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/*
* Copyright (C) 2018 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
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*/
#include "config.h"
#include "BlockFormattingContext.h"
#if ENABLE(LAYOUT_FORMATTING_CONTEXT)
#include "BlockFormattingState.h"
#include "FloatingContext.h"
#include "FloatingState.h"
#include "InvalidationState.h"
#include "LayoutBox.h"
#include "LayoutChildIterator.h"
#include "LayoutContainerBox.h"
#include "LayoutContext.h"
#include "LayoutState.h"
#include "Logging.h"
#include <wtf/IsoMallocInlines.h>
#include <wtf/text/TextStream.h>
namespace WebCore {
namespace Layout {
WTF_MAKE_ISO_ALLOCATED_IMPL(BlockFormattingContext);
BlockFormattingContext::BlockFormattingContext(const ContainerBox& formattingContextRoot, BlockFormattingState& formattingState)
: FormattingContext(formattingContextRoot, formattingState)
{
}
void BlockFormattingContext::layoutInFlowContent(InvalidationState& invalidationState, const HorizontalConstraints& rootHorizontalConstraints, const VerticalConstraints& rootVerticalConstraints)
{
// 9.4.1 Block formatting contexts
// In a block formatting context, boxes are laid out one after the other, vertically, beginning at the top of a containing block.
// The vertical distance between two sibling boxes is determined by the 'margin' properties.
// Vertical margins between adjacent block-level boxes in a block formatting context collapse.
LOG_WITH_STREAM(FormattingContextLayout, stream << "[Start] -> block formatting context -> formatting root(" << &root() << ")");
auto& formattingRoot = root();
ASSERT(formattingRoot.hasInFlowOrFloatingChild());
auto floatingContext = FloatingContext { formattingRoot, *this, formattingState().floatingState() };
LayoutQueue layoutQueue;
enum class LayoutDirection { Child, Sibling };
auto appendNextToLayoutQueue = [&] (const auto& layoutBox, auto direction) {
if (direction == LayoutDirection::Child) {
if (!is<ContainerBox>(layoutBox))
return false;
for (auto* child = downcast<ContainerBox>(layoutBox).firstInFlowOrFloatingChild(); child; child = child->nextInFlowOrFloatingSibling()) {
if (!invalidationState.needsLayout(*child))
continue;
layoutQueue.append(child);
return true;
}
return false;
}
if (direction == LayoutDirection::Sibling) {
for (auto* nextSibling = layoutBox.nextInFlowOrFloatingSibling(); nextSibling; nextSibling = nextSibling->nextInFlowOrFloatingSibling()) {
if (!invalidationState.needsLayout(*nextSibling))
continue;
layoutQueue.append(nextSibling);
return true;
}
return false;
}
ASSERT_NOT_REACHED();
return false;
};
auto horizontalConstraintsForLayoutBox = [&] (const auto& layoutBox) -> ConstraintsPair<HorizontalConstraints> {
auto* containingBlock = layoutBox.containingBlock();
ASSERT(containingBlock);
if (containingBlock == &formattingRoot)
return { rootHorizontalConstraints, rootHorizontalConstraints };
return { rootHorizontalConstraints, Geometry::horizontalConstraintsForInFlow(geometryForBox(*containingBlock)) };
};
auto verticalConstraintsForLayoutBox = [&] (const auto& layoutBox) -> ConstraintsPair<VerticalConstraints> {
auto* containingBlock = layoutBox.containingBlock();
ASSERT(containingBlock);
if (containingBlock == &formattingRoot)
return { rootVerticalConstraints, rootVerticalConstraints };
return { rootVerticalConstraints, Geometry::verticalConstraintsForInFlow(geometryForBox(*containingBlock)) };
};
// This is a post-order tree traversal layout.
