Source/WebCore/layout/FormattingContext.cpp - WebKit - Git at Google

 /*
  * 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
  * THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "FormattingContext.h"

 #if ENABLE(LAYOUT_FORMATTING_CONTEXT)

 #include "DisplayBox.h"
 #include "FormattingState.h"
 #include "InvalidationState.h"
 #include "LayoutBox.h"
 #include "LayoutContainerBox.h"
 #include "LayoutContext.h"
 #include "LayoutDescendantIterator.h"
 #include "LayoutInitialContainingBlock.h"
 #include "LayoutReplacedBox.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(FormattingContext);

 FormattingContext::FormattingContext(const ContainerBox& formattingContextRoot, FormattingState& formattingState)
     : m_root(makeWeakPtr(formattingContextRoot))
     , m_formattingState(formattingState)
 {
     ASSERT(formattingContextRoot.hasChild());
 #ifndef NDEBUG
     layoutState().registerFormattingContext(*this);
 #endif
 }

 FormattingContext::~FormattingContext()
 {
 #ifndef NDEBUG
     layoutState().deregisterFormattingContext(*this);
 #endif
 }

 LayoutState& FormattingContext::layoutState() const
 {
     return m_formattingState.layoutState();
 }

 void FormattingContext::computeOutOfFlowHorizontalGeometry(const Box& layoutBox, const HorizontalConstraints& horizontalConstraints, const VerticalConstraints& verticalConstraints)
 {
     ASSERT(layoutBox.isOutOfFlowPositioned());
     auto compute = [&](Optional<LayoutUnit> usedWidth) {
         return geometry().outOfFlowHorizontalGeometry(layoutBox, horizontalConstraints, verticalConstraints, { usedWidth, { } });
     };

     auto containingBlockWidth = horizontalConstraints.logicalWidth;
     auto horizontalGeometry = compute({ });
     if (auto maxWidth = geometry().computedMaxWidth(layoutBox, containingBlockWidth)) {
         auto maxHorizontalGeometry = compute(maxWidth);
         if (horizontalGeometry.contentWidthAndMargin.contentWidth > maxHorizontalGeometry.contentWidthAndMargin.contentWidth)
             horizontalGeometry = maxHorizontalGeometry;
     }

     if (auto minWidth = geometry().computedMinWidth(layoutBox, containingBlockWidth)) {
         auto minHorizontalGeometry = compute(minWidth);
         if (horizontalGeometry.contentWidthAndMargin.contentWidth < minHorizontalGeometry.contentWidthAndMargin.contentWidth)
             horizontalGeometry = minHorizontalGeometry;
     }

     auto& displayBox = formattingState().displayBox(layoutBox);
     displayBox.setLeft(horizontalGeometry.left + horizontalGeometry.contentWidthAndMargin.usedMargin.start);
     displayBox.setContentBoxWidth(horizontalGeometry.contentWidthAndMargin.contentWidth);
     displayBox.setHorizontalMargin(horizontalGeometry.contentWidthAndMargin.usedMargin);
     displayBox.setHorizontalComputedMargin(horizontalGeometry.contentWidthAndMargin.computedMargin);
 }

 void FormattingContext::computeOutOfFlowVerticalGeometry(const Box& layoutBox, const HorizontalConstraints& horizontalConstraints, const VerticalConstraints& verticalConstraints)
 {
     ASSERT(layoutBox.isOutOfFlowPositioned());
     auto compute = [&](Optional<LayoutUnit> usedHeight) {
         return geometry().outOfFlowVerticalGeometry(layoutBox, horizontalConstraints, verticalConstraints, { usedHeight });
     };

     auto containingBlockHeight = *verticalConstraints.logicalHeight;
     auto verticalGeometry = compute({ });
     if (auto maxHeight = geometry().computedMaxHeight(layoutBox, containingBlockHeight)) {
         auto maxVerticalGeometry = compute(maxHeight);
         if (verticalGeometry.contentHeightAndMargin.contentHeight > maxVerticalGeometry.contentHeightAndMargin.contentHeight)
             verticalGeometry = maxVerticalGeometry;
     }

