Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3042 insertions, 0 deletions

diff --git a/layout/generic/ReflowInput.cpp b/layout/generic/ReflowInput.cpp
new file mode 100644
index 0000000000..ed7dbd2656
--- /dev/null
+++ b/layout/generic/ReflowInput.cpp
@@ -0,0 +1,3042 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* struct containing the input to nsIFrame::Reflow */
+
+#include "mozilla/ReflowInput.h"
+
+#include <algorithm>
+
+#include "CounterStyleManager.h"
+#include "LayoutLogging.h"
+#include "mozilla/dom/HTMLInputElement.h"
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/WritingModes.h"
+#include "nsBlockFrame.h"
+#include "nsCSSAnonBoxes.h"
+#include "nsFlexContainerFrame.h"
+#include "nsFontInflationData.h"
+#include "nsFontMetrics.h"
+#include "nsGkAtoms.h"
+#include "nsGridContainerFrame.h"
+#include "nsIContent.h"
+#include "nsIFrame.h"
+#include "nsIFrameInlines.h"
+#include "nsImageFrame.h"
+#include "nsIPercentBSizeObserver.h"
+#include "nsLayoutUtils.h"
+#include "nsLineBox.h"
+#include "nsPresContext.h"
+#include "nsStyleConsts.h"
+#include "nsTableCellFrame.h"
+#include "nsTableFrame.h"
+#include "StickyScrollContainer.h"
+
+using namespace mozilla;
+using namespace mozilla::css;
+using namespace mozilla::dom;
+using namespace mozilla::layout;
+
+static bool CheckNextInFlowParenthood(nsIFrame* aFrame, nsIFrame* aParent) {
+  nsIFrame* frameNext = aFrame->GetNextInFlow();
+  nsIFrame* parentNext = aParent->GetNextInFlow();
+  return frameNext && parentNext && frameNext->GetParent() == parentNext;
+}
+
+/**
+ * Adjusts the margin for a list (ol, ul), if necessary, depending on
+ * font inflation settings. Unfortunately, because bullets from a list are
+ * placed in the margin area, we only have ~40px in which to place the
+ * bullets. When they are inflated, however, this causes problems, since
+ * the text takes up more space than is available in the margin.
+ *
+ * This method will return a small amount (in app units) by which the
+ * margin can be adjusted, so that the space is available for list
+ * bullets to be rendered with font inflation enabled.
+ */
+static nscoord FontSizeInflationListMarginAdjustment(const nsIFrame* aFrame) {
+  if (!aFrame->IsBlockFrameOrSubclass()) {
+    return 0;
+  }
+
+  // We only want to adjust the margins if we're dealing with an ordered list.
+  const nsBlockFrame* blockFrame = static_cast<const nsBlockFrame*>(aFrame);
+  if (!blockFrame->HasMarker()) {
+    return 0;
+  }
+
+  float inflation = nsLayoutUtils::FontSizeInflationFor(aFrame);
+  if (inflation <= 1.0f) {
+    return 0;
+  }
+
+  // The HTML spec states that the default padding for ordered lists
+  // begins at 40px, indicating that we have 40px of space to place a
+  // bullet. When performing font inflation calculations, we add space
+  // equivalent to this, but simply inflated at the same amount as the
+  // text, in app units.
