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/*
* Copyright (C) 2014-2015 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:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "AxisScrollSnapOffsets.h"
#include "ElementChildIterator.h"
#include "HTMLElement.h"
#include "Length.h"
#include "Logging.h"
#include "RenderBox.h"
#include "RenderView.h"
#include "ScrollableArea.h"
#include "StyleScrollSnapPoints.h"
#include <wtf/text/StringConcatenateNumbers.h>
#if ENABLE(CSS_SCROLL_SNAP)
namespace WebCore {
enum class InsetOrOutset {
Inset,
Outset
};
static LayoutRect computeScrollSnapPortOrAreaRect(const LayoutRect& rect, const LengthBox& insetOrOutsetBox, InsetOrOutset insetOrOutset)
{
LayoutBoxExtent extents(valueForLength(insetOrOutsetBox.top(), rect.height()), valueForLength(insetOrOutsetBox.right(), rect.width()), valueForLength(insetOrOutsetBox.bottom(), rect.height()), valueForLength(insetOrOutsetBox.left(), rect.width()));
auto snapPortOrArea(rect);
if (insetOrOutset == InsetOrOutset::Inset)
snapPortOrArea.contract(extents);
else
snapPortOrArea.expand(extents);
return snapPortOrArea;
}
static LayoutUnit computeScrollSnapAlignOffset(const LayoutUnit& leftOrTop, const LayoutUnit& widthOrHeight, ScrollSnapAxisAlignType alignment)
{
switch (alignment) {
case ScrollSnapAxisAlignType::Start:
return leftOrTop;
case ScrollSnapAxisAlignType::Center:
return leftOrTop + widthOrHeight / 2;
case ScrollSnapAxisAlignType::End:
return leftOrTop + widthOrHeight;
default:
ASSERT_NOT_REACHED();
return 0;
}
}
#if !LOG_DISABLED
static String snapOffsetsToString(const Vector<LayoutUnit>& snapOffsets)
{
StringBuilder builder;
builder.appendLiteral("[ ");
for (auto& offset : snapOffsets)
builder.append(offset.toFloat(), ' ');
builder.append(']');
return builder.toString();
}
static String snapOffsetRangesToString(const Vector<ScrollOffsetRange<LayoutUnit>>& ranges)
{
StringBuilder builder;
builder.appendLiteral("[ ");
for (auto& range : ranges)
builder.append('(', range.start.toFloat(), ", ", range.end.toFloat(), ") ");
builder.append(']');
return builder.toString();
}
static String snapPortOrAreaToString(const LayoutRect& rect)
{
return makeString("{{", rect.x().toFloat(), ", ", rect.y().toFloat(), "} {", rect.width().toFloat(), ", ", rect.height().toFloat(), "}}");
}
#endif
template <typename LayoutType>
static void indicesOfNearestSnapOffsetRanges(LayoutType offset, const Vector<ScrollOffsetRange<LayoutType>>& snapOffsetRanges, unsigned& lowerIndex, unsigned& upperIndex)
{
if (snapOffsetRanges.isEmpty()) {
lowerIndex = invalidSnapOffsetIndex;
upperIndex = invalidSnapOffsetIndex;
return;
}
int lowerIndexAsInt = -1;
int upperIndexAsInt = snapOffsetRanges.size();
do {
int middleIndex = (lowerIndexAsInt + upperIndexAsInt) / 2;
auto& range = snapOffsetRanges[middleIndex];
if (range.start < offset && offset < range.end) {
lowerIndexAsInt = middleIndex;
upperIndexAsInt = middleIndex;
break;
}
if (offset > range.end)
lowerIndexAsInt = middleIndex;
else
upperIndexAsInt = middleIndex;
} while (lowerIndexAsInt < upperIndexAsInt - 1);
if (offset <= snapOffsetRanges.first().start)
lowerIndex = invalidSnapOffsetIndex;
else
lowerIndex = lowerIndexAsInt;
if (offset >= snapOffsetRanges.last().end)
upperIndex = invalidSnapOffsetIndex;
else
upperIndex = upperIndexAsInt;
}
template <typename LayoutType>
static void indicesOfNearestSnapOffsets(LayoutType offset, const Vector<LayoutType>& snapOffsets, unsigned& lowerIndex, unsigned& upperIndex)
{
lowerIndex = 0;
upperIndex = snapOffsets.size() - 1;
while (lowerIndex < upperIndex - 1) {
int middleIndex = (lowerIndex + upperIndex) / 2;
auto middleOffset = snapOffsets[middleIndex];
