Mac: Shift more code into C++ classes from ObjC classes

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"
 
+@class CompositingIOSurfaceLayer;
+
 namespace content {
 class CompositingIOSurfaceMac;
 class CompositingIOSurfaceContext;
-class CompositingIOSurfaceLayerHelper;
 
+// The interface through which the CompositingIOSurfaceLayer calls back into
+// the structrue that created it (RenderWidgetHostViewMac or
+// BrowserCompositorViewMac).
 class CompositingIOSurfaceLayerClient {
  public:
   virtual void AcceleratedLayerDidDrawFrame(bool succeeded) = 0;
 };
 
+// CompositingIOSurfaceLayerHelper provides C++ functionality needed for the
+// CompositingIOSurfaceLayer class, and does most of the heavy lifting for the
+// class.
+// TODO(ccameron): This class should own CompositingIOSurfaceLayer, rather than
+// vice versa.
+class CompositingIOSurfaceLayerHelper {
+ public:
+  CompositingIOSurfaceLayerHelper(CompositingIOSurfaceLayerClient* client,
+                                  CompositingIOSurfaceLayer* layer);
+  ~CompositingIOSurfaceLayerHelper();
+
+  // Called when the CompositingIOSurfaceLayer gets a new frame.
+  void GotNewFrame();
+
+  // Called when -[CompositingIOSurfaceLayer canDrawInCGLContext] is called,
+  // and is passed the result that will be returned. This manages transitioning
+  // the layer in and out of asynchronous mode, and some logging.
+  void CanDrawCalled(bool needs_display);
+
+  // Called whenever -[CompositingIOSurfaceLayer drawInCGLContext] draws a
+  // frame, or when we need to ack a frame that (due to the vagaries of
+  // CoreAnimation) happens not to have drawn.
+  void AckPendingFrame(bool success);
+
+  // Immediately draw a frame (disregarding vsync) and ensure that the frame is
+  // acknowledged.
+  void ImmediatelyForceDisplayAndAck();
+
+ private:
+  void TimerFired();
+
+  // The client that the owning layer was created with.
+  content::CompositingIOSurfaceLayerClient* client_;

[miu, 2014/07/16 22:31:55]

nit: Please make const since client_ is never modified outside of ctor init
list.

  content::CompositingIOSurfaceLayerClient* const client_;

[ccameron, 2014/07/17 02:30:02]

Done.

+
+  // The layer that owns this helper.
+  CompositingIOSurfaceLayer* layer_;

[miu, 2014/07/16 22:31:55]

ditto: pointer should be const.

[ccameron, 2014/07/17 02:30:02]

Done.

+
+  // This is set when a frame is received, and un-set when the frame is drawn.
+  bool has_pending_frame_;
+
+  // Incremented every time that this layer is asked to draw but does not have
+  // new content to draw.
+  uint64 did_not_draw_counter_;
+
+  // 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.
+  base::DelayTimer<CompositingIOSurfaceLayerHelper> timer_;
+};
+
 }  // namespace content
 
 // 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_;

[miu, 2014/07/16 22:31:55]

IMHO, this state should be moved into the helper class along with the
setAsynchronous:YES call.  (see comments in .mm file)

[ccameron, 2014/07/17 02:30:02]

Moved.

-
-  // This is set when a frame is received, and un-set when the frame is drawn.
-  BOOL has_pending_frame_;
-
-  // 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
         withScaleFactor:(float)scale_factor
              withClient:(content::CompositingIOSurfaceLayerClient*)client;
 
-// Mark that the client is no longer valid and cannot be called back into.
+// Mark that the client is no longer valid and cannot be called back into. This
+// must be called before the layer is destroyed.
 - (void)resetClient;
 
 // Called when a new frame is received.
 - (void)gotNewFrame;
 
 @end
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_LAYER_MAC_H_