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

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

20 files changed, 303 insertions, 303 deletions

diff --git a/src/ui/toolbar/arc-toolbar.cpp b/src/ui/toolbar/arc-toolbar.cpp
index ad1b70a6c..b8650e2b8 100644
--- a/src/ui/toolbar/arc-toolbar.cpp
+++ b/src/ui/toolbar/arc-toolbar.cpp
@@ -96,7 +96,7 @@ static void sp_arctb_value_changed(GtkAdjustment *adj, GObject *tbl, gchar const
 
     UnitTracker* tracker = reinterpret_cast<UnitTracker*>(g_object_get_data( tbl, "tracker" ));
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
 
     SPDocument* document = desktop->getDocument();
     Geom::Scale scale = document->getDocumentScale();
@@ -265,7 +265,7 @@ static void sp_arctb_type_changed( GObject *tbl, int type )
         SPItem *item = *i;
         if (SP_IS_GENERICELLIPSE(item)) {
             Inkscape::XML::Node *repr = item->getRepr();
-            repr->setAttribute("sodipodi:open", (open?"true":NULL) );
+            repr->setAttribute("sodipodi:open", (open?"true":nullptr) );
             repr->setAttribute("sodipodi:arc-type", arc_type.c_str());
             item->updateRepr();
             modmade = true;
@@ -321,7 +321,7 @@ static void arc_tb_event_attr_changed(Inkscape::XML::Node *repr, gchar const * /
 
         UnitTracker* tracker = reinterpret_cast<UnitTracker*>( g_object_get_data( tbl, "tracker" ) );
         Unit const *unit = tracker->getActiveUnit();
-        g_return_if_fail(unit != NULL);
+        g_return_if_fail(unit != nullptr);
 
         GtkAdjustment *adj;
         adj = GTK_ADJUSTMENT( g_object_get_data(tbl, "rx") );
@@ -354,10 +354,10 @@ static void arc_tb_event_attr_changed(Inkscape::XML::Node *repr, gchar const * /
 
     sp_arctb_sensitivize( tbl, gtk_adjustment_get_value(adj1), gtk_adjustment_get_value(adj2) );
 
-    char const *arctypestr = NULL;
+    char const *arctypestr = nullptr;
     arctypestr = repr->attribute("sodipodi:arc-type");
     if (!arctypestr) { // For old files.
-        char const *openstr = NULL;
+        char const *openstr = nullptr;
         openstr = repr->attribute("sodipodi:open");
         arctypestr = (openstr ? "arc" : "slice");
     }
@@ -377,22 +377,22 @@ static void arc_tb_event_attr_changed(Inkscape::XML::Node *repr, gchar const * /
 }
 
 static Inkscape::XML::NodeEventVector arc_tb_repr_events = {
-    NULL, /* child_added */
-    NULL, /* child_removed */
+    nullptr, /* child_added */
+    nullptr, /* child_removed */
     arc_tb_event_attr_changed,
-    NULL, /* content_changed */
-    NULL  /* order_changed */
+    nullptr, /* content_changed */
+    nullptr  /* order_changed */
 };
 
 
 static void sp_arc_toolbox_selection_changed(Inkscape::Selection *selection, GObject *tbl)
 {
     int n_selected = 0;
-    Inkscape::XML::Node *repr = NULL;
-    SPItem *item = NULL;
+    Inkscape::XML::Node *repr = nullptr;
+    SPItem *item = nullptr;
 
     if ( g_object_get_data( tbl, "repr" ) ) {
-        g_object_set_data( tbl, "item", NULL );
+        g_object_set_data( tbl, "item", nullptr );
     }
     purge_repr_listener( tbl, tbl );
 
@@ -440,7 +440,7 @@ void sp_arc_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObjec
 {
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
     GtkIconSize secondarySize = ToolboxFactory::prefToSize("/toolbox/secondary", 1);
 
     UnitTracker* tracker = new UnitTracker(Inkscape::Util::UNIT_TYPE_LINEAR);
@@ -448,7 +448,7 @@ void sp_arc_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObjec
     g_object_set_data( holder, "tracker", tracker );
 
     {
-        EgeOutputAction* act = ege_output_action_new( "ArcStateAction", _("<b>New:</b>"), "", 0 );
+        EgeOutputAction* act = ege_output_action_new( "ArcStateAction", _("<b>New:</b>"), "", nullptr );
         ege_output_action_set_use_markup( act, TRUE );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
         g_object_set_data( holder, "mode_action", act );
@@ -456,7 +456,7 @@ void sp_arc_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObjec
 
     /* Radius X */
     {
-        gchar const* labels[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+        gchar const* labels[] = {nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {1, 2, 3, 5, 10, 20, 50, 100, 200, 500};
         eact = create_adjustment_action( "ArcRadiusXAction",
                                          _("Horizontal radius"), _("Rx:"), _("Horizontal radius of the circle, ellipse, or arc"),
@@ -472,12 +472,12 @@ void sp_arc_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObjec
 
     /* Radius Y */
     {
-        gchar const* labels[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+        gchar const* labels[] = {nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {1, 2, 3, 5, 10, 20, 50, 100, 200, 500};
         eact = create_adjustment_action( "ArcRadiusYAction",
                                          _("Vertical radius"), _("Ry:"), _("Vertical radius of the circle, ellipse, or arc"),
                                          "/tools/shapes/arc/ry", 0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0, 1e6, SPIN_STEP, SPIN_PAGE_STEP,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_arctb_ry_value_changed, tracker);
@@ -500,7 +500,7 @@ void sp_arc_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObjec
                                          "/tools/shapes/arc/start", 0.0,
                                          GTK_WIDGET(desktop->canvas), holder, TRUE, "altx-arc",
                                          -360.0, 360.0, 1.0, 10.0,
-                                         0, 0, 0,
+                                         nullptr, nullptr, 0,
                                          sp_arctb_start_value_changed);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
     }
@@ -511,9 +511,9 @@ void sp_arc_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObjec
                                          _("End"), _("End:"),
                                          _("The angle (in degrees) from the horizontal to the arc's end point"),
                                          "/tools/shapes/arc/end", 0.0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          -360.0, 360.0, 1.0, 10.0,
-                                         0, 0, 0,
+                                         nullptr, nullptr, 0,
                                          sp_arctb_end_value_changed);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
     }
@@ -597,7 +597,7 @@ static void arc_toolbox_check_ec(SPDesktop* desktop, Inkscape::UI::Tools::ToolBa
     } else {
         if (changed) {
             changed.disconnect();
-            purge_repr_listener(NULL, holder);
+            purge_repr_listener(nullptr, holder);
         }
     }
 }
diff --git a/src/ui/toolbar/box3d-toolbar.cpp b/src/ui/toolbar/box3d-toolbar.cpp
index 846aea59d..7e7c8df10 100644
--- a/src/ui/toolbar/box3d-toolbar.cpp
+++ b/src/ui/toolbar/box3d-toolbar.cpp
@@ -103,9 +103,9 @@ static void box3d_resync_toolbar(Inkscape::XML::Node *persp_repr, GObject *data)
     }
 
     GtkWidget *tbl = GTK_WIDGET(data);
-    GtkAdjustment *adj = 0;
-    GtkAction *act = 0;
-    GtkToggleAction *tact = 0;
+    GtkAdjustment *adj = nullptr;
+    GtkAction *act = nullptr;
+    GtkToggleAction *tact = nullptr;
     Persp3D *persp = persp3d_get_from_repr(persp_repr);
     if (!persp) {
         // Hmm, is it an error if this happens?
@@ -165,11 +165,11 @@ static void box3d_persp_tb_event_attr_changed(Inkscape::XML::Node *repr,
 
 static Inkscape::XML::NodeEventVector box3d_persp_tb_repr_events =
 {
-    NULL, /* child_added */
-    NULL, /* child_removed */
+    nullptr, /* child_added */
+    nullptr, /* child_removed */
     box3d_persp_tb_event_attr_changed,
-    NULL, /* content_changed */
-    NULL  /* order_changed */
+    nullptr, /* content_changed */
+    nullptr  /* order_changed */
 };
 
 /**
@@ -183,7 +183,7 @@ static void box3d_toolbox_selection_changed(Inkscape::Selection *selection, GObj
     // disable the angle entry fields for this direction (otherwise entering a value in them should only
     // update the perspectives with infinite VPs and leave the other ones untouched).
 
-    Inkscape::XML::Node *persp_repr = NULL;
+    Inkscape::XML::Node *persp_repr = nullptr;
     purge_repr_listener(tbl, tbl);
 
     SPItem *item = selection->singleItem();
@@ -290,17 +290,17 @@ static void box3d_toolbox_check_ec(SPDesktop* dt, Inkscape::UI::Tools::ToolBase*
 void box3d_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject* holder)
 {
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
     SPDocument *document = desktop->getDocument();
     Persp3DImpl *persp_impl = document->getCurrentPersp3DImpl();
 
-    EgeAdjustmentAction* box3d_angle_x = 0;
-    EgeAdjustmentAction* box3d_angle_y = 0;
-    EgeAdjustmentAction* box3d_angle_z = 0;
+    EgeAdjustmentAction* box3d_angle_x = nullptr;
+    EgeAdjustmentAction* box3d_angle_y = nullptr;
+    EgeAdjustmentAction* box3d_angle_z = nullptr;
 
     /* Angle X */
     {
-        gchar const* labels[] = { 0, 0, 0, 0, 0, 0, 0 };
+        gchar const* labels[] = { nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr };
         gdouble values[] = {-90, -60, -30, 0, 30, 60, 90};
         eact = create_adjustment_action( "3DBoxAngleXAction",
                                          _("Angle in X direction"), _("Angle X:"),
@@ -340,14 +340,14 @@ void box3d_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject
 
     /* Angle Y */
     {
-        gchar const* labels[] = { 0, 0, 0, 0, 0, 0, 0 };
+        gchar const* labels[] = { nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr };
         gdouble values[] = {-90, -60, -30, 0, 30, 60, 90};
         eact = create_adjustment_action( "3DBoxAngleYAction",
                                          _("Angle in Y direction"), _("Angle Y:"),
                                          // Translators: PL is short for 'perspective line'
                                          _("Angle of PLs in Y direction"),
                                          "/tools/shapes/3dbox/box3d_angle_y", 30,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          -360.0, 360.0, 1.0, 10.0,
                                          labels, values, G_N_ELEMENTS(labels),
                                          box3d_angle_y_value_changed );
@@ -379,14 +379,14 @@ void box3d_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject
 
     /* Angle Z */
     {
-        gchar const* labels[] = { 0, 0, 0, 0, 0, 0, 0 };
+        gchar const* labels[] = { nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr };
         gdouble values[] = {-90, -60, -30, 0, 30, 60, 90};
         eact = create_adjustment_action( "3DBoxAngleZAction",
                                          _("Angle in Z direction"), _("Angle Z:"),
                                          // Translators: PL is short for 'perspective line'
                                          _("Angle of PLs in Z direction"),
                                          "/tools/shapes/3dbox/box3d_angle_z", 30,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          -360.0, 360.0, 1.0, 10.0,
                                          labels, values, G_N_ELEMENTS(labels),
                                          box3d_angle_z_value_changed );
diff --git a/src/ui/toolbar/calligraphy-toolbar.cpp b/src/ui/toolbar/calligraphy-toolbar.cpp
index 44271531e..7f4d9648a 100644
--- a/src/ui/toolbar/calligraphy-toolbar.cpp
+++ b/src/ui/toolbar/calligraphy-toolbar.cpp
@@ -382,7 +382,7 @@ static void sp_ddc_change_profile(GObject* tbl, int mode)
 
 static void sp_ddc_edit_profile(GtkAction * /*act*/, GObject* tbl)
 {
-    sp_dcc_save_profile(NULL, tbl);
+    sp_dcc_save_profile(nullptr, tbl);
 }
 
 void sp_calligraphy_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject* holder)
@@ -391,11 +391,11 @@ void sp_calligraphy_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
     {
         g_object_set_data(holder, "presets_blocked", GINT_TO_POINTER(TRUE));
 
-        EgeAdjustmentAction* calligraphy_angle = 0;
+        EgeAdjustmentAction* calligraphy_angle = nullptr;
 
         {
         /* Width */
-        gchar const* labels[] = {_("(hairline)"), 0, 0, 0, _("(default)"), 0, 0, 0, 0, _("(broad stroke)")};
+        gchar const* labels[] = {_("(hairline)"), nullptr, nullptr, nullptr, _("(default)"), nullptr, nullptr, nullptr, nullptr, _("(broad stroke)")};
         gdouble values[] = {1, 3, 5, 10, 15, 20, 30, 50, 75, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "CalligraphyWidthAction",
                                                               _("Pen Width"), _("Width:"),
@@ -404,7 +404,7 @@ void sp_calligraphy_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
                                                               GTK_WIDGET(desktop->canvas), holder, TRUE, "altx-calligraphy",
                                                               1, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_ddc_width_value_changed, NULL /*unit tracker*/, 1, 0 );
+                                                              sp_ddc_width_value_changed, nullptr /*unit tracker*/, 1, 0 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -412,23 +412,23 @@ void sp_calligraphy_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
 
