Merge pull request #136 from trav90/gtk-work

Improve GTK3 support

7 files changed, 398 insertions, 285 deletions

diff --git a/build/valgrind/x86_64-redhat-linux-gnu.sup b/build/valgrind/x86_64-redhat-linux-gnu.sup
index d253a3a4e..28656e418 100644
--- a/build/valgrind/x86_64-redhat-linux-gnu.sup
+++ b/build/valgrind/x86_64-redhat-linux-gnu.sup
@@ -105,7 +105,6 @@
    fun:g_object_newv
    fun:g_object_new_valist
    fun:g_object_new
-   fun:_ZN13nsLookAndFeel4InitEv
    ...
 }
 # set_color() in gtkstyle.c of GTK version 3.4.4 only can leak GdkRGBA
diff --git a/widget/gtk/WidgetStyleCache.cpp b/widget/gtk/WidgetStyleCache.cpp
index fd099681f..f35a451aa 100644
--- a/widget/gtk/WidgetStyleCache.cpp
+++ b/widget/gtk/WidgetStyleCache.cpp
@@ -434,15 +434,6 @@ CreateScrolledWindowWidget()
 }
 
 static GtkWidget*
-CreateTextViewWidget()
-{
-  GtkWidget* widget = gtk_text_view_new();
-  gtk_container_add(GTK_CONTAINER(GetWidget(MOZ_GTK_SCROLLED_WINDOW)),
-                    widget);
-  return widget;
-}
-
-static GtkWidget*
 CreateMenuSeparatorWidget()
 {
   GtkWidget* widget = gtk_separator_menu_item_new();
@@ -591,8 +582,6 @@ CreateWidget(WidgetNodeType aWidgetType)
       return CreateEntryWidget();
     case MOZ_GTK_SCROLLED_WINDOW: 
       return CreateScrolledWindowWidget();
-    case MOZ_GTK_TEXT_VIEW:
-      return CreateTextViewWidget();
     case MOZ_GTK_TREEVIEW:
       return CreateTreeViewWidget();
     case MOZ_GTK_TREE_HEADER_CELL:
@@ -637,6 +626,24 @@ GetWidget(WidgetNodeType aWidgetType)
   GtkWidget* widget = sWidgetStorage[aWidgetType];
   if (!widget) {
     widget = CreateWidget(aWidgetType);
+    // Some widgets (MOZ_GTK_COMBOBOX_SEPARATOR for instance) may not be
+    // available or implemented.
+    if (!widget)
+      return nullptr;
+    // In GTK versions prior to 3.18, automatic invalidation of style contexts
+    // for widgets was delayed until the next resize event.  Gecko however,
+    // typically uses the style context before the resize event runs and so an
+    // explicit invalidation may be required.  This is necessary if a style
+    // property was retrieved before all changes were made to the style
+    // context.  One such situation is where gtk_button_construct_child()
+    // retrieves the style property "image-spacing" during construction of the
+    // GtkButton, before its parent is set to provide inheritance of ancestor
+    // properties.  More recent GTK versions do not need this, but do not
+    // re-resolve until required and so invalidation does not trigger
+    // unnecessary resolution in general.
+    GtkStyleContext* style = gtk_widget_get_style_context(widget);
+    gtk_style_context_invalidate(style);
+
     sWidgetStorage[aWidgetType] = widget;
   }
   return widget;
@@ -725,6 +732,21 @@ CreateCSSNode(const char* aName, GtkStyleContext* aParentStyle, GType aType)
   gtk_style_context_set_parent(context, aParentStyle);
   gtk_widget_path_unref(path);
 
+  // In GTK 3.4, gtk_render_* functions use |theming_engine| on the style
+  // context without ensuring any style resolution sets it appropriately
+  // in style_data_lookup(). e.g.
+  // https://git.gnome.org/browse/gtk+/tree/gtk/gtkstylecontext.c?h=3.4.4#n3847
+  //
+  // That can result in incorrect drawing on first draw.  To work around this,
+  // force a style look-up to set |theming_engine|.  It is sufficient to do
+  // this only on context creation, instead of after every modification to the
+  // context, because themes typically (Ambiance and oxygen-gtk, at least) set
+  // the "engine" property with the '*' selector.
+  if (GTK_MAJOR_VERSION == 3 && gtk_get_minor_version() < 6) {
+    GdkRGBA unused;
+    gtk_style_context_get_color(context, GTK_STATE_FLAG_NORMAL, &unused);
+  }
+
   return context;
 }
 
