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

cc/pinch_zoom_scrollbars_manager.h

Index: cc/pinch_zoom_scrollbars_manager.h
diff --git a/cc/pinch_zoom_scrollbars_manager.h b/cc/pinch_zoom_scrollbars_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..169c25f4c6e182b7dd4ebf1b1bbc149f2caed449
--- /dev/null
+++ b/cc/pinch_zoom_scrollbars_manager.h
@@ -0,0 +1,158 @@
+// 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_PINCH_ZOOM_SCROLLBARS_MANAGER_H_
+#define CC_PINCH_ZOOM_SCROLLBARS_MANAGER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "cc/scoped_resource.h"
+#include "cc/scrollbar_geometry_fixed_thumb.h"
+#include "cc/scrollbar_layer_impl.h"
+#include <public/WebRect.h>
+#include <public/WebScrollbar.h>
+
+namespace cc {
+
+class PinchZoomScrollbarsManager {
+public:
+    static scoped_ptr<PinchZoomScrollbarsManager> create();
+    ~PinchZoomScrollbarsManager();
+
+    void updateThumbTextures(ResourceProvider* resourceProvider);
+    void setContentBounds(const gfx::Size&);
+    void setPinchZoomViewportPosition(const gfx::Vector2dF&, float scale);
+    void setPinchZoomViewportBounds(const gfx::Size&);
+    void setRootScrollLayerOffset(const gfx::Vector2d& offset, const gfx::Vector2d& maxOffset);
+
+    void setDeviceScaleFactor(float scale) { m_deviceScaleFactor = scale; }
+
+    void setScrollbarVertical(ScrollbarLayerImpl* scrollbar);
+    void setScrollbarHorizontal(ScrollbarLayerImpl* scrollbar);
+
+    ScrollbarLayerImpl* scrollbarVertical() const { return m_pinchZoomScrollbarVertical; }
+    ScrollbarLayerImpl* scrollbarHorizontal() const { return m_pinchZoomScrollbarHorizontal; }
+
+    void setEnabled(bool enabled) { m_enabled = enabled; }
+
+private:
+    PinchZoomScrollbarsManager();
+
+    class Scrollbar : public WebKit::WebScrollbar {
+    public:
+        Scrollbar(PinchZoomScrollbarsManager* owner, WebScrollbar::Orientation orientation)
+            : m_owner(owner)
+            , m_orientation(orientation)
+            { }
+
+        // WebScrollbar implementation
+        virtual bool isOverlay() const;
+        virtual int value() const;
+        virtual WebKit::WebPoint location() const;
+        virtual WebKit::WebSize size() const;
+        virtual bool enabled() const;
+        virtual int maximum() const;
+        virtual int totalSize() const;
+        virtual bool isScrollViewScrollbar() const;
+        virtual bool isScrollableAreaActive() const;
+        virtual void getTickmarks(WebKit::WebVector<WebKit::WebRect>& tickmarks) const;
+        virtual WebScrollbar::ScrollbarControlSize controlSize() const;
+        virtual WebScrollbar::ScrollbarPart pressedPart() const;
+        virtual WebScrollbar::ScrollbarPart hoveredPart() const;
+        virtual WebScrollbar::ScrollbarOverlayStyle scrollbarOverlayStyle() const;
+        virtual WebScrollbar::Orientation orientation() const;
+        virtual bool isCustomScrollbar() const;
+
+    private:
+        PinchZoomScrollbarsManager* m_owner;
+        WebScrollbar::Orientation m_orientation;
+    };
+
+    class ScrollbarThemeGeometry : public WebKit::WebScrollbarThemeGeometry {
+    public:
+        explicit ScrollbarThemeGeometry(PinchZoomScrollbarsManager* owner) : m_owner(owner) { }
+
+        virtual WebKit::WebScrollbarThemeGeometry* clone() const OVERRIDE;
+        virtual int thumbPosition(WebKit::WebScrollbar*) OVERRIDE;
+        virtual int thumbLength(WebKit::WebScrollbar*) OVERRIDE;
+        virtual int trackPosition(WebKit::WebScrollbar*) OVERRIDE;
+        virtual int trackLength(WebKit::WebScrollbar*) OVERRIDE;
+        virtual bool hasButtons(WebKit::WebScrollbar*) OVERRIDE;
+        virtual bool hasThumb(WebKit::WebScrollbar*) OVERRIDE;
+        virtual WebKit::WebRect trackRect(WebKit::WebScrollbar*) OVERRIDE;
+        virtual WebKit::WebRect thumbRect(WebKit::WebScrollbar*) OVERRIDE;
+        virtual int minimumThumbLength(WebKit::WebScrollbar*) OVERRIDE;
+        virtual int scrollbarThickness(WebKit::WebScrollbar*) OVERRIDE;
+        virtual WebKit::WebRect backButtonStartRect(WebKit::WebScrollbar*) OVERRIDE;
+        virtual WebKit::WebRect backButtonEndRect(WebKit::WebScrollbar*) OVERRIDE;
+        virtual WebKit::WebRect forwardButtonStartRect(WebKit::WebScrollbar*) OVERRIDE;
+        virtual WebKit::WebRect forwardButtonEndRect(WebKit::WebScrollbar*) OVERRIDE;
+        virtual WebKit::WebRect constrainTrackRectToTrackPieces(WebKit::WebScrollbar*, const WebKit::WebRect&) OVERRIDE;
+        virtual void splitTrack(WebKit::WebScrollbar*, const WebKit::WebRect& track, WebKit::WebRect& startTrack, WebKit::WebRect& thumb, WebKit::WebRect& endTrack) OVERRIDE;
+
+    private:
+        PinchZoomScrollbarsManager* m_owner;
+    };
+
+    // We need to override (at least) the splitTrack() function from ScrollbarGeometryFixedThumb,
+    // so this interface exists to allow us to implement the required functions.
+    class PZScrollbarGeometry : public ScrollbarGeometryFixedThumb {

