[mutter] compositor-x11: Move synchronization to before-update

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 551101c65cda0e8a3c3a609baef263d39a32a651
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri May 29 23:47:29 2020 +0200

    compositor-x11: Move synchronization to before-update
    
    The synchronization must happen no matter the painting, as it in itself
    might result in reported damage, making the stage actually painted. Thus
    move it out of the "pre-paint" handler, to something explicitly not tied
    to the painting itself - ClutterStage::before-update.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285

 src/compositor/meta-compositor-x11.c | 42 ++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 7 deletions(-)
---
diff --git a/src/compositor/meta-compositor-x11.c b/src/compositor/meta-compositor-x11.c
index 0ab4aa0320..2cec7df1cb 100644
--- a/src/compositor/meta-compositor-x11.c
+++ b/src/compositor/meta-compositor-x11.c
@@ -39,6 +39,8 @@ struct _MetaCompositorX11
 
   Window output;
 
+  gulong before_update_handler_id;
+
   gboolean frame_has_updated_xsurfaces;
   gboolean have_x11_sync_object;
 
@@ -291,15 +293,10 @@ out:
 }
 
 static void
-meta_compositor_x11_pre_paint (MetaCompositor *compositor)
+on_before_update (ClutterStage   *stage,
+                  MetaCompositor *compositor)
 {
   MetaCompositorX11 *compositor_x11 = META_COMPOSITOR_X11 (compositor);
-  MetaCompositorClass *parent_class;
-
-  maybe_unredirect_top_window (compositor_x11);
-
-  parent_class = META_COMPOSITOR_CLASS (meta_compositor_x11_parent_class);
-  parent_class->pre_paint (compositor);
 
   if (compositor_x11->frame_has_updated_xsurfaces)
     {
@@ -332,6 +329,18 @@ meta_compositor_x11_pre_paint (MetaCompositor *compositor)
     }
 }
 
+static void
+meta_compositor_x11_pre_paint (MetaCompositor *compositor)
+{
+  MetaCompositorX11 *compositor_x11 = META_COMPOSITOR_X11 (compositor);
+  MetaCompositorClass *parent_class;
+
+  maybe_unredirect_top_window (compositor_x11);
+
+  parent_class = META_COMPOSITOR_CLASS (meta_compositor_x11_parent_class);
+  parent_class->pre_paint (compositor);
+}
+
 static void
 meta_compositor_x11_post_paint (MetaCompositor *compositor)
 {
@@ -380,10 +389,26 @@ meta_compositor_x11_new (MetaDisplay *display,
                        NULL);
 }
 
+static void
+meta_compositor_x11_constructed (GObject *object)
+{
+  MetaCompositorX11 *compositor_x11 = META_COMPOSITOR_X11 (object);
+  MetaCompositor *compositor = META_COMPOSITOR (compositor_x11);
+  ClutterStage *stage = meta_compositor_get_stage (compositor);
+
+  compositor_x11->before_update_handler_id =
+    g_signal_connect (stage, "before-update",
+                      G_CALLBACK (on_before_update), compositor);
+
+  G_OBJECT_CLASS (meta_compositor_x11_parent_class)->constructed (object);
+}
+
 static void
 meta_compositor_x11_dispose (GObject *object)
 {
   MetaCompositorX11 *compositor_x11 = META_COMPOSITOR_X11 (object);
+  MetaCompositor *compositor = META_COMPOSITOR (compositor_x11);
+  ClutterStage *stage = meta_compositor_get_stage (compositor);
 
   if (compositor_x11->have_x11_sync_object)
     {
@@ -391,6 +416,8 @@ meta_compositor_x11_dispose (GObject *object)
       compositor_x11->have_x11_sync_object = FALSE;
     }
 
+  g_clear_signal_handler (&compositor_x11->before_update_handler_id, stage);
+
   G_OBJECT_CLASS (meta_compositor_x11_parent_class)->dispose (object);
 }
 
@@ -405,6 +432,7 @@ meta_compositor_x11_class_init (MetaCompositorX11Class *klass)
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
   MetaCompositorClass *compositor_class = META_COMPOSITOR_CLASS (klass);
 
+  object_class->constructed = meta_compositor_x11_constructed;
   object_class->dispose = meta_compositor_x11_dispose;
 
   compositor_class->manage = meta_compositor_x11_manage;