/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
 *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
 * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
 *               All rights reserved.
 * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#include "core/layout/LayoutBox.h"

#include "core/dom/Document.h"
#include "core/editing/EditingUtilities.h"
#include "core/frame/FrameView.h"
#include "core/frame/LocalFrame.h"
#include "core/frame/Settings.h"
#include "core/html/HTMLElement.h"
#include "core/html/HTMLFrameElementBase.h"
#include "core/html/HTMLFrameOwnerElement.h"
#include "core/input/EventHandler.h"
#include "core/layout/HitTestResult.h"
#include "core/layout/LayoutAnalyzer.h"
#include "core/layout/LayoutDeprecatedFlexibleBox.h"
#include "core/layout/LayoutFlexibleBox.h"
#include "core/layout/LayoutGrid.h"
#include "core/layout/LayoutInline.h"
#include "core/layout/LayoutListMarker.h"
#include "core/layout/LayoutMultiColumnFlowThread.h"
#include "core/layout/LayoutMultiColumnSpannerPlaceholder.h"
#include "core/layout/LayoutPart.h"
#include "core/layout/LayoutTableCell.h"
#include "core/layout/LayoutView.h"
#include "core/layout/api/LayoutAPIShim.h"
#include "core/layout/api/LayoutPartItem.h"
#include "core/layout/api/LineLayoutBlockFlow.h"
#include "core/layout/api/LineLayoutBox.h"
#include "core/layout/compositing/PaintLayerCompositor.h"
#include "core/layout/shapes/ShapeOutsideInfo.h"
#include "core/page/AutoscrollController.h"
#include "core/page/Page.h"
#include "core/page/scrolling/SnapCoordinator.h"
#include "core/paint/BackgroundImageGeometry.h"
#include "core/paint/BoxPaintInvalidator.h"
#include "core/paint/BoxPainter.h"
#include "core/paint/PaintLayer.h"
#include "core/style/ShadowList.h"
#include "platform/LengthFunctions.h"
#include "platform/geometry/DoubleRect.h"
#include "platform/geometry/FloatQuad.h"
#include "platform/geometry/FloatRoundedRect.h"
#include "wtf/PtrUtil.h"
#include <algorithm>
#include <math.h>

namespace blink {

// Used by flexible boxes when flexing this element and by table cells.
typedef WTF::HashMap<const LayoutBox*, LayoutUnit> OverrideSizeMap;

static OverrideSizeMap* gExtraInlineOffsetMap = nullptr;
static OverrideSizeMap* gExtraBlockOffsetMap = nullptr;

// Size of border belt for autoscroll. When mouse pointer in border belt,
// autoscroll is started.
static const int autoscrollBeltSize = 20;
static const unsigned backgroundObscurationTestMaxDepth = 4;

struct SameSizeAsLayoutBox : public LayoutBoxModelObject {
  LayoutRect frameRect;
  LayoutUnit intrinsicContentLogicalHeight;
  LayoutRectOutsets marginBoxOutsets;
  LayoutUnit preferredLogicalWidth[2];
  void* pointers[3];
};

static_assert(sizeof(LayoutBox) == sizeof(SameSizeAsLayoutBox),
              "LayoutBox should stay small");

LayoutBox::LayoutBox(ContainerNode* node)
    : LayoutBoxModelObject(node),
      m_intrinsicContentLogicalHeight(-1),
      m_minPreferredLogicalWidth(-1),
      m_maxPreferredLogicalWidth(-1),
      m_inlineBoxWrapper(nullptr) {
  setIsBox();
}

PaintLayerType LayoutBox::layerTypeRequired() const {
  // hasAutoZIndex only returns true if the element is positioned or a flex-item
  // since position:static elements that are not flex-items get their z-index
  // coerced to auto.
  if (isPositioned() || createsGroup() || hasClipPath() ||
      hasTransformRelatedProperty() || style()->hasCompositorProxy() ||
      hasHiddenBackface() || hasReflection() || style()->specifiesColumns() ||
      style()->isStackingContext() ||
      style()->shouldCompositeForCurrentAnimations())
    return NormalPaintLayer;

  if (hasOverflowClip())
    return OverflowClipPaintLayer;

  return NoPaintLayer;
}

void LayoutBox::willBeDestroyed() {
  clearOverrideSize();
  clearContainingBlockOverrideSize();
  clearExtraInlineAndBlockOffests();

  if (isOutOfFlowPositioned())
    LayoutBlock::removePositionedObject(this);
  removeFromPercentHeightContainer();
  if (isOrthogonalWritingModeRoot() && !documentBeingDestroyed())
    unmarkOrthogonalWritingModeRoot();

  ShapeOutsideInfo::removeInfo(*this);

  BoxPaintInvalidator::boxWillBeDestroyed(*this);

  LayoutBoxModelObject::willBeDestroyed();
}

void LayoutBox::insertedIntoTree() {
  LayoutBoxModelObject::insertedIntoTree();
  addScrollSnapMapping();

  if (isOrthogonalWritingModeRoot())
    markOrthogonalWritingModeRoot();
}

void LayoutBox::willBeRemovedFromTree() {
  if (!documentBeingDestroyed() && isOrthogonalWritingModeRoot())
    unmarkOrthogonalWritingModeRoot();

  clearScrollSnapMapping();
  LayoutBoxModelObject::willBeRemovedFromTree();
}

void LayoutBox::removeFloatingOrPositionedChildFromBlockLists() {
  ASSERT(isFloatingOrOutOfFlowPositioned());

  if (documentBeingDestroyed())
    return;

  if (isFloating()) {
    LayoutBlockFlow* parentBlockFlow = nullptr;
    for (LayoutObject* curr = parent(); curr; curr = curr->parent()) {
      if (curr->isLayoutBlockFlow()) {
        LayoutBlockFlow* currBlockFlow = toLayoutBlockFlow(curr);
        if (!parentBlockFlow || currBlockFlow->containsFloat(this))
          parentBlockFlow = currBlockFlow;
      }
    }

    if (parentBlockFlow) {
      parentBlockFlow->markSiblingsWithFloatsForLayout(this);
      parentBlockFlow->markAllDescendantsWithFloatsForLayout(this, false);
    }
  }

  if (isOutOfFlowPositioned())
    LayoutBlock::removePositionedObject(this);
}

void LayoutBox::styleWillChange(StyleDifference diff,
                                const ComputedStyle& newStyle) {
  const ComputedStyle* oldStyle = style();
  if (oldStyle) {
    LayoutFlowThread* flowThread = flowThreadContainingBlock();
    if (flowThread && flowThread != this)
      flowThread->flowThreadDescendantStyleWillChange(this, diff, newStyle);

    // The background of the root element or the body element could propagate up
    // to the canvas. Just dirty the entire canvas when our style changes
    // substantially.
    if ((diff.needsPaintInvalidation() || diff.needsLayout()) && node() &&
        (isHTMLHtmlElement(*node()) || isHTMLBodyElement(*node()))) {
      view()->setShouldDoFullPaintInvalidation();

      if (oldStyle->hasEntirelyFixedBackground() !=
          newStyle.hasEntirelyFixedBackground())
        view()->compositor()->setNeedsUpdateFixedBackground();
    }

    // When a layout hint happens and an object's position style changes, we
    // have to do a layout to dirty the layout tree using the old position
    // value now.
    if (diff.needsFullLayout() && parent() &&
        oldStyle->position() != newStyle.position()) {
      if (!oldStyle->hasOutOfFlowPosition() &&
          newStyle.hasOutOfFlowPosition()) {
        // We're about to go out of flow. Before that takes place, we need to
        // mark the current containing block chain for preferred widths
        // recalculation.
        setNeedsLayoutAndPrefWidthsRecalc(
            LayoutInvalidationReason::StyleChange);
      } else {
        markContainerChainForLayout();
      }
      if (oldStyle->position() == StaticPosition)
        setShouldDoFullPaintInvalidation();
      else if (newStyle.hasOutOfFlowPosition())
        parent()->setChildNeedsLayout();
      if (isFloating() && !isOutOfFlowPositioned() &&
          newStyle.hasOutOfFlowPosition())
        removeFloatingOrPositionedChildFromBlockLists();
    }
    // FIXME: This branch runs when !oldStyle, which means that layout was never
    // called so what's the point in invalidating the whole view that we never
    // painted?
  } else if (isBody()) {
    view()->setShouldDoFullPaintInvalidation();
  }

  LayoutBoxModelObject::styleWillChange(diff, newStyle);
}

void LayoutBox::styleDidChange(StyleDifference diff,
                               const ComputedStyle* oldStyle) {
  // Horizontal writing mode definition is updated in LayoutBoxModelObject::
  // updateFromStyle, (as part of the LayoutBoxModelObject::styleDidChange call
  // below). So, we can safely cache the horizontal writing mode value before
  // style change here.
  bool oldHorizontalWritingMode = isHorizontalWritingMode();

  LayoutBoxModelObject::styleDidChange(diff, oldStyle);

  if (isFloatingOrOutOfFlowPositioned() && oldStyle &&
      !oldStyle->isFloating() && !oldStyle->hasOutOfFlowPosition() &&
      parent() && parent()->isLayoutBlockFlow())
    toLayoutBlockFlow(parent())->childBecameFloatingOrOutOfFlow(this);

  const ComputedStyle& newStyle = styleRef();
  if (needsLayout() && oldStyle)
    removeFromPercentHeightContainer();

  if (oldHorizontalWritingMode != isHorizontalWritingMode()) {
    if (oldStyle) {
      if (isOrthogonalWritingModeRoot())
        markOrthogonalWritingModeRoot();
      else
        unmarkOrthogonalWritingModeRoot();
    }

    clearPercentHeightDescendants();
  }

  // If our zoom factor changes and we have a defined scrollLeft/Top, we need to
  // adjust that value into the new zoomed coordinate space.  Note that the new
  // scroll offset may be outside the normal min/max range of the scrollable
  // area, which is weird but OK, because the scrollable area will update its
  // min/max in updateAfterLayout().
  if (hasOverflowClip() && oldStyle &&
      oldStyle->effectiveZoom() != newStyle.effectiveZoom()) {
    PaintLayerScrollableArea* scrollableArea = this->getScrollableArea();
    ASSERT(scrollableArea);
    // We use getScrollOffset() rather than scrollPosition(), because scroll
    // offset is the distance from the beginning of flow for the box, which is
    // the dimension we want to preserve.
    ScrollOffset oldOffset = scrollableArea->getScrollOffset();
    if (oldOffset.width() || oldOffset.height()) {
      ScrollOffset newOffset = oldOffset.scaledBy(newStyle.effectiveZoom() /
                                                  oldStyle->effectiveZoom());
      scrollableArea->setScrollOffsetUnconditionally(newOffset);
    }
  }

  // Our opaqueness might have changed without triggering layout.
  if (diff.needsPaintInvalidation()) {
    LayoutObject* parentToInvalidate = parent();
    for (unsigned i = 0;
         i < backgroundObscurationTestMaxDepth && parentToInvalidate; ++i) {
      parentToInvalidate->invalidateBackgroundObscurationStatus();
      parentToInvalidate = parentToInvalidate->parent();
    }
  }

  if (isDocumentElement() || isBody()) {
    document().view()->recalculateScrollbarOverlayColorTheme(
        document().view()->documentBackgroundColor());
    document().view()->recalculateCustomScrollbarStyle();
    if (LayoutView* layoutView = view()) {
      if (PaintLayerScrollableArea* scrollableArea =
              layoutView->getScrollableArea()) {
        if (scrollableArea->horizontalScrollbar() &&
            scrollableArea->horizontalScrollbar()->isCustomScrollbar())
          scrollableArea->horizontalScrollbar()->styleChanged();
        if (scrollableArea->verticalScrollbar() &&
            scrollableArea->verticalScrollbar()->isCustomScrollbar())
          scrollableArea->verticalScrollbar()->styleChanged();
      }
    }
  }
  updateShapeOutsideInfoAfterStyleChange(*style(), oldStyle);
  updateGridPositionAfterStyleChange(oldStyle);

  if (LayoutMultiColumnSpannerPlaceholder* placeholder =
          this->spannerPlaceholder())
    placeholder->layoutObjectInFlowThreadStyleDidChange(oldStyle);

  updateBackgroundAttachmentFixedStatusAfterStyleChange();

  if (oldStyle) {
    LayoutFlowThread* flowThread = flowThreadContainingBlock();
    if (flowThread && flowThread != this)
      flowThread->flowThreadDescendantStyleDidChange(this, diff, *oldStyle);

    updateScrollSnapMappingAfterStyleChange(&newStyle, oldStyle);

    if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() &&
        shouldClipOverflow()) {
      // The overflow clip paint property depends on border sizes through
      // overflowClipRect(), and border radii, so we update properties on
      // border size or radii change.
      if (!oldStyle->border().sizeEquals(newStyle.border()) ||
          !oldStyle->border().radiiEqual(newStyle.border()))
        setNeedsPaintPropertyUpdate();
    }
  }

  // Non-atomic inlines should be LayoutInline or LayoutText, not LayoutBox.
  DCHECK(!isInline() || isAtomicInlineLevel());
}

void LayoutBox::updateBackgroundAttachmentFixedStatusAfterStyleChange() {
  if (!frameView())
    return;

  // On low-powered/mobile devices, preventing blitting on a scroll can cause
  // noticeable delays when scrolling a page with a fixed background image. As
  // an optimization, assuming there are no fixed positoned elements on the
  // page, we can acclerate scrolling (via blitting) if we ignore the CSS
  // property "background-attachment: fixed".
  bool ignoreFixedBackgroundAttachment =
      RuntimeEnabledFeatures::fastMobileScrollingEnabled();
  if (ignoreFixedBackgroundAttachment)
    return;

  // An object needs to be repainted on frame scroll when it has background-
  // attachment:fixed. LayoutView is responsible for painting root background,
  // thus the root element (and the body element if html element has no
  // background) skips painting backgrounds.
  bool isBackgroundAttachmentFixedObject = !isDocumentElement() &&
                                           !backgroundStolenForBeingBody() &&
                                           styleRef().hasFixedBackgroundImage();
  if (isLayoutView() &&
      view()->compositor()->supportsFixedRootBackgroundCompositing()) {
    if (styleRef().hasEntirelyFixedBackground())
      isBackgroundAttachmentFixedObject = false;
  }

  setIsBackgroundAttachmentFixedObject(isBackgroundAttachmentFixedObject);
}

void LayoutBox::updateShapeOutsideInfoAfterStyleChange(
    const ComputedStyle& style,
    const ComputedStyle* oldStyle) {
  const ShapeValue* shapeOutside = style.shapeOutside();
  const ShapeValue* oldShapeOutside =
      oldStyle ? oldStyle->shapeOutside()
               : ComputedStyle::initialShapeOutside();

  Length shapeMargin = style.shapeMargin();
  Length oldShapeMargin =
      oldStyle ? oldStyle->shapeMargin() : ComputedStyle::initialShapeMargin();

  float shapeImageThreshold = style.shapeImageThreshold();
  float oldShapeImageThreshold =
      oldStyle ? oldStyle->shapeImageThreshold()
               : ComputedStyle::initialShapeImageThreshold();

  // FIXME: A future optimization would do a deep comparison for equality. (bug
  // 100811)
  if (shapeOutside == oldShapeOutside && shapeMargin == oldShapeMargin &&
      shapeImageThreshold == oldShapeImageThreshold)
    return;

  if (!shapeOutside)
    ShapeOutsideInfo::removeInfo(*this);
  else
    ShapeOutsideInfo::ensureInfo(*this).markShapeAsDirty();

  if (shapeOutside || shapeOutside != oldShapeOutside)
    markShapeOutsideDependentsForLayout();
}

void LayoutBox::updateGridPositionAfterStyleChange(
    const ComputedStyle* oldStyle) {
  if (!oldStyle || !parent() || !parent()->isLayoutGrid())
    return;

  if (oldStyle->gridColumnStart() == style()->gridColumnStart() &&
      oldStyle->gridColumnEnd() == style()->gridColumnEnd() &&
      oldStyle->gridRowStart() == style()->gridRowStart() &&
      oldStyle->gridRowEnd() == style()->gridRowEnd() &&
      oldStyle->order() == style()->order() &&
      oldStyle->hasOutOfFlowPosition() == style()->hasOutOfFlowPosition())
    return;

  // Positioned items don't participate on the layout of the grid,
  // so we don't need to mark the grid as dirty if they change positions.
  if (oldStyle->hasOutOfFlowPosition() && style()->hasOutOfFlowPosition())
    return;

  // It should be possible to not dirty the grid in some cases (like moving an
  // explicitly placed grid item).
  // For now, it's more simple to just always recompute the grid.
  toLayoutGrid(parent())->dirtyGrid();
}

void LayoutBox::updateScrollSnapMappingAfterStyleChange(
    const ComputedStyle* newStyle,
    const ComputedStyle* oldStyle) {
  SnapCoordinator* snapCoordinator = document().snapCoordinator();
  if (!snapCoordinator)
    return;

  // Scroll snap type has no effect on the viewport defining element instead
  // they are handled by the LayoutView.
  bool allowsSnapContainer = node() != document().viewportDefiningElement();

  ScrollSnapType oldSnapType =
      oldStyle ? oldStyle->getScrollSnapType() : ScrollSnapTypeNone;
  ScrollSnapType newSnapType = newStyle && allowsSnapContainer
                                   ? newStyle->getScrollSnapType()
                                   : ScrollSnapTypeNone;
  if (oldSnapType != newSnapType)
    snapCoordinator->snapContainerDidChange(*this, newSnapType);

  Vector<LengthPoint> emptyVector;
  const Vector<LengthPoint>& oldSnapCoordinate =
      oldStyle ? oldStyle->scrollSnapCoordinate() : emptyVector;
  const Vector<LengthPoint>& newSnapCoordinate =
      newStyle ? newStyle->scrollSnapCoordinate() : emptyVector;
  if (oldSnapCoordinate != newSnapCoordinate)
    snapCoordinator->snapAreaDidChange(*this, newSnapCoordinate);
}

void LayoutBox::addScrollSnapMapping() {
  updateScrollSnapMappingAfterStyleChange(style(), nullptr);
}

void LayoutBox::clearScrollSnapMapping() {
  updateScrollSnapMappingAfterStyleChange(nullptr, style());
}

void LayoutBox::updateFromStyle() {
  LayoutBoxModelObject::updateFromStyle();

  const ComputedStyle& styleToUse = styleRef();
  setFloating(!isOutOfFlowPositioned() && styleToUse.isFloating());
  setHasTransformRelatedProperty(styleToUse.hasTransformRelatedProperty());
  setHasReflection(styleToUse.boxReflect());
}

void LayoutBox::layout() {
  ASSERT(needsLayout());
  LayoutAnalyzer::Scope analyzer(*this);

  LayoutObject* child = slowFirstChild();
  if (!child) {
    clearNeedsLayout();
    return;
  }

  LayoutState state(*this);
  while (child) {
    child->layoutIfNeeded();
    ASSERT(!child->needsLayout());
    child = child->nextSibling();
  }
  invalidateBackgroundObscurationStatus();
  clearNeedsLayout();
}

// More IE extensions.  clientWidth and clientHeight represent the interior of
// an object excluding border and scrollbar.
DISABLE_CFI_PERF
LayoutUnit LayoutBox::clientWidth() const {
  return m_frameRect.width() - borderLeft() - borderRight() -
         verticalScrollbarWidth();
}

DISABLE_CFI_PERF
LayoutUnit LayoutBox::clientHeight() const {
  return m_frameRect.height() - borderTop() - borderBottom() -
         horizontalScrollbarHeight();
}

int LayoutBox::pixelSnappedClientWidth() const {
  return snapSizeToPixel(clientWidth(), location().x() + clientLeft());
}

DISABLE_CFI_PERF
int LayoutBox::pixelSnappedClientHeight() const {
  return snapSizeToPixel(clientHeight(), location().y() + clientTop());
}

int LayoutBox::pixelSnappedOffsetWidth(const Element*) const {
  return snapSizeToPixel(offsetWidth(), location().x() + clientLeft());
}

int LayoutBox::pixelSnappedOffsetHeight(const Element*) const {
  return snapSizeToPixel(offsetHeight(), location().y() + clientTop());
}

LayoutUnit LayoutBox::scrollWidth() const {
  if (hasOverflowClip())
    return getScrollableArea()->scrollWidth();
  // For objects with visible overflow, this matches IE.
  // FIXME: Need to work right with writing modes.
  if (style()->isLeftToRightDirection())
    return std::max(clientWidth(), layoutOverflowRect().maxX() - borderLeft());
  return clientWidth() -
         std::min(LayoutUnit(), layoutOverflowRect().x() - borderLeft());
}

LayoutUnit LayoutBox::scrollHeight() const {
  if (hasOverflowClip())
    return getScrollableArea()->scrollHeight();
  // For objects with visible overflow, this matches IE.
  // FIXME: Need to work right with writing modes.
  return std::max(clientHeight(), layoutOverflowRect().maxY() - borderTop());
}

LayoutUnit LayoutBox::scrollLeft() const {
  return hasOverflowClip()
             ? LayoutUnit(getScrollableArea()->scrollPosition().x())
             : LayoutUnit();
}

LayoutUnit LayoutBox::scrollTop() const {
  return hasOverflowClip()
             ? LayoutUnit(getScrollableArea()->scrollPosition().y())
             : LayoutUnit();
}

int LayoutBox::pixelSnappedScrollWidth() const {
  return snapSizeToPixel(scrollWidth(), location().x() + clientLeft());
}

int LayoutBox::pixelSnappedScrollHeight() const {
  if (hasOverflowClip())
    return snapSizeToPixel(getScrollableArea()->scrollHeight(),
                           location().y() + clientTop());
  // For objects with visible overflow, this matches IE.
  // FIXME: Need to work right with writing modes.
  return snapSizeToPixel(scrollHeight(), location().y() + clientTop());
}

void LayoutBox::setScrollLeft(LayoutUnit newLeft) {
  // This doesn't hit in any tests, but since the equivalent code in
  // setScrollTop does, presumably this code does as well.
  DisableCompositingQueryAsserts disabler;

  if (!hasOverflowClip())
    return;

  PaintLayerScrollableArea* scrollableArea = getScrollableArea();
  FloatPoint newPosition(newLeft.toFloat(),
                         scrollableArea->scrollPosition().y());
  scrollableArea->scrollToAbsolutePosition(newPosition, ScrollBehaviorAuto);
}

void LayoutBox::setScrollTop(LayoutUnit newTop) {
  // Hits in
  // compositing/overflow/do-not-assert-on-invisible-composited-layers.html
  DisableCompositingQueryAsserts disabler;

  if (!hasOverflowClip())
    return;

  PaintLayerScrollableArea* scrollableArea = getScrollableArea();
  FloatPoint newPosition(scrollableArea->scrollPosition().x(),
                         newTop.toFloat());
  scrollableArea->scrollToAbsolutePosition(newPosition, ScrollBehaviorAuto);
}

void LayoutBox::scrollToPosition(const FloatPoint& position,
                                 ScrollBehavior scrollBehavior) {
  // This doesn't hit in any tests, but since the equivalent code in
  // setScrollTop does, presumably this code does as well.
  DisableCompositingQueryAsserts disabler;

  if (!hasOverflowClip())
    return;

  getScrollableArea()->scrollToAbsolutePosition(position, scrollBehavior);
}

// Returns true iff we are attempting an autoscroll inside an iframe with
// scrolling="no".
static bool isDisallowedAutoscroll(HTMLFrameOwnerElement* ownerElement,
                                   FrameView* frameView) {
  if (ownerElement && isHTMLFrameElementBase(*ownerElement)) {
    HTMLFrameElementBase* frameElementBase =
        toHTMLFrameElementBase(ownerElement);
    if (Page* page = frameView->frame().page()) {
      return page->autoscrollController().autoscrollInProgress() &&
             frameElementBase->scrollingMode() == ScrollbarAlwaysOff;
    }
  }
  return false;
}

void LayoutBox::scrollRectToVisible(const LayoutRect& rect,
                                    const ScrollAlignment& alignX,
                                    const ScrollAlignment& alignY,
                                    ScrollType scrollType,
                                    bool makeVisibleInVisualViewport) {
  ASSERT(scrollType == ProgrammaticScroll || scrollType == UserScroll);
  // Presumably the same issue as in setScrollTop. See crbug.com/343132.
  DisableCompositingQueryAsserts disabler;

  LayoutRect rectToScroll = rect;
  if (rectToScroll.width() <= 0)
    rectToScroll.setWidth(LayoutUnit(1));
  if (rectToScroll.height() <= 0)
    rectToScroll.setHeight(LayoutUnit(1));

  LayoutBox* parentBox = nullptr;
  LayoutRect newRect = rectToScroll;

  bool restrictedByLineClamp = false;
  if (containingBlock()) {
    parentBox = containingBlock();
    restrictedByLineClamp = !containingBlock()->style()->lineClamp().isNone();
  }

  if (hasOverflowClip() && !restrictedByLineClamp) {
    // Don't scroll to reveal an overflow layer that is restricted by the
    // -webkit-line-clamp property. This will prevent us from revealing text
    // hidden by the slider in Safari RSS.
    // TODO(eae): We probably don't need this any more as we don't share any
    //            code with the Safari RSS reeder.
    newRect = getScrollableArea()->scrollIntoView(rectToScroll, alignX, alignY,
                                                  scrollType);
    if (newRect.isEmpty())
      return;
  } else if (!parentBox && canBeProgramaticallyScrolled()) {
    if (FrameView* frameView = this->frameView()) {
      HTMLFrameOwnerElement* ownerElement = document().localOwner();
      if (!isDisallowedAutoscroll(ownerElement, frameView)) {
        if (makeVisibleInVisualViewport) {
          frameView->getScrollableArea()->scrollIntoView(rectToScroll, alignX,
                                                         alignY, scrollType);
        } else {
          frameView->layoutViewportScrollableArea()->scrollIntoView(
              rectToScroll, alignX, alignY, scrollType);
        }
        if (ownerElement && ownerElement->layoutObject()) {
          if (frameView->safeToPropagateScrollToParent()) {
            parentBox = ownerElement->layoutObject()->enclosingBox();
            LayoutView* parentView = ownerElement->layoutObject()->view();
            newRect = enclosingLayoutRect(
                view()
                    ->localToAncestorQuad(
                        FloatRect(rectToScroll), parentView,
                        UseTransforms | TraverseDocumentBoundaries)
                    .boundingBox());
          } else {
            parentBox = nullptr;
          }
        }
      }
    }
  }

  // If we are fixed-position and stick to the viewport, it is useless to
  // scroll the parent.
  if (style()->position() == FixedPosition &&
      containerForFixedPosition() == view()) {
    return;
  }

  if (frame()->page()->autoscrollController().autoscrollInProgress())
    parentBox = enclosingScrollableBox();

  if (parentBox)
    parentBox->scrollRectToVisible(newRect, alignX, alignY, scrollType,
                                   makeVisibleInVisualViewport);
}

void LayoutBox::absoluteRects(Vector<IntRect>& rects,
                              const LayoutPoint& accumulatedOffset) const {
  rects.append(pixelSnappedIntRect(accumulatedOffset, size()));
}

void LayoutBox::absoluteQuads(Vector<FloatQuad>& quads) const {
  if (LayoutFlowThread* flowThread = flowThreadContainingBlock()) {
    flowThread->absoluteQuadsForDescendant(*this, quads);
    return;
  }
  quads.append(localToAbsoluteQuad(FloatRect(
      0, 0, m_frameRect.width().toFloat(), m_frameRect.height().toFloat())));
}

FloatRect LayoutBox::localBoundingBoxRectForAccessibility() const {
  return FloatRect(0, 0, m_frameRect.width().toFloat(),
                   m_frameRect.height().toFloat());
}

void LayoutBox::updateLayerTransformAfterLayout() {
  // Transform-origin depends on box size, so we need to update the layer
  // transform after layout.
  if (hasLayer())
    layer()->updateTransformationMatrix();
}

LayoutUnit LayoutBox::logicalHeightWithVisibleOverflow() const {
  if (!m_overflow || hasOverflowClip())
    return logicalHeight();
  LayoutRect overflow = layoutOverflowRect();
  if (style()->isHorizontalWritingMode())
    return overflow.maxY();
  return overflow.maxX();
}

