[gtk+/gtk-2-20] gdk: Ensure flush of surface when cairo_t is destroyed

[Tor Lillqvist <tml src gnome org>]

commit bdff56e4724b32f9881746a78ff67d316da1df35
Author: Benjamin Otte <otte redhat com>
Date:   Wed Sep 1 00:59:56 2010 +0200

    gdk: Ensure flush of surface when cairo_t is destroyed
    
    Add an ugly workaround because GTK does not ensure surfaces get flushed
    before directly accessing the drawable backed by the surface. This is
    not visible on X11 (where flushing is a no-op), but can be seen on
    Windows.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=628291

 gdk/gdkcairo.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)
---
diff --git a/gdk/gdkcairo.c b/gdk/gdkcairo.c
index ef8ec25..e1d0daf 100644
--- a/gdk/gdkcairo.c
+++ b/gdk/gdkcairo.c
@@ -23,6 +23,13 @@
 #include "gdkregion-generic.h"
 #include "gdkalias.h"
 
+static void
+gdk_ensure_surface_flush (gpointer surface)
+{
+  cairo_surface_flush (surface);
+  cairo_surface_destroy (surface);
+}
+
 /**
  * gdk_cairo_create:
  * @drawable: a #GdkDrawable
@@ -43,6 +50,7 @@
 cairo_t *
 gdk_cairo_create (GdkDrawable *drawable)
 {
+  static const cairo_user_data_key_t key;
   cairo_surface_t *surface;
   cairo_t *cr;
     
@@ -54,7 +62,12 @@ gdk_cairo_create (GdkDrawable *drawable)
   if (GDK_DRAWABLE_GET_CLASS (drawable)->set_cairo_clip)
     GDK_DRAWABLE_GET_CLASS (drawable)->set_cairo_clip (drawable, cr);
     
-  cairo_surface_destroy (surface);
+  /* Ugly workaround for GTK not ensuring to flush surfaces before
+   * directly accessing the drawable backed by the surface. Not visible
+   * on X11 (where flushing is a no-op). For details, see
+   * https://bugzilla.gnome.org/show_bug.cgi?id=628291
+   */
+  cairo_set_user_data (cr, &key, surface, gdk_ensure_surface_flush);
 
   return cr;
 }