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/*
* Copyright (c) 2010, Google Inc. All rights reserved.
* Copyright (C) 2008, 2011, 2014-2016 Apple Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
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* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "ScrollableArea.h"
#include "FloatPoint.h"
#include "GraphicsContext.h"
#include "GraphicsLayer.h"
#include "LayoutRect.h"
#include "Logging.h"
#include "PlatformWheelEvent.h"
#include "ScrollAnimator.h"
#include "ScrollAnimatorMock.h"
#include "ScrollbarTheme.h"
#include <wtf/text/TextStream.h>
namespace WebCore {
struct SameSizeAsScrollableArea {
virtual ~SameSizeAsScrollableArea();
#if ASSERT_ENABLED
bool weakPtrFactorWasConstructedOnMainThread;
#endif
#if ENABLE(CSS_SCROLL_SNAP)
void* pointers[3];
unsigned currentIndices[2];
#else
void* pointer[2];
#endif
IntPoint origin;
unsigned bitfields : 16;
};
COMPILE_ASSERT(sizeof(ScrollableArea) == sizeof(SameSizeAsScrollableArea), ScrollableArea_should_stay_small);
ScrollableArea::ScrollableArea()
: m_constrainsScrollingToContentEdge(true)
, m_inLiveResize(false)
, m_verticalScrollElasticity(ScrollElasticityNone)
, m_horizontalScrollElasticity(ScrollElasticityNone)
, m_scrollbarOverlayStyle(ScrollbarOverlayStyleDefault)
, m_scrollOriginChanged(false)
, m_currentScrollType(static_cast<unsigned>(ScrollType::User))
, m_scrollShouldClearLatchedState(false)
, m_currentScrollBehaviorStatus(static_cast<unsigned>(ScrollBehaviorStatus::NotInAnimation))
{
}
ScrollableArea::~ScrollableArea() = default;
ScrollAnimator& ScrollableArea::scrollAnimator() const
{
if (!m_scrollAnimator) {
if (usesMockScrollAnimator()) {
m_scrollAnimator = makeUnique<ScrollAnimatorMock>(const_cast<ScrollableArea&>(*this), [this](const String& message) {
logMockScrollAnimatorMessage(message);
});
} else
m_scrollAnimator = ScrollAnimator::create(const_cast<ScrollableArea&>(*this));
}
ASSERT(m_scrollAnimator);
return *m_scrollAnimator.get();
}
void ScrollableArea::setScrollOrigin(const IntPoint& origin)
{
if (m_scrollOrigin != origin) {
m_scrollOrigin = origin;
m_scrollOriginChanged = true;
}
}
float ScrollableArea::adjustScrollStepForFixedContent(float step, ScrollbarOrientation, ScrollGranularity)
{
return step;
}
bool ScrollableArea::scroll(ScrollDirection direction, ScrollGranularity granularity, float multiplier)
{
ScrollbarOrientation orientation;
Scrollbar* scrollbar;
if (direction == ScrollUp || direction == ScrollDown) {
orientation = VerticalScrollbar;
scrollbar = verticalScrollbar();
} else {
orientation = HorizontalScrollbar;
scrollbar = horizontalScrollbar();
}
if (!scrollbar)
return false;
float step = 0;
switch (granularity) {
case ScrollByLine:
step = scrollbar->lineStep();
break;
case ScrollByPage:
step = scrollbar->pageStep();
break;
case ScrollByDocument:
step = scrollbar->totalSize();
break;
case ScrollByPixel:
step = scrollbar->pixelStep();
break;
}
if (direction == ScrollUp || direction == ScrollLeft)
multiplier = -multiplier;
step = adjustScrollStepForFixedContent(step, orientation, granularity);
return scrollAnimator().scroll(orientation, granularity, step, multiplier);
}
void ScrollableArea::scrollToOffsetWithAnimation(const FloatPoint& offset, ScrollClamping)
{
LOG_WITH_STREAM(Scrolling, stream << "ScrollableArea " << this << " scrollToOffsetWithAnimation " << offset);
scrollAnimator().scrollToOffset(offset);
}
void ScrollableArea::scrollToOffsetWithoutAnimation(const FloatPoint& offset, ScrollClamping clamping)
{
LOG_WITH_STREAM(Scrolling, stream << "ScrollableArea " << this << " scrollToOffsetWithoutAnimation " << offset);
scrollAnimator().scrollToOffsetWithoutAnimation(offset, clamping);
}
void ScrollableArea::scrollToOffsetWithoutAnimation(ScrollbarOrientation orientation, float offset)
{
auto currentOffset = scrollOffsetFromPosition(IntPoint(scrollAnimator().currentPosition()));
if (orientation == HorizontalScrollbar)
scrollToOffsetWithoutAnimation(FloatPoint(offset, currentOffset.y()));
else
scrollToOffsetWithoutAnimation(FloatPoint(currentOffset.x(), offset));
}
void ScrollableArea::notifyScrollPositionChanged(const ScrollPosition& position)
{
scrollPositionChanged(position);
scrollAnimator().setCurrentPosition(position);
}
void ScrollableArea::scrollPositionChanged(const ScrollPosition& position)
{
IntPoint oldPosition = scrollPosition();
// Tell the derived class to scroll its contents.
