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      1 /*
      2  * Copyright (C) 2004, 2006, 2008 Apple 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
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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     21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  */
     25 
     26 #include "config.h"
     27 #include "platform/scroll/Scrollbar.h"
     28 
     29 #include <algorithm>
     30 #include "platform/graphics/GraphicsContext.h"
     31 #include "platform/PlatformGestureEvent.h"
     32 #include "platform/PlatformMouseEvent.h"
     33 #include "platform/scroll/ScrollAnimator.h"
     34 #include "platform/scroll/ScrollView.h"
     35 #include "platform/scroll/ScrollableArea.h"
     36 #include "platform/scroll/ScrollbarTheme.h"
     37 
     38 using namespace std;
     39 
     40 #if OS(POSIX) && !OS(MACOSX)
     41 // The position of the scrollbar thumb affects the appearance of the steppers, so
     42 // when the thumb moves, we have to invalidate them for painting.
     43 #define THUMB_POSITION_AFFECTS_BUTTONS
     44 #endif
     45 
     46 namespace WebCore {
     47 
     48 PassRefPtr<Scrollbar> Scrollbar::create(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, ScrollbarControlSize size)
     49 {
     50     return adoptRef(new Scrollbar(scrollableArea, orientation, size));
     51 }
     52 
     53 Scrollbar::Scrollbar(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, ScrollbarControlSize controlSize, ScrollbarTheme* theme)
     54     : m_scrollableArea(scrollableArea)
     55     , m_orientation(orientation)
     56     , m_controlSize(controlSize)
     57     , m_theme(theme)
     58     , m_visibleSize(0)
     59     , m_totalSize(0)
     60     , m_currentPos(0)
     61     , m_dragOrigin(0)
     62     , m_hoveredPart(NoPart)
     63     , m_pressedPart(NoPart)
     64     , m_pressedPos(0)
     65     , m_scrollPos(0)
     66     , m_draggingDocument(false)
     67     , m_documentDragPos(0)
     68     , m_enabled(true)
     69     , m_scrollTimer(this, &Scrollbar::autoscrollTimerFired)
     70     , m_overlapsResizer(false)
     71     , m_suppressInvalidation(false)
     72     , m_isAlphaLocked(false)
     73 {
     74     if (!m_theme)
     75         m_theme = ScrollbarTheme::theme();
     76 
     77     m_theme->registerScrollbar(this);
     78 
     79     // FIXME: This is ugly and would not be necessary if we fix cross-platform code to actually query for
     80     // scrollbar thickness and use it when sizing scrollbars (rather than leaving one dimension of the scrollbar
     81     // alone when sizing).
     82     int thickness = m_theme->scrollbarThickness(controlSize);
     83     Widget::setFrameRect(IntRect(0, 0, thickness, thickness));
     84 
     85     m_currentPos = scrollableAreaCurrentPos();
     86 }
     87 
     88 Scrollbar::~Scrollbar()
     89 {
     90     stopTimerIfNeeded();
     91 
     92     m_theme->unregisterScrollbar(this);
     93 }
     94 
     95 void Scrollbar::removeFromParent()
     96 {
     97     if (parent())
     98         toScrollView(parent())->removeChild(this);
     99 }
    100 
    101 ScrollView* Scrollbar::parentScrollView() const
    102 {
    103     return toScrollView(parent());
    104 }
    105 
    106 ScrollView* Scrollbar::rootScrollView() const
    107 {
    108     return toScrollView(root());
    109 }
    110 
    111 ScrollbarOverlayStyle Scrollbar::scrollbarOverlayStyle() const
    112 {
    113     return m_scrollableArea ? m_scrollableArea->scrollbarOverlayStyle() : ScrollbarOverlayStyleDefault;
    114 }
    115 
    116 void Scrollbar::getTickmarks(Vector<IntRect>& tickmarks) const
    117 {
    118     if (m_scrollableArea)
    119         m_scrollableArea->getTickmarks(tickmarks);
    120 }
    121 