         {
         /* Thinning */
-            gchar const* labels[] = {_("(speed blows up stroke)"), 0, 0, _("(slight widening)"), _("(constant width)"), _("(slight thinning, default)"), 0, 0, _("(speed deflates stroke)")};
+            gchar const* labels[] = {_("(speed blows up stroke)"), nullptr, nullptr, _("(slight widening)"), _("(constant width)"), _("(slight thinning, default)"), nullptr, nullptr, _("(speed deflates stroke)")};
             gdouble values[] = {-100, -40, -20, -10, 0, 10, 20, 40, 100};
         EgeAdjustmentAction* eact = create_adjustment_action( "ThinningAction",
                                                               _("Stroke Thinning"), _("Thinning:"),
                                                               _("How much velocity thins the stroke (> 0 makes fast strokes thinner, < 0 makes them broader, 0 makes width independent of velocity)"),
                                                               "/tools/calligraphic/thinning", 10,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               -100, 100, 1, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_ddc_velthin_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_ddc_velthin_value_changed, nullptr /*unit tracker*/, 1, 0);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
         }
 
         {
         /* Angle */
-        gchar const* labels[] = {_("(left edge up)"), 0, 0, _("(horizontal)"), _("(default)"), 0, _("(right edge up)")};
+        gchar const* labels[] = {_("(left edge up)"), nullptr, nullptr, _("(horizontal)"), _("(default)"), nullptr, _("(right edge up)")};
         gdouble values[] = {-90, -60, -30, 0, 30, 60, 90};
         EgeAdjustmentAction* eact = create_adjustment_action( "AngleAction",
                                                               _("Pen Angle"), _("Angle:"),
@@ -437,7 +437,7 @@ void sp_calligraphy_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
                                                               GTK_WIDGET(desktop->canvas), holder, TRUE, "calligraphy-angle",
                                                               -90.0, 90.0, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_ddc_angle_value_changed, NULL /*unit tracker*/, 1, 0 );
+                                                              sp_ddc_angle_value_changed, nullptr /*unit tracker*/, 1, 0 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         g_object_set_data( holder, "angle_action", eact );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -446,49 +446,49 @@ void sp_calligraphy_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
 
         {
         /* Fixation */
-            gchar const* labels[] = {_("(perpendicular to stroke, \"brush\")"), 0, 0, 0, _("(almost fixed, default)"), _("(fixed by Angle, \"pen\")")};
+            gchar const* labels[] = {_("(perpendicular to stroke, \"brush\")"), nullptr, nullptr, nullptr, _("(almost fixed, default)"), _("(fixed by Angle, \"pen\")")};
         gdouble values[] = {0, 20, 40, 60, 90, 100};
         EgeAdjustmentAction* eact = create_adjustment_action( "FixationAction",
                                                               _("Fixation"), _("Fixation:"),
                                                               _("Angle behavior (0 = nib always perpendicular to stroke direction, 100 = fixed angle)"),
                                                               "/tools/calligraphic/flatness", 90,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               0.0, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_ddc_flatness_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_ddc_flatness_value_changed, nullptr /*unit tracker*/, 1, 0);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
         }
 
         {
         /* Cap Rounding */
-            gchar const* labels[] = {_("(blunt caps, default)"), _("(slightly bulging)"), 0, 0, _("(approximately round)"), _("(long protruding caps)")};
+            gchar const* labels[] = {_("(blunt caps, default)"), _("(slightly bulging)"), nullptr, nullptr, _("(approximately round)"), _("(long protruding caps)")};
         gdouble values[] = {0, 0.3, 0.5, 1.0, 1.4, 5.0};
         // TRANSLATORS: "cap" means "end" (both start and finish) here
         EgeAdjustmentAction* eact = create_adjustment_action( "CapRoundingAction",
                                                               _("Cap rounding"), _("Caps:"),
                                                               _("Increase to make caps at the ends of strokes protrude more (0 = no caps, 1 = round caps)"),
                                                               "/tools/calligraphic/cap_rounding", 0.0,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               0.0, 5.0, 0.01, 0.1,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_ddc_cap_rounding_value_changed, NULL /*unit tracker*/, 0.01, 2 );
+                                                              sp_ddc_cap_rounding_value_changed, nullptr /*unit tracker*/, 0.01, 2 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
         }
 
         {
         /* Tremor */
-            gchar const* labels[] = {_("(smooth line)"), _("(slight tremor)"), _("(noticeable tremor)"), 0, 0, _("(maximum tremor)")};
+            gchar const* labels[] = {_("(smooth line)"), _("(slight tremor)"), _("(noticeable tremor)"), nullptr, nullptr, _("(maximum tremor)")};
         gdouble values[] = {0, 10, 20, 40, 60, 100};
         EgeAdjustmentAction* eact = create_adjustment_action( "TremorAction",
                                                               _("Stroke Tremor"), _("Tremor:"),
                                                               _("Increase to make strokes rugged and trembling"),
                                                               "/tools/calligraphic/tremor", 0.0,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               0.0, 100, 1, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_ddc_tremor_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_ddc_tremor_value_changed, nullptr /*unit tracker*/, 1, 0);
 
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
@@ -497,16 +497,16 @@ void sp_calligraphy_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
 
         {
         /* Wiggle */
-        gchar const* labels[] = {_("(no wiggle)"), _("(slight deviation)"), 0, 0, _("(wild waves and curls)")};
+        gchar const* labels[] = {_("(no wiggle)"), _("(slight deviation)"), nullptr, nullptr, _("(wild waves and curls)")};
         gdouble values[] = {0, 20, 40, 60, 100};
         EgeAdjustmentAction* eact = create_adjustment_action( "WiggleAction",
                                                               _("Pen Wiggle"), _("Wiggle:"),
                                                               _("Increase to make the pen waver and wiggle"),
                                                               "/tools/calligraphic/wiggle", 0.0,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               0.0, 100, 1, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_ddc_wiggle_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_ddc_wiggle_value_changed, nullptr /*unit tracker*/, 1, 0);
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -514,16 +514,16 @@ void sp_calligraphy_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
 
         {
         /* Mass */
-            gchar const* labels[] = {_("(no inertia)"), _("(slight smoothing, default)"), _("(noticeable lagging)"), 0, 0, _("(maximum inertia)")};
+            gchar const* labels[] = {_("(no inertia)"), _("(slight smoothing, default)"), _("(noticeable lagging)"), nullptr, nullptr, _("(maximum inertia)")};
         gdouble values[] = {0.0, 2, 10, 20, 50, 100};
         EgeAdjustmentAction* eact = create_adjustment_action( "MassAction",
                                                               _("Pen Mass"), _("Mass:"),
                                                               _("Increase to make the pen drag behind, as if slowed by inertia"),
                                                               "/tools/calligraphic/mass", 2.0,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               0.0, 100, 1, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_ddc_mass_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_ddc_mass_value_changed, nullptr /*unit tracker*/, 1, 0);
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
diff --git a/src/ui/toolbar/connector-toolbar.cpp b/src/ui/toolbar/connector-toolbar.cpp
index 2709c700e..42bf965b7 100644
--- a/src/ui/toolbar/connector-toolbar.cpp
+++ b/src/ui/toolbar/connector-toolbar.cpp
@@ -105,7 +105,7 @@ static void sp_connector_orthogonal_toggled( GtkToggleAction* act, GObject *tbl
 
         if (Inkscape::UI::Tools::cc_item_is_connector(item)) {
             item->setAttribute( "inkscape:connector-type",
-                    value, NULL);
+                    value, nullptr);
             item->avoidRef->handleSettingChange();
             modmade = true;
         }
@@ -152,7 +152,7 @@ static void connector_curvature_changed(GtkAdjustment *adj, GObject* tbl)
 
         if (Inkscape::UI::Tools::cc_item_is_connector(item)) {
             item->setAttribute( "inkscape:connector-curvature",
-                    value, NULL);
+                    value, nullptr);
             item->avoidRef->handleSettingChange();
             modmade = true;
         }
@@ -282,11 +282,11 @@ static void connector_tb_event_attr_changed(Inkscape::XML::Node *repr,
 }
 
 static Inkscape::XML::NodeEventVector connector_tb_repr_events = {
-    NULL, /* child_added */
-    NULL, /* child_removed */
+    nullptr, /* child_added */
+    nullptr, /* child_removed */
     connector_tb_event_attr_changed,
-    NULL, /* content_changed */
-    NULL  /* order_changed */
+    nullptr, /* content_changed */
+    nullptr  /* order_changed */
 };
 
 static void sp_connector_toolbox_selection_changed(Inkscape::Selection *selection, GObject *tbl)
@@ -344,7 +344,7 @@ void sp_connector_toolbox_prep( SPDesktop *desktop, GtkActionGroup* mainActions,
         g_signal_connect_after( G_OBJECT(act), "toggled", G_CALLBACK(sp_connector_orthogonal_toggled), holder );
     }
 
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
     // Curvature spinbox
     eact = create_adjustment_action( "ConnectorCurvatureAction",
                                     _("Connector Curvature"), _("Curvature:"),
@@ -352,8 +352,8 @@ void sp_connector_toolbox_prep( SPDesktop *desktop, GtkActionGroup* mainActions,
                                     "/tools/connector/curvature", defaultConnCurvature,
                                     GTK_WIDGET(desktop->canvas), holder, TRUE, "inkscape:connector-curvature",
                                     0, 100, 1.0, 10.0,
-                                    0, 0, 0,
-                                    connector_curvature_changed, NULL /*unit tracker*/, 1, 0 );
+                                    nullptr, nullptr, 0,
+                                    connector_curvature_changed, nullptr /*unit tracker*/, 1, 0 );
     gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
 
     // Spacing spinbox
@@ -363,8 +363,8 @@ void sp_connector_toolbox_prep( SPDesktop *desktop, GtkActionGroup* mainActions,
                                     "/tools/connector/spacing", defaultConnSpacing,
                                     GTK_WIDGET(desktop->canvas), holder, TRUE, "inkscape:connector-spacing",
                                     0, 100, 1.0, 10.0,
-                                    0, 0, 0,
-                                    connector_spacing_changed, NULL /*unit tracker*/, 1, 0 );
+                                    nullptr, nullptr, 0,
+                                    connector_spacing_changed, nullptr /*unit tracker*/, 1, 0 );
     gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
 
     // Graph (connector network) layout
@@ -385,8 +385,8 @@ void sp_connector_toolbox_prep( SPDesktop *desktop, GtkActionGroup* mainActions,
                                      "/tools/connector/length", 100,
                                      GTK_WIDGET(desktop->canvas), holder, TRUE, "inkscape:connector-length",
                                      10, 1000, 10.0, 100.0,
-                                     0, 0, 0,
-                                     connector_length_changed, NULL /*unit tracker*/, 1, 0 );
+                                     nullptr, nullptr, 0,
+                                     connector_length_changed, nullptr /*unit tracker*/, 1, 0 );
     gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
 
 
@@ -425,7 +425,7 @@ void sp_connector_toolbox_prep( SPDesktop *desktop, GtkActionGroup* mainActions,
     // Code to watch for changes to the connector-spacing attribute in
     // the XML.
     Inkscape::XML::Node *repr = desktop->namedview->getRepr();
-    g_assert(repr != NULL);
+    g_assert(repr != nullptr);
 
     purge_repr_listener( holder, holder );
 
diff --git a/src/ui/toolbar/dropper-toolbar.cpp b/src/ui/toolbar/dropper-toolbar.cpp
index ba3c9037c..b9d21be1b 100644
--- a/src/ui/toolbar/dropper-toolbar.cpp
+++ b/src/ui/toolbar/dropper-toolbar.cpp
@@ -80,7 +80,7 @@ void sp_dropper_toolbox_prep(SPDesktop * /*desktop*/, GtkActionGroup* mainAction
     gint pickAlpha = prefs->getInt( "/tools/dropper/pick", 1 );
 
     {
-        EgeOutputAction* act = ege_output_action_new( "DropperOpacityAction", _("Opacity:"), "", 0 );
+        EgeOutputAction* act = ege_output_action_new( "DropperOpacityAction", _("Opacity:"), "", nullptr );
         ege_output_action_set_use_markup( act, TRUE );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
     }
@@ -89,7 +89,7 @@ void sp_dropper_toolbox_prep(SPDesktop * /*desktop*/, GtkActionGroup* mainAction
         InkToggleAction* act = ink_toggle_action_new( "DropperPickAlphaAction",
                                                       _("Pick opacity"),
                                                       _("Pick both the color and the alpha (transparency) under cursor; otherwise, pick only the visible color premultiplied by alpha"),
-                                                      NULL,
+                                                      nullptr,
                                                       GTK_ICON_SIZE_MENU );
         g_object_set( act, "short_label", _("Pick"), NULL );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
@@ -102,7 +102,7 @@ void sp_dropper_toolbox_prep(SPDesktop * /*desktop*/, GtkActionGroup* mainAction
         InkToggleAction* act = ink_toggle_action_new( "DropperSetAlphaAction",
                                                       _("Assign opacity"),
                                                       _("If alpha was picked, assign it to selection as fill or stroke transparency"),
-                                                      NULL,
+                                                      nullptr,
                                                       GTK_ICON_SIZE_MENU );
         g_object_set( act, "short_label", _("Assign"), NULL );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
diff --git a/src/ui/toolbar/eraser-toolbar.cpp b/src/ui/toolbar/eraser-toolbar.cpp
index 26ff3a654..ec028a2c8 100644
--- a/src/ui/toolbar/eraser-toolbar.cpp
+++ b/src/ui/toolbar/eraser-toolbar.cpp
@@ -183,7 +183,7 @@ void sp_eraser_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
 
     /* Width */
     {
-        gchar const* labels[] = {_("(no width)"),_("(hairline)"), 0, 0, 0, _("(default)"), 0, 0, 0, 0, _("(broad stroke)")};
+        gchar const* labels[] = {_("(no width)"),_("(hairline)"), nullptr, nullptr, nullptr, _("(default)"), nullptr, nullptr, nullptr, nullptr, _("(broad stroke)")};
         gdouble values[] = {0, 1, 3, 5, 10, 15, 20, 30, 50, 75, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "EraserWidthAction",
                                                               _("Pen Width"), _("Width:"),
@@ -192,7 +192,7 @@ void sp_eraser_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
                                                               GTK_WIDGET(desktop->canvas), holder, TRUE, "altx-eraser",
                                                               0, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_erc_width_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_erc_width_value_changed, nullptr /*unit tracker*/, 1, 0);
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         g_object_set_data( holder, "width", eact );
@@ -216,16 +216,16 @@ void sp_eraser_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
 