@@ -747,13 +769,38 @@ GetWidgetRootStyle(WidgetNodeType aNodeType)
     case MOZ_GTK_IMAGEMENUITEM:
       style = CreateStyleForWidget(gtk_image_menu_item_new(), MOZ_GTK_MENUPOPUP);
       break;
-    case MOZ_GTK_CHECKMENUITEM_CONTAINER:
+    case MOZ_GTK_CHECKMENUITEM:
       style = CreateStyleForWidget(gtk_check_menu_item_new(), MOZ_GTK_MENUPOPUP);
       break;
-    case MOZ_GTK_RADIOMENUITEM_CONTAINER:
+    case MOZ_GTK_RADIOMENUITEM:
       style = CreateStyleForWidget(gtk_radio_menu_item_new(nullptr),
                                    MOZ_GTK_MENUPOPUP);
       break;
+    case MOZ_GTK_TEXT_VIEW:
+      style = CreateStyleForWidget(gtk_text_view_new(),
+                                   MOZ_GTK_SCROLLED_WINDOW);
+      break;
+    case MOZ_GTK_TOOLTIP:
+      if (gtk_check_version(3, 20, 0) != nullptr) {
+          // The tooltip style class is added first in CreateTooltipWidget()
+          // and transfered to style in CreateStyleForWidget().
+          GtkWidget* tooltipWindow = CreateTooltipWidget();
+          style = CreateStyleForWidget(tooltipWindow, nullptr);
+          gtk_widget_destroy(tooltipWindow); // Release GtkWindow self-reference.
+      } else {
+          // We create this from the path because GtkTooltipWindow is not public.
+          style = CreateCSSNode("tooltip", nullptr, GTK_TYPE_TOOLTIP);
+          gtk_style_context_add_class(style, GTK_STYLE_CLASS_BACKGROUND);
+      }
+      break;
+    case MOZ_GTK_TOOLTIP_BOX:
+      style = CreateStyleForWidget(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0),
+                                   MOZ_GTK_TOOLTIP);
+      break;
+    case MOZ_GTK_TOOLTIP_BOX_LABEL:
+      style = CreateStyleForWidget(gtk_label_new(nullptr),
+                                   MOZ_GTK_TOOLTIP_BOX);
+      break;
     default:
       GtkWidget* widget = GetWidget(aNodeType);
       MOZ_ASSERT(widget);
@@ -827,13 +874,13 @@ GetCssNodeStyleInternal(WidgetNodeType aNodeType)
       style = CreateChildCSSNode(GTK_STYLE_CLASS_CHECK,
                                  MOZ_GTK_CHECKBUTTON_CONTAINER);
       break;
-    case MOZ_GTK_RADIOMENUITEM:
+    case MOZ_GTK_RADIOMENUITEM_INDICATOR:
       style = CreateChildCSSNode(GTK_STYLE_CLASS_RADIO,
-                                 MOZ_GTK_RADIOMENUITEM_CONTAINER);
+                                 MOZ_GTK_RADIOMENUITEM);
       break;
-    case MOZ_GTK_CHECKMENUITEM:
+    case MOZ_GTK_CHECKMENUITEM_INDICATOR:
       style = CreateChildCSSNode(GTK_STYLE_CLASS_CHECK,
-                                 MOZ_GTK_CHECKMENUITEM_CONTAINER);
+                                 MOZ_GTK_CHECKMENUITEM);
       break;
     case MOZ_GTK_PROGRESS_TROUGH:
       /* Progress bar background (trough) */
@@ -844,11 +891,6 @@ GetCssNodeStyleInternal(WidgetNodeType aNodeType)
       style = CreateChildCSSNode("progress",
                                  MOZ_GTK_PROGRESS_TROUGH);
       break;
-    case MOZ_GTK_TOOLTIP:
-      // We create this from the path because GtkTooltipWindow is not public.
-      style = CreateCSSNode("tooltip", nullptr, GTK_TYPE_TOOLTIP);
-      gtk_style_context_add_class(style, GTK_STYLE_CLASS_BACKGROUND);
-      break; 
     case MOZ_GTK_GRIPPER:
       // TODO - create from CSS node
       return GetWidgetStyleWithClass(MOZ_GTK_GRIPPER,
@@ -865,10 +907,28 @@ GetCssNodeStyleInternal(WidgetNodeType aNodeType)
       // TODO - create from CSS node
       return GetWidgetStyleWithClass(MOZ_GTK_SCROLLED_WINDOW,
                                      GTK_STYLE_CLASS_FRAME);
-    case MOZ_GTK_TEXT_VIEW:
-      // TODO - create from CSS node
-      return GetWidgetStyleWithClass(MOZ_GTK_TEXT_VIEW,
-                                     GTK_STYLE_CLASS_VIEW);
+    case MOZ_GTK_TEXT_VIEW_TEXT:
+    case MOZ_GTK_RESIZER:
+      style = CreateChildCSSNode("text", MOZ_GTK_TEXT_VIEW);
+      if (aNodeType == MOZ_GTK_RESIZER) {
+        // The "grip" class provides the correct builtin icon from
+        // gtk_render_handle().  The icon is drawn with shaded variants of
+        // the background color, and so a transparent background would lead to
+        // a transparent resizer.  gtk_render_handle() also uses the
+        // background color to draw a background, and so this style otherwise
+        // matches what is used in GtkTextView to match the background with
+        // textarea elements.
+        GdkRGBA color;
+        gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL,
+                                               &color);
+        if (color.alpha == 0.0) {
+          g_object_unref(style);
+          style = CreateStyleForWidget(gtk_text_view_new(),
+                                       MOZ_GTK_SCROLLED_WINDOW);
+        }
+        gtk_style_context_add_class(style, GTK_STYLE_CLASS_GRIP);
+      }
+      break;
     case MOZ_GTK_FRAME_BORDER:
       style = CreateChildCSSNode("border", MOZ_GTK_FRAME);
       break;
@@ -971,27 +1031,20 @@ GetWidgetStyleInternal(WidgetNodeType aNodeType)
     case MOZ_GTK_CHECKBUTTON:
       return GetWidgetStyleWithClass(MOZ_GTK_CHECKBUTTON_CONTAINER,
                                      GTK_STYLE_CLASS_CHECK);
-    case MOZ_GTK_RADIOMENUITEM:
-      return GetWidgetStyleWithClass(MOZ_GTK_RADIOMENUITEM_CONTAINER,
+    case MOZ_GTK_RADIOMENUITEM_INDICATOR:
+      return GetWidgetStyleWithClass(MOZ_GTK_RADIOMENUITEM,
                                      GTK_STYLE_CLASS_RADIO);
-    case MOZ_GTK_CHECKMENUITEM:
-      return GetWidgetStyleWithClass(MOZ_GTK_CHECKMENUITEM_CONTAINER,
+    case MOZ_GTK_CHECKMENUITEM_INDICATOR:
+      return GetWidgetStyleWithClass(MOZ_GTK_CHECKMENUITEM,
                                      GTK_STYLE_CLASS_CHECK);
     case MOZ_GTK_PROGRESS_TROUGH:
       return GetWidgetStyleWithClass(MOZ_GTK_PROGRESSBAR,
                                      GTK_STYLE_CLASS_TROUGH);
-    case MOZ_GTK_TOOLTIP: {
-      GtkStyleContext* style = sStyleStorage[aNodeType];
-      if (style)
-        return style;
-
-      // The tooltip style class is added first in CreateTooltipWidget() so
-      // that gtk_widget_path_append_for_widget() in CreateStyleForWidget()
-      // will find it.
-      GtkWidget* tooltipWindow = CreateTooltipWidget();
-      style = CreateStyleForWidget(tooltipWindow, nullptr);
-      gtk_widget_destroy(tooltipWindow); // Release GtkWindow self-reference.
-      sStyleStorage[aNodeType] = style;
+    case MOZ_GTK_PROGRESS_CHUNK: {
+      GtkStyleContext* style =
+        GetWidgetStyleWithClass(MOZ_GTK_PROGRESSBAR,
+                                GTK_STYLE_CLASS_PROGRESSBAR);
+      gtk_style_context_remove_class(style, GTK_STYLE_CLASS_TROUGH);
       return style;
     }
     case MOZ_GTK_GRIPPER:
@@ -1006,9 +1059,25 @@ GetWidgetStyleInternal(WidgetNodeType aNodeType)
     case MOZ_GTK_SCROLLED_WINDOW:
       return GetWidgetStyleWithClass(MOZ_GTK_SCROLLED_WINDOW,
                                      GTK_STYLE_CLASS_FRAME);
-    case MOZ_GTK_TEXT_VIEW:
-      return GetWidgetStyleWithClass(MOZ_GTK_TEXT_VIEW,
-                                     GTK_STYLE_CLASS_VIEW);
+    case MOZ_GTK_TEXT_VIEW_TEXT:
+    case MOZ_GTK_RESIZER: {
+      // GTK versions prior to 3.20 do not have the view class on the root
+      // node, but add this to determine the background for the text window.
+      GtkStyleContext* style =
+        GetWidgetStyleWithClass(MOZ_GTK_TEXT_VIEW, GTK_STYLE_CLASS_VIEW);
+      if (aNodeType == MOZ_GTK_RESIZER) {
+        // The "grip" class provides the correct builtin icon from
+        // gtk_render_handle().  The icon is drawn with shaded variants of
+        // the background color, and so a transparent background would lead to
+        // a transparent resizer.  gtk_render_handle() also uses the
+        // background color to draw a background, and so this style otherwise
+        // matches MOZ_GTK_TEXT_VIEW_TEXT to match the background with
+        // textarea elements.  GtkTextView creates a separate text window and
+        // so the background should not be transparent.
+        gtk_style_context_add_class(style, GTK_STYLE_CLASS_GRIP);
+      }
+      return style;
+    }
     case MOZ_GTK_FRAME_BORDER:
       return GetWidgetRootStyle(MOZ_GTK_FRAME);
     case MOZ_GTK_TREEVIEW_VIEW:
diff --git a/widget/gtk/gtk3drawing.cpp b/widget/gtk/gtk3drawing.cpp
index fb95b4cc4..c592fa51c 100644
--- a/widget/gtk/gtk3drawing.cpp
+++ b/widget/gtk/gtk3drawing.cpp
@@ -36,6 +36,10 @@ static gboolean is_initialized;
 static gint
 moz_gtk_get_tab_thickness(GtkStyleContext *style);
 