setScrollOffset(scrollOffsetFromPosition(position));
Scrollbar* verticalScrollbar = this->verticalScrollbar();
// Tell the scrollbars to update their thumb postions.
if (Scrollbar* horizontalScrollbar = this->horizontalScrollbar()) {
horizontalScrollbar->offsetDidChange();
if (horizontalScrollbar->isOverlayScrollbar() && !hasLayerForHorizontalScrollbar()) {
if (!verticalScrollbar)
horizontalScrollbar->invalidate();
else {
// If there is both a horizontalScrollbar and a verticalScrollbar,
// then we must also invalidate the corner between them.
IntRect boundsAndCorner = horizontalScrollbar->boundsRect();
boundsAndCorner.setWidth(boundsAndCorner.width() + verticalScrollbar->width());
horizontalScrollbar->invalidateRect(boundsAndCorner);
}
}
}
if (verticalScrollbar) {
verticalScrollbar->offsetDidChange();
if (verticalScrollbar->isOverlayScrollbar() && !hasLayerForVerticalScrollbar())
verticalScrollbar->invalidate();
}
if (scrollPosition() != oldPosition)
scrollAnimator().notifyContentAreaScrolled(scrollPosition() - oldPosition);
}
bool ScrollableArea::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
{
if (!isScrollableOrRubberbandable())
return false;
bool handledEvent = scrollAnimator().handleWheelEvent(wheelEvent);
#if ENABLE(CSS_SCROLL_SNAP)
if (scrollAnimator().activeScrollSnapIndexDidChange()) {
setCurrentHorizontalSnapPointIndex(scrollAnimator().activeScrollSnapIndexForAxis(ScrollEventAxis::Horizontal));
setCurrentVerticalSnapPointIndex(scrollAnimator().activeScrollSnapIndexForAxis(ScrollEventAxis::Vertical));
}
#endif
return handledEvent;
}
#if ENABLE(TOUCH_EVENTS)
bool ScrollableArea::handleTouchEvent(const PlatformTouchEvent& touchEvent)
{
return scrollAnimator().handleTouchEvent(touchEvent);
}
#endif
// NOTE: Only called from Internals for testing.
