void updateSnapOffsetsForScrollableArea(ScrollableArea& scrollableArea, HTMLElement& scrollingElement, const RenderBox& scrollingElementBox, const RenderStyle& scrollingElementStyle)
{
if (scrollingElementStyle.scrollSnapType() == ScrollSnapType::None) {
scrollableArea.clearHorizontalSnapOffsets();
scrollableArea.clearVerticalSnapOffsets();
return;
}
LayoutUnit viewWidth = scrollingElementBox.width();
LayoutUnit viewHeight = scrollingElementBox.height();
LayoutUnit scrollWidth = scrollingElementBox.scrollWidth();
LayoutUnit scrollHeight = scrollingElementBox.scrollHeight();
bool canComputeHorizontalOffsets = scrollWidth > 0 && viewWidth > 0 && viewWidth < scrollWidth;
bool canComputeVerticalOffsets = scrollHeight > 0 && viewHeight > 0 && viewHeight < scrollHeight;
if (!canComputeHorizontalOffsets)
scrollableArea.clearHorizontalSnapOffsets();
if (!canComputeVerticalOffsets)
scrollableArea.clearVerticalSnapOffsets();
if (!canComputeHorizontalOffsets && !canComputeVerticalOffsets)
return;
Vector<LayoutUnit> horizontalSnapOffsetSubsequence;
Vector<LayoutUnit> verticalSnapOffsetSubsequence;
bool scrollSnapPointsXUsesElements = styleUsesElements(ScrollEventAxis::Horizontal, scrollingElementStyle);
bool scrollSnapPointsYUsesElements = styleUsesElements(ScrollEventAxis::Vertical , scrollingElementStyle);
if (scrollSnapPointsXUsesElements || scrollSnapPointsYUsesElements) {
bool shouldAddHorizontalChildOffsets = scrollSnapPointsXUsesElements && canComputeHorizontalOffsets;
bool shouldAddVerticalChildOffsets = scrollSnapPointsYUsesElements && canComputeVerticalOffsets;
appendChildSnapOffsets(scrollingElement, shouldAddHorizontalChildOffsets, horizontalSnapOffsetSubsequence, shouldAddVerticalChildOffsets, verticalSnapOffsetSubsequence);
}
if (scrollingElementStyle.scrollSnapPointsX() && !scrollSnapPointsXUsesElements && canComputeHorizontalOffsets) {
for (auto& snapLength : scrollingElementStyle.scrollSnapPointsX()->offsets)
horizontalSnapOffsetSubsequence.append(valueForLength(snapLength, viewWidth));
}
if (scrollingElementStyle.scrollSnapPointsY() && !scrollSnapPointsYUsesElements && canComputeVerticalOffsets) {
for (auto& snapLength : scrollingElementStyle.scrollSnapPointsY()->offsets)
verticalSnapOffsetSubsequence.append(valueForLength(snapLength, viewHeight));
}
if (canComputeHorizontalOffsets) {
auto horizontalSnapOffsets = std::make_unique<Vector<LayoutUnit>>();
updateFromStyle(*horizontalSnapOffsets, scrollingElementStyle, ScrollEventAxis::Horizontal, viewWidth, scrollWidth, horizontalSnapOffsetSubsequence);
scrollableArea.setHorizontalSnapOffsets(WTF::move(horizontalSnapOffsets));
}
if (canComputeVerticalOffsets) {
auto verticalSnapOffsets = std::make_unique<Vector<LayoutUnit>>();
updateFromStyle(*verticalSnapOffsets, scrollingElementStyle, ScrollEventAxis::Vertical, viewHeight, scrollHeight, verticalSnapOffsetSubsequence);
scrollableArea.setVerticalSnapOffsets(WTF::move(verticalSnapOffsets));
}
}
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->findEnclosingScrollableContainer() != 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();
}