Discard window pixmap only if the window actually resizes.

svn path=/trunk/KDE/kdebase/workspace/; revision=787945

events.cpp

@@ -1707,6 +1707,7 @@ void Unmanaged::configureNotifyEvent( XConfigureEvent* e )
         addWorkspaceRepaint( geometry()); // damage old area
         QRect old = geom;
         geom = newgeom;
+        if( old.size() != geom.size())
             discardWindowPixmap();
         if( scene != NULL )
             scene->windowGeometryShapeChanged( this );