// The root container layout is done in the formatting context it lives in, not that one it creates, so let's start with the first child.
appendNextToLayoutQueue(formattingRoot, LayoutDirection::Child);
// 1. Go all the way down to the leaf node
// 2. Compute static position and width as we traverse down
// 3. As we climb back on the tree, compute height and finialize position
// (Any subtrees with new formatting contexts need to layout synchronously)
while (!layoutQueue.isEmpty()) {
// Traverse down on the descendants and compute width/static position until we find a leaf node.
while (true) {
auto& layoutBox = *layoutQueue.last();
auto horizontalConstraints = horizontalConstraintsForLayoutBox(layoutBox);
auto verticalConstraints = verticalConstraintsForLayoutBox(layoutBox);
computeBorderAndPadding(layoutBox, horizontalConstraints.containingBlock);
computeStaticVerticalPosition(layoutBox, verticalConstraints);
computeWidthAndMargin(floatingContext, layoutBox, horizontalConstraints);
computeStaticHorizontalPosition(layoutBox, horizontalConstraints);
if (layoutBox.establishesFormattingContext()) {
if (is<ContainerBox>(layoutBox) && downcast<ContainerBox>(layoutBox).hasInFlowOrFloatingChild()) {
// Layout the inflow descendants of this formatting context root.
precomputeVerticalPositionForFormattingRoot(floatingContext, layoutBox, horizontalConstraints, verticalConstraints);
auto& rootDisplayBox = geometryForBox(layoutBox);
auto horizontalConstraintsForFormattingContext = Geometry::horizontalConstraintsForInFlow(rootDisplayBox);
auto verticalConstraintsForFormattingContext = Geometry::verticalConstraintsForInFlow(rootDisplayBox);
LayoutContext::createFormattingContext(downcast<ContainerBox>(layoutBox), layoutState())->layoutInFlowContent(invalidationState, horizontalConstraintsForFormattingContext, verticalConstraintsForFormattingContext);
}
break;
}
if (!appendNextToLayoutQueue(layoutBox, LayoutDirection::Child))
break;
}
// Climb back on the ancestors and compute height/final position.
while (!layoutQueue.isEmpty()) {
auto& layoutBox = *layoutQueue.takeLast();
auto horizontalConstraints = horizontalConstraintsForLayoutBox(layoutBox);
auto verticalConstraints = verticalConstraintsForLayoutBox(layoutBox);
// All inflow descendants (if there are any) are laid out by now. Let's compute the box's height.
computeHeightAndMargin(layoutBox, horizontalConstraints, verticalConstraints);
if (layoutBox.establishesFormattingContext()) {
// Now that we computed the root's height, we can layout the out-of-flow descendants.
if (is<ContainerBox>(layoutBox) && downcast<ContainerBox>(layoutBox).hasChild()) {
auto& rootDisplayBox = geometryForBox(layoutBox);
auto horizontalConstraintsForOutOfFlow = Geometry::horizontalConstraintsForOutOfFlow(rootDisplayBox);
auto verticalConstraintsForOutOfFlow = Geometry::verticalConstraintsForOutOfFlow(rootDisplayBox);
LayoutContext::createFormattingContext(downcast<ContainerBox>(layoutBox), layoutState())->layoutOutOfFlowContent(invalidationState, horizontalConstraintsForOutOfFlow, verticalConstraintsForOutOfFlow);
}
}
// Resolve final positions.
placeInFlowPositionedChildren(layoutBox, horizontalConstraints);
if (layoutBox.isFloatAvoider()) {
computePositionToAvoidFloats(floatingContext, layoutBox, horizontalConstraints, verticalConstraints);
if (layoutBox.isFloatingPositioned())
floatingContext.append(layoutBox);
}
if (appendNextToLayoutQueue(layoutBox, LayoutDirection::Sibling))
break;
}
}
// Place the inflow positioned children.
placeInFlowPositionedChildren(formattingRoot, ConstraintsPair<HorizontalConstraints> { rootHorizontalConstraints, rootHorizontalConstraints });
LOG_WITH_STREAM(FormattingContextLayout, stream << "[End] -> block formatting context -> formatting root(" << &root() << ")");
}
Optional<LayoutUnit> BlockFormattingContext::usedAvailableWidthForFloatAvoider(const FloatingContext& floatingContext, const Box& layoutBox) const
{
// Normally the available width for an in-flow block level box is the width of the containing block's content box.
// However (and can't find it anywhere in the spec) non-floating positioned float avoider block level boxes are constrained by existing floats.