void ScrollableArea::setScrollOffsetFromInternals(const ScrollOffset& offset)
{
setScrollOffsetFromAnimation(offset);
}
void ScrollableArea::setScrollOffsetFromAnimation(const ScrollOffset& offset)
{
ScrollPosition position = scrollPositionFromOffset(offset);
if (requestScrollPositionUpdate(position, currentScrollType()))
return;
scrollPositionChanged(position);
}
void ScrollableArea::willStartLiveResize()
{
if (m_inLiveResize)
return;
m_inLiveResize = true;
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->willStartLiveResize();
}
void ScrollableArea::willEndLiveResize()
{
if (!m_inLiveResize)
return;
m_inLiveResize = false;
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->willEndLiveResize();
}
void ScrollableArea::contentAreaWillPaint() const
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->contentAreaWillPaint();
}
void ScrollableArea::mouseEnteredContentArea() const
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->mouseEnteredContentArea();
}
void ScrollableArea::mouseExitedContentArea() const
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->mouseExitedContentArea();
}
void ScrollableArea::mouseMovedInContentArea() const
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->mouseMovedInContentArea();
}
void ScrollableArea::mouseEnteredScrollbar(Scrollbar* scrollbar) const
{
scrollAnimator().mouseEnteredScrollbar(scrollbar);
}
void ScrollableArea::mouseExitedScrollbar(Scrollbar* scrollbar) const
{
scrollAnimator().mouseExitedScrollbar(scrollbar);
}
void ScrollableArea::mouseIsDownInScrollbar(Scrollbar* scrollbar, bool mouseIsDown) const
{
scrollAnimator().mouseIsDownInScrollbar(scrollbar, mouseIsDown);
}
void ScrollableArea::contentAreaDidShow() const
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->contentAreaDidShow();
}
void ScrollableArea::contentAreaDidHide() const
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->contentAreaDidHide();
}
void ScrollableArea::lockOverlayScrollbarStateToHidden(bool shouldLockState) const
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->lockOverlayScrollbarStateToHidden(shouldLockState);
}
bool ScrollableArea::scrollbarsCanBeActive() const
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
return scrollAnimator->scrollbarsCanBeActive();
return true;
}
void ScrollableArea::didAddScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
{
if (orientation == VerticalScrollbar)
scrollAnimator().didAddVerticalScrollbar(scrollbar);
else
scrollAnimator().didAddHorizontalScrollbar(scrollbar);
// <rdar://problem/9797253> AppKit resets the scrollbar's style when you attach a scrollbar
setScrollbarOverlayStyle(scrollbarOverlayStyle());
}
void ScrollableArea::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
{
if (orientation == VerticalScrollbar)
scrollAnimator().willRemoveVerticalScrollbar(scrollbar);
else
scrollAnimator().willRemoveHorizontalScrollbar(scrollbar);
}
void ScrollableArea::contentsResized()
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->contentsResized();
}
void ScrollableArea::availableContentSizeChanged(AvailableSizeChangeReason)
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->contentsResized(); // This flashes overlay scrollbars.
}
bool ScrollableArea::hasOverlayScrollbars() const
{
return (verticalScrollbar() && verticalScrollbar()->isOverlayScrollbar())
|| (horizontalScrollbar() && horizontalScrollbar()->isOverlayScrollbar());
}
void ScrollableArea::setScrollbarOverlayStyle(ScrollbarOverlayStyle overlayStyle)
{
m_scrollbarOverlayStyle = overlayStyle;
if (horizontalScrollbar()) {
ScrollbarTheme::theme().updateScrollbarOverlayStyle(*horizontalScrollbar());
horizontalScrollbar()->invalidate();
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->invalidateScrollbarPartLayers(horizontalScrollbar());
}
if (verticalScrollbar()) {
ScrollbarTheme::theme().updateScrollbarOverlayStyle(*verticalScrollbar());
verticalScrollbar()->invalidate();
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->invalidateScrollbarPartLayers(verticalScrollbar());
}
}
bool ScrollableArea::useDarkAppearanceForScrollbars() const
{
// If dark appearance is used or the overlay style is light (because of a dark page background), set the dark appearance.
