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

cc/pinch_zoom_scrollbar_layer_impl.h

Index: cc/pinch_zoom_scrollbar_layer_impl.h
diff --git a/cc/pinch_zoom_scrollbar_layer_impl.h b/cc/pinch_zoom_scrollbar_layer_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..7b7d102c9ea387854459c90a9e6f83a11304412d
--- /dev/null
+++ b/cc/pinch_zoom_scrollbar_layer_impl.h
@@ -0,0 +1,109 @@
+// 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 PINCH_ZOOM_SCROLLBAR_LAYER_IMPL_H_
+#define PINCH_ZOOM_SCROLLBAR_LAYER_IMPL_H_
+
+#include "cc/cc_export.h"
+#include "cc/scoped_resource.h"
+#include "cc/scrollbar_layer_impl_base.h"
+#include "ui/gfx/rect.h"
+
+namespace cc {
+
+class PinchZoomViewport;
+
+// PinchZoomScrollbarState exists to store the state associated with a
+// PinchZoomScrollbarLayerImpl, so the latter can be treated as an inexpensive
+// wrapper that can be cheaply created and discarded.

[Ian Vollick, 2013/01/15 20:33:48]

We should design a system that allows impl-only layers to persist. Keeping the
state alive so that we can regenerate the layers cheaply is unfortunate, all
this stuff should live in PZSI.

+class CC_EXPORT PinchZoomScrollbarState {
+ public:
+  PinchZoomScrollbarState(WebKit::WebScrollbar::Orientation,
+                           PinchZoomViewport* owner);
+  ~PinchZoomScrollbarState();
+
+  WebKit::WebScrollbar::Orientation orientation() const {
+    return orientation_;
+  }
+
+  scoped_ptr<ScopedResource>& thumb_texture() {
+    return thumb_texture_;
+  }
+
+  gfx::Rect& thumb_rect() {
+    return thumb_rect_;
+  }
+
+  float& thumb_position() {
+    return thumb_position_;
+  }
+
+  int& track_length() {
+    return track_length_;
+  }
+
+  int& maximum_position() {
+    return maximum_position_;
+  }
+
+  gfx::SizeF layout_viewport_size() const;
+  gfx::Vector2dF zoomed_viewport_offset() const;
+  float total_page_scale_factor() const;
+  float device_scale_factor() const;
+  LayerImpl* root_scroll_layer();
+
+  // A separate function to trigger size & position changes while
+  // *not* in willDraw().
+  void RefreshSizeAndPosition(LayerImpl*);
+  bool ShouldDisplayPinchZoomScrollbars();
+
+  int track_width() const {
+    return kTrackWidth;
+  }
+
+ private:
+  static const int kTrackWidth = 10;
+  PinchZoomViewport* owner_;
+
+  WebKit::WebScrollbar::Orientation orientation_;
+
+  scoped_ptr<ScopedResource> thumb_texture_;
+  gfx::Rect thumb_rect_;
+  float thumb_position_;
+  int track_length_;
+  int maximum_position_;
+};
+
+class CC_EXPORT PinchZoomScrollbarLayerImpl : public ScrollbarLayerImplBase {
+ public:
+  static scoped_ptr<PinchZoomScrollbarLayerImpl> create(
+    LayerTreeImpl* treeImpl, int id, PinchZoomScrollbarState* state);
+  virtual ~PinchZoomScrollbarLayerImpl();
+
+  // ScrollbarLayerImplBase overrides.
+  virtual float currentPos() const OVERRIDE;
+  virtual int totalSize() const OVERRIDE;
+  virtual int maximum() const OVERRIDE;
+
+  virtual WebKit::WebScrollbar::Orientation orientation() const OVERRIDE;
+
+  // LayerImpl overrides.
+  virtual void appendQuads(QuadSink&, AppendQuadsData&) OVERRIDE;
+  virtual void didLoseOutputSurface() OVERRIDE;
+  virtual void willDraw(ResourceProvider*) OVERRIDE;
+  // The pinch-zoom scrollbars should never have an implTransform applied to them.
+  virtual void setImplTransform(const gfx::Transform& transform) OVERRIDE { }
+
+  // Class-specific functions.
+
+ private:
+  PinchZoomScrollbarLayerImpl(
+    LayerTreeImpl* treeImpl, int id, PinchZoomScrollbarState* state);
+
+  PinchZoomScrollbarState* state_;
+
+};
+
+}  // namespace cc
+#endif // PINCH_ZOOM_SCROLLBAR_LAYER_IMPL_H_