     if (auto minHeight = geometry().computedMinHeight(layoutBox, containingBlockHeight)) {
         auto minVerticalGeometry = compute(minHeight);
         if (verticalGeometry.contentHeightAndMargin.contentHeight < minVerticalGeometry.contentHeightAndMargin.contentHeight)
             verticalGeometry = minVerticalGeometry;
     }

     auto& displayBox = formattingState().displayBox(layoutBox);
     auto nonCollapsedVerticalMargin = verticalGeometry.contentHeightAndMargin.nonCollapsedMargin;
     displayBox.setTop(verticalGeometry.top + nonCollapsedVerticalMargin.before);
     displayBox.setContentBoxHeight(verticalGeometry.contentHeightAndMargin.contentHeight);
     // Margins of absolutely positioned boxes do not collapse
     displayBox.setVerticalMargin({ nonCollapsedVerticalMargin, { } });
 }

 void FormattingContext::computeBorderAndPadding(const Box& layoutBox, const HorizontalConstraints& horizontalConstraint)
 {
     auto& displayBox = formattingState().displayBox(layoutBox);
     displayBox.setBorder(geometry().computedBorder(layoutBox));
     displayBox.setPadding(geometry().computedPadding(layoutBox, horizontalConstraint));
 }

 void FormattingContext::layoutOutOfFlowContent(InvalidationState& invalidationState, const OutOfFlowHorizontalConstraints& rootHorizontalConstraints, const VerticalConstraints& rootVerticalConstraints)
 {
     LOG_WITH_STREAM(FormattingContextLayout, stream << "Start: layout out-of-flow content -> context: " << &layoutState() << " root: " << &root());

     collectOutOfFlowDescendantsIfNeeded();

     auto horizontalConstraintsForLayoutBox = [&] (const auto& outOfFlowBox) {
         auto& containingBlock = outOfFlowBox.containingBlock();
         if (&containingBlock == &root())
             return rootHorizontalConstraints;
         return Geometry::horizontalConstraintsForOutOfFlow(geometryForBox(containingBlock));
     };

     auto verticalConstraintsForLayoutBox = [&] (const auto& outOfFlowBox) {
         auto& containingBlock = outOfFlowBox.containingBlock();
         if (&containingBlock == &root())
             return rootVerticalConstraints;
         return Geometry::verticalConstraintsForOutOfFlow(geometryForBox(containingBlock));
     };

     for (auto& outOfFlowBox : formattingState().outOfFlowBoxes()) {
         ASSERT(outOfFlowBox->establishesFormattingContext());
         if (!invalidationState.needsLayout(*outOfFlowBox))
             continue;

         auto outOfFlowHorizontalConstraints = horizontalConstraintsForLayoutBox(*outOfFlowBox);
         auto horizontalConstraintsForBorderAndPadding = HorizontalConstraints { outOfFlowHorizontalConstraints.value.logicalLeft, outOfFlowHorizontalConstraints.borderAndPaddingSpecificWidth };
         computeBorderAndPadding(*outOfFlowBox, horizontalConstraintsForBorderAndPadding);

         auto horizontalConstraints = outOfFlowHorizontalConstraints.value;
         auto verticalConstraints = verticalConstraintsForLayoutBox(*outOfFlowBox);
         computeOutOfFlowHorizontalGeometry(*outOfFlowBox, horizontalConstraints, verticalConstraints);
         if (is<ContainerBox>(*outOfFlowBox)) {
             auto& containerBox = downcast<ContainerBox>(*outOfFlowBox);
             auto& containerDisplayBox = geometryForBox(containerBox);

