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

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

34 files changed, 500 insertions, 500 deletions

diff --git a/src/widgets/button.cpp b/src/widgets/button.cpp
index 7dcfc9771..7ebc20b6f 100644
--- a/src/widgets/button.cpp
+++ b/src/widgets/button.cpp
@@ -47,8 +47,8 @@ static void sp_button_class_init(SPButtonClass *klass)
 
 static void sp_button_init(SPButton *button)
 {
-    button->action = NULL;
-    button->doubleclick_action = NULL;
+    button->action = nullptr;
+    button->doubleclick_action = nullptr;
     new (&button->c_set_active) sigc::connection();
     new (&button->c_set_sensitive) sigc::connection();
 
@@ -66,10 +66,10 @@ static void sp_button_dispose(GObject *object)
     SPButton *button = SP_BUTTON(object);
 
     if (button->action) {
-        sp_button_set_action(button, NULL);
+        sp_button_set_action(button, nullptr);
     }
     if (button->doubleclick_action) {
-        sp_button_set_doubleclick_action(button, NULL);
+        sp_button_set_doubleclick_action(button, nullptr);
     }
 
     button->c_set_active.~connection();
@@ -136,7 +136,7 @@ static gint sp_button_process_event(SPButton *button, GdkEvent *event)
     switch (event->type) {
     case GDK_2BUTTON_PRESS:
         if (button->doubleclick_action) {
-            sp_action_perform(button->doubleclick_action, NULL);
+            sp_action_perform(button->doubleclick_action, nullptr);
         }
         return TRUE;
         break;
@@ -150,13 +150,13 @@ static gint sp_button_process_event(SPButton *button, GdkEvent *event)
 static void sp_button_perform_action(SPButton *button, gpointer /*data*/)
 {
     if (button->action) {
-        sp_action_perform(button->action, NULL);
+        sp_action_perform(button->action, nullptr);
     }
 }
 
 GtkWidget *sp_button_new(GtkIconSize size, SPButtonType type, SPAction *action, SPAction *doubleclick_action)
 {
-    SPButton *button = SP_BUTTON(g_object_new(SP_TYPE_BUTTON, NULL));
+    SPButton *button = SP_BUTTON(g_object_new(SP_TYPE_BUTTON, nullptr));
 
     button->type = type;
     button->lsize = CLAMP(size, GTK_ICON_SIZE_MENU, GTK_ICON_SIZE_DIALOG);
@@ -251,15 +251,15 @@ static void sp_button_set_composed_tooltip(GtkWidget *widget, SPAction *action)
         }
     } else {
         // no action
-        gtk_widget_set_tooltip_text(widget, NULL);
+        gtk_widget_set_tooltip_text(widget, nullptr);
     }
 }
 
 GtkWidget *sp_button_new_from_data(GtkIconSize size, SPButtonType type, Inkscape::UI::View::View *view,
                                    const gchar *name, const gchar *tip)
 {
-    SPAction *action = sp_action_new(Inkscape::ActionContext(view), name, name, tip, name, 0);
-    GtkWidget *button = sp_button_new(size, type, action, NULL);
+    SPAction *action = sp_action_new(Inkscape::ActionContext(view), name, name, tip, name, nullptr);
+    GtkWidget *button = sp_button_new(size, type, action, nullptr);
     g_object_unref(action);
     return button;
 }
diff --git a/src/widgets/dash-selector.cpp b/src/widgets/dash-selector.cpp
index ed2dbe321..37bf08b3d 100644
--- a/src/widgets/dash-selector.cpp
+++ b/src/widgets/dash-selector.cpp
@@ -43,9 +43,9 @@ static double dash_1_2[] = {1.0, 2.0, -1.0};
 static double dash_1_4[] = {1.0, 4.0, -1.0};
 
 static size_t BD_LEN = 7;  // must correspond to the number of entries in the next line
-static double *builtin_dashes[] = {dash_0, dash_1_1, dash_2_1, dash_4_1, dash_1_2, dash_1_4, NULL};
+static double *builtin_dashes[] = {dash_0, dash_1_1, dash_2_1, dash_4_1, dash_1_2, dash_1_4, nullptr};
 
-static double **dashes = NULL;
+static double **dashes = nullptr;
 
 SPDashSelector::SPDashSelector()
     : preview_width(80),
@@ -143,7 +143,7 @@ void SPDashSelector::init_dashes() {
         for(i=0;i<15;i++){ d[i]=i; } // have to put something in there, this is a pattern hopefully nobody would choose
         d[15]=-1.0;
         // final terminator
-        dashes[++pos]   = NULL;
+        dashes[++pos]   = nullptr;
     }
 }
 
@@ -222,7 +222,7 @@ void SPDashSelector::get_dash(int *ndash, double **dash, double *off)
         if (ndash)
             *ndash = 0;
         if (dash)
-            *dash = NULL;
+            *dash = nullptr;
         if (off)
             *off = 0.0;
     }
diff --git a/src/widgets/desktop-widget.cpp b/src/widgets/desktop-widget.cpp
index 850253c00..3c15bf3a5 100644
--- a/src/widgets/desktop-widget.cpp
+++ b/src/widgets/desktop-widget.cpp
@@ -129,7 +129,7 @@ public:
     CMSPrefWatcher() :
         _dpw(*this),
         _spw(*this),
-        _tracker(ege_color_prof_tracker_new(0))
+        _tracker(ege_color_prof_tracker_new(nullptr))
     {
         Inkscape::Preferences *prefs = Inkscape::Preferences::get();
         g_signal_connect( G_OBJECT(_tracker), "modified", G_CALLBACK(hook), this );
@@ -188,7 +188,7 @@ private:
 #if defined(HAVE_LIBLCMS1) || defined(HAVE_LIBLCMS2)
 void CMSPrefWatcher::hook(EgeColorProfTracker * /*tracker*/, gint monitor, CMSPrefWatcher * /*watcher*/)
 {
-    unsigned char* buf = 0;
+    unsigned char* buf = nullptr;
     guint len = 0;
 
     ege_color_prof_tracker_get_profile_for( monitor, reinterpret_cast<gpointer*>(&buf), &len );
@@ -225,7 +225,7 @@ void CMSPrefWatcher::_setCmsSensitive(bool enabled)
 #endif // defined(HAVE_LIBLCMS1) || defined(HAVE_LIBLCMS2)
 }
 
-static CMSPrefWatcher* watcher = NULL;
+static CMSPrefWatcher* watcher = nullptr;
 
 void
 SPDesktopWidget::setMessage (Inkscape::MessageType type, const gchar *message)
@@ -261,7 +261,7 @@ SPDesktopWidget::window_get_pointer()
     return Geom::Point(x, y);
 }
 
-static GTimer *overallTimer = 0;
+static GTimer *overallTimer = nullptr;
 
 /**
  * Registers SPDesktopWidget class and returns its type number.
@@ -272,15 +272,15 @@ GType SPDesktopWidget::getType(void)
     if (!type) {
         GTypeInfo info = {
             sizeof(SPDesktopWidgetClass),
-            0, // base_init
-            0, // base_finalize
+            nullptr, // base_init
+            nullptr, // base_finalize
             (GClassInitFunc)sp_desktop_widget_class_init,
-            0, // class_finalize
-            0, // class_data
+            nullptr, // class_finalize
+            nullptr, // class_data
             sizeof(SPDesktopWidget),
             0, // n_preallocs
             (GInstanceInitFunc)SPDesktopWidget::init,
-            0 // value_table
+            nullptr // value_table
         };
         type = g_type_register_static(SP_TYPE_VIEW_WIDGET, "SPDesktopWidget", &info, static_cast<GTypeFlags>(0));
         // Begin a timer to watch for the first desktop to appear on-screen
@@ -330,8 +330,8 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
 
     new (&dtw->modified_connection) sigc::connection();
 
-    dtw->window = 0;
-    dtw->desktop = NULL;
+    dtw->window = nullptr;
+    dtw->desktop = nullptr;
     dtw->_interaction_disabled_counter = 0;
 
     /* Main table */
@@ -386,7 +386,7 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
     // Lock guides button
     dtw->guides_lock = sp_button_new_from_data( GTK_ICON_SIZE_MENU,
                                                SP_BUTTON_TYPE_TOGGLE,
-                                               NULL,
+                                               nullptr,
                                                INKSCAPE_ICON("object-locked"),
                                                _("Toggle lock of all guides in the document"));
     auto guides_lock_style_provider = Gtk::CssProvider::create();
@@ -446,7 +446,7 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
     // Sticky zoom button
     dtw->sticky_zoom = sp_button_new_from_data ( GTK_ICON_SIZE_MENU,
                                                  SP_BUTTON_TYPE_TOGGLE,
-                                                 NULL,
+                                                 nullptr,
                                                  INKSCAPE_ICON("zoom-original"),
                                                  _("Zoom drawing if window size changes"));
     gtk_widget_set_name(dtw->sticky_zoom, "StickyZoom");
@@ -470,7 +470,7 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
     }
     dtw->cms_adjust = sp_button_new_from_data( GTK_ICON_SIZE_MENU,
                                                SP_BUTTON_TYPE_TOGGLE,
-                                               NULL,
+                                               nullptr,
                                                INKSCAPE_ICON("color-management"),
                                                tip );
     gtk_widget_set_name(dtw->cms_adjust, "CMS_Adjust");
@@ -516,7 +516,7 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
                                     "SPCanvas {\n"
                                     " background-color: white;\n"
                                     "}\n",
-                                    -1, NULL);
+                                    -1, nullptr);
 
     gtk_style_context_add_provider(style_context,
                                    GTK_STYLE_PROVIDER(css_provider),
@@ -542,8 +542,8 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
 
         /* Prevent the paned from catching F6 and F8 by unsetting the default callbacks */
         if (GtkPanedClass *paned_class = GTK_PANED_CLASS (G_OBJECT_GET_CLASS (paned->gobj()))) {
-            paned_class->cycle_child_focus = NULL;
-            paned_class->cycle_handle_focus = NULL;
+            paned_class->cycle_child_focus = nullptr;
+            paned_class->cycle_handle_focus = nullptr;
         }
 
         paned->set_hexpand(true);
@@ -573,13 +573,13 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
 		    FALSE, FALSE, 0);
 
     // Layer Selector
-    dtw->layer_selector = new Inkscape::Widgets::LayerSelector(NULL);
+    dtw->layer_selector = new Inkscape::Widgets::LayerSelector(nullptr);
     // FIXME: need to unreference on container destruction to avoid leak
     dtw->layer_selector->reference();
     gtk_box_pack_start(GTK_BOX(dtw->statusbar), GTK_WIDGET(dtw->layer_selector->gobj()), FALSE, FALSE, 1);
 
     // Select Status
-    dtw->select_status = gtk_label_new (NULL);
+    dtw->select_status = gtk_label_new (nullptr);
     gtk_widget_set_name( dtw->select_status, "SelectStatus");
     gtk_label_set_ellipsize (GTK_LABEL(dtw->select_status), PANGO_ELLIPSIZE_END);
 #if GTK_CHECK_VERSION(3,10,0)
@@ -666,8 +666,8 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
     gtk_widget_set_halign(label_y, GTK_ALIGN_START);
     gtk_grid_attach(GTK_GRID(dtw->coord_status), label_x, 1, 0, 1, 1);
     gtk_grid_attach(GTK_GRID(dtw->coord_status), label_y, 1, 1, 1, 1);
-    dtw->coord_status_x = gtk_label_new(NULL);
-    dtw->coord_status_y = gtk_label_new(NULL);
+    dtw->coord_status_x = gtk_label_new(nullptr);
+    dtw->coord_status_y = gtk_label_new(nullptr);
     gtk_label_set_markup( GTK_LABEL(dtw->coord_status_x), "<tt>   0.00 </tt>" );
     gtk_label_set_markup( GTK_LABEL(dtw->coord_status_y), "<tt>   0.00 </tt>" );
 
@@ -717,7 +717,7 @@ void SPDesktopWidget::init( SPDesktopWidget *dtw )
         } else {
             g_timer_destroy(overallTimer);
         }
-        overallTimer = 0;
+        overallTimer = nullptr;
     }
 
     // Ensure that ruler ranges are updated correctly whenever the canvas table
@@ -735,7 +735,7 @@ static void sp_desktop_widget_dispose(GObject *object)
 {
     SPDesktopWidget *dtw = SP_DESKTOP_WIDGET (object);
 
-    if (dtw == NULL) {
+    if (dtw == nullptr) {
         return;
     }
 
@@ -749,14 +749,14 @@ static void sp_desktop_widget_dispose(GObject *object)
         // Zoom
         g_signal_handlers_disconnect_by_func(G_OBJECT (dtw->zoom_status), (gpointer) G_CALLBACK(sp_dtw_zoom_input), dtw);
         g_signal_handlers_disconnect_by_func(G_OBJECT (dtw->zoom_status), (gpointer) G_CALLBACK(sp_dtw_zoom_output), dtw);
-        g_signal_handlers_disconnect_matched (G_OBJECT (dtw->zoom_status), G_SIGNAL_MATCH_DATA, 0, 0, NULL, NULL, dtw->zoom_status);
+        g_signal_handlers_disconnect_matched (G_OBJECT (dtw->zoom_status), G_SIGNAL_MATCH_DATA, 0, 0, nullptr, nullptr, dtw->zoom_status);
         g_signal_handlers_disconnect_by_func (G_OBJECT (dtw->zoom_status), (gpointer) G_CALLBACK (sp_dtw_zoom_value_changed), dtw);
         g_signal_handlers_disconnect_by_func (G_OBJECT (dtw->zoom_status), (gpointer) G_CALLBACK (sp_dtw_zoom_populate_popup), dtw);
 
         // Rotation
         g_signal_handlers_disconnect_by_func(G_OBJECT (dtw->rotation_status), (gpointer) G_CALLBACK(sp_dtw_rotation_input), dtw);
         g_signal_handlers_disconnect_by_func(G_OBJECT (dtw->rotation_status), (gpointer) G_CALLBACK(sp_dtw_rotation_output), dtw);
-        g_signal_handlers_disconnect_matched (G_OBJECT (dtw->rotation_status), G_SIGNAL_MATCH_DATA, 0, 0, NULL, NULL, dtw->rotation_status);
+        g_signal_handlers_disconnect_matched (G_OBJECT (dtw->rotation_status), G_SIGNAL_MATCH_DATA, 0, 0, nullptr, nullptr, dtw->rotation_status);
         g_signal_handlers_disconnect_by_func (G_OBJECT (dtw->rotation_status), (gpointer) G_CALLBACK (sp_dtw_rotation_value_changed), dtw);
         g_signal_handlers_disconnect_by_func (G_OBJECT (dtw->rotation_status), (gpointer) G_CALLBACK (sp_dtw_rotation_populate_popup), dtw);
 
@@ -764,13 +764,13 @@ static void sp_desktop_widget_dispose(GObject *object)
         g_signal_handlers_disconnect_by_func (G_OBJECT (dtw->canvas), (gpointer) G_CALLBACK (sp_desktop_widget_event), dtw);
         g_signal_handlers_disconnect_by_func (G_OBJECT (dtw->canvas_tbl), (gpointer) G_CALLBACK (canvas_tbl_size_allocate), dtw);
 
-        dtw->layer_selector->setDesktop(NULL);
+        dtw->layer_selector->setDesktop(nullptr);
         dtw->layer_selector->unreference();
         INKSCAPE.remove_desktop(dtw->desktop); // clears selection and event_context
         dtw->modified_connection.disconnect();
         dtw->desktop->destroy();
         Inkscape::GC::release (dtw->desktop);
-        dtw->desktop = NULL;
+        dtw->desktop = nullptr;
     }
 
     dtw->modified_connection.~connection();
@@ -962,7 +962,7 @@ sp_desktop_widget_event (GtkWidget *widget, GdkEvent *event, SPDesktopWidget *dt
         // and passed on by the canvas acetate (I think). --bb
         if ((event->type == GDK_KEY_PRESS || event->type == GDK_KEY_RELEASE)
                 && !dtw->canvas->_current_item) {
-            return sp_desktop_root_handler (NULL, event, dtw->desktop);
+            return sp_desktop_root_handler (nullptr, event, dtw->desktop);
         }
     }
 
@@ -1083,7 +1083,7 @@ sp_dtw_desktop_deactivate (SPDesktopWidget */*dtw*/)
 bool
 SPDesktopWidget::shutdown()
 {
-    g_assert(desktop != NULL);
+    g_assert(desktop != nullptr);
 
     if (INKSCAPE.sole_desktop_for_document(*desktop)) {
         SPDocument *doc = desktop->doc();
@@ -1136,7 +1136,7 @@ SPDesktopWidget::shutdown()
         }
         /* Code to check data loss */
         bool allow_data_loss = FALSE;
-        while (doc->getReprRoot()->attribute("inkscape:dataloss") != NULL && allow_data_loss == FALSE) {
+        while (doc->getReprRoot()->attribute("inkscape:dataloss") != nullptr && allow_data_loss == FALSE) {
             Gtk::Window *toplevel_window = Glib::wrap(GTK_WINDOW(gtk_widget_get_toplevel(GTK_WIDGET(this))));
             Glib::ustring message = g_markup_printf_escaped(
                 _("<span weight=\"bold\" size=\"larger\">The file \"%s\" was saved with a format that may cause data loss!</span>\n\n"
@@ -1222,8 +1222,8 @@ SPDesktopWidget::shutdown()
 void
 SPDesktopWidget::requestCanvasUpdate() {
     // ^^ also this->desktop != 0
-    g_return_if_fail(this->desktop != NULL);
-    g_return_if_fail(this->desktop->main != NULL);
+    g_return_if_fail(this->desktop != nullptr);
+    g_return_if_fail(this->desktop->main != nullptr);
     gtk_widget_queue_draw (GTK_WIDGET (SP_CANVAS_ITEM (this->desktop->main)->canvas));
 }
 
@@ -1541,7 +1541,7 @@ SPDesktopWidget::setToolboxFocusTo (const gchar* label)
 void
 SPDesktopWidget::setToolboxAdjustmentValue (gchar const *id, double value)
 {
-    GtkAdjustment *a = NULL;
+    GtkAdjustment *a = nullptr;
     gpointer hb = sp_search_by_data_recursive (aux_toolbox, (gpointer) id);
     if (hb && GTK_IS_WIDGET(hb)) {
         if (GTK_IS_SPIN_BUTTON(hb))
@@ -1589,7 +1589,7 @@ SPDesktopWidget::isToolboxButtonActive (const gchar* id)
 void SPDesktopWidget::setToolboxPosition(Glib::ustring const& id, GtkPositionType pos)
 {
     // Note - later on these won't be individual member variables.
-    GtkWidget* toolbox = 0;
+    GtkWidget* toolbox = nullptr;
     if (id == "ToolToolbar") {
         toolbox = tool_toolbox;
     } else if (id == "AuxToolbar") {
@@ -1643,7 +1643,7 @@ SPViewWidget *sp_desktop_widget_new( SPNamedView *namedview )
 
 SPDesktopWidget* SPDesktopWidget::createInstance(SPNamedView *namedview)
 {
-    SPDesktopWidget *dtw = static_cast<SPDesktopWidget*>(g_object_new(SP_TYPE_DESKTOP_WIDGET, NULL));
+    SPDesktopWidget *dtw = static_cast<SPDesktopWidget*>(g_object_new(SP_TYPE_DESKTOP_WIDGET, nullptr));
 
     dtw->dt2r = 1. / namedview->display_units->factor;
 
@@ -1752,11 +1752,11 @@ void SPDesktopWidget::namedviewModified(SPObject *obj, guint flags)
                             continue;
 
                         gpointer t = sp_search_by_data_recursive(GTK_WIDGET(j->gobj()), (gpointer) "tracker");
-                        if (t == NULL) // didn't find any tracker data
+                        if (t == nullptr) // didn't find any tracker data
                             continue;
 
                         UnitTracker *tracker = reinterpret_cast<UnitTracker*>( t );
-                        if (tracker == NULL) // it's null when inkscape is first opened
+                        if (tracker == nullptr) // it's null when inkscape is first opened
                             continue;
 
                         tracker->setActiveUnit( nv->display_units );
@@ -1769,7 +1769,7 @@ void SPDesktopWidget::namedviewModified(SPObject *obj, guint flags)
         gtk_widget_set_tooltip_text(this->vruler_box, gettext(nv->display_units->name_plural.c_str()));
 
         sp_desktop_widget_update_rulers(this);
-        ToolboxFactory::updateSnapToolbox(this->desktop, 0, this->snap_toolbox);
+        ToolboxFactory::updateSnapToolbox(this->desktop, nullptr, this->snap_toolbox);
     }
 }
 
@@ -1828,7 +1828,7 @@ sp_dtw_zoom_input (GtkSpinButton *spin, gdouble *new_val, gpointer /*data*/)
         *comma = '.';
     }
 
-    char *oldlocale = g_strdup (setlocale(LC_NUMERIC, NULL));
+    char *oldlocale = g_strdup (setlocale(LC_NUMERIC, nullptr));
     setlocale (LC_NUMERIC, "C");
     gdouble new_typed = atof (b);
     setlocale (LC_NUMERIC, oldlocale);
@@ -2029,7 +2029,7 @@ sp_dtw_rotation_input (GtkSpinButton *spin, gdouble *new_val, gpointer /*data*/)
         *comma = '.';
     }
 
-    char *oldlocale = g_strdup (setlocale(LC_NUMERIC, NULL));
+    char *oldlocale = g_strdup (setlocale(LC_NUMERIC, nullptr));
     setlocale (LC_NUMERIC, "C");
     gdouble new_value = atof (b);
     setlocale (LC_NUMERIC, oldlocale);
diff --git a/src/widgets/desktop-widget.h b/src/widgets/desktop-widget.h
index 92d670019..4744752dc 100644
--- a/src/widgets/desktop-widget.h
+++ b/src/widgets/desktop-widget.h
@@ -158,9 +158,9 @@ struct SPDesktopWidget {
             { return _dtw->shutdown(); }
         void destroy() override
             {
-                if(_dtw->window != NULL)
+                if(_dtw->window != nullptr)
                     delete _dtw->window;
-                _dtw->window = NULL;
+                _dtw->window = nullptr;
             }
 
         void requestCanvasUpdate() override
diff --git a/src/widgets/eek-preview.cpp b/src/widgets/eek-preview.cpp
index 38d5173fa..f12cecc7f 100644
--- a/src/widgets/eek-preview.cpp
+++ b/src/widgets/eek-preview.cpp
@@ -87,7 +87,7 @@ static gboolean eek_preview_draw(GtkWidget* widget, cairo_t* cr);
 
 G_DEFINE_TYPE(EekPreview, eek_preview, GTK_TYPE_DRAWING_AREA);
 