    122 bool Scrollbar::isScrollableAreaActive() const
    123 {
    124     return m_scrollableArea && m_scrollableArea->isActive();
    125 }
    126 
    127 bool Scrollbar::isScrollViewScrollbar() const
    128 {
    129     return parent() && parent()->isFrameView() && toScrollView(parent())->isScrollViewScrollbar(this);
    130 }
    131 
    132 bool Scrollbar::isLeftSideVerticalScrollbar() const
    133 {
    134     if (m_orientation == VerticalScrollbar && m_scrollableArea)
    135         return m_scrollableArea->shouldPlaceVerticalScrollbarOnLeft();
    136     return false;
    137 }
    138 
    139 void Scrollbar::offsetDidChange()
    140 {
    141     ASSERT(m_scrollableArea);
    142 
    143     float position = scrollableAreaCurrentPos();
    144     if (position == m_currentPos)
    145         return;
    146 
    147     int oldThumbPosition = theme()->thumbPosition(this);
    148     m_currentPos = position;
    149     updateThumbPosition();
    150     if (m_pressedPart == ThumbPart)
    151         setPressedPos(m_pressedPos + theme()->thumbPosition(this) - oldThumbPosition);
    152 }
    153 
    154 void Scrollbar::setProportion(int visibleSize, int totalSize)
    155 {
    156     if (visibleSize == m_visibleSize && totalSize == m_totalSize)
    157         return;
    158 
    159     m_visibleSize = visibleSize;
    160     m_totalSize = totalSize;
    161 
    162     updateThumbProportion();
    163 }
    164 
    165 void Scrollbar::updateThumb()
    166 {
    167 #ifdef THUMB_POSITION_AFFECTS_BUTTONS
    168     invalidate();
    169 #else
    170     theme()->invalidateParts(this, ForwardTrackPart | BackTrackPart | ThumbPart);
    171 #endif
    172 }
    173 
    174 void Scrollbar::updateThumbPosition()
    175 {
    176     updateThumb();
    177 }
    178 
    179 void Scrollbar::updateThumbProportion()
    180 {
    181     updateThumb();
    182 }
    183 
    184 void Scrollbar::paint(GraphicsContext* context, const IntRect& damageRect)
    185 {
    186     if (context->updatingControlTints() && theme()->supportsControlTints()) {
    187         invalidate();
    188         return;
    189     }
    190 
    191     if (context->paintingDisabled() || !frameRect().intersects(damageRect))
    192         return;
    193 
    194     if (!theme()->paint(this, context, damageRect))
    195         Widget::paint(context, damageRect);
    196 }
    197 
    198 void Scrollbar::autoscrollTimerFired(Timer<Scrollbar>*)
    199 {
    200     autoscrollPressedPart(theme()->autoscrollTimerDelay());
    201 }
    202 
    203 static bool thumbUnderMouse(Scrollbar* scrollbar)
    204 {
    205     int thumbPos = scrollbar->theme()->trackPosition(scrollbar) + scrollbar->theme()->thumbPosition(scrollbar);
    206     int thumbLength = scrollbar->theme()->thumbLength(scrollbar);
    207     return scrollbar->pressedPos() >= thumbPos && scrollbar->pressedPos() < thumbPos + thumbLength;
    208 }
    209 
    210 void Scrollbar::autoscrollPressedPart(double delay)
    211 {
    212     // Don't do anything for the thumb or if nothing was pressed.
    213     if (m_pressedPart == ThumbPart || m_pressedPart == NoPart)
    214         return;
    215 
    216     // Handle the track.
    217     if ((m_pressedPart == BackTrackPart || m_pressedPart == ForwardTrackPart) && thumbUnderMouse(this)) {
    218         theme()->invalidatePart(this, m_pressedPart);
    219         setHoveredPart(ThumbPart);
    220         return;
    221     }
    222 
    223     // Handle the arrows and track.
    224     if (m_scrollableArea && m_scrollableArea->scroll(pressedPartScrollDirection(), pressedPartScrollGranularity()))
    225         startTimerIfNeeded(delay);
    226 }
    227 
    228 void Scrollbar::startTimerIfNeeded(double delay)
    229 {
    230     // Don't do anything for the thumb.