LayoutUnit LayoutBox::constrainLogicalWidthByMinMax(LayoutUnit logicalWidth,
                                                    LayoutUnit availableWidth,
                                                    LayoutBlock* cb) const {
  const ComputedStyle& styleToUse = styleRef();
  if (!styleToUse.logicalMaxWidth().isMaxSizeNone())
    logicalWidth =
        std::min(logicalWidth,
                 computeLogicalWidthUsing(MaxSize, styleToUse.logicalMaxWidth(),
                                          availableWidth, cb));
  return std::max(logicalWidth, computeLogicalWidthUsing(
                                    MinSize, styleToUse.logicalMinWidth(),
                                    availableWidth, cb));
}

LayoutUnit LayoutBox::constrainLogicalHeightByMinMax(
    LayoutUnit logicalHeight,
    LayoutUnit intrinsicContentHeight) const {
  const ComputedStyle& styleToUse = styleRef();
  if (!styleToUse.logicalMaxHeight().isMaxSizeNone()) {
    LayoutUnit maxH = computeLogicalHeightUsing(
        MaxSize, styleToUse.logicalMaxHeight(), intrinsicContentHeight);
    if (maxH != -1)
      logicalHeight = std::min(logicalHeight, maxH);
  }
  return std::max(logicalHeight, computeLogicalHeightUsing(
                                     MinSize, styleToUse.logicalMinHeight(),
                                     intrinsicContentHeight));
}

LayoutUnit LayoutBox::constrainContentBoxLogicalHeightByMinMax(
    LayoutUnit logicalHeight,
    LayoutUnit intrinsicContentHeight) const {
  // If the min/max height and logical height are both percentages we take
  // advantage of already knowing the current resolved percentage height
  // to avoid recursing up through our containing blocks again to determine it.
  const ComputedStyle& styleToUse = styleRef();
  if (!styleToUse.logicalMaxHeight().isMaxSizeNone()) {
    if (styleToUse.logicalMaxHeight().type() == Percent &&
        styleToUse.logicalHeight().type() == Percent) {
      LayoutUnit availableLogicalHeight(
          logicalHeight / styleToUse.logicalHeight().value() * 100);
      logicalHeight =
          std::min(logicalHeight, valueForLength(styleToUse.logicalMaxHeight(),
                                                 availableLogicalHeight));
    } else {
      LayoutUnit maxHeight(computeContentLogicalHeight(
          MaxSize, styleToUse.logicalMaxHeight(), intrinsicContentHeight));
      if (maxHeight != -1)
        logicalHeight = std::min(logicalHeight, maxHeight);
    }
  }

  if (styleToUse.logicalMinHeight().type() == Percent &&
      styleToUse.logicalHeight().type() == Percent) {
    LayoutUnit availableLogicalHeight(logicalHeight /
                                      styleToUse.logicalHeight().value() * 100);
    logicalHeight = std::max(
        logicalHeight,
        valueForLength(styleToUse.logicalMinHeight(), availableLogicalHeight));
  } else {
    logicalHeight = std::max(
        logicalHeight,
        computeContentLogicalHeight(MinSize, styleToUse.logicalMinHeight(),
                                    intrinsicContentHeight));
  }

  return logicalHeight;
}

void LayoutBox::setLocationAndUpdateOverflowControlsIfNeeded(
    const LayoutPoint& location) {
  if (hasOverflowClip()) {
    IntSize oldPixelSnappedBorderRectSize = pixelSnappedBorderBoxRect().size();
    setLocation(location);
    if (pixelSnappedBorderBoxRect().size() != oldPixelSnappedBorderRectSize)
      getScrollableArea()->updateAfterLayout();
    return;
  }

  setLocation(location);
}

IntRect LayoutBox::absoluteContentBox() const {
  // This is wrong with transforms and flipped writing modes.
  IntRect rect = pixelSnappedIntRect(contentBoxRect());
  FloatPoint absPos = localToAbsolute();
  rect.move(absPos.x(), absPos.y());
  return rect;
}

IntSize LayoutBox::absoluteContentBoxOffset() const {
  IntPoint offset = roundedIntPoint(contentBoxOffset());
  FloatPoint absPos = localToAbsolute();
  offset.move(absPos.x(), absPos.y());
  return toIntSize(offset);
}

FloatQuad LayoutBox::absoluteContentQuad() const {
  LayoutRect rect = contentBoxRect();
  return localToAbsoluteQuad(FloatRect(rect));
}

LayoutRect LayoutBox::backgroundRect(BackgroundRectType rectType) const {
  EFillBox backgroundBox = TextFillBox;
  // Find the largest background rect of the given opaqueness.
  if (const FillLayer* current = &(style()->backgroundLayers())) {
    do {
      const FillLayer* cur = current;
      current = current->next();
      if (rectType == BackgroundKnownOpaqueRect) {
        if (cur->blendMode() != WebBlendModeNormal ||
            cur->composite() != CompositeSourceOver)
          continue;

        bool layerKnownOpaque = false;
        // Check if the image is opaque and fills the clip.
        if (const StyleImage* image = cur->image()) {
          if ((cur->repeatX() == RepeatFill || cur->repeatX() == RoundFill) &&
              (cur->repeatY() == RepeatFill || cur->repeatY() == RoundFill) &&
              image->knownToBeOpaque(*this)) {
            layerKnownOpaque = true;
          }
        }

        // The background color is painted into the last layer.
        if (!cur->next()) {
          Color backgroundColor = resolveColor(CSSPropertyBackgroundColor);
          if (!backgroundColor.hasAlpha())
            layerKnownOpaque = true;
        }

        // If neither the image nor the color are opaque then skip this layer.
        if (!layerKnownOpaque)
          continue;
      }
      EFillBox currentClip = cur->clip();
      // Restrict clip if attachment is local.
      if (currentClip == BorderFillBox &&
          cur->attachment() == LocalBackgroundAttachment)
        currentClip = PaddingFillBox;

      // If we're asking for the clip rect, a content-box clipped fill layer can
      // be scrolled into the padding box of the overflow container.
      if (rectType == BackgroundClipRect && currentClip == ContentFillBox &&
          cur->attachment() == LocalBackgroundAttachment) {
        currentClip = PaddingFillBox;
      }

      backgroundBox = enclosingFillBox(backgroundBox, currentClip);
    } while (current);
  }
  switch (backgroundBox) {
    case BorderFillBox:
      return borderBoxRect();
      break;
    case PaddingFillBox:
      return paddingBoxRect();
      break;
    case ContentFillBox:
      return contentBoxRect();
      break;
    default:
      break;
  }
  return LayoutRect();
}

void LayoutBox::addOutlineRects(Vector<LayoutRect>& rects,
                                const LayoutPoint& additionalOffset,
                                IncludeBlockVisualOverflowOrNot) const {
  rects.append(LayoutRect(additionalOffset, size()));
}

bool LayoutBox::canResize() const {
  // We need a special case for <iframe> because they never have
  // hasOverflowClip(). However, they do "implicitly" clip their contents, so
  // we want to allow resizing them also.
  return (hasOverflowClip() || isLayoutIFrame()) &&
         style()->resize() != RESIZE_NONE;
}

void LayoutBox::addLayerHitTestRects(LayerHitTestRects& layerRects,
                                     const PaintLayer* currentLayer,
                                     const LayoutPoint& layerOffset,
                                     const LayoutRect& containerRect) const {
  LayoutPoint adjustedLayerOffset = layerOffset + locationOffset();
  LayoutBoxModelObject::addLayerHitTestRects(
      layerRects, currentLayer, adjustedLayerOffset, containerRect);
}

void LayoutBox::computeSelfHitTestRects(Vector<LayoutRect>& rects,
                                        const LayoutPoint& layerOffset) const {
  if (!size().isEmpty())
    rects.append(LayoutRect(layerOffset, size()));
}

int LayoutBox::verticalScrollbarWidth() const {
  if (!hasOverflowClip() || style()->overflowY() == EOverflow::Overlay)
    return 0;

  return getScrollableArea()->verticalScrollbarWidth();
}

int LayoutBox::horizontalScrollbarHeight() const {
  if (!hasOverflowClip() || style()->overflowX() == EOverflow::Overlay)
    return 0;

  return getScrollableArea()->horizontalScrollbarHeight();
}

ScrollResult LayoutBox::scroll(ScrollGranularity granularity,
                               const FloatSize& delta) {
  // Presumably the same issue as in setScrollTop. See crbug.com/343132.
  DisableCompositingQueryAsserts disabler;

  if (!getScrollableArea())
    return ScrollResult();

  return getScrollableArea()->userScroll(granularity, delta);
}

bool LayoutBox::canBeScrolledAndHasScrollableArea() const {
  return canBeProgramaticallyScrolled() &&
         (pixelSnappedScrollHeight() != pixelSnappedClientHeight() ||
          pixelSnappedScrollWidth() != pixelSnappedClientWidth());
}

bool LayoutBox::canBeProgramaticallyScrolled() const {
  Node* node = this->node();
  if (node && node->isDocumentNode())
    return true;

  if (!hasOverflowClip())
    return false;

  bool hasScrollableOverflow =
      hasScrollableOverflowX() || hasScrollableOverflowY();
  if (scrollsOverflow() && hasScrollableOverflow)
    return true;

  return node && hasEditableStyle(*node);
}

void LayoutBox::autoscroll(const IntPoint& positionInRootFrame) {
  LocalFrame* frame = this->frame();
  if (!frame)
    return;

  FrameView* frameView = frame->view();
  if (!frameView)
    return;

  IntPoint positionInContent =
      frameView->rootFrameToContents(positionInRootFrame);
  scrollRectToVisible(LayoutRect(positionInContent, LayoutSize(1, 1)),
                      ScrollAlignment::alignToEdgeIfNeeded,
                      ScrollAlignment::alignToEdgeIfNeeded, UserScroll);
}

// There are two kinds of layoutObject that can autoscroll.
bool LayoutBox::canAutoscroll() const {
  if (node() && node()->isDocumentNode())
    return view()->frameView()->isScrollable();

  // Check for a box that can be scrolled in its own right.
  return canBeScrolledAndHasScrollableArea();
}

// If specified point is in border belt, returned offset denotes direction of
// scrolling.
IntSize LayoutBox::calculateAutoscrollDirection(
    const IntPoint& pointInRootFrame) const {
  if (!frame())
    return IntSize();

  FrameView* frameView = frame()->view();
  if (!frameView)
    return IntSize();

  IntRect box(absoluteBoundingBoxRect());
  box.move(view()->frameView()->scrollOffsetInt());
  IntRect windowBox = view()->frameView()->contentsToRootFrame(box);

  IntPoint windowAutoscrollPoint = pointInRootFrame;

  if (windowAutoscrollPoint.x() < windowBox.x() + autoscrollBeltSize)
    windowAutoscrollPoint.move(-autoscrollBeltSize, 0);
  else if (windowAutoscrollPoint.x() > windowBox.maxX() - autoscrollBeltSize)
    windowAutoscrollPoint.move(autoscrollBeltSize, 0);

  if (windowAutoscrollPoint.y() < windowBox.y() + autoscrollBeltSize)
    windowAutoscrollPoint.move(0, -autoscrollBeltSize);
  else if (windowAutoscrollPoint.y() > windowBox.maxY() - autoscrollBeltSize)
    windowAutoscrollPoint.move(0, autoscrollBeltSize);

  return windowAutoscrollPoint - pointInRootFrame;
}

LayoutBox* LayoutBox::findAutoscrollable(LayoutObject* layoutObject) {
  while (
      layoutObject &&
      !(layoutObject->isBox() && toLayoutBox(layoutObject)->canAutoscroll())) {
    // Do not start autoscroll when the node is inside a fixed-position element.
    if (layoutObject->isBox() && toLayoutBox(layoutObject)->hasLayer() &&
        toLayoutBox(layoutObject)->layer()->sticksToViewport()) {
      return nullptr;
    }

    if (!layoutObject->parent() &&
        layoutObject->node() == layoutObject->document() &&
        layoutObject->document().localOwner())
      layoutObject = layoutObject->document().localOwner()->layoutObject();
    else
      layoutObject = layoutObject->parent();
  }

  return layoutObject && layoutObject->isBox() ? toLayoutBox(layoutObject)
                                               : nullptr;
}

void LayoutBox::scrollByRecursively(const ScrollOffset& delta) {
  if (delta.isZero())
    return;

  bool restrictedByLineClamp = false;
  if (parent())
    restrictedByLineClamp = !parent()->style()->lineClamp().isNone();

  if (hasOverflowClip() && !restrictedByLineClamp) {
    PaintLayerScrollableArea* scrollableArea = this->getScrollableArea();
    ASSERT(scrollableArea);

    ScrollOffset newScrollOffset = scrollableArea->getScrollOffset() + delta;
    scrollableArea->setScrollOffset(newScrollOffset, ProgrammaticScroll);

    // If this layer can't do the scroll we ask the next layer up that can
    // scroll to try.
    ScrollOffset remainingScrollOffset =
        newScrollOffset - scrollableArea->getScrollOffset();
    if (!remainingScrollOffset.isZero() && parent()) {
      if (LayoutBox* scrollableBox = enclosingScrollableBox())
        scrollableBox->scrollByRecursively(remainingScrollOffset);

      LocalFrame* frame = this->frame();
      if (frame && frame->page())
        frame->page()->autoscrollController().updateAutoscrollLayoutObject();
    }
  } else if (view()->frameView()) {
    // If we are here, we were called on a layoutObject that can be
    // programmatically scrolled, but doesn't have an overflow clip. Which means
    // that it is a document node that can be scrolled.
    // FIXME: Pass in DoubleSize. crbug.com/414283.
    view()->frameView()->scrollBy(delta, UserScroll);

    // FIXME: If we didn't scroll the whole way, do we want to try looking at
    // the frames ownerElement?
    // https://bugs.webkit.org/show_bug.cgi?id=28237
  }
}

bool LayoutBox::needsPreferredWidthsRecalculation() const {
  return style()->paddingStart().isPercentOrCalc() ||
         style()->paddingEnd().isPercentOrCalc();
}

IntSize LayoutBox::originAdjustmentForScrollbars() const {
  IntSize size;
  int adjustmentWidth = verticalScrollbarWidth();
  if (hasFlippedBlocksWritingMode() ||
      (isHorizontalWritingMode() &&
       shouldPlaceBlockDirectionScrollbarOnLogicalLeft())) {
    size.expand(adjustmentWidth, 0);
  }
  return size;
}

IntSize LayoutBox::scrolledContentOffset() const {
  ASSERT(hasOverflowClip());
  ASSERT(hasLayer());
  // FIXME: Return DoubleSize here. crbug.com/414283.
  PaintLayerScrollableArea* scrollableArea = getScrollableArea();
  IntSize result =
      scrollableArea->scrollOffsetInt() + originAdjustmentForScrollbars();
  if (isHorizontalWritingMode() &&
      shouldPlaceBlockDirectionScrollbarOnLogicalLeft())
    result.expand(-verticalScrollbarWidth(), 0);
  return result;
}

LayoutRect LayoutBox::clippingRect() const {
  LayoutRect result = LayoutRect(LayoutRect::infiniteIntRect());
  if (hasOverflowClip() || style()->containsPaint())
    result = overflowClipRect(LayoutPoint());

  if (hasClip())
    result.intersect(clipRect(LayoutPoint()));

  return result;
}

bool LayoutBox::mapScrollingContentsRectToBoxSpace(
    LayoutRect& rect,
    VisualRectFlags visualRectFlags) const {
  if (!hasClipRelatedProperty())
    return true;

  if (hasOverflowClip()) {
    LayoutSize offset = LayoutSize(-scrolledContentOffset());
    rect.move(offset);
  }

  // This won't work fully correctly for fixed-position elements, who should
  // receive CSS clip but for whom the current object is not in the containing
  // block chain.
  LayoutRect clipRect = clippingRect();

  bool doesIntersect;
  if (visualRectFlags & EdgeInclusive) {
    doesIntersect = rect.inclusiveIntersect(clipRect);
  } else {
    rect.intersect(clipRect);
    doesIntersect = !rect.isEmpty();
  }

  return doesIntersect;
}

void LayoutBox::computeIntrinsicLogicalWidths(
    LayoutUnit& minLogicalWidth,
    LayoutUnit& maxLogicalWidth) const {
  minLogicalWidth = minPreferredLogicalWidth() - borderAndPaddingLogicalWidth();
  maxLogicalWidth = maxPreferredLogicalWidth() - borderAndPaddingLogicalWidth();
}

LayoutUnit LayoutBox::minPreferredLogicalWidth() const {
  if (preferredLogicalWidthsDirty()) {
#if DCHECK_IS_ON()
    SetLayoutNeededForbiddenScope layoutForbiddenScope(
        const_cast<LayoutBox&>(*this));
#endif
    const_cast<LayoutBox*>(this)->computePreferredLogicalWidths();
    ASSERT(!preferredLogicalWidthsDirty());
  }

  return m_minPreferredLogicalWidth;
}

DISABLE_CFI_PERF
LayoutUnit LayoutBox::maxPreferredLogicalWidth() const {
  if (preferredLogicalWidthsDirty()) {
#if DCHECK_IS_ON()
    SetLayoutNeededForbiddenScope layoutForbiddenScope(
        const_cast<LayoutBox&>(*this));
#endif
    const_cast<LayoutBox*>(this)->computePreferredLogicalWidths();
    ASSERT(!preferredLogicalWidthsDirty());
  }

  return m_maxPreferredLogicalWidth;
}

bool LayoutBox::hasOverrideLogicalContentHeight() const {
  return m_rareData && m_rareData->m_overrideLogicalContentHeight != -1;
}

bool LayoutBox::hasOverrideLogicalContentWidth() const {
  return m_rareData && m_rareData->m_overrideLogicalContentWidth != -1;
}

void LayoutBox::setOverrideLogicalContentHeight(LayoutUnit height) {
  ASSERT(height >= 0);
  ensureRareData().m_overrideLogicalContentHeight = height;
}

void LayoutBox::setOverrideLogicalContentWidth(LayoutUnit width) {
  ASSERT(width >= 0);
  ensureRareData().m_overrideLogicalContentWidth = width;
}

void LayoutBox::clearOverrideLogicalContentHeight() {
  if (m_rareData)
    m_rareData->m_overrideLogicalContentHeight = LayoutUnit(-1);
}

void LayoutBox::clearOverrideLogicalContentWidth() {
  if (m_rareData)
    m_rareData->m_overrideLogicalContentWidth = LayoutUnit(-1);
}

void LayoutBox::clearOverrideSize() {
  clearOverrideLogicalContentHeight();
  clearOverrideLogicalContentWidth();
}

LayoutUnit LayoutBox::overrideLogicalContentWidth() const {
  ASSERT(hasOverrideLogicalContentWidth());
  return m_rareData->m_overrideLogicalContentWidth;
}

LayoutUnit LayoutBox::overrideLogicalContentHeight() const {
  ASSERT(hasOverrideLogicalContentHeight());
  return m_rareData->m_overrideLogicalContentHeight;
}

// TODO (lajava) Now that we have implemented these functions based on physical
// direction, we'd rather remove the logical ones.
LayoutUnit LayoutBox::overrideContainingBlockContentLogicalWidth() const {
  DCHECK(hasOverrideContainingBlockLogicalWidth());
  return m_rareData->m_overrideContainingBlockContentLogicalWidth;
}

// TODO (lajava) Shouldn't we implement these functions based on physical
// direction ?.
LayoutUnit LayoutBox::overrideContainingBlockContentLogicalHeight() const {
  DCHECK(hasOverrideContainingBlockLogicalHeight());
  return m_rareData->m_overrideContainingBlockContentLogicalHeight;
}

// TODO (lajava) Shouldn't we implement these functions based on physical
// direction ?.
bool LayoutBox::hasOverrideContainingBlockLogicalWidth() const {
  return m_rareData &&
         m_rareData->m_hasOverrideContainingBlockContentLogicalWidth;
}

// TODO (lajava) Shouldn't we implement these functions based on physical
// direction ?.
bool LayoutBox::hasOverrideContainingBlockLogicalHeight() const {
  return m_rareData &&
         m_rareData->m_hasOverrideContainingBlockContentLogicalHeight;
}

// TODO (lajava) Shouldn't we implement these functions based on physical
// direction ?.
void LayoutBox::setOverrideContainingBlockContentLogicalWidth(
    LayoutUnit logicalWidth) {
  DCHECK_GE(logicalWidth, LayoutUnit(-1));
  ensureRareData().m_overrideContainingBlockContentLogicalWidth = logicalWidth;
  ensureRareData().m_hasOverrideContainingBlockContentLogicalWidth = true;
}

// TODO (lajava) Shouldn't we implement these functions based on physical
// direction ?.
void LayoutBox::setOverrideContainingBlockContentLogicalHeight(
    LayoutUnit logicalHeight) {
  DCHECK_GE(logicalHeight, LayoutUnit(-1));
  ensureRareData().m_overrideContainingBlockContentLogicalHeight =
      logicalHeight;
  ensureRareData().m_hasOverrideContainingBlockContentLogicalHeight = true;
}

// TODO (lajava) Shouldn't we implement these functions based on physical
// direction ?.
void LayoutBox::clearContainingBlockOverrideSize() {
  if (!m_rareData)
    return;
  ensureRareData().m_hasOverrideContainingBlockContentLogicalWidth = false;
  ensureRareData().m_hasOverrideContainingBlockContentLogicalHeight = false;
}

// TODO (lajava) Shouldn't we implement these functions based on physical
// direction ?.
void LayoutBox::clearOverrideContainingBlockContentLogicalHeight() {
  if (!m_rareData)
    return;
  ensureRareData().m_hasOverrideContainingBlockContentLogicalHeight = false;
}

LayoutUnit LayoutBox::extraInlineOffset() const {
  return gExtraInlineOffsetMap ? gExtraInlineOffsetMap->get(this)
                               : LayoutUnit();
}

LayoutUnit LayoutBox::extraBlockOffset() const {
  return gExtraBlockOffsetMap ? gExtraBlockOffsetMap->get(this) : LayoutUnit();
}

void LayoutBox::setExtraInlineOffset(LayoutUnit inlineOffest) {
  if (!gExtraInlineOffsetMap)
    gExtraInlineOffsetMap = new OverrideSizeMap;
  gExtraInlineOffsetMap->set(this, inlineOffest);
}

void LayoutBox::setExtraBlockOffset(LayoutUnit blockOffest) {
  if (!gExtraBlockOffsetMap)
    gExtraBlockOffsetMap = new OverrideSizeMap;
  gExtraBlockOffsetMap->set(this, blockOffest);
}

void LayoutBox::clearExtraInlineAndBlockOffests() {
  if (gExtraInlineOffsetMap)
    gExtraInlineOffsetMap->remove(this);
  if (gExtraBlockOffsetMap)
    gExtraBlockOffsetMap->remove(this);
}

LayoutUnit LayoutBox::adjustBorderBoxLogicalWidthForBoxSizing(
    float width) const {
  LayoutUnit bordersPlusPadding = collapsedBorderAndCSSPaddingLogicalWidth();
  LayoutUnit result(width);
  if (style()->boxSizing() == BoxSizingContentBox)
    return result + bordersPlusPadding;
  return std::max(result, bordersPlusPadding);
}

LayoutUnit LayoutBox::adjustBorderBoxLogicalHeightForBoxSizing(
    float height) const {
  LayoutUnit bordersPlusPadding = collapsedBorderAndCSSPaddingLogicalHeight();
  LayoutUnit result(height);
  if (style()->boxSizing() == BoxSizingContentBox)
    return result + bordersPlusPadding;
  return std::max(result, bordersPlusPadding);
}

LayoutUnit LayoutBox::adjustContentBoxLogicalWidthForBoxSizing(
    float width) const {
  LayoutUnit result(width);
  if (style()->boxSizing() == BoxSizingBorderBox)
    result -= collapsedBorderAndCSSPaddingLogicalWidth();
  return std::max(LayoutUnit(), result);
}

LayoutUnit LayoutBox::adjustContentBoxLogicalHeightForBoxSizing(
    float height) const {
  LayoutUnit result(height);
  if (style()->boxSizing() == BoxSizingBorderBox)
    result -= collapsedBorderAndCSSPaddingLogicalHeight();
  return std::max(LayoutUnit(), result);
}

// Hit Testing
bool LayoutBox::nodeAtPoint(HitTestResult& result,
                            const HitTestLocation& locationInContainer,
                            const LayoutPoint& accumulatedOffset,
                            HitTestAction action) {
  LayoutPoint adjustedLocation = accumulatedOffset + location();

  if (!isLayoutView()) {
    // Check if we need to do anything at all.
    // If we have clipping, then we can't have any spillout.
    LayoutRect overflowBox =
        hasOverflowClip() ? borderBoxRect() : visualOverflowRect();
    flipForWritingMode(overflowBox);
    overflowBox.moveBy(adjustedLocation);
    if (!locationInContainer.intersects(overflowBox))
      return false;
  }

  bool shouldHitTestSelf = isInSelfHitTestingPhase(action);

  if (shouldHitTestSelf && hasOverflowClip() &&
      hitTestOverflowControl(result, locationInContainer, adjustedLocation))
    return true;

  // TODO(pdr): We should also check for css clip in the !isSelfPaintingLayer
  //            case, similar to overflow clip below.
  bool skipChildren = false;
  if (hasOverflowClip() && !hasSelfPaintingLayer()) {
    if (!locationInContainer.intersects(overflowClipRect(
            adjustedLocation, ExcludeOverlayScrollbarSizeForHitTesting))) {
      skipChildren = true;
    } else if (style()->hasBorderRadius()) {
      LayoutRect boundsRect(adjustedLocation, size());
      skipChildren = !locationInContainer.intersects(
          style()->getRoundedInnerBorderFor(boundsRect));
    }
  }

  // A control clip can also clip out child hit testing.
  if (!skipChildren && hasControlClip() &&
      !locationInContainer.intersects(controlClipRect(adjustedLocation)))
    skipChildren = true;

  // TODO(pdr): We should also include checks for hit testing border radius at
  //            the layer level (see: crbug.com/568904).

  if (!skipChildren &&
      hitTestChildren(result, locationInContainer, adjustedLocation, action))
    return true;

  if (hitTestClippedOutByRoundedBorder(locationInContainer, adjustedLocation))
    return false;

  // Now hit test ourselves.
  if (shouldHitTestSelf && visibleToHitTestRequest(result.hitTestRequest())) {
    LayoutRect boundsRect(adjustedLocation, size());
    if (locationInContainer.intersects(boundsRect)) {
      updateHitTestResult(result,
                          flipForWritingMode(locationInContainer.point() -
                                             toLayoutSize(adjustedLocation)));
      if (result.addNodeToListBasedTestResult(nodeForHitTest(),
                                              locationInContainer,
                                              boundsRect) == StopHitTesting)
        return true;
    }
  }

  return false;
}

bool LayoutBox::hitTestChildren(HitTestResult& result,
                                const HitTestLocation& locationInContainer,
                                const LayoutPoint& accumulatedOffset,
                                HitTestAction action) {
  for (LayoutObject* child = slowLastChild(); child;
       child = child->previousSibling()) {
    if ((!child->hasLayer() ||
         !toLayoutBoxModelObject(child)->layer()->isSelfPaintingLayer()) &&
        child->nodeAtPoint(result, locationInContainer, accumulatedOffset,
                           action))
      return true;
  }

  return false;
}

bool LayoutBox::hitTestClippedOutByRoundedBorder(
    const HitTestLocation& locationInContainer,
    const LayoutPoint& borderBoxLocation) const {
  if (!style()->hasBorderRadius())
    return false;

  LayoutRect borderRect = borderBoxRect();
  borderRect.moveBy(borderBoxLocation);
  return !locationInContainer.intersects(
      style()->getRoundedBorderFor(borderRect));
}

void LayoutBox::paint(const PaintInfo& paintInfo,
                      const LayoutPoint& paintOffset) const {
  BoxPainter(*this).paint(paintInfo, paintOffset);
}

void LayoutBox::paintBoxDecorationBackground(
    const PaintInfo& paintInfo,
    const LayoutPoint& paintOffset) const {
  BoxPainter(*this).paintBoxDecorationBackground(paintInfo, paintOffset);
}

bool LayoutBox::getBackgroundPaintedExtent(LayoutRect& paintedExtent) const {
  DCHECK(styleRef().hasBackground());

  // LayoutView is special in the sense that it expands to the whole canvas,
  // thus can't be handled by this function.
  DCHECK(!isLayoutView());

  LayoutRect backgroundRect(borderBoxRect());

  Color backgroundColor = resolveColor(CSSPropertyBackgroundColor);
  if (backgroundColor.alpha()) {
    paintedExtent = backgroundRect;
    return true;
  }

  if (!style()->backgroundLayers().image() ||
      style()->backgroundLayers().next()) {
    paintedExtent = backgroundRect;
    return true;
  }

  BackgroundImageGeometry geometry;
  // TODO(jchaffraix): This function should be rethought as it's called during
  // and outside of the paint phase. Potentially returning different results at
  // different phases.
  geometry.calculate(*this, nullptr, GlobalPaintNormalPhase,
                     style()->backgroundLayers(), backgroundRect);
  if (geometry.hasNonLocalGeometry())
    return false;
  paintedExtent = LayoutRect(geometry.destRect());
  return true;
}

bool LayoutBox::backgroundIsKnownToBeOpaqueInRect(
    const LayoutRect& localRect) const {
  if (isDocumentElement() || backgroundStolenForBeingBody())
    return false;

  // If the element has appearance, it might be painted by theme.
  // We cannot be sure if theme paints the background opaque.
  // In this case it is safe to not assume opaqueness.
  // FIXME: May be ask theme if it paints opaque.
  if (style()->hasAppearance())
    return false;
  // FIXME: Check the opaqueness of background images.

