frames: apply modified hack from Mutter/Metacity

- this will be needed for proper window decoration color updates on theme change
  when theme variants fixes are applied

- realize/unrealize functions are dropped instead of map/unmap ones, because
  we didn't change these during GTK+3 porting

- MetaFrames now has GtkWindow as parent instead of GtkInvisible, otherwise
  the hack doesn't work (revert part of 96c7256d638b8c76c8abf786ba307e82a595dd67)

adapted from:
https://github.com/GNOME/metacity/commit/ba8500663457ad9f18ebfdf405162c2cb5caf88f

3 files changed, 25 insertions, 27 deletions

diff --git a/src/ui/frames.c b/src/ui/frames.c
index 74e97a30..52001c7d 100644
--- a/src/ui/frames.c
+++ b/src/ui/frames.c
@@ -42,7 +42,7 @@
 
 #include <cairo-xlib.h>
 
-G_DEFINE_TYPE (MetaFrames, meta_frames, GTK_TYPE_INVISIBLE);
+G_DEFINE_TYPE (MetaFrames, meta_frames, GTK_TYPE_WINDOW);
 
 #define DEFAULT_INNER_BUTTON_BORDER 3
 
@@ -51,8 +51,6 @@ static void meta_frames_init       (MetaFrames      *frames);
 static void meta_frames_destroy    (GtkWidget       *object);
 static void meta_frames_finalize   (GObject         *object);
 static void meta_frames_style_updated  (GtkWidget   *widget);
-static void meta_frames_realize    (GtkWidget       *widget);
-static void meta_frames_unrealize  (GtkWidget       *widget);
 
 static void meta_frames_update_prelit_control (MetaFrames      *frames,
                                                MetaUIFrame     *frame,
@@ -131,8 +129,6 @@ meta_frames_class_init (MetaFramesClass *class)
   gobject_class->finalize = meta_frames_finalize;
   widget_class->destroy = meta_frames_destroy;
   widget_class->style_updated = meta_frames_style_updated;
-  widget_class->realize = meta_frames_realize;
-  widget_class->unrealize = meta_frames_unrealize;
 
   widget_class->draw = meta_frames_draw;
   widget_class->destroy_event = meta_frames_destroy_event;
@@ -620,12 +616,25 @@ MetaFrames*
 meta_frames_new (void)
 {
   GdkScreen *screen;
+  MetaFrames *frames;
 
   screen = gdk_display_get_default_screen (gdk_display_get_default ());
 
-  return g_object_new (META_TYPE_FRAMES,
-                       "screen", screen,
-                       NULL);
+  frames = g_object_new (META_TYPE_FRAMES,
+                         "screen", screen,
+                         "type", GTK_WINDOW_POPUP,
+                         NULL);
+
+  /* Put the window at an arbitrary offscreen location; the one place
+   * it can't be is at -100x-100, since the meta_window_new() will
+   * mistake it for a window created via meta_create_offscreen_window()
+   * and ignore it, and we need this window to get frame-synchronization
+   * messages so that GTK+'s style change handling works.
+   */
+  gtk_window_move (GTK_WINDOW (frames), -200, -200);
+  gtk_window_resize (GTK_WINDOW (frames), 1, 1);
+
+  return frames;
 }
 
 /* In order to use a style with a window it has to be attached to that
@@ -734,20 +743,6 @@ meta_frames_unmanage_window (MetaFrames *frames,
     meta_warning ("Frame 0x%lx not managed, can't unmanage\n", xwindow);
 }
 
-static void
-meta_frames_realize (GtkWidget *widget)
-{
-  if (GTK_WIDGET_CLASS (meta_frames_parent_class)->realize)
-    GTK_WIDGET_CLASS (meta_frames_parent_class)->realize (widget);
-}
-
-static void
-meta_frames_unrealize (GtkWidget *widget)
-{
-  if (GTK_WIDGET_CLASS (meta_frames_parent_class)->unrealize)
-    GTK_WIDGET_CLASS (meta_frames_parent_class)->unrealize (widget);
-}
-
 static MetaUIFrame*
 meta_frames_lookup_window (MetaFrames *frames,
                            Window      xwindow)
diff --git a/src/ui/frames.h b/src/ui/frames.h
index f1258783..ad86ee44 100644
--- a/src/ui/frames.h
+++ b/src/ui/frames.h
@@ -90,7 +90,7 @@ struct _MetaUIFrame
 
 struct _MetaFrames
 {
-  GtkInvisible parent_instance;
+  GtkWindow parent_instance;
 
   GHashTable *text_heights;
 
@@ -110,7 +110,7 @@ struct _MetaFrames
 
 struct _MetaFramesClass
 {
-  GtkInvisibleClass parent_class;
+  GtkWindowClass parent_class;
 };
 
 GType        meta_frames_get_type               (void) G_GNUC_CONST;
diff --git a/src/ui/ui.c b/src/ui/ui.c
index 0639757d..ed2c5772 100644
--- a/src/ui/ui.c
+++ b/src/ui/ui.c
@@ -271,9 +271,12 @@ meta_ui_new (Display *xdisplay,
 
   g_assert (xdisplay == GDK_DISPLAY_XDISPLAY (gdk_display_get_default ()));
   ui->frames = meta_frames_new ();
-  /* This does not actually show any widget. MetaFrames has been hacked so
-   * that showing it doesn't actually do anything. But we need the flags
-   * set for GTK to deliver events properly. */
+  /* GTK+ needs the frame-sync protocol to work in order to properly
+   * handle style changes. This means that the dummy widget we create
+   * to get the style for title bars actually needs to be mapped
+   * and fully tracked as a MetaWindow. Horrible, but mostly harmless -
+   * the window is a 1x1 overide redirect window positioned offscreen.
+   */
   gtk_widget_show (GTK_WIDGET (ui->frames));
 
   g_object_set_data (G_OBJECT (gdisplay), "meta-ui", ui);