[mutter] clutter: LEQUAL depth_testing on ClutterDeformEffect

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 706c5a7565062fa6a3219fa2fa87176d92f002b3
Author: Daniel García Moreno <dani danigm net>
Date:   Thu May 2 10:18:27 2019 +0200

    clutter: LEQUAL depth_testing on ClutterDeformEffect
    
    Moving an actor with a ClutterDeformEffect applied flickers because
    the depth_testing, setting the depth testing test function to
    COGL_DEPTH_TEST_FUNCTION_LEQUAL fixes the problem.
    
    Fixes https://gitlab.gnome.org/GNOME/mutter/issues/507

 clutter/clutter/clutter-deform-effect.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/clutter/clutter/clutter-deform-effect.c b/clutter/clutter/clutter-deform-effect.c
index a52e8b93f..05ee15f2b 100644
--- a/clutter/clutter/clutter-deform-effect.c
+++ b/clutter/clutter/clutter-deform-effect.c
@@ -282,6 +282,7 @@ clutter_deform_effect_paint_target (ClutterOffscreenEffect *effect)
   /* enable depth testing */
   cogl_depth_state_init (&depth_state);
   cogl_depth_state_set_test_enabled (&depth_state, TRUE);
+  cogl_depth_state_set_test_function (&depth_state, COGL_DEPTH_TEST_FUNCTION_LEQUAL);
   cogl_pipeline_set_depth_state (pipeline, &depth_state, NULL);
 
   /* enable backface culling if we have a back material */