if (offset == middleOffset) {
upperIndex = middleIndex;
lowerIndex = middleIndex;
break;
}
if (offset > middleOffset)
lowerIndex = middleIndex;
else
upperIndex = middleIndex;
}
}
static void adjustAxisSnapOffsetsForScrollExtent(Vector<LayoutUnit>& snapOffsets, float maxScrollExtent)
{
if (snapOffsets.isEmpty())
return;
std::sort(snapOffsets.begin(), snapOffsets.end());
if (snapOffsets.last() != maxScrollExtent)
snapOffsets.append(maxScrollExtent);
if (snapOffsets.first())
snapOffsets.insert(0, 0);
}
static void computeAxisProximitySnapOffsetRanges(const Vector<LayoutUnit>& snapOffsets, Vector<ScrollOffsetRange<LayoutUnit>>& offsetRanges, LayoutUnit scrollPortAxisLength)
{
// This is an arbitrary choice for what it means to be "in proximity" of a snap offset. We should play around with
// this and see what feels best.
static const float ratioOfScrollPortAxisLengthToBeConsideredForProximity = 0.3;
if (snapOffsets.size() < 2)
return;
// The extra rule accounting for scroll offset ranges in between the scroll destination and a potential snap offset
// handles the corner case where the user scrolls with momentum very lightly away from a snap offset, such that the
// predicted scroll destination is still within proximity of the snap offset. In this case, the regular (mandatory
// scroll snapping) behavior would be to snap to the next offset in the direction of momentum scrolling, but
// instead, it is more intuitive to either return to the original snap position (which we arbitrarily choose here)
// or scroll just outside of the snap offset range. This is another minor behavior tweak that we should play around
// with to see what feels best.
LayoutUnit proximityDistance { ratioOfScrollPortAxisLengthToBeConsideredForProximity * scrollPortAxisLength };
for (size_t index = 1; index < snapOffsets.size(); ++index) {
auto startOffset = snapOffsets[index - 1] + proximityDistance;
auto endOffset = snapOffsets[index] - proximityDistance;
if (startOffset < endOffset)
offsetRanges.append({ startOffset, endOffset });
}
}
void updateSnapOffsetsForScrollableArea(ScrollableArea& scrollableArea, HTMLElement& scrollingElement, const RenderBox& scrollingElementBox, const RenderStyle& scrollingElementStyle)
{
auto* scrollContainer = scrollingElement.renderer();
auto scrollSnapType = scrollingElementStyle.scrollSnapType();
if (!scrollContainer || scrollSnapType.strictness == ScrollSnapStrictness::None || scrollContainer->view().boxesWithScrollSnapPositions().isEmpty()) {
scrollableArea.clearHorizontalSnapOffsets();
scrollableArea.clearVerticalSnapOffsets();
return;
}
Vector<LayoutUnit> verticalSnapOffsets;
Vector<LayoutUnit> horizontalSnapOffsets;
Vector<ScrollOffsetRange<LayoutUnit>> verticalSnapOffsetRanges;
Vector<ScrollOffsetRange<LayoutUnit>> horizontalSnapOffsetRanges;
HashSet<float> seenVerticalSnapOffsets;
HashSet<float> seenHorizontalSnapOffsets;
bool hasHorizontalSnapOffsets = scrollSnapType.axis == ScrollSnapAxis::Both || scrollSnapType.axis == ScrollSnapAxis::XAxis || scrollSnapType.axis == ScrollSnapAxis::Inline;
bool hasVerticalSnapOffsets = scrollSnapType.axis == ScrollSnapAxis::Both || scrollSnapType.axis == ScrollSnapAxis::YAxis || scrollSnapType.axis == ScrollSnapAxis::Block;
auto maxScrollLeft = scrollingElementBox.scrollWidth() - scrollingElementBox.contentWidth();
auto maxScrollTop = scrollingElementBox.scrollHeight() - scrollingElementBox.contentHeight();
LayoutPoint containerScrollOffset(scrollingElementBox.scrollLeft(), scrollingElementBox.scrollTop());
// The bounds of the scrolling container's snap port, where the top left of the scrolling container's border box is the origin.