             if (containerBox.hasInFlowOrFloatingChild()) {
                 auto horizontalConstraintsForInFlowContent = Geometry::horizontalConstraintsForInFlow(containerDisplayBox);
                 auto verticalConstraintsForInFlowContent = Geometry::verticalConstraintsForInFlow(containerDisplayBox);
                 auto formattingContext = LayoutContext::createFormattingContext(containerBox, layoutState());
                 formattingContext->layoutInFlowContent(invalidationState, horizontalConstraintsForInFlowContent, verticalConstraintsForInFlowContent);
             }
             computeOutOfFlowVerticalGeometry(containerBox, horizontalConstraints, verticalConstraints);
             if (containerBox.hasChild()) {
                 auto horizontalConstraintsForOutOfFlowContent =  Geometry::horizontalConstraintsForOutOfFlow(containerDisplayBox);
                 auto verticalConstraintsForOutOfFlowContent = Geometry::verticalConstraintsForOutOfFlow(containerDisplayBox);
                 auto formattingContext = LayoutContext::createFormattingContext(containerBox, layoutState());
                 formattingContext->layoutOutOfFlowContent(invalidationState, horizontalConstraintsForOutOfFlowContent, verticalConstraintsForOutOfFlowContent);
             }
         } else
             computeOutOfFlowVerticalGeometry(*outOfFlowBox, horizontalConstraints, verticalConstraints);
     }
     LOG_WITH_STREAM(FormattingContextLayout, stream << "End: layout out-of-flow content -> context: " << &layoutState() << " root: " << &root());
 }

 const Display::Box& FormattingContext::geometryForBox(const Box& layoutBox, Optional<EscapeReason> escapeReason) const
 {
     UNUSED_PARAM(escapeReason);
 #if ASSERT_ENABLED
     auto isOkToAccessDisplayBox = [&] {
         if (!is<InitialContainingBlock>(layoutBox) && &layoutBox.formattingContextRoot() == &root()) {
             // This is the non-escape case of accessing a box's geometry information within the same formatting context.
             return true;
         }

         if (!escapeReason) {
             // Any geometry access outside of the formatting context without a valid reason is considered an escape.
             return false;
         }

         if (*escapeReason == EscapeReason::DocumentBoxStrechesToViewportQuirk) {
             ASSERT(layoutState().inQuirksMode());
             return is<InitialContainingBlock>(layoutBox);
         }

         if (*escapeReason == EscapeReason::BodyStrechesToViewportQuirk) {
             ASSERT(layoutState().inQuirksMode());
             return is<InitialContainingBlock>(layoutBox) || layoutBox.isDocumentBox();

         }

         if (*escapeReason == EscapeReason::StrokeOverflowNeedsViewportGeometry)
             return is<InitialContainingBlock>(layoutBox);

         if (*escapeReason == EscapeReason::NeedsGeometryFromEstablishedFormattingContext) {
             // This is the case when a formatting root collects geometry information from the established
             // formatting context to be able to determine width/height.
             // e.g <div>text content</div>. The <div> is a formatting root of the IFC.
             // In order to compute the height of the <div>, we need to look inside the IFC and gather geometry information.
             return &layoutBox.formattingContextRoot().formattingContextRoot() == &root();
         }

         if (*escapeReason == EscapeReason::OutOfFlowBoxNeedsInFlowGeometry) {
             // When computing the static position of an out-of-flow box, we need to gather sibling/parent geometry information
             // as if the out-of-flow box was a simple inflow box.
             // Now since the out-of-flow and the sibling/parent boxes could very well be in different containing block subtrees
             // the formatting context they live in could also be very different.
             return true;
         }

         if (*escapeReason == EscapeReason::FloatBoxNeedsToBeInAbsoluteCoordinates) {
             // Float box top/left values are mapped relative to the FloatState's root. Inline formatting contexts(A) inherit floats from parent
             // block formatting contexts(B). Floats in these inline formatting contexts(A) need to be mapped to the parent, block formatting context(B).
             auto& formattingContextRoot = layoutBox.formattingContextRoot();
             return &formattingContextRoot == &root() || &formattingContextRoot == &root().formattingContextRoot();
         }