-static GtkWidgetClass* parent_class = 0;
+static GtkWidgetClass* parent_class = nullptr;
 
 void eek_preview_set_color( EekPreview* preview, int r, int g, int b )
 {
@@ -114,7 +114,7 @@ eek_preview_set_pixbuf(EekPreview *preview,
     if (priv->scaled)
     {
         g_object_unref(priv->scaled);
-        priv->scaled = NULL;
+        priv->scaled = nullptr;
     }
 
     priv->scaledW = gdk_pixbuf_get_width(priv->previewPixbuf);
@@ -567,7 +567,7 @@ static void eek_preview_class_init( EekPreviewClass *klass )
                       G_TYPE_FROM_CLASS( klass ),
                       (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_ACTION),
                       G_STRUCT_OFFSET( EekPreviewClass, clicked ),
-                      NULL, NULL,
+                      nullptr, nullptr,
                       g_cclosure_marshal_VOID__VOID, G_TYPE_NONE, 0 );
 
     eek_preview_signals[ALTCLICKED_SIGNAL] =
@@ -575,7 +575,7 @@ static void eek_preview_class_init( EekPreviewClass *klass )
                       G_TYPE_FROM_CLASS( klass ),
                       (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_ACTION),
                       G_STRUCT_OFFSET( EekPreviewClass, clicked ),
-                      NULL, NULL,
+                      nullptr, nullptr,
                       g_cclosure_marshal_VOID__INT, G_TYPE_NONE,
                       1, G_TYPE_INT );
 
@@ -584,7 +584,7 @@ static void eek_preview_class_init( EekPreviewClass *klass )
                                      PROP_FOCUS,
                                      g_param_spec_boolean(
                                          "focus-on-click",
-                                         NULL,
+                                         nullptr,
                                          "flag to grab focus when clicked",
                                          TRUE,
                                          (GParamFlags)(G_PARAM_READWRITE | G_PARAM_CONSTRUCT)
@@ -704,14 +704,14 @@ eek_preview_init(EekPreview *preview)
     priv->size          = PREVIEW_SIZE_SMALL;
     priv->ratio         = 100;
     priv->border        = BORDER_NONE;
-    priv->previewPixbuf = 0;
-    priv->scaled        = 0;
+    priv->previewPixbuf = nullptr;
+    priv->scaled        = nullptr;
 }
 
 
 GtkWidget* eek_preview_new(void)
 {
-    return GTK_WIDGET( g_object_new( EEK_PREVIEW_TYPE, NULL ) );
+    return GTK_WIDGET( g_object_new( EEK_PREVIEW_TYPE, nullptr ) );
 }
 
 /*
diff --git a/src/widgets/ege-adjustment-action.cpp b/src/widgets/ege-adjustment-action.cpp
index e922bcc00..ba120c310 100644
--- a/src/widgets/ege-adjustment-action.cpp
+++ b/src/widgets/ege-adjustment-action.cpp
@@ -72,7 +72,7 @@ static void ege_adjustment_action_defocus( EgeAdjustmentAction* action );
 static void egeAct_free_description( gpointer data, gpointer user_data );
 static void egeAct_free_all_descriptions( EgeAdjustmentAction* action );
 
-static EgeCreateAdjWidgetCB gFactoryCb = 0;
+static EgeCreateAdjWidgetCB gFactoryCb = nullptr;
 static GQuark gDataName = 0;
 
 enum {
@@ -90,7 +90,7 @@ static const gchar *floogles[] = {
     INKSCAPE_ICON("go-down"),
     INKSCAPE_ICON("help-about"),
     INKSCAPE_ICON("go-up"),
-    0};
+    nullptr};
 
 typedef struct _EgeAdjustmentDescr EgeAdjustmentDescr;
 
@@ -204,7 +204,7 @@ static void ege_adjustment_action_class_init( EgeAdjustmentActionClass* klass )
                                          g_param_spec_string( "self-id",
                                                               "Self ID",
                                                               "Marker for self pointer",
-                                                              0,
+                                                              nullptr,
                                                               (GParamFlags)(G_PARAM_READABLE | G_PARAM_WRITABLE | G_PARAM_CONSTRUCT) ) );
 
         g_object_class_install_property( objClass,
@@ -259,30 +259,30 @@ void ege_adjustment_action_set_compact_tool_factory( EgeCreateAdjWidgetCB factor
 static void ege_adjustment_action_init( EgeAdjustmentAction* action )
 {
     action->private_data = EGE_ADJUSTMENT_ACTION_GET_PRIVATE( action );
-    action->private_data->adj = 0;
-    action->private_data->focusWidget = 0;
+    action->private_data->adj = nullptr;
+    action->private_data->focusWidget = nullptr;
     action->private_data->climbRate = 0.0;
     action->private_data->digits = 2;
     action->private_data->epsilon = 0.009;
     action->private_data->format = g_strdup_printf("%%0.%df%%s%%s", action->private_data->digits);
-    action->private_data->selfId = 0;
-    action->private_data->toolPost = 0;
+    action->private_data->selfId = nullptr;
+    action->private_data->toolPost = nullptr;
     action->private_data->lastVal = 0.0;
     action->private_data->step = 0.0;
     action->private_data->page = 0.0;
     action->private_data->appearanceMode = APPEARANCE_NONE;
     action->private_data->transferFocus = FALSE;
     //action->private_data->descriptions = 0;
-    action->private_data->appearance = 0;
-    action->private_data->iconId = 0;
+    action->private_data->appearance = nullptr;
+    action->private_data->iconId = nullptr;
     action->private_data->iconSize = GTK_ICON_SIZE_SMALL_TOOLBAR;
-    action->private_data->unitTracker = NULL;
+    action->private_data->unitTracker = nullptr;
 }
 
 static void ege_adjustment_action_finalize( GObject* object )
 {
-    EgeAdjustmentAction* action = 0;
-    g_return_if_fail( object != NULL );
+    EgeAdjustmentAction* action = nullptr;
+    g_return_if_fail( object != nullptr );
     g_return_if_fail( IS_EGE_ADJUSTMENT_ACTION(object) );
 
     action = EGE_ADJUSTMENT_ACTION( object );
@@ -510,7 +510,7 @@ static void egeAct_free_description( gpointer data, gpointer user_data ) {
         EgeAdjustmentDescr* descr = (EgeAdjustmentDescr*)data;
         if ( descr->descr ) {
             g_free( descr->descr );
-            descr->descr = 0;
+            descr->descr = nullptr;
         }
         g_free( descr );
     }
@@ -519,7 +519,7 @@ static void egeAct_free_description( gpointer data, gpointer user_data ) {
 static void egeAct_free_all_descriptions( EgeAdjustmentAction* action )
 {
     for(auto i:action->private_data->descriptions) {
-        egeAct_free_description(i,0);
+        egeAct_free_description(i,nullptr);
     }
     for(auto i:action->private_data->descriptions) {
         g_free(i);
@@ -555,7 +555,7 @@ void ege_adjustment_action_set_descriptions( EgeAdjustmentAction* action, gchar
         guint i = 0;
         for ( i = 0; i < count; i++ ) {
             EgeAdjustmentDescr* descr = g_new0( EgeAdjustmentDescr, 1 );
-            descr->descr = descriptions[i] ? g_strdup( descriptions[i] ) : 0;
+            descr->descr = descriptions[i] ? g_strdup( descriptions[i] ) : nullptr;
             descr->value = values[i];
             action->private_data->descriptions.push_back(descr);
             std::sort(action->private_data->descriptions.begin(),action->private_data->descriptions.end());
@@ -629,8 +629,8 @@ static void process_menu_action( GtkWidget* obj, gpointer data )
 
 static void create_single_menu_item( GCallback toggleCb, int val, GtkWidget* menu, EgeAdjustmentAction* act, GtkWidget** dst, Gtk::RadioMenuItem::Group *group, gdouble num, gboolean active )
 {
-    char* str = 0;
-    EgeAdjustmentDescr* marker = 0;
+    char* str = nullptr;
+    EgeAdjustmentDescr* marker = nullptr;
     std::vector<EgeAdjustmentDescr*> cur = act->private_data->descriptions;
 
     for (auto descr:cur) {
@@ -682,7 +682,7 @@ static int flush_explicit_items( std::vector<EgeAdjustmentDescr*> descriptions,
             create_single_menu_item( toggleCb, val + ( std::find(act->private_data->descriptions.begin(),act->private_data->descriptions.end(),descr) - act->private_data->descriptions.begin() ) , menu, act, dst, group, descr->value, FALSE );
         }
         pos--;
-        descr = (pos<0) ? descriptions[pos] : NULL;
+        descr = (pos<0) ? descriptions[pos] : nullptr;
     }
 
     return pos;
@@ -693,7 +693,7 @@ static GtkWidget* create_popup_number_menu( EgeAdjustmentAction* act )
     GtkWidget* menu = gtk_menu_new();
 
     Gtk::RadioMenuItem::Group group;
-    GtkWidget* single = 0;
+    GtkWidget* single = nullptr;
     std::vector<EgeAdjustmentDescr*> list = act->private_data->descriptions;
     int addOns = list.size() - 1;
 
@@ -749,12 +749,12 @@ static GtkWidget* create_popup_number_menu( EgeAdjustmentAction* act )
 
 static GtkWidget* create_menu_item( GtkAction* action )
 {
-    GtkWidget* item = 0;
+    GtkWidget* item = nullptr;
 
     if ( IS_EGE_ADJUSTMENT_ACTION(action) ) {
         EgeAdjustmentAction* act = EGE_ADJUSTMENT_ACTION( action );
         GValue value;
-        GtkWidget*  subby = 0;
+        GtkWidget*  subby = nullptr;
 
         memset( &value, 0, sizeof(value) );
         g_value_init( &value, G_TYPE_STRING );
@@ -811,11 +811,11 @@ static gboolean event_cb( EgeAdjustmentAction* act, GdkEvent* evt )
 
 static GtkWidget* create_tool_item( GtkAction* action )
 {
-    GtkWidget* item = 0;
+    GtkWidget* item = nullptr;
 
     if ( IS_EGE_ADJUSTMENT_ACTION(action) ) {
         EgeAdjustmentAction* act = EGE_ADJUSTMENT_ACTION( action );
-        GtkWidget* spinbutton = 0;
+        GtkWidget* spinbutton = nullptr;
 	auto hb = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);
 	gtk_box_set_homogeneous(GTK_BOX(hb), FALSE);
         GValue value;
@@ -833,7 +833,7 @@ static GtkWidget* create_tool_item( GtkAction* action )
             gtk_widget_set_size_request(spinbutton, 100, -1);
 
         } else if ( act->private_data->appearanceMode == APPEARANCE_MINIMAL ) {
-            spinbutton = gtk_scale_button_new( GTK_ICON_SIZE_MENU, 0, 100, 2, 0 );
+            spinbutton = gtk_scale_button_new( GTK_ICON_SIZE_MENU, 0, 100, 2, nullptr );
             gtk_scale_button_set_adjustment( GTK_SCALE_BUTTON(spinbutton), act->private_data->adj );
             gtk_scale_button_set_icons( GTK_SCALE_BUTTON(spinbutton), floogles );
         } else {
@@ -969,8 +969,8 @@ static gboolean process_tab( GtkWidget* widget, int direction )
 {
     gboolean handled = FALSE;
     GtkWidget* parent = gtk_widget_get_parent(widget);
-    GtkWidget* gp = parent ? gtk_widget_get_parent(parent) : 0;
-    GtkWidget* ggp = gp ? gtk_widget_get_parent(gp) : 0;
+    GtkWidget* gp = parent ? gtk_widget_get_parent(parent) : nullptr;
+    GtkWidget* ggp = gp ? gtk_widget_get_parent(gp) : nullptr;
 
     if ( ggp && GTK_IS_TOOLBAR(ggp) ) {
         std::vector<Gtk::Widget*> kids = Glib::wrap(GTK_CONTAINER(ggp))->get_children();
@@ -1017,7 +1017,7 @@ gboolean keypress_cb( GtkWidget *widget, GdkEventKey *event, gpointer data )
     guint key = 0;
     gdk_keymap_translate_keyboard_state( Gdk::Display::get_default()->get_keymap(),
                                          event->hardware_keycode, (GdkModifierType)event->state,
-                                         0, &key, 0, 0, 0 );
+                                         0, &key, nullptr, nullptr, nullptr );
 
     switch ( key ) {
         case GDK_KEY_Escape:
diff --git a/src/widgets/ege-output-action.cpp b/src/widgets/ege-output-action.cpp
index e7d74a25f..847a4f0a1 100644
--- a/src/widgets/ege-output-action.cpp
+++ b/src/widgets/ege-output-action.cpp
@@ -163,14 +163,14 @@ void ege_output_action_set_property( GObject* obj, guint propId, const GValue *v
 
 GtkWidget* create_tool_item( GtkAction* action )
 {
-    GtkWidget* item = 0;
+    GtkWidget* item = nullptr;
 
     if ( IS_EGE_OUTPUT_ACTION(action) )
     {
         GValue value;
         auto hb = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);
 	gtk_box_set_homogeneous(GTK_BOX(hb), FALSE);
-        GtkWidget* lbl = 0;
+        GtkWidget* lbl = nullptr;
         memset( &value, 0, sizeof(value) );
 
         g_value_init( &value, G_TYPE_STRING );
@@ -183,7 +183,7 @@ GtkWidget* create_tool_item( GtkAction* action )
         gtk_container_add( GTK_CONTAINER(hb), lbl );
 
         if ( EGE_OUTPUT_ACTION(action)->private_data->useMarkup ) {
-            lbl = gtk_label_new(NULL);
+            lbl = gtk_label_new(nullptr);
             gtk_label_set_markup( GTK_LABEL(lbl), sss ? sss : " " );
         } else {
             lbl = gtk_label_new( sss ? sss : " " );
@@ -211,7 +211,7 @@ void fixup_labels( GObject *gobject, GParamSpec *arg1, gpointer user_data )
 
     if ( arg1 && arg1->name && (strcmp("label", arg1->name) == 0) ) {
         GSList* proxies = gtk_action_get_proxies( GTK_ACTION(gobject) );
-        gchar* str = 0;
+        gchar* str = nullptr;
         g_object_get( gobject, "label", &str, NULL );
         Glib::ustring str2(str);
         (void)user_data;
diff --git a/src/widgets/ege-paint-def.cpp b/src/widgets/ege-paint-def.cpp
index 8e0ec9352..b9b184638 100644
--- a/src/widgets/ege-paint-def.cpp
+++ b/src/widgets/ege-paint-def.cpp
@@ -198,7 +198,7 @@ void PaintDef::getMIMEData(std::string const & type, char*& dest, int& len, int&
         format = 8;
     } else {
         // nothing
-        dest = 0;
+        dest = nullptr;
         len = 0;
     }
 }
diff --git a/src/widgets/fill-style.cpp b/src/widgets/fill-style.cpp
index e1c1ad6d0..2e35659dd 100644
--- a/src/widgets/fill-style.cpp
+++ b/src/widgets/fill-style.cpp
@@ -127,8 +127,8 @@ Gtk::Widget *Inkscape::Widgets::createStyleWidget( FillOrStroke kind )
 FillNStroke::FillNStroke( FillOrStroke k ) :
     Gtk::VBox(),
     kind(k),
-    desktop(0),
-    psel(0),
+    desktop(nullptr),
+    psel(nullptr),
     lastDrag(0),
     dragId(0),
     update(false),
@@ -167,7 +167,7 @@ FillNStroke::~FillNStroke()
         g_source_remove(dragId);
         dragId = 0;
     }
-    psel = 0;
+    psel = nullptr;
     selectModifiedConn.disconnect();
     subselChangedConn.disconnect();
     selectChangedConn.disconnect();
@@ -206,7 +206,7 @@ void FillNStroke::setDesktop(SPDesktop *desktop)
         if (desktop && desktop->selection) {
             selectChangedConn = desktop->selection->connectChanged(sigc::hide(sigc::mem_fun(*this, &FillNStroke::performUpdate)));
             subselChangedConn = desktop->connectToolSubselectionChanged(sigc::hide(sigc::mem_fun(*this, &FillNStroke::performUpdate)));
-            eventContextConn = desktop->connectEventContextChanged(sigc::hide(sigc::bind(sigc::mem_fun(*this, &FillNStroke::eventContextCB), (Inkscape::UI::Tools::ToolBase *)NULL)));
+            eventContextConn = desktop->connectEventContextChanged(sigc::hide(sigc::bind(sigc::mem_fun(*this, &FillNStroke::eventContextCB), (Inkscape::UI::Tools::ToolBase *)nullptr)));
 
             // Must check flags, so can't call performUpdate() directly.
             selectModifiedConn = desktop->selection->connectModified(sigc::hide<0>(sigc::mem_fun(*this, &FillNStroke::selectionModifiedCB)));
@@ -358,7 +358,7 @@ void FillNStroke::setFillrule( SPPaintSelector::FillRule mode )
         sp_desktop_set_style(desktop, css);
 
         sp_repr_css_attr_unref(css);
-        css = 0;
+        css = nullptr;
 
         DocumentUndo::done(desktop->doc(), SP_VERB_DIALOG_FILL_STROKE,
                            _("Change fill rule"));
@@ -425,7 +425,7 @@ void FillNStroke::dragFromPaint()
     // Assume a base 15.625ms resolution on the timer.
     if (!dragId && lastDrag && when && ((when - lastDrag) < 32)) {
         // local change, do not update from selection
-        dragId = g_timeout_add_full(G_PRIORITY_DEFAULT, 33, dragDelayCB, this, 0);
+        dragId = g_timeout_add_full(G_PRIORITY_DEFAULT, 33, dragDelayCB, this, nullptr);
     }
 
     if (dragId) {
@@ -442,7 +442,7 @@ void FillNStroke::dragFromPaint()
         case SPPaintSelector::MODE_SOLID_COLOR:
         {
             // local change, do not update from selection
-            dragId = g_timeout_add_full(G_PRIORITY_DEFAULT, 100, dragDelayCB, this, 0);
+            dragId = g_timeout_add_full(G_PRIORITY_DEFAULT, 100, dragDelayCB, this, nullptr);
             psel->setFlatColor( desktop, (kind == FILL) ? "fill" : "stroke", (kind == FILL) ? "fill-opacity" : "stroke-opacity" );
             DocumentUndo::maybeDone(desktop->doc(), (kind == FILL) ? undo_F_label : undo_S_label, SP_VERB_DIALOG_FILL_STROKE,
                                     (kind == FILL) ? _("Set fill color") : _("Set stroke color"));
@@ -505,7 +505,7 @@ void FillNStroke::updateFromPaint()
             sp_desktop_set_style(desktop, css);
 
             sp_repr_css_attr_unref(css);
-            css = 0;
+            css = nullptr;
 
             DocumentUndo::done(document, SP_VERB_DIALOG_FILL_STROKE,
                                (kind == FILL) ? _("Remove fill") : _("Remove stroke"));
@@ -551,7 +551,7 @@ void FillNStroke::updateFromPaint()
                                                        : SP_GRADIENT_TYPE_RADIAL );
                 bool createSwatch = (psel->mode == SPPaintSelector::MODE_SWATCH);
 
-                SPCSSAttr *css = 0;
+                SPCSSAttr *css = nullptr;
                 if (kind == FILL) {
                     // HACK: reset fill-opacity - that 0.75 is annoying; BUT remove this when we have an opacity slider for all tabs
                     css = sp_repr_css_attr_new();
@@ -617,7 +617,7 @@ void FillNStroke::updateFromPaint()
 
                 if (css) {
                     sp_repr_css_attr_unref(css);
-                    css = 0;
+                    css = nullptr;
                 }
 
                 DocumentUndo::done(document, SP_VERB_DIALOG_FILL_STROKE,
@@ -631,7 +631,7 @@ void FillNStroke::updateFromPaint()
             if (!items.empty()) {
                 SPGradientType const gradient_type = SP_GRADIENT_TYPE_MESH;
 
-                SPCSSAttr *css = 0;
+                SPCSSAttr *css = nullptr;
                 if (kind == FILL) {
                     // HACK: reset fill-opacity - that 0.75 is annoying; BUT remove this when we have an opacity slider for all tabs
                     css = sp_repr_css_attr_new();
@@ -717,7 +717,7 @@ void FillNStroke::updateFromPaint()
 
                 if (css) {
                     sp_repr_css_attr_unref(css);
-                    css = 0;
+                    css = nullptr;
                 }
 
                 DocumentUndo::done(document, SP_VERB_DIALOG_FILL_STROKE,
@@ -776,7 +776,7 @@ void FillNStroke::updateFromPaint()
                     }
 
                     sp_repr_css_attr_unref(css);
-                    css = 0;
+                    css = nullptr;
                     g_free(urltext);
 
                 } // end if
@@ -806,7 +806,7 @@ void FillNStroke::updateFromPaint()
 
                 sp_desktop_set_style(desktop, css);
                 sp_repr_css_attr_unref(css);
-                css = 0;
+                css = nullptr;
 
                 DocumentUndo::done(document, SP_VERB_DIALOG_FILL_STROKE,
                                    (kind == FILL) ? _("Unset fill") : _("Unset stroke"));
diff --git a/src/widgets/gimp/ruler.cpp b/src/widgets/gimp/ruler.cpp
index 8d73ada3b..f4f1a2f29 100644
--- a/src/widgets/gimp/ruler.cpp
+++ b/src/widgets/gimp/ruler.cpp
@@ -241,7 +241,7 @@ sp_ruler_class_init (SPRulerClass *klass)
 
   gtk_widget_class_install_style_property (widget_class,
 		                           g_param_spec_double ("font-scale",
-						                NULL, NULL,
+						                nullptr, nullptr,
 								0.0,
 								G_MAXDOUBLE,
 								DEFAULT_RULER_FONT_SCALE,
@@ -262,7 +262,7 @@ sp_ruler_init (SPRuler *ruler)
   priv->position             = 0;
   priv->max_size             = 0;
 
-  priv->backing_store        = NULL;
+  priv->backing_store        = nullptr;
   priv->backing_store_valid  = FALSE;
 
   priv->last_pos_rect.x      = 0;
@@ -498,7 +498,7 @@ sp_ruler_unrealize(GtkWidget *widget)
   if (priv->backing_store)
     {
       cairo_surface_destroy (priv->backing_store);
-      priv->backing_store = NULL;
+      priv->backing_store = nullptr;
     }
 
   priv->backing_store_valid = FALSE;
@@ -506,13 +506,13 @@ sp_ruler_unrealize(GtkWidget *widget)
   if (priv->layout)
     {
       g_object_unref (priv->layout);
-      priv->layout = NULL;
+      priv->layout = nullptr;
     }
 
   if (priv->input_window)
     {
       gdk_window_destroy (priv->input_window);
-      priv->input_window = NULL;
+      priv->input_window = nullptr;
     }
 
   GTK_WIDGET_CLASS (sp_ruler_parent_class)->unrealize (widget);
@@ -577,7 +577,7 @@ sp_ruler_size_request (GtkWidget      *widget,
   gint             size;
 
   layout = sp_ruler_get_layout (widget, "0123456789");
-  pango_layout_get_pixel_extents (layout, &ink_rect, NULL);
+  pango_layout_get_pixel_extents (layout, &ink_rect, nullptr);
 
   size = 2 + ink_rect.height * 1.7;
 
@@ -617,7 +617,7 @@ sp_ruler_style_updated (GtkWidget *widget)
   if (priv->layout)
     {
      g_object_unref (priv->layout);
-     priv->layout = NULL;
+     priv->layout = nullptr;
     }
 }
 
@@ -773,7 +773,7 @@ sp_ruler_update_position (SPRuler *ruler,
   gdouble         upper;
 
   gtk_widget_get_allocation (GTK_WIDGET (ruler), &allocation);
-  sp_ruler_get_range (ruler, &lower, &upper, NULL);
+  sp_ruler_get_range (ruler, &lower, &upper, nullptr);
 
   if (priv->orientation == GTK_ORIENTATION_HORIZONTAL)
     {
@@ -827,7 +827,7 @@ gtk_widget_get_translation_to_window (GtkWidget *widget,
       *y += px;
     }
 