+static gint
+moz_gtk_menu_item_paint(WidgetNodeType widget, cairo_t *cr, GdkRectangle* rect,
+                        GtkWidgetState* state, GtkTextDirection direction);
+
 // GetStateFlagsFromGtkWidgetState() can be safely used for the specific
 // GtkWidgets that set both prelight and active flags.  For other widgets,
 // either the GtkStateFlags or Gecko's GtkWidgetState need to be carefully
@@ -167,7 +171,7 @@ moz_gtk_menuitem_get_horizontal_padding(gint* horizontal_padding)
 gint
 moz_gtk_checkmenuitem_get_horizontal_padding(gint* horizontal_padding)
 {
-    GtkStyleContext *style = ClaimStyleContext(MOZ_GTK_CHECKMENUITEM_CONTAINER);
+    GtkStyleContext *style = ClaimStyleContext(MOZ_GTK_CHECKMENUITEM);
     gtk_style_context_get_style(style,
                                 "horizontal-padding", horizontal_padding,
                                 nullptr);
@@ -463,7 +467,7 @@ moz_gtk_get_widget_min_size(WidgetNodeType aGtkWidgetType, int* width,
 }
 
 static void
-moz_gtk_rectangle_inset(GdkRectangle* rect, GtkBorder& aBorder)
+Inset(GdkRectangle* rect, GtkBorder& aBorder)
 {
     MOZ_ASSERT(rect);
     rect->x += aBorder.left;
@@ -472,17 +476,29 @@ moz_gtk_rectangle_inset(GdkRectangle* rect, GtkBorder& aBorder)
     rect->height -= aBorder.top + aBorder.bottom;
 }
 
-/* Subtracting margin is used to inset drawing of element which can have margins,
- * like scrollbar, scrollbar's trough, thumb and scrollbar's button */
+// Inset a rectangle by the margins specified in a style context.
 static void
-moz_gtk_subtract_margin(GtkStyleContext* style, GdkRectangle* rect)
+InsetByMargin(GdkRectangle* rect, GtkStyleContext* style)
 {
     MOZ_ASSERT(rect);
     GtkBorder margin;
 
     gtk_style_context_get_margin(style, gtk_style_context_get_state(style),
                                  &margin);
-    moz_gtk_rectangle_inset(rect, margin);
+    Inset(rect, margin);
+}
+
+// Inset a rectangle by the border and padding specified in a style context.
+static void
+InsetByBorderPadding(GdkRectangle* rect, GtkStyleContext* style)
+{
+    GtkStateFlags state = gtk_style_context_get_state(style);
+    GtkBorder padding, border;
+
+    gtk_style_context_get_padding(style, state, &padding);
+    Inset(rect, padding);
+    gtk_style_context_get_border(style, state, &border);
+    Inset(rect, border);
 }
 
 static gint
@@ -528,7 +544,7 @@ moz_gtk_scrollbar_button_paint(cairo_t *cr, const GdkRectangle* aRect,
     if (gtk_check_version(3,20,0) == nullptr) {
       // The "trough-border" is not used since GTK 3.20.  The stepper margin
       // box occupies the full width of the "contents" gadget content box.
-      moz_gtk_subtract_margin(style, &rect);
+      InsetByMargin(&rect, style);
     } else {
       // Scrollbar button has to be inset by trough_border because its DOM
       // element is filling width of vertical scrollbar's track (or height
@@ -601,7 +617,7 @@ moz_gtk_draw_styled_frame(GtkStyleContext* style, cairo_t *cr,
 {
     GdkRectangle rect = *aRect;
     if (gtk_check_version(3, 6, 0) == nullptr) {
-        moz_gtk_subtract_margin(style, &rect);
+        InsetByMargin(&rect, style);
     }
     gtk_render_background(style, cr, rect.x, rect.y, rect.width, rect.height);
     gtk_render_frame(style, cr, rect.x, rect.y, rect.width, rect.height);
@@ -656,7 +672,7 @@ moz_gtk_scrollbar_thumb_paint(WidgetNodeType widget,
 
     GdkRectangle rect = *aRect;
     GtkStyleContext* style = ClaimStyleContext(widget, direction, state_flags);
-    moz_gtk_subtract_margin(style, &rect);
+    InsetByMargin(&rect, style);
 
     gtk_render_slider(style, cr,
                       rect.x,
@@ -857,7 +873,7 @@ moz_gtk_entry_paint(cairo_t *cr, GdkRectangle* rect,
 }
 
 static gint
-moz_gtk_text_view_paint(cairo_t *cr, GdkRectangle* rect,
+moz_gtk_text_view_paint(cairo_t *cr, GdkRectangle* aRect,
                         GtkWidgetState* state,
                         GtkTextDirection direction)
 {
@@ -874,24 +890,24 @@ moz_gtk_text_view_paint(cairo_t *cr, GdkRectangle* rect,
 
     GtkStyleContext* style_frame =
         ClaimStyleContext(MOZ_GTK_SCROLLED_WINDOW, direction, state_flags);
-    gtk_render_frame(style_frame, cr, rect->x, rect->y, rect->width, rect->height);
+    gtk_render_frame(style_frame, cr,
+                     aRect->x, aRect->y, aRect->width, aRect->height);
+
+    GdkRectangle rect = *aRect;
+    InsetByBorderPadding(&rect, style_frame);
 
-    GtkBorder border, padding;
-    gtk_style_context_get_border(style_frame, state_flags, &border);
-    gtk_style_context_get_padding(style_frame, state_flags, &padding);
     ReleaseStyleContext(style_frame);
 
     GtkStyleContext* style =
         ClaimStyleContext(MOZ_GTK_TEXT_VIEW, direction, state_flags);
-
-    gint xthickness = border.left + padding.left;
-    gint ythickness = border.top + padding.top;
-
-    gtk_render_background(style, cr,
-                          rect->x + xthickness, rect->y + ythickness,
-                          rect->width - 2 * xthickness,
-                          rect->height - 2 * ythickness);
-
+    gtk_render_background(style, cr, rect.x, rect.y, rect.width, rect.height);
+    ReleaseStyleContext(style);
+    // There is a separate "text" window, which usually provides the
+    // background behind the text.  However, this is transparent in Ambiance
+    // for GTK 3.20, in which case the MOZ_GTK_TEXT_VIEW background is
+    // visible.
+    style = ClaimStyleContext(MOZ_GTK_TEXT_VIEW_TEXT, direction, state_flags);
+    gtk_render_background(style, cr, rect.x, rect.y, rect.width, rect.height);
     ReleaseStyleContext(style);
 
     return MOZ_GTK_SUCCESS;
@@ -1013,8 +1029,7 @@ moz_gtk_treeview_expander_paint(cairo_t *cr, GdkRectangle* rect,
     return MOZ_GTK_SUCCESS;
 }
 
-/* See gtk_separator_draw() for reference.
-*/
+/* See gtk_separator_draw() for reference. */
 static gint
 moz_gtk_combo_box_paint(cairo_t *cr, GdkRectangle* rect,
                         GtkWidgetState* state,
@@ -1283,6 +1298,7 @@ moz_gtk_tooltip_paint(cairo_t *cr, const GdkRectangle* aRect,
     GdkRectangle rect = *aRect;
     gtk_render_background(style, cr, rect.x, rect.y, rect.width, rect.height);
     gtk_render_frame(style, cr, rect.x, rect.y, rect.width, rect.height);
+    ReleaseStyleContext(style);
 
     // Horizontal Box drawing
     //
@@ -1292,33 +1308,26 @@ moz_gtk_tooltip_paint(cairo_t *cr, const GdkRectangle* aRect,
     // 6px margin.
     // For drawing Horizontal Box we have to inset drawing area by that 6px
     // plus its CSS margin.
-    GtkStyleContext* boxStyle =
-        CreateStyleForWidget(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0), style);
+    GtkStyleContext* boxStyle = ClaimStyleContext(MOZ_GTK_TOOLTIP_BOX, direction);
 
     rect.x += 6;
     rect.y += 6;
     rect.width -= 12;
     rect.height -= 12;
 
-    moz_gtk_subtract_margin(boxStyle, &rect);
+    InsetByMargin(&rect, boxStyle);
     gtk_render_background(boxStyle, cr, rect.x, rect.y, rect.width, rect.height);
     gtk_render_frame(boxStyle, cr, rect.x, rect.y, rect.width, rect.height);
 