         if (*escapeReason == EscapeReason::FindFixedHeightAncestorQuirk) {
             ASSERT(layoutState().inQuirksMode());
             // Find the first containing block with fixed height quirk. See Quirks::heightValueOfNearestContainingBlockWithFixedHeight.
             // This is only to check if the targetFormattingRoot is an ancestor formatting root.
             if (is<InitialContainingBlock>(layoutBox))
                 return true;
             auto& targetFormattingRoot = layoutBox.formattingContextRoot();
             auto* ancestorFormattingContextRoot = &root().formattingContextRoot();
             while (true) {
                 if (&targetFormattingRoot == ancestorFormattingContextRoot)
                     return true;
                 ancestorFormattingContextRoot = &ancestorFormattingContextRoot->formattingContextRoot();
                 if (is<InitialContainingBlock>(*ancestorFormattingContextRoot))
                     return true;
             }
             return false;
         }

         if (*escapeReason == EscapeReason::TableNeedsAccessToTableWrapper) {
             // Tables are wrapped in a 2 level formatting context structure. A <table> element initiates a block formatting context for its principal table box
             // where the caption and the table content live. It also initiates a table wrapper box which establishes the table formatting context.
             // In many cases the TFC needs access to the parent (generated) BFC.
             return &layoutBox == &root().formattingContextRoot();
         }

         ASSERT_NOT_REACHED();
         return false;
     };
 #endif
     ASSERT(isOkToAccessDisplayBox());
     ASSERT(layoutState().hasDisplayBox(layoutBox));
     return layoutState().displayBoxForLayoutBox(layoutBox);
 }

 void FormattingContext::collectOutOfFlowDescendantsIfNeeded()
 {
     if (!formattingState().outOfFlowBoxes().isEmpty())
         return;
     auto& root = this->root();
     if (!root.hasChild())
         return;
     if (!root.isPositioned() && !is<InitialContainingBlock>(root))
         return;
     // Collect the out-of-flow descendants at the formatting root level (as opposed to at the containing block level, though they might be the same).
     // FIXME: Turn this into a register-self as boxes are being inserted.
     for (auto& descendant : descendantsOfType<Box>(root)) {
         if (!descendant.isOutOfFlowPositioned())
             continue;
         if (&descendant.formattingContextRoot() != &root)
             continue;
         formattingState().addOutOfFlowBox(descendant);
     }
 }

 #ifndef NDEBUG
 void FormattingContext::validateGeometryConstraintsAfterLayout() const
 {
     auto& formattingContextRoot = root();
     // FIXME: add a descendantsOfType<> flavor that stops at nested formatting contexts
     for (auto& layoutBox : descendantsOfType<Box>(formattingContextRoot)) {
         if (&layoutBox.formattingContextRoot() != &formattingContextRoot)
             continue;
         auto& containingBlockGeometry = geometryForBox(layoutBox.containingBlock());
         auto& boxGeometry = geometryForBox(layoutBox);

         // 10.3.3 Block-level, non-replaced elements in normal flow
         // 10.3.7 Absolutely positioned, non-replaced elements
         if ((layoutBox.isBlockLevelBox() || layoutBox.isOutOfFlowPositioned()) && !layoutBox.isReplacedBox()) {
             // margin-left + border-left-width + padding-left + width + padding-right + border-right-width + margin-right = width of containing block
             auto containingBlockWidth = containingBlockGeometry.contentBoxWidth();
             ASSERT(boxGeometry.horizontalMarginBorderAndPadding() + boxGeometry.contentBoxWidth() == containingBlockWidth);
         }

         // 10.6.4 Absolutely positioned, non-replaced elements
         if (layoutBox.isOutOfFlowPositioned() && !layoutBox.isReplacedBox()) {
             // top + margin-top + border-top-width + padding-top + height + padding-bottom + border-bottom-width + margin-bottom + bottom = height of containing block
             auto containingBlockHeight = containingBlockGeometry.contentBoxHeight();
             ASSERT(boxGeometry.top() + boxGeometry.marginBefore() + boxGeometry.borderTop() + boxGeometry.paddingTop().valueOr(0) + boxGeometry.contentBoxHeight()
                 + boxGeometry.paddingBottom().valueOr(0) + boxGeometry.borderBottom() + boxGeometry.marginAfter() == containingBlockHeight);
         }
     }
 }
 #endif