-  if (w == NULL)
+  if (w == nullptr)
     {
       *x = 0;
       *y = 0;
@@ -1031,7 +1031,7 @@ sp_ruler_set_position (SPRuler *ruler,
           priv->pos_redraw_idle_id =
             g_idle_add_full (G_PRIORITY_LOW,
                              sp_ruler_idle_queue_pos_redraw,
-                             ruler, NULL);
+                             ruler, nullptr);
         }
     }
 }
@@ -1087,7 +1087,7 @@ sp_ruler_draw_ticks (SPRuler *ruler)
     gint             text_size;
     gint             pos;
     gdouble          max_size;
-    Inkscape::Util::Unit const *unit = NULL;
+    Inkscape::Util::Unit const *unit = nullptr;
     SPRulerMetric    ruler_metric = ruler_metric_general; /* The metric to use for this unit system */
     PangoLayout     *layout;
     PangoRectangle   logical_rect, ink_rect;
@@ -1251,7 +1251,7 @@ sp_ruler_draw_ticks (SPRuler *ruler)
                 if (priv->orientation == GTK_ORIENTATION_HORIZONTAL)
                   {
                     pango_layout_set_text (layout, unit_str, -1);
-                    pango_layout_get_extents (layout, &logical_rect, NULL);
+                    pango_layout_get_extents (layout, &logical_rect, nullptr);
 
                     cairo_move_to (cr,
                                    pos + 2,
@@ -1267,7 +1267,7 @@ sp_ruler_draw_ticks (SPRuler *ruler)
                       {
                         digit_str[0] = unit_str[j];
                         pango_layout_set_text (layout, digit_str, 1);
-                        pango_layout_get_extents (layout, NULL, &logical_rect);
+                        pango_layout_get_extents (layout, nullptr, &logical_rect);
 
                         cairo_move_to (cr,
                                        border.left + 1,
@@ -1337,7 +1337,7 @@ sp_ruler_get_pos_rect (SPRuler *ruler,
       rect.width = rect.height / 2 + 1;
     }
 
-  sp_ruler_get_range (ruler, &lower, &upper, NULL);
+  sp_ruler_get_range (ruler, &lower, &upper, nullptr);
 
   if (priv->orientation == GTK_ORIENTATION_HORIZONTAL)
     {
diff --git a/src/widgets/gradient-image.cpp b/src/widgets/gradient-image.cpp
index 65b1a6733..aae0cc063 100644
--- a/src/widgets/gradient-image.cpp
+++ b/src/widgets/gradient-image.cpp
@@ -57,7 +57,7 @@ sp_gradient_image_init (SPGradientImage *image)
 {
         gtk_widget_set_has_window (GTK_WIDGET(image), FALSE);
 
-        image->gradient = NULL;
+        image->gradient = nullptr;
 
         new (&image->release_connection) sigc::connection();
         new (&image->modified_connection) sigc::connection();
@@ -70,7 +70,7 @@ static void sp_gradient_image_destroy(GtkWidget *object)
         if (image->gradient) {
                 image->release_connection.disconnect();
                 image->modified_connection.disconnect();
-                image->gradient = NULL;
+                image->gradient = nullptr;
         }
 
         image->release_connection.~connection();
@@ -125,7 +125,7 @@ static gboolean sp_gradient_image_draw(GtkWidget *widget, cairo_t *ct)
 GtkWidget *
 sp_gradient_image_new (SPGradient *gradient)
 {
-        SPGradientImage *image = SP_GRADIENT_IMAGE(g_object_new(SP_TYPE_GRADIENT_IMAGE, NULL));
+        SPGradientImage *image = SP_GRADIENT_IMAGE(g_object_new(SP_TYPE_GRADIENT_IMAGE, nullptr));
 
         sp_gradient_image_set_gradient (image, gradient);
 
@@ -254,7 +254,7 @@ sp_gradient_image_gradient_release (SPObject *, SPGradientImage *image)
                 image->modified_connection.disconnect();
         }
 
-        image->gradient = NULL;
+        image->gradient = nullptr;
 
         sp_gradient_image_update (image);
 }
diff --git a/src/widgets/gradient-selector.cpp b/src/widgets/gradient-selector.cpp
index db2d7f028..230282e6d 100644
--- a/src/widgets/gradient-selector.cpp
+++ b/src/widgets/gradient-selector.cpp
@@ -67,28 +67,28 @@ static void sp_gradient_selector_class_init(SPGradientSelectorClass *klass)
                                         G_TYPE_FROM_CLASS(object_class),
                                         (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                         G_STRUCT_OFFSET (SPGradientSelectorClass, grabbed),
-					NULL, NULL,
+					nullptr, nullptr,
                                         g_cclosure_marshal_VOID__VOID,
                                         G_TYPE_NONE, 0);
     signals[DRAGGED] =  g_signal_new ("dragged",
                                         G_TYPE_FROM_CLASS(object_class),
                                         (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                         G_STRUCT_OFFSET (SPGradientSelectorClass, dragged),
-					NULL, NULL,
+					nullptr, nullptr,
                                         g_cclosure_marshal_VOID__VOID,
                                         G_TYPE_NONE, 0);
     signals[RELEASED] = g_signal_new ("released",
                                         G_TYPE_FROM_CLASS(object_class),
                                         (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                         G_STRUCT_OFFSET (SPGradientSelectorClass, released),
-					NULL, NULL,
+					nullptr, nullptr,
                                         g_cclosure_marshal_VOID__VOID,
                                         G_TYPE_NONE, 0);
     signals[CHANGED] =  g_signal_new ("changed",
                                         G_TYPE_FROM_CLASS(object_class),
                                         (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                         G_STRUCT_OFFSET (SPGradientSelectorClass, changed),
-					NULL, NULL,
+					nullptr, nullptr,
                                         g_cclosure_marshal_VOID__VOID,
                                         G_TYPE_NONE, 0);
 
@@ -120,7 +120,7 @@ static void sp_gradient_selector_init(SPGradientSelector *sel)
     sel->gradientSpread = SP_GRADIENT_SPREAD_PAD;
 
     /* Vectors */
-    sel->vectors = sp_gradient_vector_selector_new (NULL, NULL);
+    sel->vectors = sp_gradient_vector_selector_new (nullptr, nullptr);
     SPGradientVectorSelector *gvs = SP_GRADIENT_VECTOR_SELECTOR(sel->vectors);
     sel->store = gvs->store;
     sel->columns = gvs->columns;
@@ -223,11 +223,11 @@ static void sp_gradient_selector_dispose(GObject *object)
 
     if (sel->icon_renderer) {
         delete sel->icon_renderer;
-        sel->icon_renderer = NULL;
+        sel->icon_renderer = nullptr;
     }
     if (sel->text_renderer) {
         delete sel->text_renderer;
-        sel->text_renderer = NULL;
+        sel->text_renderer = nullptr;
     }
 
     if ((G_OBJECT_CLASS(sp_gradient_selector_parent_class))->dispose) {
@@ -244,7 +244,7 @@ void SPGradientSelector::setSpread(SPGradientSpread spread)
 
 GtkWidget *sp_gradient_selector_new()
 {
-    SPGradientSelector *sel = SP_GRADIENT_SELECTOR(g_object_new (SP_TYPE_GRADIENT_SELECTOR, NULL));
+    SPGradientSelector *sel = SP_GRADIENT_SELECTOR(g_object_new (SP_TYPE_GRADIENT_SELECTOR, nullptr));
 
     return GTK_WIDGET(sel);
 }
@@ -361,7 +361,7 @@ void SPGradientSelector::onTreeSelection()
         return;
     }
 
-    SPGradient *obj = NULL;
+    SPGradient *obj = nullptr;
     /* Single selection */
     Gtk::TreeModel::iterator iter = sel->get_selected();
     if ( iter ) {
@@ -370,7 +370,7 @@ void SPGradientSelector::onTreeSelection()
     }
 
     if (obj) {
-        sp_gradient_selector_vector_set (NULL, SP_GRADIENT(obj), this);
+        sp_gradient_selector_vector_set (nullptr, SP_GRADIENT(obj), this);
     }
 }
 
@@ -451,7 +451,7 @@ void SPGradientSelector::setVector(SPDocument *doc, SPGradient *vector)
             gtk_widget_set_sensitive(edit, FALSE);
         }
         if (add) {
-            gtk_widget_set_sensitive(add, (doc != NULL));
+            gtk_widget_set_sensitive(add, (doc != nullptr));
         }
         if (del) {
             gtk_widget_set_sensitive(del, FALSE);
@@ -472,7 +472,7 @@ static void sp_gradient_selector_vector_set(SPGradientVectorSelector * /*gvs*/,
     if (!sel->blocked) {
         sel->blocked = TRUE;
         gr = sp_gradient_ensure_vector_normalized (gr);
-        sel->setVector((gr) ? gr->document : 0, gr);
+        sel->setVector((gr) ? gr->document : nullptr, gr);
         g_signal_emit (G_OBJECT (sel), signals[CHANGED], 0, gr);
         sel->blocked = FALSE;
     }
@@ -487,7 +487,7 @@ sp_gradient_selector_delete_vector_clicked (GtkWidget */*w*/, SPGradientSelector
         return;
     }
 
-    SPGradient *obj = NULL;
+    SPGradient *obj = nullptr;
     /* Single selection */
     Gtk::TreeModel::iterator iter = selection->get_selected();
     if ( iter ) {
@@ -516,7 +516,7 @@ sp_gradient_selector_edit_vector_clicked (GtkWidget */*w*/, SPGradientSelector *
         if ( verb ) {
             SPAction *action = verb->get_action( Inkscape::ActionContext( ( Inkscape::UI::View::View * ) SP_ACTIVE_DESKTOP ) );
             if ( action ) {
-                sp_action_perform( action, NULL );
+                sp_action_perform( action, nullptr );
             }
         }
     }
@@ -533,14 +533,14 @@ sp_gradient_selector_add_vector_clicked (GtkWidget */*w*/, SPGradientSelector *s
     SPGradient *gr = sp_gradient_vector_selector_get_gradient( SP_GRADIENT_VECTOR_SELECTOR (sel->vectors));
     Inkscape::XML::Document *xml_doc = doc->getReprDoc();
 
-    Inkscape::XML::Node *repr = NULL;
+    Inkscape::XML::Node *repr = nullptr;
 
     if (gr) {
         repr = gr->getRepr()->duplicate(xml_doc);
         // Rename the new gradients id to be similar to the cloned gradients
         Glib::ustring old_id = gr->getId();
         rename_id(gr, old_id);
-        doc->getDefs()->getRepr()->addChild(repr, NULL);
+        doc->getDefs()->getRepr()->addChild(repr, nullptr);
     } else {
         repr = xml_doc->createElement("svg:linearGradient");
         Inkscape::XML::Node *stop = xml_doc->createElement("svg:stop");
@@ -553,7 +553,7 @@ sp_gradient_selector_add_vector_clicked (GtkWidget */*w*/, SPGradientSelector *s
         stop->setAttribute("style", "stop-color:#fff;stop-opacity:1;");
         repr->appendChild(stop);
         Inkscape::GC::release(stop);
-        doc->getDefs()->getRepr()->addChild(repr, NULL);
+        doc->getDefs()->getRepr()->addChild(repr, nullptr);
         gr = SP_GRADIENT(doc->getObjectByRepr(repr));
     }
     
diff --git a/src/widgets/gradient-vector.cpp b/src/widgets/gradient-vector.cpp
index 412f0b7e2..26f3fc505 100644
--- a/src/widgets/gradient-vector.cpp
+++ b/src/widgets/gradient-vector.cpp
@@ -87,7 +87,7 @@ unsigned long sp_gradient_to_hhssll(SPGradient *gr);
 static guint signals[LAST_SIGNAL] = {0};
 
 // TODO FIXME kill these globals!!!
-static GtkWidget *dlg = NULL;
+static GtkWidget *dlg = nullptr;
 static win_data wd;
 static gint x = -1000, y = -1000, w = 0, h = 0; // impossible original values to make sure they are read from prefs
 static Glib::ustring const prefs_path = "/dialogs/gradienteditor/";
@@ -102,7 +102,7 @@ static void sp_gradient_vector_selector_class_init(SPGradientVectorSelectorClass
                                         G_TYPE_FROM_CLASS(gobject_class),
                                         G_SIGNAL_RUN_LAST,
                                         G_STRUCT_OFFSET(SPGradientVectorSelectorClass, vector_set),
-                                        NULL, NULL,
+                                        nullptr, nullptr,
                                         g_cclosure_marshal_VOID__POINTER,
                                         G_TYPE_NONE, 1,
                                         G_TYPE_POINTER);
@@ -119,8 +119,8 @@ static void sp_gradient_vector_selector_init(SPGradientVectorSelector *gvs)
 
     gvs->swatched = false;
 
-    gvs->doc = NULL;
-    gvs->gr = NULL;
+    gvs->doc = nullptr;
+    gvs->gr = nullptr;
 
     new (&gvs->gradient_release_connection) sigc::connection();
     new (&gvs->defs_release_connection) sigc::connection();
@@ -139,13 +139,13 @@ static void sp_gradient_vector_selector_destroy(GtkWidget *object)
     if (gvs->gr) {
         gvs->gradient_release_connection.disconnect();
         gvs->tree_select_connection.disconnect();
-        gvs->gr = NULL;
+        gvs->gr = nullptr;
     }
 
     if (gvs->doc) {
         gvs->defs_release_connection.disconnect();
         gvs->defs_modified_connection.disconnect();
-        gvs->doc = NULL;
+        gvs->doc = nullptr;
     }
 
     gvs->gradient_release_connection.~connection();
@@ -165,7 +165,7 @@ GtkWidget *sp_gradient_vector_selector_new(SPDocument *doc, SPGradient *gr)
     g_return_val_if_fail(!gr || SP_IS_GRADIENT(gr), NULL);
     g_return_val_if_fail(!gr || (gr->document == doc), NULL);
 
-    gvs = static_cast<GtkWidget*>(g_object_new(SP_TYPE_GRADIENT_VECTOR_SELECTOR, NULL));
+    gvs = static_cast<GtkWidget*>(g_object_new(SP_TYPE_GRADIENT_VECTOR_SELECTOR, nullptr));
 
     if (doc) {
         sp_gradient_vector_selector_set_gradient(SP_GRADIENT_VECTOR_SELECTOR(gvs), doc, gr);
@@ -184,9 +184,9 @@ void sp_gradient_vector_selector_set_gradient(SPGradientVectorSelector *gvs, SPD
 //               (gr ? gr->isSolid() : -1));
     static gboolean suppress = FALSE;
 
-    g_return_if_fail(gvs != NULL);
+    g_return_if_fail(gvs != nullptr);
     g_return_if_fail(SP_IS_GRADIENT_VECTOR_SELECTOR(gvs));
-    g_return_if_fail(!gr || (doc != NULL));
+    g_return_if_fail(!gr || (doc != nullptr));
     g_return_if_fail(!gr || SP_IS_GRADIENT(gr));
     g_return_if_fail(!gr || (gr->document == doc));
     g_return_if_fail(!gr || gr->hasStops());
@@ -195,12 +195,12 @@ void sp_gradient_vector_selector_set_gradient(SPGradientVectorSelector *gvs, SPD
         /* Disconnect signals */
         if (gvs->gr) {
             gvs->gradient_release_connection.disconnect();
-            gvs->gr = NULL;
+            gvs->gr = nullptr;
         }
         if (gvs->doc) {
             gvs->defs_release_connection.disconnect();
             gvs->defs_modified_connection.disconnect();
-            gvs->doc = NULL;
+            gvs->doc = nullptr;
         }
 
         // Connect signals
@@ -219,7 +219,7 @@ void sp_gradient_vector_selector_set_gradient(SPGradientVectorSelector *gvs, SPD
         // Harder case - keep document, rebuild list and stuff
         // fixme: (Lauris)
         suppress = TRUE;
-        sp_gradient_vector_selector_set_gradient(gvs, NULL, NULL);
+        sp_gradient_vector_selector_set_gradient(gvs, nullptr, nullptr);
         sp_gradient_vector_selector_set_gradient(gvs, doc, gr);
         suppress = FALSE;
         g_signal_emit(G_OBJECT(gvs), signals[VECTOR_SET], 0, gr);
@@ -229,7 +229,7 @@ void sp_gradient_vector_selector_set_gradient(SPGradientVectorSelector *gvs, SPD
 
 SPDocument *sp_gradient_vector_selector_get_document(SPGradientVectorSelector *gvs)
 {
-    g_return_val_if_fail(gvs != NULL, NULL);
+    g_return_val_if_fail(gvs != nullptr, NULL);
     g_return_val_if_fail(SP_IS_GRADIENT_VECTOR_SELECTOR(gvs), NULL);
 
     return gvs->doc;
@@ -237,7 +237,7 @@ SPDocument *sp_gradient_vector_selector_get_document(SPGradientVectorSelector *g
 
 SPGradient *sp_gradient_vector_selector_get_gradient(SPGradientVectorSelector *gvs)
 {
-    g_return_val_if_fail(gvs != NULL, NULL);
+    g_return_val_if_fail(gvs != nullptr, NULL);
     g_return_val_if_fail(SP_IS_GRADIENT_VECTOR_SELECTOR(gvs), NULL);
 
     return gvs->gr;
@@ -365,7 +365,7 @@ static SPGradient * gr_item_get_gradient(SPItem *item, gboolean fillorstroke)
         }
     }
 
-    return NULL;
+    return nullptr;
 }
 
 /*
@@ -382,7 +382,7 @@ void gr_get_usage_counts(SPDocument *doc, std::map<SPGradient *, gint> *mapUsage
     for (auto item:all_list) {
         if (!item->getId())
             continue;
-        SPGradient *gr = NULL;
+        SPGradient *gr = nullptr;
         gr = gr_item_get_gradient(item, true); // fill
         if (gr) {
             mapUsageCount->count(gr) > 0 ? (*mapUsageCount)[gr] += 1 : (*mapUsageCount)[gr] = 1;
@@ -399,7 +399,7 @@ static void sp_gvs_gradient_release(SPObject */*obj*/, SPGradientVectorSelector
     /* Disconnect gradient */
     if (gvs->gr) {
         gvs->gradient_release_connection.disconnect();
-        gvs->gr = NULL;
+        gvs->gr = nullptr;
     }
 
     /* Rebuild GUI */
@@ -408,7 +408,7 @@ static void sp_gvs_gradient_release(SPObject */*obj*/, SPGradientVectorSelector
 
 static void sp_gvs_defs_release(SPObject */*defs*/, SPGradientVectorSelector *gvs)
 {
-    gvs->doc = NULL;
+    gvs->doc = nullptr;
 
     gvs->defs_release_connection.disconnect();
     gvs->defs_modified_connection.disconnect();
@@ -416,7 +416,7 @@ static void sp_gvs_defs_release(SPObject */*defs*/, SPGradientVectorSelector *gv
     /* Disconnect gradient as well */
     if (gvs->gr) {
         gvs->gradient_release_connection.disconnect();
-        gvs->gr = NULL;
+        gvs->gr = nullptr;
     }
 
     /* Rebuild GUI */
@@ -463,7 +463,7 @@ static void grad_edit_dia_stop_added_or_removed(Inkscape::XML::Node */*repr*/, I
 {
     GtkWidget *vb = GTK_WIDGET(data);
     SPGradient *gradient = static_cast<SPGradient *>(g_object_get_data(G_OBJECT(vb), "gradient"));
-    update_stop_list(vb, gradient, NULL);
+    update_stop_list(vb, gradient, nullptr);
 }
 
 //FIXME!!! We must also listen to attr changes on all children (i.e. stops) too,
@@ -473,15 +473,15 @@ static Inkscape::XML::NodeEventVector grad_edit_dia_repr_events =
 {
     grad_edit_dia_stop_added_or_removed, /* child_added */
     grad_edit_dia_stop_added_or_removed, /* child_removed */
-    NULL, /* attr_changed*/
-    NULL, /* content_changed */
-    NULL  /* order_changed */
+    nullptr, /* attr_changed*/
+    nullptr, /* content_changed */
+    nullptr  /* order_changed */
 };
 
 static void verify_grad(SPGradient *gradient)
 {
     int i = 0;
-    SPStop *stop = NULL;
+    SPStop *stop = nullptr;
     /* count stops */
     for (auto& ochild: gradient->children) {
         if (SP_IS_STOP(&ochild)) {
@@ -502,13 +502,13 @@ static void verify_grad(SPGradient *gradient)
         child = xml_doc->createElement("svg:stop");
         sp_repr_set_css_double(child, "offset", 0.0);
         child->setAttribute("style", os.str().c_str());
-        gradient->getRepr()->addChild(child, NULL);
+        gradient->getRepr()->addChild(child, nullptr);
         Inkscape::GC::release(child);
 
         child = xml_doc->createElement("svg:stop");
         sp_repr_set_css_double(child, "offset", 1.0);
         child->setAttribute("style", os.str().c_str());
-        gradient->getRepr()->addChild(child, NULL);
+        gradient->getRepr()->addChild(child, nullptr);
         Inkscape::GC::release(child);
         return;
     }
@@ -586,7 +586,7 @@ static void update_stop_list( GtkWidget *vb, SPGradient *gradient, SPStop *new_s
     }
 
     /* Set history */
-    if (new_stop == NULL) {
+    if (new_stop == nullptr) {
         gtk_combo_box_set_active (GTK_COMBO_BOX(combo_box) , 0);
     } else {
         select_stop_in_list(vb, gradient, new_stop);
@@ -618,18 +618,18 @@ static void sp_grad_edit_combo_box_changed (GtkComboBox * /*widget*/, GtkWidget
 
     bool isEndStop = false;
 
-    SPStop *prev = NULL;
+    SPStop *prev = nullptr;
     prev = stop->getPrevStop();
-    if (prev != NULL )  {
+    if (prev != nullptr )  {
         gtk_adjustment_set_lower (adj, prev->offset);
     } else {
         isEndStop = true;
         gtk_adjustment_set_lower (adj, 0);
     }
 
-    SPStop *next = NULL;
+    SPStop *next = nullptr;
     next = stop->getNextStop();
-    if (next != NULL ) {
+    if (next != nullptr ) {
         gtk_adjustment_set_upper (adj, next->offset);
     } else {
         isEndStop = true;
@@ -654,7 +654,7 @@ static void sp_grad_edit_combo_box_changed (GtkComboBox * /*widget*/, GtkWidget
 
 static SPStop *get_selected_stop( GtkWidget *vb)
 {
-    SPStop *stop = NULL;
+    SPStop *stop = nullptr;
     GtkWidget *combo_box = static_cast<GtkWidget *>(g_object_get_data(G_OBJECT(vb), "combo_box"));
     if (combo_box) {
         GtkTreeIter  iter;
@@ -706,19 +706,19 @@ static void sp_grd_ed_add_stop(GtkWidget */*widget*/,  GtkWidget *vb)
         return;
     }
 
-    Inkscape::XML::Node *new_stop_repr = NULL;
+    Inkscape::XML::Node *new_stop_repr = nullptr;
 
     SPStop *next = stop->getNextStop();
 
-    if (next == NULL) {
+    if (next == nullptr) {
         SPStop *prev = stop->getPrevStop();
-        if (prev != NULL) {
+        if (prev != nullptr) {
             next = stop;
             stop = prev;
         }
     }
 