     // Label drawing
-    GtkBorder padding, border;
-    gtk_style_context_get_padding(boxStyle, GTK_STATE_FLAG_NORMAL, &padding);
-    moz_gtk_rectangle_inset(&rect, padding);
-    gtk_style_context_get_border(boxStyle, GTK_STATE_FLAG_NORMAL, &border);
-    moz_gtk_rectangle_inset(&rect, border);
+    InsetByBorderPadding(&rect, boxStyle);
+    ReleaseStyleContext(boxStyle);
 
     GtkStyleContext* labelStyle =
-        CreateStyleForWidget(gtk_label_new(nullptr), boxStyle);
+        ClaimStyleContext(MOZ_GTK_TOOLTIP_BOX_LABEL, direction);
     moz_gtk_draw_styled_frame(labelStyle, cr, &rect, false);
-    g_object_unref(labelStyle);
-
-    g_object_unref(boxStyle);
+    ReleaseStyleContext(labelStyle);
 
-    ReleaseStyleContext(style);
     return MOZ_GTK_SUCCESS;
 }
 
@@ -1327,17 +1336,9 @@ moz_gtk_resizer_paint(cairo_t *cr, GdkRectangle* rect,
                       GtkWidgetState* state,
                       GtkTextDirection direction)
 {
-    GtkStyleContext* style;
-
-    // gtk_render_handle() draws a background, so use GtkTextView and its
-    // GTK_STYLE_CLASS_VIEW to match the background with textarea elements.
-    // The resizer is drawn with shaded variants of the background color, and
-    // so a transparent background would lead to a transparent resizer.
-    style = ClaimStyleContext(MOZ_GTK_TEXT_VIEW, GTK_TEXT_DIR_LTR,
-                              GetStateFlagsFromGtkWidgetState(state));
-    // TODO - we need to save/restore style when gtk 3.20 CSS node path
-    // is used
-    gtk_style_context_add_class(style, GTK_STYLE_CLASS_GRIP);
+    GtkStyleContext* style =
+        ClaimStyleContext(MOZ_GTK_RESIZER, GTK_TEXT_DIR_LTR,
+                          GetStateFlagsFromGtkWidgetState(state));
 
     // Workaround unico not respecting the text direction for resizers.
     // See bug 1174248.
@@ -1384,17 +1385,8 @@ moz_gtk_progress_chunk_paint(cairo_t *cr, GdkRectangle* rect,
                              GtkTextDirection direction,
                              WidgetNodeType widget)
 {
-    GtkStyleContext* style;
-
-    if (gtk_check_version(3, 20, 0) != nullptr) {
-      /* Ask for MOZ_GTK_PROGRESS_TROUGH instead of MOZ_GTK_PROGRESSBAR
-       * because ClaimStyleContext() saves/restores that style */
-      style = ClaimStyleContext(MOZ_GTK_PROGRESS_TROUGH, direction);
-      gtk_style_context_remove_class(style, GTK_STYLE_CLASS_TROUGH);
-      gtk_style_context_add_class(style, GTK_STYLE_CLASS_PROGRESSBAR);
-    } else {
-      style = ClaimStyleContext(MOZ_GTK_PROGRESS_CHUNK, direction);
-    }
+    GtkStyleContext* style =
+        ClaimStyleContext(MOZ_GTK_PROGRESS_CHUNK, direction);
 
     if (widget == MOZ_GTK_PROGRESS_CHUNK_INDETERMINATE ||
         widget == MOZ_GTK_PROGRESS_CHUNK_VERTICAL_INDETERMINATE) {
@@ -1778,6 +1770,13 @@ static gint
 moz_gtk_menu_separator_paint(cairo_t *cr, GdkRectangle* rect,
                              GtkTextDirection direction)
 {
+    GtkWidgetState defaultState = { 0 };
+    moz_gtk_menu_item_paint(MOZ_GTK_MENUSEPARATOR, cr, rect,
+                            &defaultState, direction);
+
+    if (gtk_get_minor_version() >= 20)
+        return MOZ_GTK_SUCCESS;
+
     GtkStyleContext* style;
     gboolean wide_separators;
     gint separator_height;
@@ -1825,36 +1824,39 @@ moz_gtk_menu_item_paint(WidgetNodeType widget, cairo_t *cr, GdkRectangle* rect,
                         GtkWidgetState* state, GtkTextDirection direction)
 {
     gint x, y, w, h;
+    guint minorVersion = gtk_get_minor_version();
+    GtkStateFlags state_flags = GetStateFlagsFromGtkWidgetState(state);
 
-    if (state->inHover && !state->disabled) {   
-        GtkStateFlags state_flags = GetStateFlagsFromGtkWidgetState(state);
-        GtkStyleContext* style =
-            ClaimStyleContext(widget, direction, state_flags);
-
-        bool pre_3_6 = gtk_check_version(3, 6, 0) != nullptr;
-        if (pre_3_6) {
-            // GTK+ 3.4 saves the style context and adds the menubar class to
-            // menubar children, but does each of these only when drawing, not
-            // during layout.
-            gtk_style_context_save(style);
-            if (widget == MOZ_GTK_MENUBARITEM) {
-                gtk_style_context_add_class(style, GTK_STYLE_CLASS_MENUBAR);
-            }
+    // GTK versions prior to 3.8 render the background and frame only when not
+    // a separator and in hover prelight.
+    if (minorVersion < 8 && (widget == MOZ_GTK_MENUSEPARATOR ||
+                             !(state_flags & GTK_STATE_FLAG_PRELIGHT)))
+        return MOZ_GTK_SUCCESS;
+
+    GtkStyleContext* style = ClaimStyleContext(widget, direction, state_flags);
+
+    if (minorVersion < 6) {
+        // GTK+ 3.4 saves the style context and adds the menubar class to
+        // menubar children, but does each of these only when drawing, not
+        // during layout.
+        gtk_style_context_save(style);
+        if (widget == MOZ_GTK_MENUBARITEM) {
+            gtk_style_context_add_class(style, GTK_STYLE_CLASS_MENUBAR);
         }
+	}
 
-        x = rect->x;
-        y = rect->y;
-        w = rect->width;
-        h = rect->height;
+    x = rect->x;
+    y = rect->y;
+    w = rect->width;
+    h = rect->height;
 
-        gtk_render_background(style, cr, x, y, w, h);
-        gtk_render_frame(style, cr, x, y, w, h);
+    gtk_render_background(style, cr, x, y, w, h);
+    gtk_render_frame(style, cr, x, y, w, h);
 
-        if (pre_3_6) {
-            gtk_style_context_restore(style);
-        }
-        ReleaseStyleContext(style);
+    if (minorVersion < 6) {
+        gtk_style_context_restore(style);
     }
+    ReleaseStyleContext(style);
 
     return MOZ_GTK_SUCCESS;
 }
@@ -1874,16 +1876,16 @@ moz_gtk_menu_arrow_paint(cairo_t *cr, GdkRectangle* rect,
     return MOZ_GTK_SUCCESS;
 }
 
-// See gtk_real_check_menu_item_draw_indicator() for reference.
+// For reference, see gtk_check_menu_item_size_allocate() in GTK versions after
+// 3.20 and gtk_real_check_menu_item_draw_indicator() in earlier versions.
 static gint
-moz_gtk_check_menu_item_paint(cairo_t *cr, GdkRectangle* rect,
+moz_gtk_check_menu_item_paint(WidgetNodeType widgetType,
+                              cairo_t *cr, GdkRectangle* rect,
                               GtkWidgetState* state,
-                              gboolean checked, gboolean isradio,
-                              GtkTextDirection direction)
+                              gboolean checked, GtkTextDirection direction)
 {
     GtkStateFlags state_flags = GetStateFlagsFromGtkWidgetState(state);
     GtkStyleContext* style;
-    GtkBorder padding;
     gint indicator_size, horizontal_padding;
     gint x, y;
 