    231     if (m_pressedPart == ThumbPart)
    232         return;
    233 
    234     // Handle the track.  We halt track scrolling once the thumb is level
    235     // with us.
    236     if ((m_pressedPart == BackTrackPart || m_pressedPart == ForwardTrackPart) && thumbUnderMouse(this)) {
    237         theme()->invalidatePart(this, m_pressedPart);
    238         setHoveredPart(ThumbPart);
    239         return;
    240     }
    241 
    242     // We can't scroll if we've hit the beginning or end.
    243     ScrollDirection dir = pressedPartScrollDirection();
    244     if (dir == ScrollUp || dir == ScrollLeft) {
    245         if (m_currentPos == 0)
    246             return;
    247     } else {
    248         if (m_currentPos == maximum())
    249             return;
    250     }
    251 
    252     m_scrollTimer.startOneShot(delay);
    253 }
    254 
    255 void Scrollbar::stopTimerIfNeeded()
    256 {
    257     if (m_scrollTimer.isActive())
    258         m_scrollTimer.stop();
    259 }
    260 
    261 ScrollDirection Scrollbar::pressedPartScrollDirection()
    262 {
    263     if (m_orientation == HorizontalScrollbar) {
    264         if (m_pressedPart == BackButtonStartPart || m_pressedPart == BackButtonEndPart || m_pressedPart == BackTrackPart)
    265             return ScrollLeft;
    266         return ScrollRight;
    267     } else {
    268         if (m_pressedPart == BackButtonStartPart || m_pressedPart == BackButtonEndPart || m_pressedPart == BackTrackPart)
    269             return ScrollUp;
    270         return ScrollDown;
    271     }
    272 }
    273 
    274 ScrollGranularity Scrollbar::pressedPartScrollGranularity()
    275 {
    276     if (m_pressedPart == BackButtonStartPart || m_pressedPart == BackButtonEndPart ||  m_pressedPart == ForwardButtonStartPart || m_pressedPart == ForwardButtonEndPart)
    277         return ScrollByLine;
    278     return ScrollByPage;
    279 }
    280 
    281 void Scrollbar::moveThumb(int pos, bool draggingDocument)
    282 {
    283     if (!m_scrollableArea)
    284         return;
    285 
    286     int delta = pos - m_pressedPos;
    287 
    288     if (draggingDocument) {
    289         if (m_draggingDocument)
    290             delta = pos - m_documentDragPos;
    291         m_draggingDocument = true;
    292         FloatPoint currentPosition = m_scrollableArea->scrollAnimator()->currentPosition();
    293         float destinationPosition = (m_orientation == HorizontalScrollbar ? currentPosition.x() : currentPosition.y()) + delta;
    294         destinationPosition = m_scrollableArea->clampScrollPosition(m_orientation, destinationPosition);
    295         m_scrollableArea->scrollToOffsetWithoutAnimation(m_orientation, destinationPosition);
    296         m_documentDragPos = pos;
    297         return;
    298     }
    299 
    300     if (m_draggingDocument) {
    301         delta += m_pressedPos - m_documentDragPos;
    302         m_draggingDocument = false;
    303     }
    304 
    305     // Drag the thumb.
    306     int thumbPos = theme()->thumbPosition(this);
    307     int thumbLen = theme()->thumbLength(this);
    308     int trackLen = theme()->trackLength(this);
    309     if (delta > 0)
    310         delta = min(trackLen - thumbLen - thumbPos, delta);
    311     else if (delta < 0)
    312         delta = max(-thumbPos, delta);
    313 
    314     float minPos = m_scrollableArea->minimumScrollPosition(m_orientation);
    315     float maxPos = m_scrollableArea->maximumScrollPosition(m_orientation);
    316     if (delta) {
    317         float newPosition = static_cast<float>(thumbPos + delta) * (maxPos - minPos) / (trackLen - thumbLen) + minPos;
    318         m_scrollableArea->scrollToOffsetWithoutAnimation(m_orientation, newPosition);
    319     }
    320 }
    321 
    322 void Scrollbar::setHoveredPart(ScrollbarPart part)
    323 {
    324     if (part == m_hoveredPart)
    325         return;
    326 
    327     if ((m_hoveredPart == NoPart || part == NoPart) && theme()->invalidateOnMouseEnterExit())
    328         invalidate();  // Just invalidate the whole scrollbar, since the buttons at either end change anyway.