  // FIXME: Use rounded rect if border radius is present.
  if (style()->hasBorderRadius())
    return false;
  if (hasClipPath())
    return false;
  if (style()->hasBlendMode())
    return false;
  return backgroundRect(BackgroundKnownOpaqueRect).contains(localRect);
}

static bool isCandidateForOpaquenessTest(const LayoutBox& childBox) {
  const ComputedStyle& childStyle = childBox.styleRef();
  if (childStyle.position() != StaticPosition &&
      childBox.containingBlock() != childBox.parent())
    return false;
  if (childStyle.visibility() != EVisibility::Visible ||
      childStyle.shapeOutside())
    return false;
  if (childBox.size().isZero())
    return false;
  if (PaintLayer* childLayer = childBox.layer()) {
    // FIXME: perhaps this could be less conservative?
    if (childLayer->compositingState() != NotComposited)
      return false;
    // FIXME: Deal with z-index.
    if (childStyle.isStackingContext())
      return false;
    if (childLayer->hasTransformRelatedProperty() ||
        childLayer->isTransparent() || childLayer->hasFilterInducingProperty())
      return false;
    if (childBox.hasOverflowClip() && childStyle.hasBorderRadius())
      return false;
  }
  return true;
}

bool LayoutBox::foregroundIsKnownToBeOpaqueInRect(
    const LayoutRect& localRect,
    unsigned maxDepthToTest) const {
  if (!maxDepthToTest)
    return false;
  for (LayoutObject* child = slowFirstChild(); child;
       child = child->nextSibling()) {
    if (!child->isBox())
      continue;
    LayoutBox* childBox = toLayoutBox(child);
    if (!isCandidateForOpaquenessTest(*childBox))
      continue;
    LayoutPoint childLocation = childBox->location();
    if (childBox->isInFlowPositioned())
      childLocation.move(childBox->offsetForInFlowPosition());
    LayoutRect childLocalRect = localRect;
    childLocalRect.moveBy(-childLocation);
    if (childLocalRect.y() < 0 || childLocalRect.x() < 0) {
      // If there is unobscured area above/left of a static positioned box then
      // the rect is probably not covered.
      if (!childBox->isPositioned())
        return false;
      continue;
    }
    if (childLocalRect.maxY() > childBox->size().height() ||
        childLocalRect.maxX() > childBox->size().width())
      continue;
    if (childBox->backgroundIsKnownToBeOpaqueInRect(childLocalRect))
      return true;
    if (childBox->foregroundIsKnownToBeOpaqueInRect(childLocalRect,
                                                    maxDepthToTest - 1))
      return true;
  }
  return false;
}

DISABLE_CFI_PERF
bool LayoutBox::computeBackgroundIsKnownToBeObscured() const {
  if (scrollsOverflow())
    return false;
  // Test to see if the children trivially obscure the background.
  if (!styleRef().hasBackground())
    return false;
  // Root background painting is special.
  if (isLayoutView())
    return false;
  // FIXME: box-shadow is painted while background painting.
  if (style()->boxShadow())
    return false;
  LayoutRect backgroundRect;
  if (!getBackgroundPaintedExtent(backgroundRect))
    return false;
  return foregroundIsKnownToBeOpaqueInRect(backgroundRect,
                                           backgroundObscurationTestMaxDepth);
}

void LayoutBox::paintMask(const PaintInfo& paintInfo,
                          const LayoutPoint& paintOffset) const {
  BoxPainter(*this).paintMask(paintInfo, paintOffset);
}

void LayoutBox::imageChanged(WrappedImagePtr image, const IntRect*) {
  // TODO(chrishtr): support PaintInvalidationDelayedFull for animated border
  // images.
  if ((styleRef().borderImage().image() &&
       styleRef().borderImage().image()->data() == image) ||
      (styleRef().maskBoxImage().image() &&
       styleRef().maskBoxImage().image()->data() == image) ||
      (styleRef().boxReflect() && styleRef().boxReflect()->mask().image() &&
       styleRef().boxReflect()->mask().image()->data() == image)) {
    setShouldDoFullPaintInvalidation();
  } else {
    for (const FillLayer* layer = &styleRef().maskLayers(); layer;
         layer = layer->next()) {
      if (layer->image() && image == layer->image()->data()) {
        setShouldDoFullPaintInvalidation();
        break;
      }
    }
  }

  if (!isDocumentElement() && !backgroundStolenForBeingBody()) {
    for (const FillLayer* layer = &styleRef().backgroundLayers(); layer;
         layer = layer->next()) {
      if (layer->image() && image == layer->image()->data()) {
        invalidateBackgroundObscurationStatus();
        bool maybeAnimated =
            layer->image()->cachedImage() &&
            layer->image()->cachedImage()->getImage() &&
            layer->image()->cachedImage()->getImage()->maybeAnimated();
        if (maybeAnimated) {
          setMayNeedPaintInvalidationAnimatedBackgroundImage();
        } else {
          setShouldDoFullPaintInvalidation();
          setBackgroundChangedSinceLastPaintInvalidation();
        }
        break;
      }
    }
  }

  ShapeValue* shapeOutsideValue = style()->shapeOutside();
  if (!frameView()->isInPerformLayout() && isFloating() && shapeOutsideValue &&
      shapeOutsideValue->image() &&
      shapeOutsideValue->image()->data() == image) {
    ShapeOutsideInfo& info = ShapeOutsideInfo::ensureInfo(*this);
    if (!info.isComputingShape()) {
      info.markShapeAsDirty();
      markShapeOutsideDependentsForLayout();
    }
  }
}

ResourcePriority LayoutBox::computeResourcePriority() const {
  LayoutRect viewBounds = viewRect();
  LayoutRect objectBounds = LayoutRect(absoluteContentBox());

  // The object bounds might be empty right now, so intersects will fail since
  // it doesn't deal with empty rects. Use LayoutRect::contains in that case.
  bool isVisible;
  if (!objectBounds.isEmpty())
    isVisible = viewBounds.intersects(objectBounds);
  else
    isVisible = viewBounds.contains(objectBounds);

  LayoutRect screenRect;
  if (!objectBounds.isEmpty()) {
    screenRect = viewBounds;
    screenRect.intersect(objectBounds);
  }

  int screenArea = 0;
  if (!screenRect.isEmpty() && isVisible)
    screenArea = (screenRect.width() * screenRect.height()).toInt();
  return ResourcePriority(
      isVisible ? ResourcePriority::Visible : ResourcePriority::NotVisible,
      screenArea);
}

void LayoutBox::frameRectChanged() {
  if (node() && node()->isElementNode()) {
    Element& element = toElement(*node());
    element.setNeedsResizeObserverUpdate();
  }
  // The frame rect may change because of layout of other objects.
  // Should check this object for paint invalidation.
  if (!needsLayout())
    setMayNeedPaintInvalidation();

  // The overflow clip paint property depends on the border box rect through
  // overflowClipRect(). The border box rect's size equals the frame rect's
  // size, so we trigger a paint property update when the framerect changes.
  if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() &&
      shouldClipOverflow())
    setNeedsPaintPropertyUpdate();
}

bool LayoutBox::intersectsVisibleViewport() const {
  LayoutRect rect = visualOverflowRect();
  LayoutView* layoutView = view();
  while (!layoutView->frame()->ownerLayoutItem().isNull())
    layoutView =
        LayoutAPIShim::layoutObjectFrom(layoutView->frame()->ownerLayoutItem())
            ->view();
  mapToVisualRectInAncestorSpace(layoutView, rect);
  return rect.intersects(LayoutRect(
      layoutView->frameView()->getScrollableArea()->visibleContentRect()));
}

void LayoutBox::ensureIsReadyForPaintInvalidation() {
  LayoutBoxModelObject::ensureIsReadyForPaintInvalidation();

  if (mayNeedPaintInvalidationAnimatedBackgroundImage() &&
      !backgroundIsKnownToBeObscured())
    setShouldDoFullPaintInvalidation(PaintInvalidationDelayedFull);

  if (fullPaintInvalidationReason() != PaintInvalidationDelayedFull ||
      !intersectsVisibleViewport())
    return;

  // Do regular full paint invalidation if the object with
  // PaintInvalidationDelayedFull is onscreen.
  if (intersectsVisibleViewport()) {
    // Conservatively assume the delayed paint invalidation was caused by
    // background image change.
    setBackgroundChangedSinceLastPaintInvalidation();
    setShouldDoFullPaintInvalidation(PaintInvalidationFull);
  }
}

PaintInvalidationReason LayoutBox::invalidatePaintIfNeeded(
    const PaintInvalidationState& paintInvalidationState) {
  if (hasBoxDecorationBackground()
      // We also paint overflow controls in background phase.
      || (hasOverflowClip() && getScrollableArea()->hasOverflowControls())) {
    PaintLayer& layer = paintInvalidationState.paintingLayer();
    if (layer.layoutObject() != this)
      layer.setNeedsPaintPhaseDescendantBlockBackgrounds();
  }

  return LayoutBoxModelObject::invalidatePaintIfNeeded(paintInvalidationState);
}

PaintInvalidationReason LayoutBox::invalidatePaintIfNeeded(
    const PaintInvalidatorContext& context) const {
  return BoxPaintInvalidator(*this, context).invalidatePaintIfNeeded();
}

LayoutRect LayoutBox::overflowClipRect(
    const LayoutPoint& location,
    OverlayScrollbarClipBehavior overlayScrollbarClipBehavior) const {
  // FIXME: When overflow-clip (CSS3) is implemented, we'll obtain the property
  // here.
  LayoutRect clipRect = borderBoxRect();
  clipRect.setLocation(location + clipRect.location() +
                       LayoutSize(borderLeft(), borderTop()));
  clipRect.setSize(clipRect.size() - LayoutSize(borderLeft() + borderRight(),
                                                borderTop() + borderBottom()));

  if (hasOverflowClip())
    excludeScrollbars(clipRect, overlayScrollbarClipBehavior);
  return clipRect;
}

void LayoutBox::excludeScrollbars(
    LayoutRect& rect,
    OverlayScrollbarClipBehavior overlayScrollbarClipBehavior) const {
  if (PaintLayerScrollableArea* scrollableArea = this->getScrollableArea()) {
    if (shouldPlaceBlockDirectionScrollbarOnLogicalLeft()) {
      rect.move(
          scrollableArea->verticalScrollbarWidth(overlayScrollbarClipBehavior),
          0);
    }
    rect.contract(
        scrollableArea->verticalScrollbarWidth(overlayScrollbarClipBehavior),
        scrollableArea->horizontalScrollbarHeight(
            overlayScrollbarClipBehavior));
  }
}

LayoutRect LayoutBox::clipRect(const LayoutPoint& location) const {
  LayoutRect borderBoxRect = this->borderBoxRect();
  LayoutRect clipRect =
      LayoutRect(borderBoxRect.location() + location, borderBoxRect.size());

  if (!style()->clipLeft().isAuto()) {
    LayoutUnit c = valueForLength(style()->clipLeft(), borderBoxRect.width());
    clipRect.move(c, LayoutUnit());
    clipRect.contract(c, LayoutUnit());
  }

  if (!style()->clipRight().isAuto())
    clipRect.contract(
        size().width() - valueForLength(style()->clipRight(), size().width()),
        LayoutUnit());

  if (!style()->clipTop().isAuto()) {
    LayoutUnit c = valueForLength(style()->clipTop(), borderBoxRect.height());
    clipRect.move(LayoutUnit(), c);
    clipRect.contract(LayoutUnit(), c);
  }

  if (!style()->clipBottom().isAuto())
    clipRect.contract(LayoutUnit(),
                      size().height() - valueForLength(style()->clipBottom(),
                                                       size().height()));

  return clipRect;
}

static LayoutUnit portionOfMarginNotConsumedByFloat(LayoutUnit childMargin,
                                                    LayoutUnit contentSide,
                                                    LayoutUnit offset) {
  if (childMargin <= 0)
    return LayoutUnit();
  LayoutUnit contentSideWithMargin = contentSide + childMargin;
  if (offset > contentSideWithMargin)
    return childMargin;
  return offset - contentSide;
}

LayoutUnit LayoutBox::shrinkLogicalWidthToAvoidFloats(
    LayoutUnit childMarginStart,
    LayoutUnit childMarginEnd,
    const LayoutBlockFlow* cb) const {
  LayoutUnit logicalTopPosition = logicalTop();
  LayoutUnit startOffsetForContent = cb->startOffsetForContent();
  LayoutUnit endOffsetForContent = cb->endOffsetForContent();
  LayoutUnit logicalHeight = cb->logicalHeightForChild(*this);
  LayoutUnit startOffsetForLine = cb->startOffsetForLine(
      logicalTopPosition, DoNotIndentText, logicalHeight);
  LayoutUnit endOffsetForLine =
      cb->endOffsetForLine(logicalTopPosition, DoNotIndentText, logicalHeight);

  // If there aren't any floats constraining us then allow the margins to
  // shrink/expand the width as much as they want.
  if (startOffsetForContent == startOffsetForLine &&
      endOffsetForContent == endOffsetForLine)
    return cb->availableLogicalWidthForLine(logicalTopPosition, DoNotIndentText,
                                            logicalHeight) -
           childMarginStart - childMarginEnd;

  LayoutUnit width = cb->availableLogicalWidthForLine(
                         logicalTopPosition, DoNotIndentText, logicalHeight) -
                     std::max(LayoutUnit(), childMarginStart) -
                     std::max(LayoutUnit(), childMarginEnd);
  // We need to see if margins on either the start side or the end side can
  // contain the floats in question. If they can, then just using the line width
  // is inaccurate. In the case where a float completely fits, we don't need to
  // use the line offset at all, but can instead push all the way to the content
  // edge of the containing block. In the case where the float doesn't fit, we
  // can use the line offset, but we need to grow it by the margin to reflect
  // the fact that the margin was "consumed" by the float. Negative margins
  // aren't consumed by the float, and so we ignore them.
  width += portionOfMarginNotConsumedByFloat(
      childMarginStart, startOffsetForContent, startOffsetForLine);
  width += portionOfMarginNotConsumedByFloat(
      childMarginEnd, endOffsetForContent, endOffsetForLine);
  return width;
}

LayoutUnit LayoutBox::containingBlockLogicalHeightForGetComputedStyle() const {
  if (hasOverrideContainingBlockLogicalHeight())
    return overrideContainingBlockContentLogicalHeight();

  if (!isPositioned())
    return containingBlockLogicalHeightForContent(ExcludeMarginBorderPadding);

  LayoutBoxModelObject* cb = toLayoutBoxModelObject(container());
  LayoutUnit height = containingBlockLogicalHeightForPositioned(cb);
  if (styleRef().position() != AbsolutePosition)
    height -= cb->paddingLogicalHeight();
  return height;
}

LayoutUnit LayoutBox::containingBlockLogicalWidthForContent() const {
  if (hasOverrideContainingBlockLogicalWidth())
    return overrideContainingBlockContentLogicalWidth();

  LayoutBlock* cb = containingBlock();
  if (isOutOfFlowPositioned())
    return cb->clientLogicalWidth();
  return cb->availableLogicalWidth();
}

LayoutUnit LayoutBox::containingBlockLogicalHeightForContent(
    AvailableLogicalHeightType heightType) const {
  if (hasOverrideContainingBlockLogicalHeight())
    return overrideContainingBlockContentLogicalHeight();

  LayoutBlock* cb = containingBlock();
  return cb->availableLogicalHeight(heightType);
}

LayoutUnit LayoutBox::containingBlockAvailableLineWidth() const {
  LayoutBlock* cb = containingBlock();
  if (cb->isLayoutBlockFlow())
    return toLayoutBlockFlow(cb)->availableLogicalWidthForLine(
        logicalTop(), DoNotIndentText,
        availableLogicalHeight(IncludeMarginBorderPadding));
  return LayoutUnit();
}

LayoutUnit LayoutBox::perpendicularContainingBlockLogicalHeight() const {
  if (hasOverrideContainingBlockLogicalHeight())
    return overrideContainingBlockContentLogicalHeight();

  LayoutBlock* cb = containingBlock();
  if (cb->hasOverrideLogicalContentHeight())
    return cb->overrideLogicalContentHeight();

  const ComputedStyle& containingBlockStyle = cb->styleRef();
  Length logicalHeightLength = containingBlockStyle.logicalHeight();

  // FIXME: For now just support fixed heights.  Eventually should support
  // percentage heights as well.
  if (!logicalHeightLength.isFixed()) {
    LayoutUnit fillFallbackExtent =
        LayoutUnit(containingBlockStyle.isHorizontalWritingMode()
                       ? view()->frameView()->visibleContentSize().height()
                       : view()->frameView()->visibleContentSize().width());
    LayoutUnit fillAvailableExtent =
        containingBlock()->availableLogicalHeight(ExcludeMarginBorderPadding);
    if (fillAvailableExtent == -1)
      return fillFallbackExtent;
    return std::min(fillAvailableExtent, fillFallbackExtent);
  }

  // Use the content box logical height as specified by the style.
  return cb->adjustContentBoxLogicalHeightForBoxSizing(
      LayoutUnit(logicalHeightLength.value()));
}

void LayoutBox::mapLocalToAncestor(const LayoutBoxModelObject* ancestor,
                                   TransformState& transformState,
                                   MapCoordinatesFlags mode) const {
  bool isFixedPos = style()->position() == FixedPosition;

  // If this box has a transform or contains paint, it acts as a fixed position
  // container for fixed descendants, and may itself also be fixed position. So
  // propagate 'fixed' up only if this box is fixed position.
  if (style()->canContainFixedPositionObjects() && !isFixedPos)
    mode &= ~IsFixed;
  else if (isFixedPos)
    mode |= IsFixed;

  LayoutBoxModelObject::mapLocalToAncestor(ancestor, transformState, mode);
}

void LayoutBox::mapAncestorToLocal(const LayoutBoxModelObject* ancestor,
                                   TransformState& transformState,
                                   MapCoordinatesFlags mode) const {
  if (this == ancestor)
    return;

  bool isFixedPos = style()->position() == FixedPosition;

  // If this box has a transform or contains paint, it acts as a fixed position
  // container for fixed descendants, and may itself also be fixed position. So
  // propagate 'fixed' up only if this box is fixed position.
  if (style()->canContainFixedPositionObjects() && !isFixedPos)
    mode &= ~IsFixed;
  else if (isFixedPos)
    mode |= IsFixed;

  LayoutBoxModelObject::mapAncestorToLocal(ancestor, transformState, mode);
}

LayoutSize LayoutBox::offsetFromContainer(const LayoutObject* o) const {
  ASSERT(o == container());

  LayoutSize offset;
  if (isInFlowPositioned())
    offset += offsetForInFlowPosition();

  offset += physicalLocationOffset();

  if (o->hasOverflowClip())
    offset -= toLayoutBox(o)->scrolledContentOffset();

  if (style()->position() == AbsolutePosition && o->isInFlowPositioned() &&
      o->isLayoutInline())
    offset += toLayoutInline(o)->offsetForInFlowPositionedInline(*this);

  return offset;
}

InlineBox* LayoutBox::createInlineBox() {
  return new InlineBox(LineLayoutItem(this));
}

void LayoutBox::dirtyLineBoxes(bool fullLayout) {
  if (m_inlineBoxWrapper) {
    if (fullLayout) {
      m_inlineBoxWrapper->destroy();
      m_inlineBoxWrapper = nullptr;
    } else {
      m_inlineBoxWrapper->dirtyLineBoxes();
    }
  }
}

void LayoutBox::positionLineBox(InlineBox* box) {
  if (isOutOfFlowPositioned()) {
    // Cache the x position only if we were an INLINE type originally.
    bool originallyInline = style()->isOriginalDisplayInlineType();
    if (originallyInline) {
      // The value is cached in the xPos of the box.  We only need this value if
      // our object was inline originally, since otherwise it would have ended
      // up underneath the inlines.
      RootInlineBox& root = box->root();
      root.block().setStaticInlinePositionForChild(LineLayoutBox(this),
                                                   box->logicalLeft());
    } else {
      // Our object was a block originally, so we make our normal flow position
      // be just below the line box (as though all the inlines that came before
      // us got wrapped in an anonymous block, which is what would have happened
      // had we been in flow). This value was cached in the y() of the box.
      layer()->setStaticBlockPosition(box->logicalTop());
    }

    if (container()->isLayoutInline())
      moveWithEdgeOfInlineContainerIfNecessary(box->isHorizontal());

    // Nuke the box.
    box->remove(DontMarkLineBoxes);
    box->destroy();
  } else if (isAtomicInlineLevel()) {
    setLocationAndUpdateOverflowControlsIfNeeded(box->location());
    setInlineBoxWrapper(box);
  }
}

void LayoutBox::moveWithEdgeOfInlineContainerIfNecessary(bool isHorizontal) {
  ASSERT(isOutOfFlowPositioned() && container()->isLayoutInline() &&
         container()->isInFlowPositioned());
  // If this object is inside a relative positioned inline and its inline
  // position is an explicit offset from the edge of its container then it will
  // need to move if its inline container has changed width. We do not track if
  // the width has changed but if we are here then we are laying out lines
  // inside it, so it probably has - mark our object for layout so that it can
  // move to the new offset created by the new width.
  if (!normalChildNeedsLayout() &&
      !style()->hasStaticInlinePosition(isHorizontal))
    setChildNeedsLayout(MarkOnlyThis);
}

void LayoutBox::deleteLineBoxWrapper() {
  if (m_inlineBoxWrapper) {
    if (!documentBeingDestroyed())
      m_inlineBoxWrapper->remove();
    m_inlineBoxWrapper->destroy();
    m_inlineBoxWrapper = nullptr;
  }
}

void LayoutBox::setSpannerPlaceholder(
    LayoutMultiColumnSpannerPlaceholder& placeholder) {
  // Not expected to change directly from one spanner to another.
  RELEASE_ASSERT(!m_rareData || !m_rareData->m_spannerPlaceholder);
  ensureRareData().m_spannerPlaceholder = &placeholder;
}

void LayoutBox::clearSpannerPlaceholder() {
  if (!m_rareData)
    return;
  m_rareData->m_spannerPlaceholder = nullptr;
}

void LayoutBox::setPaginationStrut(LayoutUnit strut) {
  if (!strut && !m_rareData)
    return;
  ensureRareData().m_paginationStrut = strut;
}

bool LayoutBox::isBreakBetweenControllable(EBreak breakValue) const {
  if (breakValue == BreakAuto)
    return true;
  // We currently only support non-auto break-before and break-after values on
  // in-flow block level elements, which is the minimum requirement according to
  // the spec.
  if (isInline() || isFloatingOrOutOfFlowPositioned())
    return false;
  const LayoutBlock* curr = containingBlock();
  if (!curr || !curr->isLayoutBlockFlow())
    return false;
  const LayoutView* layoutView = view();
  bool viewIsPaginated = layoutView->fragmentationContext();
  if (!viewIsPaginated && !flowThreadContainingBlock())
    return false;
  while (curr) {
    if (curr == layoutView)
      return viewIsPaginated && breakValue != BreakColumn &&
             breakValue != BreakAvoidColumn;
    if (curr->isLayoutFlowThread()) {
      if (breakValue ==
          BreakAvoid)  // Valid in any kind of fragmentation context.
        return true;
      bool isMulticolValue =
          breakValue == BreakColumn || breakValue == BreakAvoidColumn;
      if (toLayoutFlowThread(curr)->isLayoutPagedFlowThread())
        return !isMulticolValue;
      if (isMulticolValue)
        return true;
      // If this is a flow thread for a multicol container, and we have a break
      // value for paged, we need to keep looking.
    }
    if (curr->isFloatingOrOutOfFlowPositioned())
      return false;
    curr = curr->containingBlock();
  }
  ASSERT_NOT_REACHED();
  return false;
}

bool LayoutBox::isBreakInsideControllable(EBreak breakValue) const {
  ASSERT(!isForcedFragmentainerBreakValue(breakValue));
  if (breakValue == BreakAuto)
    return true;
  // First check multicol.
  const LayoutFlowThread* flowThread = flowThreadContainingBlock();
  // 'avoid-column' is only valid in a multicol context.
  if (breakValue == BreakAvoidColumn)
    return flowThread && !flowThread->isLayoutPagedFlowThread();
  // 'avoid' is valid in any kind of fragmentation context.
  if (breakValue == BreakAvoid && flowThread)
    return true;
  ASSERT(breakValue == BreakAvoidPage || breakValue == BreakAvoid);
  if (view()->fragmentationContext())
    return true;  // The view is paginated, probably because we're printing.
  if (!flowThread)
    return false;  // We're not inside any pagination context
  // We're inside a flow thread. We need to be contained by a flow thread for
  // paged overflow in order for pagination values to be valid, though.
  for (const LayoutBlock* ancestor = flowThread; ancestor;
       ancestor = ancestor->containingBlock()) {
    if (ancestor->isLayoutFlowThread() &&
        toLayoutFlowThread(ancestor)->isLayoutPagedFlowThread())
      return true;
  }
  return false;
}

EBreak LayoutBox::breakAfter() const {
  EBreak breakValue = style()->breakAfter();
  if (breakValue == BreakAuto || isBreakBetweenControllable(breakValue))
    return breakValue;
  return BreakAuto;
}

EBreak LayoutBox::breakBefore() const {
  EBreak breakValue = style()->breakBefore();
  if (breakValue == BreakAuto || isBreakBetweenControllable(breakValue))
    return breakValue;
  return BreakAuto;
}

EBreak LayoutBox::breakInside() const {
  EBreak breakValue = style()->breakInside();
  if (breakValue == BreakAuto || isBreakInsideControllable(breakValue))
    return breakValue;
  return BreakAuto;
}

// At a class A break point [1], the break value with the highest precedence
// wins. If the two values have the same precedence (e.g. "left" and "right"),
// the value specified on a latter object wins.
//
// [1] https://drafts.csswg.org/css-break/#possible-breaks
static inline int fragmentainerBreakPrecedence(EBreak breakValue) {
  // "auto" has the lowest priority.
  // "avoid*" values win over "auto".
  // "avoid-page" wins over "avoid-column".
  // "avoid" wins over "avoid-page".
  // Forced break values win over "avoid".
  // Any forced page break value wins over "column" forced break.
  // More specific break values (left, right, recto, verso) wins over generic
  // "page" values.

  switch (breakValue) {
    default:
      ASSERT_NOT_REACHED();
    // fall-through
    case BreakAuto:
      return 0;
    case BreakAvoidColumn:
      return 1;
    case BreakAvoidPage:
      return 2;
    case BreakAvoid:
      return 3;
    case BreakColumn:
      return 4;
    case BreakPage:
      return 5;
    case BreakLeft:
    case BreakRight:
    case BreakRecto:
    case BreakVerso:
      return 6;
  }
}

EBreak LayoutBox::joinFragmentainerBreakValues(EBreak firstValue,
                                               EBreak secondValue) {
  if (fragmentainerBreakPrecedence(secondValue) >=
      fragmentainerBreakPrecedence(firstValue))
    return secondValue;
  return firstValue;
}