ASSERT(layoutBox.isFloatAvoider());
if (floatingContext.isEmpty())
return { };
// Vertical static position is not computed yet, so let's just pre-compute it for now.
auto verticalPosition = mapTopToFormattingContextRoot(layoutBox);
// FIXME: Check if the non-yet-computed height affects this computation - and whether we have to resolve it
// at a later point or not (can't find this in the spec).
auto constraints = floatingContext.constraints(verticalPosition, verticalPosition);
if (!constraints.left && !constraints.right)
return { };
auto& containingBlock = *layoutBox.containingBlock();
auto& containingBlockGeometry = geometryForBox(containingBlock);
auto availableWidth = containingBlockGeometry.contentBoxWidth();
LayoutUnit containingBlockLeft;
LayoutUnit containingBlockRight = containingBlockGeometry.right();
if (&containingBlock != &root()) {
// Move containing block left/right to the root's coordinate system.
containingBlockLeft = mapLeftToFormattingContextRoot(containingBlock);
containingBlockRight = mapRightToFormattingContextRoot(containingBlock);
}
auto containingBlockContentBoxLeft = containingBlockLeft + containingBlockGeometry.borderLeft() + containingBlockGeometry.paddingLeft().valueOr(0);
auto containingBlockContentBoxRight = containingBlockRight - containingBlockGeometry.borderRight() + containingBlockGeometry.paddingRight().valueOr(0);
// Shrink the available space if the floats are actually intruding at this vertical position.
if (constraints.left)
availableWidth -= std::max<LayoutUnit>(0, constraints.left->x - containingBlockContentBoxLeft);
if (constraints.right)
availableWidth -= std::max<LayoutUnit>(0, containingBlockContentBoxRight - constraints.right->x);
return availableWidth;
}
void BlockFormattingContext::placeInFlowPositionedChildren(const Box& layoutBox, const ConstraintsPair<HorizontalConstraints>& horizontalConstraints)
{
if (!is<ContainerBox>(layoutBox))
return;
LOG_WITH_STREAM(FormattingContextLayout, stream << "Start: move in-flow positioned children -> parent: " << &layoutBox);
auto& containerBox = downcast<ContainerBox>(layoutBox);
for (auto& childBox : childrenOfType<Box>(containerBox)) {
if (!childBox.isInFlowPositioned())
continue;
auto positionOffset = geometry().inFlowPositionedPositionOffset(childBox, horizontalConstraints.containingBlock);
formattingState().displayBox(childBox).move(positionOffset);
}
LOG_WITH_STREAM(FormattingContextLayout, stream << "End: move in-flow positioned children -> parent: " << &layoutBox);
}
void BlockFormattingContext::computeStaticVerticalPosition(const Box& layoutBox, const ConstraintsPair<VerticalConstraints>& verticalConstraints)
{
formattingState().displayBox(layoutBox).setTop(geometry().staticVerticalPosition(layoutBox, verticalConstraints.containingBlock));
}
void BlockFormattingContext::computeStaticHorizontalPosition(const Box& layoutBox, const ConstraintsPair<HorizontalConstraints>& horizontalConstraints)
{
formattingState().displayBox(layoutBox).setLeft(geometry().staticHorizontalPosition(layoutBox, horizontalConstraints.containingBlock));
}
void BlockFormattingContext::precomputeVerticalPosition(const Box& layoutBox, const HorizontalConstraints& horizontalConstraints, const VerticalConstraints& verticalConstraints)
{
auto computedVerticalMargin = geometry().computedVerticalMargin(layoutBox, horizontalConstraints);
auto usedNonCollapsedMargin = UsedVerticalMargin::NonCollapsedValues { computedVerticalMargin.before.valueOr(0), computedVerticalMargin.after.valueOr(0) };
auto precomputedMarginBefore = marginCollapse().precomputedMarginBefore(layoutBox, usedNonCollapsedMargin);
setPrecomputedMarginBefore(layoutBox, precomputedMarginBefore);
auto& displayBox = formattingState().displayBox(layoutBox);
auto nonCollapsedValues = UsedVerticalMargin::NonCollapsedValues { precomputedMarginBefore.nonCollapsedValue, { } };
auto collapsedValues = UsedVerticalMargin::CollapsedValues { precomputedMarginBefore.collapsedValue, { }, precomputedMarginBefore.isCollapsedThrough };
auto verticalMargin = UsedVerticalMargin { nonCollapsedValues, collapsedValues };
displayBox.setVerticalMargin(verticalMargin);
displayBox.setTop(verticalPositionWithMargin(layoutBox, verticalMargin, verticalConstraints));
#if ASSERT_ENABLED
displayBox.setHasPrecomputedMarginBefore();
#endif
}
void BlockFormattingContext::precomputeVerticalPositionForAncestors(const Box& layoutBox, const ConstraintsPair<HorizontalConstraints>& horizontalConstraints, const ConstraintsPair<VerticalConstraints>& verticalConstraints)
{
// We only need to pre-compute the margin top for float related layout (formatting context roots avoid floats).
