[niepce] Must call mark_dirty() in the surface for it to work. Thanks to mitch on #gegl

[Hubert FiguiÃre <hub src gnome org>]

commit cbb6b8235a7fe0bd1babfba4962fdfb790fad9d3
Author: Hubert FiguiÃre <hub figuiere net>
Date:   Sun Jul 22 14:54:53 2012 -0700

    Must call mark_dirty() in the surface for it to work.
    Thanks to mitch on #gegl

 src/ncr/image.cpp |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/ncr/image.cpp b/src/ncr/image.cpp
index 8a2246b..c19ecac 100644
--- a/src/ncr/image.cpp
+++ b/src/ncr/image.cpp
@@ -336,6 +336,9 @@ Cairo::RefPtr<Cairo::Surface> Image::cairo_surface_for_display()
                    (void*)surface->get_data(), surface->get_stride(),
                    (GeglBlitFlags)(GEGL_BLIT_CACHE | GEGL_BLIT_DIRTY));
 
+    // If you don't do that, it will never paint().
+    // Thanks to mitch for the tip in #gegl
+    surface->mark_dirty();
     return surface;
 }