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.right() < point.x())

    47         dx = point.x() - rect.right();

    48     if (point.y() < rect.y())

    49         dy = point.y() - rect.y();

    50     else if (rect.bottom() < point.y())

    51         dy = point.y() - rect.bottom();

    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