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      1 /*
      2  * Copyright (C) 2011 Apple Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
     14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
     15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
     17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
     23  * THE POSSIBILITY OF SUCH DAMAGE.
     24  */
     25 
     26 #ifndef ScrollingCoordinator_h
     27 #define ScrollingCoordinator_h
     28 
     29 #include "core/platform/PlatformWheelEvent.h"
     30 #include "core/platform/ScrollTypes.h"
     31 #include "core/platform/graphics/IntRect.h"
     32 #include "core/rendering/RenderObject.h"
     33 #include "wtf/text/WTFString.h"
     34 
     35 namespace WebKit {
     36 class WebLayer;
     37 class WebScrollbarLayer;
     38 }
     39 
     40 namespace WebCore {
     41 
     42 typedef unsigned MainThreadScrollingReasons;
     43 
     44 class Document;
     45 class Frame;
     46 class FrameView;
     47 class GraphicsLayer;
     48 class Page;
     49 class Region;
     50 class ScrollableArea;
     51 class ViewportConstraints;
     52 
     53 class ScrollingCoordinator : public RefCounted<ScrollingCoordinator> {
     54 public:
     55     static PassRefPtr<ScrollingCoordinator> create(Page*);
     56     ~ScrollingCoordinator();
     57 
     58     void pageDestroyed();
     59 
     60     // Return whether this scrolling coordinator handles scrolling for the given frame view.
     61     bool coordinatesScrollingForFrameView(FrameView*) const;
     62 
     63     // Should be called whenever the given frame view has been laid out.
     64     void frameViewLayoutUpdated(FrameView*);
     65 
     66     // Should be called whenever a wheel event handler is added or removed in the
     67     // frame view's underlying document.
     68     void frameViewWheelEventHandlerCountChanged(FrameView*);
     69 
     70     // Should be called whenever the slow repaint objects counter changes between zero and one.
     71     void frameViewHasSlowRepaintObjectsDidChange(FrameView*);
     72 
     73     // Should be called whenever the set of fixed objects changes.
     74     void frameViewFixedObjectsDidChange(FrameView*);
     75 
     76     // Should be called whenever the root layer for the given frame view changes.
     77     void frameViewRootLayerDidChange(FrameView*);
     78 
     79 #if OS(DARWIN)
     80     // Dispatched by the scrolling tree during handleWheelEvent. This is required as long as scrollbars are painted on the main thread.
     81     void handleWheelEventPhase(PlatformWheelEventPhase);
     82 #endif
     83 
     84     enum MainThreadScrollingReasonFlags {
     85         HasSlowRepaintObjects = 1 << 0,
     86         HasViewportConstrainedObjectsWithoutSupportingFixedLayers = 1 << 1,
     87         HasNonLayerViewportConstrainedObjects = 1 << 2,
     88     };
     89 
     90     MainThreadScrollingReasons mainThreadScrollingReasons() const;
     91     bool shouldUpdateScrollLayerPositionOnMainThread() const { return mainThreadScrollingReasons() != 0; }
     92 
     93     void willDestroyScrollableArea(ScrollableArea*);
     94     // Returns true if the coordinator handled this change.
     95     bool scrollableAreaScrollLayerDidChange(ScrollableArea*);
     96     void scrollableAreaScrollbarLayerDidChange(ScrollableArea*, ScrollbarOrientation);
     97     void setLayerIsContainerForFixedPositionLayers(GraphicsLayer*, bool);
     98     void updateLayerPositionConstraint(RenderLayer*);
     99     void touchEventTargetRectsDidChange(const Document*);
    100 
    101     static String mainThreadScrollingReasonsAsText(MainThreadScrollingReasons);
    102     String mainThreadScrollingReasonsAsText() const;
    103     Region computeShouldHandleScrollGestureOnMainThreadRegion(const Frame*, const IntPoint& frameLocation) const;
    104 
    105     class TouchEventTargetRectsObserver {
    106     public:
    107         virtual void touchEventTargetRectsChanged(const LayerHitTestRects&) = 0;
    108     };
    109 
    110     void addTouchEventTargetRectsObserver(TouchEventTargetRectsObserver*);
    111     void removeTouchEventTargetRectsObserver(TouchEventTargetRectsObserver*);
    112 
    113 protected:
    114     explicit ScrollingCoordinator(Page*);
    115 
    116     static GraphicsLayer* scrollLayerForScrollableArea(ScrollableArea*);
    117     static GraphicsLayer* horizontalScrollbarLayerForScrollableArea(ScrollableArea*);
    118     static GraphicsLayer* verticalScrollbarLayerForScrollableArea(ScrollableArea*);
    119     bool isForMainFrame(ScrollableArea*) const;
    120 
    121     unsigned computeCurrentWheelEventHandlerCount();
    122     GraphicsLayer* scrollLayerForFrameView(FrameView*);
    123     GraphicsLayer* counterScrollingLayerForFrameView(FrameView*);
    124 
    125     Page* m_page;
    126 
    127 private:
    128     void recomputeWheelEventHandlerCountForFrameView(FrameView*);
    129     void setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons);
    130 
    131     bool hasVisibleSlowRepaintViewportConstrainedObjects(FrameView*) const;
    132     void updateShouldUpdateScrollLayerPositionOnMainThread();
    133 
    134     static WebKit::WebLayer* scrollingWebLayerForScrollableArea(ScrollableArea*);
    135 
    136     bool touchHitTestingEnabled() const;
    137     void setShouldHandleScrollGestureOnMainThreadRegion(const Region&);
    138     void setTouchEventTargetRects(const LayerHitTestRects&);
    139     void computeTouchEventTargetRects(LayerHitTestRects&);
    140     void setWheelEventHandlerCount(unsigned);
    141 
    142     WebKit::WebScrollbarLayer* addWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation, PassOwnPtr<WebKit::WebScrollbarLayer>);
    143     WebKit::WebScrollbarLayer* getWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation);
    144     void removeWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation);
    145 
    146 
    147     typedef HashMap<ScrollableArea*, OwnPtr<WebKit::WebScrollbarLayer> > ScrollbarMap;
    148     ScrollbarMap m_horizontalScrollbars;
    149     ScrollbarMap m_verticalScrollbars;
    150 
    151     HashSet<TouchEventTargetRectsObserver*> m_touchEventTargetRectsObservers;
    152 };
    153 
    154 } // namespace WebCore
    155 
    156 #endif // ScrollingCoordinator_h
    157