-    if (next != NULL) {
+    if (next != nullptr) {
         new_stop_repr = stop->getRepr()->duplicate(gradient->getRepr()->document());
         gradient->getRepr()->addChild(new_stop_repr, stop->getRepr());
     } else {
@@ -782,7 +782,7 @@ static void sp_grd_ed_del_stop(GtkWidget */*widget*/,  GtkWidget *vb)
 
         gradient->getRepr()->removeChild(stop->getRepr());
         sp_gradient_vector_widget_load_gradient(vb, gradient);
-        update_stop_list(GTK_WIDGET(vb), gradient, NULL);
+        update_stop_list(GTK_WIDGET(vb), gradient, nullptr);
         DocumentUndo::done(gradient->document, SP_VERB_CONTEXT_GRADIENT,
                            _("Delete gradient stop"));
     }
@@ -795,7 +795,7 @@ static GtkWidget * sp_gradient_vector_widget_new(SPGradient *gradient, SPStop *s
 
     GtkWidget *vb, *w, *f;
 
-    g_return_val_if_fail(gradient != NULL, NULL);
+    g_return_val_if_fail(gradient != nullptr, NULL);
     g_return_val_if_fail(SP_IS_GRADIENT(gradient), NULL);
 
     vb = gtk_box_new(GTK_ORIENTATION_VERTICAL, PAD);
@@ -827,7 +827,7 @@ static GtkWidget * sp_gradient_vector_widget_new(SPGradient *gradient, SPStop *s
     gtk_box_pack_start(GTK_BOX(vb), combo_box, FALSE, FALSE, 0);
     g_object_set_data(G_OBJECT(vb), "combo_box", combo_box);
 
-    update_stop_list(GTK_WIDGET(vb), gradient, NULL);
+    update_stop_list(GTK_WIDGET(vb), gradient, nullptr);
 
     g_signal_connect(G_OBJECT(combo_box), "changed", G_CALLBACK(sp_grad_edit_combo_box_changed), vb);
 
@@ -861,13 +861,13 @@ static GtkWidget * sp_gradient_vector_widget_new(SPGradient *gradient, SPStop *s
     gtk_widget_show(l);
 
     /* Adjustment */
-    GtkAdjustment *Offset_adj = NULL;
+    GtkAdjustment *Offset_adj = nullptr;
     Offset_adj= GTK_ADJUSTMENT(gtk_adjustment_new(0.0, 0.0, 1.0, 0.01, 0.01, 0.0));
     g_object_set_data(G_OBJECT(vb), "offset", Offset_adj);
 
     SPStop *stop = get_selected_stop(vb);
     if (!stop) {
-        return NULL;
+        return nullptr;
     }
 
     gtk_adjustment_set_value(Offset_adj, stop->offset);
@@ -940,7 +940,7 @@ static GtkWidget * sp_gradient_vector_widget_new(SPGradient *gradient, SPStop *s
 
 GtkWidget * sp_gradient_vector_editor_new(SPGradient *gradient, SPStop *stop)
 {
-    if (dlg == NULL) {
+    if (dlg == nullptr) {
         Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
         dlg = sp_window_new(_("Gradient editor"), TRUE);
@@ -973,7 +973,7 @@ GtkWidget * sp_gradient_vector_editor_new(SPGradient *gradient, SPStop *stop)
         wd.stop = 0;
 
         GObject *obj = G_OBJECT(dlg);
-        sigc::connection *conn = NULL;
+        sigc::connection *conn = nullptr;
 
         conn = new sigc::connection(INKSCAPE.signal_activate_desktop.connect(sigc::bind(sigc::ptr_fun(&sp_transientize_callback), &wd)));
         g_object_set_data(obj, "desktop-activate-connection", conn);
@@ -984,7 +984,7 @@ GtkWidget * sp_gradient_vector_editor_new(SPGradient *gradient, SPStop *stop)
 
         conn = new sigc::connection(INKSCAPE.signal_shut_down.connect(
             sigc::hide_return(
-            sigc::bind(sigc::ptr_fun(&sp_gradient_vector_dialog_delete), (GtkWidget *) NULL, (GdkEvent *) NULL, (GtkWidget *) NULL)
+            sigc::bind(sigc::ptr_fun(&sp_gradient_vector_dialog_delete), (GtkWidget *) nullptr, (GdkEvent *) nullptr, (GtkWidget *) nullptr)
         )));
         g_object_set_data(obj, "shutdown-connection", conn);
 
@@ -1017,7 +1017,7 @@ GtkWidget * sp_gradient_vector_editor_new(SPGradient *gradient, SPStop *stop)
         gtk_main_do_event(reinterpret_cast<GdkEvent*>(&event));
         g_object_unref(G_OBJECT(event.window));
 
-        g_assert(dlg == NULL);
+        g_assert(dlg == nullptr);
         sp_gradient_vector_editor_new(gradient, stop);
     }
 
@@ -1040,8 +1040,8 @@ static void sp_gradient_vector_widget_load_gradient(GtkWidget *widget, SPGradien
         modified_connection = static_cast<sigc::connection *>(g_object_get_data(G_OBJECT(widget), "gradient_modified_connection"));
 
         if (old) {
-            g_assert( release_connection != NULL );
-            g_assert( modified_connection != NULL );
+            g_assert( release_connection != nullptr );
+            g_assert( modified_connection != nullptr );
             release_connection->disconnect();
             modified_connection->disconnect();
             sp_signal_disconnect_by_data(old, widget);
@@ -1059,11 +1059,11 @@ static void sp_gradient_vector_widget_load_gradient(GtkWidget *widget, SPGradien
         } else {
             if (release_connection) {
                 delete release_connection;
-                release_connection = NULL;
+                release_connection = nullptr;
             }
             if (modified_connection) {
                 delete modified_connection;
-                modified_connection = NULL;
+                modified_connection = nullptr;
             }
         }
 
@@ -1094,14 +1094,14 @@ static void sp_gradient_vector_widget_load_gradient(GtkWidget *widget, SPGradien
         GtkWidget *w = static_cast<GtkWidget *>(g_object_get_data(G_OBJECT(widget), "preview"));
         sp_gradient_image_set_gradient(SP_GRADIENT_IMAGE(w), gradient);
 
-        update_stop_list(GTK_WIDGET(widget), gradient, NULL);
+        update_stop_list(GTK_WIDGET(widget), gradient, nullptr);
 
         // Once the user edits a gradient, it stops being auto-collectable
         if (gradient->getRepr()->attribute("inkscape:collect")) {
             SPDocument *document = gradient->document;
             bool saved = DocumentUndo::getUndoSensitive(document);
             DocumentUndo::setUndoSensitive(document, false);
-            gradient->getRepr()->setAttribute("inkscape:collect", NULL);
+            gradient->getRepr()->setAttribute("inkscape:collect", nullptr);
             DocumentUndo::setUndoSensitive(document, saved);
         }
     } else { // no gradient, disable everything
@@ -1136,7 +1136,7 @@ static void sp_gradient_vector_dialog_destroy(GtkWidget * /*object*/, gpointer /
     conn->disconnect();
     delete conn;
 
-    wd.win = dlg = NULL;
+    wd.win = dlg = nullptr;
     wd.stop = 0;
 }
 
@@ -1170,8 +1170,8 @@ static void sp_gradient_vector_widget_destroy(GtkWidget *object, gpointer /*data
     sigc::connection *modified_connection = static_cast<sigc::connection *>(g_object_get_data(G_OBJECT(object), "gradient_modified_connection"));
 
     if (gradient) {
-        g_assert( release_connection != NULL );
-        g_assert( modified_connection != NULL );
+        g_assert( release_connection != nullptr );
+        g_assert( modified_connection != nullptr );
         release_connection->disconnect();
         modified_connection->disconnect();
         sp_signal_disconnect_by_data(gradient, object);
@@ -1184,13 +1184,13 @@ static void sp_gradient_vector_widget_destroy(GtkWidget *object, gpointer /*data
     SelectedColor *selected_color = static_cast<SelectedColor *>(g_object_get_data(G_OBJECT(object), "cselector"));
     if (selected_color) {
         delete selected_color;
-        g_object_set_data(G_OBJECT(object), "cselector", NULL);
+        g_object_set_data(G_OBJECT(object), "cselector", nullptr);
     }
 }
 
 static void sp_gradient_vector_gradient_release(SPObject */*object*/, GtkWidget *widget)
 {
-    sp_gradient_vector_widget_load_gradient(widget, NULL);
+    sp_gradient_vector_widget_load_gradient(widget, nullptr);
 }
 
 static void sp_gradient_vector_gradient_modified(SPObject *object, guint /*flags*/, GtkWidget *widget)
@@ -1267,7 +1267,7 @@ static void sp_gradient_vector_color_changed(Inkscape::UI::SelectedColor *select
 
     /* Set start parameters */
     /* We rely on normalized vector, i.e. stops HAVE to exist */
-    g_return_if_fail(ngr->getFirstStop() != NULL);
+    g_return_if_fail(ngr->getFirstStop() != nullptr);
 
     SPStop *stop = get_selected_stop(GTK_WIDGET(object));
     if (!stop) {
diff --git a/src/widgets/gradient-vector.h b/src/widgets/gradient-vector.h
index b51b276b9..793f37384 100644
--- a/src/widgets/gradient-vector.h
+++ b/src/widgets/gradient-vector.h
@@ -72,7 +72,7 @@ SPDocument *sp_gradient_vector_selector_get_document (SPGradientVectorSelector *
 SPGradient *sp_gradient_vector_selector_get_gradient (SPGradientVectorSelector *gvs);
 
 /* fixme: rethink this (Lauris) */
-GtkWidget *sp_gradient_vector_editor_new (SPGradient *gradient, SPStop *stop = NULL);
+GtkWidget *sp_gradient_vector_editor_new (SPGradient *gradient, SPStop *stop = nullptr);
 
 guint32 sp_average_color(guint32 c1, guint32 c2, gdouble p = 0.5);
 
diff --git a/src/widgets/ink-action.cpp b/src/widgets/ink-action.cpp
index dae214656..5adb69ac6 100644
--- a/src/widgets/ink-action.cpp
+++ b/src/widgets/ink-action.cpp
@@ -63,7 +63,7 @@ static void ink_action_class_init( InkActionClass* klass )
 static void ink_action_init( InkAction* action )
 {
     action->private_data = INK_ACTION_GET_PRIVATE( action );
-    action->private_data->iconId = 0;
+    action->private_data->iconId = nullptr;
     action->private_data->iconSize = GTK_ICON_SIZE_SMALL_TOOLBAR;
 }
 
diff --git a/src/widgets/ink-comboboxentry-action.cpp b/src/widgets/ink-comboboxentry-action.cpp
index 133ae7878..5aace3f34 100644
--- a/src/widgets/ink-comboboxentry-action.cpp
+++ b/src/widgets/ink-comboboxentry-action.cpp
@@ -287,7 +287,7 @@ ink_comboboxentry_action_class_init (Ink_ComboBoxEntry_ActionClass *klass)
                                    G_TYPE_FROM_CLASS(klass),
                                    G_SIGNAL_RUN_FIRST,
                                    G_STRUCT_OFFSET(Ink_ComboBoxEntry_ActionClass, changed),
-                                   NULL, NULL,
+                                   nullptr, nullptr,
                                    g_cclosure_marshal_VOID__VOID,
                                    G_TYPE_NONE, 0);
 
@@ -296,7 +296,7 @@ ink_comboboxentry_action_class_init (Ink_ComboBoxEntry_ActionClass *klass)
                                    G_TYPE_FROM_CLASS(klass),
                                    G_SIGNAL_RUN_FIRST,
                                    G_STRUCT_OFFSET(Ink_ComboBoxEntry_ActionClass, activated),
-                                   NULL, NULL,
+                                   nullptr, nullptr,
                                    g_cclosure_marshal_VOID__VOID,
                                    G_TYPE_NONE, 0);
 
@@ -306,19 +306,19 @@ static void ink_comboboxentry_action_init (Ink_ComboBoxEntry_Action *action)
 {
   action->active = -1;
   action->text = strdup("");
-  action->entry_completion = NULL;
-  action->indicator = NULL;
+  action->entry_completion = nullptr;
+  action->indicator = nullptr;
   action->popup = false;
-  action->info = NULL;
-  action->info_cb = NULL;
+  action->info = nullptr;
+  action->info_cb = nullptr;
   action->info_cb_id = 0;
   action->info_cb_blocked = false;
-  action->warning = NULL;
-  action->warning_cb = NULL;
+  action->warning = nullptr;
+  action->warning_cb = nullptr;
   action->warning_cb_id = 0;
   action->warning_cb_blocked = false;
-  action->altx_name = NULL;
-  action->focusWidget = NULL;
+  action->altx_name = nullptr;
+  action->focusWidget = nullptr;
 }
 
 Ink_ComboBoxEntry_Action *ink_comboboxentry_action_new (const gchar   *name,
@@ -332,7 +332,7 @@ Ink_ComboBoxEntry_Action *ink_comboboxentry_action_new (const gchar   *name,
                                                         void          *separator_func,
                                                         GtkWidget      *focusWidget)
 {
-  g_return_val_if_fail (name != NULL, NULL);
+  g_return_val_if_fail (name != nullptr, NULL);
 
   return (Ink_ComboBoxEntry_Action*)g_object_new (INK_COMBOBOXENTRY_TYPE_ACTION,
                                                   "name",           name,
@@ -351,15 +351,15 @@ Ink_ComboBoxEntry_Action *ink_comboboxentry_action_new (const gchar   *name,
 // Create a widget for a toolbar.
 GtkWidget* create_tool_item( GtkAction* action )
 {
-  GtkWidget* item = 0;
+  GtkWidget* item = nullptr;
 
   if ( INK_COMBOBOXENTRY_IS_ACTION( action ) && INK_COMBOBOXENTRY_ACTION(action)->model ) {
 
     Ink_ComboBoxEntry_Action* ink_comboboxentry_action = INK_COMBOBOXENTRY_ACTION( action );
 
     gchar *action_name = g_strdup( gtk_action_get_name( action ) );
-    gchar *combobox_name = g_strjoin( NULL, action_name, "_combobox", NULL );
-    gchar *entry_name =    g_strjoin( NULL, action_name, "_entry", NULL );
+    gchar *combobox_name = g_strjoin( nullptr, action_name, "_combobox", NULL );
+    gchar *entry_name =    g_strjoin( nullptr, action_name, "_entry", NULL );
     g_free( action_name );
 
     item = GTK_WIDGET( gtk_tool_item_new() );
@@ -386,10 +386,10 @@ GtkWidget* create_tool_item( GtkAction* action )
     g_signal_connect( G_OBJECT(comboBoxEntry), "changed", G_CALLBACK(combo_box_changed_cb), action );
 
     // Optionally add separator function...
-    if( ink_comboboxentry_action->separator_func != NULL ) {
+    if( ink_comboboxentry_action->separator_func != nullptr ) {
        gtk_combo_box_set_row_separator_func( ink_comboboxentry_action->combobox,
 					    GtkTreeViewRowSeparatorFunc (ink_comboboxentry_action->separator_func),
-      					    NULL, NULL );
+      					    nullptr, nullptr );
     }
 
     // FIXME: once gtk3 migration is done this can be removed
@@ -397,19 +397,19 @@ GtkWidget* create_tool_item( GtkAction* action )
     gtk_widget_show_all (comboBoxEntry);
 
     // Optionally add formatting...
-    if( ink_comboboxentry_action->cell_data_func != NULL ) {
+    if( ink_comboboxentry_action->cell_data_func != nullptr ) {
       GtkCellRenderer *cell = gtk_cell_renderer_text_new();
       gtk_cell_layout_clear( GTK_CELL_LAYOUT( comboBoxEntry ) );
       gtk_cell_layout_pack_start( GTK_CELL_LAYOUT( comboBoxEntry ), cell, true );
       gtk_cell_layout_set_cell_data_func (GTK_CELL_LAYOUT( comboBoxEntry ), cell,
                                           GtkCellLayoutDataFunc (ink_comboboxentry_action->cell_data_func),
-                                          NULL, NULL );
+                                          nullptr, nullptr );
     }
 
     // Optionally widen the combobox width... which widens the drop-down list in list mode.
     if( ink_comboboxentry_action->extra_width > 0 ) {
       GtkRequisition req;
-      gtk_widget_get_preferred_size(GTK_WIDGET(ink_comboboxentry_action->combobox), &req, NULL);
+      gtk_widget_get_preferred_size(GTK_WIDGET(ink_comboboxentry_action->combobox), &req, nullptr);
       gtk_widget_set_size_request( GTK_WIDGET( ink_comboboxentry_action->combobox ),
 				   req.width + ink_comboboxentry_action->extra_width, -1 );
     }
@@ -460,7 +460,7 @@ GtkWidget* create_tool_item( GtkAction* action )
 // Create a drop-down menu.
 GtkWidget* create_menu_item( GtkAction* action )
 {
-  GtkWidget* item = 0;
+  GtkWidget* item = nullptr;
 
     item = GTK_ACTION_CLASS(ink_comboboxentry_action_parent_class)->create_menu_item( action );
     g_warning( "ink_comboboxentry_action: create_menu_item not implemented" );
@@ -535,7 +535,7 @@ gboolean ink_comboboxentry_action_set_active_text( Ink_ComboBoxEntry_Action* act
     }
 
     bool set = false;
-    if( action->warning != NULL ) {
+    if( action->warning != nullptr ) {
       Glib::ustring missing = check_comma_separated_text( action );
       if( !missing.empty() ) {
 	  gtk_entry_set_icon_from_icon_name( action->entry,
@@ -570,7 +570,7 @@ gboolean ink_comboboxentry_action_set_active_text( Ink_ComboBoxEntry_Action* act
       }
     }
  
-    if( !set && action->info != NULL ) {
+    if( !set && action->info != nullptr ) {
       gtk_entry_set_icon_from_icon_name( GTK_ENTRY(action->entry),
 					 GTK_ENTRY_ICON_SECONDARY,
 					 INKSCAPE_ICON("edit-select-all") );
@@ -600,7 +600,7 @@ gboolean ink_comboboxentry_action_set_active_text( Ink_ComboBoxEntry_Action* act
     if( !set ) {
       gtk_entry_set_icon_from_icon_name( GTK_ENTRY(action->entry),
 					 GTK_ENTRY_ICON_SECONDARY,
-					 NULL );
+					 nullptr );
     }
   }
 
@@ -626,7 +626,7 @@ void ink_comboboxentry_action_set_extra_width( Ink_ComboBoxEntry_Action* action,
   // Widget may not have been created....
   if( action->combobox ) {
     GtkRequisition req;
-    gtk_widget_get_preferred_size(GTK_WIDGET(action->combobox), &req, NULL);
+    gtk_widget_get_preferred_size(GTK_WIDGET(action->combobox), &req, nullptr);
     gtk_widget_set_size_request( GTK_WIDGET( action->combobox ), req.width + action->extra_width, -1 );
   }
 }
@@ -662,7 +662,7 @@ void ink_comboboxentry_action_popup_disable( Ink_ComboBoxEntry_Action* action )
 
   if( action->entry_completion ) {
     gtk_widget_destroy(GTK_WIDGET(action->entry_completion));
-    action->entry_completion = 0;
+    action->entry_completion = nullptr;
   }
 }
 void     ink_comboboxentry_action_set_tooltip( Ink_ComboBoxEntry_Action* action, const gchar* tooltip ) {
@@ -748,7 +748,7 @@ gint get_active_row_from_text( Ink_ComboBoxEntry_Action* action, const gchar* ta
 
     if( check ) {
       // Get text from list entry
-      gchar* text = 0;
+      gchar* text = nullptr;
       gtk_tree_model_get( action->model, &iter, 0, &text, -1 ); // Column 0
 
       if( !ignore_case ) {
@@ -801,7 +801,7 @@ static Glib::ustring check_comma_separated_text( Ink_ComboBoxEntry_Action* actio
   gchar** tokens = g_strsplit( action->text, ",", 0 );
 
   gint i = 0;
-  while( tokens[i] != NULL ) {
+  while( tokens[i] != nullptr ) {
 
     // Remove any surrounding white space.
     g_strstrip( tokens[i] );
@@ -842,7 +842,7 @@ static void combo_box_changed_cb( GtkComboBox* widget, gpointer data ) {
     GtkTreeIter iter;
     if( gtk_combo_box_get_active_iter( GTK_COMBO_BOX( action->combobox ), &iter ) ) {
 
-      gchar* text = 0;
+      gchar* text = nullptr;
       gtk_tree_model_get( action->model, &iter, 0, &text, -1 );
       gtk_entry_set_text( action->entry, text );
 
@@ -885,7 +885,7 @@ static gboolean match_selected_cb( GtkEntryCompletion* /*widget*/, GtkTreeModel*
   GtkEntry *entry = action->entry;
 
   if( entry) {
-    gchar *family = 0;
+    gchar *family = nullptr;
     gtk_tree_model_get(model, iter, 0, &family, -1);
 
     // Set text in GtkEntry
@@ -924,7 +924,7 @@ gboolean keypress_cb( GtkWidget * /*widget*/, GdkEventKey *event, gpointer data
     Ink_ComboBoxEntry_Action* action = INK_COMBOBOXENTRY_ACTION( data );
     gdk_keymap_translate_keyboard_state( Gdk::Display::get_default()->get_keymap(),
                                          event->hardware_keycode, (GdkModifierType)event->state,
-                                         0, &key, 0, 0, 0 );
+                                         0, &key, nullptr, nullptr, nullptr );
 
     switch ( key ) {
 
diff --git a/src/widgets/ink-comboboxentry-action.h b/src/widgets/ink-comboboxentry-action.h
index 04b66e8fe..9faf44268 100644
--- a/src/widgets/ink-comboboxentry-action.h
+++ b/src/widgets/ink-comboboxentry-action.h
@@ -79,9 +79,9 @@ Ink_ComboBoxEntry_Action *ink_comboboxentry_action_new ( const gchar  *name,
 							 GtkTreeModel *model,
 							 gint          entry_width = -1,
 							 gint          extra_width = -1,
-							 gpointer cell_data_func = NULL,
-							 gpointer separator_func = NULL,
-							 GtkWidget* focusWidget = NULL);
+							 gpointer cell_data_func = nullptr,
+							 gpointer separator_func = nullptr,
+							 GtkWidget* focusWidget = nullptr);
 
 GtkTreeModel     *ink_comboboxentry_action_get_model( Ink_ComboBoxEntry_Action* action );
 GtkComboBox      *ink_comboboxentry_action_get_comboboxentry( Ink_ComboBoxEntry_Action* action );
diff --git a/src/widgets/ink-radio-action.cpp b/src/widgets/ink-radio-action.cpp
index e2bf828ce..611e0c624 100644
--- a/src/widgets/ink-radio-action.cpp
+++ b/src/widgets/ink-radio-action.cpp
@@ -61,7 +61,7 @@ static void ink_radio_action_class_init( InkRadioActionClass* klass )
 static void ink_radio_action_init( InkRadioAction* action )
 {
     action->private_data = INK_RADIO_ACTION_GET_PRIVATE( action );
-    action->private_data->iconId = 0;
+    action->private_data->iconId = nullptr;
     action->private_data->iconSize = GTK_ICON_SIZE_SMALL_TOOLBAR;
 }
 
diff --git a/src/widgets/ink-toggle-action.cpp b/src/widgets/ink-toggle-action.cpp
index 200d0d558..467f0f24c 100644
--- a/src/widgets/ink-toggle-action.cpp
+++ b/src/widgets/ink-toggle-action.cpp
@@ -63,7 +63,7 @@ static void ink_toggle_action_class_init( InkToggleActionClass* klass )
 static void ink_toggle_action_init( InkToggleAction* action )
 {
     action->private_data = INK_TOGGLE_ACTION_GET_PRIVATE( action );
-    action->private_data->iconId = 0;
+    action->private_data->iconId = nullptr;
     action->private_data->iconSize = GTK_ICON_SIZE_SMALL_TOOLBAR;
 }
 
