[gtk+/gtk-2-24] win32: avoid assertion when creating a GdkPixmap fails

[Aleksander Morgado <aleksm src gnome org>]

commit cc2d29771daee4f88474497c3b596968a4ebb31a
Author: Aleksander Morgado <aleksander lanedo com>
Date:   Mon Apr 29 17:32:31 2013 +0200

    win32: avoid assertion when creating a GdkPixmap fails
    
    If gdk_pixmap_new() fails (e.g. CreateDIBSection() failure) we end up
    g_object_unref()-ing the temporary GdkPixmap, and we do this before having set
    the drawable_impl->hdc and drawable_impl->hdc_count. Now, this could have just
    been a couple of warnings being dumped, but instead it really crashes the
    application because in win32-specific GdkDrawable's finalize() we assert if
    drawable_impl->hdc_count is not zero:
    
    Gdk:ERROR:gdkdrawable-win32.c:2047:_gdk_win32_drawable_finish: assertion failed: (impl->hdc_count == 0)
    
    In order to avoid this crash, we make sure we don't decrement the hdc_count in
    the GdkPixmap's finalize() unless we have it set first (i.e. we avoid hdc_count
    going down to -1).
    
    https://bugzilla.gnome.org/show_bug.cgi?id=699236

 gdk/win32/gdkpixmap-win32.c |   21 +++++++++++++--------
 1 files changed, 13 insertions(+), 8 deletions(-)
---
diff --git a/gdk/win32/gdkpixmap-win32.c b/gdk/win32/gdkpixmap-win32.c
index 883efbe..e06d069 100644
--- a/gdk/win32/gdkpixmap-win32.c
+++ b/gdk/win32/gdkpixmap-win32.c
@@ -113,14 +113,19 @@ gdk_pixmap_impl_win32_finalize (GObject *object)
 
   if (!impl->is_foreign)
     {
-      drawable_impl->hdc_count--;
+      /* Only decrement count if we did set the hdc */
+      if (drawable_impl->hdc)
+       drawable_impl->hdc_count--;
 
-      /* Tell outstanding owners that the surface is useless */
-      cairo_surface_finish (drawable_impl->cairo_surface);
+      if (drawable_impl->cairo_surface)
+       {
+         /* Tell outstanding owners that the surface is useless */
+         cairo_surface_finish (drawable_impl->cairo_surface);
 
-      /* Drop our reference */
-      cairo_surface_destroy (drawable_impl->cairo_surface);
-      drawable_impl->cairo_surface = NULL;
+         /* Drop our reference */
+         cairo_surface_destroy (drawable_impl->cairo_surface);
+         drawable_impl->cairo_surface = NULL;
+       }
     }
 
   _gdk_win32_drawable_finish (GDK_DRAWABLE (object));