@@ -1893,35 +1895,44 @@ moz_gtk_check_menu_item_paint(cairo_t *cr, GdkRectangle* rect,
       state_flags = static_cast<GtkStateFlags>(state_flags|checkbox_check_state);
     }
 
-    style = ClaimStyleContext(isradio ? MOZ_GTK_RADIOMENUITEM_CONTAINER :
-                                        MOZ_GTK_CHECKMENUITEM_CONTAINER,
-                              direction);
+    bool pre_3_20 = gtk_get_minor_version() < 20;
+    gint offset;
+    style = ClaimStyleContext(widgetType, direction);
     gtk_style_context_get_style(style,
                                 "indicator-size", &indicator_size,
                                 "horizontal-padding", &horizontal_padding,
                                 NULL);
+    if (pre_3_20) {
+        GtkBorder padding;
+        gtk_style_context_get_padding(style, state_flags, &padding);
+        offset = horizontal_padding + padding.left + 2;
+    } else {
+        GdkRectangle r = { 0 };
+        InsetByMargin(&r, style);
+        InsetByBorderPadding(&r, style);
+        offset = r.x;
+    }
     ReleaseStyleContext(style);
 
-    style = ClaimStyleContext(isradio ? MOZ_GTK_RADIOMENUITEM :
-                                        MOZ_GTK_CHECKMENUITEM,
-                              direction, state_flags);
-    gtk_style_context_get_padding(style, state_flags, &padding);
-    gint offset = padding.left + 2;
+    bool isRadio = (widgetType == MOZ_GTK_RADIOMENUITEM);
+    WidgetNodeType indicatorType = isRadio ? MOZ_GTK_RADIOMENUITEM_INDICATOR
+                                           : MOZ_GTK_CHECKMENUITEM_INDICATOR;
+    style = ClaimStyleContext(indicatorType, direction, state_flags);
 
     if (direction == GTK_TEXT_DIR_RTL) {
-        x = rect->width - indicator_size - offset - horizontal_padding;
+        x = rect->width - indicator_size - offset;
     }
     else {
-        x = rect->x + offset + horizontal_padding;
+        x = rect->x + offset;
     }
     y = rect->y + (rect->height - indicator_size) / 2;
 
-    if (gtk_check_version(3, 20, 0) == nullptr) {
+    if (!pre_3_20) {
         gtk_render_background(style, cr, x, y, indicator_size, indicator_size);
         gtk_render_frame(style, cr, x, y, indicator_size, indicator_size);
     }
 
-    if (isradio) {
+    if (isRadio) {
       gtk_render_option(style, cr, x, y, indicator_size, indicator_size);
     } else {
       gtk_render_check(style, cr, x, y, indicator_size, indicator_size);
@@ -2166,12 +2177,15 @@ moz_gtk_get_widget_border(WidgetNodeType widget, gint* left, gint* top,
         {
             // Bug 1274143 for MOZ_GTK_MENUBARITEM
             WidgetNodeType type =
-                widget == MOZ_GTK_MENUBARITEM || widget == MOZ_GTK_MENUITEM ?
-                MOZ_GTK_MENUITEM : MOZ_GTK_CHECKMENUITEM_CONTAINER;
+                widget == MOZ_GTK_MENUBARITEM ? MOZ_GTK_MENUITEM : widget;
             style = ClaimStyleContext(type);
 
-            moz_gtk_add_style_padding(style, left, top, right, bottom);
-
+            if (gtk_get_minor_version() < 20) {
+                moz_gtk_add_style_padding(style, left, top, right, bottom);
+            } else {
+                moz_gtk_add_margin_border_padding(style,
+                                                  left, top, right, bottom);
+            }
             ReleaseStyleContext(style);
             return MOZ_GTK_SUCCESS;
         }
@@ -2180,7 +2194,6 @@ moz_gtk_get_widget_border(WidgetNodeType widget, gint* left, gint* top,
         break;
     case MOZ_GTK_TOOLTIP:
         {
-            style = ClaimStyleContext(MOZ_GTK_TOOLTIP);
             // In GTK 3 there are 6 pixels of additional margin around the box.
             // See details there:
             // https://github.com/GNOME/gtk/blob/5ea69a136bd7e4970b3a800390e20314665aaed2/gtk/ui/gtktooltipwindow.ui#L11
@@ -2189,21 +2202,16 @@ moz_gtk_get_widget_border(WidgetNodeType widget, gint* left, gint* top,
             // We also need to add margin/padding/borders from Tooltip content.
             // Tooltip contains horizontal box, where icon and label is put.
             // We ignore icon as long as we don't have support for it.
-            GtkStyleContext* boxStyle =
-                CreateStyleForWidget(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0),
-                                     style);
+            GtkStyleContext* boxStyle = ClaimStyleContext(MOZ_GTK_TOOLTIP_BOX);
             moz_gtk_add_margin_border_padding(boxStyle,
                                               left, top, right, bottom);
+            ReleaseStyleContext(boxStyle);
 
-            GtkStyleContext* labelStyle =
-                CreateStyleForWidget(gtk_label_new(nullptr), boxStyle);
+            GtkStyleContext* labelStyle = ClaimStyleContext(MOZ_GTK_TOOLTIP_BOX_LABEL);
             moz_gtk_add_margin_border_padding(labelStyle,
                                               left, top, right, bottom);
+            ReleaseStyleContext(labelStyle);
 
-            g_object_unref(labelStyle);
-            g_object_unref(boxStyle);
-
-            ReleaseStyleContext(style);
             return MOZ_GTK_SUCCESS;
         }
     case MOZ_GTK_SCROLLBAR_VERTICAL:
@@ -2492,11 +2500,11 @@ void
 moz_gtk_get_scale_metrics(GtkOrientation orient, gint* scale_width,
                           gint* scale_height)
 {
-  WidgetNodeType widget = (orient == GTK_ORIENTATION_HORIZONTAL) ?
-                           MOZ_GTK_SCALE_HORIZONTAL :
-                           MOZ_GTK_SCALE_VERTICAL;
-
   if (gtk_check_version(3, 20, 0) != nullptr) {
+      WidgetNodeType widget = (orient == GTK_ORIENTATION_HORIZONTAL) ?
+                               MOZ_GTK_SCALE_HORIZONTAL :
+                               MOZ_GTK_SCALE_VERTICAL;
+
       gint thumb_length, thumb_height, trough_border;
       moz_gtk_get_scalethumb_metrics(orient, &thumb_length, &thumb_height);
 
@@ -2512,12 +2520,10 @@ moz_gtk_get_scale_metrics(GtkOrientation orient, gint* scale_width,
       }
       ReleaseStyleContext(style);
   } else {
-      GtkStyleContext* style = ClaimStyleContext(widget);
-      gtk_style_context_get(style, gtk_style_context_get_state(style),
-                            "min-width", scale_width,
-                            "min-height", scale_height,
-                            nullptr);
-      ReleaseStyleContext(style);
+      WidgetNodeType widget = (orient == GTK_ORIENTATION_HORIZONTAL) ?
+                               MOZ_GTK_SCALE_TROUGH_HORIZONTAL :
+                               MOZ_GTK_SCALE_TROUGH_VERTICAL;
+      moz_gtk_get_widget_min_size(widget, scale_width, scale_height);
   }
 }
 