    329     else if (m_pressedPart == NoPart) {  // When there's a pressed part, we don't draw a hovered state, so there's no reason to invalidate.
    330         theme()->invalidatePart(this, part);
    331         theme()->invalidatePart(this, m_hoveredPart);
    332     }
    333     m_hoveredPart = part;
    334 }
    335 
    336 void Scrollbar::setPressedPart(ScrollbarPart part)
    337 {
    338     if (m_pressedPart != NoPart)
    339         theme()->invalidatePart(this, m_pressedPart);
    340     m_pressedPart = part;
    341     if (m_pressedPart != NoPart)
    342         theme()->invalidatePart(this, m_pressedPart);
    343     else if (m_hoveredPart != NoPart)  // When we no longer have a pressed part, we can start drawing a hovered state on the hovered part.
    344         theme()->invalidatePart(this, m_hoveredPart);
    345 }
    346 
    347 bool Scrollbar::gestureEvent(const PlatformGestureEvent& evt)
    348 {
    349     switch (evt.type()) {
    350     case PlatformEvent::GestureTapDown:
    351         setPressedPart(theme()->hitTest(this, evt.position()));
    352         m_pressedPos = orientation() == HorizontalScrollbar ? convertFromContainingWindow(evt.position()).x() : convertFromContainingWindow(evt.position()).y();
    353         return true;
    354     case PlatformEvent::GestureTapDownCancel:
    355     case PlatformEvent::GestureScrollBegin:
    356         if (m_pressedPart != ThumbPart)
    357             return false;
    358         m_scrollPos = m_pressedPos;
    359         return true;
    360     case PlatformEvent::GestureScrollUpdate:
    361     case PlatformEvent::GestureScrollUpdateWithoutPropagation:
    362         if (m_pressedPart != ThumbPart)
    363             return false;
    364         m_scrollPos += orientation() == HorizontalScrollbar ? evt.deltaX() : evt.deltaY();
    365         moveThumb(m_scrollPos, false);
    366         return true;
    367     case PlatformEvent::GestureScrollEnd:
    368     case PlatformEvent::GestureLongPress:
    369     case PlatformEvent::GestureFlingStart:
    370         m_scrollPos = 0;
    371         m_pressedPos = 0;
    372         setPressedPart(NoPart);
    373         return false;
    374     case PlatformEvent::GestureTap: {
    375         if (m_pressedPart != ThumbPart && m_pressedPart != NoPart && m_scrollableArea
    376             && m_scrollableArea->scroll(pressedPartScrollDirection(), pressedPartScrollGranularity())) {
    377             return true;
    378         }
    379         m_scrollPos = 0;
    380         m_pressedPos = 0;
    381         setPressedPart(NoPart);
    382         return false;
    383     }
    384     default:
    385         // By default, we assume that gestures don't deselect the scrollbar.
    386         return true;
    387     }
    388 }
    389 
    390 void Scrollbar::mouseMoved(const PlatformMouseEvent& evt)
    391 {
    392     if (m_pressedPart == ThumbPart) {
    393         if (theme()->shouldSnapBackToDragOrigin(this, evt)) {
    394             if (m_scrollableArea)
    395                 m_scrollableArea->scrollToOffsetWithoutAnimation(m_orientation, m_dragOrigin);
    396         } else {
    397             moveThumb(m_orientation == HorizontalScrollbar ?
    398                       convertFromContainingWindow(evt.position()).x() :
    399                       convertFromContainingWindow(evt.position()).y(), theme()->shouldDragDocumentInsteadOfThumb(this, evt));
    400         }
    401         return;
    402     }
    403 
    404     if (m_pressedPart != NoPart)
    405         m_pressedPos = orientation() == HorizontalScrollbar ? convertFromContainingWindow(evt.position()).x() : convertFromContainingWindow(evt.position()).y();
    406 
    407     ScrollbarPart part = theme()->hitTest(this, evt.position());
    408     if (part != m_hoveredPart) {
    409         if (m_pressedPart != NoPart) {
    410             if (part == m_pressedPart) {
    411                 // The mouse is moving back over the pressed part.  We
    412                 // need to start up the timer action again.