     /* Thinning */
     {
-        gchar const* labels[] = {_("(speed blows up stroke)"), 0, 0, _("(slight widening)"), _("(constant width)"), _("(slight thinning, default)"), 0, 0, _("(speed deflates stroke)")};
+        gchar const* labels[] = {_("(speed blows up stroke)"), nullptr, nullptr, _("(slight widening)"), _("(constant width)"), _("(slight thinning, default)"), nullptr, nullptr, _("(speed deflates stroke)")};
         gdouble values[] = {-100, -40, -20, -10, 0, 10, 20, 40, 100};
         EgeAdjustmentAction* eact = create_adjustment_action( "EraserThinningAction",
                                                               _("Eraser Stroke Thinning"), _("Thinning:"),
                                                               _("How much velocity thins the stroke (> 0 makes fast strokes thinner, < 0 makes them broader, 0 makes width independent of velocity)"),
                                                               "/tools/eraser/thinning", 10,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               -100, 100, 1, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_erc_velthin_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_erc_velthin_value_changed, nullptr /*unit tracker*/, 1, 0);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         g_object_set_data( holder, "thinning", eact );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -234,17 +234,17 @@ void sp_eraser_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
 
     /* Cap Rounding */
     {
-            gchar const* labels[] = {_("(blunt caps, default)"), _("(slightly bulging)"), 0, 0, _("(approximately round)"), _("(long protruding caps)")};
+            gchar const* labels[] = {_("(blunt caps, default)"), _("(slightly bulging)"), nullptr, nullptr, _("(approximately round)"), _("(long protruding caps)")};
         gdouble values[] = {0, 0.3, 0.5, 1.0, 1.4, 5.0};
         // TRANSLATORS: "cap" means "end" (both start and finish) here
         EgeAdjustmentAction* eact = create_adjustment_action( "EraserCapRoundingAction",
                                                               _("Eraser Cap rounding"), _("Caps:"),
                                                               _("Increase to make caps at the ends of strokes protrude more (0 = no caps, 1 = round caps)"),
                                                               "/tools/eraser/cap_rounding", 0.0,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               0.0, 5.0, 0.01, 0.1,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_erc_cap_rounding_value_changed, NULL /*unit tracker*/, 0.01, 2 );
+                                                              sp_erc_cap_rounding_value_changed, nullptr /*unit tracker*/, 0.01, 2 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         g_object_set_data( holder, "cap_rounding", eact );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -253,16 +253,16 @@ void sp_eraser_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
 
     /* Tremor */
     {
-        gchar const* labels[] = {_("(smooth line)"), _("(slight tremor)"), _("(noticeable tremor)"), 0, 0, _("(maximum tremor)")};
+        gchar const* labels[] = {_("(smooth line)"), _("(slight tremor)"), _("(noticeable tremor)"), nullptr, nullptr, _("(maximum tremor)")};
         gdouble values[] = {0, 10, 20, 40, 60, 100};
         EgeAdjustmentAction* eact = create_adjustment_action( "EraserTremorAction",
                                                               _("EraserStroke Tremor"), _("Tremor:"),
                                                               _("Increase to make strokes rugged and trembling"),
                                                               "/tools/eraser/tremor", 0.0,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               0.0, 100, 1, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_erc_tremor_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_erc_tremor_value_changed, nullptr /*unit tracker*/, 1, 0);
 
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         g_object_set_data( holder, "tremor", eact );
@@ -273,16 +273,16 @@ void sp_eraser_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
 
     /* Mass */
     {
-            gchar const* labels[] = {_("(no inertia)"), _("(slight smoothing, default)"), _("(noticeable lagging)"), 0, 0, _("(maximum inertia)")};
+            gchar const* labels[] = {_("(no inertia)"), _("(slight smoothing, default)"), _("(noticeable lagging)"), nullptr, nullptr, _("(maximum inertia)")};
         gdouble values[] = {0.0, 2, 10, 20, 50, 100};
         EgeAdjustmentAction* eact = create_adjustment_action( "EraserMassAction",
                                                               _("Eraser Mass"), _("Mass:"),
                                                               _("Increase to make the eraser drag behind, as if slowed by inertia"),
                                                               "/tools/eraser/mass", 10.0,
-                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                                              GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                                               0.0, 100, 1, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_erc_mass_value_changed, NULL /*unit tracker*/, 1, 0);
+                                                              sp_erc_mass_value_changed, nullptr /*unit tracker*/, 1, 0);
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         g_object_set_data( holder, "mass", eact );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
diff --git a/src/ui/toolbar/gradient-toolbar.cpp b/src/ui/toolbar/gradient-toolbar.cpp
index 38724aca4..b6677e221 100644
--- a/src/ui/toolbar/gradient-toolbar.cpp
+++ b/src/ui/toolbar/gradient-toolbar.cpp
@@ -157,7 +157,7 @@ int gr_vector_list(Glib::RefPtr<Gtk::ListStore> store, SPDesktop *desktop,
 
     } else {
 
-        if (gr_selected == NULL) {
+        if (gr_selected == nullptr) {
             row = *(store->append());
             row[columns.col_label    ] = _("No gradient");
             row[columns.col_tooltip  ] = "";
@@ -210,13 +210,13 @@ int gr_vector_list(Glib::RefPtr<Gtk::ListStore> store, SPDesktop *desktop,
  */
 void gr_get_dt_selected_gradient(Inkscape::Selection *selection, SPGradient *&gr_selected)
 {
-    SPGradient *gradient = 0;
+    SPGradient *gradient = nullptr;
 
     auto itemlist= selection->items();
     for(auto i=itemlist.begin();i!=itemlist.end();++i){
         SPItem *item = *i;// get the items gradient, not the getVector() version
          SPStyle *style = item->style;
-         SPPaintServer *server = 0;
+         SPPaintServer *server = nullptr;
 
          if (style && (style->fill.isPaintserver())) {
              server = item->style->getFillPaintServer();
@@ -231,7 +231,7 @@ void gr_get_dt_selected_gradient(Inkscape::Selection *selection, SPGradient *&gr
     }
 
     if (gradient && gradient->isSolid()) {
-        gradient = 0;
+        gradient = nullptr;
     }
 
     if (gradient) {
@@ -258,7 +258,7 @@ void gr_read_selection( Inkscape::Selection *selection,
             SPGradientSpread spread = sp_item_gradient_get_spread(draggable->item, draggable->fill_or_stroke);
 
             if (gradient && gradient->isSolid()) {
-                gradient = 0;
+                gradient = nullptr;
             }
 
             if (gradient && (gradient != gr_selected)) {
@@ -292,7 +292,7 @@ void gr_read_selection( Inkscape::Selection *selection,
                 SPGradientSpread spread = SP_GRADIENT(server)->fetchSpread();
 
                 if (gradient && gradient->isSolid()) {
-                    gradient = 0;
+                    gradient = nullptr;
                 }
 
                 if (gradient && (gradient != gr_selected)) {
@@ -318,7 +318,7 @@ void gr_read_selection( Inkscape::Selection *selection,
                 SPGradientSpread spread = SP_GRADIENT(server)->fetchSpread();
 
                 if (gradient && gradient->isSolid()) {
-                    gradient = 0;
+                    gradient = nullptr;
                 }
 
                 if (gradient && (gradient != gr_selected)) {
@@ -394,7 +394,7 @@ static void gr_remove_stop(GtkWidget * /*button*/, GObject *data)
     }
 
     ToolBase *ev = desktop->getEventContext();
-    GrDrag *drag = NULL;
+    GrDrag *drag = nullptr;
     if (ev) {
         drag = ev->get_drag();
     }
@@ -450,18 +450,18 @@ static void gr_stop_set_offset (GObject *data)
 
     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;
@@ -739,7 +739,7 @@ static void gr_gradient_changed( GObject *data, int active )
         Inkscape::Selection *selection = desktop->getSelection();
         ToolBase *ev = desktop->getEventContext();
 
-        gr_apply_gradient(selection, ev ? ev->get_drag() : NULL, gr);
+        gr_apply_gradient(selection, ev ? ev->get_drag() : nullptr, gr);
 
         DocumentUndo::done(desktop->getDocument(), SP_VERB_CONTEXT_GRADIENT,
                    _("Assign gradient to object"));
@@ -761,7 +761,7 @@ static void gr_spread_changed( GObject *data, int active )
 
     SPDesktop *desktop = static_cast<SPDesktop *>(g_object_get_data(data, "desktop"));
     Inkscape::Selection *selection = desktop->getSelection();
-    SPGradient *gradient = 0;
+    SPGradient *gradient = nullptr;
     gr_get_dt_selected_gradient(selection, gradient);
 
     if (gradient) {
@@ -1047,15 +1047,15 @@ void sp_gradient_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions,
 
     /* Offset */
     {
-        EgeAdjustmentAction* eact = 0;
+        EgeAdjustmentAction* eact = nullptr;
         eact = create_adjustment_action( "GradientEditOffsetAction",
                                          _("Offset"), C_("Gradient", "Offset:"), _("Offset of selected stop"),
                                          "/tools/gradient/stopoffset", 0,
-                                         GTK_WIDGET(desktop->canvas), data, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), data, FALSE, nullptr,
                                          0.0, 1.0, 0.01, 0.1,
-                                         0, 0, 0,
+                                         nullptr, nullptr, 0,
                                          gr_stop_offset_adjustment_changed,
-                                         NULL /*unit tracker*/,
+                                         nullptr /*unit tracker*/,
                                          0.01, 2, 1.0);
 
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
@@ -1149,12 +1149,12 @@ static void gr_tb_selection_changed(Inkscape::Selection * /*selection*/, GObject
     if (selection) {
 
         ToolBase *ev = desktop->getEventContext();
-        GrDrag *drag = NULL;
+        GrDrag *drag = nullptr;
         if (ev) {
             drag = ev->get_drag();
         }
 
-        SPGradient *gr_selected = 0;
+        SPGradient *gr_selected = nullptr;
         SPGradientSpread spr_selected = SP_GRADIENT_SPREAD_UNDEFINED;
         bool gr_multi = false;
         bool spr_multi = false;
@@ -1188,7 +1188,7 @@ static void gr_tb_selection_changed(Inkscape::Selection * /*selection*/, GObject
         gtk_action_set_sensitive(GTK_ACTION(del), (gr_selected && !gr_multi && drag && !drag->selected.empty()));
 
         InkAction *reverse = (InkAction *) g_object_get_data(data, "gradient_stops_reverse_action");
-        gtk_action_set_sensitive(GTK_ACTION(reverse), (gr_selected!= NULL));
+        gtk_action_set_sensitive(GTK_ACTION(reverse), (gr_selected!= nullptr));
 
         InkSelectOneAction *stops_action = (InkSelectOneAction *) g_object_get_data(data, "gradient_stop_action");
         stops_action->set_sensitive( gr_selected && !gr_multi);
@@ -1207,17 +1207,17 @@ static void gr_tb_selection_modified(Inkscape::Selection *selection, guint /*fla
 
 static void gr_drag_selection_changed(gpointer /*dragger*/, GObject* data)
 {
-    gr_tb_selection_changed(NULL, data);
+    gr_tb_selection_changed(nullptr, data);
 }
 
 static void gr_defs_release(SPObject * /*defs*/, GObject* data)
 {
-    gr_tb_selection_changed(NULL, data);
+    gr_tb_selection_changed(nullptr, data);
 }
 
 static void gr_defs_modified(SPObject * /*defs*/, guint /*flags*/, GObject* data)
 {
-    gr_tb_selection_changed(NULL, data);
+    gr_tb_selection_changed(nullptr, data);
 }
 
 // lp:1327267
diff --git a/src/ui/toolbar/lpe-toolbar.cpp b/src/ui/toolbar/lpe-toolbar.cpp
index bed5ed4bf..b42c1ae0c 100644
--- a/src/ui/toolbar/lpe-toolbar.cpp
+++ b/src/ui/toolbar/lpe-toolbar.cpp
@@ -131,14 +131,14 @@ static void sp_lpetool_toolbox_sel_changed(Inkscape::Selection *selection, GObje
             act->set_sensitive(true);
             act->set_active( lpels->end_type.get_value() );
         } else {
-            g_object_set_data(tbl, "currentlpe", NULL);
-            g_object_set_data(tbl, "currentlpeitem", NULL);
+            g_object_set_data(tbl, "currentlpe", nullptr);
+            g_object_set_data(tbl, "currentlpeitem", nullptr);
             act->set_sensitive(false);
         }
 
     } else {
-        g_object_set_data(tbl, "currentlpe", NULL);
-        g_object_set_data(tbl, "currentlpeitem", NULL);
+        g_object_set_data(tbl, "currentlpe", nullptr);
+        g_object_set_data(tbl, "currentlpeitem", nullptr);
         act->set_sensitive(false);
     }
 }
@@ -180,7 +180,7 @@ static void lpetool_unit_changed(GObject* tbl, int /* NotUsed */)
 {
     UnitTracker* tracker = reinterpret_cast<UnitTracker*>(g_object_get_data(tbl, "tracker"));
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
     prefs->setString("/tools/lpetool/unit", unit->abbr);
 
