[gtk+] wayland: Don't assume drag context has a source window when finalizing

[Jonas Ådahl <jadahl src gnome org>]

commit 27763743b1d1c1900932099ff10e64f4a2734148
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Aug 3 14:26:39 2015 +0800

    wayland: Don't assume drag context has a source window when finalizing
    
    Only a drag context which was created with 'drag_begin' will be
    guaranteed to have a source window at all times. Thus, in finalize we
    cannot assume we can retrieve a GdkDisplay from the source_window
    pointer since it may be NULL. Though, the display is only needed for
    contexts created via 'drag_begin' thus we can retrieve it after
    checking that is the case.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=749339

 gdk/wayland/gdkdnd-wayland.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/gdk/wayland/gdkdnd-wayland.c b/gdk/wayland/gdkdnd-wayland.c
index e96aeda..835b6d0 100644
--- a/gdk/wayland/gdkdnd-wayland.c
+++ b/gdk/wayland/gdkdnd-wayland.c
@@ -64,13 +64,20 @@ gdk_wayland_drag_context_finalize (GObject *object)
 {
   GdkWaylandDragContext *wayland_context = GDK_WAYLAND_DRAG_CONTEXT (object);
   GdkDragContext *context = GDK_DRAG_CONTEXT (object);
-  GdkDisplay *display = gdk_window_get_display (context->source_window);
 
   contexts = g_list_remove (contexts, context);
 
-  if (context->is_source &&
-      gdk_selection_owner_get_for_display (display, gdk_drag_get_selection (context)) == 
context->source_window)
-    gdk_wayland_selection_unset_data_source (display, gdk_drag_get_selection (context));
+  if (context->is_source)
+    {
+      GdkDisplay *display = gdk_window_get_display (context->source_window);
+      GdkAtom selection;
+      GdkWindow *selection_owner;
+
+      selection = gdk_drag_get_selection (context);
+      selection_owner = gdk_selection_owner_get_for_display (display, selection);
+      if (selection_owner == context->source_window)
+        gdk_wayland_selection_unset_data_source (display, selection);
+    }
 
   if (wayland_context->data_source)
     wl_data_source_destroy (wayland_context->data_source);