this is the last */
-    if (timer_list == NULL) {
+    if (timer_list == nullptr) {
         timer_started = false;
         return false;
     }
@@ -162,7 +162,7 @@ ExpirationTimer::idle_func (void)
     }
 
     /* see if this is the last */
-    if (timer_list == NULL) {
+    if (timer_list == nullptr) {
         timer_started = false;
         return false;
     }