@@ -247,7 +247,7 @@ static void lpetool_open_lpe_dialog(GtkToggleAction *act, gpointer data)
     SPDesktop *desktop = static_cast<SPDesktop *>(data);
 
     if (tools_isactive(desktop, TOOLS_LPETOOL)) {
-        sp_action_perform(Inkscape::Verb::get(SP_VERB_DIALOG_LIVE_PATH_EFFECT)->get_action(Inkscape::ActionContext(desktop)), NULL);
+        sp_action_perform(Inkscape::Verb::get(SP_VERB_DIALOG_LIVE_PATH_EFFECT)->get_action(Inkscape::ActionContext(desktop)), nullptr);
     }
     gtk_toggle_action_set_active(act, false);
 }
@@ -260,7 +260,7 @@ void sp_lpetool_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GO
     tracker->setActiveUnit(desktop->getNamedView()->display_units);
     g_object_set_data(holder, "tracker", tracker);
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
 
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
     prefs->setString("/tools/lpetool/unit", unit->abbr);
diff --git a/src/ui/toolbar/measure-toolbar.cpp b/src/ui/toolbar/measure-toolbar.cpp
index ec9cffe25..07eefa330 100644
--- a/src/ui/toolbar/measure-toolbar.cpp
+++ b/src/ui/toolbar/measure-toolbar.cpp
@@ -63,7 +63,7 @@ using Inkscape::UI::Tools::MeasureTool;
  * Will go away during tool refactoring. */
 static MeasureTool *get_measure_tool()
 {
-    MeasureTool *tool = 0;
+    MeasureTool *tool = nullptr;
     if (SP_ACTIVE_DESKTOP ) {
         Inkscape::UI::Tools::ToolBase *ec = SP_ACTIVE_DESKTOP->event_context;
         if (SP_IS_MEASURE_CONTEXT(ec)) {
@@ -286,7 +286,7 @@ void sp_measure_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions, G
     
     g_object_set_data( holder, "tracker", tracker );
 
-    EgeAdjustmentAction *eact = 0;
+    EgeAdjustmentAction *eact = nullptr;
     GtkIconSize secondarySize = ToolboxFactory::prefToSize("/toolbox/secondary", 1);
 
     /* Font Size */
@@ -295,16 +295,16 @@ void sp_measure_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions, G
                                          _("Font Size"), _("Font Size:"),
                                          _("The font size to be used in the measurement labels"),
                                          "/tools/measure/fontsize", 10.0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          1.0, 36.0, 1.0, 4.0,
-                                         0, 0, 0,
-                                         sp_measure_fontsize_value_changed, NULL, 0 , 2);
+                                         nullptr, nullptr, 0,
+                                         sp_measure_fontsize_value_changed, nullptr, 0 , 2);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact));
     }
 
     /* units label */
     {
-        EgeOutputAction* act = ege_output_action_new( "measure_units_label", _("Units:"), _("The units to be used for the measurements"), 0 );
+        EgeOutputAction* act = ege_output_action_new( "measure_units_label", _("Units:"), _("The units to be used for the measurements"), nullptr );
         ege_output_action_set_use_markup( act, TRUE );
         g_object_set( act, "visible-overflown", FALSE, NULL );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
@@ -323,10 +323,10 @@ void sp_measure_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions, G
                                          _("Precision"), _("Precision:"),
                                          _("Decimal precision of measure"),
                                          "/tools/measure/precision", 2,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0, 10, 1, 0,
-                                         0, 0, 0,
-                                         sp_measure_precision_value_changed, NULL, 0 ,0);
+                                         nullptr, nullptr, 0,
+                                         sp_measure_precision_value_changed, nullptr, 0 ,0);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact));
     }
 
@@ -336,10 +336,10 @@ void sp_measure_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions, G
                                          _("Scale %"), _("Scale %:"),
                                          _("Scale the results"),
                                          "/tools/measure/scale", 100.0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0.0, 90000.0, 1.0, 4.0,
-                                         0, 0, 0,
-                                         sp_measure_scale_value_changed, NULL, 0 , 3);
+                                         nullptr, nullptr, 0,
+                                         sp_measure_scale_value_changed, nullptr, 0 , 3);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
     }
 
@@ -349,10 +349,10 @@ void sp_measure_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions, G
                                          _("Offset"), _("Offset:"),
                                          _("Mark dimension offset"),
                                          "/tools/measure/offset", 5.0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0.0, 90000.0, 1.0, 4.0,
-                                         0, 0, 0,
-                                         sp_measure_offset_value_changed, NULL, 0 , 2);
+                                         nullptr, nullptr, 0,
+                                         sp_measure_offset_value_changed, nullptr, 0 , 2);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
     }
 
diff --git a/src/ui/toolbar/mesh-toolbar.cpp b/src/ui/toolbar/mesh-toolbar.cpp
index fdeb736e6..80f817ae3 100644
--- a/src/ui/toolbar/mesh-toolbar.cpp
+++ b/src/ui/toolbar/mesh-toolbar.cpp
@@ -112,7 +112,7 @@ void ms_read_selection( Inkscape::Selection *selection,
                         SPMeshType &ms_type,
                         bool &ms_type_multi )
 {
-    ms_selected = NULL;
+    ms_selected = nullptr;
     ms_selected_multi = false;
     ms_type = SP_MESH_TYPE_COONS;
     ms_type_multi = false;
@@ -162,7 +162,7 @@ static void ms_tb_selection_changed(Inkscape::Selection * /*selection*/, gpointe
         //     // Hide/show handles?
         // }
 
-        SPMeshGradient *ms_selected = 0;
+        SPMeshGradient *ms_selected = nullptr;
         SPMeshType ms_type = SP_MESH_TYPE_COONS;
         bool ms_selected_multi = false;
         bool ms_type_multi = false; 
@@ -187,18 +187,18 @@ static void ms_tb_selection_modified(Inkscape::Selection *selection, guint /*fla
 
 static void ms_drag_selection_changed(gpointer /*dragger*/, gpointer data)
 {
-    ms_tb_selection_changed(NULL, data);
+    ms_tb_selection_changed(nullptr, data);
 
 }
 
 static void ms_defs_release(SPObject * /*defs*/, GObject *widget)
 {
-    ms_tb_selection_changed(NULL, widget);
+    ms_tb_selection_changed(nullptr, widget);
 }
 
 static void ms_defs_modified(SPObject * /*defs*/, guint /*flags*/, GObject *widget)
 {
-    ms_tb_selection_changed(NULL, widget);
+    ms_tb_selection_changed(nullptr, widget);
 }
 
 /*
@@ -279,7 +279,7 @@ static void ms_type_changed( GObject *tbl, int mode )
  * Will go away during tool refactoring. */
 static MeshTool *get_mesh_tool()
 {
-    MeshTool *tool = 0;
+    MeshTool *tool = nullptr;
     if (SP_ACTIVE_DESKTOP ) {
         Inkscape::UI::Tools::ToolBase *ec = SP_ACTIVE_DESKTOP->event_context;
         if (SP_IS_MESH_CONTEXT(ec)) {
@@ -338,7 +338,7 @@ static void ms_toggle_fill_stroke(InkToggleAction * /*act*/, gpointer data)
         drag->updateDraggers();
         drag->updateLines();
         drag->updateLevels();
-        ms_tb_selection_changed(NULL, data); // Need to update Type widget
+        ms_tb_selection_changed(nullptr, data); // Need to update Type widget
     }
 }
 
@@ -367,7 +367,7 @@ void sp_mesh_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions, GObj
 {
     GtkIconSize secondarySize = ToolboxFactory::prefToSize("/toolbox/secondary", 1);
 
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
 
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
@@ -449,15 +449,15 @@ void sp_mesh_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions, GObj
 
     /* Number of mesh rows */
     {
-        gchar const** labels = NULL;
+        gchar const** labels = nullptr;
         gdouble values[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
         eact = create_adjustment_action( "MeshRowAction",
                                          _("Rows"), _("Rows:"), _("Number of rows in new mesh"),
                                          "/tools/mesh/mesh_rows", 1,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          1, 20, 1, 1,
                                          labels, values, 0,
-                                         ms_row_changed, NULL /*unit tracker*/,
+                                         ms_row_changed, nullptr /*unit tracker*/,
                                          1.0, 0 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -465,15 +465,15 @@ void sp_mesh_toolbox_prep(SPDesktop * desktop, GtkActionGroup* mainActions, GObj
 
     /* Number of mesh columns */
     {
-        gchar const** labels = NULL;
+        gchar const** labels = nullptr;
         gdouble values[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
         eact = create_adjustment_action( "MeshColumnAction",
                                          _("Columns"), _("Columns:"), _("Number of columns in new mesh"),
                                          "/tools/mesh/mesh_cols", 1,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          1, 20, 1, 1,
                                          labels, values, 0,
-                                         ms_col_changed, NULL /*unit tracker*/,
+                                         ms_col_changed, nullptr /*unit tracker*/,
                                          1.0, 0 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
diff --git a/src/ui/toolbar/node-toolbar.cpp b/src/ui/toolbar/node-toolbar.cpp
index a5e6a68ad..2cb9fb364 100644
--- a/src/ui/toolbar/node-toolbar.cpp
+++ b/src/ui/toolbar/node-toolbar.cpp
@@ -70,7 +70,7 @@ using Inkscape::UI::Tools::NodeTool;
  * Will go away during tool refactoring. */
 static NodeTool *get_node_tool()
 {
-    NodeTool *tool = 0;
+    NodeTool *tool = nullptr;
     if (SP_ACTIVE_DESKTOP ) {
         Inkscape::UI::Tools::ToolBase *ec = SP_ACTIVE_DESKTOP->event_context;
         if (INK_IS_NODE_TOOL(ec)) {
@@ -231,7 +231,7 @@ static void sp_node_toolbox_coord_changed(gpointer /*shape_editor*/, GObject *tb
         return;
     }
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
 
     NodeTool *nt = get_node_tool();
     if (!nt || !(nt->_selected_nodes) ||nt->_selected_nodes->empty()) {
@@ -348,10 +348,10 @@ void sp_node_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
         g_object_set( INK_ACTION(inky), "short_label", _("Insert"), NULL );
         g_signal_connect_after( G_OBJECT(inky), "activate", G_CALLBACK(sp_node_path_edit_add), 0 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(inky) );
-        GtkToolItem *menu_tool_button = gtk_menu_tool_button_new (NULL, NULL);
+        GtkToolItem *menu_tool_button = gtk_menu_tool_button_new (nullptr, nullptr);
         gtk_activatable_set_related_action (GTK_ACTIVATABLE (menu_tool_button), GTK_ACTION(inky));
         // also create dummy menu action:
-        gtk_action_group_add_action( mainActions, gtk_action_new("NodeInsertActionMenu", NULL, NULL, NULL) );
+        gtk_action_group_add_action( mainActions, gtk_action_new("NodeInsertActionMenu", nullptr, nullptr, nullptr) );
     }
 
     {
@@ -577,8 +577,8 @@ void sp_node_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
 
     /* X coord of selected node(s) */
     {
-        EgeAdjustmentAction* eact = 0;
-        gchar const* labels[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+        EgeAdjustmentAction* eact = nullptr;
+        gchar const* labels[] = {nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {1, 2, 3, 5, 10, 20, 50, 100, 200, 500};
         eact = create_adjustment_action( "NodeXAction",
                                          _("X coordinate:"), _("X:"), _("X coordinate of selected node(s)"),
@@ -594,13 +594,13 @@ void sp_node_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
 
     /* Y coord of selected node(s) */
     {
-        EgeAdjustmentAction* eact = 0;
-        gchar const* labels[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+        EgeAdjustmentAction* eact = nullptr;
+        gchar const* labels[] = {nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {1, 2, 3, 5, 10, 20, 50, 100, 200, 500};
         eact = create_adjustment_action( "NodeYAction",
                                          _("Y coordinate:"), _("Y:"), _("Y coordinate of selected node(s)"),
                                          "/tools/nodes/Ycoord", 0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          -1e6, 1e6, SPIN_STEP, SPIN_PAGE_STEP,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_node_path_y_value_changed, tracker );
diff --git a/src/ui/toolbar/paintbucket-toolbar.cpp b/src/ui/toolbar/paintbucket-toolbar.cpp
index 280cf0eb1..c46a007b6 100644
--- a/src/ui/toolbar/paintbucket-toolbar.cpp
+++ b/src/ui/toolbar/paintbucket-toolbar.cpp
@@ -83,7 +83,7 @@ static void paintbucket_offset_changed(GtkAdjustment *adj, GObject *tbl)
     // unit and it'll be correctly handled on load.
     prefs->setDouble("/tools/paintbucket/offset", (gdouble)gtk_adjustment_get_value(adj));
 
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
     prefs->setString("/tools/paintbucket/offsetunits", unit->abbr);
 }
 
@@ -117,7 +117,7 @@ static void paintbucket_defaults(GtkWidget *, GObject *tbl)
 
 void sp_paintbucket_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject* holder)
 {
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
     // Channel
@@ -164,8 +164,8 @@ void sp_paintbucket_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
             _("The maximum allowed difference between the clicked pixel and the neighboring pixels to be counted in the fill"),
             "/tools/paintbucket/threshold", 5, GTK_WIDGET(desktop->canvas), holder, TRUE,
             "inkscape:paintbucket-threshold", 0, 100.0, 1.0, 10.0,
-            0, 0, 0,
-            paintbucket_threshold_changed, NULL /*unit tracker*/, 1, 0 );
+            nullptr, nullptr, 0,
+            paintbucket_threshold_changed, nullptr /*unit tracker*/, 1, 0 );
 