 }
 }
 #endif
	/*
	* 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
	* THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "FormattingContext.h"

	#if ENABLE(LAYOUT_FORMATTING_CONTEXT)

	#include "DisplayBox.h"
	#include "FormattingState.h"
	#include "InvalidationState.h"
	#include "LayoutBox.h"
	#include "LayoutContainerBox.h"
	#include "LayoutContext.h"
	#include "LayoutDescendantIterator.h"
	#include "LayoutInitialContainingBlock.h"
	#include "LayoutReplacedBox.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(FormattingContext);

	FormattingContext::FormattingContext(const ContainerBox& formattingContextRoot, FormattingState& formattingState)
	: m_root(makeWeakPtr(formattingContextRoot))
	, m_formattingState(formattingState)
	{
	ASSERT(formattingContextRoot.hasChild());
	#ifndef NDEBUG
	layoutState().registerFormattingContext(*this);
	#endif
	}

	FormattingContext::~FormattingContext()
	{
	#ifndef NDEBUG
	layoutState().deregisterFormattingContext(*this);
	#endif
	}

	LayoutState& FormattingContext::layoutState() const
	{
	return m_formattingState.layoutState();
	}

	void FormattingContext::computeOutOfFlowHorizontalGeometry(const Box& layoutBox, const HorizontalConstraints& horizontalConstraints, const VerticalConstraints& verticalConstraints)
	{
	ASSERT(layoutBox.isOutOfFlowPositioned());
	auto compute = [&](Optional<LayoutUnit> usedWidth) {
	return geometry().outOfFlowHorizontalGeometry(layoutBox, horizontalConstraints, verticalConstraints, { usedWidth, { } });
	};

	auto containingBlockWidth = horizontalConstraints.logicalWidth;
	auto horizontalGeometry = compute({ });
	if (auto maxWidth = geometry().computedMaxWidth(layoutBox, containingBlockWidth)) {
	auto maxHorizontalGeometry = compute(maxWidth);
	if (horizontalGeometry.contentWidthAndMargin.contentWidth > maxHorizontalGeometry.contentWidthAndMargin.contentWidth)
	horizontalGeometry = maxHorizontalGeometry;
	}

	if (auto minWidth = geometry().computedMinWidth(layoutBox, containingBlockWidth)) {
	auto minHorizontalGeometry = compute(minWidth);
	if (horizontalGeometry.contentWidthAndMargin.contentWidth < minHorizontalGeometry.contentWidthAndMargin.contentWidth)
	horizontalGeometry = minHorizontalGeometry;
	}

	auto& displayBox = formattingState().displayBox(layoutBox);
	displayBox.setLeft(horizontalGeometry.left + horizontalGeometry.contentWidthAndMargin.usedMargin.start);
	displayBox.setContentBoxWidth(horizontalGeometry.contentWidthAndMargin.contentWidth);
	displayBox.setHorizontalMargin(horizontalGeometry.contentWidthAndMargin.usedMargin);
	displayBox.setHorizontalComputedMargin(horizontalGeometry.contentWidthAndMargin.computedMargin);
	}

	void FormattingContext::computeOutOfFlowVerticalGeometry(const Box& layoutBox, const HorizontalConstraints& horizontalConstraints, const VerticalConstraints& verticalConstraints)
	{
	ASSERT(layoutBox.isOutOfFlowPositioned());
	auto compute = [&](Optional<LayoutUnit> usedHeight) {
	return geometry().outOfFlowVerticalGeometry(layoutBox, horizontalConstraints, verticalConstraints, { usedHeight });
	};

	auto containingBlockHeight = *verticalConstraints.logicalHeight;
	auto verticalGeometry = compute({ });
	if (auto maxHeight = geometry().computedMaxHeight(layoutBox, containingBlockHeight)) {
	auto maxVerticalGeometry = compute(maxHeight);
	if (verticalGeometry.contentHeightAndMargin.contentHeight > maxVerticalGeometry.contentHeightAndMargin.contentHeight)
	verticalGeometry = maxVerticalGeometry;
	}