@@ -169,11 +169,11 @@ static GtkWidget* ink_toggle_action_create_tool_item( GtkAction* action )
 	    gtk_widget_set_vexpand(child, FALSE);
 	    gtk_tool_button_set_icon_widget(button, child);
         } else {
-            gchar *label = 0;
+            gchar *label = nullptr;
             g_object_get( G_OBJECT(action), "short_label", &label, NULL );
             gtk_tool_button_set_label( button, label );
             g_free( label );
-            label = 0;
+            label = nullptr;
         }
     } else {
         // For now trigger a warning but don't do anything else
diff --git a/src/widgets/ink-tool-menu-action.cpp b/src/widgets/ink-tool-menu-action.cpp
index 44c09147b..d1d9501b4 100644
--- a/src/widgets/ink-tool-menu-action.cpp
+++ b/src/widgets/ink-tool-menu-action.cpp
@@ -23,7 +23,7 @@ ink_tool_menu_action_new (const gchar *name,
                           const gchar *inkId,
                           GtkIconSize  size )
 {
-    g_return_val_if_fail (name != NULL, NULL);
+    g_return_val_if_fail (name != nullptr, NULL);
 
     GObject* obj = (GObject*)g_object_new( INK_TOOL_MENU_ACTION_TYPE,
                                            "name", name,
diff --git a/src/widgets/paint-selector.cpp b/src/widgets/paint-selector.cpp
index 991d81d4a..3fcd40bdf 100644
--- a/src/widgets/paint-selector.cpp
+++ b/src/widgets/paint-selector.cpp
@@ -127,7 +127,7 @@ static bool isPaintModeGradient(SPPaintSelector::Mode mode)
 
 static SPGradientSelector *getGradientFromData(SPPaintSelector const *psel)
 {
-    SPGradientSelector *grad = 0;
+    SPGradientSelector *grad = nullptr;
     if (psel->mode == SPPaintSelector::MODE_SWATCH) {
         SwatchSelector *swatchsel = static_cast<SwatchSelector*>(g_object_get_data(G_OBJECT(psel->selector), "swatch-selector"));
         if (swatchsel) {
@@ -150,42 +150,42 @@ sp_paint_selector_class_init(SPPaintSelectorClass *klass)
                                                 G_TYPE_FROM_CLASS(object_class),
                                                 (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                                 G_STRUCT_OFFSET(SPPaintSelectorClass, mode_changed),
-                                                NULL, NULL,
+                                                nullptr, nullptr,
                                                 g_cclosure_marshal_VOID__UINT,
                                                 G_TYPE_NONE, 1, G_TYPE_UINT);
     psel_signals[GRABBED] =  g_signal_new("grabbed",
                                             G_TYPE_FROM_CLASS(object_class),
                                             (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                             G_STRUCT_OFFSET(SPPaintSelectorClass, grabbed),
-                                            NULL, NULL,
+                                            nullptr, nullptr,
                                             g_cclosure_marshal_VOID__VOID,
                                             G_TYPE_NONE, 0);
     psel_signals[DRAGGED] =  g_signal_new("dragged",
                                             G_TYPE_FROM_CLASS(object_class),
                                             (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                             G_STRUCT_OFFSET(SPPaintSelectorClass, dragged),
-                                            NULL, NULL,
+                                            nullptr, nullptr,
                                             g_cclosure_marshal_VOID__VOID,
                                             G_TYPE_NONE, 0);
     psel_signals[RELEASED] = g_signal_new("released",
                                             G_TYPE_FROM_CLASS(object_class),
                                             (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                             G_STRUCT_OFFSET(SPPaintSelectorClass, released),
-                                            NULL, NULL,
+                                            nullptr, nullptr,
                                             g_cclosure_marshal_VOID__VOID,
                                             G_TYPE_NONE, 0);
     psel_signals[CHANGED] =  g_signal_new("changed",
                                             G_TYPE_FROM_CLASS(object_class),
                                             (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                             G_STRUCT_OFFSET(SPPaintSelectorClass, changed),
-                                            NULL, NULL,
+                                            nullptr, nullptr,
                                             g_cclosure_marshal_VOID__VOID,
                                             G_TYPE_NONE, 0);
     psel_signals[FILLRULE_CHANGED] = g_signal_new("fillrule_changed",
                                                     G_TYPE_FROM_CLASS(object_class),
                                                     (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                                     G_STRUCT_OFFSET(SPPaintSelectorClass, fillrule_changed),
-                                                    NULL, NULL,
+                                                    nullptr, nullptr,
                                                     g_cclosure_marshal_VOID__UINT,
                                                     G_TYPE_NONE, 1, G_TYPE_UINT);
 
@@ -237,7 +237,7 @@ sp_paint_selector_init(SPPaintSelector *psel)
         gtk_box_pack_end(GTK_BOX(psel->style), psel->fillrulebox, FALSE, FALSE, 0);
 
         GtkWidget *w;
-        psel->evenodd = gtk_radio_button_new(NULL);
+        psel->evenodd = gtk_radio_button_new(nullptr);
         gtk_button_set_relief(GTK_BUTTON(psel->evenodd), GTK_RELIEF_NONE);
         gtk_toggle_button_set_mode(GTK_TOGGLE_BUTTON(psel->evenodd), FALSE);
         // TRANSLATORS: for info, see http://www.w3.org/TR/2000/CR-SVG-20000802/painting.html#FillRuleProperty
@@ -290,16 +290,16 @@ static void sp_paint_selector_dispose(GObject *object)
     SPPaintSelector *psel = SP_PAINT_SELECTOR(object);
 
     // clean up our long-living pattern menu
-    g_object_set_data(G_OBJECT(psel),"patternmenu",NULL);
+    g_object_set_data(G_OBJECT(psel),"patternmenu",nullptr);
 
 #ifdef WITH_MESH
     // clean up our long-living mesh menu
-    g_object_set_data(G_OBJECT(psel),"meshmenu",NULL);
+    g_object_set_data(G_OBJECT(psel),"meshmenu",nullptr);
 #endif
 
     if (psel->selected_color) {
         delete psel->selected_color;
-        psel->selected_color = NULL;
+        psel->selected_color = nullptr;
     }
 
     if ((G_OBJECT_CLASS(sp_paint_selector_parent_class))->dispose)
@@ -358,7 +358,7 @@ sp_paint_selector_show_fillrule(SPPaintSelector *psel, bool is_fill)
             gtk_widget_show_all(psel->fillrulebox);
         } else {
             gtk_widget_destroy(psel->fillrulebox);
-            psel->fillrulebox = NULL;
+            psel->fillrulebox = nullptr;
         }
     }
 }
@@ -366,7 +366,7 @@ sp_paint_selector_show_fillrule(SPPaintSelector *psel, bool is_fill)
 
 SPPaintSelector *sp_paint_selector_new(FillOrStroke kind)
 {
-    SPPaintSelector *psel = static_cast<SPPaintSelector*>(g_object_new(SP_TYPE_PAINT_SELECTOR, NULL));
+    SPPaintSelector *psel = static_cast<SPPaintSelector*>(g_object_new(SP_TYPE_PAINT_SELECTOR, nullptr));
 
     psel->setMode(SPPaintSelector::MODE_MULTIPLE);
 
@@ -472,7 +472,7 @@ void SPPaintSelector::setSwatch(SPGradient *vector )
 
     SwatchSelector *swatchsel = static_cast<SwatchSelector*>(g_object_get_data(G_OBJECT(selector), "swatch-selector"));
     if (swatchsel) {
-        swatchsel->setVector( (vector) ? vector->document : 0, vector );
+        swatchsel->setVector( (vector) ? vector->document : nullptr, vector );
     }
 }
 
@@ -486,7 +486,7 @@ void SPPaintSelector::setGradientLinear(SPGradient *vector)
     SPGradientSelector *gsel = getGradientFromData(this);
 
     gsel->setMode(SPGradientSelector::MODE_LINEAR);
-    gsel->setVector((vector) ? vector->document : 0, vector);
+    gsel->setVector((vector) ? vector->document : nullptr, vector);
 }
 
 void SPPaintSelector::setGradientRadial(SPGradient *vector)
@@ -500,7 +500,7 @@ void SPPaintSelector::setGradientRadial(SPGradient *vector)
 
     gsel->setMode(SPGradientSelector::MODE_RADIAL);
 
-    gsel->setVector((vector) ? vector->document : 0, vector);
+    gsel->setVector((vector) ? vector->document : nullptr, vector);
 }
 
 #ifdef WITH_MESH
@@ -550,7 +550,7 @@ void SPPaintSelector::getColorAlpha(SPColor &color, gfloat &alpha) const
 
 SPGradient *SPPaintSelector::getGradientVector()
 {
-    SPGradient* vect = 0;
+    SPGradient* vect = nullptr;
 
     if (isPaintModeGradient(mode)) {
         SPGradientSelector *gsel = getGradientFromData(this);
@@ -574,7 +574,7 @@ void SPPaintSelector::pushAttrsToGradient( SPGradient *gr ) const
 static void
 sp_paint_selector_clear_frame(SPPaintSelector *psel)
 {
-    g_return_if_fail( psel != NULL);
+    g_return_if_fail( psel != nullptr);
 
     if (psel->selector) {
 
@@ -582,14 +582,14 @@ sp_paint_selector_clear_frame(SPPaintSelector *psel)
         //The widget is hidden first so it can recognize that it should not process signals from notebook child
         gtk_widget_set_visible(psel->selector, false);
         gtk_widget_destroy(psel->selector);
-        psel->selector = NULL;
+        psel->selector = nullptr;
     }
 }
 
 static void
 sp_paint_selector_set_mode_empty(SPPaintSelector *psel)
 {
-    sp_paint_selector_set_style_buttons(psel, NULL);
+    sp_paint_selector_set_style_buttons(psel, nullptr);
     gtk_widget_set_sensitive(psel->style, FALSE);
 
     sp_paint_selector_clear_frame(psel);
@@ -600,7 +600,7 @@ sp_paint_selector_set_mode_empty(SPPaintSelector *psel)
 static void
 sp_paint_selector_set_mode_multiple(SPPaintSelector *psel)
 {
-    sp_paint_selector_set_style_buttons(psel, NULL);
+    sp_paint_selector_set_style_buttons(psel, nullptr);
     gtk_widget_set_sensitive(psel->style, TRUE);
 
     sp_paint_selector_clear_frame(psel);
@@ -803,7 +803,7 @@ static std::vector<SPMeshGradient *>
 ink_mesh_list_get (SPDocument *source)
 {
     std::vector<SPMeshGradient *> pl;
-    if (source == NULL)
+    if (source == nullptr)
         return pl;
 
 
@@ -861,7 +861,7 @@ static void sp_mesh_list_from_doc(GtkWidget *combo, SPDocument * /*current_doc*/
 static void
 ink_mesh_menu_populate_menu(GtkWidget *combo, SPDocument *doc)
 {
-    static SPDocument *meshes_doc = NULL;
+    static SPDocument *meshes_doc = nullptr;
 
     // If we ever add a list of canned mesh gradients, uncomment following:
 
@@ -875,7 +875,7 @@ ink_mesh_menu_populate_menu(GtkWidget *combo, SPDocument *doc)
     // }
 
     // suck in from current doc
-    sp_mesh_list_from_doc ( combo, NULL, doc, meshes_doc );
+    sp_mesh_list_from_doc ( combo, nullptr, doc, meshes_doc );
 
     // add separator
     // {
@@ -939,7 +939,7 @@ void SPPaintSelector::updateMeshList( SPMeshGradient *mesh )
     }
 
     GtkWidget *combo = GTK_WIDGET(g_object_get_data(G_OBJECT(this), "meshmenu"));
-    g_assert( combo != NULL );
+    g_assert( combo != nullptr );
 
     /* Clear existing menu if any */
     GtkTreeModel *store = gtk_combo_box_get_model(GTK_COMBO_BOX(combo));
@@ -956,7 +956,7 @@ void SPPaintSelector::updateMeshList( SPMeshGradient *mesh )
 
         // Find this mesh and set it active in the combo_box
         GtkTreeIter iter ;
-        gchar *meshid = NULL;
+        gchar *meshid = nullptr;
         bool valid = gtk_tree_model_get_iter_first (store, &iter);
         if (!valid) {
             return;
@@ -982,7 +982,7 @@ static void sp_paint_selector_set_mode_mesh(SPPaintSelector *psel, SPPaintSelect
     }
     gtk_widget_set_sensitive(psel->style, TRUE);
 
-    GtkWidget *tbl = NULL;
+    GtkWidget *tbl = nullptr;
 
     if (psel->mode == SPPaintSelector::MODE_GRADIENT_MESH) {
         /* Already have mesh menu */
@@ -1005,7 +1005,7 @@ static void sp_paint_selector_set_mode_mesh(SPPaintSelector *psel, SPPaintSelect
              */
             GtkListStore *store = gtk_list_store_new (COMBO_N_COLS, G_TYPE_STRING, G_TYPE_BOOLEAN, G_TYPE_STRING, G_TYPE_BOOLEAN);
             GtkWidget *combo = gtk_combo_box_new_with_model (GTK_TREE_MODEL (store));
-            gtk_combo_box_set_row_separator_func(GTK_COMBO_BOX(combo), SPPaintSelector::isSeparator, NULL, NULL);
+            gtk_combo_box_set_row_separator_func(GTK_COMBO_BOX(combo), SPPaintSelector::isSeparator, nullptr, nullptr);
 
             GtkCellRenderer *renderer = gtk_cell_renderer_text_new ();
             gtk_cell_renderer_set_padding (renderer, 2, 0);
@@ -1027,7 +1027,7 @@ static void sp_paint_selector_set_mode_mesh(SPPaintSelector *psel, SPPaintSelect
         {
             auto hb = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0);
             gtk_box_set_homogeneous(GTK_BOX(hb), FALSE);
-            auto l = gtk_label_new(NULL);
+            auto l = gtk_label_new(nullptr);
             gtk_label_set_markup(GTK_LABEL(l), _("Use the <b>Mesh tool</b> to modify the mesh."));
             gtk_label_set_line_wrap(GTK_LABEL(l), true);
             gtk_widget_set_size_request(l, 180, -1);
@@ -1055,8 +1055,8 @@ SPMeshGradient *SPPaintSelector::getMeshGradient()
     GtkWidget *combo = GTK_WIDGET(g_object_get_data(G_OBJECT(this), "meshmenu"));
 
     /* no mesh menu if we were just selected */
-    if ( combo == NULL ) {
-        return NULL;
+    if ( combo == nullptr ) {
+        return nullptr;
     }
     GtkTreeModel *store = gtk_combo_box_get_model(GTK_COMBO_BOX(combo));
 
@@ -1064,19 +1064,19 @@ SPMeshGradient *SPPaintSelector::getMeshGradient()
     GtkTreeIter  iter;
     if (!gtk_combo_box_get_active_iter (GTK_COMBO_BOX(combo), &iter) ||
             !gtk_list_store_iter_is_valid(GTK_LIST_STORE(store), &iter)) {
-        return NULL;
+        return nullptr;
     }
 
-    gchar *meshid = NULL;
+    gchar *meshid = nullptr;
     gboolean stockid = FALSE;
-    gchar *label = NULL;
+    gchar *label = nullptr;
     gtk_tree_model_get (store, &iter, COMBO_COL_LABEL, &label, COMBO_COL_STOCK, &stockid, COMBO_COL_MESH, &meshid,  -1);
     // std::cout << "  .. meshid: " << (meshid?meshid:"null") << "   label: " << (label?label:"null") << std::endl;
-    if (meshid == NULL) {
-        return NULL;
+    if (meshid == nullptr) {
+        return nullptr;
     }
 
-    SPMeshGradient *mesh = 0;
+    SPMeshGradient *mesh = nullptr;
     if (strcmp(meshid, "none")){
 
         gchar *mesh_name;
@@ -1137,7 +1137,7 @@ static std::vector<SPPattern*>
 ink_pattern_list_get (SPDocument *source)
 {
     std::vector<SPPattern *> pl;
-    if (source == NULL)
+    if (source == nullptr)
         return pl;
 
     std::vector<SPObject *> patterns = source->getResourceList("pattern");
@@ -1199,10 +1199,10 @@ static void sp_pattern_list_from_doc(GtkWidget *combo, SPDocument * /*current_do
 static void
 ink_pattern_menu_populate_menu(GtkWidget *combo, SPDocument *doc)
 {
-    static SPDocument *patterns_doc = NULL;
+    static SPDocument *patterns_doc = nullptr;
 
     // find and load patterns.svg
-    if (patterns_doc == NULL) {
+    if (patterns_doc == nullptr) {
         char *patterns_source = g_build_filename(INKSCAPE_PATTERNSDIR, "patterns.svg", NULL);
         if (Inkscape::IO::file_test(patterns_source, G_FILE_TEST_IS_REGULAR)) {
             patterns_doc = SPDocument::createNewDoc(patterns_source, FALSE);
@@ -1211,7 +1211,7 @@ ink_pattern_menu_populate_menu(GtkWidget *combo, SPDocument *doc)
     }
 
     // suck in from current doc
-    sp_pattern_list_from_doc ( combo, NULL, doc, patterns_doc );
+    sp_pattern_list_from_doc ( combo, nullptr, doc, patterns_doc );
 
     // add separator
     {
@@ -1225,7 +1225,7 @@ ink_pattern_menu_populate_menu(GtkWidget *combo, SPDocument *doc)
     // suck in from patterns.svg
     if (patterns_doc) {
         doc->ensureUpToDate();
-        sp_pattern_list_from_doc ( combo, doc, patterns_doc, NULL );
+        sp_pattern_list_from_doc ( combo, doc, patterns_doc, nullptr );
     }
 
 }
@@ -1274,7 +1274,7 @@ void SPPaintSelector::updatePatternList( SPPattern *pattern )
         return;
     }
     GtkWidget *combo = GTK_WIDGET(g_object_get_data(G_OBJECT(this), "patternmenu"));
-    g_assert( combo != NULL );
+    g_assert( combo != nullptr );
 
     /* Clear existing menu if any */
     GtkTreeModel *store = gtk_combo_box_get_model(GTK_COMBO_BOX(combo));
@@ -1291,7 +1291,7 @@ void SPPaintSelector::updatePatternList( SPPattern *pattern )
 
         // Find this pattern and set it active in the combo_box
         GtkTreeIter iter ;
-        gchar *patid = NULL;
+        gchar *patid = nullptr;
         bool valid = gtk_tree_model_get_iter_first (store, &iter);
         if (!valid) {
             return;
@@ -1318,7 +1318,7 @@ static void sp_paint_selector_set_mode_pattern(SPPaintSelector *psel, SPPaintSel
 
     gtk_widget_set_sensitive(psel->style, TRUE);
 
-    GtkWidget *tbl = NULL;
+    GtkWidget *tbl = nullptr;
 
     if (psel->mode == SPPaintSelector::MODE_PATTERN) {
         /* Already have pattern menu */
@@ -1341,7 +1341,7 @@ static void sp_paint_selector_set_mode_pattern(SPPaintSelector *psel, SPPaintSel
              */
             GtkListStore *store = gtk_list_store_new (COMBO_N_COLS, G_TYPE_STRING, G_TYPE_BOOLEAN, G_TYPE_STRING, G_TYPE_BOOLEAN);
             GtkWidget *combo = gtk_combo_box_new_with_model (GTK_TREE_MODEL (store));
-            gtk_combo_box_set_row_separator_func(GTK_COMBO_BOX(combo), SPPaintSelector::isSeparator, NULL, NULL);
+            gtk_combo_box_set_row_separator_func(GTK_COMBO_BOX(combo), SPPaintSelector::isSeparator, nullptr, nullptr);
 
             GtkCellRenderer *renderer = gtk_cell_renderer_text_new ();
             gtk_cell_renderer_set_padding (renderer, 2, 0);
@@ -1363,7 +1363,7 @@ static void sp_paint_selector_set_mode_pattern(SPPaintSelector *psel, SPPaintSel
         {
             auto hb = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0);
             gtk_box_set_homogeneous(GTK_BOX(hb), FALSE);
-            auto l = gtk_label_new(NULL);
+            auto l = gtk_label_new(nullptr);
             gtk_label_set_markup(GTK_LABEL(l), _("Use the <b>Node tool</b> to adjust position, scale, and rotation of the pattern on canvas. Use <b>Object &gt; Pattern &gt; Objects to Pattern</b> to create a new pattern from selection."));
             gtk_label_set_line_wrap(GTK_LABEL(l), true);
             gtk_widget_set_size_request(l, 180, -1);
@@ -1393,14 +1393,14 @@ gboolean SPPaintSelector::isSeparator (GtkTreeModel *model, GtkTreeIter *iter, g
 
 SPPattern *SPPaintSelector::getPattern()
 {
-    SPPattern *pat = 0;
+    SPPattern *pat = nullptr;
     g_return_val_if_fail((mode == MODE_PATTERN) , NULL);
 
     GtkWidget *combo = GTK_WIDGET(g_object_get_data(G_OBJECT(this), "patternmenu"));
 
     /* no pattern menu if we were just selected */
-    if ( combo == NULL ) {
-        return NULL;
+    if ( combo == nullptr ) {
+        return nullptr;
     }
 
     GtkTreeModel *store = gtk_combo_box_get_model(GTK_COMBO_BOX(combo));
@@ -1409,15 +1409,15 @@ SPPattern *SPPaintSelector::getPattern()
     GtkTreeIter  iter;
     if (!gtk_combo_box_get_active_iter (GTK_COMBO_BOX(combo), &iter) ||
             !gtk_list_store_iter_is_valid(GTK_LIST_STORE(store), &iter)) {
-        return NULL;
+        return nullptr;
     }
 
-    gchar *patid = NULL;
+    gchar *patid = nullptr;
     gboolean stockid = FALSE;
-    gchar *label = NULL;
+    gchar *label = nullptr;
     gtk_tree_model_get (store, &iter, COMBO_COL_LABEL, &label, COMBO_COL_STOCK, &stockid, COMBO_COL_PATTERN, &patid,  -1);
-    if (patid == NULL) {
-        return NULL;
+    if (patid == nullptr) {
+        return nullptr;
     }
 
     if (strcmp(patid, "none")){
@@ -1439,7 +1439,7 @@ SPPattern *SPPaintSelector::getPattern()
     }
 
     if (pat && !SP_IS_PATTERN(pat)) {
-        pat = 0;
+        pat = nullptr;
     }
 
     return pat;
diff --git a/src/widgets/sp-attribute-widget.cpp b/src/widgets/sp-attribute-widget.cpp
index d89e6296c..043eb93cc 100644
--- a/src/widgets/sp-attribute-widget.cpp
+++ b/src/widgets/sp-attribute-widget.cpp
@@ -65,9 +65,9 @@ static void sp_attribute_table_object_release (SPObject */*object*/, SPAttribute
 
