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

cc/layer_tree_impl.h

 // Copyright 2012 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_IMPL_H_
 #define CC_LAYER_TREE_IMPL_H_
 
 #include "base/hash_tables.h"
 #include "base/values.h"
 #include "cc/layer_impl.h"
@@ skipping 16 matching lines @@
 class HeadsUpDisplayLayerImpl;
 class LayerTreeDebugState;
 class LayerTreeHostImpl;
 class LayerTreeImpl;
 class LayerTreeSettings;
 class MemoryHistory;
 class OutputSurface;
 class PaintTimeCounter;
 class Proxy;
 class ResourceProvider;
+class ScrollbarLayerImpl;
 class TileManager;
 struct RendererCapabilities;
 
 class CC_EXPORT LayerTreeImpl {
  public:
   typedef std::vector<LayerImpl*> LayerList;
 
   static scoped_ptr<LayerTreeImpl> create(LayerTreeHostImpl* layer_tree_host_impl)
   {
     return make_scoped_ptr(new LayerTreeImpl(layer_tree_host_impl));
@@ skipping 136 matching lines @@
 
   // Set on the active tree when the viewport size recently changed
   // and the active tree's size is now out of date.
   bool ViewportSizeInvalid() const;
   void SetViewportSizeInvalid();
   void ResetViewportSizeInvalid();
 
   // Useful for debug assertions, probably shouldn't be used for anything else.
   Proxy* proxy() const;
 
+  void SetPinchZoomHorizontalLayerId(int layer_id);
+  ScrollbarLayerImpl* PinchZoomScrollbarHorizontal();
+  void SetPinchZoomVerticalLayerId(int layer_id);
+  ScrollbarLayerImpl* PinchZoomScrollbarVertical();
+
+  enum PinchZoomScrollbarUpdateReason {

[enne (OOO), 2013/03/06 19:32:58]

What's the purpose of this enum? Are you just emulating the updateDrawProperties
update reason? Is updating 6 properties so expensive that you have to guard
against doing it too often?

[wjmaclean, 2013/03/06 22:36:53]

I was hoping that it might reduce the number of paint()'s issue to the PZ
scrollbars, though I can't really say that it helps much. It's gone.

[enne (OOO), 2013/03/06 22:45:38]

Paints? Isn't all the painting done on the main thread?

[wjmaclean, 2013/03/07 22:57:39]

Yes, but I was concerned about updates on the impl-side parameters possibly
making their way back and causing re-paints on the main thread ... perhaps I was
being overly cautious.

[enne (OOO), 2013/03/07 23:41:17]

I think you're being overly cautious.  I don't see how UpdatePinchZoomScrollbars
could cause a repaint.

+    UPDATE_IMPL_THREAD_SCROLL,
+    UPDATE_MAIN_THREAD_SCROLL
+  };
+
+  void UpdatePinchZoomScrollbarsIfNeeded(
+    PinchZoomScrollbarUpdateReason update_reason);
+  void FadeInPinchZoomScrollbars();
+  void FadeOutPinchZoomScrollbars();
+
+  bool HasPinchZoomScrollbars() {
+    return pinch_zoom_scrollbar_horizontal_layer_id &&
+           pinch_zoom_scrollbar_vertical_layer_id;
+  }
+
 protected:
   LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl);
 
   LayerTreeHostImpl* layer_tree_host_impl_;
   int source_frame_number_;
   scoped_ptr<LayerImpl> root_layer_;
   HeadsUpDisplayLayerImpl* hud_layer_;
   LayerImpl* root_scroll_layer_;
   LayerImpl* currently_scrolling_layer_;
   SkColor background_color_;
   bool has_transparent_background_;
 
+  int pinch_zoom_scrollbar_horizontal_layer_id;

[enne (OOO), 2013/03/06 19:32:58]

style nit: member variables end with trailing underscores.

[wjmaclean, 2013/03/06 22:36:53]

Thanks, missed that!

Done.

+  int pinch_zoom_scrollbar_vertical_layer_id;
+
   float page_scale_factor_;
   float page_scale_delta_;
   float sent_page_scale_delta_;
   float min_page_scale_factor_;
   float max_page_scale_factor_;
 
   typedef base::hash_map<int, LayerImpl*> LayerIdMap;
   LayerIdMap layer_id_map_;
 
   // Persisted state for non-impl-side-painting.
@@ skipping 10 matching lines @@
   // In impl-side painting mode, this is true when the tree may contain
   // structural differences relative to the active tree.
   bool needs_full_tree_sync_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }
 
 #endif  // CC_LAYER_TREE_IMPL_H_