Chromium compositor change implementing page-scale driven pinch-zoom.

cc/CCThreadProxy.cpp

 // Copyright 2011 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.
 
 #include "config.h"
 
 #include "CCThreadProxy.h"
 
 #include "CCDelayBasedTimeSource.h"
 #include "CCDrawQuad.h"
@@ skipping 449 matching lines @@
     setNeedsForcedCommitOnImplThread();
 }
 
 void CCThreadProxy::scheduledActionBeginFrame()
 {
     TRACE_EVENT0("cc", "CCThreadProxy::scheduledActionBeginFrame");
     ASSERT(!m_pendingBeginFrameRequest);
     m_pendingBeginFrameRequest = adoptPtr(new BeginFrameAndCommitState());
     m_pendingBeginFrameRequest->monotonicFrameBeginTime = monotonicallyIncreasingTime();
     m_pendingBeginFrameRequest->scrollInfo = m_layerTreeHostImpl->processScrollDeltas();
+    m_pendingBeginFrameRequest->implTransform = m_layerTreeHostImpl->implTransform();

[Jeff Timanus, 2012/09/21 18:10:01]

I pass the impl-transform from the pinch state to the main thread at this point.
 This transform is then installed on the fist scrollable layer before the call
to CalculateDrawTransforms(...) in CCLayerTreeHost.

This ensures that only those tiles that are needed are prepared, as opposed to
all the tiles covering the red box.

I think my variable naming here is not the best.  I chose impl-transform,
because that's where this transformation is installed on the impl side, but I
think for the main thread, it would be clearer if this name indicated that it
was specific to the pinch zoom state, and only applied to the root scroll layer.
 Thoughts?

     m_pendingBeginFrameRequest->memoryAllocationLimitBytes = m_layerTreeHostImpl->memoryAllocationLimitBytes();
     m_layerTreeHost->getEvictedContentTexturesBackings(m_pendingBeginFrameRequest->evictedContentsTexturesBackings);
 
     m_mainThreadProxy->postTask(createCCThreadTask(this, &CCThreadProxy::beginFrame));
 
     if (m_beginFrameCompletionEventOnImplThread) {
         m_beginFrameCompletionEventOnImplThread->signal();
         m_beginFrameCompletionEventOnImplThread = 0;
     }
 }
@@ skipping 24 matching lines @@
     m_commitRequestSentToImplThread = true;
 
     // On the other hand, the animationRequested flag needs to be cleared
     // here so that any animation requests generated by the apply or animate
     // callbacks will trigger another frame.
     m_animateRequested = false;
 
     // FIXME: technically, scroll deltas need to be applied for dropped commits as well.
     // Re-do the commit flow so that we don't send the scrollInfo on the BFAC message.
     m_layerTreeHost->applyScrollAndScale(*request->scrollInfo);
+    m_layerTreeHost->setImplTransform(request->implTransform);
 
     if (!m_inCompositeAndReadback && !m_layerTreeHost->visible()) {
         m_commitRequested = false;
         m_commitRequestSentToImplThread = false;
         m_forcedCommitRequested = false;
 
         TRACE_EVENT0("cc", "EarlyOut_NotVisible");
         CCProxy::implThread()->postTask(createCCThreadTask(this, &CCThreadProxy::beginFrameAbortedOnImplThread));
         return;
     }
@@ skipping 406 matching lines @@
 }
 
 void CCThreadProxy::implSideRenderingStatsOnImplThread(CCCompletionEvent* completion, CCRenderingStats* stats)
 {
     ASSERT(isImplThread());
     m_layerTreeHostImpl->renderingStats(*stats);
     completion->signal();
 }
 
 } // namespace cc