 
 SPAttributeTable::SPAttributeTable () : 
-    _object(NULL),
+    _object(nullptr),
     blocked(false),
-    table(NULL),
+    table(nullptr),
     _attributes(),
     _entries(),
     modified_connection(),
@@ -76,9 +76,9 @@ SPAttributeTable::SPAttributeTable () :
 }
 
 SPAttributeTable::SPAttributeTable (SPObject *object, std::vector<Glib::ustring> &labels, std::vector<Glib::ustring> &attributes, GtkWidget* parent) : 
-    _object(NULL),
+    _object(nullptr),
     blocked(false),
-    table(NULL),
+    table(nullptr),
     _attributes(),
     _entries(),
     modified_connection(),
@@ -101,7 +101,7 @@ void SPAttributeTable::clear(void)
         {
             Gtk::Widget *w = ch[i];
             ch.pop_back();
-            if (w != NULL)
+            if (w != nullptr)
             {
                 try
                 {
@@ -118,14 +118,14 @@ void SPAttributeTable::clear(void)
         _entries.clear();
         
         delete table;
-        table = NULL;
+        table = nullptr;
     }
 
     if (_object)
     {
         modified_connection.disconnect();
         release_connection.disconnect();
-        _object = NULL;
+        _object = nullptr;
     }
 }
 
@@ -151,7 +151,7 @@ void SPAttributeTable::set_object(SPObject *object,
         // Create table
         table = new Gtk::Grid();
 
-        if (!(parent == NULL))
+        if (!(parent == nullptr))
             gtk_container_add(GTK_CONTAINER(parent), (GtkWidget*)table->gobj());
         
         // Fill rows
@@ -208,7 +208,7 @@ void SPAttributeTable::change_object(SPObject *object)
     {
         modified_connection.disconnect();
         release_connection.disconnect();
-        _object = NULL;
+        _object = nullptr;
     }
 
     _object = object;
@@ -295,7 +295,7 @@ static void sp_attribute_table_object_release (SPObject */*object*/, SPAttribute
 {
     std::vector<Glib::ustring> labels;
     std::vector<Glib::ustring> attributes;
-    spat->set_object (NULL, labels, attributes, NULL);
+    spat->set_object (nullptr, labels, attributes, nullptr);
 }
 
 /*
diff --git a/src/widgets/sp-color-selector.cpp b/src/widgets/sp-color-selector.cpp
index 8a30b276b..6ee827fb8 100644
--- a/src/widgets/sp-color-selector.cpp
+++ b/src/widgets/sp-color-selector.cpp
@@ -36,7 +36,7 @@ G_DEFINE_TYPE(SPColorSelector, sp_color_selector, GTK_TYPE_BOX);
 
 void sp_color_selector_class_init( SPColorSelectorClass *klass )
 {
-    static const gchar* nameset[] = {N_("Unnamed"), 0};
+    static const gchar* nameset[] = {N_("Unnamed"), nullptr};
     GObjectClass *object_class = G_OBJECT_CLASS(klass);
     GtkWidgetClass *widget_class;
     widget_class = GTK_WIDGET_CLASS(klass);
@@ -45,28 +45,28 @@ void sp_color_selector_class_init( SPColorSelectorClass *klass )
                                             G_TYPE_FROM_CLASS(object_class),
                                             (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                             G_STRUCT_OFFSET(SPColorSelectorClass, grabbed),
-					    NULL, NULL,
+					    nullptr, nullptr,
 					    g_cclosure_marshal_VOID__VOID,
                                             G_TYPE_NONE, 0 );
     csel_signals[DRAGGED] = g_signal_new( "dragged",
                                             G_TYPE_FROM_CLASS(object_class),
                                             (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                             G_STRUCT_OFFSET(SPColorSelectorClass, dragged),
-					    NULL, NULL,
+					    nullptr, nullptr,
 					    g_cclosure_marshal_VOID__VOID,
                                             G_TYPE_NONE, 0 );
     csel_signals[RELEASED] = g_signal_new( "released",
                                              G_TYPE_FROM_CLASS(object_class),
                                              (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                              G_STRUCT_OFFSET(SPColorSelectorClass, released),
-					     NULL, NULL,
+					     nullptr, nullptr,
 					     g_cclosure_marshal_VOID__VOID,
                                              G_TYPE_NONE, 0 );
     csel_signals[CHANGED] = g_signal_new( "changed",
                                             G_TYPE_FROM_CLASS(object_class),
                                             (GSignalFlags)(G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE),
                                             G_STRUCT_OFFSET(SPColorSelectorClass, changed),
-					    NULL, NULL,
+					    nullptr, nullptr,
 					    g_cclosure_marshal_VOID__VOID,
                                             G_TYPE_NONE, 0 );
 
@@ -97,7 +97,7 @@ void sp_color_selector_dispose(GObject *object)
     if ( csel->base )
         {
             delete csel->base;
-            csel->base = 0;
+            csel->base = nullptr;
         }
 
     if ((G_OBJECT_CLASS(sp_color_selector_parent_class))->dispose ) {
@@ -119,7 +119,7 @@ GtkWidget *sp_color_selector_new( GType selector_type )
 {
     g_return_val_if_fail( g_type_is_a( selector_type, SP_TYPE_COLOR_SELECTOR ), NULL );
 
-    SPColorSelector *csel = SP_COLOR_SELECTOR( g_object_new( selector_type, NULL ) );
+    SPColorSelector *csel = SP_COLOR_SELECTOR( g_object_new( selector_type, nullptr ) );
 
     return GTK_WIDGET( csel );
 }
@@ -183,7 +183,7 @@ void ColorSelector::setColorAlpha( const SPColor& color, gfloat alpha, bool emit
 #ifdef DUMP_CHANGE_INFO
     g_message("ColorSelector::setColorAlpha( this=%p, %f, %f, %f, %s,   %f,   %s) in %s", this, color.v.c[0], color.v.c[1], color.v.c[2], (color.icc?color.icc->colorProfile.c_str():"<null>"), alpha, (emit?"YES":"no"), FOO_NAME(_csel));
 #endif
-    g_return_if_fail( _csel != NULL );
+    g_return_if_fail( _csel != nullptr );
     g_return_if_fail( ( 0.0 <= alpha ) && ( alpha <= 1.0 ) );
 
 #ifdef DUMP_CHANGE_INFO
diff --git a/src/widgets/sp-widget.cpp b/src/widgets/sp-widget.cpp
index 707e62c12..fab39544b 100644
--- a/src/widgets/sp-widget.cpp
+++ b/src/widgets/sp-widget.cpp
@@ -81,7 +81,7 @@ sp_widget_class_init(SPWidgetClass *klass)
                                               G_TYPE_FROM_CLASS(object_class),
                                               G_SIGNAL_RUN_FIRST,
                                               G_STRUCT_OFFSET(SPWidgetClass, construct),
-                                              NULL, NULL,
+                                              nullptr, nullptr,
                                               g_cclosure_marshal_VOID__VOID,
                                               G_TYPE_NONE, 0);
 
@@ -89,7 +89,7 @@ sp_widget_class_init(SPWidgetClass *klass)
                                               G_TYPE_FROM_CLASS(object_class),
                                               G_SIGNAL_RUN_FIRST,
                                               G_STRUCT_OFFSET(SPWidgetClass, change_selection),
-                                              NULL, NULL,
+                                              nullptr, nullptr,
                                               g_cclosure_marshal_VOID__POINTER,
                                               G_TYPE_NONE, 1,
                                               G_TYPE_POINTER);
@@ -98,7 +98,7 @@ sp_widget_class_init(SPWidgetClass *klass)
                                               G_TYPE_FROM_CLASS(object_class),
                                               G_SIGNAL_RUN_FIRST,
                                               G_STRUCT_OFFSET(SPWidgetClass, modify_selection),
-                                              NULL, NULL,
+                                              nullptr, nullptr,
                                               sp_marshal_VOID__POINTER_UINT,
                                               G_TYPE_NONE, 2,
                                               G_TYPE_POINTER, G_TYPE_UINT);
@@ -107,7 +107,7 @@ sp_widget_class_init(SPWidgetClass *klass)
                                               G_TYPE_FROM_CLASS(object_class),
                                               G_SIGNAL_RUN_FIRST,
                                               G_STRUCT_OFFSET(SPWidgetClass, set_selection),
-                                              NULL, NULL,
+                                              nullptr, nullptr,
                                               g_cclosure_marshal_VOID__POINTER,
                                               G_TYPE_NONE, 1,
                                               G_TYPE_POINTER);
@@ -148,7 +148,7 @@ void SPWidgetImpl::dispose(GObject *object)
     }            
 
     delete spw->_impl;
-    spw->_impl = 0;
+    spw->_impl = nullptr;
 
     if (G_OBJECT_CLASS(sp_widget_parent_class)->dispose) {
         G_OBJECT_CLASS(sp_widget_parent_class)->dispose(object);
@@ -300,11 +300,11 @@ void SPWidgetImpl::setSelection(Selection *selection)
 
 GtkWidget *sp_widget_new_global()
 {
-    SPWidget *spw = reinterpret_cast<SPWidget*>(g_object_new(SP_TYPE_WIDGET, NULL));
+    SPWidget *spw = reinterpret_cast<SPWidget*>(g_object_new(SP_TYPE_WIDGET, nullptr));
 
     if (!SPWidgetImpl::constructGlobal(spw)) {
         g_object_unref(spw);
-        spw = 0;
+        spw = nullptr;
     }
 
     return reinterpret_cast<GtkWidget *>(spw);
diff --git a/src/widgets/sp-xmlview-attr-list.cpp b/src/widgets/sp-xmlview-attr-list.cpp
index e99605b97..720856ba5 100644
--- a/src/widgets/sp-xmlview-attr-list.cpp
+++ b/src/widgets/sp-xmlview-attr-list.cpp
@@ -25,16 +25,16 @@ static void sp_xmlview_attr_list_destroy(GtkWidget * object);
 static void event_attr_changed (Inkscape::XML::Node * repr, const gchar * name, const gchar * old_value, const gchar * new_value, bool is_interactive, gpointer data);
 
 static Inkscape::XML::NodeEventVector repr_events = {
-	NULL, /* child_added */
-	NULL, /* child_removed */
+	nullptr, /* child_added */
+	nullptr, /* child_removed */
 	event_attr_changed,
-	NULL, /* content_changed */
-	NULL  /* order_changed */
+	nullptr, /* content_changed */
+	nullptr  /* order_changed */
 };
 
 GtkWidget *sp_xmlview_attr_list_new (Inkscape::XML::Node * repr)
 {
-    SPXMLViewAttrList * attr_list = SP_XMLVIEW_ATTR_LIST(g_object_new(SP_TYPE_XMLVIEW_ATTR_LIST, NULL));
+    SPXMLViewAttrList * attr_list = SP_XMLVIEW_ATTR_LIST(g_object_new(SP_TYPE_XMLVIEW_ATTR_LIST, nullptr));
 
     attr_list->store = gtk_list_store_new (ATTR_N_COLS, G_TYPE_STRING, G_TYPE_UINT, G_TYPE_STRING );
     gtk_tree_view_set_model (GTK_TREE_VIEW(attr_list), GTK_TREE_MODEL(attr_list->store));
@@ -90,7 +90,7 @@ void sp_xmlview_attr_list_class_init (SPXMLViewAttrListClass * klass)
                       G_TYPE_FROM_CLASS(klass),
                       G_SIGNAL_RUN_FIRST,
                       G_STRUCT_OFFSET (SPXMLViewAttrListClass, row_changed),
-                      NULL, NULL,
+                      nullptr, nullptr,
                       g_cclosure_marshal_VOID__STRING,
                       G_TYPE_NONE, 1,
                       G_TYPE_STRING);
@@ -99,8 +99,8 @@ void sp_xmlview_attr_list_class_init (SPXMLViewAttrListClass * klass)
 void
 sp_xmlview_attr_list_init (SPXMLViewAttrList * list)
 {
-    list->store = NULL;
-	list->repr = NULL;
+    list->store = nullptr;
+	list->repr = nullptr;
 }
 
 void sp_xmlview_attr_list_destroy(GtkWidget * object)
@@ -110,7 +110,7 @@ void sp_xmlview_attr_list_destroy(GtkWidget * object)
 	list = SP_XMLVIEW_ATTR_LIST (object);
 
 	g_object_unref(list->store);
-	sp_xmlview_attr_list_set_repr (list, NULL);
+	sp_xmlview_attr_list_set_repr (list, nullptr);
 
 	GTK_WIDGET_CLASS(sp_xmlview_attr_list_parent_class)->destroy (object);
 }
@@ -121,7 +121,7 @@ void sp_xmlview_attr_list_select_row_by_key(SPXMLViewAttrList * list, const gcha
     gboolean match = false;
     gboolean valid = gtk_tree_model_get_iter_first( GTK_TREE_MODEL(list->store), &iter );
     while ( valid ) {
-        gchar *n = 0;
+        gchar *n = nullptr;
         gtk_tree_model_get (GTK_TREE_MODEL(list->store), &iter, ATTR_COL_NAME, &n, -1);
         if (!strcmp(n, name)) {
             match = true;
@@ -157,7 +157,7 @@ event_attr_changed (Inkscape::XML::Node * /*repr*/,
     gboolean valid = gtk_tree_model_get_iter_first( GTK_TREE_MODEL(list->store), &iter );
     gboolean match = false;
     while ( valid ) {
-        gchar *n = 0;
+        gchar *n = nullptr;
         gtk_tree_model_get (GTK_TREE_MODEL(list->store), &iter, ATTR_COL_NAME, &n, -1);
         if (!strcmp(n, name)) {
             match = true;
@@ -177,7 +177,7 @@ event_attr_changed (Inkscape::XML::Node * /*repr*/,
 		} else {
 			gtk_list_store_remove  (list->store, &iter);
 		}
-	} else if (new_value != NULL) {
+	} else if (new_value != nullptr) {
 	    gtk_list_store_append (list->store, &iter);
         gtk_list_store_set (list->store, &iter, ATTR_COL_NAME, name, ATTR_COL_VALUE, new_value, ATTR_COL_ATTR, g_quark_from_string (name), -1);
 	}
diff --git a/src/widgets/sp-xmlview-content.cpp b/src/widgets/sp-xmlview-content.cpp
index 6e59ba3cd..6fc08c4ac 100644
--- a/src/widgets/sp-xmlview-content.cpp
+++ b/src/widgets/sp-xmlview-content.cpp
@@ -30,17 +30,17 @@ void sp_xmlview_content_changed (GtkTextBuffer *tb, SPXMLViewContent *text);
 static void event_content_changed (Inkscape::XML::Node * repr, const gchar * old_content, const gchar * new_content, gpointer data);
 
 static Inkscape::XML::NodeEventVector repr_events = {
-    NULL, /* child_added */
-    NULL, /* child_removed */
-    NULL, /* attr_changed */
+    nullptr, /* child_added */
+    nullptr, /* child_removed */
+    nullptr, /* attr_changed */
     event_content_changed,
-    NULL  /* order_changed */
+    nullptr  /* order_changed */
 };
 
 GtkWidget *sp_xmlview_content_new(Inkscape::XML::Node * repr)
 {
-    GtkTextBuffer *tb = gtk_text_buffer_new(NULL);
-    SPXMLViewContent *text = SP_XMLVIEW_CONTENT(g_object_new(SP_TYPE_XMLVIEW_CONTENT, NULL));
+    GtkTextBuffer *tb = gtk_text_buffer_new(nullptr);
+    SPXMLViewContent *text = SP_XMLVIEW_CONTENT(g_object_new(SP_TYPE_XMLVIEW_CONTENT, nullptr));
     gtk_text_view_set_buffer (GTK_TEXT_VIEW (text), tb);
     gtk_text_view_set_wrap_mode (GTK_TEXT_VIEW (text), GTK_WRAP_CHAR);
 
@@ -83,7 +83,7 @@ void sp_xmlview_content_class_init(SPXMLViewContentClass * klass)
 void
 sp_xmlview_content_init (SPXMLViewContent *text)
 {
-    text->repr = NULL;
+    text->repr = nullptr;
     text->blocked = FALSE;
 }
 
@@ -91,7 +91,7 @@ void sp_xmlview_content_destroy(GtkWidget * object)
 {
     SPXMLViewContent * text = SP_XMLVIEW_CONTENT (object);
 
-    sp_xmlview_content_set_repr (text, NULL);
+    sp_xmlview_content_set_repr (text, nullptr);
 
     GTK_WIDGET_CLASS (sp_xmlview_content_parent_class)->destroy (object);
 }
@@ -111,7 +111,7 @@ event_content_changed (Inkscape::XML::Node * /*repr*/, const gchar * /*old_conte
     } else {
         gtk_text_buffer_set_text (gtk_text_view_get_buffer (GTK_TEXT_VIEW (text)), "", 0);
     }
-    gtk_text_view_set_editable (GTK_TEXT_VIEW (text), new_content != NULL);
+    gtk_text_view_set_editable (GTK_TEXT_VIEW (text), new_content != nullptr);
 
     text->blocked = FALSE;
 }
diff --git a/src/widgets/sp-xmlview-tree.cpp b/src/widgets/sp-xmlview-tree.cpp
index 3f8cc6063..6b8db59ab 100644
--- a/src/widgets/sp-xmlview-tree.cpp
+++ b/src/widgets/sp-xmlview-tree.cpp
@@ -54,48 +54,48 @@ static const Inkscape::XML::NodeEventVector element_repr_events = {
         element_child_added,
         element_child_removed,
         element_attr_changed,
-        NULL, /* content_changed */
+        nullptr, /* content_changed */
         element_order_changed
 };
 
 static const Inkscape::XML::NodeEventVector text_repr_events = {
-        NULL, /* child_added */
-        NULL, /* child_removed */
-        NULL, /* attr_changed */
+        nullptr, /* child_added */
+        nullptr, /* child_removed */
+        nullptr, /* attr_changed */
         text_content_changed,
-        NULL  /* order_changed */
+        nullptr  /* order_changed */
 };
 
 static const Inkscape::XML::NodeEventVector comment_repr_events = {
-        NULL, /* child_added */
-        NULL, /* child_removed */
-        NULL, /* attr_changed */
+        nullptr, /* child_added */
+        nullptr, /* child_removed */
+        nullptr, /* attr_changed */
         comment_content_changed,
-        NULL  /* order_changed */
+        nullptr  /* order_changed */
 };
 
 static const Inkscape::XML::NodeEventVector pi_repr_events = {
-        NULL, /* child_added */
-        NULL, /* child_removed */
-        NULL, /* attr_changed */
+        nullptr, /* child_added */
+        nullptr, /* child_removed */
+        nullptr, /* attr_changed */
         pi_content_changed,
-        NULL  /* order_changed */
+        nullptr  /* order_changed */
 };
 
 GtkWidget *sp_xmlview_tree_new(Inkscape::XML::Node * repr, void * /*factory*/, void * /*data*/)
 {
-    SPXMLViewTree *tree = SP_XMLVIEW_TREE(g_object_new (SP_TYPE_XMLVIEW_TREE, NULL));
+    SPXMLViewTree *tree = SP_XMLVIEW_TREE(g_object_new (SP_TYPE_XMLVIEW_TREE, nullptr));
 
     tree->store = gtk_tree_store_new (STORE_N_COLS, G_TYPE_STRING, G_TYPE_POINTER, G_TYPE_POINTER);
 
     // Detach the model from the view until all the data is loaded
     g_object_ref(tree->store);
-    gtk_tree_view_set_model(GTK_TREE_VIEW(tree), NULL);
+    gtk_tree_view_set_model(GTK_TREE_VIEW(tree), nullptr);
 
     gtk_tree_view_set_headers_visible (GTK_TREE_VIEW(tree), FALSE);
     gtk_tree_view_set_reorderable (GTK_TREE_VIEW(tree), TRUE);
     gtk_tree_view_set_enable_search (GTK_TREE_VIEW(tree), TRUE);
-    gtk_tree_view_set_search_equal_func (GTK_TREE_VIEW(tree), search_equal_func, NULL, NULL);
+    gtk_tree_view_set_search_equal_func (GTK_TREE_VIEW(tree), search_equal_func, nullptr, nullptr);
 
     GtkCellRenderer *renderer = gtk_cell_renderer_text_new ();
     GtkTreeViewColumn *column = gtk_tree_view_column_new_with_attributes ("", renderer, "text", STORE_TEXT_COL, NULL);
@@ -124,7 +124,7 @@ void sp_xmlview_tree_class_init(SPXMLViewTreeClass * klass)
         G_TYPE_FROM_CLASS(klass),
         G_SIGNAL_RUN_FIRST,
         0,
-        NULL, NULL,
+        nullptr, nullptr,
         g_cclosure_marshal_VOID__UINT,
         G_TYPE_NONE, 1,
         G_TYPE_UINT);
@@ -133,7 +133,7 @@ void sp_xmlview_tree_class_init(SPXMLViewTreeClass * klass)
 void
 sp_xmlview_tree_init (SPXMLViewTree * tree)
 {
-	tree->repr = NULL;
+	tree->repr = nullptr;
 	tree->blocked = 0;
 	tree->dndactive = FALSE;
 }
@@ -142,7 +142,7 @@ void sp_xmlview_tree_destroy(GtkWidget * object)
 {
 	SPXMLViewTree * tree = SP_XMLVIEW_TREE (object);
 
-	sp_xmlview_tree_set_repr (tree, NULL);
+	sp_xmlview_tree_set_repr (tree, nullptr);
 
 	GTK_WIDGET_CLASS(sp_xmlview_tree_parent_class)->destroy (object);
 }
@@ -153,27 +153,27 @@ void sp_xmlview_tree_destroy(GtkWidget * object)
 GtkTreeRowReference *
 add_node (SPXMLViewTree * tree, GtkTreeIter *parent, GtkTreeIter *before, Inkscape::XML::Node * repr)
 {
-	NodeData * data = NULL;
+	NodeData * data = nullptr;
 	const Inkscape::XML::NodeEventVector * vec;
 	static const gchar *default_text[] = { "???" };
 
-	g_assert (tree != NULL);
-	g_assert (repr != NULL);
+	g_assert (tree != nullptr);
+	g_assert (repr != nullptr);
 
     if (before && !gtk_tree_store_iter_is_valid(tree->store, before)) {
-        before = NULL;
+        before = nullptr;
     }
 
 	GtkTreeIter iter;
     gtk_tree_store_insert_before (tree->store, &iter, parent, before);
 
     if (!gtk_tree_store_iter_is_valid(tree->store, &iter)) {
-        return NULL;
+        return nullptr;
     }
 
     GtkTreeRowReference  *rowref = tree_iter_to_ref (tree, &iter);
     data = node_data_new (tree, &iter, rowref, repr);
-    g_assert (data != NULL);
+    g_assert (data != nullptr);
 
 	gtk_tree_store_set (tree->store, &iter, STORE_TEXT_COL, default_text, STORE_DATA_COL, data, STORE_REPR_COL, repr, -1);
 