EBreak LayoutBox::classABreakPointValue(EBreak previousBreakAfterValue) const {
  // First assert that we're at a class A break point.
  ASSERT(isBreakBetweenControllable(previousBreakAfterValue));

  return joinFragmentainerBreakValues(previousBreakAfterValue, breakBefore());
}

bool LayoutBox::needsForcedBreakBefore(EBreak previousBreakAfterValue) const {
  // Forced break values are only honored when specified on in-flow objects, but
  // floats and out-of-flow positioned objects may be affected by a break-after
  // value of the previous in-flow object, even though we're not at a class A
  // break point.
  EBreak breakValue = isFloatingOrOutOfFlowPositioned()
                          ? previousBreakAfterValue
                          : classABreakPointValue(previousBreakAfterValue);
  return isForcedFragmentainerBreakValue(breakValue);
}

bool LayoutBox::paintedOutputOfObjectHasNoEffectRegardlessOfSize() const {
  if (hasNonCompositedScrollbars() || getSelectionState() != SelectionNone ||
      hasBoxDecorationBackground() || styleRef().hasBoxDecorations() ||
      styleRef().hasVisualOverflowingEffect())
    return false;

  // If the box has clip or mask, we need issue paint invalidation to cover
  // the changed part of children when the box got resized. In SPv2 this is
  // handled by detecting paint property changes.
  if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
    if (hasClipRelatedProperty() || hasControlClip() || hasMask())
      return false;
  }

  return true;
}

LayoutRect LayoutBox::localVisualRect() const {
  if (style()->visibility() != EVisibility::Visible)
    return LayoutRect();

  if (hasMask() && !RuntimeEnabledFeatures::slimmingPaintV2Enabled())
    return LayoutRect(layer()->boxForFilterOrMask());
  return selfVisualOverflowRect();
}

void LayoutBox::inflateVisualRectForFilterUnderContainer(
    LayoutRect& rect,
    const LayoutObject& container,
    const LayoutBoxModelObject* ancestorToStopAt) const {
  // Apply visual overflow caused by reflections and filters defined on objects
  // between this object and container (not included) or ancestorToStopAt
  // (included).
  LayoutSize offsetFromContainer = this->offsetFromContainer(&container);
  rect.move(offsetFromContainer);
  for (LayoutObject* parent = this->parent(); parent && parent != container;
       parent = parent->parent()) {
    if (parent->isBox()) {
      // Convert rect into coordinate space of parent to apply parent's
      // reflection and filter.
      LayoutSize parentOffset = parent->offsetFromAncestorContainer(&container);
      rect.move(-parentOffset);
      toLayoutBox(parent)->inflateVisualRectForFilter(rect);
      rect.move(parentOffset);
    }
    if (parent == ancestorToStopAt)
      break;
  }
  rect.move(-offsetFromContainer);
}

bool LayoutBox::mapToVisualRectInAncestorSpace(
    const LayoutBoxModelObject* ancestor,
    LayoutRect& rect,
    VisualRectFlags visualRectFlags) const {
  inflateVisualRectForFilter(rect);

  if (ancestor == this)
    return true;

  bool ancestorSkipped;
  bool filterSkipped;
  LayoutObject* container =
      this->container(ancestor, &ancestorSkipped, &filterSkipped);
  LayoutBox* tableRowContainer = nullptr;
  // Skip table row because cells and rows are in the same coordinate space (see
  // below, however for more comments about when |ancestor| is the table row).
  if (isTableCell()) {
    DCHECK(container->isTableRow() && parentBox() == container);
    if (container != ancestor)
      container = container->parent();
    else
      tableRowContainer = toLayoutBox(container);
  }
  if (!container)
    return true;

  if (filterSkipped)
    inflateVisualRectForFilterUnderContainer(rect, *container, ancestor);

  // We are now in our parent container's coordinate space. Apply our transform
  // to obtain a bounding box in the parent's coordinate space that encloses us.
  if (hasLayer() && layer()->transform()) {
    // Use enclosingIntRect because we cannot properly compute pixel snapping
    // for painted elements within the transform since we don't know the desired
    // subpixel accumulation at this point, and the transform may include a
    // scale.
    rect = LayoutRect(layer()->transform()->mapRect(enclosingIntRect(rect)));
  }
  LayoutPoint topLeft = rect.location();
  if (container->isBox()) {
    topLeft.moveBy(physicalLocation(toLayoutBox(container)));
    // If the row is the ancestor, however, add its offset back in. In effect,
    // this passes from the joint <td> / <tr> coordinate space to the parent
    // space, then back to <tr> / <td>.
    if (tableRowContainer) {
      topLeft.moveBy(
          -tableRowContainer->physicalLocation(toLayoutBox(container)));
    }
  } else if (container->isRuby()) {
    // TODO(wkorman): Generalize Ruby specialization and/or document more
    // clearly. See the accompanying specialization in
    // LayoutInline::mapToVisualRectInAncestorSpace.
    topLeft.moveBy(physicalLocation());
  } else {
    topLeft.moveBy(location());
  }

  const ComputedStyle& styleToUse = styleRef();
  EPosition position = styleToUse.position();
  if (position == AbsolutePosition && container->isInFlowPositioned() &&
      container->isLayoutInline()) {
    topLeft +=
        toLayoutInline(container)->offsetForInFlowPositionedInline(*this);
  } else if (styleToUse.hasInFlowPosition() && layer()) {
    // Apply the relative position offset when invalidating a rectangle. The
    // layer is translated, but the layout box isn't, so we need to do this to
    // get the right dirty rect.  Since this is called from
    // LayoutObject::setStyle, the relative position flag on the LayoutObject
    // has been cleared, so use the one on the style().
    topLeft += layer()->offsetForInFlowPosition();
  }

  // FIXME: We ignore the lightweight clipping rect that controls use, since if
  // |o| is in mid-layout, its controlClipRect will be wrong. For overflow clip
  // we use the values cached by the layer.
  rect.setLocation(topLeft);

  if (container->isBox() && container != ancestor &&
      !toLayoutBox(container)->mapScrollingContentsRectToBoxSpace(
          rect, visualRectFlags))
    return false;

  if (ancestorSkipped) {
    // If the ancestor is below the container, then we need to map the rect into
    // ancestor's coordinates.
    LayoutSize containerOffset =
        ancestor->offsetFromAncestorContainer(container);
    rect.move(-containerOffset);
    // If the ancestor is fixed, then the rect is already in its coordinates so
    // doesn't need viewport-adjusting.
    if (ancestor->style()->position() != FixedPosition &&
        container->isLayoutView() && position == FixedPosition)
      rect.move(toLayoutView(container)->offsetForFixedPosition(true));
    return true;
  }

  if (container->isLayoutView())
    return toLayoutView(container)->mapToVisualRectInAncestorSpace(
        ancestor, rect, position == FixedPosition ? IsFixed : 0,
        visualRectFlags);
  else
    return container->mapToVisualRectInAncestorSpace(ancestor, rect,
                                                     visualRectFlags);
}

void LayoutBox::inflateVisualRectForFilter(LayoutRect& visualRect) const {
  if (layer() && layer()->hasFilterInducingProperty())
    visualRect = layer()->mapLayoutRectForFilter(visualRect);
}

void LayoutBox::updateLogicalWidth() {
  LogicalExtentComputedValues computedValues;
  computeLogicalWidth(computedValues);

  setLogicalWidth(computedValues.m_extent);
  setLogicalLeft(computedValues.m_position);
  setMarginStart(computedValues.m_margins.m_start);
  setMarginEnd(computedValues.m_margins.m_end);
}

static float getMaxWidthListMarker(const LayoutBox* layoutObject) {
#if ENABLE(ASSERT)
  ASSERT(layoutObject);
  Node* parentNode = layoutObject->generatingNode();
  ASSERT(parentNode);
  ASSERT(isHTMLOListElement(parentNode) || isHTMLUListElement(parentNode));
  ASSERT(layoutObject->style()->textAutosizingMultiplier() != 1);
#endif
  float maxWidth = 0;
  for (LayoutObject* child = layoutObject->slowFirstChild(); child;
       child = child->nextSibling()) {
    if (!child->isListItem())
      continue;

    LayoutBox* listItem = toLayoutBox(child);
    for (LayoutObject* itemChild = listItem->slowFirstChild(); itemChild;
         itemChild = itemChild->nextSibling()) {
      if (!itemChild->isListMarker())
        continue;
      LayoutBox* itemMarker = toLayoutBox(itemChild);
      // Make sure to compute the autosized width.
      if (itemMarker->needsLayout())
        itemMarker->layout();
      maxWidth = std::max<float>(
          maxWidth, toLayoutListMarker(itemMarker)->logicalWidth().toFloat());
      break;
    }
  }
  return maxWidth;
}

DISABLE_CFI_PERF
void LayoutBox::computeLogicalWidth(
    LogicalExtentComputedValues& computedValues) const {
  computedValues.m_extent =
      style()->containsSize() ? borderAndPaddingLogicalWidth() : logicalWidth();
  computedValues.m_position = logicalLeft();
  computedValues.m_margins.m_start = marginStart();
  computedValues.m_margins.m_end = marginEnd();

  if (isOutOfFlowPositioned()) {
    computePositionedLogicalWidth(computedValues);
    return;
  }

  // The parent box is flexing us, so it has increased or decreased our
  // width.  Use the width from the style context.
  // FIXME: Account for writing-mode in flexible boxes.
  // https://bugs.webkit.org/show_bug.cgi?id=46418
  if (hasOverrideLogicalContentWidth() &&
      parent()->isFlexibleBoxIncludingDeprecated()) {
    computedValues.m_extent =
        overrideLogicalContentWidth() + borderAndPaddingLogicalWidth();
    return;
  }

  // FIXME: Account for writing-mode in flexible boxes.
  // https://bugs.webkit.org/show_bug.cgi?id=46418
  bool inVerticalBox = parent()->isDeprecatedFlexibleBox() &&
                       (parent()->style()->boxOrient() == VERTICAL);
  bool stretching = (parent()->style()->boxAlign() == BSTRETCH);
  // TODO (lajava): Stretching is the only reason why we don't want the box to
  // be treated as a replaced element, so we could perhaps refactor all this
  // logic, not only for flex and grid since alignment is intended to be applied
  // to any block.
  bool treatAsReplaced = shouldComputeSizeAsReplaced() &&
                         (!inVerticalBox || !stretching) &&
                         (!isGridItem() || !hasStretchedLogicalWidth());
  const ComputedStyle& styleToUse = styleRef();
  Length logicalWidthLength = treatAsReplaced
                                  ? Length(computeReplacedLogicalWidth(), Fixed)
                                  : styleToUse.logicalWidth();

  LayoutBlock* cb = containingBlock();
  LayoutUnit containerLogicalWidth =
      std::max(LayoutUnit(), containingBlockLogicalWidthForContent());
  bool hasPerpendicularContainingBlock =
      cb->isHorizontalWritingMode() != isHorizontalWritingMode();

  if (isInline() && !isInlineBlockOrInlineTable()) {
    // just calculate margins
    computedValues.m_margins.m_start =
        minimumValueForLength(styleToUse.marginStart(), containerLogicalWidth);
    computedValues.m_margins.m_end =
        minimumValueForLength(styleToUse.marginEnd(), containerLogicalWidth);
    if (treatAsReplaced)
      computedValues.m_extent =
          std::max(LayoutUnit(floatValueForLength(logicalWidthLength, 0)) +
                       borderAndPaddingLogicalWidth(),
                   minPreferredLogicalWidth());
    return;
  }

  LayoutUnit containerWidthInInlineDirection = containerLogicalWidth;
  if (hasPerpendicularContainingBlock)
    containerWidthInInlineDirection =
        perpendicularContainingBlockLogicalHeight();

  // Width calculations
  if (treatAsReplaced) {
    computedValues.m_extent =
        LayoutUnit(logicalWidthLength.value()) + borderAndPaddingLogicalWidth();
  } else {
    LayoutUnit preferredWidth =
        computeLogicalWidthUsing(MainOrPreferredSize, styleToUse.logicalWidth(),
                                 containerWidthInInlineDirection, cb);
    computedValues.m_extent = constrainLogicalWidthByMinMax(
        preferredWidth, containerWidthInInlineDirection, cb);
  }

  // Margin calculations.
  computeMarginsForDirection(
      InlineDirection, cb, containerLogicalWidth, computedValues.m_extent,
      computedValues.m_margins.m_start, computedValues.m_margins.m_end,
      style()->marginStart(), style()->marginEnd());

  if (!hasPerpendicularContainingBlock && containerLogicalWidth &&
      containerLogicalWidth !=
          (computedValues.m_extent + computedValues.m_margins.m_start +
           computedValues.m_margins.m_end) &&
      !isFloating() && !isInline() && !cb->isFlexibleBoxIncludingDeprecated() &&
      !cb->isLayoutGrid()) {
    LayoutUnit newMargin = containerLogicalWidth - computedValues.m_extent -
                           cb->marginStartForChild(*this);
    bool hasInvertedDirection = cb->style()->isLeftToRightDirection() !=
                                style()->isLeftToRightDirection();
    if (hasInvertedDirection)
      computedValues.m_margins.m_start = newMargin;
    else
      computedValues.m_margins.m_end = newMargin;
  }

  if (styleToUse.textAutosizingMultiplier() != 1 &&
      styleToUse.marginStart().type() == Fixed) {
    Node* parentNode = generatingNode();
    if (parentNode &&
        (isHTMLOListElement(*parentNode) || isHTMLUListElement(*parentNode))) {
      // Make sure the markers in a list are properly positioned (i.e. not
      // chopped off) when autosized.
      const float adjustedMargin =
          (1 - 1.0 / styleToUse.textAutosizingMultiplier()) *
          getMaxWidthListMarker(this);
      bool hasInvertedDirection = cb->style()->isLeftToRightDirection() !=
                                  style()->isLeftToRightDirection();
      if (hasInvertedDirection)
        computedValues.m_margins.m_end += adjustedMargin;
      else
        computedValues.m_margins.m_start += adjustedMargin;
    }
  }
}

LayoutUnit LayoutBox::fillAvailableMeasure(
    LayoutUnit availableLogicalWidth) const {
  LayoutUnit marginStart;
  LayoutUnit marginEnd;
  return fillAvailableMeasure(availableLogicalWidth, marginStart, marginEnd);
}

LayoutUnit LayoutBox::fillAvailableMeasure(LayoutUnit availableLogicalWidth,
                                           LayoutUnit& marginStart,
                                           LayoutUnit& marginEnd) const {
  ASSERT(availableLogicalWidth >= 0);
  marginStart =
      minimumValueForLength(style()->marginStart(), availableLogicalWidth);
  marginEnd =
      minimumValueForLength(style()->marginEnd(), availableLogicalWidth);
  LayoutUnit available = availableLogicalWidth - marginStart - marginEnd;
  available = std::max(available, LayoutUnit());
  return available;
}

DISABLE_CFI_PERF
LayoutUnit LayoutBox::computeIntrinsicLogicalWidthUsing(
    const Length& logicalWidthLength,
    LayoutUnit availableLogicalWidth,
    LayoutUnit borderAndPadding) const {
  if (logicalWidthLength.type() == FillAvailable)
    return std::max(borderAndPadding,
                    fillAvailableMeasure(availableLogicalWidth));

  LayoutUnit minLogicalWidth;
  LayoutUnit maxLogicalWidth;
  computeIntrinsicLogicalWidths(minLogicalWidth, maxLogicalWidth);

  if (logicalWidthLength.type() == MinContent)
    return minLogicalWidth + borderAndPadding;

  if (logicalWidthLength.type() == MaxContent)
    return maxLogicalWidth + borderAndPadding;

  if (logicalWidthLength.type() == FitContent) {
    minLogicalWidth += borderAndPadding;
    maxLogicalWidth += borderAndPadding;
    return std::max(
        minLogicalWidth,
        std::min(maxLogicalWidth, fillAvailableMeasure(availableLogicalWidth)));
  }

  ASSERT_NOT_REACHED();
  return LayoutUnit();
}

DISABLE_CFI_PERF
LayoutUnit LayoutBox::computeLogicalWidthUsing(SizeType widthType,
                                               const Length& logicalWidth,
                                               LayoutUnit availableLogicalWidth,
                                               const LayoutBlock* cb) const {
  ASSERT(widthType == MinSize || widthType == MainOrPreferredSize ||
         !logicalWidth.isAuto());
  if (widthType == MinSize && logicalWidth.isAuto())
    return adjustBorderBoxLogicalWidthForBoxSizing(0);

  if (!logicalWidth.isIntrinsicOrAuto()) {
    // FIXME: If the containing block flow is perpendicular to our direction we
    // need to use the available logical height instead.
    return adjustBorderBoxLogicalWidthForBoxSizing(
        valueForLength(logicalWidth, availableLogicalWidth));
  }

  if (logicalWidth.isIntrinsic())
    return computeIntrinsicLogicalWidthUsing(
        logicalWidth, availableLogicalWidth, borderAndPaddingLogicalWidth());

  LayoutUnit marginStart;
  LayoutUnit marginEnd;
  LayoutUnit logicalWidthResult =
      fillAvailableMeasure(availableLogicalWidth, marginStart, marginEnd);

  if (shrinkToAvoidFloats() && cb->isLayoutBlockFlow() &&
      toLayoutBlockFlow(cb)->containsFloats())
    logicalWidthResult = std::min(
        logicalWidthResult, shrinkLogicalWidthToAvoidFloats(
                                marginStart, marginEnd, toLayoutBlockFlow(cb)));

  if (widthType == MainOrPreferredSize &&
      sizesLogicalWidthToFitContent(logicalWidth))
    return std::max(minPreferredLogicalWidth(),
                    std::min(maxPreferredLogicalWidth(), logicalWidthResult));
  return logicalWidthResult;
}

bool LayoutBox::columnFlexItemHasStretchAlignment() const {
  // auto margins mean we don't stretch. Note that this function will only be
  // used for widths, so we don't have to check marginBefore/marginAfter.
  const auto& parentStyle = parent()->styleRef();
  DCHECK(parentStyle.isColumnFlexDirection());
  if (styleRef().marginStart().isAuto() || styleRef().marginEnd().isAuto())
    return false;
  return styleRef()
             .resolvedAlignSelf(
                 containingBlock()->selfAlignmentNormalBehavior(),
                 isAnonymous() ? &parentStyle : nullptr)
             .position() == ItemPositionStretch;
}

bool LayoutBox::isStretchingColumnFlexItem() const {
  LayoutObject* parent = this->parent();
  if (parent->isDeprecatedFlexibleBox() &&
      parent->style()->boxOrient() == VERTICAL &&
      parent->style()->boxAlign() == BSTRETCH)
    return true;

  // We don't stretch multiline flexboxes because they need to apply line
  // spacing (align-content) first.
  if (parent->isFlexibleBox() && parent->style()->flexWrap() == FlexNoWrap &&
      parent->style()->isColumnFlexDirection() &&
      columnFlexItemHasStretchAlignment())
    return true;
  return false;
}

// TODO (lajava) Can/Should we move this inside specific layout classes (flex.
// grid)? Can we refactor columnFlexItemHasStretchAlignment logic?
bool LayoutBox::hasStretchedLogicalWidth() const {
  const ComputedStyle& style = styleRef();
  if (!style.logicalWidth().isAuto() || style.marginStart().isAuto() ||
      style.marginEnd().isAuto())
    return false;
  LayoutBlock* cb = containingBlock();
  if (!cb) {
    // We are evaluating align-self/justify-self, which default to 'normal' for
    // the root element. The 'normal' value behaves like 'start' except for
    // Flexbox Items, which obviously should have a container.
    return false;
  }
  const ComputedStyle* parentStyle = isAnonymous() ? cb->style() : nullptr;
  if (cb->isHorizontalWritingMode() != isHorizontalWritingMode())
    return style
               .resolvedAlignSelf(cb->selfAlignmentNormalBehavior(),
                                  parentStyle)
               .position() == ItemPositionStretch;
  return style
             .resolvedJustifySelf(cb->selfAlignmentNormalBehavior(),
                                  parentStyle)
             .position() == ItemPositionStretch;
}

bool LayoutBox::sizesLogicalWidthToFitContent(
    const Length& logicalWidth) const {
  if (isFloating() || isInlineBlockOrInlineTable())
    return true;

  if (isGridItem())
    return !hasStretchedLogicalWidth();

  // Flexible box items should shrink wrap, so we lay them out at their
  // intrinsic widths. In the case of columns that have a stretch alignment, we
  // go ahead and layout at the stretched size to avoid an extra layout when
  // applying alignment.
  if (parent()->isFlexibleBox()) {
    // For multiline columns, we need to apply align-content first, so we can't
    // stretch now.
    if (!parent()->style()->isColumnFlexDirection() ||
        parent()->style()->flexWrap() != FlexNoWrap)
      return true;
    if (!columnFlexItemHasStretchAlignment())
      return true;
  }

  // Flexible horizontal boxes lay out children at their intrinsic widths. Also
  // vertical boxes that don't stretch their kids lay out their children at
  // their intrinsic widths.
  // FIXME: Think about writing-mode here.
  // https://bugs.webkit.org/show_bug.cgi?id=46473
  if (parent()->isDeprecatedFlexibleBox() &&
      (parent()->style()->boxOrient() == HORIZONTAL ||
       parent()->style()->boxAlign() != BSTRETCH))
    return true;

  // Button, input, select, textarea, and legend treat width value of 'auto' as
  // 'intrinsic' unless it's in a stretching column flexbox.
  // FIXME: Think about writing-mode here.
  // https://bugs.webkit.org/show_bug.cgi?id=46473
  if (logicalWidth.isAuto() && !isStretchingColumnFlexItem() &&
      autoWidthShouldFitContent())
    return true;

  if (isHorizontalWritingMode() != containingBlock()->isHorizontalWritingMode())
    return true;

  return false;
}

bool LayoutBox::autoWidthShouldFitContent() const {
  return node() &&
         (isHTMLInputElement(*node()) || isHTMLSelectElement(*node()) ||
          isHTMLButtonElement(*node()) || isHTMLTextAreaElement(*node()) ||
          (isHTMLLegendElement(*node()) && !style()->hasOutOfFlowPosition()));
}

void LayoutBox::computeMarginsForDirection(MarginDirection flowDirection,
                                           const LayoutBlock* containingBlock,
                                           LayoutUnit containerWidth,
                                           LayoutUnit childWidth,
                                           LayoutUnit& marginStart,
                                           LayoutUnit& marginEnd,
                                           Length marginStartLength,
                                           Length marginEndLength) const {
  // First assert that we're not calling this method on box types that don't
  // support margins.
  ASSERT(!isTableCell());
  ASSERT(!isTableRow());
  ASSERT(!isTableSection());
  ASSERT(!isLayoutTableCol());
  if (flowDirection == BlockDirection || isFloating() || isInline()) {
    // Margins are calculated with respect to the logical width of
    // the containing block (8.3)
    // Inline blocks/tables and floats don't have their margins increased.
    marginStart = minimumValueForLength(marginStartLength, containerWidth);
    marginEnd = minimumValueForLength(marginEndLength, containerWidth);
    return;
  }

  if (containingBlock->isFlexibleBox()) {
    // We need to let flexbox handle the margin adjustment - otherwise, flexbox
    // will think we're wider than we actually are and calculate line sizes
    // wrong. See also http://dev.w3.org/csswg/css-flexbox/#auto-margins
    if (marginStartLength.isAuto())
      marginStartLength.setValue(0);
    if (marginEndLength.isAuto())
      marginEndLength.setValue(0);
  }

  LayoutUnit marginStartWidth =
      minimumValueForLength(marginStartLength, containerWidth);
  LayoutUnit marginEndWidth =
      minimumValueForLength(marginEndLength, containerWidth);

  LayoutUnit availableWidth = containerWidth;
  if (avoidsFloats() && containingBlock->isLayoutBlockFlow() &&
      toLayoutBlockFlow(containingBlock)->containsFloats()) {
    availableWidth = containingBlockAvailableLineWidth();
    if (shrinkToAvoidFloats() && availableWidth < containerWidth) {
      marginStart = std::max(LayoutUnit(), marginStartWidth);
      marginEnd = std::max(LayoutUnit(), marginEndWidth);
    }
  }

  // CSS 2.1 (10.3.3): "If 'width' is not 'auto' and 'border-left-width' +
  // 'padding-left' + 'width' + 'padding-right' + 'border-right-width' (plus any
  // of 'margin-left' or 'margin-right' that are not 'auto') is larger than the
  // width of the containing block, then any 'auto' values for 'margin-left' or
  // 'margin-right' are, for the following rules, treated as zero.
  LayoutUnit marginBoxWidth =
      childWidth + (!style()->width().isAuto()
                        ? marginStartWidth + marginEndWidth
                        : LayoutUnit());

  if (marginBoxWidth < availableWidth) {
    // CSS 2.1: "If both 'margin-left' and 'margin-right' are 'auto', their used
    // values are equal. This horizontally centers the element with respect to
    // the edges of the containing block."
    const ComputedStyle& containingBlockStyle = containingBlock->styleRef();
    if ((marginStartLength.isAuto() && marginEndLength.isAuto()) ||
        (!marginStartLength.isAuto() && !marginEndLength.isAuto() &&
         containingBlockStyle.textAlign() == ETextAlign::WebkitCenter)) {
      // Other browsers center the margin box for align=center elements so we
      // match them here.
      LayoutUnit centeredMarginBoxStart = std::max(
          LayoutUnit(),
          (availableWidth - childWidth - marginStartWidth - marginEndWidth) /
              2);
      marginStart = centeredMarginBoxStart + marginStartWidth;
      marginEnd = availableWidth - childWidth - marginStart + marginEndWidth;
      return;
    }

    // Adjust margins for the align attribute
    if ((!containingBlockStyle.isLeftToRightDirection() &&
         containingBlockStyle.textAlign() == ETextAlign::WebkitLeft) ||
        (containingBlockStyle.isLeftToRightDirection() &&
         containingBlockStyle.textAlign() == ETextAlign::WebkitRight)) {
      if (containingBlockStyle.isLeftToRightDirection() !=
          styleRef().isLeftToRightDirection()) {
        if (!marginStartLength.isAuto())
          marginEndLength = Length(Auto);
      } else {
        if (!marginEndLength.isAuto())
          marginStartLength = Length(Auto);
      }
    }

    // CSS 2.1: "If there is exactly one value specified as 'auto', its used
    // value follows from the equality."
    if (marginEndLength.isAuto()) {
      marginStart = marginStartWidth;
      marginEnd = availableWidth - childWidth - marginStart;
      return;
    }

    if (marginStartLength.isAuto()) {
      marginEnd = marginEndWidth;
      marginStart = availableWidth - childWidth - marginEnd;
      return;
    }
  }

  // Either no auto margins, or our margin box width is >= the container width,
  // auto margins will just turn into 0.
  marginStart = marginStartWidth;
  marginEnd = marginEndWidth;
}

DISABLE_CFI_PERF
void LayoutBox::updateLogicalHeight() {
  m_intrinsicContentLogicalHeight = contentLogicalHeight();

  LogicalExtentComputedValues computedValues;
  computeLogicalHeight(computedValues);

  setLogicalHeight(computedValues.m_extent);
  setLogicalTop(computedValues.m_position);
  setMarginBefore(computedValues.m_margins.m_before);
  setMarginAfter(computedValues.m_margins.m_after);
}

static inline Length heightForDocumentElement(const Document& document) {
  return document.documentElement()->layoutObject()->style()->logicalHeight();
}

void LayoutBox::computeLogicalHeight(
    LogicalExtentComputedValues& computedValues) const {
  LayoutUnit height = style()->containsSize() ? borderAndPaddingLogicalHeight()
                                              : logicalHeight();
  computeLogicalHeight(height, logicalTop(), computedValues);
}

void LayoutBox::computeLogicalHeight(
    LayoutUnit logicalHeight,
    LayoutUnit logicalTop,
    LogicalExtentComputedValues& computedValues) const {
  computedValues.m_extent = logicalHeight;
  computedValues.m_position = logicalTop;

  // Cell height is managed by the table.
  if (isTableCell())
    return;

  Length h;
  if (isOutOfFlowPositioned()) {
    computePositionedLogicalHeight(computedValues);
  } else {
    LayoutBlock* cb = containingBlock();

    // If we are perpendicular to our containing block then we need to resolve
    // our block-start and block-end margins so that if they are 'auto' we are
    // centred or aligned within the inline flow containing block: this is done
    // by computing the margins as though they are inline.
    // Note that as this is the 'sizing phase' we are using our own writing mode
    // rather than the containing block's. We use the containing block's writing
    // mode when figuring out the block-direction margins for positioning in
    // |computeAndSetBlockDirectionMargins| (i.e. margin collapsing etc.).
    // http://www.w3.org/TR/2014/CR-css-writing-modes-3-20140320/#orthogonal-flows
    MarginDirection flowDirection =
        isHorizontalWritingMode() != cb->isHorizontalWritingMode()
            ? InlineDirection
            : BlockDirection;

