[gnome-shell] Disable clearing the color buffer

[Owen Taylor <otaylor src gnome org>]

commit 55f290bc9620685b96e3cfe2911a93e383f2fbcd
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Sat Nov 13 13:02:39 2010 -0500

    Disable clearing the color buffer
    
    Since we always cover the stage, we don't need to clear it to a
    constant color before painting the scene.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=634769

 js/ui/main.js |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/js/ui/main.js b/js/ui/main.js
index 5177df6..4589ad0 100644
--- a/js/ui/main.js
+++ b/js/ui/main.js
@@ -97,10 +97,11 @@ function start() {
     Shell.WindowTracker.get_default();
     Shell.AppUsage.get_default();
 
-    // The background color really only matters if there is no desktop
-    // window (say, nautilus) running. We set it mostly so things look good
-    // when we are running inside Xephyr.
+    // The stage is always covered so Clutter doesn't need to clear it; however
+    // the color is used as the default contents for the actor created by
+    // global.create_root_pixmap_actor() so we set it anyways.
     global.stage.color = DEFAULT_BACKGROUND_COLOR;
+    global.stage.no_clear_hint = true;
 
     let themeContext = St.ThemeContext.get_for_stage (global.stage);
     let stylesheetPath = global.datadir + '/theme/gnome-shell.css';