From fc197a38cc2bd3119d02a4267a5b4210ed0669aa Mon Sep 17 00:00:00 2001
From: Hans Breuer <hans@breuer.org>
Date: Sun, 7 Nov 2010 21:12:28 +0100
Subject: [PATCH] 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 | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/gdk/gdkcairo.c b/gdk/gdkcairo.c
index 6e83f53a37..50762a9e92 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;
     
@@ -50,7 +58,13 @@ gdk_cairo_create (GdkDrawable *drawable)
 
   surface = _gdk_drawable_ref_cairo_surface (drawable);
   cr = cairo_create (surface);
-  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;
 }