return useDarkAppearance() || scrollbarOverlayStyle() == WebCore::ScrollbarOverlayStyleLight;
}
void ScrollableArea::invalidateScrollbar(Scrollbar& scrollbar, const IntRect& rect)
{
if (&scrollbar == horizontalScrollbar()) {
if (GraphicsLayer* graphicsLayer = layerForHorizontalScrollbar()) {
graphicsLayer->setNeedsDisplay();
graphicsLayer->setContentsNeedsDisplay();
return;
}
} else if (&scrollbar == verticalScrollbar()) {
if (GraphicsLayer* graphicsLayer = layerForVerticalScrollbar()) {
graphicsLayer->setNeedsDisplay();
graphicsLayer->setContentsNeedsDisplay();
return;
}
}
invalidateScrollbarRect(scrollbar, rect);
}
void ScrollableArea::invalidateScrollCorner(const IntRect& rect)
{
if (GraphicsLayer* graphicsLayer = layerForScrollCorner()) {
graphicsLayer->setNeedsDisplay();
return;
}
invalidateScrollCornerRect(rect);
}
void ScrollableArea::verticalScrollbarLayerDidChange()
{
scrollAnimator().verticalScrollbarLayerDidChange();
}
void ScrollableArea::horizontalScrollbarLayerDidChange()
{
scrollAnimator().horizontalScrollbarLayerDidChange();
}
bool ScrollableArea::hasLayerForHorizontalScrollbar() const
{
return layerForHorizontalScrollbar();
}
bool ScrollableArea::hasLayerForVerticalScrollbar() const
{
return layerForVerticalScrollbar();
}
bool ScrollableArea::hasLayerForScrollCorner() const
{
return layerForScrollCorner();
}
#if ENABLE(CSS_SCROLL_SNAP)
ScrollSnapOffsetsInfo<LayoutUnit>& ScrollableArea::ensureSnapOffsetsInfo()
{
if (!m_snapOffsetsInfo)
m_snapOffsetsInfo = makeUnique<ScrollSnapOffsetsInfo<LayoutUnit>>();
return *m_snapOffsetsInfo;
}
const Vector<LayoutUnit>* ScrollableArea::horizontalSnapOffsets() const
{
if (!m_snapOffsetsInfo)
return nullptr;
return &m_snapOffsetsInfo->horizontalSnapOffsets;
}
const Vector<ScrollOffsetRange<LayoutUnit>>* ScrollableArea::horizontalSnapOffsetRanges() const
{
if (!m_snapOffsetsInfo)
return nullptr;
return &m_snapOffsetsInfo->horizontalSnapOffsetRanges;
}
const Vector<ScrollOffsetRange<LayoutUnit>>* ScrollableArea::verticalSnapOffsetRanges() const
{
if (!m_snapOffsetsInfo)
return nullptr;
return &m_snapOffsetsInfo->verticalSnapOffsetRanges;
}
const Vector<LayoutUnit>* ScrollableArea::verticalSnapOffsets() const
{
if (!m_snapOffsetsInfo)
return nullptr;
return &m_snapOffsetsInfo->verticalSnapOffsets;
}
void ScrollableArea::setHorizontalSnapOffsets(const Vector<LayoutUnit>& horizontalSnapOffsets)
{
// Consider having a non-empty set of snap offsets as a cue to initialize the ScrollAnimator.
if (horizontalSnapOffsets.size())
scrollAnimator();
ensureSnapOffsetsInfo().horizontalSnapOffsets = horizontalSnapOffsets;
}
void ScrollableArea::setVerticalSnapOffsets(const Vector<LayoutUnit>& verticalSnapOffsets)
{
// Consider having a non-empty set of snap offsets as a cue to initialize the ScrollAnimator.
if (verticalSnapOffsets.size())
scrollAnimator();
ensureSnapOffsetsInfo().verticalSnapOffsets = verticalSnapOffsets;
}
void ScrollableArea::setHorizontalSnapOffsetRanges(const Vector<ScrollOffsetRange<LayoutUnit>>& horizontalRanges)
{
ensureSnapOffsetsInfo().horizontalSnapOffsetRanges = horizontalRanges;
}
void ScrollableArea::setVerticalSnapOffsetRanges(const Vector<ScrollOffsetRange<LayoutUnit>>& verticalRanges)
{
ensureSnapOffsetsInfo().verticalSnapOffsetRanges = verticalRanges;
}
void ScrollableArea::clearHorizontalSnapOffsets()
{
if (!m_snapOffsetsInfo)
return;
m_snapOffsetsInfo->horizontalSnapOffsets = { };
m_snapOffsetsInfo->horizontalSnapOffsetRanges = { };
m_currentHorizontalSnapPointIndex = 0;
}
void ScrollableArea::clearVerticalSnapOffsets()
{
if (!m_snapOffsetsInfo)
return;
m_snapOffsetsInfo->verticalSnapOffsets = { };
m_snapOffsetsInfo->verticalSnapOffsetRanges = { };
m_currentVerticalSnapPointIndex = 0;
}
IntPoint ScrollableArea::nearestActiveSnapPoint(const IntPoint& currentPosition)