auto scrollSnapPort = computeScrollSnapPortOrAreaRect(scrollingElementBox.paddingBoxRect(), scrollingElementStyle.scrollPadding(), InsetOrOutset::Inset);
#if !LOG_DISABLED
LOG(Scrolling, "Computing scroll snap offsets in snap port: %s", snapPortOrAreaToString(scrollSnapPort).utf8().data());
#endif
for (auto* child : scrollContainer->view().boxesWithScrollSnapPositions()) {
if (child->enclosingScrollableContainerForSnapping() != scrollContainer)
continue;
// The bounds of the child element's snap area, where the top left of the scrolling container's border box is the origin.
// The snap area is the bounding box of the child element's border box, after applying transformations.
auto scrollSnapArea = LayoutRect(child->localToContainerQuad(FloatQuad(child->borderBoundingBox()), scrollingElement.renderBox()).boundingBox());
scrollSnapArea.moveBy(containerScrollOffset);
scrollSnapArea = computeScrollSnapPortOrAreaRect(scrollSnapArea, child->style().scrollSnapMargin(), InsetOrOutset::Outset);
#if !LOG_DISABLED
LOG(Scrolling, " Considering scroll snap area: %s", snapPortOrAreaToString(scrollSnapArea).utf8().data());
#endif
auto alignment = child->style().scrollSnapAlign();
if (hasHorizontalSnapOffsets && alignment.x != ScrollSnapAxisAlignType::None) {
auto absoluteScrollOffset = clampTo<LayoutUnit>(computeScrollSnapAlignOffset(scrollSnapArea.x(), scrollSnapArea.width(), alignment.x) - computeScrollSnapAlignOffset(scrollSnapPort.x(), scrollSnapPort.width(), alignment.x), 0, maxScrollLeft);
if (!seenHorizontalSnapOffsets.contains(absoluteScrollOffset)) {
seenHorizontalSnapOffsets.add(absoluteScrollOffset);
horizontalSnapOffsets.append(absoluteScrollOffset);
}
}
if (hasVerticalSnapOffsets && alignment.y != ScrollSnapAxisAlignType::None) {
auto absoluteScrollOffset = clampTo<LayoutUnit>(computeScrollSnapAlignOffset(scrollSnapArea.y(), scrollSnapArea.height(), alignment.y) - computeScrollSnapAlignOffset(scrollSnapPort.y(), scrollSnapPort.height(), alignment.y), 0, maxScrollTop);
if (!seenVerticalSnapOffsets.contains(absoluteScrollOffset)) {
seenVerticalSnapOffsets.add(absoluteScrollOffset);
verticalSnapOffsets.append(absoluteScrollOffset);
}
}
}
if (!horizontalSnapOffsets.isEmpty()) {
adjustAxisSnapOffsetsForScrollExtent(horizontalSnapOffsets, maxScrollLeft);
#if !LOG_DISABLED
LOG(Scrolling, " => Computed horizontal scroll snap offsets: %s", snapOffsetsToString(horizontalSnapOffsets).utf8().data());
LOG(Scrolling, " => Computed horizontal scroll snap offset ranges: %s", snapOffsetRangesToString(horizontalSnapOffsetRanges).utf8().data());
#endif
if (scrollSnapType.strictness == ScrollSnapStrictness::Proximity)
computeAxisProximitySnapOffsetRanges(horizontalSnapOffsets, horizontalSnapOffsetRanges, scrollSnapPort.width());
scrollableArea.setHorizontalSnapOffsets(horizontalSnapOffsets);
scrollableArea.setHorizontalSnapOffsetRanges(horizontalSnapOffsetRanges);
} else
scrollableArea.clearHorizontalSnapOffsets();
if (!verticalSnapOffsets.isEmpty()) {
adjustAxisSnapOffsetsForScrollExtent(verticalSnapOffsets, maxScrollTop);
#if !LOG_DISABLED
LOG(Scrolling, " => Computed vertical scroll snap offsets: %s", snapOffsetsToString(verticalSnapOffsets).utf8().data());
LOG(Scrolling, " => Computed vertical scroll snap offset ranges: %s", snapOffsetRangesToString(verticalSnapOffsetRanges).utf8().data());