    // For tables, calculate margins only.
    if (isTable()) {
      computeMarginsForDirection(
          flowDirection, cb, containingBlockLogicalWidthForContent(),
          computedValues.m_extent, computedValues.m_margins.m_before,
          computedValues.m_margins.m_after, style()->marginBefore(),
          style()->marginAfter());
      return;
    }

    // FIXME: Account for writing-mode in flexible boxes.
    // https://bugs.webkit.org/show_bug.cgi?id=46418
    bool inHorizontalBox = parent()->isDeprecatedFlexibleBox() &&
                           parent()->style()->boxOrient() == HORIZONTAL;
    bool stretching = parent()->style()->boxAlign() == BSTRETCH;
    bool treatAsReplaced =
        shouldComputeSizeAsReplaced() && (!inHorizontalBox || !stretching);
    bool checkMinMaxHeight = false;

    // The parent box is flexing us, so it has increased or decreased our
    // height. We have to grab our cached flexible height.
    // FIXME: Account for writing-mode in flexible boxes.
    // https://bugs.webkit.org/show_bug.cgi?id=46418
    if (hasOverrideLogicalContentHeight()) {
      h = Length(overrideLogicalContentHeight(), Fixed);
    } else if (treatAsReplaced) {
      h = Length(computeReplacedLogicalHeight(), Fixed);
    } else {
      h = style()->logicalHeight();
      checkMinMaxHeight = true;
    }

    // Block children of horizontal flexible boxes fill the height of the box.
    // FIXME: Account for writing-mode in flexible boxes.
    // https://bugs.webkit.org/show_bug.cgi?id=46418
    if (h.isAuto() && inHorizontalBox &&
        toLayoutDeprecatedFlexibleBox(parent())->isStretchingChildren()) {
      h = Length(parentBox()->contentLogicalHeight() - marginBefore() -
                     marginAfter() - borderAndPaddingLogicalHeight(),
                 Fixed);
      checkMinMaxHeight = false;
    }

    LayoutUnit heightResult;
    if (checkMinMaxHeight) {
      heightResult = computeLogicalHeightUsing(
          MainOrPreferredSize, style()->logicalHeight(),
          computedValues.m_extent - borderAndPaddingLogicalHeight());
      if (heightResult == -1)
        heightResult = computedValues.m_extent;
      heightResult = constrainLogicalHeightByMinMax(
          heightResult,
          computedValues.m_extent - borderAndPaddingLogicalHeight());
    } else {
      // The only times we don't check min/max height are when a fixed length
      // has been given as an override.  Just use that.  The value has already
      // been adjusted for box-sizing.
      ASSERT(h.isFixed());
      heightResult = LayoutUnit(h.value()) + borderAndPaddingLogicalHeight();
    }

    computedValues.m_extent = heightResult;
    computeMarginsForDirection(
        flowDirection, cb, containingBlockLogicalWidthForContent(),
        computedValues.m_extent, computedValues.m_margins.m_before,
        computedValues.m_margins.m_after, style()->marginBefore(),
        style()->marginAfter());
  }

  // WinIE quirk: The <html> block always fills the entire canvas in quirks
  // mode. The <body> always fills the <html> block in quirks mode. Only apply
  // this quirk if the block is normal flow and no height is specified. When
  // we're printing, we also need this quirk if the body or root has a
  // percentage height since we don't set a height in LayoutView when we're
  // printing. So without this quirk, the height has nothing to be a percentage
  // of, and it ends up being 0. That is bad.
  bool paginatedContentNeedsBaseHeight =
      document().printing() && h.isPercentOrCalc() &&
      (isDocumentElement() ||
       (isBody() && heightForDocumentElement(document()).isPercentOrCalc())) &&
      !isInline();
  if (stretchesToViewport() || paginatedContentNeedsBaseHeight) {
    LayoutUnit margins = collapsedMarginBefore() + collapsedMarginAfter();
    LayoutUnit visibleHeight = view()->viewLogicalHeightForPercentages();
    if (isDocumentElement()) {
      computedValues.m_extent =
          std::max(computedValues.m_extent, visibleHeight - margins);
    } else {
      LayoutUnit marginsBordersPadding =
          margins + parentBox()->marginBefore() + parentBox()->marginAfter() +
          parentBox()->borderAndPaddingLogicalHeight();
      computedValues.m_extent = std::max(computedValues.m_extent,
                                         visibleHeight - marginsBordersPadding);
    }
  }
}

LayoutUnit LayoutBox::computeLogicalHeightWithoutLayout() const {
  // TODO(cbiesinger): We should probably return something other than just
  // border + padding, but for now we have no good way to do anything else
  // without layout, so we just use that.
  LogicalExtentComputedValues computedValues;
  computeLogicalHeight(borderAndPaddingLogicalHeight(), LayoutUnit(),
                       computedValues);
  return computedValues.m_extent;
}

LayoutUnit LayoutBox::computeLogicalHeightUsing(
    SizeType heightType,
    const Length& height,
    LayoutUnit intrinsicContentHeight) const {
  LayoutUnit logicalHeight = computeContentAndScrollbarLogicalHeightUsing(
      heightType, height, intrinsicContentHeight);
  if (logicalHeight != -1) {
    if (height.isSpecified())
      logicalHeight = adjustBorderBoxLogicalHeightForBoxSizing(logicalHeight);
    else
      logicalHeight += borderAndPaddingLogicalHeight();
  }
  return logicalHeight;
}

LayoutUnit LayoutBox::computeContentLogicalHeight(
    SizeType heightType,
    const Length& height,
    LayoutUnit intrinsicContentHeight) const {
  LayoutUnit heightIncludingScrollbar =
      computeContentAndScrollbarLogicalHeightUsing(heightType, height,
                                                   intrinsicContentHeight);
  if (heightIncludingScrollbar == -1)
    return LayoutUnit(-1);
  LayoutUnit adjusted = heightIncludingScrollbar;
  if (height.isSpecified()) {
    // Keywords don't get adjusted for box-sizing
    adjusted =
        adjustContentBoxLogicalHeightForBoxSizing(heightIncludingScrollbar);
  }
  return std::max(LayoutUnit(), adjusted - scrollbarLogicalHeight());
}

LayoutUnit LayoutBox::computeIntrinsicLogicalContentHeightUsing(
    const Length& logicalHeightLength,
    LayoutUnit intrinsicContentHeight,
    LayoutUnit borderAndPadding) const {
  // FIXME(cbiesinger): The css-sizing spec is considering changing what
  // min-content/max-content should resolve to.
  // If that happens, this code will have to change.
  if (logicalHeightLength.isMinContent() ||
      logicalHeightLength.isMaxContent() ||
      logicalHeightLength.isFitContent()) {
    if (isAtomicInlineLevel())
      return intrinsicSize().height();
    return intrinsicContentHeight;
  }
  if (logicalHeightLength.isFillAvailable())
    return containingBlock()->availableLogicalHeight(
               ExcludeMarginBorderPadding) -
           borderAndPadding;
  ASSERT_NOT_REACHED();
  return LayoutUnit();
}

LayoutUnit LayoutBox::computeContentAndScrollbarLogicalHeightUsing(
    SizeType heightType,
    const Length& height,
    LayoutUnit intrinsicContentHeight) const {
  if (height.isAuto())
    return heightType == MinSize ? LayoutUnit() : LayoutUnit(-1);
  // FIXME(cbiesinger): The css-sizing spec is considering changing what
  // min-content/max-content should resolve to.
  // If that happens, this code will have to change.
  if (height.isIntrinsic()) {
    if (intrinsicContentHeight == -1)
      return LayoutUnit(-1);  // Intrinsic height isn't available.
    return computeIntrinsicLogicalContentHeightUsing(
               height, intrinsicContentHeight,
               borderAndPaddingLogicalHeight()) +
           scrollbarLogicalHeight();
  }
  if (height.isFixed())
    return LayoutUnit(height.value());
  if (height.isPercentOrCalc())
    return computePercentageLogicalHeight(height);
  return LayoutUnit(-1);
}

bool LayoutBox::stretchesToViewportInQuirksMode() const {
  if (!isDocumentElement() && !isBody())
    return false;
  return style()->logicalHeight().isAuto() &&
         !isFloatingOrOutOfFlowPositioned() && !isInline() &&
         !flowThreadContainingBlock();
}

bool LayoutBox::skipContainingBlockForPercentHeightCalculation(
    const LayoutBox* containingBlock) const {
  // If the writing mode of the containing block is orthogonal to ours, it means
  // that we shouldn't skip anything, since we're going to resolve the
  // percentage height against a containing block *width*.
  if (isHorizontalWritingMode() != containingBlock->isHorizontalWritingMode())
    return false;

  // Anonymous blocks should not impede percentage resolution on a child.
  // Examples of such anonymous blocks are blocks wrapped around inlines that
  // have block siblings (from the CSS spec) and multicol flow threads (an
  // implementation detail). Another implementation detail, ruby runs, create
  // anonymous inline-blocks, so skip those too. All other types of anonymous
  // objects, such as table-cells, will be treated just as if they were
  // non-anonymous.
  if (containingBlock->isAnonymous()) {
    EDisplay display = containingBlock->styleRef().display();
    return display == EDisplay::Block || display == EDisplay::InlineBlock;
  }

  // For quirks mode, we skip most auto-height containing blocks when computing
  // percentages.
  return document().inQuirksMode() && !containingBlock->isTableCell() &&
         !containingBlock->isOutOfFlowPositioned() &&
         !containingBlock->isLayoutGrid() &&
         containingBlock->style()->logicalHeight().isAuto();
}

LayoutUnit LayoutBox::computePercentageLogicalHeight(
    const Length& height) const {
  LayoutBlock* cb = containingBlock();
  const LayoutBox* containingBlockChild = this;
  bool skippedAutoHeightContainingBlock = false;
  LayoutUnit rootMarginBorderPaddingHeight;
  while (!cb->isLayoutView() &&
         skipContainingBlockForPercentHeightCalculation(cb)) {
    if (cb->isBody() || cb->isDocumentElement())
      rootMarginBorderPaddingHeight += cb->marginBefore() + cb->marginAfter() +
                                       cb->borderAndPaddingLogicalHeight();
    skippedAutoHeightContainingBlock = true;
    containingBlockChild = cb;
    cb = cb->containingBlock();
  }
  cb->addPercentHeightDescendant(const_cast<LayoutBox*>(this));

  LayoutUnit availableHeight(-1);
  if (isHorizontalWritingMode() != cb->isHorizontalWritingMode()) {
    availableHeight =
        containingBlockChild->containingBlockLogicalWidthForContent();
  } else if (hasOverrideContainingBlockLogicalHeight()) {
    availableHeight = overrideContainingBlockContentLogicalHeight();
  } else if (cb->isTableCell()) {
    if (!skippedAutoHeightContainingBlock) {
      // Table cells violate what the CSS spec says to do with heights.
      // Basically we don't care if the cell specified a height or not. We just
      // always make ourselves be a percentage of the cell's current content
      // height.
      if (!cb->hasOverrideLogicalContentHeight()) {
        // https://drafts.csswg.org/css-tables-3/#row-layout:
        // For the purpose of calculating [the minimum height of a row],
        // descendants of table cells whose height depends on percentages
        // of their parent cell's height are considered to have an auto
        // height if they have overflow set to visible or hidden or if
        // they are replaced elements, and a 0px height if they have not.
        LayoutTableCell* cell = toLayoutTableCell(cb);
        if (style()->overflowY() != EOverflow::Visible &&
            style()->overflowY() != EOverflow::Hidden &&
            !shouldBeConsideredAsReplaced() &&
            (!cell->style()->logicalHeight().isAuto() ||
             !cell->table()->style()->logicalHeight().isAuto()))
          return LayoutUnit();
        return LayoutUnit(-1);
      }
      availableHeight = cb->overrideLogicalContentHeight();
    }
  } else {
    availableHeight = cb->availableLogicalHeightForPercentageComputation();
  }

  if (availableHeight == -1)
    return availableHeight;

  availableHeight -= rootMarginBorderPaddingHeight;

  if (isTable() && isOutOfFlowPositioned())
    availableHeight += cb->paddingLogicalHeight();

  LayoutUnit result = valueForLength(height, availableHeight);
  // |overrideLogicalContentHeight| is the maximum height made available by the
  // cell to its percent height children when we decide they can determine the
  // height of the cell. If the percent height child is box-sizing:content-box
  // then we must subtract the border and padding from the cell's
  // |availableHeight| (given by |overrideLogicalContentHeight|) to arrive
  // at the child's computed height.
  bool subtractBorderAndPadding =
      isTable() || (cb->isTableCell() && !skippedAutoHeightContainingBlock &&
                    cb->hasOverrideLogicalContentHeight() &&
                    style()->boxSizing() == BoxSizingContentBox);
  if (subtractBorderAndPadding) {
    result -= borderAndPaddingLogicalHeight();
    return std::max(LayoutUnit(), result);
  }
  return result;
}

LayoutUnit LayoutBox::computeReplacedLogicalWidth(
    ShouldComputePreferred shouldComputePreferred) const {
  return computeReplacedLogicalWidthRespectingMinMaxWidth(
      computeReplacedLogicalWidthUsing(MainOrPreferredSize,
                                       style()->logicalWidth()),
      shouldComputePreferred);
}

LayoutUnit LayoutBox::computeReplacedLogicalWidthRespectingMinMaxWidth(
    LayoutUnit logicalWidth,
    ShouldComputePreferred shouldComputePreferred) const {
  LayoutUnit minLogicalWidth = (shouldComputePreferred == ComputePreferred &&
                                style()->logicalMinWidth().isPercentOrCalc())
                                   ? logicalWidth
                                   : computeReplacedLogicalWidthUsing(
                                         MinSize, style()->logicalMinWidth());
  LayoutUnit maxLogicalWidth =
      (shouldComputePreferred == ComputePreferred &&
       style()->logicalMaxWidth().isPercentOrCalc()) ||
              style()->logicalMaxWidth().isMaxSizeNone()
          ? logicalWidth
          : computeReplacedLogicalWidthUsing(MaxSize,
                                             style()->logicalMaxWidth());
  return std::max(minLogicalWidth, std::min(logicalWidth, maxLogicalWidth));
}

LayoutUnit LayoutBox::computeReplacedLogicalWidthUsing(
    SizeType sizeType,
    const Length& logicalWidth) const {
  ASSERT(sizeType == MinSize || sizeType == MainOrPreferredSize ||
         !logicalWidth.isAuto());
  if (sizeType == MinSize && logicalWidth.isAuto())
    return adjustContentBoxLogicalWidthForBoxSizing(LayoutUnit());

  switch (logicalWidth.type()) {
    case Fixed:
      return adjustContentBoxLogicalWidthForBoxSizing(logicalWidth.value());
    case MinContent:
    case MaxContent: {
      // MinContent/MaxContent don't need the availableLogicalWidth argument.
      LayoutUnit availableLogicalWidth;
      return computeIntrinsicLogicalWidthUsing(logicalWidth,
                                               availableLogicalWidth,
                                               borderAndPaddingLogicalWidth()) -
             borderAndPaddingLogicalWidth();
    }
    case FitContent:
    case FillAvailable:
    case Percent:
    case Calculated: {
      // FIXME: containingBlockLogicalWidthForContent() is wrong if the replaced
      // element's writing-mode is perpendicular to the containing block's
      // writing-mode. https://bugs.webkit.org/show_bug.cgi?id=46496
      const LayoutUnit cw = isOutOfFlowPositioned()
                                ? containingBlockLogicalWidthForPositioned(
                                      toLayoutBoxModelObject(container()))
                                : containingBlockLogicalWidthForContent();
      Length containerLogicalWidth = containingBlock()->style()->logicalWidth();
      // FIXME: Handle cases when containing block width is calculated or
      // viewport percent. https://bugs.webkit.org/show_bug.cgi?id=91071
      if (logicalWidth.isIntrinsic())
        return computeIntrinsicLogicalWidthUsing(
                   logicalWidth, cw, borderAndPaddingLogicalWidth()) -
               borderAndPaddingLogicalWidth();
      if (cw > 0 || (!cw && (containerLogicalWidth.isFixed() ||
                             containerLogicalWidth.isPercentOrCalc())))
        return adjustContentBoxLogicalWidthForBoxSizing(
            minimumValueForLength(logicalWidth, cw));
      return LayoutUnit();
    }
    case Auto:
    case MaxSizeNone:
      return intrinsicLogicalWidth();
    case ExtendToZoom:
    case DeviceWidth:
    case DeviceHeight:
      break;
  }

  ASSERT_NOT_REACHED();
  return LayoutUnit();
}

LayoutUnit LayoutBox::computeReplacedLogicalHeight(LayoutUnit) const {
  return computeReplacedLogicalHeightRespectingMinMaxHeight(
      computeReplacedLogicalHeightUsing(MainOrPreferredSize,
                                        style()->logicalHeight()));
}

bool LayoutBox::logicalHeightComputesAsNone(SizeType sizeType) const {
  ASSERT(sizeType == MinSize || sizeType == MaxSize);
  Length logicalHeight = sizeType == MinSize ? style()->logicalMinHeight()
                                             : style()->logicalMaxHeight();
  Length initialLogicalHeight = sizeType == MinSize
                                    ? ComputedStyle::initialMinSize()
                                    : ComputedStyle::initialMaxSize();

  if (logicalHeight == initialLogicalHeight)
    return true;

  if (LayoutBlock* cb = containingBlockForAutoHeightDetection(logicalHeight))
    return cb->hasAutoHeightOrContainingBlockWithAutoHeight();
  return false;
}

LayoutUnit LayoutBox::computeReplacedLogicalHeightRespectingMinMaxHeight(
    LayoutUnit logicalHeight) const {
  // If the height of the containing block is not specified explicitly (i.e., it
  // depends on content height), and this element is not absolutely positioned,
  // the percentage value is treated as '0' (for 'min-height') or 'none' (for
  // 'max-height').
  LayoutUnit minLogicalHeight;
  if (!logicalHeightComputesAsNone(MinSize))
    minLogicalHeight =
        computeReplacedLogicalHeightUsing(MinSize, style()->logicalMinHeight());
  LayoutUnit maxLogicalHeight = logicalHeight;
  if (!logicalHeightComputesAsNone(MaxSize))
    maxLogicalHeight =
        computeReplacedLogicalHeightUsing(MaxSize, style()->logicalMaxHeight());
  return std::max(minLogicalHeight, std::min(logicalHeight, maxLogicalHeight));
}

LayoutUnit LayoutBox::computeReplacedLogicalHeightUsing(
    SizeType sizeType,
    const Length& logicalHeight) const {
  ASSERT(sizeType == MinSize || sizeType == MainOrPreferredSize ||
         !logicalHeight.isAuto());
  if (sizeType == MinSize && logicalHeight.isAuto())
    return adjustContentBoxLogicalHeightForBoxSizing(LayoutUnit());

  switch (logicalHeight.type()) {
    case Fixed:
      return adjustContentBoxLogicalHeightForBoxSizing(logicalHeight.value());
    case Percent:
    case Calculated: {
      // TODO(rego): Check if we can somehow reuse
      // LayoutBox::computePercentageLogicalHeight() and/or
      // LayoutBlock::availableLogicalHeightForPercentageComputation() (see
      // http://crbug.com/635655).
      LayoutObject* cb =
          isOutOfFlowPositioned() ? container() : containingBlock();
      while (cb->isAnonymous())
        cb = cb->containingBlock();
      LayoutUnit stretchedHeight(-1);
      if (cb->isLayoutBlock()) {
        LayoutBlock* block = toLayoutBlock(cb);
        block->addPercentHeightDescendant(const_cast<LayoutBox*>(this));
        if (block->isFlexItem())
          stretchedHeight =
              toLayoutFlexibleBox(block->parent())
                  ->childLogicalHeightForPercentageResolution(*block);
        else if (block->isGridItem() &&
                 block->hasOverrideLogicalContentHeight())
          stretchedHeight = block->overrideLogicalContentHeight();
      }

      if (cb->isOutOfFlowPositioned() && cb->style()->height().isAuto() &&
          !(cb->style()->top().isAuto() || cb->style()->bottom().isAuto())) {
        SECURITY_DCHECK(cb->isLayoutBlock());
        LayoutBlock* block = toLayoutBlock(cb);
        LogicalExtentComputedValues computedValues;
        block->computeLogicalHeight(block->logicalHeight(), LayoutUnit(),
                                    computedValues);
        LayoutUnit newContentHeight = computedValues.m_extent -
                                      block->borderAndPaddingLogicalHeight() -
                                      block->scrollbarLogicalHeight();
        LayoutUnit newHeight =
            block->adjustContentBoxLogicalHeightForBoxSizing(newContentHeight);
        return adjustContentBoxLogicalHeightForBoxSizing(
            valueForLength(logicalHeight, newHeight));
      }

      // FIXME: availableLogicalHeight() is wrong if the replaced element's
      // writing-mode is perpendicular to the containing block's writing-mode.
      // https://bugs.webkit.org/show_bug.cgi?id=46496
      LayoutUnit availableHeight;
      if (isOutOfFlowPositioned()) {
        availableHeight = containingBlockLogicalHeightForPositioned(
            toLayoutBoxModelObject(cb));
      } else if (stretchedHeight != -1) {
        availableHeight = stretchedHeight;
      } else if (hasOverrideContainingBlockLogicalHeight()) {
        availableHeight = overrideContainingBlockContentLogicalHeight();
      } else {
        availableHeight =
            containingBlockLogicalHeightForContent(IncludeMarginBorderPadding);
        // It is necessary to use the border-box to match WinIE's broken
        // box model.  This is essential for sizing inside
        // table cells using percentage heights.
        // FIXME: This needs to be made writing-mode-aware. If the cell and
        // image are perpendicular writing-modes, this isn't right.
        // https://bugs.webkit.org/show_bug.cgi?id=46997
        while (cb && !cb->isLayoutView() &&
               (cb->style()->logicalHeight().isAuto() ||
                cb->style()->logicalHeight().isPercentOrCalc())) {
          if (cb->isTableCell()) {
            // Don't let table cells squeeze percent-height replaced elements
            // <http://bugs.webkit.org/show_bug.cgi?id=15359>
            availableHeight =
                std::max(availableHeight, intrinsicLogicalHeight());
            return valueForLength(
                logicalHeight,
                availableHeight - borderAndPaddingLogicalHeight());
          }
          toLayoutBlock(cb)->addPercentHeightDescendant(
              const_cast<LayoutBox*>(this));
          cb = cb->containingBlock();
        }
      }
      return adjustContentBoxLogicalHeightForBoxSizing(
          valueForLength(logicalHeight, availableHeight));
    }
    case MinContent:
    case MaxContent:
    case FitContent:
    case FillAvailable:
      return adjustContentBoxLogicalHeightForBoxSizing(
          computeIntrinsicLogicalContentHeightUsing(logicalHeight,
                                                    intrinsicLogicalHeight(),
                                                    borderAndPaddingHeight()));
    default:
      return intrinsicLogicalHeight();
  }
}

LayoutUnit LayoutBox::availableLogicalHeight(
    AvailableLogicalHeightType heightType) const {
  // http://www.w3.org/TR/CSS2/visudet.html#propdef-height - We are interested
  // in the content height.
  // FIXME: Should we pass intrinsicContentLogicalHeight() instead of -1 here?
  return constrainContentBoxLogicalHeightByMinMax(
      availableLogicalHeightUsing(style()->logicalHeight(), heightType),
      LayoutUnit(-1));
}

LayoutUnit LayoutBox::availableLogicalHeightUsing(
    const Length& h,
    AvailableLogicalHeightType heightType) const {
  if (isLayoutView()) {
    return LayoutUnit(
        isHorizontalWritingMode()
            ? toLayoutView(this)->frameView()->visibleContentSize().height()
            : toLayoutView(this)->frameView()->visibleContentSize().width());
  }

  // We need to stop here, since we don't want to increase the height of the
  // table artificially.  We're going to rely on this cell getting expanded to
  // some new height, and then when we lay out again we'll use the calculation
  // below.
  if (isTableCell() && (h.isAuto() || h.isPercentOrCalc())) {
    if (hasOverrideLogicalContentHeight())
      return overrideLogicalContentHeight();
    return logicalHeight() - borderAndPaddingLogicalHeight();
  }

  if (isFlexItem()) {
    LayoutFlexibleBox& flexBox = toLayoutFlexibleBox(*parent());
    LayoutUnit stretchedHeight =
        flexBox.childLogicalHeightForPercentageResolution(*this);
    if (stretchedHeight != LayoutUnit(-1))
      return stretchedHeight;
  }

  if (h.isPercentOrCalc() && isOutOfFlowPositioned()) {
    // FIXME: This is wrong if the containingBlock has a perpendicular writing
    // mode.
    LayoutUnit availableHeight =
        containingBlockLogicalHeightForPositioned(containingBlock());
    return adjustContentBoxLogicalHeightForBoxSizing(
        valueForLength(h, availableHeight));
  }

  // FIXME: Should we pass intrinsicContentLogicalHeight() instead of -1 here?
  LayoutUnit heightIncludingScrollbar =
      computeContentAndScrollbarLogicalHeightUsing(MainOrPreferredSize, h,
                                                   LayoutUnit(-1));
  if (heightIncludingScrollbar != -1)
    return std::max(LayoutUnit(), adjustContentBoxLogicalHeightForBoxSizing(
                                      heightIncludingScrollbar) -
                                      scrollbarLogicalHeight());

  // FIXME: Check logicalTop/logicalBottom here to correctly handle vertical
  // writing-mode.
  // https://bugs.webkit.org/show_bug.cgi?id=46500
  if (isLayoutBlock() && isOutOfFlowPositioned() &&
      style()->height().isAuto() &&
      !(style()->top().isAuto() || style()->bottom().isAuto())) {
    LayoutBlock* block = const_cast<LayoutBlock*>(toLayoutBlock(this));
    LogicalExtentComputedValues computedValues;
    block->computeLogicalHeight(block->logicalHeight(), LayoutUnit(),
                                computedValues);
    LayoutUnit newContentHeight = computedValues.m_extent -
                                  block->borderAndPaddingLogicalHeight() -
                                  block->scrollbarLogicalHeight();
    return adjustContentBoxLogicalHeightForBoxSizing(newContentHeight);
  }

  // FIXME: This is wrong if the containingBlock has a perpendicular writing
  // mode.
  LayoutUnit availableHeight =
      containingBlockLogicalHeightForContent(heightType);
  if (heightType == ExcludeMarginBorderPadding) {
    // FIXME: Margin collapsing hasn't happened yet, so this incorrectly removes
    // collapsed margins.
    availableHeight -=
        marginBefore() + marginAfter() + borderAndPaddingLogicalHeight();
  }
  return availableHeight;
}

void LayoutBox::computeAndSetBlockDirectionMargins(
    const LayoutBlock* containingBlock) {
  LayoutUnit marginBefore;
  LayoutUnit marginAfter;
  computeMarginsForDirection(
      BlockDirection, containingBlock, containingBlockLogicalWidthForContent(),
      logicalHeight(), marginBefore, marginAfter,
      style()->marginBeforeUsing(containingBlock->style()),
      style()->marginAfterUsing(containingBlock->style()));
  // Note that in this 'positioning phase' of the layout we are using the
  // containing block's writing mode rather than our own when calculating
  // margins.
  // http://www.w3.org/TR/2014/CR-css-writing-modes-3-20140320/#orthogonal-flows
  containingBlock->setMarginBeforeForChild(*this, marginBefore);
  containingBlock->setMarginAfterForChild(*this, marginAfter);
}

LayoutUnit LayoutBox::containingBlockLogicalWidthForPositioned(
    const LayoutBoxModelObject* containingBlock,
    bool checkForPerpendicularWritingMode) const {
  if (checkForPerpendicularWritingMode &&
      containingBlock->isHorizontalWritingMode() != isHorizontalWritingMode())
    return containingBlockLogicalHeightForPositioned(containingBlock, false);