{
if (!horizontalSnapOffsets() && !verticalSnapOffsets())
return currentPosition;
if (!existingScrollAnimator())
return currentPosition;
IntPoint correctedPosition = currentPosition;
if (horizontalSnapOffsets()) {
const auto& horizontal = *horizontalSnapOffsets();
size_t activeIndex = currentHorizontalSnapPointIndex();
if (activeIndex < horizontal.size())
correctedPosition.setX(horizontal[activeIndex].toInt());
}
if (verticalSnapOffsets()) {
const auto& vertical = *verticalSnapOffsets();
size_t activeIndex = currentVerticalSnapPointIndex();
if (activeIndex < vertical.size())
correctedPosition.setY(vertical[activeIndex].toInt());
}
return correctedPosition;
}
void ScrollableArea::updateScrollSnapState()
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->updateScrollSnapState();
if (isScrollSnapInProgress())
return;
IntPoint currentPosition = scrollPosition();
IntPoint correctedPosition = nearestActiveSnapPoint(currentPosition);
if (correctedPosition != currentPosition)
scrollToOffsetWithoutAnimation(correctedPosition);
}
#else
void ScrollableArea::updateScrollSnapState()
{
}
#endif
void ScrollableArea::serviceScrollAnimations()
{
if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
scrollAnimator->serviceScrollAnimations();
}
bool ScrollableArea::isPinnedInBothDirections(const IntSize& scrollDelta) const
{
return isPinnedHorizontallyInDirection(scrollDelta.width()) && isPinnedVerticallyInDirection(scrollDelta.height());
}
bool ScrollableArea::isPinnedHorizontallyInDirection(int horizontalScrollDelta) const
{
if (horizontalScrollDelta < 0 && isHorizontalScrollerPinnedToMinimumPosition())
return true;
if (horizontalScrollDelta > 0 && isHorizontalScrollerPinnedToMaximumPosition())
return true;
return false;
}
bool ScrollableArea::isPinnedVerticallyInDirection(int verticalScrollDelta) const
{
if (verticalScrollDelta < 0 && isVerticalScrollerPinnedToMinimumPosition())
return true;
if (verticalScrollDelta > 0 && isVerticalScrollerPinnedToMaximumPosition())
return true;
return false;
}
int ScrollableArea::horizontalScrollbarIntrusion() const
{
return verticalScrollbar() ? verticalScrollbar()->occupiedWidth() : 0;
}
int ScrollableArea::verticalScrollbarIntrusion() const
{
return horizontalScrollbar() ? horizontalScrollbar()->occupiedHeight() : 0;
}
IntSize ScrollableArea::scrollbarIntrusion() const
{
return { horizontalScrollbarIntrusion(), verticalScrollbarIntrusion() };
}
ScrollOffset ScrollableArea::scrollOffset() const
{
return scrollOffsetFromPosition(scrollPosition());
}
ScrollPosition ScrollableArea::minimumScrollPosition() const
{
return scrollPositionFromOffset(ScrollPosition());
}
ScrollPosition ScrollableArea::maximumScrollPosition() const
{
return scrollPositionFromOffset(ScrollPosition(totalContentsSize() - visibleSize()));
}
ScrollOffset ScrollableArea::maximumScrollOffset() const
{
return ScrollOffset(totalContentsSize() - visibleSize());
}
ScrollPosition ScrollableArea::scrollPositionFromOffset(ScrollOffset offset) const
{
return scrollPositionFromOffset(offset, toIntSize(m_scrollOrigin));
}
ScrollOffset ScrollableArea::scrollOffsetFromPosition(ScrollPosition position) const
{
return scrollOffsetFromPosition(position, toIntSize(m_scrollOrigin));
}
bool ScrollableArea::scrolledToTop() const
{
return scrollPosition().y() <= minimumScrollPosition().y();
}
bool ScrollableArea::scrolledToBottom() const
{
return scrollPosition().y() >= maximumScrollPosition().y();
}
bool ScrollableArea::scrolledToLeft() const
{
return scrollPosition().x() <= minimumScrollPosition().x();
}
bool ScrollableArea::scrolledToRight() const
{
return scrollPosition().x() >= maximumScrollPosition().x();
}
void ScrollableArea::scrollbarStyleChanged(ScrollbarStyle, bool)
{