@@ -186,13 +186,13 @@ add_node (SPXMLViewTree * tree, GtkTreeIter *parent, GtkTreeIter *before, Inksca
 	} else if ( repr->type() == Inkscape::XML::ELEMENT_NODE ) {
 		vec = &element_repr_events;
 	} else {
-		vec = NULL;
+		vec = nullptr;
 	}
 
 	if (vec) {
 		/* cheat a little to get the id updated properly */
 		if (repr->type() == Inkscape::XML::ELEMENT_NODE) {
-			element_attr_changed (repr, "id", NULL, NULL, false, data);
+			element_attr_changed (repr, "id", nullptr, nullptr, false, data);
 		}
 		sp_repr_add_listener (repr, vec, data);
 		sp_repr_synthesize_events (repr, vec, data);
@@ -344,7 +344,7 @@ void on_drag_data_received(GtkWidget * /*wgt*/, GdkDragContext * /*context*/, in
        return;
     }
 
-    GtkTreeModel *model = 0;
+    GtkTreeModel *model = nullptr;
     GtkTreeIter iter;
     GtkTreeSelection *selection = gtk_tree_view_get_selection(GTK_TREE_VIEW(tree));
     if (gtk_tree_selection_get_selected(selection, &model, &iter)) {
@@ -352,7 +352,7 @@ void on_drag_data_received(GtkWidget * /*wgt*/, GdkDragContext * /*context*/, in
         tree->dndactive = TRUE;
 
         GtkTreeIter parent_iter;
-        GtkTreeRowReference  *parent_ref = NULL;
+        GtkTreeRowReference  *parent_ref = nullptr;
         if (gtk_tree_model_iter_parent(model, &parent_iter, &iter)) {
             parent_ref = tree_iter_to_ref (tree, &parent_iter);
         }
@@ -398,7 +398,7 @@ void on_row_changed(GtkTreeModel *tree_model, GtkTreePath *path, GtkTreeIter *it
 
     // Find the sibling node before iter
     GtkTreeIter before_iter;
-    Inkscape::XML::Node *before_repr = NULL;
+    Inkscape::XML::Node *before_repr = nullptr;
     GtkTreeIter tmp_iter;
 
     gboolean valid = gtk_tree_model_iter_children(tree_model, &tmp_iter, &new_parent);
@@ -538,7 +538,7 @@ gboolean tree_model_iter_compare(GtkTreeModel* store, GtkTreeIter * iter1, GtkTr
  */
 gboolean do_drag_motion(GtkWidget *widget, GdkDragContext *context, gint x, gint y, guint time, gpointer user_data)
 {
-    GtkTreePath *path = NULL;
+    GtkTreePath *path = nullptr;
     GtkTreeViewDropPosition pos;
     gtk_tree_view_get_dest_row_at_pos (GTK_TREE_VIEW(widget), x, y, &path, &pos);
 
@@ -585,7 +585,7 @@ sp_xmlview_tree_set_repr (SPXMLViewTree * tree, Inkscape::XML::Node * repr)
          *  Instead just unref the old and create a new store.
          */
         //gtk_tree_store_clear(tree->store);
-        gtk_tree_view_set_model(GTK_TREE_VIEW(tree), NULL);
+        gtk_tree_view_set_model(GTK_TREE_VIEW(tree), nullptr);
         g_object_unref(tree->store);
         tree->store = gtk_tree_store_new (STORE_N_COLS, G_TYPE_STRING, G_TYPE_POINTER, G_TYPE_POINTER);
         gtk_tree_view_set_model (GTK_TREE_VIEW(tree), GTK_TREE_MODEL(tree->store));
@@ -596,7 +596,7 @@ sp_xmlview_tree_set_repr (SPXMLViewTree * tree, Inkscape::XML::Node * repr)
     if (repr) {
         GtkTreeRowReference * rowref;
         Inkscape::GC::anchor(repr);
-        rowref = add_node (tree, NULL, NULL, repr);
+        rowref = add_node (tree, nullptr, nullptr, repr);
 
         // Set the tree model here, after all data is inserted
         gtk_tree_view_set_model (GTK_TREE_VIEW(tree), GTK_TREE_MODEL(tree->store));
@@ -604,7 +604,7 @@ sp_xmlview_tree_set_repr (SPXMLViewTree * tree, Inkscape::XML::Node * repr)
 
         GtkTreePath *path = gtk_tree_row_reference_get_path(rowref);
         gtk_tree_view_expand_to_path (GTK_TREE_VIEW(tree), path);
-        gtk_tree_view_scroll_to_cell (GTK_TREE_VIEW(tree), path, NULL, true, 0.5, 0.0);
+        gtk_tree_view_scroll_to_cell (GTK_TREE_VIEW(tree), path, nullptr, true, 0.5, 0.0);
         gtk_tree_path_free(path);
     }
 }
@@ -635,10 +635,10 @@ sp_xmlview_tree_get_repr_node (SPXMLViewTree * tree, Inkscape::XML::Node * repr,
     NodeData anode;
     anode.tree = tree;
     anode.repr = repr;
-    anode.rowref = NULL;
+    anode.rowref = nullptr;
 
     gtk_tree_model_foreach(GTK_TREE_MODEL(tree->store), foreach_func, &anode);
-    if (anode.rowref != NULL) {
+    if (anode.rowref != nullptr) {
         tree_ref_to_iter(tree, iter, anode.rowref);
         return TRUE;
     }
@@ -666,10 +666,10 @@ gboolean foreach_func(GtkTreeModel *model, GtkTreePath * /*path*/, GtkTreeIter *
  */
 gboolean search_equal_func(GtkTreeModel *model, gint /*column*/, const gchar *key, GtkTreeIter *iter, gpointer /*search_data*/)
 {
-    gchar *text = 0;
+    gchar *text = nullptr;
     gtk_tree_model_get(model, iter, STORE_TEXT_COL, &text, -1);
 
-    gboolean match = (strstr(text, key) != NULL);
+    gboolean match = (strstr(text, key) != nullptr);
 
     g_free(text);
 
diff --git a/src/widgets/spw-utilities.cpp b/src/widgets/spw-utilities.cpp
index 992f1f6b7..0dc041f80 100644
--- a/src/widgets/spw-utilities.cpp
+++ b/src/widgets/spw-utilities.cpp
@@ -32,8 +32,8 @@
 Gtk::Label * spw_label(Gtk::Grid *table, const gchar *label_text, int col, int row, Gtk::Widget* target)
 {
   Gtk::Label *label_widget = new Gtk::Label();
-  g_assert(label_widget != NULL);
-  if (target != NULL)
+  g_assert(label_widget != nullptr);
+  if (target != nullptr)
   {
     label_widget->set_text_with_mnemonic(label_text);
 	label_widget->set_mnemonic_widget(*target);
@@ -69,7 +69,7 @@ Gtk::HBox * spw_hbox(Gtk::Grid * table, int width, int col, int row)
 {
   /* Create a new hbox with a 4-pixel spacing between children */
   Gtk::HBox *hb = new Gtk::HBox(false, 4);
-  g_assert(hb != NULL);
+  g_assert(hb != nullptr);
   hb->show();
   hb->set_hexpand();
   hb->set_halign(Gtk::ALIGN_FILL);
@@ -94,7 +94,7 @@ sp_set_font_size_recursive (GtkWidget *w, gpointer font)
 
         gtk_css_provider_load_from_data(css_provider,
                                         css_data.str().c_str(),
-                                        -1, NULL);
+                                        -1, nullptr);
 
         auto style_context = gtk_widget_get_style_context(w);
         gtk_style_context_add_provider(style_context,
@@ -128,7 +128,7 @@ sp_set_font_size_smaller (GtkWidget *w)
  */
 gpointer sp_search_by_data_recursive(GtkWidget *w, gpointer key)
 {
-	gpointer r = NULL;
+	gpointer r = nullptr;
 
 	if (w && G_IS_OBJECT(w)) {
 		r = g_object_get_data(G_OBJECT(w), (gchar *) key);
@@ -143,7 +143,7 @@ gpointer sp_search_by_data_recursive(GtkWidget *w, gpointer key)
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -151,7 +151,7 @@ gpointer sp_search_by_data_recursive(GtkWidget *w, gpointer key)
  */
 GtkWidget *sp_search_by_value_recursive(GtkWidget *w, gchar *key, gchar *value)
 {
-	gchar *r = NULL;
+	gchar *r = nullptr;
 
 	if (w && G_IS_OBJECT(w)) {
 		r = (gchar *) g_object_get_data(G_OBJECT(w), key);
@@ -166,7 +166,7 @@ GtkWidget *sp_search_by_value_recursive(GtkWidget *w, gchar *key, gchar *value)
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /*
diff --git a/src/widgets/stroke-marker-selector.cpp b/src/widgets/stroke-marker-selector.cpp
index 95a8ce078..191d215f3 100644
--- a/src/widgets/stroke-marker-selector.cpp
+++ b/src/widgets/stroke-marker-selector.cpp
@@ -53,7 +53,7 @@ MarkerComboBox::MarkerComboBox(gchar const *id, int l) :
     set_model(marker_store);
     pack_start(image_renderer, false);
     set_cell_data_func(image_renderer, sigc::mem_fun(*this, &MarkerComboBox::prepareImageRenderer));
-    gtk_combo_box_set_row_separator_func(GTK_COMBO_BOX(gobj()), MarkerComboBox::separator_cb, NULL, NULL);
+    gtk_combo_box_set_row_separator_func(GTK_COMBO_BOX(gobj()), MarkerComboBox::separator_cb, nullptr, nullptr);
 
     empty_image = new Gtk::Image();
     empty_image->set_from_icon_name("no-marker", Gtk::ICON_SIZE_SMALL_TOOLBAR);
@@ -138,7 +138,7 @@ MarkerComboBox::init_combo()
     if (updating)
         return;
 
-    const gchar *active = NULL;
+    const gchar *active = nullptr;
     if (get_active()) {
         active = get_active()->get_value(marker_columns.marker);
     }
@@ -152,11 +152,11 @@ MarkerComboBox::init_combo()
         row[marker_columns.history] = false;
         row[marker_columns.separator] = false;
         set_sensitive(false);
-        set_current(NULL);
+        set_current(nullptr);
         return;
     }
 
-    static SPDocument *markers_doc = NULL;
+    static SPDocument *markers_doc = nullptr;
 
     // add separator
     Gtk::TreeModel::Row row_sep = *(marker_store->append());
@@ -171,7 +171,7 @@ MarkerComboBox::init_combo()
     sp_marker_list_from_doc(doc, true);
 
     // find and load markers.svg
-    if (markers_doc == NULL) {
+    if (markers_doc == nullptr) {
         char *markers_source = g_build_filename(INKSCAPE_MARKERSDIR, "markers.svg", NULL);
         if (Inkscape::IO::file_test(markers_source, G_FILE_TEST_IS_REGULAR)) {
             markers_doc = SPDocument::createNewDoc(markers_source, FALSE);
@@ -199,13 +199,13 @@ void MarkerComboBox::set_current(SPObject *marker)
 {
     updating = true;
 
-    if (marker != NULL) {
+    if (marker != nullptr) {
         gchar *markname = g_strdup(marker->getRepr()->attribute("id"));
         set_selected(markname);
         g_free (markname);
     }
     else {
-        set_selected(NULL);
+        set_selected(nullptr);
     }
 
     updating = false;
@@ -220,7 +220,7 @@ const gchar * MarkerComboBox::get_active_marker_uri()
     const gchar *markid = get_active()->get_value(marker_columns.marker);
     if (!markid)
     {
-        return NULL;
+        return nullptr;
     }
 
     gchar const *marker = "";
@@ -308,7 +308,7 @@ void MarkerComboBox::sp_marker_list_from_doc(SPDocument *source, gboolean histor
 std::vector<SPMarker *> MarkerComboBox::get_marker_list (SPDocument *source)
 {
     std::vector<SPMarker *> ml;
-    if (source == NULL)
+    if (source == nullptr)
         return ml;
 
     SPDefs *defs = source->getDefs();
@@ -446,8 +446,8 @@ MarkerComboBox::create_marker_image(unsigned psize, gchar const *mname,
 {
     // Retrieve the marker named 'mname' from the source SVG document
     SPObject const *marker = source->getObjectById(mname);
-    if (marker == NULL) {
-        return NULL;
+    if (marker == nullptr) {
+        return nullptr;
     }
 
     // Create a copy repr of the marker with id="sample"
@@ -509,8 +509,8 @@ MarkerComboBox::create_marker_image(unsigned psize, gchar const *mname,
     sandbox->getRoot()->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
     sandbox->ensureUpToDate();
 
-    if (object == NULL || !SP_IS_ITEM(object)) {
-        return NULL; // sandbox broken?
+    if (object == nullptr || !SP_IS_ITEM(object)) {
+        return nullptr; // sandbox broken?
     }
 
     SPItem *item = SP_ITEM(object);
@@ -518,7 +518,7 @@ MarkerComboBox::create_marker_image(unsigned psize, gchar const *mname,
     Geom::OptRect dbox = item->documentVisualBounds();
 
     if (!dbox) {
-        return NULL;
+        return nullptr;
     }
 
     /* Update to renderable state */
diff --git a/src/widgets/stroke-style.cpp b/src/widgets/stroke-style.cpp
index b127efcff..53b094206 100644
--- a/src/widgets/stroke-style.cpp
+++ b/src/widgets/stroke-style.cpp
@@ -74,7 +74,7 @@ SPObject* getMarkerObj(gchar const *n, SPDocument *doc)
     }
 
     if (*p == '\0' || p[1] == '\0') {
-        return NULL;
+        return nullptr;
     }
 
     p++;
@@ -84,7 +84,7 @@ SPObject* getMarkerObj(gchar const *n, SPDocument *doc)
     }
 
     if (p[c] == '\0') {
-        return NULL;
+        return nullptr;
     }
 
     gchar* b = g_strdup(p);
@@ -122,7 +122,7 @@ StrokeStyle::StrokeStyleButton::StrokeStyleButton(Gtk::RadioButtonGroup &grp,
 
     auto px = Gtk::manage(new Gtk::Image());
     px->set_from_icon_name(icon, Gtk::ICON_SIZE_LARGE_TOOLBAR);
-    g_assert(px != NULL);
+    g_assert(px != nullptr);
     px->show();
     add(*px);
 }
@@ -150,13 +150,13 @@ StrokeStyle::StrokeStyle() :
     capSquare(),
     dashSelector(),
     update(false),
-    desktop(0),
+    desktop(nullptr),
     selectChangedConn(),
     selectModifiedConn(),
     startMarkerConn(),
     midMarkerConn(),
     endMarkerConn(),
-    _old_unit(NULL)
+    _old_unit(nullptr)
 {
     Gtk::HBox *hb;
     Gtk::HBox *f = new Gtk::HBox(false, 0);
@@ -210,7 +210,7 @@ StrokeStyle::StrokeStyle() :
     i++;
 
     /* Dash */
-    spw_label(table, _("Dashes:"), 0, i, NULL); //no mnemonic for now
+    spw_label(table, _("Dashes:"), 0, i, nullptr); //no mnemonic for now
                                             //decide what to do:
                                             //   implement a set_mnemonic_source function in the
                                             //   SPDashSelector class, so that we do not have to
@@ -230,7 +230,7 @@ StrokeStyle::StrokeStyle() :
     // TRANSLATORS: Path markers are an SVG feature that allows you to attach arbitrary shapes
     // (arrowheads, bullets, faces, whatever) to the start, end, or middle nodes of a path.
 
-    spw_label(table, _("Markers:"), 0, i, NULL);
+    spw_label(table, _("Markers:"), 0, i, nullptr);
 
     hb = spw_hbox(table, 1, 1, i);
     i++;
@@ -267,7 +267,7 @@ StrokeStyle::StrokeStyle() :
     /* Join type */
     // TRANSLATORS: The line join style specifies the shape to be used at the
     //  corners of paths. It can be "miter", "round" or "bevel".
-    spw_label(table, _("Join:"), 0, i, NULL);
+    spw_label(table, _("Join:"), 0, i, nullptr);
 
     hb = spw_hbox(table, 3, 1, i);
 
@@ -318,7 +318,7 @@ StrokeStyle::StrokeStyle() :
     /* Cap type */
     // TRANSLATORS: cap type specifies the shape for the ends of lines
     //spw_label(t, _("_Cap:"), 0, i);
-    spw_label(table, _("Cap:"), 0, i, NULL);
+    spw_label(table, _("Cap:"), 0, i, nullptr);
 
     hb = spw_hbox(table, 3, 1, i);
 
@@ -349,7 +349,7 @@ StrokeStyle::StrokeStyle() :
 
     /* Paint order */
     // TRANSLATORS: Paint order determines the order the 'fill', 'stroke', and 'markers are painted.
-    spw_label(table, _("Order:"), 0, i, NULL);
+    spw_label(table, _("Order:"), 0, i, nullptr);
 
     hb = spw_hbox(table, 4, 1, i);
 
@@ -433,8 +433,8 @@ StrokeStyle::makeRadioButton(Gtk::RadioButtonGroup &grp,
                              StrokeStyleButtonType  button_type,
                              gchar const           *stroke_style)
 {
-    g_assert(icon != NULL);
-    g_assert(hb  != NULL);
+    g_assert(icon != nullptr);
+    g_assert(hb  != nullptr);
 
     StrokeStyleButton *tb = new StrokeStyleButton(grp, icon, button_type, stroke_style);
 
@@ -505,7 +505,7 @@ void StrokeStyle::markerSelectCB(MarkerComboBox *marker_combo, StrokeStyle *spw,
     }
 
     sp_repr_css_attr_unref(css);
-    css = 0;
+    css = nullptr;
 
     spw->update = false;
 };
@@ -579,7 +579,7 @@ SPObject *
 StrokeStyle::forkMarker(SPObject *marker, int loc, SPItem *item)
 {
     if (!item || !marker) {
-        return NULL;
+        return nullptr;
     }
 
     gchar const *marker_id = SPMarkerNames[loc].key;
@@ -609,7 +609,7 @@ StrokeStyle::forkMarker(SPObject *marker, int loc, SPItem *item)
     sp_repr_css_change_recursive(item->getRepr(), css_item, "style");
 
     sp_repr_css_attr_unref(css_item);
-    css_item = 0;
+    css_item = nullptr;
 
     return marker;
 }
@@ -692,7 +692,7 @@ StrokeStyle::setMarkerColor(SPObject *marker, int loc, SPItem *item)
     endMarkerCombo->update_marker_image(mid);
 
     sp_repr_css_attr_unref(css);
-    css = 0;
+    css = nullptr;
 
 
 }
@@ -751,7 +751,7 @@ StrokeStyle::setDashSelectorFromStyle(SPDashSelector *dsel, SPStyle *style)
                        style->stroke_dashoffset.value / style->stroke_width.computed  :
                        style->stroke_dashoffset.value);
     } else {
-        dsel->set_dash(0, NULL, 0.0);
+        dsel->set_dash(0, nullptr, 0.0);
     }
 }
 
@@ -761,7 +761,7 @@ StrokeStyle::setDashSelectorFromStyle(SPDashSelector *dsel, SPStyle *style)
 void
 StrokeStyle::setJoinType (unsigned const jointype)
 {
-    Gtk::RadioButton *tb = NULL;
+    Gtk::RadioButton *tb = nullptr;
     switch (jointype) {
         case SP_STROKE_LINEJOIN_MITER:
             tb = joinMiter;
@@ -787,7 +787,7 @@ StrokeStyle::setJoinType (unsigned const jointype)
 void
 StrokeStyle::setCapType (unsigned const captype)
 {
-    Gtk::RadioButton *tb = NULL;
+    Gtk::RadioButton *tb = nullptr;
     switch (captype) {
         case SP_STROKE_LINECAP_BUTT:
             tb = capButt;
@@ -857,7 +857,7 @@ StrokeStyle::updateLine()
 
     update = true;
 
-    Inkscape::Selection *sel = desktop ? desktop->getSelection() : NULL;
+    Inkscape::Selection *sel = desktop ? desktop->getSelection() : nullptr;
 
     FillOrStroke kind = GPOINTER_TO_INT(get_data("kind")) ? FILL : STROKE;
 
@@ -926,19 +926,19 @@ StrokeStyle::updateLine()
     if (! is_query_style_updateable(result_join)) {
         setJoinType(query.stroke_linejoin.value);
     } else {
-        setJoinButtons(NULL);
+        setJoinButtons(nullptr);
     }
 
     if (! is_query_style_updateable(result_cap)) {
         setCapType (query.stroke_linecap.value);
     } else {
-        setCapButtons(NULL);
+        setCapButtons(nullptr);
     }
 
     if (! is_query_style_updateable(result_order)) {
         setPaintOrder (query.paint_order.value);
     } else {
-        setPaintOrder (NULL);
+        setPaintOrder (nullptr);
     }
 
     if (!sel || sel->isEmpty())
@@ -982,7 +982,7 @@ StrokeStyle::setScaledDash(SPCSSAttr *css,
         sp_repr_css_set_property(css, "stroke-dashoffset", osoffset.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);
     }
 }
 
@@ -1061,7 +1061,7 @@ StrokeStyle::scaleLine()
     sp_desktop_set_style (desktop, css, false);
 
     sp_repr_css_attr_unref(css);
-    css = 0;
+    css = nullptr;
 
     DocumentUndo::done(document, SP_VERB_DIALOG_FILL_STROKE,
                        _("Set stroke style"));
@@ -1151,7 +1151,7 @@ void StrokeStyle::buttonToggledCB(StrokeStyleButton *tb, StrokeStyle *spw)
         }
 
         sp_repr_css_attr_unref(css);
-        css = 0;
+        css = nullptr;
 
         DocumentUndo::done(spw->desktop->getDocument(), SP_VERB_DIALOG_FILL_STROKE, _("Set stroke style"));
     }
@@ -1240,7 +1240,7 @@ StrokeStyle::updateAllMarkers(std::vector<SPItem*> const &objects, bool skip_und
 
         combo->setDesktop(desktop);
 
-        if (object->style->marker_ptrs[keyloc[i].loc]->value != NULL && !all_texts) {
+        if (object->style->marker_ptrs[keyloc[i].loc]->value != nullptr && !all_texts) {
             // If the object has this type of markers,
 
             // Extract the name of the marker that the object uses
@@ -1263,7 +1263,7 @@ StrokeStyle::updateAllMarkers(std::vector<SPItem*> const &objects, bool skip_und
             }
 
         } else {
-            combo->set_current(NULL);
+            combo->set_current(nullptr);
         }
     }
 
diff --git a/src/widgets/stroke-style.h b/src/widgets/stroke-style.h
index 274cc2b47..049782517 100644
--- a/src/widgets/stroke-style.h
+++ b/src/widgets/stroke-style.h
@@ -84,7 +84,7 @@ struct { gchar const *key; gint value; } const SPMarkerNames[] = {
     {"marker-mid", SP_MARKER_LOC_MID},
     {"marker-end", SP_MARKER_LOC_END},
     {"", SP_MARKER_LOC_QTY},
-    {NULL, -1}
+    {nullptr, -1}
 };
 
 /**
diff --git a/src/widgets/swatch-selector.cpp b/src/widgets/swatch-selector.cpp
index 3bfa83cd9..286dcc610 100644
--- a/src/widgets/swatch-selector.cpp
+++ b/src/widgets/swatch-selector.cpp
@@ -25,7 +25,7 @@ namespace Widgets
 
 SwatchSelector::SwatchSelector() :
     Gtk::VBox(),
-    _gsel(0),
+    _gsel(nullptr),
     _updating_color(false)
 {
     using Inkscape::UI::Widget::ColorNotebook;
@@ -52,7 +52,7 @@ SwatchSelector::SwatchSelector() :
 
