Throttle rendering pipeline for invisible iframes

public/web/WebWidget.h

 
 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 92 matching lines @@
     // onto the specified canvas at (viewPort.x,viewPort.y). You MUST call
     // Layout before calling this method. It is okay to call paint
     // multiple times once layout has been called, assuming no other
     // changes are made to the WebWidget (e.g., once events are
     // processed, it should be assumed that another call to layout is
     // warranted before painting again).
     virtual void paint(WebCanvas*, const WebRect& viewPort) { }
 
     virtual void paintCompositedDeprecated(WebCanvas*, const WebRect&) { }
 
+    virtual void didCommitCompositorFrame() { }

[dglazkov, 2015/09/02 21:12:06]

Can you help me understand why this needs to be at the DidComitCompositorFrame
phase and not at the end of WebViewImpl::layout, like
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

[ojan, 2015/09/02 21:17:11]

See
https://codereview.chromium.org/1246173002/diff/520001/Source/web/WebViewImpl....

TL;DR: We do the actual paint recording after WebViewImpl::layout. We compute
the visibility at the end of layout, but we don't want it to apply mid-way
through the pipeline, we want to it apply after the current frame ends and
before the next one begins. Otherwise, we end up painting a frame that's in an
invalid state.

+
     // Run layout and paint of all pending document changes asynchronously.
     // The caller is resposible for keeping the WebLayoutAndPaintAsyncCallback
     // object alive until it is called.
     virtual void layoutAndPaintAsync(WebLayoutAndPaintAsyncCallback*) { }
 
     // The caller is responsible for keeping the WebCompositeAndReadbackAsyncCallback
     // object alive until it is called. This should only be called when
     // isAcceleratedCompositingActive() is true.
     virtual void compositeAndReadbackAsync(WebCompositeAndReadbackAsyncCallback*) { }
 
@@ skipping 139 matching lines @@
     // control what are valid states for top controls and if it should animate.
     virtual void updateTopControlsState(WebTopControlsState constraints, WebTopControlsState current, bool animate) { }
 
 protected:
     ~WebWidget() { }
 };
 
 } // namespace blink
 
 #endif