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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 "DragScrollTimer.h"
     33 
     34 #include "FrameView.h"
     35 
     36 using namespace WebCore;
     37 
     38 namespace WebKit {
     39 
     40 // Computes the distance from a point outside a rect to the nearest edge of the rect.
     41 static IntSize distanceToRect(const IntPoint& point, const IntRect& rect)
     42 {
     43     int dx = 0, dy = 0;
     44     if (point.x() < rect.x())
     45         dx = point.x() - rect.x();
     46     else if (rect.maxX() < point.x())
     47         dx = point.x() - rect.maxX();
     48     if (point.y() < rect.y())
     49         dy = point.y() - rect.y();
     50     else if (rect.maxY() < point.y())
     51         dy = point.y() - rect.maxY();
     52     return IntSize(dx, dy);
     53 }
     54 
     55 DragScrollTimer::DragScrollTimer()
     56     : m_timer(this, &DragScrollTimer::fired)
     57     , m_view(0)
     58     , m_scrolling(false)
     59 {
     60 }
     61 
     62 DragScrollTimer::~DragScrollTimer()
     63 {
     64     // We do this for detecting dead object earlier
     65     stop();
     66 }
     67 
     68 void DragScrollTimer::stop()
     69 {
     70     m_timer.stop();
     71     m_view = 0;
     72     m_scrolling = false;
     73 }
     74 
     75 void DragScrollTimer::scroll()
     76 {
     77     m_view->scrollBy(m_lastDistance);
     78     m_scrolling = true;
     79 }
     80 
     81 void DragScrollTimer::update()
     82 {
     83     if (shouldScroll())
     84         scroll();
     85     else
     86         stop();
     87 }
     88 
     89 void DragScrollTimer::triggerScroll(FrameView* view, const WebPoint& location)
     90 {
     91     if (!view)
     92         return;
     93 
     94     // Approximates Safari
     95     static const double scrollStartDelay = 0.2;
     96 
     97     m_view = view;
     98     m_lastDistance = scrollDistanceFor(view, location);
     99 
    100     if (m_scrolling)
    101         update();
    102     else if (shouldScroll() && !m_timer.isActive())
    103         m_timer.startOneShot(scrollStartDelay);
    104 }
    105 
    106 IntSize DragScrollTimer::scrollDistanceFor(FrameView* view, const WebPoint& location) const
    107 {
    108     static const int scrollMargin = 30;
    109 
    110     IntRect bounds(0, 0, view->visibleWidth(), view->visibleHeight());
    111     if (!bounds.contains(location))
    112         return IntSize(0, 0); // The location is outside the border belt.
    113 
    114     bounds.setY(bounds.y() + scrollMargin);
    115     bounds.setHeight(bounds.height() - scrollMargin * 2);
    116     bounds.setX(bounds.x() + scrollMargin);
    117     bounds.setWidth(bounds.width() - scrollMargin * 2);
    118 
    119     if (bounds.contains(location))
    120         return IntSize(0, 0); // The location is inside the border belt.
    121 
    122     // The location is over the border belt.
    123     return distanceToRect(location, bounds);
    124 }
    125 
    126 } // namespace WebKit
    127