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
@@ -193,7 +193,7 @@ void sp_paintbucket_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions
             _("The amount to grow (positive) or shrink (negative) the created fill path"),
             "/tools/paintbucket/offset", 0, GTK_WIDGET(desktop->canvas), holder, TRUE,
             "inkscape:paintbucket-offset", -1e4, 1e4, 0.1, 0.5,
-            0, 0, 0,
+            nullptr, nullptr, 0,
             paintbucket_offset_changed, tracker, 1, 2);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
     }
diff --git a/src/ui/toolbar/pencil-toolbar.cpp b/src/ui/toolbar/pencil-toolbar.cpp
index 6391af394..cf4ba5a5d 100644
--- a/src/ui/toolbar/pencil-toolbar.cpp
+++ b/src/ui/toolbar/pencil-toolbar.cpp
@@ -304,7 +304,7 @@ static void sp_flatten_spiro_bspline(GtkWidget * /*widget*/, GObject *obj)
 {
     SPDesktop *desktop = static_cast<SPDesktop *>(g_object_get_data(obj, "desktop"));
     auto selected = desktop->getSelection()->items();
-    SPLPEItem* lpeitem = NULL;
+    SPLPEItem* lpeitem = nullptr;
     for (auto it(selected.begin()); it != selected.end(); ++it){
         lpeitem = dynamic_cast<SPLPEItem*>(*it);
         if (lpeitem && lpeitem->hasPathEffect()){
@@ -347,7 +347,7 @@ static void sp_simplify_flatten(GtkWidget * /*widget*/, GObject *obj)
 {
     SPDesktop *desktop = static_cast<SPDesktop *>(g_object_get_data(obj, "desktop"));
     auto selected = desktop->getSelection()->items();
-    SPLPEItem* lpeitem = NULL;
+    SPLPEItem* lpeitem = nullptr;
     for (auto it(selected.begin()); it != selected.end(); ++it){
         lpeitem = dynamic_cast<SPLPEItem*>(*it);
         if (lpeitem && lpeitem->hasPathEffect()){
@@ -497,7 +497,7 @@ void sp_pencil_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
 {
     sp_add_freehand_mode_toggle(mainActions, holder, true);
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
 
     
     /* min pressure */
@@ -505,10 +505,10 @@ void sp_pencil_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
         eact = create_adjustment_action( "MinPressureAction",
                                          _("Min pressure"), _("Min:"), _("Min percent of pressure"),
                                          "/tools/freehand/pencil/minpressure", 0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0, 100, 1, 0,
-                                         0, 0, 0,
-                                         sp_minpressure_value_changed, NULL, 0 ,0);
+                                         nullptr, nullptr, 0,
+                                         sp_minpressure_value_changed, nullptr, 0 ,0);
                                          
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         g_object_set_data( holder, "minpressure", eact );
@@ -523,10 +523,10 @@ void sp_pencil_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
         eact = create_adjustment_action( "MaxPressureAction",
                                          _("Max pressure"), _("Max:"), _("Max percent of pressure"),
                                          "/tools/freehand/pencil/maxpressure", 100,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0, 100, 1, 0,
-                                         0, 0, 0,
-                                         sp_maxpressure_value_changed, NULL, 0 ,0);
+                                         nullptr, nullptr, 0,
+                                         sp_maxpressure_value_changed, nullptr, 0 ,0);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         g_object_set_data( holder, "maxpressure", eact );
         if (prefs->getInt("/tools/freehand/pencil/freehand-mode", 0) == 3) {
@@ -556,7 +556,7 @@ void sp_pencil_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
     }
     /* Tolerance */
     {
-        gchar const* labels[] = {_("(many nodes, rough)"), _("(default)"), 0, 0, 0, 0, _("(few nodes, smooth)")};
+        gchar const* labels[] = {_("(many nodes, rough)"), _("(default)"), nullptr, nullptr, nullptr, nullptr, _("(few nodes, smooth)")};
         gdouble values[] = {1, 10, 20, 30, 50, 75, 100};
         eact = create_adjustment_action( "PencilToleranceAction",
                                          _("Smoothing:"), _("Smoothing: "),
@@ -568,7 +568,7 @@ void sp_pencil_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
                                          1, 100.0, 0.5, 1.0,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_pencil_tb_tolerance_value_changed,
-                                         NULL /*unit tracker*/,
+                                         nullptr /*unit tracker*/,
                                          1, 2);
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
diff --git a/src/ui/toolbar/rect-toolbar.cpp b/src/ui/toolbar/rect-toolbar.cpp
index 420c3410e..f52e4dfa1 100644
--- a/src/ui/toolbar/rect-toolbar.cpp
+++ b/src/ui/toolbar/rect-toolbar.cpp
@@ -90,7 +90,7 @@ static void sp_rtb_value_changed(GtkAdjustment *adj, GObject *tbl, gchar const *
 
     UnitTracker* tracker = reinterpret_cast<UnitTracker*>(g_object_get_data( tbl, "tracker" ));
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
 
     if (DocumentUndo::getUndoSensitive(desktop->getDocument())) {
         Inkscape::Preferences *prefs = Inkscape::Preferences::get();
@@ -114,7 +114,7 @@ static void sp_rtb_value_changed(GtkAdjustment *adj, GObject *tbl, gchar const *
             if (gtk_adjustment_get_value(adj) != 0) {
                 (SP_RECT(*i)->*setter)(Quantity::convert(gtk_adjustment_get_value(adj), unit, "px"));
             } else {
-                (*i)->getRepr()->setAttribute(value_name, NULL);
+                (*i)->getRepr()->setAttribute(value_name, nullptr);
             }
             modmade = true;
         }
@@ -154,7 +154,7 @@ static void sp_rtb_height_value_changed(GtkAdjustment *adj, GObject *tbl)
 
 static void sp_rtb_defaults( GtkWidget * /*widget*/, GObject *obj)
 {
-    GtkAdjustment *adj = 0;
+    GtkAdjustment *adj = nullptr;
 
     adj = GTK_ADJUSTMENT( g_object_get_data(obj, "rx") );
     gtk_adjustment_set_value(adj, 0.0);
@@ -190,7 +190,7 @@ static void rect_tb_event_attr_changed(Inkscape::XML::Node * /*repr*/, gchar con
 
     UnitTracker* tracker = reinterpret_cast<UnitTracker*>( g_object_get_data( tbl, "tracker" ) );
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
 
     gpointer item = g_object_get_data( tbl, "item" );
     if (item && SP_IS_RECT(item)) {
@@ -230,11 +230,11 @@ static void rect_tb_event_attr_changed(Inkscape::XML::Node * /*repr*/, gchar con
 
 
 static Inkscape::XML::NodeEventVector rect_tb_repr_events = {
-    NULL, /* child_added */
-    NULL, /* child_removed */
+    nullptr, /* child_added */
+    nullptr, /* child_removed */
     rect_tb_event_attr_changed,
-    NULL, /* content_changed */
-    NULL  /* order_changed */
+    nullptr, /* content_changed */
+    nullptr  /* order_changed */
 };
 
 /**
@@ -243,11 +243,11 @@ static Inkscape::XML::NodeEventVector rect_tb_repr_events = {
 static void sp_rect_toolbox_selection_changed(Inkscape::Selection *selection, GObject *tbl)
 {
     int n_selected = 0;
-    Inkscape::XML::Node *repr = NULL;
-    SPItem *item = NULL;
+    Inkscape::XML::Node *repr = nullptr;
+    SPItem *item = nullptr;
 
     if ( g_object_get_data( tbl, "repr" ) ) {
-        g_object_set_data( tbl, "item", NULL );
+        g_object_set_data( tbl, "item", nullptr );
     }
     purge_repr_listener( tbl, tbl );
 
@@ -300,11 +300,11 @@ static void rect_toolbox_watch_ec(SPDesktop* dt, Inkscape::UI::Tools::ToolBase*
 
 void sp_rect_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject* holder)
 {
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
     GtkIconSize secondarySize = ToolboxFactory::prefToSize("/toolbox/secondary", 1);
 
     {
-        EgeOutputAction* act = ege_output_action_new( "RectStateAction", _("<b>New:</b>"), "", 0 );
+        EgeOutputAction* act = ege_output_action_new( "RectStateAction", _("<b>New:</b>"), "", nullptr );
         ege_output_action_set_use_markup( act, TRUE );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
         g_object_set_data( holder, "mode_action", act );
@@ -319,7 +319,7 @@ void sp_rect_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
 
     /* W */
     {
-        gchar const* labels[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+        gchar const* labels[] = {nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {1, 2, 3, 5, 10, 20, 50, 100, 200, 500};
         eact = create_adjustment_action( "RectWidthAction",
                                          _("Width"), _("W:"), _("Width of rectangle"),
@@ -335,12 +335,12 @@ void sp_rect_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
 
     /* H */
     {
-        gchar const* labels[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+        gchar const* labels[] = {nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {1, 2, 3, 5, 10, 20, 50, 100, 200, 500};
         eact = create_adjustment_action( "RectHeightAction",
                                          _("Height"), _("H:"), _("Height of rectangle"),
                                          "/tools/shapes/rect/height", 0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0, 1e6, SPIN_STEP, SPIN_PAGE_STEP,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_rtb_height_value_changed, tracker);
@@ -351,12 +351,12 @@ void sp_rect_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
 
     /* rx */
     {
-        gchar const* labels[] = {_("not rounded"), 0, 0, 0, 0, 0, 0, 0, 0};
+        gchar const* labels[] = {_("not rounded"), nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {0.5, 1, 2, 3, 5, 10, 20, 50, 100};
         eact = create_adjustment_action( "RadiusXAction",
                                          _("Horizontal radius"), _("Rx:"), _("Horizontal radius of rounded corners"),
                                          "/tools/shapes/rect/rx", 0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0, 1e6, SPIN_STEP, SPIN_PAGE_STEP,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_rtb_rx_value_changed, tracker);
@@ -365,12 +365,12 @@ void sp_rect_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
 
     /* ry */
     {
-        gchar const* labels[] = {_("not rounded"), 0, 0, 0, 0, 0, 0, 0, 0};
+        gchar const* labels[] = {_("not rounded"), nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {0.5, 1, 2, 3, 5, 10, 20, 50, 100};
         eact = create_adjustment_action( "RadiusYAction",
                                          _("Vertical radius"), _("Ry:"), _("Vertical radius of rounded corners"),
                                          "/tools/shapes/rect/ry", 0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0, 1e6, SPIN_STEP, SPIN_PAGE_STEP,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_rtb_ry_value_changed, tracker);
@@ -419,7 +419,7 @@ static void rect_toolbox_watch_ec(SPDesktop* desktop, Inkscape::UI::Tools::ToolB
     } else {
         if (changed) {
             changed.disconnect();
-            purge_repr_listener(NULL, holder);
+            purge_repr_listener(nullptr, holder);
         }
     }
 }
diff --git a/src/ui/toolbar/select-toolbar.cpp b/src/ui/toolbar/select-toolbar.cpp
index 47a9b9ed7..fcb76a185 100644
--- a/src/ui/toolbar/select-toolbar.cpp
+++ b/src/ui/toolbar/select-toolbar.cpp
@@ -76,7 +76,7 @@ sp_selection_layout_widget_update(SPWidget *spw, Inkscape::Selection *sel)
         if ( bbox ) {
             UnitTracker *tracker = reinterpret_cast<UnitTracker*>(g_object_get_data(G_OBJECT(spw), "tracker"));
             Unit const *unit = tracker->getActiveUnit();
-            g_return_if_fail(unit != NULL);
+            g_return_if_fail(unit != nullptr);
 
             struct { char const *key; double val; } const keyval[] = {
                 { "X", bbox->min()[X] },
@@ -182,7 +182,7 @@ sp_object_layout_any_value_changed(GtkAdjustment *adj, GObject *tbl)
     gdouble xrel = 0;
     gdouble yrel = 0;
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
 
     GtkAdjustment* a_x = GTK_ADJUSTMENT( g_object_get_data( tbl, "X" ) );
     GtkAdjustment* a_y = GTK_ADJUSTMENT( g_object_get_data( tbl, "Y" ) );
@@ -239,9 +239,9 @@ sp_object_layout_any_value_changed(GtkAdjustment *adj, GObject *tbl)
     char const * const actionkey = ( mh > 5e-4 ? "selector:toolbar:move:horizontal" :
                                      sh > 5e-4 ? "selector:toolbar:scale:horizontal" :
                                      mv > 5e-4 ? "selector:toolbar:move:vertical" :
-                                     sv > 5e-4 ? "selector:toolbar:scale:vertical" : NULL );
+                                     sv > 5e-4 ? "selector:toolbar:scale:vertical" : nullptr );
 
-    if (actionkey != NULL) {
+    if (actionkey != nullptr) {
 
         // FIXME: fix for GTK breakage, see comment in SelectedStyle::on_opacity_changed
         desktop->getCanvas()->forceFullRedrawAfterInterruptions(0);
@@ -339,7 +339,7 @@ static void destroy_tracker( GObject* obj, gpointer /*user_data*/ )
     UnitTracker *tracker = reinterpret_cast<UnitTracker*>(g_object_get_data(obj, "tracker"));
     if ( tracker ) {
         delete tracker;
-        g_object_set_data( obj, "tracker", 0 );
+        g_object_set_data( obj, "tracker", nullptr );
     }
 }
 
@@ -347,13 +347,13 @@ 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  );
@@ -370,7 +370,7 @@ void sp_select_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
     GtkIconSize secondarySize = Inkscape::UI::ToolboxFactory::prefToSize("/toolbox/secondary", 1);
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
-    GtkAction* act = 0;
+    GtkAction* act = nullptr;
 
     GtkActionGroup* selectionActions = mainActions; // temporary
     std::vector<GtkAction*>* contextActions = new std::vector<GtkAction*>();
@@ -429,7 +429,7 @@ void sp_select_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
     g_object_set_data( G_OBJECT(spw), "tracker", tracker );
     g_signal_connect( G_OBJECT(spw), "destroy", G_CALLBACK(destroy_tracker), spw );
 
