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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/rendering/RenderObject.h"
     30 #include "platform/PlatformWheelEvent.h"
     31 #include "platform/geometry/IntRect.h"
     32 #include "platform/scroll/ScrollTypes.h"
     33 #include "wtf/text/WTFString.h"
     34 
     35 namespace blink {
     36 class WebLayer;
     37 class WebScrollbarLayer;
     38 }
     39 
     40 namespace WebCore {
     41 
     42 typedef unsigned MainThreadScrollingReasons;
     43 
     44 class Document;
     45 class LocalFrame;
     46 class FrameView;
     47 class GraphicsLayer;
     48 class Page;
     49 class Region;
     50 class ScrollableArea;
     51 class ViewportConstraints;
     52 
     53 class ScrollingCoordinator {
     54 public:
     55     ~ScrollingCoordinator();
     56 
     57     static PassOwnPtr<ScrollingCoordinator> create(Page*);
     58 
     59     void willBeDestroyed();
     60 
     61     // Return whether this scrolling coordinator handles scrolling for the given frame view.
     62     bool coordinatesScrollingForFrameView(FrameView*) const;
     63 
     64     // Called when any frame has done its layout.
     65     void notifyLayoutUpdated();
     66 
     67     void updateAfterCompositingChangeIfNeeded();
     68 
     69     void updateHaveWheelEventHandlers();
     70     void updateHaveScrollEventHandlers();
     71 
     72     // Should be called whenever the slow repaint objects counter changes between zero and one.
     73     void frameViewHasSlowRepaintObjectsDidChange(FrameView*);
     74 
     75     // Should be called whenever the set of fixed objects changes.
     76     void frameViewFixedObjectsDidChange(FrameView*);
     77 
     78     // Should be called whenever the root layer for the given frame view changes.
     79     void frameViewRootLayerDidChange(FrameView*);
     80 
     81 #if OS(MACOSX)
     82     // Dispatched by the scrolling tree during handleWheelEvent. This is required as long as scrollbars are painted on the main thread.
     83     void handleWheelEventPhase(PlatformWheelEventPhase);
     84 #endif
     85 
     86     enum MainThreadScrollingReasonFlags {
     87         HasSlowRepaintObjects = 1 << 0,
     88         HasViewportConstrainedObjectsWithoutSupportingFixedLayers = 1 << 1,
     89         HasNonLayerViewportConstrainedObjects = 1 << 2,
     90     };
     91 
     92     MainThreadScrollingReasons mainThreadScrollingReasons() const;
     93     bool shouldUpdateScrollLayerPositionOnMainThread() const { return mainThreadScrollingReasons() != 0; }
     94 
     95     PassOwnPtr<blink::WebScrollbarLayer> createSolidColorScrollbarLayer(ScrollbarOrientation, int thumbThickness, int trackStart, bool isLeftSideVerticalScrollbar);
     96 
     97     void willDestroyScrollableArea(ScrollableArea*);
     98     // Returns true if the coordinator handled this change.
     99     bool scrollableAreaScrollLayerDidChange(ScrollableArea*);
    100     void scrollableAreaScrollbarLayerDidChange(ScrollableArea*, ScrollbarOrientation);
    101     void setLayerIsContainerForFixedPositionLayers(GraphicsLayer*, bool);
    102     void updateLayerPositionConstraint(RenderLayer*);
    103     void touchEventTargetRectsDidChange();
    104     void willDestroyRenderLayer(RenderLayer*);
    105 
    106     void updateScrollParentForGraphicsLayer(GraphicsLayer* child, RenderLayer* parent);
    107     void updateClipParentForGraphicsLayer(GraphicsLayer* child, RenderLayer* parent);
    108 
    109     static String mainThreadScrollingReasonsAsText(MainThreadScrollingReasons);
    110     String mainThreadScrollingReasonsAsText() const;
    111     Region computeShouldHandleScrollGestureOnMainThreadRegion(const LocalFrame*, const IntPoint& frameLocation) const;
    112 
    113     void updateTouchEventTargetRectsIfNeeded();
    114 
    115     // For testing purposes only. This ScrollingCoordinator is reused between layout test, and must be reset
    116     // for the results to be valid.
    117     void reset();
    118 
    119 protected:
    120     explicit ScrollingCoordinator(Page*);
    121 
    122     bool isForMainFrame(ScrollableArea*) const;
    123 
    124     Page* m_page;
    125 
    126     // Dirty flags used to idenfity what really needs to be computed after compositing is updated.
    127     bool m_scrollGestureRegionIsDirty;
    128     bool m_touchEventTargetRectsAreDirty;
    129     bool m_shouldScrollOnMainThreadDirty;
    130 
    131 private:
    132     bool shouldUpdateAfterCompositingChange() const { return m_scrollGestureRegionIsDirty || m_touchEventTargetRectsAreDirty || frameViewIsDirty(); }
    133 
    134     void setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons);
    135 
    136     bool hasVisibleSlowRepaintViewportConstrainedObjects(FrameView*) const;
    137 
    138     bool touchHitTestingEnabled() const;
    139     void setShouldHandleScrollGestureOnMainThreadRegion(const Region&);
    140     void setTouchEventTargetRects(LayerHitTestRects&);
    141     void computeTouchEventTargetRects(LayerHitTestRects&);
    142 
    143     blink::WebScrollbarLayer* addWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation, PassOwnPtr<blink::WebScrollbarLayer>);
    144     blink::WebScrollbarLayer* getWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation);
    145     void removeWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation);
    146 
    147     bool frameViewIsDirty() const;
    148 
    149     typedef HashMap<ScrollableArea*, OwnPtr<blink::WebScrollbarLayer> > ScrollbarMap;
    150     ScrollbarMap m_horizontalScrollbars;
    151     ScrollbarMap m_verticalScrollbars;
    152     HashSet<const RenderLayer*> m_layersWithTouchRects;
    153     bool m_wasFrameScrollable;
    154 
    155     // This is retained for testing.
    156     MainThreadScrollingReasons m_lastMainThreadScrollingReasons;
    157 };
    158 
    159 } // namespace WebCore
    160 
    161 #endif // ScrollingCoordinator_h
    162