Ack swap buffers after a timeout

content/browser/renderer_host/compositing_iosurface_layer_mac.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_LAYER_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_LAYER_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/ref_counted.h"
+#include "base/timer/timer.h"
 
 namespace content {
 class CompositingIOSurfaceMac;
 class CompositingIOSurfaceContext;
+class CompositingIOSurfaceLayerHelper;
 
 class CompositingIOSurfaceLayerClient {
  public:
   virtual void AcceleratedLayerDidDrawFrame(bool succeeded) = 0;
-  virtual bool AcceleratedLayerHasNotAckedPendingFrame() const = 0;
 };
 
 }
 
 // The CoreAnimation layer for drawing accelerated content.
 @interface CompositingIOSurfaceLayer : CAOpenGLLayer {
  @private
   content::CompositingIOSurfaceLayerClient* client_;
   scoped_refptr<content::CompositingIOSurfaceMac> iosurface_;
   scoped_refptr<content::CompositingIOSurfaceContext> context_;
 
+  // The browser places back-pressure on the GPU by not acknowledging swap
+  // calls until they appear on the screen. This can lead to hangs if the
+  // view is moved offscreen (among other things). Prevent hangs by always
+  // acknowledging the frame after timeout of 1/6th of a second  has passed.
+  scoped_ptr<content::CompositingIOSurfaceLayerHelper> helper_;
+  scoped_ptr<base::DelayTimer<content::CompositingIOSurfaceLayerHelper>> timer_;
+
   // Used to track when canDrawInCGLContext should return YES. This can be
   // in response to receiving a new compositor frame, or from any of the events
   // that cause setNeedsDisplay to be called on the layer.
   BOOL needs_display_;
 
+  // This is set when a frame is received, and un-set when the frame is drawn.
+  BOOL has_pending_frame_;

[miu, 2014/06/04 03:57:07]

FYI--I've been told repeatedly by Mac owners (e.g., avi@) to use
camelCaseNamingStyle_ in ObjC code.  You may want to do a style clean-up in a
later change.

[ccameron, 2014/06/04 05:36:22]

Okay ... I had been switching more and more to the _ style -- I'll start
switching back.

+
   // Incremented every time that this layer is asked to draw but does not have
   // new content to draw.
   uint64 did_not_draw_counter_;
 }
 
 - (content::CompositingIOSurfaceMac*)iosurface;
 - (content::CompositingIOSurfaceContext*)context;
 
 - (id)initWithIOSurface:(scoped_refptr<content::CompositingIOSurfaceMac>)
                             iosurface
              withClient:(content::CompositingIOSurfaceLayerClient*)client;
 
 // Mark that the client is no longer valid and cannot be called back into.
 - (void)resetClient;
 
 // Called when a new frame is received.
 - (void)gotNewFrame;
 
 @end
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_LAYER_MAC_H_