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
 
     // four spinbuttons
 
@@ -444,7 +444,7 @@ void sp_select_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
             G_OBJECT(spw),                        /* dataKludge */ 
             TRUE, "altx",                         /* altx, altx_mark */ 
             -1e6, 1e6, SPIN_STEP, SPIN_PAGE_STEP, /* lower, upper, step, page */ 
-            0, 0, 0,                              /* descrLabels, descrValues, descrCount */ 
+            nullptr, nullptr, 0,                              /* descrLabels, descrValues, descrCount */ 
             sp_object_layout_any_value_changed,   /* callback */ 
             tracker,                              /* unit_tracker */ 
             SPIN_STEP, 3, 1);                     /* climb, digits, factor */
@@ -463,7 +463,7 @@ void sp_select_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
             G_OBJECT(spw),                        /* dataKludge */
             TRUE, "altx",                         /* altx, altx_mark */
             -1e6, 1e6, SPIN_STEP, SPIN_PAGE_STEP, /* lower, upper, step, page */
-            0, 0, 0,                              /* descrLabels, descrValues, descrCount */
+            nullptr, nullptr, 0,                              /* descrLabels, descrValues, descrCount */
             sp_object_layout_any_value_changed,   /* callback */
             tracker,                              /* unit_tracker */
             SPIN_STEP, 3, 1);                     /* climb, digits, factor */              
@@ -482,7 +482,7 @@ void sp_select_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
             G_OBJECT(spw),                        /* dataKludge */
             TRUE, "altx",                         /* altx, altx_mark */
             0.0, 1e6, SPIN_STEP, SPIN_PAGE_STEP,  /* lower, upper, step, page */
-            0, 0, 0,                              /* descrLabels, descrValues, descrCount */
+            nullptr, nullptr, 0,                              /* descrLabels, descrValues, descrCount */
             sp_object_layout_any_value_changed,   /* callback */
             tracker,                              /* unit_tracker */
             SPIN_STEP, 3, 1);                     /* climb, digits, factor */
@@ -514,7 +514,7 @@ void sp_select_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
             G_OBJECT(spw),                        /* dataKludge */
             TRUE, "altx",                         /* altx, altx_mark */
             0.0, 1e6, SPIN_STEP, SPIN_PAGE_STEP,  /* lower, upper, step, page */
-            0, 0, 0,                              /* descrLabels, descrValues, descrCount */
+            nullptr, nullptr, 0,                              /* descrLabels, descrValues, descrCount */
             sp_object_layout_any_value_changed,   /* callback */
             tracker,                              /* unit_tracker */
             SPIN_STEP, 3, 1);                     /* climb, digits, factor */
@@ -537,7 +537,7 @@ void sp_select_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
     g_signal_connect(G_OBJECT(spw), "change_selection", G_CALLBACK(sp_selection_layout_widget_change_selection), desktop);
 
     // Update now.
-    sp_selection_layout_widget_update(SP_WIDGET(spw), SP_ACTIVE_DESKTOP ? SP_ACTIVE_DESKTOP->getSelection() : NULL);
+    sp_selection_layout_widget_update(SP_WIDGET(spw), SP_ACTIVE_DESKTOP ? SP_ACTIVE_DESKTOP->getSelection() : nullptr);
 
     for ( std::vector<GtkAction*>::iterator iter = contextActions->begin();
           iter != contextActions->end(); ++iter) {
diff --git a/src/ui/toolbar/spiral-toolbar.cpp b/src/ui/toolbar/spiral-toolbar.cpp
index c5c87755d..b551ea379 100644
--- a/src/ui/toolbar/spiral-toolbar.cpp
+++ b/src/ui/toolbar/spiral-toolbar.cpp
@@ -189,17 +189,17 @@ static void spiral_tb_event_attr_changed(Inkscape::XML::Node *repr,
 
 
 static Inkscape::XML::NodeEventVector spiral_tb_repr_events = {
-    NULL, /* child_added */
-    NULL, /* child_removed */
+    nullptr, /* child_added */
+    nullptr, /* child_removed */
     spiral_tb_event_attr_changed,
-    NULL, /* content_changed */
-    NULL  /* order_changed */
+    nullptr, /* content_changed */
+    nullptr  /* order_changed */
 };
 
 static void sp_spiral_toolbox_selection_changed(Inkscape::Selection *selection, GObject *tbl)
 {
     int n_selected = 0;
-    Inkscape::XML::Node *repr = NULL;
+    Inkscape::XML::Node *repr = nullptr;
 
     purge_repr_listener( tbl, tbl );
 
@@ -235,11 +235,11 @@ static void sp_spiral_toolbox_selection_changed(Inkscape::Selection *selection,
 
 void sp_spiral_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObject* holder)
 {
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
     GtkIconSize secondarySize = ToolboxFactory::prefToSize("/toolbox/secondary", 1);
 
     {
-        EgeOutputAction* act = ege_output_action_new( "SpiralStateAction", _("<b>New:</b>"), "", 0 );
+        EgeOutputAction* act = ege_output_action_new( "SpiralStateAction", _("<b>New:</b>"), "", nullptr );
         ege_output_action_set_use_markup( act, TRUE );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
         g_object_set_data( holder, "mode_action", act );
@@ -247,7 +247,7 @@ void sp_spiral_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
 
     /* Revolution */
     {
-        gchar const* labels[] = {_("just a curve"), 0, _("one full revolution"), 0, 0, 0, 0, 0, 0};
+        gchar const* labels[] = {_("just a curve"), nullptr, _("one full revolution"), nullptr, nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {0.01, 0.5, 1, 2, 3, 5, 10, 20, 50, 100};
         eact = create_adjustment_action( "SpiralRevolutionAction",
                                          _("Number of turns"), _("Turns:"), _("Number of revolutions"),
@@ -255,18 +255,18 @@ void sp_spiral_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
                                          GTK_WIDGET(desktop->canvas), holder, TRUE, "altx-spiral",
                                          0.01, 1024.0, 0.1, 1.0,
                                          labels, values, G_N_ELEMENTS(labels),
-                                         sp_spl_tb_revolution_value_changed, NULL /*unit tracker*/, 1, 2);
+                                         sp_spl_tb_revolution_value_changed, nullptr /*unit tracker*/, 1, 2);
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
     }
 
     /* Expansion */
     {
-        gchar const* labels[] = {_("circle"), _("edge is much denser"), _("edge is denser"), _("even"), _("center is denser"), _("center is much denser"), 0};
+        gchar const* labels[] = {_("circle"), _("edge is much denser"), _("edge is denser"), _("even"), _("center is denser"), _("center is much denser"), nullptr};
         gdouble values[] = {0, 0.1, 0.5, 1, 1.5, 5, 20};
         eact = create_adjustment_action( "SpiralExpansionAction",
                                          _("Divergence"), _("Divergence:"), _("How much denser/sparser are outer revolutions; 1 = uniform"),
                                          "/tools/shapes/spiral/expansion", 1.0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0.0, 1000.0, 0.01, 1.0,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_spl_tb_expansion_value_changed);
@@ -280,7 +280,7 @@ void sp_spiral_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GOb
         eact = create_adjustment_action( "SpiralT0Action",
                                          _("Inner radius"), _("Inner radius:"), _("Radius of the innermost revolution (relative to the spiral size)"),
                                          "/tools/shapes/spiral/t0", 0.0,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0.0, 0.999, 0.01, 1.0,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_spl_tb_t0_value_changed);
diff --git a/src/ui/toolbar/spray-toolbar.cpp b/src/ui/toolbar/spray-toolbar.cpp
index f44e61051..894a69a69 100644
--- a/src/ui/toolbar/spray-toolbar.cpp
+++ b/src/ui/toolbar/spray-toolbar.cpp
@@ -137,7 +137,7 @@ Inkscape::UI::Dialog::CloneTiler *get_clone_tiler_panel(SPDesktop *desktop)
         } catch (std::exception &e) { }
     }
 
-    return 0;
+    return nullptr;
 }
 
 static void sp_spray_width_value_changed( GtkAdjustment *adj, GObject * /*tbl*/ )
@@ -290,7 +290,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
     {
         /* Width */
-        gchar const* labels[] = {_("(narrow spray)"), 0, 0, 0, _("(default)"), 0, 0, 0, 0, _("(broad spray)")};
+        gchar const* labels[] = {_("(narrow spray)"), nullptr, nullptr, nullptr, _("(default)"), nullptr, nullptr, nullptr, nullptr, _("(broad spray)")};
         gdouble values[] = {1, 3, 5, 10, 15, 20, 30, 50, 75, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "SprayWidthAction",
                                                               _("Width"), _("Width:"), _("The width of the spray area (relative to the visible canvas area)"),
@@ -298,7 +298,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, true, "altx-spray",
                                                               1, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_spray_width_value_changed, NULL /*unit tracker*/, 1, 0 );
+                                                              sp_spray_width_value_changed, nullptr /*unit tracker*/, 1, 0 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), true );
@@ -319,7 +319,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
     
     {
         /* Mean */
-        gchar const* labels[] = {_("(default)"), 0, 0, 0, 0, 0, 0, _("(maximum mean)")};
+        gchar const* labels[] = {_("(default)"), nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, _("(maximum mean)")};
         gdouble values[] = {0, 5, 10, 20, 30, 50, 70, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "SprayMeanAction",
                                                               _("Focus"), _("Focus:"), _("0 to spray a spot; increase to enlarge the ring radius"),
@@ -327,7 +327,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, true, "spray-mean",
                                                               0, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_spray_mean_value_changed, NULL /*unit tracker*/, 1, 0 );
+                                                              sp_spray_mean_value_changed, nullptr /*unit tracker*/, 1, 0 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), true );
@@ -335,7 +335,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
 
     {
         /* Standard_deviation */
-        gchar const* labels[] = {_("(minimum scatter)"), 0, 0, 0, 0, 0, _("(default)"), _("(maximum scatter)")};
+        gchar const* labels[] = {_("(minimum scatter)"), nullptr, nullptr, nullptr, nullptr, nullptr, _("(default)"), _("(maximum scatter)")};
         gdouble values[] = {1, 5, 10, 20, 30, 50, 70, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "SprayStandard_deviationAction",
                                                               C_("Spray tool", "Scatter"), C_("Spray tool", "Scatter:"), _("Increase to scatter sprayed objects"),
@@ -343,7 +343,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, true, "spray-standard_deviation",
                                                               1, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_spray_standard_deviation_value_changed, NULL /*unit tracker*/, 1, 0 );
+                                                              sp_spray_standard_deviation_value_changed, nullptr /*unit tracker*/, 1, 0 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), true );
@@ -402,7 +402,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
     }
 
     {   /* Population */
-        gchar const* labels[] = {_("(low population)"), 0, 0, 0, _("(default)"), 0, _("(high population)")};
+        gchar const* labels[] = {_("(low population)"), nullptr, nullptr, nullptr, _("(default)"), nullptr, _("(high population)")};
         gdouble values[] = {5, 20, 35, 50, 70, 85, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "SprayPopulationAction",
                                                               _("Amount"), _("Amount:"),
@@ -411,7 +411,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, true, "spray-population",
                                                               1, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_spray_population_value_changed, NULL /*unit tracker*/, 1, 0 );
+                                                              sp_spray_population_value_changed, nullptr /*unit tracker*/, 1, 0 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), true );
@@ -432,7 +432,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
     }
 
     {   /* Rotation */
-        gchar const* labels[] = {_("(default)"), 0, 0, 0, 0, 0, 0, _("(high rotation variation)")};
+        gchar const* labels[] = {_("(default)"), nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, _("(high rotation variation)")};
         gdouble values[] = {0, 10, 25, 35, 50, 60, 80, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "SprayRotationAction",
                                                               _("Rotation"), _("Rotation:"),
@@ -442,7 +442,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, true, "spray-rotation",
                                                               0, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_spray_rotation_value_changed, NULL /*unit tracker*/, 1, 0 );
+                                                              sp_spray_rotation_value_changed, nullptr /*unit tracker*/, 1, 0 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), true );
@@ -450,7 +450,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
     }
 
     {   /* Scale */
-        gchar const* labels[] = {_("(default)"), 0, 0, 0, 0, 0, 0, _("(high scale variation)")};
+        gchar const* labels[] = {_("(default)"), nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, _("(high scale variation)")};
         gdouble values[] = {0, 10, 25, 35, 50, 60, 80, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "SprayScaleAction",
                                                               C_("Spray tool", "Scale"), C_("Spray tool", "Scale:"),
@@ -460,7 +460,7 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, true, "spray-scale",
                                                               0, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_spray_scale_value_changed, NULL /*unit tracker*/, 1, 0 );
+                                                              sp_spray_scale_value_changed, nullptr /*unit tracker*/, 1, 0 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), true );
@@ -599,16 +599,16 @@ void sp_spray_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
     