@@ -2540,10 +2546,27 @@ moz_gtk_get_scalethumb_metrics(GtkOrientation orient, gint* thumb_length, gint*
                                MOZ_GTK_SCALE_THUMB_HORIZONTAL:
                                MOZ_GTK_SCALE_THUMB_VERTICAL;
       GtkStyleContext* style = ClaimStyleContext(widget);
-      gtk_style_context_get(style, gtk_style_context_get_state(style),
-                            "min-width", thumb_length,
-                            "min-height", thumb_height,
+      gint min_width, min_height;
+      GtkStateFlags state = gtk_style_context_get_state(style);
+      gtk_style_context_get(style, state,
+                            "min-width", &min_width,
+                            "min-height", &min_height,
                              nullptr);
+      GtkBorder margin;
+      gtk_style_context_get_margin(style, state, &margin);
+      gint margin_width = margin.left + margin.right;
+      gint margin_height = margin.top + margin.bottom;
+
+      // Negative margin of slider element also determines its minimal size
+      // so use bigger of those two values.
+      if (min_width < -margin_width)
+          min_width = -margin_width;
+      if (min_height < -margin_height)
+          min_height = -margin_height;
+
+      *thumb_length = min_width;
+      *thumb_height = min_height;
+
       ReleaseStyleContext(style);
   }
 
@@ -2786,10 +2809,8 @@ moz_gtk_widget_paint(WidgetNodeType widget, cairo_t *cr,
         break;
     case MOZ_GTK_CHECKMENUITEM:
     case MOZ_GTK_RADIOMENUITEM:
-        return moz_gtk_check_menu_item_paint(cr, rect, state,
-                                             (gboolean) flags,
-                                             (widget == MOZ_GTK_RADIOMENUITEM),
-                                             direction);
+        return moz_gtk_check_menu_item_paint(widget, cr, rect, state,
+                                             (gboolean) flags, direction);
         break;
     case MOZ_GTK_SPLITTER_HORIZONTAL:
         return moz_gtk_vpaned_paint(cr, rect, state);
diff --git a/widget/gtk/gtkdrawing.h b/widget/gtk/gtkdrawing.h
index 9bbfdefe9..7db5db043 100644
--- a/widget/gtk/gtkdrawing.h
+++ b/widget/gtk/gtkdrawing.h
@@ -145,8 +145,11 @@ typedef enum {
   MOZ_GTK_ENTRY,
   /* Paints a GtkExpander. */
   MOZ_GTK_EXPANDER,
-  /* Paints a GtkTextView. */
+  /* Paints a GtkTextView or gets the style context corresponding to the
+     root node of a GtkTextView. */
   MOZ_GTK_TEXT_VIEW,
+  /* The "text" window or node of a GtkTextView */
+  MOZ_GTK_TEXT_VIEW_TEXT,
   /* Paints a GtkOptionMenu. */
   MOZ_GTK_DROPDOWN,
   /* Paints a dropdown arrow (a GtkButton containing a down GtkArrow). */
@@ -160,11 +163,15 @@ typedef enum {
   MOZ_GTK_TOOLBAR_SEPARATOR,
   /* Paints a GtkToolTip */
   MOZ_GTK_TOOLTIP,
+   /* Paints a GtkBox from GtkToolTip  */
+  MOZ_GTK_TOOLTIP_BOX,
+  /* Paints a GtkLabel of GtkToolTip */
+  MOZ_GTK_TOOLTIP_BOX_LABEL,
   /* Paints a GtkFrame (e.g. a status bar panel). */
   MOZ_GTK_FRAME,
   /* Paints the border of a GtkFrame */
   MOZ_GTK_FRAME_BORDER,
-  /* Paints a resize grip for a GtkWindow */
+  /* Paints a resize grip for a GtkTextView */
   MOZ_GTK_RESIZER,
   /* Paints a GtkProgressBar. */
   MOZ_GTK_PROGRESSBAR,
@@ -211,10 +218,13 @@ typedef enum {
   /* Paints items of popup menus. */
   MOZ_GTK_MENUITEM,
   MOZ_GTK_IMAGEMENUITEM,
-  MOZ_GTK_CHECKMENUITEM_CONTAINER,
-  MOZ_GTK_RADIOMENUITEM_CONTAINER,
+  /* Paints a menuitem with check indicator, or the gets the style context for
+     a menuitem that contains a checkbox. */
   MOZ_GTK_CHECKMENUITEM,
+  /* Gets the style context for a checkbox in a check menuitem. */
+  MOZ_GTK_CHECKMENUITEM_INDICATOR,
   MOZ_GTK_RADIOMENUITEM,
+  MOZ_GTK_RADIOMENUITEM_INDICATOR,
   MOZ_GTK_MENUSEPARATOR,
   /* GtkVPaned base class */
   MOZ_GTK_SPLITTER_HORIZONTAL,
diff --git a/widget/gtk/nsLookAndFeel.cpp b/widget/gtk/nsLookAndFeel.cpp
index 53430dfbb..d2b82e495 100644
--- a/widget/gtk/nsLookAndFeel.cpp
+++ b/widget/gtk/nsLookAndFeel.cpp
@@ -47,9 +47,6 @@ nsLookAndFeel::nsLookAndFeel()
     : nsXPLookAndFeel(),
 #if (MOZ_WIDGET_GTK == 2)
       mStyle(nullptr),
-#else
-      mBackgroundStyle(nullptr),
-      mButtonStyle(nullptr),
 #endif
       mDefaultFontCached(false), mButtonFontCached(false),
       mFieldFontCached(false), mMenuFontCached(false)
@@ -61,13 +58,27 @@ nsLookAndFeel::~nsLookAndFeel()
 {
 #if (MOZ_WIDGET_GTK == 2)
     g_object_unref(mStyle);
-#else
-    g_object_unref(mBackgroundStyle);
-    g_object_unref(mButtonStyle);
 #endif
 }
 
 #if MOZ_WIDGET_GTK != 2
+// Modifies color |*aDest| as if a pattern of color |aSource| was painted with
+// CAIRO_OPERATOR_OVER to a surface with color |*aDest|.
+static void
+ApplyColorOver(const GdkRGBA& aSource, GdkRGBA* aDest) {
+    gdouble sourceCoef = aSource.alpha;
+    gdouble destCoef = aDest->alpha * (1.0 - sourceCoef);
+    gdouble resultAlpha = sourceCoef + destCoef;
+    if (resultAlpha != 0.0) { // don't divide by zero
+        destCoef /= resultAlpha;
+        sourceCoef /= resultAlpha;
+        aDest->red = sourceCoef * aSource.red + destCoef * aDest->red;
+        aDest->green = sourceCoef * aSource.green + destCoef * aDest->green;
+        aDest->blue = sourceCoef * aSource.blue + destCoef * aDest->blue;
+        aDest->alpha = resultAlpha;
+    }
+}
+
 static void
 GetLightAndDarkness(const GdkRGBA& aColor,
                     double* aLightness, double* aDarkness)
@@ -377,30 +388,39 @@ nsLookAndFeel::NativeGetColor(ColorID aID, nscolor& aColor)
         break;
 #else
         // css2  http://www.w3.org/TR/REC-CSS2/ui.html#system-colors
-    case eColorID_activeborder:
+    case eColorID_activeborder: {
         // active window border
-        gtk_style_context_get_border_color(mBackgroundStyle, 
+        GtkStyleContext *style = ClaimStyleContext(MOZ_GTK_WINDOW);
+        gtk_style_context_get_border_color(style,
                                            GTK_STATE_FLAG_NORMAL, &gdk_color);
         aColor = GDK_RGBA_TO_NS_RGBA(gdk_color);
+        ReleaseStyleContext(style);
         break;
-    case eColorID_inactiveborder:
+    }
+    case eColorID_inactiveborder: {
         // inactive window border
-        gtk_style_context_get_border_color(mBackgroundStyle, 
-                                           GTK_STATE_FLAG_INSENSITIVE, 
+        GtkStyleContext *style = ClaimStyleContext(MOZ_GTK_WINDOW);
+        gtk_style_context_get_border_color(style,
+                                           GTK_STATE_FLAG_INSENSITIVE,
                                            &gdk_color);
         aColor = GDK_RGBA_TO_NS_RGBA(gdk_color);
+        ReleaseStyleContext(style);
         break;
+    }
     case eColorID_graytext: // disabled text in windows, menus, etc.
     case eColorID_inactivecaptiontext: // text in inactive window caption
         aColor = sMenuTextInactive;
         break;
-    case eColorID_inactivecaption:
+    case eColorID_inactivecaption: {
         // inactive window caption
-        gtk_style_context_get_background_color(mBackgroundStyle, 
+        GtkStyleContext *style = ClaimStyleContext(MOZ_GTK_WINDOW);
+        gtk_style_context_get_background_color(style,
                                                GTK_STATE_FLAG_INSENSITIVE, 
                                                &gdk_color);
         aColor = GDK_RGBA_TO_NS_RGBA(gdk_color);
+        ReleaseStyleContext(style);
         break;
+    }
 #endif
     case eColorID_infobackground:
         // tooltip background color
@@ -521,18 +541,24 @@ nsLookAndFeel::NativeGetColor(ColorID aID, nscolor& aColor)
     case eColorID__moz_fieldtext:
         aColor = sMozFieldText;
         break;
-    case eColorID__moz_buttondefault:
-      // default button border color
-        gtk_style_context_get_border_color(mButtonStyle, 
+    case eColorID__moz_buttondefault: {
+        // default button border color
+        GtkStyleContext *style = ClaimStyleContext(MOZ_GTK_BUTTON);
+        gtk_style_context_get_border_color(style,
                                            GTK_STATE_FLAG_NORMAL, &gdk_color);
         aColor = GDK_RGBA_TO_NS_RGBA(gdk_color);
+        ReleaseStyleContext(style);
         break;
-    case eColorID__moz_buttonhoverface:
-        gtk_style_context_get_background_color(mButtonStyle, 
+    }
+    case eColorID__moz_buttonhoverface: {
+        GtkStyleContext *style = ClaimStyleContext(MOZ_GTK_BUTTON);
+        gtk_style_context_get_background_color(style, 
                                                GTK_STATE_FLAG_PRELIGHT, 
                                                &gdk_color);
         aColor = GDK_RGBA_TO_NS_RGBA(gdk_color);
+        ReleaseStyleContext(style);
         break;
+    }
     case eColorID__moz_buttonhovertext:
         aColor = sButtonHoverText;
         break;
@@ -1029,16 +1055,6 @@ nsLookAndFeel::GetFontImpl(FontID aID, nsString& aFontName,
   return true;
 }
 