  // Use viewport as container for top-level fixed-position elements.
  if (style()->position() == FixedPosition && containingBlock->isLayoutView() &&
      !document().printing()) {
    const LayoutView* view = toLayoutView(containingBlock);
    if (FrameView* frameView = view->frameView()) {
      // Don't use visibleContentRect since the PaintLayer's size has not been
      // set yet.
      LayoutSize viewportSize(
          frameView->layoutViewportScrollableArea()->excludeScrollbars(
              frameView->frameRect().size()));
      return LayoutUnit(containingBlock->isHorizontalWritingMode()
                            ? viewportSize.width()
                            : viewportSize.height());
    }
  }

  if (hasOverrideContainingBlockLogicalWidth())
    return overrideContainingBlockContentLogicalWidth();

  // Ensure we compute our width based on the width of our rel-pos inline
  // container rather than any anonymous block created to manage a block-flow
  // ancestor of ours in the rel-pos inline's inline flow.
  if (containingBlock->isAnonymousBlock() && containingBlock->isRelPositioned())
    containingBlock = toLayoutBox(containingBlock)->continuation();
  else if (containingBlock->isBox())
    return std::max(LayoutUnit(),
                    toLayoutBox(containingBlock)->clientLogicalWidth());

  ASSERT(containingBlock->isLayoutInline() &&
         containingBlock->isInFlowPositioned());

  const LayoutInline* flow = toLayoutInline(containingBlock);
  InlineFlowBox* first = flow->firstLineBox();
  InlineFlowBox* last = flow->lastLineBox();

  // If the containing block is empty, return a width of 0.
  if (!first || !last)
    return LayoutUnit();

  LayoutUnit fromLeft;
  LayoutUnit fromRight;
  if (containingBlock->style()->isLeftToRightDirection()) {
    fromLeft = first->logicalLeft() + first->borderLogicalLeft();
    fromRight =
        last->logicalLeft() + last->logicalWidth() - last->borderLogicalRight();
  } else {
    fromRight = first->logicalLeft() + first->logicalWidth() -
                first->borderLogicalRight();
    fromLeft = last->logicalLeft() + last->borderLogicalLeft();
  }

  return std::max(LayoutUnit(), fromRight - fromLeft);
}

LayoutUnit LayoutBox::containingBlockLogicalHeightForPositioned(
    const LayoutBoxModelObject* containingBlock,
    bool checkForPerpendicularWritingMode) const {
  if (checkForPerpendicularWritingMode &&
      containingBlock->isHorizontalWritingMode() != isHorizontalWritingMode())
    return containingBlockLogicalWidthForPositioned(containingBlock, false);

  // Use viewport as container for top-level fixed-position elements.
  if (style()->position() == FixedPosition && containingBlock->isLayoutView() &&
      !document().printing()) {
    const LayoutView* view = toLayoutView(containingBlock);
    if (FrameView* frameView = view->frameView()) {
      // Don't use visibleContentRect since the PaintLayer's size has not been
      // set yet.
      LayoutSize viewportSize(
          frameView->layoutViewportScrollableArea()->excludeScrollbars(
              frameView->frameRect().size()));
      return containingBlock->isHorizontalWritingMode() ? viewportSize.height()
                                                        : viewportSize.width();
    }
  }

  if (hasOverrideContainingBlockLogicalHeight())
    return overrideContainingBlockContentLogicalHeight();

  if (containingBlock->isBox()) {
    const LayoutBlock* cb = containingBlock->isLayoutBlock()
                                ? toLayoutBlock(containingBlock)
                                : containingBlock->containingBlock();
    return cb->clientLogicalHeight();
  }

  ASSERT(containingBlock->isLayoutInline() &&
         containingBlock->isInFlowPositioned());

  const LayoutInline* flow = toLayoutInline(containingBlock);
  InlineFlowBox* first = flow->firstLineBox();
  InlineFlowBox* last = flow->lastLineBox();

  // If the containing block is empty, return a height of 0.
  if (!first || !last)
    return LayoutUnit();

  LayoutUnit heightResult;
  LayoutRect boundingBox(flow->linesBoundingBox());
  if (containingBlock->isHorizontalWritingMode())
    heightResult = boundingBox.height();
  else
    heightResult = boundingBox.width();
  heightResult -=
      (containingBlock->borderBefore() + containingBlock->borderAfter());
  return heightResult;
}

static LayoutUnit accumulateStaticOffsetForFlowThread(
    LayoutBox& layoutBox,
    LayoutUnit inlinePosition,
    LayoutUnit& blockPosition) {
  if (layoutBox.isTableRow())
    return LayoutUnit();
  blockPosition += layoutBox.logicalTop();
  if (!layoutBox.isLayoutFlowThread())
    return LayoutUnit();
  LayoutUnit previousInlinePosition = inlinePosition;
  // We're walking out of a flowthread here. This flow thread is not in the
  // containing block chain, so we need to convert the position from the
  // coordinate space of this flowthread to the containing coordinate space.
  toLayoutFlowThread(layoutBox).flowThreadToContainingCoordinateSpace(
      blockPosition, inlinePosition);
  return inlinePosition - previousInlinePosition;
}

void LayoutBox::computeInlineStaticDistance(
    Length& logicalLeft,
    Length& logicalRight,
    const LayoutBox* child,
    const LayoutBoxModelObject* containerBlock,
    LayoutUnit containerLogicalWidth) {
  if (!logicalLeft.isAuto() || !logicalRight.isAuto())
    return;

  // For multicol we also need to keep track of the block position, since that
  // determines which column we're in and thus affects the inline position.
  LayoutUnit staticBlockPosition = child->layer()->staticBlockPosition();

  // FIXME: The static distance computation has not been patched for mixed
  // writing modes yet.
  if (child->parent()->style()->direction() == TextDirection::Ltr) {
    LayoutUnit staticPosition = child->layer()->staticInlinePosition() -
                                containerBlock->borderLogicalLeft();
    for (LayoutObject* curr = child->parent(); curr && curr != containerBlock;
         curr = curr->container()) {
      if (curr->isBox()) {
        staticPosition += toLayoutBox(curr)->logicalLeft();
        if (toLayoutBox(curr)->isInFlowPositioned())
          staticPosition +=
              toLayoutBox(curr)->offsetForInFlowPosition().width();
        if (curr->isInsideFlowThread())
          staticPosition += accumulateStaticOffsetForFlowThread(
              *toLayoutBox(curr), staticPosition, staticBlockPosition);
      } else if (curr->isInline()) {
        if (curr->isInFlowPositioned()) {
          if (!curr->style()->logicalLeft().isAuto())
            staticPosition +=
                valueForLength(curr->style()->logicalLeft(),
                               curr->containingBlock()->availableWidth());
          else
            staticPosition -=
                valueForLength(curr->style()->logicalRight(),
                               curr->containingBlock()->availableWidth());
        }
      }
    }
    logicalLeft.setValue(Fixed, staticPosition);
  } else {
    LayoutBox* enclosingBox = child->parent()->enclosingBox();
    LayoutUnit staticPosition = child->layer()->staticInlinePosition() +
                                containerLogicalWidth +
                                containerBlock->borderLogicalLeft();
    for (LayoutObject* curr = child->parent(); curr; curr = curr->container()) {
      if (curr->isBox()) {
        if (curr == enclosingBox)
          staticPosition -= enclosingBox->logicalWidth();
        if (curr != containerBlock) {
          staticPosition -= toLayoutBox(curr)->logicalLeft();
          if (toLayoutBox(curr)->isInFlowPositioned())
            staticPosition -=
                toLayoutBox(curr)->offsetForInFlowPosition().width();
          if (curr->isInsideFlowThread())
            staticPosition -= accumulateStaticOffsetForFlowThread(
                *toLayoutBox(curr), staticPosition, staticBlockPosition);
        }
      } else if (curr->isInline()) {
        if (curr->isInFlowPositioned()) {
          if (!curr->style()->logicalLeft().isAuto())
            staticPosition -=
                valueForLength(curr->style()->logicalLeft(),
                               curr->containingBlock()->availableWidth());
          else
            staticPosition +=
                valueForLength(curr->style()->logicalRight(),
                               curr->containingBlock()->availableWidth());
        }
      }
      if (curr == containerBlock)
        break;
    }
    logicalRight.setValue(Fixed, staticPosition);
  }
}

void LayoutBox::computePositionedLogicalWidth(
    LogicalExtentComputedValues& computedValues) const {
  // QUESTIONS
  // FIXME 1: Should we still deal with these the cases of 'left' or 'right'
  // having the type 'static' in determining whether to calculate the static
  // distance?
  // NOTE: 'static' is not a legal value for 'left' or 'right' as of CSS 2.1.

  // FIXME 2: Can perhaps optimize out cases when max-width/min-width are
  // greater than or less than the computed width(). Be careful of box-sizing
  // and percentage issues.

  // The following is based off of the W3C Working Draft from April 11, 2006 of
  // CSS 2.1: Section 10.3.7 "Absolutely positioned, non-replaced elements"
  // <http://www.w3.org/TR/CSS21/visudet.html#abs-non-replaced-width>
  // (block-style-comments in this function and in
  // computePositionedLogicalWidthUsing() correspond to text from the spec)

  // We don't use containingBlock(), since we may be positioned by an enclosing
  // relative positioned inline.
  const LayoutBoxModelObject* containerBlock =
      toLayoutBoxModelObject(container());

  const LayoutUnit containerLogicalWidth =
      containingBlockLogicalWidthForPositioned(containerBlock);

  // Use the container block's direction except when calculating the static
  // distance. This conforms with the reference results for
  // abspos-replaced-width-margin-000.htm of the CSS 2.1 test suite.
  TextDirection containerDirection = containerBlock->style()->direction();

  bool isHorizontal = isHorizontalWritingMode();
  const LayoutUnit bordersPlusPadding = borderAndPaddingLogicalWidth();
  const Length marginLogicalLeft =
      isHorizontal ? style()->marginLeft() : style()->marginTop();
  const Length marginLogicalRight =
      isHorizontal ? style()->marginRight() : style()->marginBottom();

  Length logicalLeftLength = style()->logicalLeft();
  Length logicalRightLength = style()->logicalRight();
  // ---------------------------------------------------------------------------
  //  For the purposes of this section and the next, the term "static position"
  //  (of an element) refers, roughly, to the position an element would have had
  //  in the normal flow. More precisely:
  //
  //  * The static position for 'left' is the distance from the left edge of the
  //    containing block to the left margin edge of a hypothetical box that
  //    would have been the first box of the element if its 'position' property
  //    had been 'static' and 'float' had been 'none'. The value is negative if
  //    the hypothetical box is to the left of the containing block.
  //  * The static position for 'right' is the distance from the right edge of
  //    the containing block to the right margin edge of the same hypothetical
  //    box as above. The value is positive if the hypothetical box is to the
  //    left of the containing block's edge.
  //
  //  But rather than actually calculating the dimensions of that hypothetical
  //  box, user agents are free to make a guess at its probable position.
  //
  //  For the purposes of calculating the static position, the containing block
  //  of fixed positioned elements is the initial containing block instead of
  //  the viewport, and all scrollable boxes should be assumed to be scrolled to
  //  their origin.
  // ---------------------------------------------------------------------------
  // see FIXME 1
  // Calculate the static distance if needed.
  computeInlineStaticDistance(logicalLeftLength, logicalRightLength, this,
                              containerBlock, containerLogicalWidth);

  // Calculate constraint equation values for 'width' case.
  computePositionedLogicalWidthUsing(
      MainOrPreferredSize, style()->logicalWidth(), containerBlock,
      containerDirection, containerLogicalWidth, bordersPlusPadding,
      logicalLeftLength, logicalRightLength, marginLogicalLeft,
      marginLogicalRight, computedValues);

  // Calculate constraint equation values for 'max-width' case.
  if (!style()->logicalMaxWidth().isMaxSizeNone()) {
    LogicalExtentComputedValues maxValues;

    computePositionedLogicalWidthUsing(
        MaxSize, style()->logicalMaxWidth(), containerBlock, containerDirection,
        containerLogicalWidth, bordersPlusPadding, logicalLeftLength,
        logicalRightLength, marginLogicalLeft, marginLogicalRight, maxValues);

    if (computedValues.m_extent > maxValues.m_extent) {
      computedValues.m_extent = maxValues.m_extent;
      computedValues.m_position = maxValues.m_position;
      computedValues.m_margins.m_start = maxValues.m_margins.m_start;
      computedValues.m_margins.m_end = maxValues.m_margins.m_end;
    }
  }

  // Calculate constraint equation values for 'min-width' case.
  if (!style()->logicalMinWidth().isZero() ||
      style()->logicalMinWidth().isIntrinsic()) {
    LogicalExtentComputedValues minValues;

    computePositionedLogicalWidthUsing(
        MinSize, style()->logicalMinWidth(), containerBlock, containerDirection,
        containerLogicalWidth, bordersPlusPadding, logicalLeftLength,
        logicalRightLength, marginLogicalLeft, marginLogicalRight, minValues);

    if (computedValues.m_extent < minValues.m_extent) {
      computedValues.m_extent = minValues.m_extent;
      computedValues.m_position = minValues.m_position;
      computedValues.m_margins.m_start = minValues.m_margins.m_start;
      computedValues.m_margins.m_end = minValues.m_margins.m_end;
    }
  }

  if (!style()->hasStaticInlinePosition(isHorizontal))
    computedValues.m_position += extraInlineOffset();

  computedValues.m_extent += bordersPlusPadding;
}

void LayoutBox::computeLogicalLeftPositionedOffset(
    LayoutUnit& logicalLeftPos,
    const LayoutBox* child,
    LayoutUnit logicalWidthValue,
    const LayoutBoxModelObject* containerBlock,
    LayoutUnit containerLogicalWidth) {
  // Deal with differing writing modes here. Our offset needs to be in the
  // containing block's coordinate space. If the containing block is flipped
  // along this axis, then we need to flip the coordinate. This can only happen
  // if the containing block is both a flipped mode and perpendicular to us.
  if (containerBlock->isHorizontalWritingMode() !=
          child->isHorizontalWritingMode() &&
      containerBlock->style()->isFlippedBlocksWritingMode()) {
    logicalLeftPos = containerLogicalWidth - logicalWidthValue - logicalLeftPos;
    logicalLeftPos +=
        (child->isHorizontalWritingMode() ? containerBlock->borderRight()
                                          : containerBlock->borderBottom());
  } else {
    logicalLeftPos +=
        (child->isHorizontalWritingMode() ? containerBlock->borderLeft()
                                          : containerBlock->borderTop());
  }
}

LayoutUnit LayoutBox::shrinkToFitLogicalWidth(
    LayoutUnit availableLogicalWidth,
    LayoutUnit bordersPlusPadding) const {
  LayoutUnit preferredLogicalWidth =
      maxPreferredLogicalWidth() - bordersPlusPadding;
  LayoutUnit preferredMinLogicalWidth =
      minPreferredLogicalWidth() - bordersPlusPadding;
  return std::min(std::max(preferredMinLogicalWidth, availableLogicalWidth),
                  preferredLogicalWidth);
}

void LayoutBox::computePositionedLogicalWidthUsing(
    SizeType widthSizeType,
    Length logicalWidth,
    const LayoutBoxModelObject* containerBlock,
    TextDirection containerDirection,
    LayoutUnit containerLogicalWidth,
    LayoutUnit bordersPlusPadding,
    const Length& logicalLeft,
    const Length& logicalRight,
    const Length& marginLogicalLeft,
    const Length& marginLogicalRight,
    LogicalExtentComputedValues& computedValues) const {
  LayoutUnit logicalWidthValue;

  ASSERT(widthSizeType == MinSize || widthSizeType == MainOrPreferredSize ||
         !logicalWidth.isAuto());
  if (widthSizeType == MinSize && logicalWidth.isAuto())
    logicalWidthValue = LayoutUnit();
  else if (logicalWidth.isIntrinsic())
    logicalWidthValue =
        computeIntrinsicLogicalWidthUsing(logicalWidth, containerLogicalWidth,
                                          bordersPlusPadding) -
        bordersPlusPadding;
  else
    logicalWidthValue = adjustContentBoxLogicalWidthForBoxSizing(
        valueForLength(logicalWidth, containerLogicalWidth));

  // 'left' and 'right' cannot both be 'auto' because one would of been
  // converted to the static position already
  ASSERT(!(logicalLeft.isAuto() && logicalRight.isAuto()));

  // minimumValueForLength will convert 'auto' to 0 so that it doesn't impact
  // the available space computation below.
  LayoutUnit logicalLeftValue =
      minimumValueForLength(logicalLeft, containerLogicalWidth);
  LayoutUnit logicalRightValue =
      minimumValueForLength(logicalRight, containerLogicalWidth);

  const LayoutUnit containerRelativeLogicalWidth =
      containingBlockLogicalWidthForPositioned(containerBlock, false);

  bool logicalWidthIsAuto = logicalWidth.isAuto();
  bool logicalLeftIsAuto = logicalLeft.isAuto();
  bool logicalRightIsAuto = logicalRight.isAuto();
  LayoutUnit& marginLogicalLeftValue = style()->isLeftToRightDirection()
                                           ? computedValues.m_margins.m_start
                                           : computedValues.m_margins.m_end;
  LayoutUnit& marginLogicalRightValue = style()->isLeftToRightDirection()
                                            ? computedValues.m_margins.m_end
                                            : computedValues.m_margins.m_start;
  if (!logicalLeftIsAuto && !logicalWidthIsAuto && !logicalRightIsAuto) {
    // -------------------------------------------------------------------------
    // If none of the three is 'auto': If both 'margin-left' and 'margin-
    // right' are 'auto', solve the equation under the extra constraint that
    // the two margins get equal values, unless this would make them negative,
    // in which case when direction of the containing block is 'ltr' ('rtl'),
    // set 'margin-left' ('margin-right') to zero and solve for 'margin-right'
    // ('margin-left'). If one of 'margin-left' or 'margin-right' is 'auto',
    // solve the equation for that value. If the values are over-constrained,
    // ignore the value for 'left' (in case the 'direction' property of the
    // containing block is 'rtl') or 'right' (in case 'direction' is 'ltr')
    // and solve for that value.
    // -------------------------------------------------------------------------
    // NOTE:  It is not necessary to solve for 'right' in the over constrained
    // case because the value is not used for any further calculations.

    computedValues.m_extent = logicalWidthValue;

    const LayoutUnit availableSpace =
        containerLogicalWidth - (logicalLeftValue + computedValues.m_extent +
                                 logicalRightValue + bordersPlusPadding);

    // Margins are now the only unknown
    if (marginLogicalLeft.isAuto() && marginLogicalRight.isAuto()) {
      // Both margins auto, solve for equality
      if (availableSpace >= 0) {
        marginLogicalLeftValue = availableSpace / 2;  // split the difference
        marginLogicalRightValue =
            availableSpace -
            marginLogicalLeftValue;  // account for odd valued differences
      } else {
        // Use the containing block's direction rather than the parent block's
        // per CSS 2.1 reference test abspos-non-replaced-width-margin-000.
        if (containerDirection == TextDirection::Ltr) {
          marginLogicalLeftValue = LayoutUnit();
          marginLogicalRightValue = availableSpace;  // will be negative
        } else {
          marginLogicalLeftValue = availableSpace;  // will be negative
          marginLogicalRightValue = LayoutUnit();
        }
      }
    } else if (marginLogicalLeft.isAuto()) {
      // Solve for left margin
      marginLogicalRightValue =
          valueForLength(marginLogicalRight, containerRelativeLogicalWidth);
      marginLogicalLeftValue = availableSpace - marginLogicalRightValue;
    } else if (marginLogicalRight.isAuto()) {
      // Solve for right margin
      marginLogicalLeftValue =
          valueForLength(marginLogicalLeft, containerRelativeLogicalWidth);
      marginLogicalRightValue = availableSpace - marginLogicalLeftValue;
    } else {
      // Over-constrained, solve for left if direction is RTL
      marginLogicalLeftValue =
          valueForLength(marginLogicalLeft, containerRelativeLogicalWidth);
      marginLogicalRightValue =
          valueForLength(marginLogicalRight, containerRelativeLogicalWidth);

      // Use the containing block's direction rather than the parent block's
      // per CSS 2.1 reference test abspos-non-replaced-width-margin-000.
      if (containerDirection == TextDirection::Rtl)
        logicalLeftValue = (availableSpace + logicalLeftValue) -
                           marginLogicalLeftValue - marginLogicalRightValue;
    }
  } else {
    // -------------------------------------------------------------------------
    // Otherwise, set 'auto' values for 'margin-left' and 'margin-right'
    // to 0, and pick the one of the following six rules that applies.
    //
    // 1. 'left' and 'width' are 'auto' and 'right' is not 'auto', then the
    //    width is shrink-to-fit. Then solve for 'left'
    //
    //              OMIT RULE 2 AS IT SHOULD NEVER BE HIT
    // ------------------------------------------------------------------
    // 2. 'left' and 'right' are 'auto' and 'width' is not 'auto', then if
    //    the 'direction' property of the containing block is 'ltr' set
    //    'left' to the static position, otherwise set 'right' to the
    //    static position. Then solve for 'left' (if 'direction is 'rtl')
    //    or 'right' (if 'direction' is 'ltr').
    // ------------------------------------------------------------------
    //
    // 3. 'width' and 'right' are 'auto' and 'left' is not 'auto', then the
    //    width is shrink-to-fit . Then solve for 'right'
    // 4. 'left' is 'auto', 'width' and 'right' are not 'auto', then solve
    //    for 'left'
    // 5. 'width' is 'auto', 'left' and 'right' are not 'auto', then solve
    //    for 'width'
    // 6. 'right' is 'auto', 'left' and 'width' are not 'auto', then solve
    //    for 'right'
    //
    // Calculation of the shrink-to-fit width is similar to calculating the
    // width of a table cell using the automatic table layout algorithm.
    // Roughly: calculate the preferred width by formatting the content without
    // breaking lines other than where explicit line breaks occur, and also
    // calculate the preferred minimum width, e.g., by trying all possible line
    // breaks. CSS 2.1 does not define the exact algorithm.
    // Thirdly, calculate the available width: this is found by solving for
    // 'width' after setting 'left' (in case 1) or 'right' (in case 3) to 0.
    //
    // Then the shrink-to-fit width is:
    // min(max(preferred minimum width, available width), preferred width).
    // -------------------------------------------------------------------------
    // NOTE: For rules 3 and 6 it is not necessary to solve for 'right'
    // because the value is not used for any further calculations.

    // Calculate margins, 'auto' margins are ignored.
    marginLogicalLeftValue =
        minimumValueForLength(marginLogicalLeft, containerRelativeLogicalWidth);
    marginLogicalRightValue = minimumValueForLength(
        marginLogicalRight, containerRelativeLogicalWidth);

    const LayoutUnit availableSpace =
        containerLogicalWidth -
        (marginLogicalLeftValue + marginLogicalRightValue + logicalLeftValue +
         logicalRightValue + bordersPlusPadding);

    // FIXME: Is there a faster way to find the correct case?
    // Use rule/case that applies.
    if (logicalLeftIsAuto && logicalWidthIsAuto && !logicalRightIsAuto) {
      // RULE 1: (use shrink-to-fit for width, and solve of left)
      computedValues.m_extent =
          shrinkToFitLogicalWidth(availableSpace, bordersPlusPadding);
      logicalLeftValue = availableSpace - computedValues.m_extent;
    } else if (!logicalLeftIsAuto && logicalWidthIsAuto && logicalRightIsAuto) {
      // RULE 3: (use shrink-to-fit for width, and no need solve of right)
      computedValues.m_extent =
          shrinkToFitLogicalWidth(availableSpace, bordersPlusPadding);
    } else if (logicalLeftIsAuto && !logicalWidthIsAuto &&
               !logicalRightIsAuto) {
      // RULE 4: (solve for left)
      computedValues.m_extent = logicalWidthValue;
      logicalLeftValue = availableSpace - computedValues.m_extent;
    } else if (!logicalLeftIsAuto && logicalWidthIsAuto &&
               !logicalRightIsAuto) {
      // RULE 5: (solve for width)
      if (autoWidthShouldFitContent())
        computedValues.m_extent =
            shrinkToFitLogicalWidth(availableSpace, bordersPlusPadding);
      else
        computedValues.m_extent = std::max(LayoutUnit(), availableSpace);
    } else if (!logicalLeftIsAuto && !logicalWidthIsAuto &&
               logicalRightIsAuto) {
      // RULE 6: (no need solve for right)
      computedValues.m_extent = logicalWidthValue;
    }
  }

  // Use computed values to calculate the horizontal position.

