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26 #ifndef ScrollElasticityController_h
27 #define ScrollElasticityController_h
29 #if USE(RUBBER_BANDING)
31 #include "platform/PlatformExport.h"
32 #include "platform/geometry/FloatPoint.h"
33 #include "platform/geometry/FloatSize.h"
34 #include "platform/scroll/ScrollTypes.h"
35 #include "wtf/Noncopyable.h"
39 class PlatformWheelEvent;
41 class ScrollElasticityControllerClient {
43 virtual ~ScrollElasticityControllerClient() { }
46 virtual bool allowsHorizontalStretching() = 0;
47 virtual bool allowsVerticalStretching() = 0;
48 // The amount that the view is stretched past the normal allowable bounds.
49 // The "overhang" amount.
50 virtual IntSize stretchAmount() = 0;
51 virtual bool pinnedInDirection(const FloatSize&) = 0;
52 virtual bool canScrollHorizontally() = 0;
53 virtual bool canScrollVertically() = 0;
55 // Return the absolute scroll position, not relative to the scroll origin.
56 virtual blink::IntPoint absoluteScrollPosition() = 0;
58 virtual void immediateScrollBy(const FloatSize&) = 0;
59 virtual void immediateScrollByWithoutContentEdgeConstraints(const FloatSize&) = 0;
60 virtual void startSnapRubberbandTimer() = 0;
61 virtual void stopSnapRubberbandTimer() = 0;
63 // If the current scroll position is within the overhang area, this function will cause
64 // the page to scroll to the nearest boundary point.
65 virtual void adjustScrollPositionToBoundsIfNecessary() = 0;
68 class PLATFORM_EXPORT ScrollElasticityController {
69 WTF_MAKE_NONCOPYABLE(ScrollElasticityController);
72 explicit ScrollElasticityController(ScrollElasticityControllerClient*);
74 // This method is responsible for both scrolling and rubber-banding.
76 // Events are passed by IPC from the embedder. Events on Mac are grouped
77 // into "gestures". If this method returns 'true', then this object has
78 // handled the event. It expects the embedder to continue to forward events
81 // This method makes the assumption that there is only 1 input device being
82 // used at a time. If the user simultaneously uses multiple input devices,
83 // Cocoa does not correctly pass all the gestureBegin/End events. The state
84 // of this class is guaranteed to become eventually consistent, once the
85 // user stops using multiple input devices.
86 bool handleWheelEvent(const PlatformWheelEvent&);
87 void snapRubberBandTimerFired();
89 bool isRubberBandInProgress() const;
92 void stopSnapRubberbandTimer();
93 void snapRubberBand();
95 // This method determines whether a given event should be handled. The
96 // logic for control events of gestures (PhaseBegan, PhaseEnded) is handled
99 // This class handles almost all wheel events. All of the following
100 // conditions must be met for this class to ignore an event:
101 // + No previous events in this gesture have caused any scrolling or rubber
103 // + The event contains a horizontal component.
104 // + The client's view is pinned in the horizontal direction of the event.
105 // + The wheel event disallows rubber banding in the horizontal direction
107 bool shouldHandleEvent(const PlatformWheelEvent&);
109 ScrollElasticityControllerClient* m_client;
111 // There is an active scroll gesture event. This parameter only gets set to
112 // false after the rubber band has been snapped, and before a new gesture
113 // has begun. A careful audit of the code may deprecate the need for this
115 bool m_inScrollGesture;
116 // At least one event in the current gesture has been consumed and has
117 // caused the view to scroll or rubber band. All future events in this
118 // gesture will be consumed and overscrolls will cause rubberbanding.
120 bool m_momentumScrollInProgress;
121 bool m_ignoreMomentumScrolls;
123 CFTimeInterval m_lastMomentumScrollTimestamp;
124 FloatSize m_overflowScrollDelta;
125 FloatSize m_stretchScrollForce;
126 FloatSize m_momentumVelocity;
128 // Rubber band state.
129 CFTimeInterval m_startTime;
130 FloatSize m_startStretch;
131 FloatPoint m_origOrigin;
132 FloatSize m_origVelocity;
134 bool m_snapRubberbandTimerIsActive;
139 #endif // USE(RUBBER_BANDING)
141 #endif // ScrollElasticityController_h