-#if (MOZ_WIDGET_GTK == 3)
-static GtkStyleContext*
-create_context(GtkWidgetPath *path)
-{
-    GtkStyleContext *style = gtk_style_context_new();
-    gtk_style_context_set_path(style, path);
-    return(style);
-}
-#endif
-
 void
 nsLookAndFeel::Init()
 {
@@ -1129,78 +1145,55 @@ nsLookAndFeel::Init()
         g_object_set(settings, dark_setting, FALSE, nullptr);
     }
 
-    GtkWidgetPath *path = gtk_widget_path_new();
-    gtk_widget_path_append_type(path, GTK_TYPE_WINDOW);
-
-    mBackgroundStyle = create_context(path);
-    gtk_style_context_add_class(mBackgroundStyle, GTK_STYLE_CLASS_BACKGROUND);
-
-    mButtonStyle = create_context(path);
-    gtk_style_context_add_class(mButtonStyle, GTK_STYLE_CLASS_BUTTON); 
-
     // Scrollbar colors
-    style = create_context(path);
-    gtk_style_context_add_class(style, GTK_STYLE_CLASS_SCROLLBAR);
-    gtk_style_context_add_class(style, GTK_STYLE_CLASS_TROUGH);
+    style = ClaimStyleContext(MOZ_GTK_SCROLLBAR_TROUGH_VERTICAL);
     gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sMozScrollbar = GDK_RGBA_TO_NS_RGBA(color);
-    g_object_unref(style);
+    ReleaseStyleContext(style);
 
     // Window colors
-    style = create_context(path);
-    gtk_style_context_save(style);
-    gtk_style_context_add_class(style, GTK_STYLE_CLASS_BACKGROUND);
+    style = ClaimStyleContext(MOZ_GTK_WINDOW);
     gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sMozWindowBackground = GDK_RGBA_TO_NS_RGBA(color);
     gtk_style_context_get_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sMozWindowText = GDK_RGBA_TO_NS_RGBA(color);
-    gtk_style_context_restore(style);
-    g_object_unref(style);
+    ReleaseStyleContext(style);
 
     // tooltip foreground and background
     style = ClaimStyleContext(MOZ_GTK_TOOLTIP);
     gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sInfoBackground = GDK_RGBA_TO_NS_RGBA(color);
-    {
-        GtkStyleContext* boxStyle =
-            CreateStyleForWidget(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0),
-                                 style);
-        GtkStyleContext* labelStyle =
-            CreateStyleForWidget(gtk_label_new(nullptr), boxStyle);
-        gtk_style_context_get_color(labelStyle, GTK_STATE_FLAG_NORMAL, &color);
-        g_object_unref(labelStyle);
-        g_object_unref(boxStyle);
-    }
-    sInfoText = GDK_RGBA_TO_NS_RGBA(color);
     ReleaseStyleContext(style);
 
-    // menu foreground & menu background
-    GtkWidget *accel_label = gtk_accel_label_new("M");
-    GtkWidget *menuitem = gtk_menu_item_new();
-    GtkWidget *menu = gtk_menu_new();
-
-    g_object_ref_sink(menu);
-
-    gtk_container_add(GTK_CONTAINER(menuitem), accel_label);
-    gtk_menu_shell_append(GTK_MENU_SHELL(menu), menuitem);
-
-    style = gtk_widget_get_style_context(accel_label);
+    style = ClaimStyleContext(MOZ_GTK_TOOLTIP_BOX_LABEL);
     gtk_style_context_get_color(style, GTK_STATE_FLAG_NORMAL, &color);
-    sMenuText = GDK_RGBA_TO_NS_RGBA(color);
-    gtk_style_context_get_color(style, GTK_STATE_FLAG_INSENSITIVE, &color);
-    sMenuTextInactive = GDK_RGBA_TO_NS_RGBA(color);
+    sInfoText = GDK_RGBA_TO_NS_RGBA(color);
+    ReleaseStyleContext(style);
 
-    style = gtk_widget_get_style_context(menu);
+    style = ClaimStyleContext(MOZ_GTK_MENUITEM);
+    {
+        GtkStyleContext* accelStyle =
+            CreateStyleForWidget(gtk_accel_label_new("M"), style);
+        gtk_style_context_get_color(accelStyle, GTK_STATE_FLAG_NORMAL, &color);
+        sMenuText = GDK_RGBA_TO_NS_RGBA(color);
+        gtk_style_context_get_color(accelStyle, GTK_STATE_FLAG_INSENSITIVE, &color);
+        sMenuTextInactive = GDK_RGBA_TO_NS_RGBA(color);
+        g_object_unref(accelStyle);
+    }
+    ReleaseStyleContext(style);
+
+    style = ClaimStyleContext(MOZ_GTK_MENUPOPUP);
     gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sMenuBackground = GDK_RGBA_TO_NS_RGBA(color);
+    ReleaseStyleContext(style);
 
-    style = gtk_widget_get_style_context(menuitem);
+    style = ClaimStyleContext(MOZ_GTK_MENUITEM);
     gtk_style_context_get_background_color(style, GTK_STATE_FLAG_PRELIGHT, &color);
     sMenuHover = GDK_RGBA_TO_NS_RGBA(color);
     gtk_style_context_get_color(style, GTK_STATE_FLAG_PRELIGHT, &color);
     sMenuHoverText = GDK_RGBA_TO_NS_RGBA(color);
 