  // FIXME: This hack is needed to calculate the  logical left position for a
  // 'rtl' relatively positioned, inline because right now, it is using the
  // logical left position of the first line box when really it should use the
  // last line box. When this is fixed elsewhere, this block should be removed.
  if (containerBlock->isLayoutInline() &&
      !containerBlock->style()->isLeftToRightDirection()) {
    const LayoutInline* flow = toLayoutInline(containerBlock);
    InlineFlowBox* firstLine = flow->firstLineBox();
    InlineFlowBox* lastLine = flow->lastLineBox();
    if (firstLine && lastLine && firstLine != lastLine) {
      computedValues.m_position =
          logicalLeftValue + marginLogicalLeftValue +
          lastLine->borderLogicalLeft() +
          (lastLine->logicalLeft() - firstLine->logicalLeft());
      return;
    }
  }

  if (containerBlock->isBox() &&
      toLayoutBox(containerBlock)->scrollsOverflowY() &&
      toLayoutBox(containerBlock)
          ->shouldPlaceBlockDirectionScrollbarOnLogicalLeft()) {
    logicalLeftValue = logicalLeftValue +
                       toLayoutBox(containerBlock)->verticalScrollbarWidth();
  }

  computedValues.m_position = logicalLeftValue + marginLogicalLeftValue;
  computeLogicalLeftPositionedOffset(computedValues.m_position, this,
                                     computedValues.m_extent, containerBlock,
                                     containerLogicalWidth);
}

void LayoutBox::computeBlockStaticDistance(
    Length& logicalTop,
    Length& logicalBottom,
    const LayoutBox* child,
    const LayoutBoxModelObject* containerBlock) {
  if (!logicalTop.isAuto() || !logicalBottom.isAuto())
    return;

  // FIXME: The static distance computation has not been patched for mixed
  // writing modes.
  LayoutUnit staticLogicalTop = child->layer()->staticBlockPosition();
  for (LayoutObject* curr = child->parent(); curr && curr != containerBlock;
       curr = curr->container()) {
    if (!curr->isBox() || curr->isTableRow())
      continue;
    const LayoutBox& box = *toLayoutBox(curr);
    staticLogicalTop += box.logicalTop();
    if (box.isInFlowPositioned())
      staticLogicalTop += box.offsetForInFlowPosition().height();
    if (!box.isLayoutFlowThread())
      continue;
    // We're walking out of a flowthread here. This flow thread is not in the
    // containing block chain, so we need to convert the position from the
    // coordinate space of this flowthread to the containing coordinate space.
    // The inline position cannot affect the block position, so we don't bother
    // calculating it.
    LayoutUnit dummyInlinePosition;
    toLayoutFlowThread(box).flowThreadToContainingCoordinateSpace(
        staticLogicalTop, dummyInlinePosition);
  }
  logicalTop.setValue(Fixed, staticLogicalTop - containerBlock->borderBefore());
}

void LayoutBox::computePositionedLogicalHeight(
    LogicalExtentComputedValues& computedValues) const {
  // The following is based off of the W3C Working Draft from April 11, 2006 of
  // CSS 2.1: Section 10.6.4 "Absolutely positioned, non-replaced elements"
  // <http://www.w3.org/TR/2005/WD-CSS21-20050613/visudet.html#abs-non-replaced-height>
  // (block-style-comments in this function and in
  // computePositionedLogicalHeightUsing()
  // correspond to text from the spec)

  // We don't use containingBlock(), since we may be positioned by an enclosing
  // relpositioned inline.
  const LayoutBoxModelObject* containerBlock =
      toLayoutBoxModelObject(container());

  const LayoutUnit containerLogicalHeight =
      containingBlockLogicalHeightForPositioned(containerBlock);

  const ComputedStyle& styleToUse = styleRef();
  const LayoutUnit bordersPlusPadding = borderAndPaddingLogicalHeight();
  const Length marginBefore = styleToUse.marginBefore();
  const Length marginAfter = styleToUse.marginAfter();
  Length logicalTopLength = styleToUse.logicalTop();
  Length logicalBottomLength = styleToUse.logicalBottom();

  // ---------------------------------------------------------------------------
  // For the purposes of this section and the next, the term "static position"
  // (of an element) refers, roughly, to the position an element would have had
  // in the normal flow. More precisely, the static position for 'top' is the
  // distance from the top edge of the containing block to the top margin edge
  // of a hypothetical box that would have been the first box of the element if
  // its 'position' property had been 'static' and 'float' had been 'none'. The
  // value is negative if the hypothetical box is above the containing block.
  //
  // But rather than actually calculating the dimensions of that hypothetical
  // box, user agents are free to make a guess at its probable position.
  //
  // For the purposes of calculating the static position, the containing block
  // of fixed positioned elements is the initial containing block instead of
  // the viewport.
  // ---------------------------------------------------------------------------
  // see FIXME 1
  // Calculate the static distance if needed.
  computeBlockStaticDistance(logicalTopLength, logicalBottomLength, this,
                             containerBlock);

  // Calculate constraint equation values for 'height' case.
  LayoutUnit logicalHeight = computedValues.m_extent;
  computePositionedLogicalHeightUsing(
      MainOrPreferredSize, styleToUse.logicalHeight(), containerBlock,
      containerLogicalHeight, bordersPlusPadding, logicalHeight,
      logicalTopLength, logicalBottomLength, marginBefore, marginAfter,
      computedValues);

  // Avoid doing any work in the common case (where the values of min-height and
  // max-height are their defaults).
  // see FIXME 2

  // Calculate constraint equation values for 'max-height' case.
  if (!styleToUse.logicalMaxHeight().isMaxSizeNone()) {
    LogicalExtentComputedValues maxValues;

    computePositionedLogicalHeightUsing(MaxSize, styleToUse.logicalMaxHeight(),
                                        containerBlock, containerLogicalHeight,
                                        bordersPlusPadding, logicalHeight,
                                        logicalTopLength, logicalBottomLength,
                                        marginBefore, marginAfter, maxValues);

    if (computedValues.m_extent > maxValues.m_extent) {
      computedValues.m_extent = maxValues.m_extent;
      computedValues.m_position = maxValues.m_position;
      computedValues.m_margins.m_before = maxValues.m_margins.m_before;
      computedValues.m_margins.m_after = maxValues.m_margins.m_after;
    }
  }

  // Calculate constraint equation values for 'min-height' case.
  if (!styleToUse.logicalMinHeight().isZero() ||
      styleToUse.logicalMinHeight().isIntrinsic()) {
    LogicalExtentComputedValues minValues;

    computePositionedLogicalHeightUsing(MinSize, styleToUse.logicalMinHeight(),
                                        containerBlock, containerLogicalHeight,
                                        bordersPlusPadding, logicalHeight,
                                        logicalTopLength, logicalBottomLength,
                                        marginBefore, marginAfter, minValues);

    if (computedValues.m_extent < minValues.m_extent) {
      computedValues.m_extent = minValues.m_extent;
      computedValues.m_position = minValues.m_position;
      computedValues.m_margins.m_before = minValues.m_margins.m_before;
      computedValues.m_margins.m_after = minValues.m_margins.m_after;
    }
  }

  if (!style()->hasStaticBlockPosition(isHorizontalWritingMode()))
    computedValues.m_position += extraBlockOffset();

  // Set final height value.
  computedValues.m_extent += bordersPlusPadding;
}

void LayoutBox::computeLogicalTopPositionedOffset(
    LayoutUnit& logicalTopPos,
    const LayoutBox* child,
    LayoutUnit logicalHeightValue,
    const LayoutBoxModelObject* containerBlock,
    LayoutUnit containerLogicalHeight) {
  // Deal with differing writing modes here. Our offset needs to be in the
  // containing block's coordinate space. If the containing block is flipped
  // along this axis, then we need to flip the coordinate.  This can only happen
  // if the containing block is both a flipped mode and perpendicular to us.
  if ((child->style()->isFlippedBlocksWritingMode() &&
       child->isHorizontalWritingMode() !=
           containerBlock->isHorizontalWritingMode()) ||
      (child->style()->isFlippedBlocksWritingMode() !=
           containerBlock->style()->isFlippedBlocksWritingMode() &&
       child->isHorizontalWritingMode() ==
           containerBlock->isHorizontalWritingMode()))
    logicalTopPos = containerLogicalHeight - logicalHeightValue - logicalTopPos;

  // Our offset is from the logical bottom edge in a flipped environment, e.g.,
  // right for vertical-rl.
  if (containerBlock->style()->isFlippedBlocksWritingMode() &&
      child->isHorizontalWritingMode() ==
          containerBlock->isHorizontalWritingMode()) {
    if (child->isHorizontalWritingMode())
      logicalTopPos += containerBlock->borderBottom();
    else
      logicalTopPos += containerBlock->borderRight();
  } else {
    if (child->isHorizontalWritingMode())
      logicalTopPos += containerBlock->borderTop();
    else
      logicalTopPos += containerBlock->borderLeft();
  }
}

void LayoutBox::computePositionedLogicalHeightUsing(
    SizeType heightSizeType,
    Length logicalHeightLength,
    const LayoutBoxModelObject* containerBlock,
    LayoutUnit containerLogicalHeight,
    LayoutUnit bordersPlusPadding,
    LayoutUnit logicalHeight,
    const Length& logicalTop,
    const Length& logicalBottom,
    const Length& marginBefore,
    const Length& marginAfter,
    LogicalExtentComputedValues& computedValues) const {
  ASSERT(heightSizeType == MinSize || heightSizeType == MainOrPreferredSize ||
         !logicalHeightLength.isAuto());
  if (heightSizeType == MinSize && logicalHeightLength.isAuto())
    logicalHeightLength = Length(0, Fixed);

  // 'top' and 'bottom' cannot both be 'auto' because 'top would of been
  // converted to the static position in computePositionedLogicalHeight()
  ASSERT(!(logicalTop.isAuto() && logicalBottom.isAuto()));

  LayoutUnit logicalHeightValue;
  LayoutUnit contentLogicalHeight = logicalHeight - bordersPlusPadding;

  const LayoutUnit containerRelativeLogicalWidth =
      containingBlockLogicalWidthForPositioned(containerBlock, false);

  LayoutUnit logicalTopValue;

  bool logicalHeightIsAuto = logicalHeightLength.isAuto();
  bool logicalTopIsAuto = logicalTop.isAuto();
  bool logicalBottomIsAuto = logicalBottom.isAuto();

  LayoutUnit resolvedLogicalHeight;
  // Height is never unsolved for tables.
  if (isTable()) {
    resolvedLogicalHeight = contentLogicalHeight;
    logicalHeightIsAuto = false;
  } else {
    if (logicalHeightLength.isIntrinsic())
      resolvedLogicalHeight = computeIntrinsicLogicalContentHeightUsing(
          logicalHeightLength, contentLogicalHeight, bordersPlusPadding);
    else
      resolvedLogicalHeight = adjustContentBoxLogicalHeightForBoxSizing(
          valueForLength(logicalHeightLength, containerLogicalHeight));
  }

  if (!logicalTopIsAuto && !logicalHeightIsAuto && !logicalBottomIsAuto) {
    // -------------------------------------------------------------------------
    // If none of the three are 'auto': If both 'margin-top' and 'margin-bottom'
    // are 'auto', solve the equation under the extra constraint that the two
    // margins get equal values. If one of 'margin-top' or 'margin- bottom' is
    // 'auto', solve the equation for that value. If the values are over-
    // constrained, ignore the value for 'bottom' and solve for that value.
    // -------------------------------------------------------------------------
    // NOTE:  It is not necessary to solve for 'bottom' in the over constrained
    // case because the value is not used for any further calculations.

    logicalHeightValue = resolvedLogicalHeight;
    logicalTopValue = valueForLength(logicalTop, containerLogicalHeight);

    const LayoutUnit availableSpace =
        containerLogicalHeight -
        (logicalTopValue + logicalHeightValue +
         valueForLength(logicalBottom, containerLogicalHeight) +
         bordersPlusPadding);

    // Margins are now the only unknown
    if (marginBefore.isAuto() && marginAfter.isAuto()) {
      // Both margins auto, solve for equality
      // NOTE: This may result in negative values.
      computedValues.m_margins.m_before =
          availableSpace / 2;  // split the difference
      computedValues.m_margins.m_after =
          availableSpace -
          computedValues.m_margins
              .m_before;  // account for odd valued differences
    } else if (marginBefore.isAuto()) {
      // Solve for top margin
      computedValues.m_margins.m_after =
          valueForLength(marginAfter, containerRelativeLogicalWidth);
      computedValues.m_margins.m_before =
          availableSpace - computedValues.m_margins.m_after;
    } else if (marginAfter.isAuto()) {
      // Solve for bottom margin
      computedValues.m_margins.m_before =
          valueForLength(marginBefore, containerRelativeLogicalWidth);
      computedValues.m_margins.m_after =
          availableSpace - computedValues.m_margins.m_before;
    } else {
      // Over-constrained, (no need solve for bottom)
      computedValues.m_margins.m_before =
          valueForLength(marginBefore, containerRelativeLogicalWidth);
      computedValues.m_margins.m_after =
          valueForLength(marginAfter, containerRelativeLogicalWidth);
    }
  } else {
    // -------------------------------------------------------------------------
    // Otherwise, set 'auto' values for 'margin-top' and 'margin-bottom'
    // to 0, and pick the one of the following six rules that applies.
    //
    // 1. 'top' and 'height' are 'auto' and 'bottom' is not 'auto', then
    //    the height is based on the content, and solve for 'top'.
    //
    //              OMIT RULE 2 AS IT SHOULD NEVER BE HIT
    // ------------------------------------------------------------------
    // 2. 'top' and 'bottom' are 'auto' and 'height' is not 'auto', then
    //    set 'top' to the static position, and solve for 'bottom'.
    // ------------------------------------------------------------------
    //
    // 3. 'height' and 'bottom' are 'auto' and 'top' is not 'auto', then
    //    the height is based on the content, and solve for 'bottom'.
    // 4. 'top' is 'auto', 'height' and 'bottom' are not 'auto', and
    //    solve for 'top'.
    // 5. 'height' is 'auto', 'top' and 'bottom' are not 'auto', and
    //    solve for 'height'.
    // 6. 'bottom' is 'auto', 'top' and 'height' are not 'auto', and
    //    solve for 'bottom'.
    // -------------------------------------------------------------------------
    // NOTE: For rules 3 and 6 it is not necessary to solve for 'bottom'
    // because the value is not used for any further calculations.

    // Calculate margins, 'auto' margins are ignored.
    computedValues.m_margins.m_before =
        minimumValueForLength(marginBefore, containerRelativeLogicalWidth);
    computedValues.m_margins.m_after =
        minimumValueForLength(marginAfter, containerRelativeLogicalWidth);

    const LayoutUnit availableSpace =
        containerLogicalHeight -
        (computedValues.m_margins.m_before + computedValues.m_margins.m_after +
         bordersPlusPadding);

    // Use rule/case that applies.
    if (logicalTopIsAuto && logicalHeightIsAuto && !logicalBottomIsAuto) {
      // RULE 1: (height is content based, solve of top)
      logicalHeightValue = contentLogicalHeight;
      logicalTopValue = availableSpace -
                        (logicalHeightValue +
                         valueForLength(logicalBottom, containerLogicalHeight));
    } else if (!logicalTopIsAuto && logicalHeightIsAuto &&
               logicalBottomIsAuto) {
      // RULE 3: (height is content based, no need solve of bottom)
      logicalTopValue = valueForLength(logicalTop, containerLogicalHeight);
      logicalHeightValue = contentLogicalHeight;
    } else if (logicalTopIsAuto && !logicalHeightIsAuto &&
               !logicalBottomIsAuto) {
      // RULE 4: (solve of top)
      logicalHeightValue = resolvedLogicalHeight;
      logicalTopValue = availableSpace -
                        (logicalHeightValue +
                         valueForLength(logicalBottom, containerLogicalHeight));
    } else if (!logicalTopIsAuto && logicalHeightIsAuto &&
               !logicalBottomIsAuto) {
      // RULE 5: (solve of height)
      logicalTopValue = valueForLength(logicalTop, containerLogicalHeight);
      logicalHeightValue =
          std::max(LayoutUnit(),
                   availableSpace -
                       (logicalTopValue +
                        valueForLength(logicalBottom, containerLogicalHeight)));
    } else if (!logicalTopIsAuto && !logicalHeightIsAuto &&
               logicalBottomIsAuto) {
      // RULE 6: (no need solve of bottom)
      logicalHeightValue = resolvedLogicalHeight;
      logicalTopValue = valueForLength(logicalTop, containerLogicalHeight);
    }
  }
  computedValues.m_extent = logicalHeightValue;

  // Use computed values to calculate the vertical position.
  computedValues.m_position =
      logicalTopValue + computedValues.m_margins.m_before;
  computeLogicalTopPositionedOffset(computedValues.m_position, this,
                                    logicalHeightValue, containerBlock,
                                    containerLogicalHeight);
}

LayoutRect LayoutBox::localCaretRect(InlineBox* box,
                                     int caretOffset,
                                     LayoutUnit* extraWidthToEndOfLine) {
  // VisiblePositions at offsets inside containers either a) refer to the
  // positions before/after those containers (tables and select elements) or
  // b) refer to the position inside an empty block.
  // They never refer to children.
  // FIXME: Paint the carets inside empty blocks differently than the carets
  // before/after elements.

  LayoutRect rect(location(), LayoutSize(caretWidth(), size().height()));
  bool ltr =
      box ? box->isLeftToRightDirection() : style()->isLeftToRightDirection();

  if ((!caretOffset) ^ ltr)
    rect.move(LayoutSize(size().width() - caretWidth(), LayoutUnit()));

  if (box) {
    RootInlineBox& rootBox = box->root();
    LayoutUnit top = rootBox.lineTop();
    rect.setY(top);
    rect.setHeight(rootBox.lineBottom() - top);
  }

  // If height of box is smaller than font height, use the latter one,
  // otherwise the caret might become invisible.
  //
  // Also, if the box is not an atomic inline-level element, always use the font
  // height. This prevents the "big caret" bug described in:
  // <rdar://problem/3777804> Deleting all content in a document can result in
  // giant tall-as-window insertion point
  //
  // FIXME: ignoring :first-line, missing good reason to take care of
  const SimpleFontData* fontData = style()->font().primaryFont();
  LayoutUnit fontHeight =
      LayoutUnit(fontData ? fontData->getFontMetrics().height() : 0);
  if (fontHeight > rect.height() || (!isAtomicInlineLevel() && !isTable()))
    rect.setHeight(fontHeight);

  if (extraWidthToEndOfLine)
    *extraWidthToEndOfLine = location().x() + size().width() - rect.maxX();

  // Move to local coords
  rect.moveBy(-location());

  // FIXME: Border/padding should be added for all elements but this workaround
  // is needed because we use offsets inside an "atomic" element to represent
  // positions before and after the element in deprecated editing offsets.
  if (node() &&
      !(editingIgnoresContent(*node()) || isDisplayInsideTable(node()))) {
    rect.setX(rect.x() + borderLeft() + paddingLeft());
    rect.setY(rect.y() + paddingTop() + borderTop());
  }

  if (!isHorizontalWritingMode())
    return rect.transposedRect();

  return rect;
}

PositionWithAffinity LayoutBox::positionForPoint(const LayoutPoint& point) {
  // no children...return this layout object's element, if there is one, and
  // offset 0
  LayoutObject* firstChild = slowFirstChild();
  if (!firstChild)
    return createPositionWithAffinity(
        nonPseudoNode() ? firstPositionInOrBeforeNode(nonPseudoNode())
                        : Position());

  if (isTable() && nonPseudoNode()) {
    LayoutUnit right = size().width() - verticalScrollbarWidth();
    LayoutUnit bottom = size().height() - horizontalScrollbarHeight();

    if (point.x() < 0 || point.x() > right || point.y() < 0 ||
        point.y() > bottom) {
      if (point.x() <= right / 2)
        return createPositionWithAffinity(
            firstPositionInOrBeforeNode(nonPseudoNode()));
      return createPositionWithAffinity(
          lastPositionInOrAfterNode(nonPseudoNode()));
    }
  }

  // Pass off to the closest child.
  LayoutUnit minDist = LayoutUnit::max();
  LayoutBox* closestLayoutObject = nullptr;
  LayoutPoint adjustedPoint = point;
  if (isTableRow())
    adjustedPoint.moveBy(location());

  for (LayoutObject* layoutObject = firstChild; layoutObject;
       layoutObject = layoutObject->nextSibling()) {
    if ((!layoutObject->slowFirstChild() && !layoutObject->isInline() &&
         !layoutObject->isLayoutBlockFlow()) ||
        layoutObject->style()->visibility() != EVisibility::Visible)
      continue;

    if (!layoutObject->isBox())
      continue;

    LayoutBox* layoutBox = toLayoutBox(layoutObject);

    LayoutUnit top = layoutBox->borderTop() + layoutBox->paddingTop() +
                     (isTableRow() ? LayoutUnit() : layoutBox->location().y());
    LayoutUnit bottom = top + layoutBox->contentHeight();
    LayoutUnit left = layoutBox->borderLeft() + layoutBox->paddingLeft() +
                      (isTableRow() ? LayoutUnit() : layoutBox->location().x());
    LayoutUnit right = left + layoutBox->contentWidth();

    if (point.x() <= right && point.x() >= left && point.y() <= top &&
        point.y() >= bottom) {
      if (layoutBox->isTableRow())
        return layoutBox->positionForPoint(point + adjustedPoint -
                                           layoutBox->locationOffset());
      return layoutBox->positionForPoint(point - layoutBox->locationOffset());
    }

    // Find the distance from (x, y) to the box.  Split the space around the box
    // into 8 pieces and use a different compare depending on which piece (x, y)
    // is in.
    LayoutPoint cmp;
    if (point.x() > right) {
      if (point.y() < top)
        cmp = LayoutPoint(right, top);
      else if (point.y() > bottom)
        cmp = LayoutPoint(right, bottom);
      else
        cmp = LayoutPoint(right, point.y());
    } else if (point.x() < left) {
      if (point.y() < top)
        cmp = LayoutPoint(left, top);
      else if (point.y() > bottom)
        cmp = LayoutPoint(left, bottom);
      else
        cmp = LayoutPoint(left, point.y());
    } else {
      if (point.y() < top)
        cmp = LayoutPoint(point.x(), top);
      else
        cmp = LayoutPoint(point.x(), bottom);
    }

    LayoutSize difference = cmp - point;

    LayoutUnit dist = difference.width() * difference.width() +
                      difference.height() * difference.height();
    if (dist < minDist) {
      closestLayoutObject = layoutBox;
      minDist = dist;
    }
  }

  if (closestLayoutObject)
    return closestLayoutObject->positionForPoint(
        adjustedPoint - closestLayoutObject->locationOffset());
  return createPositionWithAffinity(
      firstPositionInOrBeforeNode(nonPseudoNode()));
}

DISABLE_CFI_PERF
bool LayoutBox::shrinkToAvoidFloats() const {
  // Floating objects don't shrink.  Objects that don't avoid floats don't
  // shrink.
  if (isInline() || !avoidsFloats() || isFloating())
    return false;

  // Only auto width objects can possibly shrink to avoid floats.
  return style()->width().isAuto();
}

DISABLE_CFI_PERF
bool LayoutBox::shouldBeConsideredAsReplaced() const {
  // Checkboxes and radioboxes are not isAtomicInlineLevel() nor do they have
  // their own layoutObject in which to override avoidFloats().
  if (isAtomicInlineLevel())
    return true;
  Node* node = this->node();
  return node && node->isElementNode() &&
         (toElement(node)->isFormControlElement() ||
          isHTMLImageElement(toElement(node)));
}

DISABLE_CFI_PERF
bool LayoutBox::avoidsFloats() const {
  return shouldBeConsideredAsReplaced() || hasOverflowClip() || isHR() ||
         isLegend() || isWritingModeRoot() || isFlexItemIncludingDeprecated() ||
         style()->containsPaint() || style()->containsLayout();
}

bool LayoutBox::hasNonCompositedScrollbars() const {
  if (PaintLayerScrollableArea* scrollableArea = this->getScrollableArea()) {
    if (scrollableArea->hasHorizontalScrollbar() &&
        !scrollableArea->layerForHorizontalScrollbar())
      return true;
    if (scrollableArea->hasVerticalScrollbar() &&
        !scrollableArea->layerForVerticalScrollbar())
      return true;
  }
  return false;
}

void LayoutBox::updateFragmentationInfoForChild(LayoutBox& child) {
  LayoutState* layoutState = view()->layoutState();
  DCHECK(layoutState->isPaginated());
  child.setOffsetToNextPage(LayoutUnit());
  if (!pageLogicalHeightForOffset(child.logicalTop()))
    return;

  LayoutUnit logicalTop = child.logicalTop();
  LayoutUnit logicalHeight = child.logicalHeightWithVisibleOverflow();
  LayoutUnit spaceLeft =
      pageRemainingLogicalHeightForOffset(logicalTop, AssociateWithLatterPage);
  if (spaceLeft < logicalHeight)
    child.setOffsetToNextPage(spaceLeft);
}

bool LayoutBox::childNeedsRelayoutForPagination(const LayoutBox& child) const {
  // TODO(mstensho): Should try to get this to work for floats too, instead of
  // just marking and bailing here.
  if (child.isFloating())
    return true;
  const LayoutFlowThread* flowThread = child.flowThreadContainingBlock();
  LayoutUnit logicalTop = child.logicalTop();
  // Figure out if we really need to force re-layout of the child. We only need
  // to do this if there's a chance that we need to recalculate pagination
  // struts inside.
  if (LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(logicalTop)) {
    LayoutUnit logicalHeight = child.logicalHeightWithVisibleOverflow();
    LayoutUnit remainingSpace = pageRemainingLogicalHeightForOffset(
        logicalTop, AssociateWithLatterPage);
    if (child.offsetToNextPage()) {
      // We need to relayout unless we're going to break at the exact same
      // location as before.
      if (child.offsetToNextPage() != remainingSpace)
        return true;
      // If column height isn't guaranteed to be uniform, we have no way of
      // telling what has happened after the first break.
      if (flowThread && flowThread->mayHaveNonUniformPageLogicalHeight())
        return true;
    } else if (logicalHeight > remainingSpace) {
      // Last time we laid out this child, we didn't need to break, but now we
      // have to. So we need to relayout.
      return true;
    }
  } else if (child.offsetToNextPage()) {
    // This child did previously break, but it won't anymore, because we no
    // longer have a known fragmentainer height.
    return true;
  }

  // It seems that we can skip layout of this child, but we need to ask the flow
  // thread for permission first. We currently cannot skip over objects
  // containing column spanners.
  return flowThread && !flowThread->canSkipLayout(child);
}

void LayoutBox::markChildForPaginationRelayoutIfNeeded(
    LayoutBox& child,
    SubtreeLayoutScope& layoutScope) {
  DCHECK(!child.needsLayout());
  LayoutState* layoutState = view()->layoutState();

  if (layoutState->paginationStateChanged() ||
      (layoutState->isPaginated() && childNeedsRelayoutForPagination(child)))
    layoutScope.setChildNeedsLayout(&child);
}

void LayoutBox::markOrthogonalWritingModeRoot() {
  ASSERT(frameView());
  frameView()->addOrthogonalWritingModeRoot(*this);
}

void LayoutBox::unmarkOrthogonalWritingModeRoot() {
  ASSERT(frameView());
  frameView()->removeOrthogonalWritingModeRoot(*this);
}

void LayoutBox::addVisualEffectOverflow() {
  if (!style()->hasVisualOverflowingEffect())
    return;

  // Add in the final overflow with shadows, outsets and outline combined.
  LayoutRect visualEffectOverflow = borderBoxRect();
  visualEffectOverflow.expand(computeVisualEffectOverflowOutsets());
  addSelfVisualOverflow(visualEffectOverflow);
}

LayoutRectOutsets LayoutBox::computeVisualEffectOverflowOutsets() const {
  ASSERT(style()->hasVisualOverflowingEffect());

  LayoutUnit top;
  LayoutUnit right;
  LayoutUnit bottom;
  LayoutUnit left;

  if (const ShadowList* boxShadow = style()->boxShadow()) {
    // FIXME: Use LayoutUnit edge outsets, and then simplify this.
    FloatRectOutsets outsets = boxShadow->rectOutsetsIncludingOriginal();
    top = LayoutUnit(outsets.top());
    right = LayoutUnit(outsets.right());
    bottom = LayoutUnit(outsets.bottom());
    left = LayoutUnit(outsets.left());
  }

  if (style()->hasBorderImageOutsets()) {
    LayoutRectOutsets borderOutsets = style()->borderImageOutsets();
    top = std::max(top, borderOutsets.top());
    right = std::max(right, borderOutsets.right());
    bottom = std::max(bottom, borderOutsets.bottom());
    left = std::max(left, borderOutsets.left());
  }

  // Box-shadow and border-image-outsets are in physical direction. Flip into
  // block direction.
  if (UNLIKELY(hasFlippedBlocksWritingMode()))
    std::swap(left, right);

  if (style()->hasOutline()) {
    Vector<LayoutRect> outlineRects;
    // The result rects are in coordinates of this object's border box.
    addOutlineRects(outlineRects, LayoutPoint(),
                    outlineRectsShouldIncludeBlockVisualOverflow());
    LayoutRect rect = unionRectEvenIfEmpty(outlineRects);
    int outlineOutset = style()->outlineOutsetExtent();
    top = std::max(top, -rect.y() + outlineOutset);
    right = std::max(right, rect.maxX() - size().width() + outlineOutset);
    bottom = std::max(bottom, rect.maxY() - size().height() + outlineOutset);
    left = std::max(left, -rect.x() + outlineOutset);
  }

  return LayoutRectOutsets(top, right, bottom, left);
}

DISABLE_CFI_PERF
void LayoutBox::addOverflowFromChild(LayoutBox* child,
                                     const LayoutSize& delta) {
  // Never allow flow threads to propagate overflow up to a parent.
  if (child->isLayoutFlowThread())
    return;

  // Only propagate layout overflow from the child if the child isn't clipping
  // its overflow.  If it is, then its overflow is internal to it, and we don't
  // care about it. layoutOverflowRectForPropagation takes care of this and just
  // propagates the border box rect instead.
  LayoutRect childLayoutOverflowRect =
      child->layoutOverflowRectForPropagation(styleRef());
  childLayoutOverflowRect.move(delta);
  addLayoutOverflow(childLayoutOverflowRect);

  // Add in visual overflow from the child.  Even if the child clips its
  // overflow, it may still have visual overflow of its own set from box shadows
  // or reflections. It is unnecessary to propagate this overflow if we are
  // clipping our own overflow.
  if (child->hasSelfPaintingLayer())
    return;
  LayoutRect childVisualOverflowRect =
      child->visualOverflowRectForPropagation(styleRef());
  childVisualOverflowRect.move(delta);
  addContentsVisualOverflow(childVisualOverflowRect);
}

bool LayoutBox::hasTopOverflow() const {
  return !style()->isLeftToRightDirection() && !isHorizontalWritingMode();
}

bool LayoutBox::hasLeftOverflow() const {
  return !style()->isLeftToRightDirection() && isHorizontalWritingMode();
}

DISABLE_CFI_PERF
void LayoutBox::addLayoutOverflow(const LayoutRect& rect) {
  if (rect.isEmpty())
    return;

  LayoutRect clientBox = noOverflowRect();
  if (clientBox.contains(rect))
    return;

  // For overflow clip objects, we don't want to propagate overflow into
  // unreachable areas.
  LayoutRect overflowRect(rect);
  if (hasOverflowClip() || isLayoutView()) {
    // Overflow is in the block's coordinate space and thus is flipped for
    // vertical-rl writing
    // mode.  At this stage that is actually a simplification, since we can
    // treat vertical-lr/rl
    // as the same.
    if (hasTopOverflow())
      overflowRect.shiftMaxYEdgeTo(
          std::min(overflowRect.maxY(), clientBox.maxY()));
    else
      overflowRect.shiftYEdgeTo(std::max(overflowRect.y(), clientBox.y()));
    if (hasLeftOverflow())
      overflowRect.shiftMaxXEdgeTo(
          std::min(overflowRect.maxX(), clientBox.maxX()));
    else
      overflowRect.shiftXEdgeTo(std::max(overflowRect.x(), clientBox.x()));