    413                 startTimerIfNeeded(theme()->autoscrollTimerDelay());
    414                 theme()->invalidatePart(this, m_pressedPart);
    415             } else if (m_hoveredPart == m_pressedPart) {
    416                 // The mouse is leaving the pressed part.  Kill our timer
    417                 // if needed.
    418                 stopTimerIfNeeded();
    419                 theme()->invalidatePart(this, m_pressedPart);
    420             }
    421         }
    422 
    423         setHoveredPart(part);
    424     }
    425 
    426     return;
    427 }
    428 
    429 void Scrollbar::mouseEntered()
    430 {
    431     if (m_scrollableArea)
    432         m_scrollableArea->mouseEnteredScrollbar(this);
    433 }
    434 
    435 void Scrollbar::mouseExited()
    436 {
    437     if (m_scrollableArea)
    438         m_scrollableArea->mouseExitedScrollbar(this);
    439     setHoveredPart(NoPart);
    440 }
    441 
    442 void Scrollbar::mouseUp(const PlatformMouseEvent& mouseEvent)
    443 {
    444     setPressedPart(NoPart);
    445     m_pressedPos = 0;
    446     m_draggingDocument = false;
    447     stopTimerIfNeeded();
    448 
    449     if (m_scrollableArea) {
    450         // m_hoveredPart won't be updated until the next mouseMoved or mouseDown, so we have to hit test
    451         // to really know if the mouse has exited the scrollbar on a mouseUp.
    452         ScrollbarPart part = theme()->hitTest(this, mouseEvent.position());
    453         if (part == NoPart)
    454             m_scrollableArea->mouseExitedScrollbar(this);
    455     }
    456 }
    457 
    458 void Scrollbar::mouseDown(const PlatformMouseEvent& evt)
    459 {
    460     // Early exit for right click
    461     if (evt.button() == RightButton)
    462         return;
    463 
    464     setPressedPart(theme()->hitTest(this, evt.position()));
    465     int pressedPos = orientation() == HorizontalScrollbar ? convertFromContainingWindow(evt.position()).x() : convertFromContainingWindow(evt.position()).y();
    466 
    467     if ((m_pressedPart == BackTrackPart || m_pressedPart == ForwardTrackPart) && theme()->shouldCenterOnThumb(this, evt)) {
    468         setHoveredPart(ThumbPart);
    469         setPressedPart(ThumbPart);
    470         m_dragOrigin = m_currentPos;
    471         int thumbLen = theme()->thumbLength(this);
    472         int desiredPos = pressedPos;
    473         // Set the pressed position to the middle of the thumb so that when we do the move, the delta
    474         // will be from the current pixel position of the thumb to the new desired position for the thumb.
    475         m_pressedPos = theme()->trackPosition(this) + theme()->thumbPosition(this) + thumbLen / 2;
    476         moveThumb(desiredPos);
    477         return;
    478     } else if (m_pressedPart == ThumbPart)
    479         m_dragOrigin = m_currentPos;
    480 
    481     m_pressedPos = pressedPos;
    482 
    483     autoscrollPressedPart(theme()->initialAutoscrollTimerDelay());
    484 }
    485 
    486 void Scrollbar::setFrameRect(const IntRect& rect)
    487 {
    488     // Get our window resizer rect and see if we overlap. Adjust to avoid the overlap
    489     // if necessary.