+  auto margin = nsPresContext::CSSPixelsToAppUnits(40) * (inflation - 1);
+
+  auto* list = aFrame->StyleList();
+  if (!list->mCounterStyle.IsAtom()) {
+    return margin;
+  }
+
+  nsAtom* type = list->mCounterStyle.AsAtom();
+  if (type != nsGkAtoms::none && type != nsGkAtoms::disc &&
+      type != nsGkAtoms::circle && type != nsGkAtoms::square &&
+      type != nsGkAtoms::disclosure_closed &&
+      type != nsGkAtoms::disclosure_open) {
+    return margin;
+  }
+
+  return 0;
+}
+
+SizeComputationInput::SizeComputationInput(nsIFrame* aFrame,
+                                           gfxContext* aRenderingContext)
+    : mFrame(aFrame),
+      mRenderingContext(aRenderingContext),
+      mWritingMode(aFrame->GetWritingMode()),
+      mIsThemed(aFrame->IsThemed()),
+      mComputedMargin(mWritingMode),
+      mComputedBorderPadding(mWritingMode),
+      mComputedPadding(mWritingMode) {
+  MOZ_ASSERT(mFrame);
+}
+
+SizeComputationInput::SizeComputationInput(
+    nsIFrame* aFrame, gfxContext* aRenderingContext,
+    WritingMode aContainingBlockWritingMode, nscoord aContainingBlockISize,
+    const Maybe<LogicalMargin>& aBorder, const Maybe<LogicalMargin>& aPadding)
+    : SizeComputationInput(aFrame, aRenderingContext) {
+  MOZ_ASSERT(!mFrame->IsTableColFrame());
+  InitOffsets(aContainingBlockWritingMode, aContainingBlockISize,
+              mFrame->Type(), {}, aBorder, aPadding);
+}
+
+// Initialize a <b>root</b> reflow input with a rendering context to
+// use for measuring things.
+ReflowInput::ReflowInput(nsPresContext* aPresContext, nsIFrame* aFrame,
+                         gfxContext* aRenderingContext,
+                         const LogicalSize& aAvailableSpace, InitFlags aFlags)
+    : SizeComputationInput(aFrame, aRenderingContext),
+      mAvailableSize(aAvailableSpace) {
+  MOZ_ASSERT(aRenderingContext, "no rendering context");
+  MOZ_ASSERT(aPresContext, "no pres context");
+  MOZ_ASSERT(aFrame, "no frame");
+  MOZ_ASSERT(aPresContext == aFrame->PresContext(), "wrong pres context");
+
+  if (aFlags.contains(InitFlag::DummyParentReflowInput)) {
+    mFlags.mDummyParentReflowInput = true;
+  }
+  if (aFlags.contains(InitFlag::StaticPosIsCBOrigin)) {
+    mFlags.mStaticPosIsCBOrigin = true;
+  }
+
+  if (!aFlags.contains(InitFlag::CallerWillInit)) {
+    Init(aPresContext);
+  }
+  // When we encounter a PageContent frame this will be set to true.
+  mFlags.mCanHaveClassABreakpoints = false;
+}
+
+// Initialize a reflow input for a child frame's reflow. Some state
+// is copied from the parent reflow input; the remaining state is
+// computed.
+ReflowInput::ReflowInput(nsPresContext* aPresContext,
+                         const ReflowInput& aParentReflowInput,
+                         nsIFrame* aFrame, const LogicalSize& aAvailableSpace,
+                         const Maybe<LogicalSize>& aContainingBlockSize,
+                         InitFlags aFlags,
+                         const StyleSizeOverrides& aSizeOverrides,
+                         ComputeSizeFlags aComputeSizeFlags)
+    : SizeComputationInput(aFrame, aParentReflowInput.mRenderingContext),
+      mParentReflowInput(&aParentReflowInput),
+      mFloatManager(aParentReflowInput.mFloatManager),
+      mLineLayout(mFrame->IsLineParticipant() ? aParentReflowInput.mLineLayout
+                                              : nullptr),
+      mBreakType(aParentReflowInput.mBreakType),
+      mPercentBSizeObserver(
+          (aParentReflowInput.mPercentBSizeObserver &&
+           aParentReflowInput.mPercentBSizeObserver->NeedsToObserve(*this))
+              ? aParentReflowInput.mPercentBSizeObserver
+              : nullptr),
+      mFlags(aParentReflowInput.mFlags),
+      mStyleSizeOverrides(aSizeOverrides),
+      mComputeSizeFlags(aComputeSizeFlags),
+      mReflowDepth(aParentReflowInput.mReflowDepth + 1),
+      mAvailableSize(aAvailableSpace) {
+  MOZ_ASSERT(aPresContext, "no pres context");
+  MOZ_ASSERT(aFrame, "no frame");
+  MOZ_ASSERT(aPresContext == aFrame->PresContext(), "wrong pres context");
+  MOZ_ASSERT(!mFlags.mSpecialBSizeReflow || !aFrame->IsSubtreeDirty(),
+             "frame should be clean when getting special bsize reflow");
+
+  if (mWritingMode.IsOrthogonalTo(aParentReflowInput.GetWritingMode())) {
+    // If we're setting up for an orthogonal flow, and the parent reflow input
+    // had a constrained ComputedBSize, we can use that as our AvailableISize
+    // in preference to leaving it unconstrained.
