[gtk+] x11: Fix damage tracking hack

[Matthias Clasen <matthiasc src gnome org>]

commit 4d60b5b10c472fb3b37465cede661288708e16e6
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Jan 8 13:44:36 2016 -0500

    x11: Fix damage tracking hack
    
    We are setting mime data with a destroy notify on the cairo
    surface to get notified when cairo registers damage for the
    surface (in that case, it clears the mime data, calling the
    destroy notify). Unfortunately, the destroy notify is also
    called when we remove the mime data ourselves, which was
    not intentional.
    
    Use a flag in the window impl struct to ignore the callback
    when we are clearing the hook.

 gdk/x11/gdkwindow-x11.c |   30 +++++++++++++++++++-----------
 gdk/x11/gdkwindow-x11.h |    1 +
 2 files changed, 20 insertions(+), 11 deletions(-)
---
diff --git a/gdk/x11/gdkwindow-x11.c b/gdk/x11/gdkwindow-x11.c
index 9f189ad..6106b28 100644
--- a/gdk/x11/gdkwindow-x11.c
+++ b/gdk/x11/gdkwindow-x11.c
@@ -250,8 +250,10 @@ static void
 on_surface_changed (void *data)
 {
   GdkWindow *window = data;
+  GdkWindowImplX11 *impl = GDK_WINDOW_IMPL_X11 (window->impl);
 
-  window_pre_damage (window);
+  if (impl->tracking_damage)
+    window_pre_damage (window);
 }
 
 /* We want to know when cairo drawing causes damage to the window,
@@ -269,12 +271,15 @@ hook_surface_changed (GdkWindow *window)
   GdkWindowImplX11 *impl = GDK_WINDOW_IMPL_X11 (window->impl);
 
   if (impl->cairo_surface)
-    cairo_surface_set_mime_data (impl->cairo_surface,
-                                 "x-gdk/change-notify",
-                                 (unsigned char *)"X",
-                                 1,
-                                 on_surface_changed,
-                                 window);
+    {
+      cairo_surface_set_mime_data (impl->cairo_surface,
+                                   "x-gdk/change-notify",
+                                   (unsigned char *)"X",
+                                   1,
+                                   on_surface_changed,
+                                   window);
+      impl->tracking_damage = 1;
+    }
 }
 
 static void
@@ -283,10 +288,13 @@ unhook_surface_changed (GdkWindow *window)
   GdkWindowImplX11 *impl = GDK_WINDOW_IMPL_X11 (window->impl);
 
   if (impl->cairo_surface)
-    cairo_surface_set_mime_data (impl->cairo_surface,
-                                 "x-gdk/change-notify",
-                                 NULL, 0,
-                                 NULL, NULL);
+    {
+      impl->tracking_damage = 0;
+      cairo_surface_set_mime_data (impl->cairo_surface,
+                                   "x-gdk/change-notify",
+                                   NULL, 0,
+                                   NULL, NULL);
+    }
 }
 
 static void
diff --git a/gdk/x11/gdkwindow-x11.h b/gdk/x11/gdkwindow-x11.h
index 2bc2417..ed0cbb6 100644
--- a/gdk/x11/gdkwindow-x11.h
+++ b/gdk/x11/gdkwindow-x11.h
@@ -73,6 +73,7 @@ struct _GdkWindowImplX11
   guint override_redirect : 1;
   guint frame_clock_connected : 1;
   guint frame_sync_enabled : 1;
+  guint tracking_damage: 1;
 
   gint window_scale;