	if (auto minHeight = geometry().computedMinHeight(layoutBox, containingBlockHeight)) {
	auto minVerticalGeometry = compute(minHeight);
	if (verticalGeometry.contentHeightAndMargin.contentHeight < minVerticalGeometry.contentHeightAndMargin.contentHeight)
	verticalGeometry = minVerticalGeometry;
	}

	auto& displayBox = formattingState().displayBox(layoutBox);
	auto nonCollapsedVerticalMargin = verticalGeometry.contentHeightAndMargin.nonCollapsedMargin;
	displayBox.setTop(verticalGeometry.top + nonCollapsedVerticalMargin.before);
	displayBox.setContentBoxHeight(verticalGeometry.contentHeightAndMargin.contentHeight);
	// Margins of absolutely positioned boxes do not collapse
	displayBox.setVerticalMargin({ nonCollapsedVerticalMargin, { } });
	}

	void FormattingContext::computeBorderAndPadding(const Box& layoutBox, const HorizontalConstraints& horizontalConstraint)
	{
	auto& displayBox = formattingState().displayBox(layoutBox);
	displayBox.setBorder(geometry().computedBorder(layoutBox));
	displayBox.setPadding(geometry().computedPadding(layoutBox, horizontalConstraint));
	}

	void FormattingContext::layoutOutOfFlowContent(InvalidationState& invalidationState, const OutOfFlowHorizontalConstraints& rootHorizontalConstraints, const VerticalConstraints& rootVerticalConstraints)
	{
	LOG_WITH_STREAM(FormattingContextLayout, stream << "Start: layout out-of-flow content -> context: " << &layoutState() << " root: " << &root());

	collectOutOfFlowDescendantsIfNeeded();

	auto horizontalConstraintsForLayoutBox = [&] (const auto& outOfFlowBox) {
	auto& containingBlock = outOfFlowBox.containingBlock();
	if (&containingBlock == &root())
	return rootHorizontalConstraints;
	return Geometry::horizontalConstraintsForOutOfFlow(geometryForBox(containingBlock));
	};

	auto verticalConstraintsForLayoutBox = [&] (const auto& outOfFlowBox) {
	auto& containingBlock = outOfFlowBox.containingBlock();
	if (&containingBlock == &root())
	return rootVerticalConstraints;
	return Geometry::verticalConstraintsForOutOfFlow(geometryForBox(containingBlock));
	};

	for (auto& outOfFlowBox : formattingState().outOfFlowBoxes()) {
	ASSERT(outOfFlowBox->establishesFormattingContext());
	if (!invalidationState.needsLayout(*outOfFlowBox))
	continue;

	auto outOfFlowHorizontalConstraints = horizontalConstraintsForLayoutBox(*outOfFlowBox);
	auto horizontalConstraintsForBorderAndPadding = HorizontalConstraints { outOfFlowHorizontalConstraints.value.logicalLeft, outOfFlowHorizontalConstraints.borderAndPaddingSpecificWidth };
	computeBorderAndPadding(*outOfFlowBox, horizontalConstraintsForBorderAndPadding);

	auto horizontalConstraints = outOfFlowHorizontalConstraints.value;
	auto verticalConstraints = verticalConstraintsForLayoutBox(*outOfFlowBox);
	computeOutOfFlowHorizontalGeometry(*outOfFlowBox, horizontalConstraints, verticalConstraints);
	if (is<ContainerBox>(*outOfFlowBox)) {
	auto& containerBox = downcast<ContainerBox>(*outOfFlowBox);
	auto& containerDisplayBox = geometryForBox(containerBox);