#endif
if (scrollSnapType.strictness == ScrollSnapStrictness::Proximity)
computeAxisProximitySnapOffsetRanges(verticalSnapOffsets, verticalSnapOffsetRanges, scrollSnapPort.height());
scrollableArea.setVerticalSnapOffsets(verticalSnapOffsets);
scrollableArea.setVerticalSnapOffsetRanges(verticalSnapOffsetRanges);
} else
scrollableArea.clearVerticalSnapOffsets();
}
template <typename LayoutType>
LayoutType closestSnapOffset(const Vector<LayoutType>& snapOffsets, const Vector<ScrollOffsetRange<LayoutType>>& snapOffsetRanges, LayoutType scrollDestination, float velocity, unsigned& activeSnapIndex)
{
ASSERT(snapOffsets.size());
activeSnapIndex = 0;
unsigned lowerSnapOffsetRangeIndex;
unsigned upperSnapOffsetRangeIndex;
indicesOfNearestSnapOffsetRanges<LayoutType>(scrollDestination, snapOffsetRanges, lowerSnapOffsetRangeIndex, upperSnapOffsetRangeIndex);
if (lowerSnapOffsetRangeIndex == upperSnapOffsetRangeIndex && upperSnapOffsetRangeIndex != invalidSnapOffsetIndex) {
activeSnapIndex = invalidSnapOffsetIndex;
return scrollDestination;
}
if (scrollDestination <= snapOffsets.first())
return snapOffsets.first();
activeSnapIndex = snapOffsets.size() - 1;
if (scrollDestination >= snapOffsets.last())
return snapOffsets.last();
unsigned lowerIndex;
unsigned upperIndex;
indicesOfNearestSnapOffsets<LayoutType>(scrollDestination, snapOffsets, lowerIndex, upperIndex);
LayoutType lowerSnapPosition = snapOffsets[lowerIndex];
LayoutType upperSnapPosition = snapOffsets[upperIndex];
if (!std::abs(velocity)) {
bool isCloserToLowerSnapPosition = scrollDestination - lowerSnapPosition <= upperSnapPosition - scrollDestination;
activeSnapIndex = isCloserToLowerSnapPosition ? lowerIndex : upperIndex;
return isCloserToLowerSnapPosition ? lowerSnapPosition : upperSnapPosition;
}
// Non-zero velocity indicates a flick gesture. Even if another snap point is closer, we should choose the one in the direction of the flick gesture
// as long as a scroll snap offset range does not lie between the scroll destination and the targeted snap offset.
if (velocity < 0) {
if (lowerSnapOffsetRangeIndex != invalidSnapOffsetIndex && lowerSnapPosition < snapOffsetRanges[lowerSnapOffsetRangeIndex].end) {
activeSnapIndex = upperIndex;
return upperSnapPosition;
}
activeSnapIndex = lowerIndex;
return lowerSnapPosition;
}
if (upperSnapOffsetRangeIndex != invalidSnapOffsetIndex && snapOffsetRanges[upperSnapOffsetRangeIndex].start < upperSnapPosition) {
activeSnapIndex = lowerIndex;
return lowerSnapPosition;
}
activeSnapIndex = upperIndex;
return upperSnapPosition;
}
LayoutUnit closestSnapOffset(const Vector<LayoutUnit>& snapOffsets, const Vector<ScrollOffsetRange<LayoutUnit>>& snapOffsetRanges, LayoutUnit scrollDestination, float velocity, unsigned& activeSnapIndex)
{
return closestSnapOffset<LayoutUnit>(snapOffsets, snapOffsetRanges, scrollDestination, velocity, activeSnapIndex);
}
float closestSnapOffset(const Vector<float>& snapOffsets, const Vector<ScrollOffsetRange<float>>& snapOffsetRanges, float scrollDestination, float velocity, unsigned& activeSnapIndex)
{
return closestSnapOffset<float>(snapOffsets, snapOffsetRanges, scrollDestination, velocity, activeSnapIndex);
}
} // namespace WebCore
#endif // CSS_SCROLL_SNAP