themingengine: set the cairo extend to PAD when we're stretching bg

This avoids artifacts around the borders due to bilinear filtering cairo
applies to the surface pattern when stretching it.

https://bugzilla.gnome.org/show_bug.cgi?id=663522

diff --git a/gtk/gtkthemingengine.c b/gtk/gtkthemingengine.c
index 8d6da01018860df8a3ef3dad7e88d1984854eab9..f068c3d38dbb9412beb53e5b9d1239acf4877439 100644 (file)
--- a/gtk/gtkthemingengine.c
+++ b/gtk/gtkthemingengine.c
@@ -1622,6 +1622,7 @@ render_background_internal (GtkThemingEngine *engine,
         }
       else
         {
+          cairo_pattern_set_extend (pattern, CAIRO_EXTEND_PAD);
           scale_width = width;
           scale_height = height;
         }