[mutter/wip/carlosg/performance-improvements: 29/38] compositor: Avoid changing pipeline/source if shadow is not being painted

[Carlos Garnacho <carlosg src gnome org>]

commit 060543466c4cb55557734fc03b40e09ecb086e16
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun May 7 03:00:10 2017 +0200

    compositor: Avoid changing pipeline/source if shadow is not being painted
    
    Avoids some context invalidations in cogl.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=782344

 src/compositor/meta-shadow-factory.c |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)
---
diff --git a/src/compositor/meta-shadow-factory.c b/src/compositor/meta-shadow-factory.c
index cd00600..33b9741 100644
--- a/src/compositor/meta-shadow-factory.c
+++ b/src/compositor/meta-shadow-factory.c
@@ -220,11 +220,7 @@ meta_shadow_paint (MetaShadow     *shadow,
   int dest_x[4];
   int dest_y[4];
   int n_x, n_y;
-
-  cogl_pipeline_set_color4ub (shadow->pipeline,
-                              opacity, opacity, opacity, opacity);
-
-  cogl_set_source (shadow->pipeline);
+  gboolean source_updated = FALSE;
 
   if (shadow->scale_width)
     {
@@ -300,6 +296,17 @@ meta_shadow_paint (MetaShadow     *shadow,
           else
             overlap = CAIRO_REGION_OVERLAP_IN;
 
+          if (overlap == CAIRO_REGION_OVERLAP_OUT)
+            continue;
+
+          if (!source_updated)
+            {
+              cogl_pipeline_set_color4ub (shadow->pipeline,
+                                          opacity, opacity, opacity, opacity);
+              cogl_set_source (shadow->pipeline);
+              source_updated = TRUE;
+            }
+
           /* There's quite a bit of overhead from allocating a new
            * region in order to find an exact intersection and
            * generating more geometry - we make the assumption that