[mutter/wip/dnd-surface3: 7/11] compositor: Add A "feedback" window group

[Carlos Garnacho <carlosg src gnome org>]

commit ad560999be0eae89f66d0cd96973156677133447
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Oct 6 16:46:26 2014 +0200

    compositor: Add A "feedback" window group
    
    Although not strictly a window group... This ClutterActor is
    meant to stay always on top, and only show non-reactive actors
    created by Mutter itself. Two possible usecases for this layer
    are DnD surfaces, and touch spots.

 src/compositor/compositor-private.h |    2 +-
 src/compositor/compositor.c         |   14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletions(-)
---
diff --git a/src/compositor/compositor-private.h b/src/compositor/compositor-private.h
index a41f563..80fb4e2 100644
--- a/src/compositor/compositor-private.h
+++ b/src/compositor/compositor-private.h
@@ -23,7 +23,7 @@ struct _MetaCompositor
   guint           server_time_is_monotonic_time : 1;
   guint           no_mipmaps  : 1;
 
-  ClutterActor          *stage, *window_group, *top_window_group;
+  ClutterActor          *stage, *window_group, *top_window_group, *feedback_group;
   ClutterActor          *background_actor;
   GList                 *windows;
   Window                 output;
diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index 47bea31..6493dbe 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -449,6 +449,15 @@ redirect_windows (MetaScreen *screen)
     }
 }
 
+static void
+compositor_stage_actor_added (ClutterActor   *actor,
+                              ClutterActor   *child,
+                              MetaCompositor *compositor)
+{
+  /* Ensure the feedback group stays topmost */
+  clutter_actor_set_child_at_index (actor, compositor->feedback_group, -1);
+}
+
 void
 meta_compositor_manage (MetaCompositor *compositor)
 {
@@ -478,9 +487,14 @@ meta_compositor_manage (MetaCompositor *compositor)
 
   compositor->window_group = meta_window_group_new (screen);
   compositor->top_window_group = meta_window_group_new (screen);
+  compositor->feedback_group = meta_window_group_new (screen);
 
   clutter_actor_add_child (compositor->stage, compositor->window_group);
   clutter_actor_add_child (compositor->stage, compositor->top_window_group);
+  clutter_actor_add_child (compositor->stage, compositor->feedback_group);
+
+  g_signal_connect (compositor->stage, "actor-added",
+                    G_CALLBACK (compositor_stage_actor_added), compositor);
 
   if (meta_is_wayland_compositor ())
     {