ASSERT(layoutBox.isFloatAvoider() || layoutBox.establishesInlineFormattingContext());
// In order to figure out whether a box should avoid a float, we need to know the final positions of both (ignore relative positioning for now).
// In block formatting context the final position for a normal flow box includes
// 1. the static position and
// 2. the corresponding (non)collapsed margins.
// Now the vertical margins are computed when all the descendants are finalized, because the margin values might be depending on the height of the box
// (and the height might be based on the content).
// So when we get to the point where we intersect the box with the float to decide if the box needs to move, we don't yet have the final vertical position.
//
// The idea here is that as long as we don't cross the block formatting context boundary, we should be able to pre-compute the final top position.
// FIXME: we currently don't account for the "clear" property when computing the final position for an ancestor.
for (auto* ancestor = layoutBox.containingBlock(); ancestor && !ancestor->establishesBlockFormattingContext(); ancestor = ancestor->containingBlock()) {
// FIXME: with incremental layout, we might actually have a valid (non-precomputed) margin top as well.
if (hasPrecomputedMarginBefore(*ancestor))
return;
auto horizontalConstraintsForAncestor = [&] {
auto* containingBlock = layoutBox.containingBlock();
return containingBlock == &root() ? horizontalConstraints.root : Geometry::horizontalConstraintsForInFlow(geometryForBox(*containingBlock));
};
auto verticalConstraintsForAncestor = [&] {
auto* containingBlock = layoutBox.containingBlock();
return containingBlock == &root() ? verticalConstraints.root : Geometry::verticalConstraintsForInFlow(geometryForBox(*containingBlock));
};
precomputeVerticalPosition(*ancestor, horizontalConstraintsForAncestor(), verticalConstraintsForAncestor());
}
}
void BlockFormattingContext::precomputeVerticalPositionForFormattingRoot(const FloatingContext& floatingContext, const Box& layoutBox, const ConstraintsPair<HorizontalConstraints>& horizontalConstraints, const ConstraintsPair<VerticalConstraints>& verticalConstraints)
{
ASSERT(layoutBox.establishesFormattingContext());
if (layoutBox.isFloatAvoider() && !layoutBox.hasFloatClear())
return;
// We need the final vertical position when the formatting context inherits floats from the parent FC.
precomputeVerticalPositionForAncestors(layoutBox, horizontalConstraints, verticalConstraints);
precomputeVerticalPosition(layoutBox, horizontalConstraints.containingBlock, verticalConstraints.containingBlock);
if (layoutBox.hasFloatClear()) {
// if we just let the box sit at the static vertical position, we might find unrelated float boxes there (boxes that we need to clear).
computeVerticalPositionForFloatClear(floatingContext, layoutBox);
}
}
void BlockFormattingContext::computePositionToAvoidFloats(const FloatingContext& floatingContext, const Box& layoutBox, const ConstraintsPair<HorizontalConstraints>& horizontalConstraints, const ConstraintsPair<VerticalConstraints>& verticalConstraints)
{
ASSERT(layoutBox.isFloatAvoider());
// In order to position a float avoider we need to know its vertical position relative to its formatting context root (and not just its containing block),
// because all the already-placed floats (floats that we are trying to avoid here) in this BFC might belong
// to a different set of containing blocks (but they all descendants of the BFC root).
// However according to the BFC rules, at this point of the layout flow we don't yet have computed vertical positions for the ancestors.
if (layoutBox.isFloatingPositioned()) {
precomputeVerticalPositionForAncestors(layoutBox, horizontalConstraints, verticalConstraints);
formattingState().displayBox(layoutBox).setTopLeft(floatingContext.positionForFloat(layoutBox));
return;
}
// Non-float positioned float avoiders (formatting context roots and clear boxes) should be fine unless there are floats in this context.
