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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 WebScrollbarLayer;
     37 }
     38 
     39 namespace blink {
     40 
     41 typedef unsigned MainThreadScrollingReasons;
     42 
     43 class LocalFrame;
     44 class FrameView;
     45 class GraphicsLayer;
     46 class Page;
     47 class Region;
     48 class ScrollableArea;
     49 
     50 class ScrollingCoordinator {
     51 public:
     52     ~ScrollingCoordinator();
     53 
     54     static PassOwnPtr<ScrollingCoordinator> create(Page*);
     55 
     56     void willBeDestroyed();
     57 
     58     // Return whether this scrolling coordinator handles scrolling for the given frame view.
     59     bool coordinatesScrollingForFrameView(FrameView*) const;
     60 
     61     // Called when any frame has done its layout.
     62     void notifyLayoutUpdated();
     63 
     64     void updateAfterCompositingChangeIfNeeded();
     65 
     66     void updateHaveWheelEventHandlers();
     67     void updateHaveScrollEventHandlers();
     68 
     69     // Should be called whenever the slow repaint objects counter changes between zero and one.
     70     void frameViewHasSlowRepaintObjectsDidChange(FrameView*);
     71 
     72     // Should be called whenever the set of fixed objects changes.
     73     void frameViewFixedObjectsDidChange(FrameView*);
     74 
     75     // Should be called whenever the root layer for the given frame view changes.
     76     void frameViewRootLayerDidChange(FrameView*);
     77 
     78 #if OS(MACOSX)
     79     // Dispatched by the scrolling tree during handleWheelEvent. This is required as long as scrollbars are painted on the main thread.
     80     void handleWheelEventPhase(PlatformWheelEventPhase);
     81 #endif
     82 
     83     enum MainThreadScrollingReasonFlags {
     84         HasSlowRepaintObjects = 1 << 0,
     85         HasViewportConstrainedObjectsWithoutSupportingFixedLayers = 1 << 1,
     86         HasNonLayerViewportConstrainedObjects = 1 << 2,
     87         ThreadedScrollingDisabled = 1 << 3
     88     };
     89 
     90     MainThreadScrollingReasons mainThreadScrollingReasons() const;
     91     bool shouldUpdateScrollLayerPositionOnMainThread() const { return mainThreadScrollingReasons() != 0; }
     92 
     93     PassOwnPtr<blink::WebScrollbarLayer> createSolidColorScrollbarLayer(ScrollbarOrientation, int thumbThickness, int trackStart, bool isLeftSideVerticalScrollbar);
     94 
     95     void willDestroyScrollableArea(ScrollableArea*);
     96     // Returns true if the coordinator handled this change.
     97     bool scrollableAreaScrollLayerDidChange(ScrollableArea*);
     98     void scrollableAreaScrollbarLayerDidChange(ScrollableArea*, ScrollbarOrientation);
     99     void setLayerIsContainerForFixedPositionLayers(GraphicsLayer*, bool);
    100     void updateLayerPositionConstraint(RenderLayer*);
    101     void touchEventTargetRectsDidChange();
    102     void willDestroyRenderLayer(RenderLayer*);
    103 
    104     void updateScrollParentForGraphicsLayer(GraphicsLayer* child, RenderLayer* parent);
    105     void updateClipParentForGraphicsLayer(GraphicsLayer* child, RenderLayer* parent);
    106 
    107     static String mainThreadScrollingReasonsAsText(MainThreadScrollingReasons);
    108     String mainThreadScrollingReasonsAsText() const;
    109     Region computeShouldHandleScrollGestureOnMainThreadRegion(const LocalFrame*, const IntPoint& frameLocation) const;
    110 
    111     void updateTouchEventTargetRectsIfNeeded();
    112 
    113     // For testing purposes only. This ScrollingCoordinator is reused between layout test, and must be reset
    114     // for the results to be valid.
    115     void reset();
    116 
    117 protected:
    118     explicit ScrollingCoordinator(Page*);
    119 
    120     bool isForMainFrame(ScrollableArea*) const;
    121 
    122     Page* m_page;
    123 
    124     // Dirty flags used to idenfity what really needs to be computed after compositing is updated.
    125     bool m_scrollGestureRegionIsDirty;
    126     bool m_touchEventTargetRectsAreDirty;
    127     bool m_shouldScrollOnMainThreadDirty;
    128 
    129 private:
    130     bool shouldUpdateAfterCompositingChange() const { return m_scrollGestureRegionIsDirty || m_touchEventTargetRectsAreDirty || frameViewIsDirty(); }
    131 
    132     void setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons);
    133 
    134     bool hasVisibleSlowRepaintViewportConstrainedObjects(FrameView*) const;
    135 
    136     void setShouldHandleScrollGestureOnMainThreadRegion(const Region&);
    137     void setTouchEventTargetRects(LayerHitTestRects&);
    138     void computeTouchEventTargetRects(LayerHitTestRects&);
    139 
    140     blink::WebScrollbarLayer* addWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation, PassOwnPtr<blink::WebScrollbarLayer>);
    141     blink::WebScrollbarLayer* getWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation);
    142     void removeWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation);
    143 
    144     bool frameViewIsDirty() const;
    145 
    146     typedef HashMap<ScrollableArea*, OwnPtr<blink::WebScrollbarLayer> > ScrollbarMap;
    147     ScrollbarMap m_horizontalScrollbars;
    148     ScrollbarMap m_verticalScrollbars;
    149     HashSet<const RenderLayer*> m_layersWithTouchRects;
    150     bool m_wasFrameScrollable;
    151 
    152     // This is retained for testing.
    153     MainThreadScrollingReasons m_lastMainThreadScrollingReasons;
    154 };
    155 
    156 } // namespace blink
    157 
    158 #endif // ScrollingCoordinator_h
    159