+    if (AvailableISize() == NS_UNCONSTRAINEDSIZE &&
+        aParentReflowInput.ComputedBSize() != NS_UNCONSTRAINEDSIZE) {
+      SetAvailableISize(aParentReflowInput.ComputedBSize());
+    }
+  }
+
+  // Note: mFlags was initialized as a copy of aParentReflowInput.mFlags up in
+  // this constructor's init list, so the only flags that we need to explicitly
+  // initialize here are those that may need a value other than our parent's.
+  mFlags.mNextInFlowUntouched =
+      aParentReflowInput.mFlags.mNextInFlowUntouched &&
+      CheckNextInFlowParenthood(aFrame, aParentReflowInput.mFrame);
+  mFlags.mAssumingHScrollbar = mFlags.mAssumingVScrollbar = false;
+  mFlags.mIsColumnBalancing = false;
+  mFlags.mColumnSetWrapperHasNoBSizeLeft = false;
+  mFlags.mTreatBSizeAsIndefinite = false;
+  mFlags.mDummyParentReflowInput = false;
+  mFlags.mStaticPosIsCBOrigin = aFlags.contains(InitFlag::StaticPosIsCBOrigin);
+  mFlags.mIOffsetsNeedCSSAlign = mFlags.mBOffsetsNeedCSSAlign = false;
+
+  // aPresContext->IsPaginated() and the named pages pref should have been
+  // checked when constructing the root ReflowInput.
+  if (aParentReflowInput.mFlags.mCanHaveClassABreakpoints) {
+    MOZ_ASSERT(aPresContext->IsPaginated(),
+               "mCanHaveClassABreakpoints set during non-paginated reflow.");
+  }
+
+  {
+    using mozilla::LayoutFrameType;
+    switch (mFrame->Type()) {
+      case LayoutFrameType::PageContent:
+        // PageContent requires paginated reflow.
+        MOZ_ASSERT(aPresContext->IsPaginated(),
+                   "nsPageContentFrame should not be in non-paginated reflow");
+        MOZ_ASSERT(!mFlags.mCanHaveClassABreakpoints,
+                   "mFlags.mCanHaveClassABreakpoints should have been "
+                   "initalized to false before we found nsPageContentFrame");
+        mFlags.mCanHaveClassABreakpoints = true;
+        break;
+      case LayoutFrameType::Block:          // FALLTHROUGH
+      case LayoutFrameType::Canvas:         // FALLTHROUGH
+      case LayoutFrameType::FlexContainer:  // FALLTHROUGH
+      case LayoutFrameType::GridContainer:
+        if (mFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW)) {
+          // Never allow breakpoints inside of out-of-flow frames.
+          mFlags.mCanHaveClassABreakpoints = false;
+          break;
+        }
+        // This frame type can have class A breakpoints, inherit this flag
+        // from the parent (this is done for all flags during construction).
+        // This also includes Canvas frames, as each PageContent frame always
+        // has exactly one child which is a Canvas frame.
