Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/layer_tree_host.h

 // 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.
 
 #ifndef CC_LAYER_TREE_HOST_H_
 #define CC_LAYER_TREE_HOST_H_
 
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 35 matching lines @@
 class AnimationRegistrar;
 class HeadsUpDisplayLayer;
 class Layer;
 class LayerTreeHostImpl;
 class LayerTreeHostImplClient;
 class PrioritizedResourceManager;
 class PrioritizedResource;
 class Region;
 class ResourceProvider;
 class ResourceUpdateQueue;
+class ScrollbarLayer;
 class TopControlsManager;
 struct ScrollAndScaleSet;
 
 
 // Provides information on an Impl's rendering capabilities back to the LayerTreeHost
 struct CC_EXPORT RendererCapabilities {
     RendererCapabilities();
     ~RendererCapabilities();
 
     unsigned bestTextureFormat;
@@ skipping 24 matching lines @@
     bool needsOffscreenContext() const { return m_needsFilterContext || settings().acceleratePainting; }
 
     // LayerTreeHost interface to Proxy.
     void willBeginFrame() { m_client->willBeginFrame(); }
     void didBeginFrame();
     void updateAnimations(base::TimeTicks monotonicFrameBeginTime);
     void didStopFlinging();
     void layout();
     void beginCommitOnImplThread(LayerTreeHostImpl*);
     void finishCommitOnImplThread(LayerTreeHostImpl*);
+    void setPinchZoomScrollbarsBoundsAndPosition();
+    void createAndAddPinchZoomScrollbars();
     void willCommit();
     void commitComplete();
     scoped_ptr<OutputSurface> createOutputSurface();
     scoped_ptr<InputHandler> createInputHandler();
     virtual scoped_ptr<LayerTreeHostImpl> createLayerTreeHostImpl(LayerTreeHostImplClient*);
     void didLoseOutputSurface();
     enum RecreateResult {
         RecreateSucceeded,
         RecreateFailedButTryAgain,
         RecreateFailedAndGaveUp,
@@ skipping 35 matching lines @@
     void setNeedsAnimate();
     // virtual for testing
     virtual void setNeedsCommit();
     virtual void setNeedsFullTreeSync();
     void setNeedsRedraw();
     bool commitRequested() const;
 
     void setAnimationEvents(scoped_ptr<AnimationEventsVector>, base::Time wallClockTime);
 
     Layer* rootLayer() { return m_rootLayer.get(); }
+    Layer* rootScrollLayer() const;

[jamesr, 2013/03/02 03:19:14]

Do you still need this?

[wjmaclean, 2013/03/04 15:53:10]

Yes, I believe so. In order for a PZ scrollbar to paint, its ScrollbarLayer
calls the PinchZoomScrollbar object as part of determining the thumb geometry,
and since this information isn't coming from WebKit, the PinchZoomScrollbar
needs to be able to pull it from the root scroll layer.

This function allows a caller external to LTH to get access to
findFirstScrollableLayer(), though I suppose we could expose that instead, or
possible have PinchZoomScrollbar replicate LTH's logic for doing this (though I
suspect that would be harder to maintain).

+
     const Layer* rootLayer() const { return m_rootLayer.get(); }
     void setRootLayer(scoped_refptr<Layer>);
 
     const LayerTreeSettings& settings() const { return m_settings; }
 
     void setDebugState(const LayerTreeDebugState& debugState);
     const LayerTreeDebugState& debugState() const { return m_debugState; }
 
     void setViewportSize(const gfx::Size& layoutViewportSize, const gfx::Size& deviceViewportSize);
 
@@ skipping 81 matching lines @@
 
     int m_commitNumber;
     RenderingStats m_renderingStats;
 
     bool m_rendererInitialized;
     bool m_outputSurfaceLost;
     int m_numFailedRecreateAttempts;
 
     scoped_refptr<Layer> m_rootLayer;
     scoped_refptr<HeadsUpDisplayLayer> m_hudLayer;
+    scoped_refptr<ScrollbarLayer> m_pinchZoomScrollbarHorizontal;
+    scoped_refptr<ScrollbarLayer> m_pinchZoomScrollbarVertical;
 
     scoped_ptr<PrioritizedResourceManager> m_contentsTextureManager;
     scoped_ptr<PrioritizedResource> m_surfaceMemoryPlaceholder;
 
     base::WeakPtr<TopControlsManager> m_topControlsManagerWeakPtr;
 
     LayerTreeSettings m_settings;
     LayerTreeDebugState m_debugState;
 
     gfx::Size m_layoutViewportSize;
@@ skipping 17 matching lines @@
     size_t m_partialTextureUpdateRequests;
 
     scoped_ptr<AnimationRegistrar> m_animationRegistrar;
 
     DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYER_TREE_HOST_H_