if (floatingContext.isEmpty())
return;
precomputeVerticalPositionForAncestors(layoutBox, horizontalConstraints, verticalConstraints);
if (layoutBox.hasFloatClear())
return computeVerticalPositionForFloatClear(floatingContext, layoutBox);
ASSERT(layoutBox.establishesFormattingContext());
if (auto adjustedPosition = floatingContext.positionForFormattingContextRoot(layoutBox))
formattingState().displayBox(layoutBox).setTopLeft(*adjustedPosition);
}
void BlockFormattingContext::computeVerticalPositionForFloatClear(const FloatingContext& floatingContext, const Box& layoutBox)
{
ASSERT(layoutBox.hasFloatClear());
if (floatingContext.isEmpty())
return;
auto verticalPositionAndClearance = floatingContext.verticalPositionWithClearance(layoutBox);
if (!verticalPositionAndClearance.position) {
ASSERT(!verticalPositionAndClearance.clearance);
return;
}
auto& displayBox = formattingState().displayBox(layoutBox);
ASSERT(*verticalPositionAndClearance.position >= displayBox.top());
displayBox.setTop(*verticalPositionAndClearance.position);
if (verticalPositionAndClearance.clearance)
displayBox.setHasClearance();
}
void BlockFormattingContext::computeWidthAndMargin(const FloatingContext& floatingContext, const Box& layoutBox, const ConstraintsPair<HorizontalConstraints>& horizontalConstraints)
{
auto compute = [&](Optional<LayoutUnit> usedWidth) -> ContentWidthAndMargin {
if (layoutBox.isFloatingPositioned())
return geometry().floatingWidthAndMargin(layoutBox, horizontalConstraints.containingBlock, { usedWidth, { } });
if (layoutBox.isFloatAvoider()) {
auto availableWidth = usedAvailableWidthForFloatAvoider(floatingContext, layoutBox).valueOr(horizontalConstraints.containingBlock.logicalWidth);
return geometry().inFlowWidthAndMargin(layoutBox, { horizontalConstraints.containingBlock.logicalLeft, availableWidth }, { usedWidth, { } });
}
if (layoutBox.isInFlow())
return geometry().inFlowWidthAndMargin(layoutBox, horizontalConstraints.containingBlock, { usedWidth, { } });
ASSERT_NOT_REACHED();
return { };
};
auto contentWidthAndMargin = compute({ });
auto availableWidth = horizontalConstraints.containingBlock.logicalWidth;
if (auto maxWidth = geometry().computedMaxWidth(layoutBox, availableWidth)) {
auto maxWidthAndMargin = compute(maxWidth);
if (contentWidthAndMargin.contentWidth > maxWidthAndMargin.contentWidth)
contentWidthAndMargin = maxWidthAndMargin;
}
auto minWidth = geometry().computedMinWidth(layoutBox, availableWidth).valueOr(0);
auto minWidthAndMargin = compute(minWidth);
if (contentWidthAndMargin.contentWidth < minWidthAndMargin.contentWidth)
contentWidthAndMargin = minWidthAndMargin;
auto& displayBox = formattingState().displayBox(layoutBox);
displayBox.setContentBoxWidth(contentWidthAndMargin.contentWidth);
displayBox.setHorizontalMargin(contentWidthAndMargin.usedMargin);
displayBox.setHorizontalComputedMargin(contentWidthAndMargin.computedMargin);
}
void BlockFormattingContext::computeHeightAndMargin(const Box& layoutBox, const ConstraintsPair<HorizontalConstraints>& horizontalConstraints, const ConstraintsPair<VerticalConstraints>& verticalConstraints)
{
auto compute = [&](Optional<LayoutUnit> usedHeight) -> ContentHeightAndMargin {
if (layoutBox.isInFlow())
return geometry().inFlowHeightAndMargin(layoutBox, horizontalConstraints.containingBlock, { usedHeight });
if (layoutBox.isFloatingPositioned())
return geometry().floatingHeightAndMargin(layoutBox, horizontalConstraints.containingBlock, { usedHeight });
ASSERT_NOT_REACHED();
return { };
};
auto contentHeightAndMargin = compute({ });
if (auto maxHeight = geometry().computedMaxHeight(layoutBox)) {
if (contentHeightAndMargin.contentHeight > *maxHeight) {
auto maxHeightAndMargin = compute(maxHeight);
// Used height should remain the same.
ASSERT((layoutState().inQuirksMode() && (layoutBox.isBodyBox() || layoutBox.isDocumentBox())) || maxHeightAndMargin.contentHeight == *maxHeight);
contentHeightAndMargin = { *maxHeight, maxHeightAndMargin.nonCollapsedMargin };
}
}
if (auto minHeight = geometry().computedMinHeight(layoutBox)) {
if (contentHeightAndMargin.contentHeight < *minHeight) {
auto minHeightAndMargin = compute(minHeight);
// Used height should remain the same.