     /* Offset */
     {
-        gchar const* labels[] = {_("(minimum offset)"), 0, 0, 0, _("(default)"), 0, 0, _("(maximum offset)")};
+        gchar const* labels[] = {_("(minimum offset)"), nullptr, nullptr, nullptr, _("(default)"), nullptr, nullptr, _("(maximum offset)")};
         gdouble values[] = {0, 25, 50, 75, 100, 150, 200, 1000};
         EgeAdjustmentAction *eact = create_adjustment_action( "SprayToolOffsetAction",
                                          _("Offset %"), _("Offset %:"),
                                          _("Increase to segregate objects more (value in percent)"),
                                          "/tools/spray/offset", 100,
-                                         GTK_WIDGET(desktop->canvas), holder, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), holder, FALSE, nullptr,
                                          0, 1000, 1, 4,
                                          labels, values, G_N_ELEMENTS(labels),
-                                         sp_spray_offset_value_changed, NULL, 0 , 0);
+                                         sp_spray_offset_value_changed, nullptr, 0 , 0);
         g_object_set_data( holder, "offset", eact );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
     }
diff --git a/src/ui/toolbar/star-toolbar.cpp b/src/ui/toolbar/star-toolbar.cpp
index 1c5745273..6cd225c78 100644
--- a/src/ui/toolbar/star-toolbar.cpp
+++ b/src/ui/toolbar/star-toolbar.cpp
@@ -300,7 +300,7 @@ static void star_tb_event_attr_changed(Inkscape::XML::Node *repr, gchar const *n
     // in turn, prevent callbacks from responding
     g_object_set_data(dataKludge, "freeze", GINT_TO_POINTER(TRUE));
 
-    GtkAdjustment *adj = 0;
+    GtkAdjustment *adj = nullptr;
 
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
     bool isFlatSided = prefs->getBool("/tools/shapes/star/isflatsided", true);
@@ -361,11 +361,11 @@ static void star_tb_event_attr_changed(Inkscape::XML::Node *repr, gchar const *n
 
 static Inkscape::XML::NodeEventVector star_tb_repr_events =
 {
-    NULL, /* child_added */
-    NULL, /* child_removed */
+    nullptr, /* child_added */
+    nullptr, /* child_removed */
     star_tb_event_attr_changed,
-    NULL, /* content_changed */
-    NULL  /* order_changed */
+    nullptr, /* content_changed */
+    nullptr  /* order_changed */
 };
 
 
@@ -376,7 +376,7 @@ static void
 sp_star_toolbox_selection_changed(Inkscape::Selection *selection, GObject *dataKludge)
 {
     int n_selected = 0;
-    Inkscape::XML::Node *repr = NULL;
+    Inkscape::XML::Node *repr = nullptr;
 
     purge_repr_listener( dataKludge, dataKludge );
 
@@ -415,7 +415,7 @@ static void sp_star_defaults( GtkWidget * /*widget*/, GObject *dataKludge )
     // FIXME: in this and all other _default functions, set some flag telling the value_changed
     // callbacks to lump all the changes for all selected objects in one undo step
 
-    GtkAdjustment *adj = 0;
+    GtkAdjustment *adj = nullptr;
 
     // fixme: make settable in prefs!
     gint mag = 5;
@@ -469,10 +469,10 @@ void sp_star_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
     bool isFlatSided = prefs->getBool("/tools/shapes/star/isflatsided", true);
 
-    EgeAdjustmentAction* eact = 0;
+    EgeAdjustmentAction* eact = nullptr;
 
     {
-        EgeOutputAction* act = ege_output_action_new( "StarStateAction", _("<b>New:</b>"), "", 0 );
+        EgeOutputAction* act = ege_output_action_new( "StarStateAction", _("<b>New:</b>"), "", nullptr );
         ege_output_action_set_use_markup( act, TRUE );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
         g_object_set_data( dataKludge, "mode_action", act );
@@ -516,15 +516,15 @@ void sp_star_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
 
     /* Magnitude */
     {
-        gchar const* labels[] = {_("triangle/tri-star"), _("square/quad-star"), _("pentagon/five-pointed star"), _("hexagon/six-pointed star"), 0, 0, 0, 0, 0};
+        gchar const* labels[] = {_("triangle/tri-star"), _("square/quad-star"), _("pentagon/five-pointed star"), _("hexagon/six-pointed star"), nullptr, nullptr, nullptr, nullptr, nullptr};
         gdouble values[] = {3, 4, 5, 6, 7, 8, 10, 12, 20};
         eact = create_adjustment_action( "MagnitudeAction",
                                          _("Corners"), _("Corners:"), _("Number of corners of a polygon or star"),
                                          "/tools/shapes/star/magnitude", 3,
-                                         GTK_WIDGET(desktop->canvas), dataKludge, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), dataKludge, FALSE, nullptr,
                                          3, 1024, 1, 5,
                                          labels, values, G_N_ELEMENTS(labels),
-                                         sp_star_magnitude_value_changed, NULL /*unit tracker*/,
+                                         sp_star_magnitude_value_changed, nullptr /*unit tracker*/,
                                          1.0, 0 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -532,7 +532,7 @@ void sp_star_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
 
     /* Spoke ratio */
     {
-        gchar const* labels[] = {_("thin-ray star"), 0, _("pentagram"), _("hexagram"), _("heptagram"), _("octagram"), _("regular polygon")};
+        gchar const* labels[] = {_("thin-ray star"), nullptr, _("pentagram"), _("hexagram"), _("heptagram"), _("octagram"), _("regular polygon")};
         gdouble values[] = {0.01, 0.2, 0.382, 0.577, 0.692, 0.765, 1};
         eact = create_adjustment_action( "SpokeAction",
                                          _("Spoke ratio"), _("Spoke ratio:"),
@@ -540,7 +540,7 @@ void sp_star_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
                                          // Base radius is the same for the closest handle.
                                          _("Base radius to tip radius ratio"),
                                          "/tools/shapes/star/proportion", 0.5,
-                                         GTK_WIDGET(desktop->canvas), dataKludge, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), dataKludge, FALSE, nullptr,
                                          0.01, 1.0, 0.01, 0.1,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_star_proportion_value_changed );
@@ -557,12 +557,12 @@ void sp_star_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     /* Roundedness */
     {
         gchar const* labels[] = {_("stretched"), _("twisted"), _("slightly pinched"), _("NOT rounded"), _("slightly rounded"),
-                                 _("visibly rounded"), _("well rounded"), _("amply rounded"), 0, _("stretched"), _("blown up")};
+                                 _("visibly rounded"), _("well rounded"), _("amply rounded"), nullptr, _("stretched"), _("blown up")};
         gdouble values[] = {-1, -0.2, -0.03, 0, 0.05, 0.1, 0.2, 0.3, 0.5, 1, 10};
         eact = create_adjustment_action( "RoundednessAction",
                                          _("Rounded"), _("Rounded:"), _("How much rounded are the corners (0 for sharp)"),
                                          "/tools/shapes/star/rounded", 0.0,
-                                         GTK_WIDGET(desktop->canvas), dataKludge, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), dataKludge, FALSE, nullptr,
                                          -10.0, 10.0, 0.01, 0.1,
                                          labels, values, G_N_ELEMENTS(labels),
                                          sp_star_rounded_value_changed );
@@ -577,10 +577,10 @@ void sp_star_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
         eact = create_adjustment_action( "RandomizationAction",
                                          _("Randomized"), _("Randomized:"), _("Scatter randomly the corners and angles"),
                                          "/tools/shapes/star/randomized", 0.0,
-                                         GTK_WIDGET(desktop->canvas), dataKludge, FALSE, NULL,
+                                         GTK_WIDGET(desktop->canvas), dataKludge, FALSE, nullptr,
                                          -10.0, 10.0, 0.001, 0.01,
                                          labels, values, G_N_ELEMENTS(labels),
-                                         sp_star_randomized_value_changed, NULL /*unit tracker*/, 0.1, 3 );
+                                         sp_star_randomized_value_changed, nullptr /*unit tracker*/, 0.1, 3 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
     }
@@ -605,7 +605,7 @@ static void star_toolbox_watch_ec(SPDesktop* desktop, Inkscape::UI::Tools::ToolB
 {
     static sigc::connection changed;
 
-    if (dynamic_cast<Inkscape::UI::Tools::StarTool const*>(ec) != NULL) {
+    if (dynamic_cast<Inkscape::UI::Tools::StarTool const*>(ec) != nullptr) {
         changed = desktop->getSelection()->connectChanged(sigc::bind(sigc::ptr_fun(sp_star_toolbox_selection_changed), dataKludge));
         sp_star_toolbox_selection_changed(desktop->getSelection(), dataKludge);
     } else {
diff --git a/src/ui/toolbar/text-toolbar.cpp b/src/ui/toolbar/text-toolbar.cpp
index 4f532fa3d..a521c165d 100644
--- a/src/ui/toolbar/text-toolbar.cpp
+++ b/src/ui/toolbar/text-toolbar.cpp
@@ -341,7 +341,7 @@ static void sp_text_outer_style_changed( InkToggleAction*act, GObject *tbl )
     prefs->setInt("/tools/text/outer_style", outer);
 
     // Update widgets to reflect new state of Text Outer Style button.
-    sp_text_toolbox_selection_changed( NULL, tbl );
+    sp_text_toolbox_selection_changed( nullptr, tbl );
 }
 
 // Unset line height on selection's inner text objects (tspan, etc.).
@@ -663,7 +663,7 @@ static void sp_text_lineheight_value_changed( GtkAdjustment *adj, GObject *tbl )
     // Get user selected unit and save as preference
     UnitTracker *tracker = reinterpret_cast<UnitTracker*>(g_object_get_data(tbl, "tracker"));
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
 
@@ -746,7 +746,7 @@ static void sp_text_lineheight_unit_changed( GObject *tbl, int /* Not Used */ )
     // Get user selected unit and save as preference
     UnitTracker *tracker = reinterpret_cast<UnitTracker*>(g_object_get_data(tbl, "tracker"));
     Unit const *unit = tracker->getActiveUnit();
-    g_return_if_fail(unit != NULL);
+    g_return_if_fail(unit != nullptr);
     Inkscape::Preferences *prefs = Inkscape::Preferences::get();
 
     // This nonsense is to get SP_CSS_UNIT_xx value corresponding to unit.
@@ -1476,7 +1476,7 @@ static void sp_text_toolbox_selection_changed(Inkscape::Selection */*selection*/
     fontlister->selection_update();
 
     // Update font list, but only if widget already created.
-    if( fontFamilyAction->combobox != NULL ) {
+    if( fontFamilyAction->combobox != nullptr ) {
         ink_comboboxentry_action_set_active_text( fontFamilyAction, fontlister->get_font_family().c_str(), fontlister->get_font_family_row() );
         ink_comboboxentry_action_set_active_text( fontStyleAction,  fontlister->get_font_style().c_str()  );
     }
@@ -1553,7 +1553,7 @@ static void sp_text_toolbox_selection_changed(Inkscape::Selection */*selection*/
 
         // To ensure the value of the combobox is properly set on start-up, only mark
         // the prefs set if the combobox has already been constructed.
-        if( fontFamilyAction->combobox != NULL ) {
+        if( fontFamilyAction->combobox != nullptr ) {
             g_object_set_data(tbl, "text_style_from_prefs", GINT_TO_POINTER(TRUE));
         }
     } else {
@@ -1928,7 +1928,7 @@ static void sp_text_toolbox_selection_modified(Inkscape::Selection *selection, g
 static void
 sp_text_toolbox_subselection_changed (gpointer /*tc*/, GObject *tbl)
 {
-    sp_text_toolbox_selection_changed (NULL, tbl, true);
+    sp_text_toolbox_selection_changed (nullptr, tbl, true);
 }
 
 // TODO: possibly share with font-selector by moving most code to font-lister (passing family name)
@@ -1994,7 +1994,7 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
             ink_comboboxentry_action_new( "TextFontFamilyAction",
                                           _("Font Family"),
                                           _("Select Font Family (Alt-X to access)"),
-                                          NULL,
+                                          nullptr,
                                           GTK_TREE_MODEL(model),
                                           -1,                // Entry width
                                           50,                // Extra list width
@@ -2023,7 +2023,7 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
                                         "#TextFontFamilyAction_combobox {\n"
                                         "  -GtkComboBox-appears-as-list: true;\n"
                                         "}\n",
-                                        -1, NULL);
+                                        -1, nullptr);
 
         auto screen = gdk_screen_get_default();
         gtk_style_context_add_provider_for_screen(screen,
@@ -2045,12 +2045,12 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
         Ink_ComboBoxEntry_Action* act = ink_comboboxentry_action_new( "TextFontSizeAction",
                                                                       _("Font Size"),
                                                                       _(tooltip.c_str()),
-                                                                      NULL,
+                                                                      nullptr,
                                                                       GTK_TREE_MODEL(model_size),
                                                                       8,      // Width in characters
                                                                       0,      // Extra list width
-                                                                      NULL,   // Cell layout
-                                                                      NULL,   // Separator
+                                                                      nullptr,   // Cell layout
+                                                                      nullptr,   // Separator
                                                                       GTK_WIDGET(desktop->canvas)); // Focus widget
 
         g_signal_connect( G_OBJECT(act), "changed", G_CALLBACK(sp_text_fontsize_value_changed), holder );
@@ -2067,12 +2067,12 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
         Ink_ComboBoxEntry_Action* act = ink_comboboxentry_action_new( "TextFontStyleAction",
                                                                       _("Font Style"),
                                                                       _("Font style"),
-                                                                      NULL,
+                                                                      nullptr,
                                                                       GTK_TREE_MODEL(model_style),
                                                                       12,     // Width in characters
                                                                       0,      // Extra list width
-                                                                      NULL,   // Cell layout
-                                                                      NULL,   // Separator
+                                                                      nullptr,   // Cell layout
+                                                                      nullptr,   // Separator
                                                                       GTK_WIDGET(desktop->canvas)); // Focus widget
 
         g_signal_connect( G_OBJECT(act), "changed", G_CALLBACK(sp_text_fontstyle_value_changed), holder );
@@ -2291,7 +2291,7 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     /* Line height */
     {
         // Drop down menu
-        gchar const* labels[] = {_("Smaller spacing"), 0, 0, 0, 0, C_("Text tool", "Normal"), 0, 0, 0, 0, 0, _("Larger spacing")};
+        gchar const* labels[] = {_("Smaller spacing"), nullptr, nullptr, nullptr, nullptr, C_("Text tool", "Normal"), nullptr, nullptr, nullptr, nullptr, nullptr, _("Larger spacing")};
         gdouble values[] = { 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1,2, 1.3, 1.4, 1.5, 2.0};
 
