[gtk+] Check screen really changed before notifying it and invalidating the context

[Carlos Garnacho <carlosg src gnome org>]

commit 7a5a622998a32ef4e420cddfa5369bd630dc8b30
Author: Carlos Garcia Campos <cgarcia igalia com>
Date:   Fri Nov 26 09:01:17 2010 +0100

    Check screen really changed before notifying it and invalidating the context

 gtk/gtkstylecontext.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkstylecontext.c b/gtk/gtkstylecontext.c
index 2cee500..7e1dd2c 100644
--- a/gtk/gtkstylecontext.c
+++ b/gtk/gtkstylecontext.c
@@ -2556,8 +2556,12 @@ gtk_style_context_set_screen (GtkStyleContext *context,
   GtkStyleContextPrivate *priv;
 
   g_return_if_fail (GTK_IS_STYLE_CONTEXT (context));
+  g_return_if_fail (GDK_IS_SCREEN (screen));
 
   priv = context->priv;
+  if (priv->screen == screen)
+    return;
+
   priv->screen = screen;
 
   g_object_notify (G_OBJECT (context), "screen");