 SwatchSelector::~SwatchSelector()
 {
-    _gsel = 0;
+    _gsel = nullptr;
 }
 
 SPGradientSelector *SwatchSelector::getGradientSelector()
@@ -124,7 +124,7 @@ void SwatchSelector::connectchangedHandler( GCallback handler, void *data )
 void SwatchSelector::setVector(SPDocument */*doc*/, SPGradient *vector)
 {
     //GtkVBox * box = gobj();
-    _gsel->setVector((vector) ? vector->document : 0, vector);
+    _gsel->setVector((vector) ? vector->document : nullptr, vector);
 
     if ( vector && vector->isSolid() ) {
         SPStop* stop = vector->getFirstStop();
diff --git a/src/widgets/toolbox.cpp b/src/widgets/toolbox.cpp
index c340e5291..7b3df3337 100644
--- a/src/widgets/toolbox.cpp
+++ b/src/widgets/toolbox.cpp
@@ -171,7 +171,7 @@ static struct {
 	{ "/tools/gradient", "gradient_tool",  SP_VERB_CONTEXT_GRADIENT, SP_VERB_CONTEXT_GRADIENT_PREFS },
 	{ "/tools/mesh",     "mesh_tool",      SP_VERB_CONTEXT_MESH, SP_VERB_CONTEXT_MESH_PREFS },
 	{ "/tools/dropper",  "dropper_tool",   SP_VERB_CONTEXT_DROPPER, SP_VERB_CONTEXT_DROPPER_PREFS },
-	{ NULL, NULL, 0, 0 }
+	{ nullptr, nullptr, 0, 0 }
 };
 
 static struct {
@@ -184,56 +184,56 @@ static struct {
     gchar const *swatch_tool;
     gchar const *swatch_tip;
 } const aux_toolboxes[] = {
-    { "/tools/select", "select_toolbox", 0, sp_select_toolbox_prep,            "SelectToolbar",
-      SP_VERB_INVALID, 0, 0},
-    { "/tools/nodes",   "node_toolbox",   0, sp_node_toolbox_prep,              "NodeToolbar",
-      SP_VERB_INVALID, 0, 0},
-    { "/tools/tweak",   "tweak_toolbox",   0, sp_tweak_toolbox_prep,              "TweakToolbar",
+    { "/tools/select", "select_toolbox", nullptr, sp_select_toolbox_prep,            "SelectToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
+    { "/tools/nodes",   "node_toolbox",   nullptr, sp_node_toolbox_prep,              "NodeToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
+    { "/tools/tweak",   "tweak_toolbox",   nullptr, sp_tweak_toolbox_prep,              "TweakToolbar",
       SP_VERB_CONTEXT_TWEAK_PREFS, "/tools/tweak", N_("Color/opacity used for color tweaking")},
-    { "/tools/spray",   "spray_toolbox",   0, sp_spray_toolbox_prep,              "SprayToolbar",
-      SP_VERB_INVALID, 0, 0},
+    { "/tools/spray",   "spray_toolbox",   nullptr, sp_spray_toolbox_prep,              "SprayToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
     { "/tools/zoom",   "zoom_toolbox",   Inkscape::UI::Toolbar::ZoomToolbar::create, nullptr, "ZoomToolbar",
-      SP_VERB_INVALID, 0, 0},
-    { "/tools/measure",   "measure_toolbox",   0, sp_measure_toolbox_prep,              "MeasureToolbar",
-      SP_VERB_INVALID, 0, 0},
-    { "/tools/shapes/star",   "star_toolbox",   0, sp_star_toolbox_prep,              "StarToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
+    { "/tools/measure",   "measure_toolbox",   nullptr, sp_measure_toolbox_prep,              "MeasureToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
+    { "/tools/shapes/star",   "star_toolbox",   nullptr, sp_star_toolbox_prep,              "StarToolbar",
       SP_VERB_CONTEXT_STAR_PREFS,   "/tools/shapes/star",     N_("Style of new stars")},
-    { "/tools/shapes/rect",   "rect_toolbox",   0, sp_rect_toolbox_prep,              "RectToolbar",
+    { "/tools/shapes/rect",   "rect_toolbox",   nullptr, sp_rect_toolbox_prep,              "RectToolbar",
       SP_VERB_CONTEXT_RECT_PREFS,   "/tools/shapes/rect",     N_("Style of new rectangles")},
-    { "/tools/shapes/3dbox",  "3dbox_toolbox",  0, box3d_toolbox_prep,             "3DBoxToolbar",
+    { "/tools/shapes/3dbox",  "3dbox_toolbox",  nullptr, box3d_toolbox_prep,             "3DBoxToolbar",
       SP_VERB_CONTEXT_3DBOX_PREFS,  "/tools/shapes/3dbox",    N_("Style of new 3D boxes")},
-    { "/tools/shapes/arc",    "arc_toolbox",    0, sp_arc_toolbox_prep,               "ArcToolbar",
+    { "/tools/shapes/arc",    "arc_toolbox",    nullptr, sp_arc_toolbox_prep,               "ArcToolbar",
       SP_VERB_CONTEXT_ARC_PREFS,    "/tools/shapes/arc",      N_("Style of new ellipses")},
-    { "/tools/shapes/spiral", "spiral_toolbox", 0, sp_spiral_toolbox_prep,            "SpiralToolbar",
+    { "/tools/shapes/spiral", "spiral_toolbox", nullptr, sp_spiral_toolbox_prep,            "SpiralToolbar",
       SP_VERB_CONTEXT_SPIRAL_PREFS, "/tools/shapes/spiral",   N_("Style of new spirals")},
-    { "/tools/freehand/pencil", "pencil_toolbox", 0, sp_pencil_toolbox_prep,            "PencilToolbar",
+    { "/tools/freehand/pencil", "pencil_toolbox", nullptr, sp_pencil_toolbox_prep,            "PencilToolbar",
       SP_VERB_CONTEXT_PENCIL_PREFS, "/tools/freehand/pencil", N_("Style of new paths created by Pencil")},
-    { "/tools/freehand/pen", "pen_toolbox", 0, sp_pen_toolbox_prep,                     "PenToolbar",
+    { "/tools/freehand/pen", "pen_toolbox", nullptr, sp_pen_toolbox_prep,                     "PenToolbar",
       SP_VERB_CONTEXT_PEN_PREFS,    "/tools/freehand/pen",    N_("Style of new paths created by Pen")},
-    { "/tools/calligraphic", "calligraphy_toolbox", 0, sp_calligraphy_toolbox_prep,"CalligraphyToolbar",
+    { "/tools/calligraphic", "calligraphy_toolbox", nullptr, sp_calligraphy_toolbox_prep,"CalligraphyToolbar",
       SP_VERB_CONTEXT_CALLIGRAPHIC_PREFS, "/tools/calligraphic", N_("Style of new calligraphic strokes")},
-    { "/tools/eraser", "eraser_toolbox", 0, sp_eraser_toolbox_prep,"EraserToolbar",
+    { "/tools/eraser", "eraser_toolbox", nullptr, sp_eraser_toolbox_prep,"EraserToolbar",
       SP_VERB_CONTEXT_ERASER_PREFS, "/tools/eraser", _("TBD")},
-    { "/tools/lpetool", "lpetool_toolbox", 0, sp_lpetool_toolbox_prep, "LPEToolToolbar",
+    { "/tools/lpetool", "lpetool_toolbox", nullptr, sp_lpetool_toolbox_prep, "LPEToolToolbar",
       SP_VERB_CONTEXT_LPETOOL_PREFS, "/tools/lpetool", _("TBD")},
     // If you change TextToolbar here, change it also in desktop-widget.cpp
-    { "/tools/text",   "text_toolbox",   0, sp_text_toolbox_prep, "TextToolbar",
-      SP_VERB_INVALID, 0, 0},
-    { "/tools/dropper", "dropper_toolbox", 0, sp_dropper_toolbox_prep,         "DropperToolbar",
-      SP_VERB_INVALID, 0, 0},
-    { "/tools/connector", "connector_toolbox", 0, sp_connector_toolbox_prep,   "ConnectorToolbar",
-      SP_VERB_INVALID, 0, 0},
-    { "/tools/gradient", "gradient_toolbox", 0, sp_gradient_toolbox_prep, "GradientToolbar",
-      SP_VERB_INVALID, 0, 0},
-    { "/tools/mesh", "mesh_toolbox", 0, sp_mesh_toolbox_prep, "MeshToolbar",
-      SP_VERB_INVALID, 0, 0},
+    { "/tools/text",   "text_toolbox",   nullptr, sp_text_toolbox_prep, "TextToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
+    { "/tools/dropper", "dropper_toolbox", nullptr, sp_dropper_toolbox_prep,         "DropperToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
+    { "/tools/connector", "connector_toolbox", nullptr, sp_connector_toolbox_prep,   "ConnectorToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
+    { "/tools/gradient", "gradient_toolbox", nullptr, sp_gradient_toolbox_prep, "GradientToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
+    { "/tools/mesh", "mesh_toolbox", nullptr, sp_mesh_toolbox_prep, "MeshToolbar",
+      SP_VERB_INVALID, nullptr, nullptr},
 #if HAVE_POTRACE
-    { "/tools/paintbucket",  "paintbucket_toolbox",  0, sp_paintbucket_toolbox_prep, "PaintbucketToolbar",
+    { "/tools/paintbucket",  "paintbucket_toolbox",  nullptr, sp_paintbucket_toolbox_prep, "PaintbucketToolbar",
       SP_VERB_CONTEXT_PAINTBUCKET_PREFS, "/tools/paintbucket", N_("Style of Paint Bucket fill objects")},
 #else
     { "/tools/paintbucket",  "paintbucket_toolbox",  0, NULL, "PaintbucketToolbar", SP_VERB_NONE, "/tools/paintbucket", N_("Disabled")},
 #endif
-    { NULL, NULL, NULL, NULL, NULL, SP_VERB_INVALID, NULL, NULL }
+    { nullptr, nullptr, nullptr, nullptr, nullptr, SP_VERB_INVALID, nullptr, nullptr }
 };
 
 
@@ -293,7 +293,7 @@ Glib::RefPtr<VerbAction> VerbAction::create(Inkscape::Verb* verb, Inkscape::Verb
 }
 
 VerbAction::VerbAction(Inkscape::Verb* verb, Inkscape::Verb* verb2, Inkscape::UI::View::View *view) :
-    Gtk::Action(Glib::ustring(verb->get_id()), verb->get_image(), Glib::ustring(g_dpgettext2(NULL, "ContextVerb", verb->get_name())), Glib::ustring(_(verb->get_tip()))),
+    Gtk::Action(Glib::ustring(verb->get_id()), verb->get_image(), Glib::ustring(g_dpgettext2(nullptr, "ContextVerb", verb->get_name())), Glib::ustring(_(verb->get_tip()))),
     verb(verb),
     verb2(verb2),
     view(view),
@@ -316,7 +316,7 @@ Gtk::Widget* VerbAction::create_tool_item_vfunc()
 {
 //     Gtk::Widget* widg = Gtk::Action::create_tool_item_vfunc();
     GtkIconSize toolboxSize = ToolboxFactory::prefToSize("/toolbox/tools/small");
-    GtkWidget* toolbox = 0;
+    GtkWidget* toolbox = nullptr;
     GtkToolItem *button_toolitem = sp_toolbox_button_item_new_from_verb_with_doubleclick( toolbox, toolboxSize,
                                                                                       SP_BUTTON_TYPE_TOGGLE,
                                                                                       verb,
@@ -369,7 +369,7 @@ void VerbAction::on_activate()
     if ( verb ) {
         SPAction *action = verb->get_action(Inkscape::ActionContext(view));
         if ( action ) {
-            sp_action_perform(action, 0);
+            sp_action_perform(action, nullptr);
         }
     }
 }
@@ -391,8 +391,8 @@ void purge_repr_listener( GObject* /*obj*/, GObject* tbl )
     if (oldrepr) { // remove old listener
         sp_repr_remove_listener_by_data(oldrepr, tbl);
         Inkscape::GC::release(oldrepr);
-        oldrepr = 0;
-        g_object_set_data( tbl, "repr", NULL );
+        oldrepr = nullptr;
+        g_object_set_data( tbl, "repr", nullptr );
     }
 }
 
@@ -459,14 +459,14 @@ GtkToolItem * sp_toolbox_button_item_new_from_verb_with_doubleclick(GtkWidget *t
 {
     SPAction *action = verb->get_action(Inkscape::ActionContext(view));
     if (!action) {
-        return NULL;
+        return nullptr;
     }
 
     SPAction *doubleclick_action;
     if (doubleclick_verb) {
         doubleclick_action = doubleclick_verb->get_action(Inkscape::ActionContext(view));
     } else {
-        doubleclick_action = NULL;
+        doubleclick_action = nullptr;
     }
 
     /* fixme: Handle sensitive/unsensitive */
@@ -501,13 +501,13 @@ static void trigger_sp_action( GtkAction* /*act*/, gpointer user_data )
 {
     SPAction* targetAction = SP_ACTION(user_data);
     if ( targetAction ) {
-        sp_action_perform( targetAction, NULL );
+        sp_action_perform( targetAction, nullptr );
     }
 }
 
 static GtkAction* create_action_for_verb( Inkscape::Verb* verb, Inkscape::UI::View::View* view, GtkIconSize size )
 {
-    GtkAction* act = 0;
+    GtkAction* act = nullptr;
 
     SPAction* targetAction = verb->get_action(Inkscape::ActionContext(view));
     InkAction* inky = ink_action_new( verb->get_id(), _(verb->get_name()), verb->get_tip(), verb->get_image(), size  );
@@ -587,7 +587,7 @@ static Glib::RefPtr<Gtk::ActionGroup> create_or_fetch_actions( SPDesktop* deskto
 
     GtkIconSize toolboxSize = ToolboxFactory::prefToSize("/toolbox/small");
     Glib::RefPtr<Gtk::ActionGroup> mainActions;
-    if (desktop == NULL)
+    if (desktop == nullptr)
     {
         return mainActions;
     }
@@ -636,7 +636,7 @@ static Glib::RefPtr<Gtk::ActionGroup> create_or_fetch_actions( SPDesktop* deskto
 
 static GtkWidget* toolboxNewCommon( GtkWidget* tb, BarId id, GtkPositionType /*handlePos*/ )
 {
-    g_object_set_data(G_OBJECT(tb), "desktop", NULL);
+    g_object_set_data(G_OBJECT(tb), "desktop", nullptr);
 
     gtk_widget_set_sensitive(tb, FALSE);
 
@@ -729,7 +729,7 @@ EgeAdjustmentAction * create_adjustment_action( gchar const *name,
 
     g_signal_connect( G_OBJECT(adj), "value-changed", G_CALLBACK(callback), dataKludge );
 
-    EgeAdjustmentAction* act = ege_adjustment_action_new( adj, name, label, tooltip, 0, climb, digits, unit_tracker );
+    EgeAdjustmentAction* act = ege_adjustment_action_new( adj, name, label, tooltip, nullptr, climb, digits, unit_tracker );
     if ( shortLabel ) {
         g_object_set( act, "short_label", shortLabel, NULL );
     }
@@ -770,8 +770,8 @@ void ToolboxFactory::setToolboxDesktop(GtkWidget *toolbox, SPDesktop *desktop)
 
     BarId id = static_cast<BarId>( GPOINTER_TO_INT(g_object_get_data(G_OBJECT(toolbox), BAR_ID_KEY)) );
 
-    SetupFunction setup_func = 0;
-    UpdateFunction update_func = 0;
+    SetupFunction setup_func = nullptr;
+    UpdateFunction update_func = nullptr;
 
     switch (id) {
         case BAR_TOOL:
@@ -832,7 +832,7 @@ static void setupToolboxCommon( GtkWidget *toolbox,
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
     GtkUIManager* mgr = gtk_ui_manager_new();
-    GError* err = 0;
+    GError* err = nullptr;
 
     GtkOrientation orientation = GTK_ORIENTATION_HORIZONTAL;
 
@@ -859,7 +859,7 @@ static void setupToolboxCommon( GtkWidget *toolbox,
     gtk_orientable_set_orientation (GTK_ORIENTABLE(toolBar), orientation);
     gtk_toolbar_set_show_arrow(GTK_TOOLBAR(toolBar), TRUE);
 
-    g_object_set_data(G_OBJECT(toolBar), "desktop", NULL);
+    g_object_set_data(G_OBJECT(toolBar), "desktop", nullptr);
 
     GtkWidget* child = gtk_bin_get_child(GTK_BIN(toolbox));
     if ( child ) {
@@ -956,7 +956,7 @@ void update_tool_toolbox( SPDesktop *desktop, ToolBase *eventcontext, GtkWidget
 {
     gchar const *const tname = ( eventcontext
                                  ? eventcontext->getPrefsPath().c_str() //g_type_name(G_OBJECT_TYPE(eventcontext))
-                                 : NULL );
+                                 : nullptr );
     Glib::RefPtr<Gtk::ActionGroup> mainActions = create_or_fetch_actions( desktop );
 
     for (int i = 0 ; tools[i].type_name ; i++ ) {
@@ -977,7 +977,7 @@ void setup_aux_toolbox(GtkWidget *toolbox, SPDesktop *desktop)
     GtkSizeGroup* grouper = gtk_size_group_new( GTK_SIZE_GROUP_BOTH );
     Glib::RefPtr<Gtk::ActionGroup> mainActions = create_or_fetch_actions( desktop );
     GtkUIManager* mgr = gtk_ui_manager_new();
-    GError *err = 0;
+    GError *err = nullptr;
     gtk_ui_manager_insert_action_group( mgr, mainActions->gobj(), 0 );
 
     Glib::ustring filename = get_filename(UIS, "select-toolbar.ui");
@@ -1002,8 +1002,8 @@ void setup_aux_toolbox(GtkWidget *toolbox, SPDesktop *desktop)
             aux_toolboxes[i].prep_func( desktop, mainActions->gobj(), G_OBJECT(kludge) );
         } else {
 
-            GtkWidget *sub_toolbox = 0;
-            if (aux_toolboxes[i].create_func == NULL) {
+            GtkWidget *sub_toolbox = nullptr;
+            if (aux_toolboxes[i].create_func == nullptr) {
                 sub_toolbox = sp_empty_toolbox_new(desktop);
             } else {
                 sub_toolbox = aux_toolboxes[i].create_func(desktop);
@@ -1029,7 +1029,7 @@ void setup_aux_toolbox(GtkWidget *toolbox, SPDesktop *desktop)
             gchar* tmp = g_strdup_printf( "/ui/%s", aux_toolboxes[i].ui_name );
             GtkWidget* toolBar = gtk_ui_manager_get_widget( mgr, tmp );
             g_free( tmp );
-            tmp = 0;
+            tmp = nullptr;
 
             if ( prefs->getBool( "/toolbox/icononly", true) ) {
                 gtk_toolbar_set_style( GTK_TOOLBAR(toolBar), GTK_TOOLBAR_ICONS );
@@ -1041,7 +1041,7 @@ void setup_aux_toolbox(GtkWidget *toolbox, SPDesktop *desktop)
             gtk_grid_attach( GTK_GRID(holder), toolBar, 0, 0, 1, 1);
 
             if ( aux_toolboxes[i].swatch_verb_id != SP_VERB_INVALID ) {
-                Inkscape::UI::Widget::StyleSwatch *swatch = new Inkscape::UI::Widget::StyleSwatch( NULL, _(aux_toolboxes[i].swatch_tip) );
+                Inkscape::UI::Widget::StyleSwatch *swatch = new Inkscape::UI::Widget::StyleSwatch( nullptr, _(aux_toolboxes[i].swatch_tip) );
                 swatch->setDesktop( desktop );
                 swatch->setClickVerb( aux_toolboxes[i].swatch_verb_id );
                 swatch->setWatchedTool( aux_toolboxes[i].swatch_tool, true );
@@ -1081,7 +1081,7 @@ void update_aux_toolbox(SPDesktop * /*desktop*/, ToolBase *eventcontext, GtkWidg
 {
     gchar const *tname = ( eventcontext
                            ? eventcontext->getPrefsPath().c_str() //g_type_name(G_OBJECT_TYPE(eventcontext))
-                           : NULL );
+                           : nullptr );
     for (int i = 0 ; aux_toolboxes[i].type_name ; i++ ) {
         GtkWidget *sub_toolbox = GTK_WIDGET(g_object_get_data(G_OBJECT(toolbox), aux_toolboxes[i].data_name));
         if (tname && !strcmp(tname, aux_toolboxes[i].type_name)) {
@@ -1112,11 +1112,11 @@ static void toggle_snap_callback(GtkToggleAction *act, gpointer data) //data poi
     }
 
     gpointer ptr = g_object_get_data(G_OBJECT(data), "desktop");
-    g_assert(ptr != NULL);
+    g_assert(ptr != nullptr);
 
     SPDesktop *dt = reinterpret_cast<SPDesktop*>(ptr);
     SPNamedView *nv = dt->getNamedView();
-    if (nv == NULL) {
+    if (nv == nullptr) {
         g_warning("No namedview specified (in toggle_snap_callback)!");
         return;
     }
@@ -1124,7 +1124,7 @@ static void toggle_snap_callback(GtkToggleAction *act, gpointer data) //data poi
     SPDocument *doc = nv->document;
     Inkscape::XML::Node *repr = nv->getRepr();
 
-    if (repr == NULL) {
+    if (repr == nullptr) {
         g_warning("This namedview doesn't have a xml representation attached!");
         return;
     }
@@ -1442,11 +1442,11 @@ Glib::ustring ToolboxFactory::getToolboxName(GtkWidget* toolbox)
 
 void ToolboxFactory::updateSnapToolbox(SPDesktop *desktop, ToolBase * /*eventcontext*/, GtkWidget *toolbox)
 {
-    g_assert(desktop != NULL);
-    g_assert(toolbox != NULL);
+    g_assert(desktop != nullptr);
+    g_assert(toolbox != nullptr);
 
     SPNamedView *nv = desktop->getNamedView();
-    if (nv == NULL) {
+    if (nv == nullptr) {
         g_warning("Namedview cannot be retrieved (in updateSnapToolbox)!");
         return;
     }
diff --git a/src/widgets/toolbox.h b/src/widgets/toolbox.h
index a1dc0770b..47a5639de 100644
--- a/src/widgets/toolbox.h
+++ b/src/widgets/toolbox.h
@@ -82,7 +82,7 @@ public:
      * @param callback function to invoke when changes are pushed.
      * @param cbData data to be passed on to the callback function.
      */
-    PrefPusher( GtkToggleAction *act, Glib::ustring const &path, void (*callback)(GObject*) = 0, GObject *cbData = 0 );
+    PrefPusher( GtkToggleAction *act, Glib::ustring const &path, void (*callback)(GObject*) = nullptr, GObject *cbData = nullptr );
 
     /**
      * Destructor that unregisters the preference callback.
@@ -135,7 +135,7 @@ void delete_connection(GObject * /*obj*/, sigc::connection *connection);
                                                        gdouble lower, gdouble upper, gdouble step, gdouble page,
                                                        gchar const** descrLabels, gdouble const* descrValues, guint descrCount,
                                                        void (*callback)(GtkAdjustment *, GObject *),
-                                                       Inkscape::UI::Widget::UnitTracker *unit_tracker = NULL,
+                                                       Inkscape::UI::Widget::UnitTracker *unit_tracker = nullptr,
                                                        gdouble climb = 0.1, guint digits = 3, double factor = 1.0 );
 
 #endif /* !SEEN_TOOLBOX_H */