	if (containerBox.hasInFlowOrFloatingChild()) {
	auto horizontalConstraintsForInFlowContent = Geometry::horizontalConstraintsForInFlow(containerDisplayBox);
	auto verticalConstraintsForInFlowContent = Geometry::verticalConstraintsForInFlow(containerDisplayBox);
	auto formattingContext = LayoutContext::createFormattingContext(containerBox, layoutState());
	formattingContext->layoutInFlowContent(invalidationState, horizontalConstraintsForInFlowContent, verticalConstraintsForInFlowContent);
	}
	computeOutOfFlowVerticalGeometry(containerBox, horizontalConstraints, verticalConstraints);
	if (containerBox.hasChild()) {
	auto horizontalConstraintsForOutOfFlowContent = Geometry::horizontalConstraintsForOutOfFlow(containerDisplayBox);
	auto verticalConstraintsForOutOfFlowContent = Geometry::verticalConstraintsForOutOfFlow(containerDisplayBox);
	auto formattingContext = LayoutContext::createFormattingContext(containerBox, layoutState());
	formattingContext->layoutOutOfFlowContent(invalidationState, horizontalConstraintsForOutOfFlowContent, verticalConstraintsForOutOfFlowContent);
	}
	} else
	computeOutOfFlowVerticalGeometry(*outOfFlowBox, horizontalConstraints, verticalConstraints);
	}
	LOG_WITH_STREAM(FormattingContextLayout, stream << "End: layout out-of-flow content -> context: " << &layoutState() << " root: " << &root());
	}

	const Display::Box& FormattingContext::geometryForBox(const Box& layoutBox, Optional<EscapeReason> escapeReason) const
	{
	UNUSED_PARAM(escapeReason);
	#if ASSERT_ENABLED
	auto isOkToAccessDisplayBox = [&] {
	if (!is<InitialContainingBlock>(layoutBox) && &layoutBox.formattingContextRoot() == &root()) {
	// This is the non-escape case of accessing a box's geometry information within the same formatting context.
	return true;
	}

	if (!escapeReason) {
	// Any geometry access outside of the formatting context without a valid reason is considered an escape.
	return false;
	}

	if (*escapeReason == EscapeReason::DocumentBoxStrechesToViewportQuirk) {
	ASSERT(layoutState().inQuirksMode());
	return is<InitialContainingBlock>(layoutBox);
	}

	if (*escapeReason == EscapeReason::BodyStrechesToViewportQuirk) {
	ASSERT(layoutState().inQuirksMode());
	return is<InitialContainingBlock>(layoutBox) \|\| layoutBox.isDocumentBox();

	}

	if (*escapeReason == EscapeReason::StrokeOverflowNeedsViewportGeometry)
	return is<InitialContainingBlock>(layoutBox);

	if (*escapeReason == EscapeReason::NeedsGeometryFromEstablishedFormattingContext) {
	// This is the case when a formatting root collects geometry information from the established
	// formatting context to be able to determine width/height.
	// e.g <div>text content</div>. The <div> is a formatting root of the IFC.
	// In order to compute the height of the <div>, we need to look inside the IFC and gather geometry information.
	return &layoutBox.formattingContextRoot().formattingContextRoot() == &root();
	}

	if (*escapeReason == EscapeReason::OutOfFlowBoxNeedsInFlowGeometry) {
	// When computing the static position of an out-of-flow box, we need to gather sibling/parent geometry information
	// as if the out-of-flow box was a simple inflow box.
	// Now since the out-of-flow and the sibling/parent boxes could very well be in different containing block subtrees
	// the formatting context they live in could also be very different.
	return true;
	}

	if (*escapeReason == EscapeReason::FloatBoxNeedsToBeInAbsoluteCoordinates) {
	// Float box top/left values are mapped relative to the FloatState's root. Inline formatting contexts(A) inherit floats from parent
	// block formatting contexts(B). Floats in these inline formatting contexts(A) need to be mapped to the parent, block formatting context(B).
	auto& formattingContextRoot = layoutBox.formattingContextRoot();
	return &formattingContextRoot == &root() \|\| &formattingContextRoot == &root().formattingContextRoot();
	}

