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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 ScrollElasticityController_h
     27 #define ScrollElasticityController_h
     28 
     29 #if ENABLE(RUBBER_BANDING)
     30 
     31 #include "core/platform/ScrollTypes.h"
     32 #include "core/platform/graphics/FloatPoint.h"
     33 #include "core/platform/graphics/FloatSize.h"
     34 #include "wtf/Noncopyable.h"
     35 
     36 namespace WebCore {
     37 
     38 class PlatformWheelEvent;
     39 
     40 class ScrollElasticityControllerClient {
     41 protected:
     42     virtual ~ScrollElasticityControllerClient() { }
     43 
     44 public:
     45     virtual bool allowsHorizontalStretching() = 0;
     46     virtual bool allowsVerticalStretching() = 0;
     47     virtual IntSize stretchAmount() = 0;
     48     virtual bool pinnedInDirection(const FloatSize&) = 0;
     49     virtual bool canScrollHorizontally() = 0;
     50     virtual bool canScrollVertically() = 0;
     51     virtual bool shouldRubberBandInDirection(ScrollDirection) = 0;
     52 
     53     // Return the absolute scroll position, not relative to the scroll origin.
     54     virtual WebCore::IntPoint absoluteScrollPosition() = 0;
     55 
     56     virtual void immediateScrollBy(const FloatSize&) = 0;
     57     virtual void immediateScrollByWithoutContentEdgeConstraints(const FloatSize&) = 0;
     58     virtual void startSnapRubberbandTimer() = 0;
     59     virtual void stopSnapRubberbandTimer() = 0;
     60 };
     61 
     62 class ScrollElasticityController {
     63     WTF_MAKE_NONCOPYABLE(ScrollElasticityController);
     64 
     65 public:
     66     explicit ScrollElasticityController(ScrollElasticityControllerClient*);
     67 
     68     bool handleWheelEvent(const PlatformWheelEvent&);
     69     void snapRubberBandTimerFired();
     70 
     71     bool isRubberBandInProgress() const;
     72 
     73 private:
     74     void stopSnapRubberbandTimer();
     75     void snapRubberBand();
     76 
     77     bool shouldRubberBandInHorizontalDirection(const PlatformWheelEvent&);
     78 
     79     ScrollElasticityControllerClient* m_client;
     80 
     81     bool m_inScrollGesture;
     82     bool m_momentumScrollInProgress;
     83     bool m_ignoreMomentumScrolls;
     84 
     85     CFTimeInterval m_lastMomentumScrollTimestamp;
     86     FloatSize m_overflowScrollDelta;
     87     FloatSize m_stretchScrollForce;
     88     FloatSize m_momentumVelocity;
     89 
     90     // Rubber band state.
     91     CFTimeInterval m_startTime;
     92     FloatSize m_startStretch;
     93     FloatPoint m_origOrigin;
     94     FloatSize m_origVelocity;
     95 
     96     bool m_snapRubberbandTimerIsActive;
     97 };
     98 
     99 } // namespace WebCore
    100 
    101 #endif // ENABLE(RUBBER_BANDING)
    102 
    103 #endif // ScrollElasticityController_h
    104