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
36using namespace WebCore;
37
38namespace WebKit {
39
40// Computes the distance from a point outside a rect to the nearest edge of the rect.
41static 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
55DragScrollTimer::DragScrollTimer()
56    : m_timer(this, &DragScrollTimer::fired)
57    , m_view(0)
58    , m_scrolling(false)
59{
60}
61
62DragScrollTimer::~DragScrollTimer()
63{
64    // We do this for detecting dead object earlier
65    stop();
66}
67
68void DragScrollTimer::stop()
69{
70    m_timer.stop();
71    m_view = 0;
72    m_scrolling = false;
73}
74
75void DragScrollTimer::scroll()
76{
77    m_view->scrollBy(m_lastDistance);
78    m_scrolling = true;
79}
80
81void DragScrollTimer::update()
82{
83    if (shouldScroll())
84        scroll();
85    else
86        stop();
87}
88
89void 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
106IntSize 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