[mutter] ClutterStageCogl: Don't get buffer damage dirty pixel when not supported

[Jonas Ådahl <jadahl src gnome org>]

commit 342532a98de4392e5539fcb5f375eebc13eb03f5
Author: Jonas Ådahl <jadahl gmail com>
Date:   Tue Sep 13 18:18:02 2016 +0800

    ClutterStageCogl: Don't get buffer damage dirty pixel when not supported
    
    Now with the existance of offscreen view framebuffers the buffer age
    damage regions are only valid if the view in question doesn't doesn't
    have an intermediate offscreen. So, for views that doesn't have buffer
    age, return the dirty pixel (0,0).
    
    https://bugzilla.gnome.org/show_bug.cgi?id=770672

 clutter/clutter/cogl/clutter-stage-cogl.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/clutter/clutter/cogl/clutter-stage-cogl.c b/clutter/clutter/cogl/clutter-stage-cogl.c
index 32a6978..2c525af 100644
--- a/clutter/clutter/cogl/clutter-stage-cogl.c
+++ b/clutter/clutter/cogl/clutter-stage-cogl.c
@@ -806,7 +806,9 @@ clutter_stage_cogl_get_dirty_pixel (ClutterStageWindow *stage_window,
                                     int                *x,
                                     int                *y)
 {
+  CoglFramebuffer *framebuffer = clutter_stage_view_get_framebuffer (view);
   gboolean has_buffer_age =
+    cogl_is_onscreen (framebuffer) &&
     cogl_clutter_winsys_has_feature (COGL_WINSYS_FEATURE_BUFFER_AGE);
   cairo_rectangle_int_t *rect;