    // Now re-test with the adjusted rectangle and see if it has become
    // unreachable or fully
    // contained.
    if (clientBox.contains(overflowRect) || overflowRect.isEmpty())
      return;
  }

  if (!m_overflow) {
    m_overflow =
        WTF::wrapUnique(new BoxOverflowModel(clientBox, borderBoxRect()));
  }

  m_overflow->addLayoutOverflow(overflowRect);
}

void LayoutBox::addSelfVisualOverflow(const LayoutRect& rect) {
  if (rect.isEmpty())
    return;

  LayoutRect borderBox = borderBoxRect();
  if (borderBox.contains(rect))
    return;

  if (!m_overflow) {
    m_overflow =
        WTF::wrapUnique(new BoxOverflowModel(noOverflowRect(), borderBox));
  }

  m_overflow->addSelfVisualOverflow(rect);
}

void LayoutBox::addContentsVisualOverflow(const LayoutRect& rect) {
  if (rect.isEmpty())
    return;

  // If hasOverflowClip() we always save contents visual overflow because we
  // need it
  // e.g. to determine whether to apply rounded corner clip on contents.
  // Otherwise we save contents visual overflow only if it overflows the border
  // box.
  LayoutRect borderBox = borderBoxRect();
  if (!hasOverflowClip() && borderBox.contains(rect))
    return;

  if (!m_overflow) {
    m_overflow =
        WTF::wrapUnique(new BoxOverflowModel(noOverflowRect(), borderBox));
  }
  m_overflow->addContentsVisualOverflow(rect);
}

void LayoutBox::clearLayoutOverflow() {
  if (!m_overflow)
    return;

  if (!hasSelfVisualOverflow() && contentsVisualOverflowRect().isEmpty()) {
    clearAllOverflows();
    return;
  }

  m_overflow->setLayoutOverflow(noOverflowRect());
}

bool LayoutBox::percentageLogicalHeightIsResolvable() const {
  Length fakeLength(100, Percent);
  return computePercentageLogicalHeight(fakeLength) != -1;
}

DISABLE_CFI_PERF
bool LayoutBox::hasUnsplittableScrollingOverflow() const {
  // We will paginate as long as we don't scroll overflow in the pagination
  // direction.
  bool isHorizontal = isHorizontalWritingMode();
  if ((isHorizontal && !scrollsOverflowY()) ||
      (!isHorizontal && !scrollsOverflowX()))
    return false;

  // Fragmenting scrollbars is only problematic in interactive media, e.g.
  // multicol on a screen. If we're printing, which is non-interactive media, we
  // should allow objects with non-visible overflow to be paginated as normally.
  if (document().printing())
    return false;

  // We do have overflow. We'll still be willing to paginate as long as the
  // block has auto logical height, auto or undefined max-logical-height and a
  // zero or auto min-logical-height.
  // Note this is just a heuristic, and it's still possible to have overflow
  // under these conditions, but it should work out to be good enough for common
  // cases. Paginating overflow with scrollbars present is not the end of the
  // world and is what we used to do in the old model anyway.
  return !style()->logicalHeight().isIntrinsicOrAuto() ||
         (!style()->logicalMaxHeight().isIntrinsicOrAuto() &&
          !style()->logicalMaxHeight().isMaxSizeNone() &&
          (!style()->logicalMaxHeight().isPercentOrCalc() ||
           percentageLogicalHeightIsResolvable())) ||
         (!style()->logicalMinHeight().isIntrinsicOrAuto() &&
          style()->logicalMinHeight().isPositive() &&
          (!style()->logicalMinHeight().isPercentOrCalc() ||
           percentageLogicalHeightIsResolvable()));
}

LayoutBox::PaginationBreakability LayoutBox::getPaginationBreakability() const {
  // TODO(mstensho): It is wrong to check isAtomicInlineLevel() as we
  // actually look for replaced elements.
  if (isAtomicInlineLevel() || hasUnsplittableScrollingOverflow() ||
      (parent() && isWritingModeRoot()) ||
      (isOutOfFlowPositioned() && style()->position() == FixedPosition))
    return ForbidBreaks;

  EBreak breakValue = breakInside();
  if (breakValue == BreakAvoid || breakValue == BreakAvoidPage ||
      breakValue == BreakAvoidColumn)
    return AvoidBreaks;
  return AllowAnyBreaks;
}

LayoutUnit LayoutBox::lineHeight(bool /*firstLine*/,
                                 LineDirectionMode direction,
                                 LinePositionMode /*linePositionMode*/) const {
  if (isAtomicInlineLevel())
    return direction == HorizontalLine ? marginHeight() + size().height()
                                       : marginWidth() + size().width();
  return LayoutUnit();
}

DISABLE_CFI_PERF
int LayoutBox::baselinePosition(FontBaseline baselineType,
                                bool /*firstLine*/,
                                LineDirectionMode direction,
                                LinePositionMode linePositionMode) const {
  ASSERT(linePositionMode == PositionOnContainingLine);
  if (isAtomicInlineLevel()) {
    int result = direction == HorizontalLine
                     ? roundToInt(marginHeight() + size().height())
                     : roundToInt(marginWidth() + size().width());
    if (baselineType == AlphabeticBaseline)
      return result;
    return result - result / 2;
  }
  return 0;
}

PaintLayer* LayoutBox::enclosingFloatPaintingLayer() const {
  const LayoutObject* curr = this;
  while (curr) {
    PaintLayer* layer =
        curr->hasLayer() && curr->isBox() ? toLayoutBox(curr)->layer() : 0;
    if (layer && layer->isSelfPaintingLayer())
      return layer;
    curr = curr->parent();
  }
  return nullptr;
}

LayoutRect LayoutBox::logicalVisualOverflowRectForPropagation(
    const ComputedStyle& parentStyle) const {
  LayoutRect rect = visualOverflowRectForPropagation(parentStyle);
  if (!parentStyle.isHorizontalWritingMode())
    return rect.transposedRect();
  return rect;
}

DISABLE_CFI_PERF
LayoutRect LayoutBox::visualOverflowRectForPropagation(
    const ComputedStyle& parentStyle) const {
  // If the writing modes of the child and parent match, then we don't have to
  // do anything fancy. Just return the result.
  LayoutRect rect = visualOverflowRect();
  if (parentStyle.getWritingMode() == style()->getWritingMode())
    return rect;

  // We are putting ourselves into our parent's coordinate space. If there is a
  // flipped block mismatch in a particular axis, then we have to flip the rect
  // along that axis.
  if (isFlippedBlocksWritingMode(style()->getWritingMode()) ||
      isFlippedBlocksWritingMode(parentStyle.getWritingMode()))
    rect.setX(size().width() - rect.maxX());

  return rect;
}

DISABLE_CFI_PERF
LayoutRect LayoutBox::logicalLayoutOverflowRectForPropagation(
    const ComputedStyle& parentStyle) const {
  LayoutRect rect = layoutOverflowRectForPropagation(parentStyle);
  if (!parentStyle.isHorizontalWritingMode())
    return rect.transposedRect();
  return rect;
}

DISABLE_CFI_PERF
LayoutRect LayoutBox::layoutOverflowRectForPropagation(
    const ComputedStyle& parentStyle) const {
  // Only propagate interior layout overflow if we don't clip it.
  LayoutRect rect = borderBoxRect();
  // We want to include the margin, but only when it adds height. Quirky margins
  // don't contribute height nor do the margins of self-collapsing blocks.
  if (!styleRef().hasMarginAfterQuirk() && !isSelfCollapsingBlock())
    rect.expand(isHorizontalWritingMode()
                    ? LayoutSize(LayoutUnit(), marginAfter())
                    : LayoutSize(marginAfter(), LayoutUnit()));

  if (!hasOverflowClip())
    rect.unite(layoutOverflowRect());

  bool hasTransform = hasLayer() && layer()->transform();
  if (isInFlowPositioned() || hasTransform) {
    // If we are relatively positioned or if we have a transform, then we have
    // to convert this rectangle into physical coordinates, apply relative
    // positioning and transforms to it, and then convert it back.
    flipForWritingMode(rect);

    if (hasTransform)
      rect = layer()->currentTransform().mapRect(rect);

    if (isInFlowPositioned())
      rect.move(offsetForInFlowPosition());

    // Now we need to flip back.
    flipForWritingMode(rect);
  }

  // If the writing modes of the child and parent match, then we don't have to
  // do anything fancy. Just return the result.
  if (parentStyle.getWritingMode() == style()->getWritingMode())
    return rect;

  // We are putting ourselves into our parent's coordinate space. If there is a
  // flipped block mismatch in a particular axis, then we have to flip the rect
  // along that axis.
  if (isFlippedBlocksWritingMode(style()->getWritingMode()) ||
      isFlippedBlocksWritingMode(parentStyle.getWritingMode()))
    rect.setX(size().width() - rect.maxX());

  return rect;
}

DISABLE_CFI_PERF
LayoutRect LayoutBox::noOverflowRect() const {
  // Because of the special coordinate system used for overflow rectangles and
  // many other rectangles (not quite logical, not quite physical), we need to
  // flip the block progression coordinate in vertical-rl writing mode. In other
  // words, the rectangle returned is physical, except for the block direction
  // progression coordinate (x in vertical writing mode), which is always
  // "logical top". Apart from the flipping, this method does the same thing as
  // clientBoxRect().

  const int scrollBarWidth = verticalScrollbarWidth();
  const int scrollBarHeight = horizontalScrollbarHeight();
  LayoutUnit left(
      borderLeft() +
      (shouldPlaceBlockDirectionScrollbarOnLogicalLeft() ? scrollBarWidth : 0));
  LayoutUnit top(borderTop());
  LayoutUnit right(borderRight());
  LayoutUnit bottom(borderBottom());
  LayoutRect rect(left, top, size().width() - left - right,
                  size().height() - top - bottom);
  flipForWritingMode(rect);
  // Subtract space occupied by scrollbars. Order is important here: first flip,
  // then subtract scrollbars. This may seem backwards and weird, since one
  // would think that a vertical scrollbar at the physical right in vertical-rl
  // ought to be at the logical left (physical right), between the logical left
  // (physical right) border and the logical left (physical right) padding. But
  // this is how the rest of the code expects us to behave. This is highly
  // related to https://bugs.webkit.org/show_bug.cgi?id=76129
  // FIXME: when the above mentioned bug is fixed, it should hopefully be
  // possible to call clientBoxRect() or paddingBoxRect() in this method, rather
  // than fiddling with the edges on our own.
  if (shouldPlaceBlockDirectionScrollbarOnLogicalLeft())
    rect.contract(0, scrollBarHeight);
  else
    rect.contract(scrollBarWidth, scrollBarHeight);
  return rect;
}

LayoutRect LayoutBox::visualOverflowRect() const {
  if (!m_overflow)
    return borderBoxRect();
  if (hasOverflowClip())
    return m_overflow->selfVisualOverflowRect();
  return unionRect(m_overflow->selfVisualOverflowRect(),
                   m_overflow->contentsVisualOverflowRect());
}

LayoutUnit LayoutBox::offsetLeft(const Element* parent) const {
  return adjustedPositionRelativeTo(physicalLocation(), parent).x();
}

LayoutUnit LayoutBox::offsetTop(const Element* parent) const {
  return adjustedPositionRelativeTo(physicalLocation(), parent).y();
}

LayoutPoint LayoutBox::flipForWritingModeForChild(
    const LayoutBox* child,
    const LayoutPoint& point) const {
  if (!style()->isFlippedBlocksWritingMode())
    return point;

  // The child is going to add in its x(), so we have to make sure it ends up in
  // the right place.
  return LayoutPoint(point.x() + size().width() - child->size().width() -
                         (2 * child->location().x()),
                     point.y());
}

LayoutBox* LayoutBox::locationContainer() const {
  // Location of a non-root SVG object derived from LayoutBox should not be
  // affected by writing-mode of the containing box (SVGRoot).
  if (isSVG() && !isSVGRoot())
    return nullptr;

  // Normally the box's location is relative to its containing box.
  LayoutObject* container = this->container();
  while (container && !container->isBox())
    container = container->container();
  return toLayoutBox(container);
}

LayoutPoint LayoutBox::physicalLocation(
    const LayoutBox* flippedBlocksContainer) const {
  const LayoutBox* containerBox;
  if (flippedBlocksContainer) {
    DCHECK(flippedBlocksContainer == locationContainer());
    containerBox = flippedBlocksContainer;
  } else {
    containerBox = locationContainer();
  }
  if (!containerBox)
    return location();
  return containerBox->flipForWritingModeForChild(this, location());
}

bool LayoutBox::hasRelativeLogicalWidth() const {
  return style()->logicalWidth().isPercentOrCalc() ||
         style()->logicalMinWidth().isPercentOrCalc() ||
         style()->logicalMaxWidth().isPercentOrCalc();
}

bool LayoutBox::hasRelativeLogicalHeight() const {
  return style()->logicalHeight().isPercentOrCalc() ||
         style()->logicalMinHeight().isPercentOrCalc() ||
         style()->logicalMaxHeight().isPercentOrCalc();
}

static void markBoxForRelayoutAfterSplit(LayoutBox* box) {
  // FIXME: The table code should handle that automatically. If not,
  // we should fix it and remove the table part checks.
  if (box->isTable()) {
    // Because we may have added some sections with already computed column
    // structures, we need to sync the table structure with them now. This
    // avoids crashes when adding new cells to the table.
    toLayoutTable(box)->forceSectionsRecalc();
  } else if (box->isTableSection()) {
    toLayoutTableSection(box)->setNeedsCellRecalc();
  }

  box->setNeedsLayoutAndPrefWidthsRecalcAndFullPaintInvalidation(
      LayoutInvalidationReason::AnonymousBlockChange);
}

static void collapseLoneAnonymousBlockChild(LayoutBox* parent,
                                            LayoutObject* child) {
  if (!child->isAnonymousBlock() || !child->isLayoutBlockFlow())
    return;
  if (!parent->isLayoutBlockFlow())
    return;
  toLayoutBlockFlow(parent)->collapseAnonymousBlockChild(
      toLayoutBlockFlow(child));
}

LayoutObject* LayoutBox::splitAnonymousBoxesAroundChild(
    LayoutObject* beforeChild) {
  LayoutBox* boxAtTopOfNewBranch = nullptr;

  while (beforeChild->parent() != this) {
    LayoutBox* boxToSplit = toLayoutBox(beforeChild->parent());
    if (boxToSplit->slowFirstChild() != beforeChild &&
        boxToSplit->isAnonymous()) {
      // We have to split the parent box into two boxes and move children
      // from |beforeChild| to end into the new post box.
      LayoutBox* postBox = boxToSplit->createAnonymousBoxWithSameTypeAs(this);
      postBox->setChildrenInline(boxToSplit->childrenInline());
      LayoutBox* parentBox = toLayoutBox(boxToSplit->parent());
      // We need to invalidate the |parentBox| before inserting the new node
      // so that the table paint invalidation logic knows the structure is
      // dirty. See for example LayoutTableCell:localVisualRect().
      markBoxForRelayoutAfterSplit(parentBox);
      parentBox->virtualChildren()->insertChildNode(parentBox, postBox,
                                                    boxToSplit->nextSibling());
      boxToSplit->moveChildrenTo(postBox, beforeChild, 0, true);

      LayoutObject* child = postBox->slowFirstChild();
      ASSERT(child);
      if (child && !child->nextSibling())
        collapseLoneAnonymousBlockChild(postBox, child);
      child = boxToSplit->slowFirstChild();
      ASSERT(child);
      if (child && !child->nextSibling())
        collapseLoneAnonymousBlockChild(boxToSplit, child);

      markBoxForRelayoutAfterSplit(boxToSplit);
      markBoxForRelayoutAfterSplit(postBox);
      boxAtTopOfNewBranch = postBox;

      beforeChild = postBox;
    } else {
      beforeChild = boxToSplit;
    }
  }

  // Splitting the box means the left side of the container chain will lose any
  // percent height descendants below |boxAtTopOfNewBranch| on the right hand
  // side.
  if (boxAtTopOfNewBranch) {
    boxAtTopOfNewBranch->clearPercentHeightDescendants();
    markBoxForRelayoutAfterSplit(this);
  }

  ASSERT(beforeChild->parent() == this);
  return beforeChild;
}

LayoutUnit LayoutBox::offsetFromLogicalTopOfFirstPage() const {
  LayoutState* layoutState = view()->layoutState();
  if (!layoutState || !layoutState->isPaginated())
    return LayoutUnit();

  if (layoutState->layoutObject() == this) {
    LayoutSize offset = layoutState->paginationOffset();
    return isHorizontalWritingMode() ? offset.height() : offset.width();
  }

  // A LayoutBlock always establishes a layout state, and this method is only
  // meant to be called on the object currently being laid out.
  ASSERT(!isLayoutBlock());

  // In case this box doesn't establish a layout state, try the containing
  // block.
  LayoutBlock* containerBlock = containingBlock();
  ASSERT(layoutState->layoutObject() == containerBlock);
  return containerBlock->offsetFromLogicalTopOfFirstPage() + logicalTop();
}

void LayoutBox::setOffsetToNextPage(LayoutUnit offset) {
  if (!m_rareData && !offset)
    return;
  ensureRareData().m_offsetToNextPage = offset;
}

void LayoutBox::logicalExtentAfterUpdatingLogicalWidth(
    const LayoutUnit& newLogicalTop,
    LayoutBox::LogicalExtentComputedValues& computedValues) {
  // FIXME: None of this is right for perpendicular writing-mode children.
  LayoutUnit oldLogicalWidth = logicalWidth();
  LayoutUnit oldLogicalLeft = logicalLeft();
  LayoutUnit oldMarginLeft = marginLeft();
  LayoutUnit oldMarginRight = marginRight();
  LayoutUnit oldLogicalTop = logicalTop();

  setLogicalTop(newLogicalTop);
  updateLogicalWidth();

  computedValues.m_extent = logicalWidth();
  computedValues.m_position = logicalLeft();
  computedValues.m_margins.m_start = marginStart();
  computedValues.m_margins.m_end = marginEnd();

  setLogicalTop(oldLogicalTop);
  setLogicalWidth(oldLogicalWidth);
  setLogicalLeft(oldLogicalLeft);
  setMarginLeft(oldMarginLeft);
  setMarginRight(oldMarginRight);
}

bool LayoutBox::mustInvalidateFillLayersPaintOnHeightChange(
    const FillLayer& layer) {
  // Nobody will use multiple layers without wanting fancy positioning.
  if (layer.next())
    return true;

  // Make sure we have a valid image.
  StyleImage* img = layer.image();
  if (!img || !img->canRender())
    return false;

  if (layer.repeatY() != RepeatFill && layer.repeatY() != NoRepeatFill)
    return true;

  // TODO(alancutter): Make this work correctly for calc lengths.
  if (layer.yPosition().isPercentOrCalc() && !layer.yPosition().isZero())
    return true;

  if (layer.backgroundYOrigin() != TopEdge)
    return true;

  EFillSizeType sizeType = layer.sizeType();

  if (sizeType == Contain || sizeType == Cover)
    return true;

  if (sizeType == SizeLength) {
    // TODO(alancutter): Make this work correctly for calc lengths.
    if (layer.sizeLength().height().isPercentOrCalc() &&
        !layer.sizeLength().height().isZero())
      return true;
    if (img->isGeneratedImage() && layer.sizeLength().height().isAuto())
      return true;
  } else if (img->usesImageContainerSize()) {
    return true;
  }

  return false;
}

bool LayoutBox::mustInvalidateFillLayersPaintOnWidthChange(
    const FillLayer& layer) {
  // Nobody will use multiple layers without wanting fancy positioning.
  if (layer.next())
    return true;

  // Make sure we have a valid image.
  StyleImage* img = layer.image();
  if (!img || !img->canRender())
    return false;

  if (layer.repeatX() != RepeatFill && layer.repeatX() != NoRepeatFill)
    return true;

  // TODO(alancutter): Make this work correctly for calc lengths.
  if (layer.xPosition().isPercentOrCalc() && !layer.xPosition().isZero())
    return true;

  if (layer.backgroundXOrigin() != LeftEdge)
    return true;

  EFillSizeType sizeType = layer.sizeType();

  if (sizeType == Contain || sizeType == Cover)
    return true;

  if (sizeType == SizeLength) {
    // TODO(alancutter): Make this work correctly for calc lengths.
    if (layer.sizeLength().width().isPercentOrCalc() &&
        !layer.sizeLength().width().isZero())
      return true;
    if (img->isGeneratedImage() && layer.sizeLength().width().isAuto())
      return true;
  } else if (img->usesImageContainerSize()) {
    return true;
  }

  return false;
}

bool LayoutBox::mustInvalidateBackgroundOrBorderPaintOnWidthChange() const {
  if (hasMask() &&
      mustInvalidateFillLayersPaintOnWidthChange(style()->maskLayers()))
    return true;

  // If we don't have a background/border/mask, then nothing to do.
  if (!hasBoxDecorationBackground())
    return false;

  if (mustInvalidateFillLayersPaintOnWidthChange(style()->backgroundLayers()))
    return true;

  // Our fill layers are ok. Let's check border.
  if (style()->hasBorderDecoration() && canRenderBorderImage())
    return true;

  return false;
}

bool LayoutBox::mustInvalidateBackgroundOrBorderPaintOnHeightChange() const {
  if (hasMask() &&
      mustInvalidateFillLayersPaintOnHeightChange(style()->maskLayers()))
    return true;

  // If we don't have a background/border/mask, then nothing to do.
  if (!hasBoxDecorationBackground())
    return false;

  if (mustInvalidateFillLayersPaintOnHeightChange(style()->backgroundLayers()))
    return true;

  // Our fill layers are ok.  Let's check border.
  if (style()->hasBorderDecoration() && canRenderBorderImage())
    return true;

  return false;
}

bool LayoutBox::canRenderBorderImage() const {
  if (!style()->hasBorderDecoration())
    return false;

  StyleImage* borderImage = style()->borderImage().image();
  return borderImage && borderImage->canRender() && borderImage->isLoaded();
}

ShapeOutsideInfo* LayoutBox::shapeOutsideInfo() const {
  return ShapeOutsideInfo::isEnabledFor(*this) ? ShapeOutsideInfo::info(*this)
                                               : nullptr;
}

void LayoutBox::clearPreviousVisualRects() {
  LayoutBoxModelObject::clearPreviousVisualRects();
  if (PaintLayerScrollableArea* scrollableArea = this->getScrollableArea())
    scrollableArea->clearPreviousVisualRects();
}

void LayoutBox::setPercentHeightContainer(LayoutBlock* container) {
  ASSERT(!container || !percentHeightContainer());
  if (!container && !m_rareData)
    return;
  ensureRareData().m_percentHeightContainer = container;
}

void LayoutBox::removeFromPercentHeightContainer() {
  if (!percentHeightContainer())
    return;

  ASSERT(percentHeightContainer()->hasPercentHeightDescendant(this));
  percentHeightContainer()->removePercentHeightDescendant(this);
  // The above call should call this object's
  // setPercentHeightContainer(nullptr).
  ASSERT(!percentHeightContainer());
}

void LayoutBox::clearPercentHeightDescendants() {
  for (LayoutObject* curr = slowFirstChild(); curr;
       curr = curr->nextInPreOrder(this)) {
    if (curr->isBox())
      toLayoutBox(curr)->removeFromPercentHeightContainer();
  }
}

LayoutUnit LayoutBox::pageLogicalHeightForOffset(LayoutUnit offset) const {
  LayoutView* layoutView = view();
  LayoutFlowThread* flowThread = flowThreadContainingBlock();
  if (!flowThread)
    return layoutView->pageLogicalHeight();
  return flowThread->pageLogicalHeightForOffset(
      offset + offsetFromLogicalTopOfFirstPage());
}

bool LayoutBox::isPageLogicalHeightKnown() const {
  if (const LayoutFlowThread* flowThread = flowThreadContainingBlock())
    return flowThread->isPageLogicalHeightKnown();
  return view()->pageLogicalHeight();
}

LayoutUnit LayoutBox::pageRemainingLogicalHeightForOffset(
    LayoutUnit offset,
    PageBoundaryRule pageBoundaryRule) const {
  LayoutView* layoutView = view();
  offset += offsetFromLogicalTopOfFirstPage();

  LayoutFlowThread* flowThread = flowThreadContainingBlock();
  if (!flowThread) {
    LayoutUnit pageLogicalHeight = layoutView->pageLogicalHeight();
    LayoutUnit remainingHeight =
        pageLogicalHeight - intMod(offset, pageLogicalHeight);
    if (pageBoundaryRule == AssociateWithFormerPage) {
      // An offset exactly at a page boundary will act as being part of the
      // former page in question (i.e. no remaining space), rather than being
      // part of the latter (i.e. one whole page length of remaining space).
      remainingHeight = intMod(remainingHeight, pageLogicalHeight);
    }
    return remainingHeight;
  }

  return flowThread->pageRemainingLogicalHeightForOffset(offset,
                                                         pageBoundaryRule);
}

bool LayoutBox::crossesPageBoundary(LayoutUnit offset,
                                    LayoutUnit logicalHeight) const {
  if (!pageLogicalHeightForOffset(offset))
    return false;
  return pageRemainingLogicalHeightForOffset(offset, AssociateWithLatterPage) <
         logicalHeight;
}

LayoutUnit LayoutBox::calculatePaginationStrutToFitContent(
    LayoutUnit offset,
    LayoutUnit strutToNextPage,
    LayoutUnit contentLogicalHeight) const {
  ASSERT(strutToNextPage ==
         pageRemainingLogicalHeightForOffset(offset, AssociateWithLatterPage));
  // If we're a cell in a row that straddles a page then avoid the repeating
  // header group if necessary.
  if (isTableCell()) {
    const LayoutTableCell* cell = toLayoutTableCell(this);
    if (!cell->row()->isFirstRowInSectionAfterHeader())
      strutToNextPage += cell->table()->rowOffsetFromRepeatingHeader();
  }
  LayoutUnit nextPageLogicalTop = offset + strutToNextPage;
  if (pageLogicalHeightForOffset(nextPageLogicalTop) >= contentLogicalHeight)
    return strutToNextPage;  // Content fits just fine in the next page or
                             // column.

  // Moving to the top of the next page or column doesn't result in enough space
  // for the content that we're trying to fit. If we're in a nested
  // fragmentation context, we may find enough space if we move to a column
  // further ahead, by effectively breaking to the next outer fragmentainer.
  LayoutFlowThread* flowThread = flowThreadContainingBlock();
  if (!flowThread) {
    // If there's no flow thread, we're not nested. All pages have the same
    // height. Give up.
    return strutToNextPage;
  }
  // Start searching for a suitable offset at the top of the next page or
  // column.
  LayoutUnit flowThreadOffset =
      offsetFromLogicalTopOfFirstPage() + nextPageLogicalTop;
  return strutToNextPage +
         flowThread->nextLogicalTopForUnbreakableContent(flowThreadOffset,
                                                         contentLogicalHeight) -
         flowThreadOffset;
}

LayoutBox* LayoutBox::snapContainer() const {
  return m_rareData ? m_rareData->m_snapContainer : nullptr;
}

void LayoutBox::setSnapContainer(LayoutBox* newContainer) {
  LayoutBox* oldContainer = snapContainer();
  if (oldContainer == newContainer)
    return;

  if (oldContainer)
    oldContainer->removeSnapArea(*this);

  ensureRareData().m_snapContainer = newContainer;

  if (newContainer)
    newContainer->addSnapArea(*this);
}

void LayoutBox::clearSnapAreas() {
  if (SnapAreaSet* areas = snapAreas()) {
    for (auto& snapArea : *areas)
      snapArea->m_rareData->m_snapContainer = nullptr;
    areas->clear();
  }
}

void LayoutBox::addSnapArea(const LayoutBox& snapArea) {
  ensureRareData().ensureSnapAreas().add(&snapArea);
}

void LayoutBox::removeSnapArea(const LayoutBox& snapArea) {
  if (m_rareData && m_rareData->m_snapAreas) {
    m_rareData->m_snapAreas->remove(&snapArea);
  }
}

SnapAreaSet* LayoutBox::snapAreas() const {
  return m_rareData ? m_rareData->m_snapAreas.get() : nullptr;
}

LayoutRect LayoutBox::debugRect() const {
  LayoutRect rect = frameRect();

  LayoutBlock* block = containingBlock();
  if (block)
    block->adjustChildDebugRect(rect);

  return rect;
}

bool LayoutBox::shouldClipOverflow() const {
  return hasOverflowClip() || styleRef().containsPaint() || hasControlClip();
}

}  // namespace blink