availableContentSizeChanged(AvailableSizeChangeReason::ScrollbarsChanged);
}
IntSize ScrollableArea::reachableTotalContentsSize() const
{
return totalContentsSize();
}
IntSize ScrollableArea::totalContentsSize() const
{
IntSize totalContentsSize = contentsSize();
totalContentsSize.setHeight(totalContentsSize.height() + headerHeight() + footerHeight());
return totalContentsSize;
}
IntRect ScrollableArea::visibleContentRect(VisibleContentRectBehavior visibleContentRectBehavior) const
{
return visibleContentRectInternal(ExcludeScrollbars, visibleContentRectBehavior);
}
IntRect ScrollableArea::visibleContentRectIncludingScrollbars(VisibleContentRectBehavior visibleContentRectBehavior) const
{
return visibleContentRectInternal(IncludeScrollbars, visibleContentRectBehavior);
}
IntRect ScrollableArea::visibleContentRectInternal(VisibleContentRectIncludesScrollbars scrollbarInclusion, VisibleContentRectBehavior) const
{
int verticalScrollbarWidth = 0;
int horizontalScrollbarHeight = 0;
if (scrollbarInclusion == IncludeScrollbars) {
if (Scrollbar* verticalBar = verticalScrollbar())
verticalScrollbarWidth = verticalBar->occupiedWidth();
if (Scrollbar* horizontalBar = horizontalScrollbar())
horizontalScrollbarHeight = horizontalBar->occupiedHeight();
}
return IntRect(scrollPosition().x(),
scrollPosition().y(),
std::max(0, visibleWidth() + verticalScrollbarWidth),
std::max(0, visibleHeight() + horizontalScrollbarHeight));
}
LayoutPoint ScrollableArea::constrainScrollPositionForOverhang(const LayoutRect& visibleContentRect, const LayoutSize& totalContentsSize, const LayoutPoint& scrollPosition, const LayoutPoint& scrollOrigin, int headerHeight, int footerHeight)
{
// The viewport rect that we're scrolling shouldn't be larger than our document.
LayoutSize idealScrollRectSize(std::min(visibleContentRect.width(), totalContentsSize.width()), std::min(visibleContentRect.height(), totalContentsSize.height()));
LayoutRect scrollRect(scrollPosition + scrollOrigin - LayoutSize(0, headerHeight), idealScrollRectSize);
LayoutRect documentRect(LayoutPoint(), LayoutSize(totalContentsSize.width(), totalContentsSize.height() - headerHeight - footerHeight));
// Use intersection to constrain our ideal scroll rect by the document rect.
scrollRect.intersect(documentRect);
if (scrollRect.size() != idealScrollRectSize) {
// If the rect was clipped, restore its size, effectively pushing it "down" from the top left.
scrollRect.setSize(idealScrollRectSize);
// If we still clip, push our rect "up" from the bottom right.
scrollRect.intersect(documentRect);
if (scrollRect.width() < idealScrollRectSize.width())
scrollRect.move(-(idealScrollRectSize.width() - scrollRect.width()), 0_lu);
if (scrollRect.height() < idealScrollRectSize.height())
scrollRect.move(0_lu, -(idealScrollRectSize.height() - scrollRect.height()));
}
return scrollRect.location() - toLayoutSize(scrollOrigin);
}
LayoutPoint ScrollableArea::constrainScrollPositionForOverhang(const LayoutPoint& scrollPosition)
{
return constrainScrollPositionForOverhang(visibleContentRect(), totalContentsSize(), scrollPosition, scrollOrigin(), headerHeight(), footerHeight());
}
void ScrollableArea::computeScrollbarValueAndOverhang(float currentPosition, float totalSize, float visibleSize, float& doubleValue, float& overhangAmount)
{
doubleValue = 0;
overhangAmount = 0;
float maximum = totalSize - visibleSize;
if (currentPosition < 0) {
// Scrolled past the top.
doubleValue = 0;
overhangAmount = -currentPosition;
} else if (visibleSize + currentPosition > totalSize) {
// Scrolled past the bottom.
doubleValue = 1;
overhangAmount = currentPosition + visibleSize - totalSize;
} else {
// Within the bounds of the scrollable area.
if (maximum > 0)
doubleValue = currentPosition / maximum;
else
doubleValue = 0;
}
}
} // namespace WebCore