[enne (OOO), 2012/12/13 17:43:38]

Why are you using FixedThumb?

[wjmaclean, 2012/12/13 18:26:50]

Primarily because ScrollbarLayerImpl requires this type, and I was trying to
minimize the changes. I'll look into deriving from SLI to achieve this with less
overhead.

[enne (OOO), 2012/12/13 18:57:42]

Ah, just curious.  FixedThumb is there because ScrollbarLayerImpl can't
regenerate content, so it needs to keep the thumb at a fixed size.  It just
didn't seem like that restriction was needed here.

+    public:
+        static scoped_ptr<ScrollbarGeometryFixedThumb> create(scoped_ptr<WebKit::WebScrollbarThemeGeometry>, PinchZoomScrollbarsManager* owner);
+        virtual ~PZScrollbarGeometry();
+
+        virtual WebKit::WebScrollbarThemeGeometry* clone() const OVERRIDE;
+        virtual int thumbLength(WebKit::WebScrollbar*) OVERRIDE;
+        virtual int thumbPosition(WebKit::WebScrollbar*) OVERRIDE;
+        virtual void splitTrack(WebKit::WebScrollbar*, const WebKit::WebRect& track, WebKit::WebRect& startTrack, WebKit::WebRect& thumb, WebKit::WebRect& endTrack) OVERRIDE;
+
+    private:
+        explicit PZScrollbarGeometry(scoped_ptr<WebKit::WebScrollbarThemeGeometry>, PinchZoomScrollbarsManager* owner);
+
+        PinchZoomScrollbarsManager* m_owner;
+    };
+
+    static const int kTrackWidth = 15;
+    WebKit::WebRect thumbRect(const WebKit::WebScrollbar*) const;
+    WebKit::WebRect trackRect(const WebKit::WebScrollbar*) const;
+    int thumbLength(const WebKit::WebScrollbar*) const ;
+    int trackLength(const WebKit::WebScrollbar*) const ;
+    // The following function allows us to include device scale factor in the
+    // track width at some later time, if we wish.
+    int trackWidth() const { return kTrackWidth; }
+    int position(const WebKit::WebScrollbar*) const;
+    int maximum(const WebKit::WebScrollbar*) const;
+
+    void updateOneThumb(ScrollbarLayerImpl* scrollbarImpl,
+                        Scrollbar& scrollbar,
+                        scoped_ptr<ScopedResource>& thumbTexture,
+                        scoped_ptr<SkCanvas>& thumbCanvas,
+                        ResourceProvider* resourceProvider);
+
+    void updateScrollbarImpl(ScrollbarLayerImpl*, WebKit::WebScrollbar*);
+
+    Scrollbar m_scrollbarVertical;
+    Scrollbar m_scrollbarHorizontal;
+
+    // The layer tree owns the scrollbar impl pointers.
+    ScrollbarLayerImpl* m_pinchZoomScrollbarVertical;

[enne (OOO), 2012/12/13 17:43:38]

This class is way too smart and the layers are way too dumb.  Why do you
duplicate everything here? Why not just put everything once on the layer? It'd
actually be pretty useful to have something that inherits from
ScrollbarLayerImpl but can paint its scrollbar on the impl thread.

[wjmaclean, 2012/12/13 18:26:50]

OK, I'll create a derived class to do it.

+    ScrollbarLayerImpl* m_pinchZoomScrollbarHorizontal;
+
+    scoped_ptr<ScopedResource> m_verticalThumbTexture;
+    scoped_ptr<ScopedResource> m_horizontalThumbTexture;
+
+    scoped_ptr<SkCanvas> m_verticalThumbCanvas;
+    scoped_ptr<SkCanvas> m_horizontalThumbCanvas;
+
+    gfx::Vector2dF m_layoutViewportPosition;
+    gfx::Size m_layoutViewportSize;
+    gfx::Size m_layoutDocumentSize;
+    gfx::Vector2d m_rootScrollOffset;
+    gfx::Vector2d m_rootMaxScrollOffset;
+    float m_viewportScale;
+    float m_deviceScaleFactor;
+
+    bool m_enabled;
+};
+}
+#endif // CC_PINCH_ZOOM_SCROLLBARS_MANAGER_H_