ASSERT((layoutState().inQuirksMode() && (layoutBox.isBodyBox() || layoutBox.isDocumentBox())) || minHeightAndMargin.contentHeight == *minHeight);
contentHeightAndMargin = { *minHeight, minHeightAndMargin.nonCollapsedMargin };
}
}
// 1. Compute collapsed margins.
// 2. Adjust vertical position using the collapsed values
// 3. Adjust previous in-flow sibling margin after using this margin.
auto collapsedMargin = marginCollapse().collapsedVerticalValues(layoutBox, contentHeightAndMargin.nonCollapsedMargin);
auto verticalMargin = UsedVerticalMargin { contentHeightAndMargin.nonCollapsedMargin, collapsedMargin };
auto& displayBox = formattingState().displayBox(layoutBox);
// Out of flow boxes don't need vertical adjustment after margin collapsing.
if (layoutBox.isOutOfFlowPositioned()) {
ASSERT(!hasPrecomputedMarginBefore(layoutBox));
displayBox.setContentBoxHeight(contentHeightAndMargin.contentHeight);
displayBox.setVerticalMargin(verticalMargin);
return;
}
ASSERT(!hasPrecomputedMarginBefore(layoutBox) || precomputedMarginBefore(layoutBox).usedValue() == verticalMargin.before());
removePrecomputedMarginBefore(layoutBox);
displayBox.setTop(verticalPositionWithMargin(layoutBox, verticalMargin, verticalConstraints.containingBlock));
displayBox.setContentBoxHeight(contentHeightAndMargin.contentHeight);
displayBox.setVerticalMargin(verticalMargin);
auto marginCollapse = this->marginCollapse();
formattingState().setPositiveAndNegativeVerticalMargin(layoutBox, marginCollapse.resolvedPositiveNegativeMarginValues(layoutBox, contentHeightAndMargin.nonCollapsedMargin));
// Adjust the previous sibling's margin bottom now that this box's vertical margin is computed.
MarginCollapse::updateMarginAfterForPreviousSibling(*this, marginCollapse, layoutBox);
}
FormattingContext::IntrinsicWidthConstraints BlockFormattingContext::computedIntrinsicWidthConstraints()
{
auto& formattingState = this->formattingState();
ASSERT(!formattingState.intrinsicWidthConstraints());
// Visit the in-flow descendants and compute their min/max intrinsic width if needed.
// 1. Go all the way down to the leaf node
// 2. Check if actually need to visit all the boxes as we traverse down (already computed, container's min/max does not depend on descendants etc)
// 3. As we climb back on the tree, compute min/max intrinsic width
// (Any subtrees with new formatting contexts need to layout synchronously)
Vector<const Box*> queue;
if (root().hasInFlowOrFloatingChild())
queue.append(root().firstInFlowOrFloatingChild());
IntrinsicWidthConstraints constraints;
while (!queue.isEmpty()) {
while (true) {
auto& layoutBox = *queue.last();
auto hasInFlowOrFloatingChild = is<ContainerBox>(layoutBox) && downcast<ContainerBox>(layoutBox).hasInFlowOrFloatingChild();
auto skipDescendants = formattingState.intrinsicWidthConstraintsForBox(layoutBox) || !hasInFlowOrFloatingChild || layoutBox.establishesFormattingContext() || layoutBox.style().width().isFixed();
if (skipDescendants)
break;
queue.append(downcast<ContainerBox>(layoutBox).firstInFlowOrFloatingChild());
}
// Compute min/max intrinsic width bottom up if needed.
while (!queue.isEmpty()) {
auto& layoutBox = *queue.takeLast();
auto desdendantConstraints = formattingState.intrinsicWidthConstraintsForBox(layoutBox);
if (!desdendantConstraints) {
desdendantConstraints = geometry().intrinsicWidthConstraints(layoutBox);
formattingState.setIntrinsicWidthConstraintsForBox(layoutBox, *desdendantConstraints);
}
constraints.minimum = std::max(constraints.minimum, desdendantConstraints->minimum);
constraints.maximum = std::max(constraints.maximum, desdendantConstraints->maximum);
// Move over to the next sibling or take the next box in the queue.
if (auto* nextSibling = layoutBox.nextInFlowOrFloatingSibling()) {
queue.append(nextSibling);
break;
}
}
}
formattingState.setIntrinsicWidthConstraints(constraints);
return constraints;
}
LayoutUnit BlockFormattingContext::verticalPositionWithMargin(const Box& layoutBox, const UsedVerticalMargin& verticalMargin, const VerticalConstraints& verticalConstraints) const
{
ASSERT(!layoutBox.isOutOfFlowPositioned());
// Now that we've computed the final margin before, let's shift the box's vertical position if needed.