-    g_object_unref(menu);
+    ReleaseStyleContext(style);
 #endif
 
     // button styles
@@ -1211,9 +1204,6 @@ nsLookAndFeel::Init()
     GtkWidget *combobox = gtk_combo_box_new();
     GtkWidget *comboboxLabel = gtk_label_new("M");
     gtk_container_add(GTK_CONTAINER(combobox), comboboxLabel);
-#else
-    GtkWidget *combobox = gtk_combo_box_new_with_entry();
-    GtkWidget *comboboxLabel = gtk_bin_get_child(GTK_BIN(combobox));
 #endif
     GtkWidget *window = gtk_window_new(GTK_WINDOW_POPUP);
     GtkWidget *treeView = gtk_tree_view_new();
@@ -1227,7 +1217,9 @@ nsLookAndFeel::Init()
     gtk_container_add(GTK_CONTAINER(parent), button);
     gtk_container_add(GTK_CONTAINER(parent), treeView);
     gtk_container_add(GTK_CONTAINER(parent), linkButton);
+#if (MOZ_WIDGET_GTK == 2)
     gtk_container_add(GTK_CONTAINER(parent), combobox);
+#endif
     gtk_container_add(GTK_CONTAINER(parent), menuBar);
     gtk_menu_shell_append(GTK_MENU_SHELL(menuBar), menuBarItem);
     gtk_container_add(GTK_CONTAINER(window), parent);
@@ -1310,11 +1302,19 @@ nsLookAndFeel::Init()
     }
 #else
     // Text colors
-    style = gtk_widget_get_style_context(textView);
-    gtk_style_context_save(style);
-    gtk_style_context_add_class(style, GTK_STYLE_CLASS_VIEW);
-    gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL, &color);
-    sMozFieldBackground = GDK_RGBA_TO_NS_RGBA(color);
+    GdkRGBA bgColor;
+    // If the text window background is translucent, then the background of
+    // the textview root node is visible.
+    style = ClaimStyleContext(MOZ_GTK_TEXT_VIEW);
+    gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL,
+                                           &bgColor);
+    ReleaseStyleContext(style);
+
+    style = ClaimStyleContext(MOZ_GTK_TEXT_VIEW_TEXT);
+    gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL,
+                                           &color);
+    ApplyColorOver(color, &bgColor);
+    sMozFieldBackground = GDK_RGBA_TO_NS_RGBA(bgColor);
     gtk_style_context_get_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sMozFieldText = GDK_RGBA_TO_NS_RGBA(color);
 
@@ -1327,26 +1327,34 @@ nsLookAndFeel::Init()
         static_cast<GtkStateFlags>(GTK_STATE_FLAG_FOCUSED|GTK_STATE_FLAG_SELECTED),
         &color);
     sTextSelectedText = GDK_RGBA_TO_NS_RGBA(color);
-    gtk_style_context_restore(style);
+    ReleaseStyleContext(style);
 
-    // Button text, background, border
-    style = gtk_widget_get_style_context(label);
-    gtk_style_context_get_color(style, GTK_STATE_FLAG_NORMAL, &color);
-    sButtonText = GDK_RGBA_TO_NS_RGBA(color);
-    gtk_style_context_get_color(style, GTK_STATE_FLAG_PRELIGHT, &color);
-    sButtonHoverText = GDK_RGBA_TO_NS_RGBA(color);
+    // Button text color
+    style = ClaimStyleContext(MOZ_GTK_BUTTON);
+    {
+        GtkStyleContext* labelStyle =
+            CreateStyleForWidget(gtk_label_new("M"), style);
+        gtk_style_context_get_color(labelStyle, GTK_STATE_FLAG_NORMAL, &color);
+        sButtonText = GDK_RGBA_TO_NS_RGBA(color);
+        gtk_style_context_get_color(labelStyle, GTK_STATE_FLAG_PRELIGHT, &color);
+        sButtonHoverText = GDK_RGBA_TO_NS_RGBA(color);
+        g_object_unref(labelStyle);
+    }
+    ReleaseStyleContext(style);
 
     // Combobox text color
-    style = gtk_widget_get_style_context(comboboxLabel);
+    style = ClaimStyleContext(MOZ_GTK_COMBOBOX_ENTRY_TEXTAREA);
     gtk_style_context_get_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sComboBoxText = GDK_RGBA_TO_NS_RGBA(color);
+    ReleaseStyleContext(style);
 
     // Menubar text and hover text colors    
-    style = gtk_widget_get_style_context(menuBarItem);
+    style = ClaimStyleContext(MOZ_GTK_MENUBARITEM);
     gtk_style_context_get_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sMenuBarText = GDK_RGBA_TO_NS_RGBA(color);
     gtk_style_context_get_color(style, GTK_STATE_FLAG_PRELIGHT, &color);
     sMenuBarHoverText = GDK_RGBA_TO_NS_RGBA(color);
+    ReleaseStyleContext(style);
 
     // GTK's guide to fancy odd row background colors:
     // 1) Check if a theme explicitly defines an odd row color
@@ -1354,7 +1362,7 @@ nsLookAndFeel::Init()
     //    slightly by a hardcoded value (gtkstyle.c)
     // 3) If neither are defined, take the base background color and
     //    darken that by a hardcoded value
-    style = gtk_widget_get_style_context(treeView);
+    style = ClaimStyleContext(MOZ_GTK_TREEVIEW);
 
     // Get odd row background color
     gtk_style_context_save(style);
@@ -1362,8 +1370,7 @@ nsLookAndFeel::Init()
     gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL, &color);
     sOddCellBackground = GDK_RGBA_TO_NS_RGBA(color);
     gtk_style_context_restore(style);
-
-    gtk_widget_path_free(path);
+    ReleaseStyleContext(style);
 
     // GtkFrame has a "border" subnode on which Adwaita draws the border.
     // Some themes do not draw on this node but draw a border on the widget
@@ -1448,12 +1455,6 @@ nsLookAndFeel::RefreshImpl()
 #if (MOZ_WIDGET_GTK == 2)
     g_object_unref(mStyle);
     mStyle = nullptr;
-#else
-    g_object_unref(mBackgroundStyle);
-    g_object_unref(mButtonStyle);
-
-    mBackgroundStyle = nullptr;
-    mButtonStyle = nullptr;
 #endif
 
     Init();
diff --git a/widget/gtk/nsLookAndFeel.h b/widget/gtk/nsLookAndFeel.h
index 9058250b9..726859b41 100644
--- a/widget/gtk/nsLookAndFeel.h
+++ b/widget/gtk/nsLookAndFeel.h
@@ -33,9 +33,6 @@ public:
 protected:
 #if (MOZ_WIDGET_GTK == 2)
     struct _GtkStyle *mStyle;
-#else
-    struct _GtkStyleContext *mBackgroundStyle;
-    struct _GtkStyleContext *mButtonStyle;
 #endif
 
     // Cached fonts
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index d97b35002..e4e69c1b4 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -6627,6 +6627,22 @@ nsWindow::GetDragInfo(WidgetMouseEvent* aMouseEvent,
         return false;
     }
 
+    if (mIsX11Display) {
+      // Workaround for https://bugzilla.gnome.org/show_bug.cgi?id=789054
+      // To avoid crashes disable double-click on WM without _NET_WM_MOVERESIZE.
+      // See _should_perform_ewmh_drag() at gdkwindow-x11.c
+      GdkScreen* screen = gdk_window_get_screen(gdk_window);
+      GdkAtom atom = gdk_atom_intern("_NET_WM_MOVERESIZE", FALSE);
+      if (!gdk_x11_screen_supports_net_wm_hint(screen, atom)) {
+          static unsigned int lastTimeStamp = 0;
+          if (lastTimeStamp != aMouseEvent->mTime) {
+              lastTimeStamp = aMouseEvent->mTime;
+          } else {
+              return false;
+          }
+      }
+    }
+
     // FIXME: It would be nice to have the widget position at the time
     // of the event, but it's relatively unlikely that the widget has
     // moved since the mousedown.  (On the other hand, it's quite likely