+        // Do NOT include the subclasses of BlockFrame here, as the ones for
+        // which this could be applicable (ColumnSetWrapper and the MathML
+        // frames) cannot have class A breakpoints.
+        MOZ_ASSERT(mFlags.mCanHaveClassABreakpoints ==
+                   aParentReflowInput.mFlags.mCanHaveClassABreakpoints);
+        break;
+      default:
+        mFlags.mCanHaveClassABreakpoints = false;
+        break;
+    }
+  }
+
+  if (aFlags.contains(InitFlag::DummyParentReflowInput) ||
+      (mParentReflowInput->mFlags.mDummyParentReflowInput &&
+       mFrame->IsTableFrame())) {
+    mFlags.mDummyParentReflowInput = true;
+  }
+
+  if (!aFlags.contains(InitFlag::CallerWillInit)) {
+    Init(aPresContext, aContainingBlockSize);
+  }
+}
+
+template <typename SizeOrMaxSize>
+inline nscoord SizeComputationInput::ComputeISizeValue(
+    const WritingMode aWM, const LogicalSize& aContainingBlockSize,
+    const LogicalSize& aContentEdgeToBoxSizing, nscoord aBoxSizingToMarginEdge,
+    const SizeOrMaxSize& aSize) const {
+  return mFrame
+      ->ComputeISizeValue(mRenderingContext, aWM, aContainingBlockSize,
+                          aContentEdgeToBoxSizing, aBoxSizingToMarginEdge,
+                          aSize)
+      .mISize;
+}
+
+template <typename SizeOrMaxSize>
+nscoord SizeComputationInput::ComputeISizeValue(
+    const LogicalSize& aContainingBlockSize, StyleBoxSizing aBoxSizing,
+    const SizeOrMaxSize& aSize) const {
+  WritingMode wm = GetWritingMode();
+  const auto borderPadding = ComputedLogicalBorderPadding(wm);
+  LogicalSize inside = aBoxSizing == StyleBoxSizing::Border
+                           ? borderPadding.Size(wm)
+                           : LogicalSize(wm);
+  nscoord outside =
+      borderPadding.IStartEnd(wm) + ComputedLogicalMargin(wm).IStartEnd(wm);
+  outside -= inside.ISize(wm);
+
+  return ComputeISizeValue(wm, aContainingBlockSize, inside, outside, aSize);
+}
+
+nscoord SizeComputationInput::ComputeBSizeValue(
+    nscoord aContainingBlockBSize, StyleBoxSizing aBoxSizing,
+    const LengthPercentage& aSize) const {
+  WritingMode wm = GetWritingMode();
+  nscoord inside = 0;
+  if (aBoxSizing == StyleBoxSizing::Border) {
+    inside = ComputedLogicalBorderPadding(wm).BStartEnd(wm);
+  }
+  return nsLayoutUtils::ComputeBSizeValue(aContainingBlockBSize, inside, aSize);
+}
+
+nsSize ReflowInput::ComputedSizeAsContainerIfConstrained() const {
+  LogicalSize size = ComputedSize();
+  if (size.ISize(mWritingMode) == NS_UNCONSTRAINEDSIZE) {
+    size.ISize(mWritingMode) = 0;
+  } else {
+    size.ISize(mWritingMode) += mComputedBorderPadding.IStartEnd(mWritingMode);
+  }
+  if (size.BSize(mWritingMode) == NS_UNCONSTRAINEDSIZE) {
+    size.BSize(mWritingMode) = 0;
+  } else {
+    size.BSize(mWritingMode) += mComputedBorderPadding.BStartEnd(mWritingMode);
+  }
+  return size.GetPhysicalSize(mWritingMode);
+}
+
+bool ReflowInput::ShouldReflowAllKids() const {
+  // Note that we could make a stronger optimization for IsBResize if
+  // we use it in a ShouldReflowChild test that replaces the current
+  // checks of NS_FRAME_IS_DIRTY | NS_FRAME_HAS_DIRTY_CHILDREN, if it
+  // were tested there along with NS_FRAME_CONTAINS_RELATIVE_BSIZE.