// 1. Check if the box has clearance. If so, we've already precomputed/finalized the top value and vertical margin does not impact it anymore.
// 2. Check if the margin before collapses with the previous box's margin after. if not -> return previous box's bottom including margin after + marginBefore
// 3. Check if the previous box's margins collapse through. If not -> return previous box' bottom excluding margin after + marginBefore (they are supposed to be equal)
// 4. Go to previous box and start from step #1 until we hit the parent box.
auto& boxGeometry = geometryForBox(layoutBox);
if (boxGeometry.hasClearance())
return boxGeometry.top();
auto* currentLayoutBox = &layoutBox;
while (currentLayoutBox) {
if (!currentLayoutBox->previousInFlowSibling())
break;
auto& previousInFlowSibling = *currentLayoutBox->previousInFlowSibling();
if (!marginCollapse().marginBeforeCollapsesWithPreviousSiblingMarginAfter(*currentLayoutBox)) {
auto& previousBoxGeometry = geometryForBox(previousInFlowSibling);
return previousBoxGeometry.rectWithMargin().bottom() + verticalMargin.before();
}
if (!marginCollapse().marginsCollapseThrough(previousInFlowSibling)) {
auto& previousBoxGeometry = geometryForBox(previousInFlowSibling);
return previousBoxGeometry.bottom() + verticalMargin.before();
}
currentLayoutBox = &previousInFlowSibling;
}
auto containingBlockContentBoxTop = verticalConstraints.logicalTop;
// Adjust vertical position depending whether this box directly or indirectly adjoins with its parent.
auto directlyAdjoinsParent = !layoutBox.previousInFlowSibling();
if (directlyAdjoinsParent) {
// If the top and bottom margins of a box are adjoining, then it is possible for margins to collapse through it.
// In this case, the position of the element depends on its relationship with the other elements whose margins are being collapsed.
if (verticalMargin.collapsedValues().isCollapsedThrough) {
// If the element's margins are collapsed with its parent's top margin, the top border edge of the box is defined to be the same as the parent's.
if (marginCollapse().marginBeforeCollapsesWithParentMarginBefore(layoutBox))
return containingBlockContentBoxTop;
// Otherwise, either the element's parent is not taking part in the margin collapsing, or only the parent's bottom margin is involved.
// The position of the element's top border edge is the same as it would have been if the element had a non-zero bottom border.
auto beforeMarginWithBottomBorder = marginCollapse().marginBeforeIgnoringCollapsingThrough(layoutBox, verticalMargin.nonCollapsedValues());
return containingBlockContentBoxTop + beforeMarginWithBottomBorder;
}
// Non-collapsed through box vertical position depending whether the margin collapses.
if (marginCollapse().marginBeforeCollapsesWithParentMarginBefore(layoutBox))
return containingBlockContentBoxTop;
return containingBlockContentBoxTop + verticalMargin.before();
}
// At this point this box indirectly (via collapsed through previous in-flow siblings) adjoins the parent. Let's check if it margin collapses with the parent.
auto& containingBlock = *layoutBox.containingBlock();
ASSERT(containingBlock.firstInFlowChild());
ASSERT(containingBlock.firstInFlowChild() != &layoutBox);
if (marginCollapse().marginBeforeCollapsesWithParentMarginBefore(*containingBlock.firstInFlowChild()))
return containingBlockContentBoxTop;
return containingBlockContentBoxTop + verticalMargin.before();
}
void BlockFormattingContext::setPrecomputedMarginBefore(const Box& layoutBox, const PrecomputedMarginBefore& precomputedMarginBefore)
{
// Can't cross formatting context boundary.
ASSERT(&layoutState().formattingStateForBox(layoutBox) == &formattingState());
m_precomputedMarginBeforeList.set(&layoutBox, precomputedMarginBefore);
}
bool BlockFormattingContext::hasPrecomputedMarginBefore(const Box& layoutBox) const
{
// Can't cross formatting context boundary.
ASSERT(&layoutState().formattingStateForBox(layoutBox) == &formattingState());
return m_precomputedMarginBeforeList.contains(&layoutBox);
}
}
}
#endif