[mutter] screen-cast/window: Use window actor damaged signal instead of paint

[Jonas Ådahl <jadahl src gnome org>]

commit 65fde269c60678fd2d00c02e94b511ec3de4a93f
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Aug 26 16:12:30 2019 +0300

    screen-cast/window: Use window actor damaged signal instead of paint
    
    We are really more interested in when a window is damaged, rather than
    when it's painted, for screen casting windows. This also has the benefit
    of not listening on the "paint" signal of the actor, meaning it'll open
    doors for hacks currently necessary for taking a screenshot of a window
    consisting of multiple surfaces.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/752

 src/backends/meta-screen-cast-window-stream-src.c | 45 ++++++-----------------
 1 file changed, 11 insertions(+), 34 deletions(-)
---
diff --git a/src/backends/meta-screen-cast-window-stream-src.c 
b/src/backends/meta-screen-cast-window-stream-src.c
index dbf330420..c31830b03 100644
--- a/src/backends/meta-screen-cast-window-stream-src.c
+++ b/src/backends/meta-screen-cast-window-stream-src.c
@@ -34,13 +34,11 @@ struct _MetaScreenCastWindowStreamSrc
 
   MetaScreenCastWindow *screen_cast_window;
 
-  unsigned long screen_cast_window_before_paint_handler_id;
-  unsigned long screen_cast_window_after_paint_handler_id;
+  unsigned long screen_cast_window_damaged_handler_id;
   unsigned long screen_cast_window_destroyed_handler_id;
   unsigned long cursor_moved_handler_id;
   unsigned long cursor_changed_handler_id;
 
-  gboolean actor_was_dirty;
   gboolean cursor_bitmap_invalid;
 };
 
@@ -255,15 +253,10 @@ meta_screen_cast_window_stream_src_stop (MetaScreenCastWindowStreamSrc *window_s
   if (!window_src->screen_cast_window)
     return;
 
-  if (window_src->screen_cast_window_before_paint_handler_id)
+  if (window_src->screen_cast_window_damaged_handler_id)
     g_signal_handler_disconnect (window_src->screen_cast_window,
-                                 window_src->screen_cast_window_before_paint_handler_id);
-  window_src->screen_cast_window_before_paint_handler_id = 0;
-
-  if (window_src->screen_cast_window_after_paint_handler_id)
-    g_signal_handler_disconnect (window_src->screen_cast_window,
-                                 window_src->screen_cast_window_after_paint_handler_id);
-  window_src->screen_cast_window_after_paint_handler_id = 0;
+                                 window_src->screen_cast_window_damaged_handler_id);
+  window_src->screen_cast_window_damaged_handler_id = 0;
 
   if (window_src->screen_cast_window_destroyed_handler_id)
     g_signal_handler_disconnect (window_src->screen_cast_window,
@@ -282,23 +275,12 @@ meta_screen_cast_window_stream_src_stop (MetaScreenCastWindowStreamSrc *window_s
 }
 
 static void
-screen_cast_window_before_paint (MetaScreenCastWindow          *screen_cast_window,
-                                 MetaScreenCastWindowStreamSrc *window_src)
-{
-  window_src->actor_was_dirty =
-    meta_screen_cast_window_has_damage (screen_cast_window);
-}
-
-static void
-screen_cast_window_after_paint (MetaWindowActor               *actor,
-                                MetaScreenCastWindowStreamSrc *window_src)
+screen_cast_window_damaged (MetaWindowActor               *actor,
+                            MetaScreenCastWindowStreamSrc *window_src)
 {
-  if (window_src->actor_was_dirty)
-    {
-      MetaScreenCastStreamSrc *src = META_SCREEN_CAST_STREAM_SRC (window_src);
+  MetaScreenCastStreamSrc *src = META_SCREEN_CAST_STREAM_SRC (window_src);
 
-      meta_screen_cast_stream_src_maybe_record_frame (src);
-    }
+  meta_screen_cast_stream_src_maybe_record_frame (src);
 }
 
 static void
@@ -378,16 +360,11 @@ meta_screen_cast_window_stream_src_enable (MetaScreenCastStreamSrc *src)
 
   window_src->screen_cast_window = META_SCREEN_CAST_WINDOW (window_actor);
 
-  window_src->screen_cast_window_before_paint_handler_id =
+  window_src->screen_cast_window_damaged_handler_id =
     g_signal_connect (window_src->screen_cast_window,
-                      "paint",
-                      G_CALLBACK (screen_cast_window_before_paint),
+                      "damaged",
+                      G_CALLBACK (screen_cast_window_damaged),
                       window_src);
-  window_src->screen_cast_window_after_paint_handler_id =
-    g_signal_connect_after (window_src->screen_cast_window,
-                            "paint",
-                            G_CALLBACK (screen_cast_window_after_paint),
-                            window_src);
 
   window_src->screen_cast_window_destroyed_handler_id =
     g_signal_connect (window_src->screen_cast_window,