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      1 /*
      2  * Copyright (c) 2010, Google 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 are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #include "config.h"
     32 #include "platform/scroll/ScrollAnimator.h"
     33 
     34 #include "platform/geometry/FloatPoint.h"
     35 #include "platform/scroll/ScrollableArea.h"
     36 #include "wtf/PassOwnPtr.h"
     37 #include <algorithm>
     38 
     39 namespace blink {
     40 
     41 ScrollAnimator::ScrollAnimator(ScrollableArea* scrollableArea)
     42     : m_scrollableArea(scrollableArea)
     43     , m_currentPosX(0)
     44     , m_currentPosY(0)
     45 {
     46 }
     47 
     48 ScrollAnimator::~ScrollAnimator()
     49 {
     50 }
     51 
     52 bool ScrollAnimator::scroll(ScrollbarOrientation orientation, ScrollGranularity, float step, float delta)
     53 {
     54     float& currentPos = (orientation == HorizontalScrollbar) ? m_currentPosX : m_currentPosY;
     55     float newPos = clampScrollPosition(orientation, currentPos + step * delta);
     56     if (currentPos == newPos)
     57         return false;
     58     currentPos = newPos;
     59 
     60     notifyPositionChanged();
     61 
     62     return true;
     63 }
     64 
     65 void ScrollAnimator::scrollToOffsetWithoutAnimation(const FloatPoint& offset)
     66 {
     67     m_currentPosX = offset.x();
     68     m_currentPosY = offset.y();
     69     notifyPositionChanged();
     70 }
     71 
     72 bool ScrollAnimator::handleWheelEvent(const PlatformWheelEvent& e)
     73 {
     74     bool canScrollX = m_scrollableArea->userInputScrollable(HorizontalScrollbar);
     75     bool canScrollY = m_scrollableArea->userInputScrollable(VerticalScrollbar);
     76 
     77     // Accept the event if we are scrollable in that direction and can still
     78     // scroll any further.
     79     float deltaX = canScrollX ? e.deltaX() : 0;
     80     float deltaY = canScrollY ? e.deltaY() : 0;
     81 
     82     bool handled = false;
     83 
     84 #if !OS(MACOSX)
     85     ScrollGranularity granularity = e.hasPreciseScrollingDeltas() ? ScrollByPrecisePixel : ScrollByPixel;
     86 #else
     87     ScrollGranularity granularity = ScrollByPixel;
     88 #endif
     89 
     90     IntSize maxForwardScrollDelta = m_scrollableArea->maximumScrollPosition() - m_scrollableArea->scrollPosition();
     91     IntSize maxBackwardScrollDelta = m_scrollableArea->scrollPosition() - m_scrollableArea->minimumScrollPosition();
     92     if ((deltaX < 0 && maxForwardScrollDelta.width() > 0)
     93         || (deltaX > 0 && maxBackwardScrollDelta.width() > 0)
     94         || (deltaY < 0 && maxForwardScrollDelta.height() > 0)
     95         || (deltaY > 0 && maxBackwardScrollDelta.height() > 0)) {
     96         handled = true;
     97 
     98         if (deltaY) {
     99             if (e.granularity() == ScrollByPageWheelEvent) {
    100                 bool negative = deltaY < 0;
    101                 deltaY = m_scrollableArea->pageStep(VerticalScrollbar);
    102                 if (negative)
    103                     deltaY = -deltaY;
    104             }
    105 
    106             scroll(VerticalScrollbar, granularity, m_scrollableArea->pixelStep(VerticalScrollbar), -deltaY);
    107         }
    108 
    109         if (deltaX) {
    110             if (e.granularity() == ScrollByPageWheelEvent) {
    111                 bool negative = deltaX < 0;
    112                 deltaX = m_scrollableArea->pageStep(HorizontalScrollbar);
    113                 if (negative)
    114                     deltaX = -deltaX;
    115             }
    116 
    117             scroll(HorizontalScrollbar, granularity, m_scrollableArea->pixelStep(HorizontalScrollbar), -deltaX);
    118         }
    119     }
    120     return handled;
    121 }
    122 
    123 void ScrollAnimator::setCurrentPosition(const FloatPoint& position)
    124 {
    125     m_currentPosX = position.x();
    126     m_currentPosY = position.y();
    127 }
    128 
    129 FloatPoint ScrollAnimator::currentPosition() const
    130 {
    131     return FloatPoint(m_currentPosX, m_currentPosY);
    132 }
    133 
    134 void ScrollAnimator::notifyPositionChanged()
    135 {
    136     m_scrollableArea->setScrollOffsetFromAnimation(IntPoint(m_currentPosX, m_currentPosY));
    137 }
    138 
    139 float ScrollAnimator::clampScrollPosition(ScrollbarOrientation orientation, float pos)
    140 {
    141     float maxScrollPos = m_scrollableArea->maximumScrollPosition(orientation);
    142     float minScrollPos = m_scrollableArea->minimumScrollPosition(orientation);
    143     return std::max(std::min(pos, maxScrollPos), minScrollPos);
    144 }
    145 
    146 } // namespace blink
    147