Bug 713305 - Force staying on discrete GPU while any WebGL context is live - r=jrmuizel

content/canvas/src/WebGLContext.h

@@ -64,6 +64,10 @@
 
 #include "CheckedInt.h"
 
+#ifdef XP_MACOSX
+#include "ForceDiscreteGPUHelperCGL.h"
+#endif
+
 /* 
  * Minimum value constants defined in 6.2 State Tables of OpenGL ES - 2.0.25
  *   https://bugzilla.mozilla.org/show_bug.cgi?id=686732
@@ -943,6 +947,16 @@ protected:
     bool mContextLostErrorSet;
     bool mContextLostDueToTest;
 
+#ifdef XP_MACOSX
+    // see bug 713305. This RAII helper guarantees that we're on the discrete GPU, during its lifetime
+    // Debouncing note: we don't want to switch GPUs too frequently, so try to not create and destroy
+    // these objects at high frequency. Having WebGLContext's hold one such object seems fine,
+    // because WebGLContext objects only go away during GC, which shouldn't happen too frequently.
+    // If in the future GC becomes much more frequent, we may have to revisit then (maybe use a timer).
+    ForceDiscreteGPUHelperCGL mForceDiscreteGPUHelper;
+#endif
+
+
 public:
     // console logging helpers
     static void LogMessage(const char *fmt, ...);

gfx/gl/ForceDiscreteGPUHelperCGL.h

@@ -0,0 +1,65 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Initial Developer of the Original Code is Mozilla Foundation.
+ * Portions created by the Initial Developer are Copyright (C) 2010
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef ForceDiscreteGPUHelperCGL_h_
+#define ForceDiscreteGPUHelperCGL_h_
+
+#include <OpenGL/OpenGL.h>
+
+/** This RAII helper guarantees that we're on the discrete GPU during its lifetime.
+ * 
+ * As long as any ForceDiscreteGPUHelperCGL object is alive, we're on the discrete GPU.
+ */
+class ForceDiscreteGPUHelperCGL
+{
+    CGLPixelFormatObj mPixelFormatObj;
+
+public:
+    ForceDiscreteGPUHelperCGL()
+    {
+        // the code in this function is taken from Chromium, src/ui/gfx/gl/gl_context_cgl.cc, r122013
+        // BSD-style license, (c) The Chromium Authors
+        CGLPixelFormatAttribute attribs[1];
+        attribs[0] = static_cast<CGLPixelFormatAttribute>(0);
+        GLint num_pixel_formats = 0;
+        CGLChoosePixelFormat(attribs, &mPixelFormatObj, &num_pixel_formats);
+    }
+
+    ~ForceDiscreteGPUHelperCGL()
+    {
+        CGLReleasePixelFormat(mPixelFormatObj);
+    }
+};
+
+#endif // ForceDiscreteGPUHelperCGL_h_

gfx/gl/Makefile.in

@@ -52,6 +52,7 @@ EXPORTS	= \
 	GLContextProvider.h \
 	GLContextProviderImpl.h \
 	EGLUtils.h \
+	ForceDiscreteGPUHelperCGL.h \
 	$(NULL)
 
 ifdef MOZ_X11