[gnome-shell] shell-glsl-quad: Set the pipeline blend string explicitly

[Rui Matos <rtcm src gnome org>]

commit 44047ac881f97d6d43d5f78944934d79250bac69
Author: Rui Matos <tiagomatos gmail com>
Date:   Sat Oct 3 21:21:24 2015 +0200

    shell-glsl-quad: Set the pipeline blend string explicitly
    
    The default pipeline color is opaque white and blending is turned
    off. If we only draw with that color (e.g. because animations are
    disabled and we're always drawn with opacity == 255), blending is kept
    disabled since cogl_pipeline_set_color() returns early if the color
    doesn't change from what was there before.
    
    In our case we always want blending to be enabled which we can achieve
    by setting the blending string ourselves.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=755827

 src/shell-glsl-quad.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/shell-glsl-quad.c b/src/shell-glsl-quad.c
index b24f0ce..21652d1 100644
--- a/src/shell-glsl-quad.c
+++ b/src/shell-glsl-quad.c
@@ -139,6 +139,7 @@ shell_glsl_quad_constructed (GObject *object)
   if (G_UNLIKELY (klass->base_pipeline == NULL))
     {
       klass->base_pipeline = cogl_pipeline_new (ctx);
+      cogl_pipeline_set_blend (klass->base_pipeline, "RGBA = ADD (SRC_COLOR * (SRC_COLOR[A]), DST_COLOR * 
(1-SRC_COLOR[A]))", NULL);
 
       if (klass->build_pipeline != NULL)
         klass->build_pipeline (self);