gtkwidget: Widgets are now always double-buffered

gtk_widget_set_double_buffered is now deprecated, and we don't support
non-double-buffered widgets. This means that under normal circumstances,
paints are never outside of a begin_paint / end_paint sequence, which
natively-double-buffered backends like Wayland can't possibly support.

gdk/gdkwindow.c

@@ -2728,9 +2728,7 @@ gdk_window_begin_paint_rect (GdkWindow          *window,
  * #GdkEventExpose has already been cleared to the window background,
  * is already set as the clip region, and already has a backing store.
  * Therefore in most cases, application code need not call
- * gdk_window_begin_paint_region(). (You can disable the automatic
+ * gdk_window_begin_paint_region().
- * calls around expose events on a widget-by-widget basis by calling
- * gtk_widget_set_double_buffered().)
  *
  * If you call this function multiple times before calling the
  * matching gdk_window_end_paint(), the backing stores are pushed onto

gtk/gtkmain.c

@@ -1647,23 +1647,16 @@ gtk_main_do_event (GdkEvent *event)
       break;
 
     case GDK_EXPOSE:
-      if (event->any.window && gtk_widget_get_double_buffered (event_widget))
+      /* We handle exposes only on native windows, relying on the
-        {
+       * draw() handler to propagate down to non-native windows.
-	  /* We handle exposes only on native windows, relying on the
+       * This is ok now that we child windows always are considered
-	   * draw() handler to propagate down to non-native windows.
+       * (semi)transparent.
-	   * This is ok now that we child windows always are considered
+       */
-	   * (semi)transparent.
+      if (event->any.window && gdk_window_has_native (event->expose.window))
-	   */
-	  if (gdk_window_has_native (event->expose.window))
-	    {
-	      gdk_window_begin_paint_region (event->any.window, event->expose.region);
-	      gtk_widget_send_expose (event_widget, event);
-	      gdk_window_end_paint (event->any.window);
-	    }
-        }
-      else
         {
+          gdk_window_begin_paint_region (event->any.window, event->expose.region);
           gtk_widget_send_expose (event_widget, event);
+          gdk_window_end_paint (event->any.window);
         }
       break;
 

gtk/gtkwidget.c

@@ -432,7 +432,6 @@ struct _GtkWidgetPrivate
   guint shadowed              : 1;
   guint style_update_pending  : 1;
   guint app_paintable         : 1;
-  guint double_buffered       : 1;
   guint redraw_on_alloc       : 1;
   guint no_show_all           : 1;
   guint child_visible         : 1;
@@ -1369,6 +1368,8 @@ G_GNUC_END_IGNORE_DEPRECATIONS
    * Whether the widget is double buffered.
    *
    * Since: 2.18
+   *
+   * Deprecated: 3.14
    */
   g_object_class_install_property (gobject_class,
                                    PROP_DOUBLE_BUFFERED,
@@ -1376,7 +1377,7 @@ G_GNUC_END_IGNORE_DEPRECATIONS
                                                          P_("Double Buffered"),
                                                          P_("Whether the widget is double buffered"),
                                                          TRUE,
-                                                         GTK_PARAM_READWRITE|G_PARAM_EXPLICIT_NOTIFY));
+                                                         GTK_PARAM_READWRITE|G_PARAM_EXPLICIT_NOTIFY|G_PARAM_DEPRECATED));
 
   /**
    * GtkWidget:halign:
@@ -3811,7 +3812,6 @@ gtk_widget_set_property (GObject         *object,
         gtk_widget_queue_tooltip_query (widget);
       break;
     case PROP_DOUBLE_BUFFERED:
-      gtk_widget_set_double_buffered (widget, g_value_get_boolean (value));
       break;
     case PROP_HALIGN:
       gtk_widget_set_halign (widget, g_value_get_enum (value));
@@ -3975,7 +3975,7 @@ gtk_widget_get_property (GObject         *object,
       g_value_set_object (value, gtk_widget_get_window (widget));
       break;
     case PROP_DOUBLE_BUFFERED:
-      g_value_set_boolean (value, gtk_widget_get_double_buffered (widget));
+      g_value_set_boolean (value, TRUE);
       break;
     case PROP_HALIGN:
       g_value_set_enum (value, gtk_widget_get_halign (widget));
@@ -4377,7 +4377,6 @@ gtk_widget_init (GtkWidget *widget)
 
   priv->sensitive = TRUE;
   priv->composite_child = composite_child_stack != 0;
-  priv->double_buffered = TRUE;
   priv->redraw_on_alloc = TRUE;
   priv->alloc_needed = TRUE;
    
@@ -6963,11 +6962,8 @@ _gtk_widget_draw_windows (GdkWindow *window,
     {
       gdk_window_get_user_data (window, (gpointer *) &widget);
 
-      /* Only clear bg if double bufferer. This is what we used
-	 to do before, where begin_paint() did the clearing. */
       pattern = gdk_window_get_background_pattern (window);
-      if (pattern != NULL &&
+      if (pattern != NULL)
-	  widget->priv->double_buffered)
 	{
 	  cairo_save (cr);
 	  cairo_set_source (cr, pattern);
@@ -9208,42 +9204,15 @@ gtk_widget_get_app_paintable (GtkWidget *widget)
  * @widget: a #GtkWidget
  * @double_buffered: %TRUE to double-buffer a widget
  *
- * Widgets are double buffered by default; you can use this function
+ * Widgets are always double-buffered. This function does nothing.
- * to turn off the buffering. “Double buffered” simply means that
- * gdk_window_begin_paint_region() and gdk_window_end_paint() are called
- * automatically around expose events sent to the
- * widget. gdk_window_begin_paint_region() diverts all drawing to a widget's
- * window to an offscreen buffer, and gdk_window_end_paint() draws the
- * buffer to the screen. The result is that users see the window
- * update in one smooth step, and don’t see individual graphics
- * primitives being rendered.
  *
- * In very simple terms, double buffered widgets don’t flicker,
+ * Deprecated: 3.14
- * so you would only use this function to turn off double buffering
- * if you had special needs and really knew what you were doing.
- *
- * Note: if you turn off double-buffering, you have to handle
- * expose events, since even the clearing to the background color or
- * pixmap will not happen automatically (as it is done in
- * gdk_window_begin_paint_region()).
- *
- * Since 3.10 this function only works for widgets with native
- * windows.
  **/
 void
 gtk_widget_set_double_buffered (GtkWidget *widget,
 				gboolean   double_buffered)
 {
   g_return_if_fail (GTK_IS_WIDGET (widget));
-
-  double_buffered = (double_buffered != FALSE);
-
-  if (widget->priv->double_buffered != double_buffered)
-    {
-      widget->priv->double_buffered = double_buffered;
-
-      g_object_notify (G_OBJECT (widget), "double-buffered");
-    }
 }
 
 /**
@@ -9263,7 +9232,7 @@ gtk_widget_get_double_buffered (GtkWidget *widget)
 {
   g_return_val_if_fail (GTK_IS_WIDGET (widget), FALSE);
 
-  return widget->priv->double_buffered;
+  return TRUE;
 }
 
 /**