         EgeAdjustmentAction *eact = create_adjustment_action(
@@ -2304,11 +2304,11 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
             GTK_WIDGET(desktop->canvas),          /* focusTarget */
             holder,                               /* dataKludge */
             FALSE,                                /* set alt-x keyboard shortcut? */
-            NULL,                                 /* altx_mark */
+            nullptr,                                 /* altx_mark */
             0.0, 1000.0, 0.1, 1.0,                /* lower, upper, step (arrow up/down), page up/down */
             labels, values, G_N_ELEMENTS(labels), /* drop down menu */
             sp_text_lineheight_value_changed,     /* callback */
-            NULL, // tracker,                     /* unit tracker */
+            nullptr, // tracker,                     /* unit tracker */
             0.1,                                  /* step (used?) */
             2,                                    /* digits to show */
             1.0                                   /* factor (multiplies default) */
@@ -2379,7 +2379,7 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     /* Word spacing */
     {
         // Drop down menu
-        gchar const* labels[] = {_("Negative spacing"), 0, 0, 0, C_("Text tool", "Normal"), 0, 0, 0, 0, 0, 0, 0, _("Positive spacing")};
+        gchar const* labels[] = {_("Negative spacing"), nullptr, nullptr, nullptr, C_("Text tool", "Normal"), nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, _("Positive spacing")};
         gdouble values[] = {-2.0, -1.5, -1.0, -0.5, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0};
 
         EgeAdjustmentAction *eact = create_adjustment_action(
@@ -2392,11 +2392,11 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
             GTK_WIDGET(desktop->canvas),          /* focusTarget */
             holder,                               /* dataKludge */
             FALSE,                                /* set alt-x keyboard shortcut? */
-            NULL,                                 /* altx_mark */
+            nullptr,                                 /* altx_mark */
             -100.0, 100.0, 0.01, 0.10,            /* lower, upper, step (arrow up/down), page up/down */
             labels, values, G_N_ELEMENTS(labels), /* drop down menu */
             sp_text_wordspacing_value_changed,    /* callback */
-            NULL,                                 /* unit tracker */
+            nullptr,                                 /* unit tracker */
             0.1,                                  /* step (used?) */
             2,                                    /* digits to show */
             1.0                                   /* factor (multiplies default) */
@@ -2410,7 +2410,7 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     /* Letter spacing */
     {
         // Drop down menu
-        gchar const* labels[] = {_("Negative spacing"), 0, 0, 0, C_("Text tool", "Normal"), 0, 0, 0, 0, 0, 0, 0, _("Positive spacing")};
+        gchar const* labels[] = {_("Negative spacing"), nullptr, nullptr, nullptr, C_("Text tool", "Normal"), nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, _("Positive spacing")};
         gdouble values[] = {-2.0, -1.5, -1.0, -0.5, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0};
 
         EgeAdjustmentAction *eact = create_adjustment_action(
@@ -2423,11 +2423,11 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
             GTK_WIDGET(desktop->canvas),          /* focusTarget */
             holder,                               /* dataKludge */
             FALSE,                                /* set alt-x keyboard shortcut? */
-            NULL,                                 /* altx_mark */
+            nullptr,                                 /* altx_mark */
             -100.0, 100.0, 0.01, 0.10,            /* lower, upper, step (arrow up/down), page up/down */
             labels, values, G_N_ELEMENTS(labels), /* drop down menu */
             sp_text_letterspacing_value_changed,  /* callback */
-            NULL,                                 /* unit tracker */
+            nullptr,                                 /* unit tracker */
             0.1,                                  /* step (used?) */
             2,                                    /* digits to show */
             1.0                                   /* factor (multiplies default) */
@@ -2441,7 +2441,7 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     /* Character kerning (horizontal shift) */
     {
         // Drop down menu
-        gchar const* labels[] = {   0,   0,   0,   0,   0,   0,   0,   0,   0,   0 };
+        gchar const* labels[] = {   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr };
         gdouble values[]      = { -2.0, -1.5, -1.0, -0.5,   0,  0.5,  1.0,  1.5,  2.0, 2.5 };
 
         EgeAdjustmentAction *eact = create_adjustment_action(
@@ -2454,11 +2454,11 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
             GTK_WIDGET(desktop->canvas),          /* focusTarget */
             holder,                               /* dataKludge */
             FALSE,                                /* set alt-x keyboard shortcut? */
-            NULL,                                 /* altx_mark */
+            nullptr,                                 /* altx_mark */
             -100.0, 100.0, 0.01, 0.1,             /* lower, upper, step (arrow up/down), page up/down */
             labels, values, G_N_ELEMENTS(labels), /* drop down menu */
             sp_text_dx_value_changed,             /* callback */
-            NULL,                                 /* unit tracker */
+            nullptr,                                 /* unit tracker */
             0.1,                                  /* step (used?) */
             2,                                    /* digits to show */
             1.0                                   /* factor (multiplies default) */
@@ -2472,7 +2472,7 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     /* Character vertical shift */
     {
         // Drop down menu
-        gchar const* labels[] = {   0,   0,   0,   0,   0,   0,   0,   0,   0,   0 };
+        gchar const* labels[] = {   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr };
         gdouble values[]      = { -2.0, -1.5, -1.0, -0.5,   0,  0.5,  1.0,  1.5,  2.0, 2.5 };
 
         EgeAdjustmentAction *eact = create_adjustment_action(
@@ -2485,11 +2485,11 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
             GTK_WIDGET(desktop->canvas),          /* focusTarget */
             holder,                               /* dataKludge */
             FALSE,                                /* set alt-x keyboard shortcut? */
-            NULL,                                 /* altx_mark */
+            nullptr,                                 /* altx_mark */
             -100.0, 100.0, 0.01, 0.1,             /* lower, upper, step (arrow up/down), page up/down */
             labels, values, G_N_ELEMENTS(labels), /* drop down menu */
             sp_text_dy_value_changed,             /* callback */
-            NULL,                                 /* unit tracker */
+            nullptr,                                 /* unit tracker */
             0.1,                                  /* step (used?) */
             2,                                    /* digits to show */
             1.0                                   /* factor (multiplies default) */
@@ -2503,7 +2503,7 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
     /* Character rotation */
     {
         // Drop down menu
-        gchar const* labels[] = {   0,   0,   0,   0,   0,   0,   0,   0,   0,   0 };
+        gchar const* labels[] = {   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr,   nullptr };
         gdouble values[]      = { -90, -45, -30, -15,   0,  15,  30,  45,  90, 180 };
 
         EgeAdjustmentAction *eact = create_adjustment_action(
@@ -2516,11 +2516,11 @@ void sp_text_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObje
             GTK_WIDGET(desktop->canvas),          /* focusTarget */
             holder,                               /* dataKludge */
             FALSE,                                /* set alt-x keyboard shortcut? */
-            NULL,                                 /* altx_mark */
+            nullptr,                                 /* altx_mark */
             -180.0, 180.0, 0.1, 1.0,              /* lower, upper, step (arrow up/down), page up/down */
             labels, values, G_N_ELEMENTS(labels), /* drop down menu */
             sp_text_rotation_value_changed,       /* callback */
-            NULL,                                 /* unit tracker */
+            nullptr,                                 /* unit tracker */
             0.1,                                  /* step (used?) */
             2,                                    /* digits to show */
             1.0                                   /* factor (multiplies default) */
diff --git a/src/ui/toolbar/tweak-toolbar.cpp b/src/ui/toolbar/tweak-toolbar.cpp
index 173e99479..be6dda4e5 100644
--- a/src/ui/toolbar/tweak-toolbar.cpp
+++ b/src/ui/toolbar/tweak-toolbar.cpp
@@ -126,7 +126,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
 
     {
         /* Width */
-        gchar const* labels[] = {_("(pinch tweak)"), 0, 0, 0, _("(default)"), 0, 0, 0, 0, _("(broad tweak)")};
+        gchar const* labels[] = {_("(pinch tweak)"), nullptr, nullptr, nullptr, _("(default)"), nullptr, nullptr, nullptr, nullptr, _("(broad tweak)")};
         gdouble values[] = {1, 3, 5, 10, 15, 20, 30, 50, 75, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "TweakWidthAction",
                                                               _("Width"), _("Width:"), _("The width of the tweak area (relative to the visible canvas area)"),
@@ -134,7 +134,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, TRUE, "altx-tweak",
                                                               1, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_tweak_width_value_changed, NULL /*unit tracker*/, 0.01, 0, 100 );
+                                                              sp_tweak_width_value_changed, nullptr /*unit tracker*/, 0.01, 0, 100 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -143,7 +143,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
 
     {
         /* Force */
-        gchar const* labels[] = {_("(minimum force)"), 0, 0, _("(default)"), 0, 0, 0, _("(maximum force)")};
+        gchar const* labels[] = {_("(minimum force)"), nullptr, nullptr, _("(default)"), nullptr, nullptr, nullptr, _("(maximum force)")};
         gdouble values[] = {1, 5, 10, 20, 30, 50, 70, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "TweakForceAction",
                                                               _("Force"), _("Force:"), _("The force of the tweak action"),
@@ -151,7 +151,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, TRUE, "tweak-force",
                                                               1, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_tweak_force_value_changed, NULL /*unit tracker*/, 0.01, 0, 100 );
+                                                              sp_tweak_force_value_changed, nullptr /*unit tracker*/, 0.01, 0, 100 );
         ege_adjustment_action_set_appearance( eact, TOOLBAR_SLIDER_HINT );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_sensitive( GTK_ACTION(eact), TRUE );
@@ -266,7 +266,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
     guint mode = prefs->getInt("/tools/tweak/mode", 0);
 
     {
-        EgeOutputAction* act = ege_output_action_new( "TweakChannelsLabel", _("Channels:"), "", 0 );
+        EgeOutputAction* act = ege_output_action_new( "TweakChannelsLabel", _("Channels:"), "", nullptr );
         ege_output_action_set_use_markup( act, TRUE );
         gtk_action_group_add_action( mainActions, GTK_ACTION( act ) );
         if (mode != Inkscape::UI::Tools::TWEAK_MODE_COLORPAINT && mode != Inkscape::UI::Tools::TWEAK_MODE_COLORJITTER) {
@@ -279,7 +279,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
         InkToggleAction* act = ink_toggle_action_new( "TweakDoH",
                                                       _("Hue"),
                                                       _("In color mode, act on objects' hue"),
-                                                      NULL,
+                                                      nullptr,
                                                       GTK_ICON_SIZE_MENU );
         //TRANSLATORS:  "H" here stands for hue
         g_object_set( act, "short_label", C_("Hue", "H"), NULL );
@@ -295,7 +295,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
         InkToggleAction* act = ink_toggle_action_new( "TweakDoS",
                                                       _("Saturation"),
                                                       _("In color mode, act on objects' saturation"),
-                                                      NULL,
+                                                      nullptr,
                                                       GTK_ICON_SIZE_MENU );
         //TRANSLATORS: "S" here stands for Saturation
         g_object_set( act, "short_label", C_("Saturation", "S"), NULL );
@@ -311,7 +311,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
         InkToggleAction* act = ink_toggle_action_new( "TweakDoL",
                                                       _("Lightness"),
                                                       _("In color mode, act on objects' lightness"),
-                                                      NULL,
+                                                      nullptr,
                                                       GTK_ICON_SIZE_MENU );
         //TRANSLATORS: "L" here stands for Lightness
         g_object_set( act, "short_label", C_("Lightness", "L"), NULL );
@@ -327,7 +327,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
         InkToggleAction* act = ink_toggle_action_new( "TweakDoO",
                                                       _("Opacity"),
                                                       _("In color mode, act on objects' opacity"),
-                                                      NULL,
+                                                      nullptr,
                                                       GTK_ICON_SIZE_MENU );
         //TRANSLATORS: "O" here stands for Opacity
         g_object_set( act, "short_label", C_("Opacity", "O"), NULL );
@@ -341,7 +341,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
     }
 
     {   /* Fidelity */
-        gchar const* labels[] = {_("(rough, simplified)"), 0, 0, _("(default)"), 0, 0, _("(fine, but many nodes)")};
+        gchar const* labels[] = {_("(rough, simplified)"), nullptr, nullptr, _("(default)"), nullptr, nullptr, _("(fine, but many nodes)")};
         gdouble values[] = {10, 25, 35, 50, 60, 80, 100};
         EgeAdjustmentAction *eact = create_adjustment_action( "TweakFidelityAction",
                                                               _("Fidelity"), _("Fidelity:"),
@@ -350,7 +350,7 @@ void sp_tweak_toolbox_prep(SPDesktop *desktop, GtkActionGroup* mainActions, GObj
                                                               GTK_WIDGET(desktop->canvas), holder, TRUE, "tweak-fidelity",
                                                               1, 100, 1.0, 10.0,
                                                               labels, values, G_N_ELEMENTS(labels),
-                                                              sp_tweak_fidelity_value_changed, NULL /*unit tracker*/, 0.01, 0, 100 );
+                                                              sp_tweak_fidelity_value_changed, nullptr /*unit tracker*/, 0.01, 0, 100 );
         gtk_action_group_add_action( mainActions, GTK_ACTION(eact) );
         gtk_action_set_visible( GTK_ACTION(eact), TRUE );
         if (mode == Inkscape::UI::Tools::TWEAK_MODE_COLORPAINT || mode == Inkscape::UI::Tools::TWEAK_MODE_COLORJITTER) {