	if (*escapeReason == EscapeReason::FindFixedHeightAncestorQuirk) {
	ASSERT(layoutState().inQuirksMode());
	// Find the first containing block with fixed height quirk. See Quirks::heightValueOfNearestContainingBlockWithFixedHeight.
	// This is only to check if the targetFormattingRoot is an ancestor formatting root.
	if (is<InitialContainingBlock>(layoutBox))
	return true;
	auto& targetFormattingRoot = layoutBox.formattingContextRoot();
	auto* ancestorFormattingContextRoot = &root().formattingContextRoot();
	while (true) {
	if (&targetFormattingRoot == ancestorFormattingContextRoot)
	return true;
	ancestorFormattingContextRoot = &ancestorFormattingContextRoot->formattingContextRoot();
	if (is<InitialContainingBlock>(*ancestorFormattingContextRoot))
	return true;
	}
	return false;
	}

	if (*escapeReason == EscapeReason::TableNeedsAccessToTableWrapper) {
	// Tables are wrapped in a 2 level formatting context structure. A <table> element initiates a block formatting context for its principal table box
	// where the caption and the table content live. It also initiates a table wrapper box which establishes the table formatting context.
	// In many cases the TFC needs access to the parent (generated) BFC.
	return &layoutBox == &root().formattingContextRoot();
	}

	ASSERT_NOT_REACHED();
	return false;
	};
	#endif
	ASSERT(isOkToAccessDisplayBox());
	ASSERT(layoutState().hasDisplayBox(layoutBox));
	return layoutState().displayBoxForLayoutBox(layoutBox);
	}

	void FormattingContext::collectOutOfFlowDescendantsIfNeeded()
	{
	if (!formattingState().outOfFlowBoxes().isEmpty())
	return;
	auto& root = this->root();
	if (!root.hasChild())
	return;
	if (!root.isPositioned() && !is<InitialContainingBlock>(root))
	return;
	// Collect the out-of-flow descendants at the formatting root level (as opposed to at the containing block level, though they might be the same).
	// FIXME: Turn this into a register-self as boxes are being inserted.
	for (auto& descendant : descendantsOfType<Box>(root)) {
	if (!descendant.isOutOfFlowPositioned())
	continue;
	if (&descendant.formattingContextRoot() != &root)
	continue;
	formattingState().addOutOfFlowBox(descendant);
	}
	}

	#ifndef NDEBUG
	void FormattingContext::validateGeometryConstraintsAfterLayout() const
	{
	auto& formattingContextRoot = root();
	// FIXME: add a descendantsOfType<> flavor that stops at nested formatting contexts
	for (auto& layoutBox : descendantsOfType<Box>(formattingContextRoot)) {
	if (&layoutBox.formattingContextRoot() != &formattingContextRoot)
	continue;
	auto& containingBlockGeometry = geometryForBox(layoutBox.containingBlock());
	auto& boxGeometry = geometryForBox(layoutBox);

	// 10.3.3 Block-level, non-replaced elements in normal flow
	// 10.3.7 Absolutely positioned, non-replaced elements
	if ((layoutBox.isBlockLevelBox() \|\| layoutBox.isOutOfFlowPositioned()) && !layoutBox.isReplacedBox()) {
	// margin-left + border-left-width + padding-left + width + padding-right + border-right-width + margin-right = width of containing block
	auto containingBlockWidth = containingBlockGeometry.contentBoxWidth();
	ASSERT(boxGeometry.horizontalMarginBorderAndPadding() + boxGeometry.contentBoxWidth() == containingBlockWidth);
	}

	// 10.6.4 Absolutely positioned, non-replaced elements
	if (layoutBox.isOutOfFlowPositioned() && !layoutBox.isReplacedBox()) {
	// top + margin-top + border-top-width + padding-top + height + padding-bottom + border-bottom-width + margin-bottom + bottom = height of containing block
	auto containingBlockHeight = containingBlockGeometry.contentBoxHeight();
	ASSERT(boxGeometry.top() + boxGeometry.marginBefore() + boxGeometry.borderTop() + boxGeometry.paddingTop().valueOr(0) + boxGeometry.contentBoxHeight()
	+ boxGeometry.paddingBottom().valueOr(0) + boxGeometry.borderBottom() + boxGeometry.marginAfter() == containingBlockHeight);
	}
	}
	}
	#endif

	}
	}
	#endif