[gthumb] mark the cairo surface as dirty after changing it

[Paolo Bacchilega <paobac src gnome org>]

commit 926b3239d24d31c9ea67f624ad5c1fb344dcf95d
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Fri Jun 28 16:44:43 2013 +0200

    mark the cairo surface as dirty after changing it

 gthumb/cairo-utils.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gthumb/cairo-utils.c b/gthumb/cairo-utils.c
index 43eceb9..44f480d 100644
--- a/gthumb/cairo-utils.c
+++ b/gthumb/cairo-utils.c
@@ -556,6 +556,8 @@ _cairo_image_surface_color_shift (cairo_surface_t *image,
                dest_row += dest_stride;
        }
 
+       cairo_surface_mark_dirty (shifted);
+
        return shifted;
 }