    490     IntRect adjustedRect(rect);
    491     bool overlapsResizer = false;
    492     ScrollView* view = parentScrollView();
    493     if (view && !rect.isEmpty() && !view->windowResizerRect().isEmpty()) {
    494         IntRect resizerRect = view->convertFromContainingWindow(view->windowResizerRect());
    495         if (rect.intersects(resizerRect)) {
    496             if (orientation() == HorizontalScrollbar) {
    497                 int overlap = rect.maxX() - resizerRect.x();
    498                 if (overlap > 0 && resizerRect.maxX() >= rect.maxX()) {
    499                     adjustedRect.setWidth(rect.width() - overlap);
    500                     overlapsResizer = true;
    501                 }
    502             } else {
    503                 int overlap = rect.maxY() - resizerRect.y();
    504                 if (overlap > 0 && resizerRect.maxY() >= rect.maxY()) {
    505                     adjustedRect.setHeight(rect.height() - overlap);
    506                     overlapsResizer = true;
    507                 }
    508             }
    509         }
    510     }
    511     if (overlapsResizer != m_overlapsResizer) {
    512         m_overlapsResizer = overlapsResizer;
    513         if (view)
    514             view->adjustScrollbarsAvoidingResizerCount(m_overlapsResizer ? 1 : -1);
    515     }
    516 
    517     Widget::setFrameRect(adjustedRect);
    518 }
    519 
    520 void Scrollbar::setParent(Widget* parentView)
    521 {
    522     if (!parentView && m_overlapsResizer && parentScrollView())
    523         parentScrollView()->adjustScrollbarsAvoidingResizerCount(-1);
    524     Widget::setParent(parentView);
    525 }
    526 
    527 void Scrollbar::setEnabled(bool e)
    528 {
    529     if (m_enabled == e)
    530         return;
    531     m_enabled = e;
    532     theme()->updateEnabledState(this);
    533     invalidate();
    534 }
    535 
    536 bool Scrollbar::isOverlayScrollbar() const
    537 {
    538     return m_theme->usesOverlayScrollbars();
    539 }
    540 
    541 bool Scrollbar::shouldParticipateInHitTesting()
    542 {
    543     // Non-overlay scrollbars should always participate in hit testing.
    544     if (!isOverlayScrollbar())
    545         return true;
    546     return m_scrollableArea->scrollAnimator()->shouldScrollbarParticipateInHitTesting(this);
    547 }
    548 
    549 bool Scrollbar::isWindowActive() const
    550 {
    551     return m_scrollableArea && m_scrollableArea->isActive();
    552 }
    553 
    554 void Scrollbar::invalidateRect(const IntRect& rect)
    555 {
    556     if (suppressInvalidation())
    557         return;
    558 
    559     if (m_scrollableArea)
    560         m_scrollableArea->invalidateScrollbar(this, rect);
    561 }
    562 
    563 IntRect Scrollbar::convertToContainingView(const IntRect& localRect) const
    564 {
    565     if (m_scrollableArea)
    566         return m_scrollableArea->convertFromScrollbarToContainingView(this, localRect);
    567 
    568     return Widget::convertToContainingView(localRect);
    569 }
    570 
    571 IntRect Scrollbar::convertFromContainingView(const IntRect& parentRect) const
    572 {
    573     if (m_scrollableArea)
    574         return m_scrollableArea->convertFromContainingViewToScrollbar(this, parentRect);
    575 
    576     return Widget::convertFromContainingView(parentRect);
    577 }
    578 
    579 IntPoint Scrollbar::convertToContainingView(const IntPoint& localPoint) const
    580 {
    581     if (m_scrollableArea)
    582         return m_scrollableArea->convertFromScrollbarToContainingView(this, localPoint);
    583 
    584     return Widget::convertToContainingView(localPoint);
    585 }
    586 
    587 IntPoint Scrollbar::convertFromContainingView(const IntPoint& parentPoint) const
    588 {
    589     if (m_scrollableArea)
    590         return m_scrollableArea->convertFromContainingViewToScrollbar(this, parentPoint);
    591 
    592     return Widget::convertFromContainingView(parentPoint);
    593 }
    594 
    595 float Scrollbar::scrollableAreaCurrentPos() const
    596 {
    597     if (!m_scrollableArea)
    598         return 0;
    599 
    600     if (m_orientation == HorizontalScrollbar)
    601         return m_scrollableArea->scrollPosition().x() - m_scrollableArea->minimumScrollPosition().x();
    602 
    603     return m_scrollableArea->scrollPosition().y() - m_scrollableArea->minimumScrollPosition().y();
    604 }
    605 
    606 } // namespace WebCore
    607