Move scroll elasticity files from blink to content

content/renderer/input/input_scroll_elasticity_controller.h

+/*
+ * Copyright (C) 2011 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef ScrollElasticityController_h
+#define ScrollElasticityController_h
+
+#if USE(RUBBER_BANDING)
+
+// #include "platform/PlatformExport.h"
+// #include "platform/geometry/FloatPoint.h"
+// #include "platform/geometry/FloatSize.h"
+// #include "platform/scroll/ScrollTypes.h"
+// #include "wtf/Noncopyable.h"
+
+namespace blink {
+
+class PlatformWheelEvent;
+
+class ScrollElasticityControllerClient {
+protected:
+    virtual ~ScrollElasticityControllerClient() { }
+
+public:
+    virtual bool allowsHorizontalStretching() = 0;
+    virtual bool allowsVerticalStretching() = 0;
+    // The amount that the view is stretched past the normal allowable bounds.
+    // The "overhang" amount.
+    virtual IntSize stretchAmount() = 0;
+    virtual bool pinnedInDirection(const FloatSize&) = 0;
+    virtual bool canScrollHorizontally() = 0;
+    virtual bool canScrollVertically() = 0;
+
+    // Return the absolute scroll position, not relative to the scroll origin.
+    virtual blink::IntPoint absoluteScrollPosition() = 0;
+
+    virtual void immediateScrollBy(const FloatSize&) = 0;
+    virtual void immediateScrollByWithoutContentEdgeConstraints(const FloatSize&) = 0;
+    virtual void startSnapRubberbandTimer() = 0;
+    virtual void stopSnapRubberbandTimer() = 0;
+
+    // If the current scroll position is within the overhang area, this function will cause
+    // the page to scroll to the nearest boundary point.
+    virtual void adjustScrollPositionToBoundsIfNecessary() = 0;
+};
+
+class PLATFORM_EXPORT ScrollElasticityController {
+    WTF_MAKE_NONCOPYABLE(ScrollElasticityController);
+
+public:
+    explicit ScrollElasticityController(ScrollElasticityControllerClient*);
+
+    // This method is responsible for both scrolling and rubber-banding.
+    //
+    // Events are passed by IPC from the embedder. Events on Mac are grouped
+    // into "gestures". If this method returns 'true', then this object has
+    // handled the event. It expects the embedder to continue to forward events
+    // from the gesture.
+    //
+    // This method makes the assumption that there is only 1 input device being
+    // used at a time. If the user simultaneously uses multiple input devices,
+    // Cocoa does not correctly pass all the gestureBegin/End events. The state
+    // of this class is guaranteed to become eventually consistent, once the
+    // user stops using multiple input devices.
+    bool handleWheelEvent(const PlatformWheelEvent&);
+    void snapRubberBandTimerFired();
+
+    bool isRubberBandInProgress() const;
+
+private:
+    void stopSnapRubberbandTimer();
+    void snapRubberBand();
+
+    // This method determines whether a given event should be handled. The
+    // logic for control events of gestures (PhaseBegan, PhaseEnded) is handled
+    // elsewhere.
+    //
+    // This class handles almost all wheel events. All of the following
+    // conditions must be met for this class to ignore an event:
+    // + No previous events in this gesture have caused any scrolling or rubber
+    // banding.
+    // + The event contains a horizontal component.
+    // + The client's view is pinned in the horizontal direction of the event.
+    // + The wheel event disallows rubber banding in the horizontal direction
+    // of the event.
+    bool shouldHandleEvent(const PlatformWheelEvent&);
+
+    ScrollElasticityControllerClient* m_client;
+
+    // There is an active scroll gesture event. This parameter only gets set to
+    // false after the rubber band has been snapped, and before a new gesture
+    // has begun. A careful audit of the code may deprecate the need for this
+    // parameter.
+    bool m_inScrollGesture;
+    // At least one event in the current gesture has been consumed and has
+    // caused the view to scroll or rubber band. All future events in this
+    // gesture will be consumed and overscrolls will cause rubberbanding.
+    bool m_hasScrolled;
+    bool m_momentumScrollInProgress;
+    bool m_ignoreMomentumScrolls;
+
+    CFTimeInterval m_lastMomentumScrollTimestamp;
+    FloatSize m_overflowScrollDelta;
+    FloatSize m_stretchScrollForce;
+    FloatSize m_momentumVelocity;
+
+    // Rubber band state.
+    CFTimeInterval m_startTime;
+    FloatSize m_startStretch;
+    FloatPoint m_origOrigin;
+    FloatSize m_origVelocity;
+
+    bool m_snapRubberbandTimerIsActive;
+};
+
+} // namespace blink
+
+#endif // USE(RUBBER_BANDING)
+
+#endif // ScrollElasticityController_h