+  // This would need to be combined with a slight change in which
+  // frames NS_FRAME_CONTAINS_RELATIVE_BSIZE is marked on.
+  return mFrame->HasAnyStateBits(NS_FRAME_IS_DIRTY) || IsIResize() ||
+         (IsBResize() &&
+          mFrame->HasAnyStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE)) ||
+         mFlags.mIsInLastColumnBalancingReflow;
+}
+
+void ReflowInput::SetComputedISize(nscoord aComputedISize,
+                                   ResetResizeFlags aFlags) {
+  // It'd be nice to assert that |frame| is not in reflow, but this fails
+  // because viewport frames reset the computed isize on a copy of their reflow
+  // input when reflowing fixed-pos kids.  In that case we actually don't want
+  // to mess with the resize flags, because comparing the frame's rect to the
+  // munged computed isize is pointless.
+  NS_WARNING_ASSERTION(aComputedISize >= 0, "Invalid computed inline-size!");
+  if (ComputedISize() != aComputedISize) {
+    mComputedSize.ISize(mWritingMode) = std::max(0, aComputedISize);
+    if (aFlags == ResetResizeFlags::Yes) {
+      InitResizeFlags(mFrame->PresContext(), mFrame->Type());
+    }
+  }
+}
+
+void ReflowInput::SetComputedBSize(nscoord aComputedBSize,
+                                   ResetResizeFlags aFlags) {
+  // It'd be nice to assert that |frame| is not in reflow, but this fails
+  // for the same reason as above.
+  NS_WARNING_ASSERTION(aComputedBSize >= 0, "Invalid computed block-size!");
+  if (ComputedBSize() != aComputedBSize) {
+    mComputedSize.BSize(mWritingMode) = std::max(0, aComputedBSize);
+    if (aFlags == ResetResizeFlags::Yes) {
+      InitResizeFlags(mFrame->PresContext(), mFrame->Type());
+    }
+  }
+}
+
+void ReflowInput::Init(nsPresContext* aPresContext,
+                       const Maybe<LogicalSize>& aContainingBlockSize,
+                       const Maybe<LogicalMargin>& aBorder,
+                       const Maybe<LogicalMargin>& aPadding) {
+  if (AvailableISize() == NS_UNCONSTRAINEDSIZE) {
+    // Look up the parent chain for an orthogonal inline limit,
+    // and reset AvailableISize() if found.
+    for (const ReflowInput* parent = mParentReflowInput; parent != nullptr;
+         parent = parent->mParentReflowInput) {
+      if (parent->GetWritingMode().IsOrthogonalTo(mWritingMode) &&
+          parent->mOrthogonalLimit != NS_UNCONSTRAINEDSIZE) {
+        SetAvailableISize(parent->mOrthogonalLimit);
+        break;
+      }
+    }
+  }
+
+  LAYOUT_WARN_IF_FALSE(AvailableISize() != NS_UNCONSTRAINEDSIZE,
+                       "have unconstrained inline-size; this should only "
+                       "result from very large sizes, not attempts at "
+                       "intrinsic inline-size calculation");
+
+  mStylePosition = mFrame->StylePosition();
+  mStyleDisplay = mFrame->StyleDisplay();
+  mStyleBorder = mFrame->StyleBorder();
+  mStyleMargin = mFrame->StyleMargin();
+
+  InitCBReflowInput();
+
+  LayoutFrameType type = mFrame->Type();
+  if (type == mozilla::LayoutFrameType::Placeholder) {
+    // Placeholders have a no-op Reflow method that doesn't need the rest of
+    // this initialization, so we bail out early.
+    mComputedSize.SizeTo(mWritingMode, 0, 0);
+    return;
+  }
+
+  mFlags.mIsReplaced = mFrame->IsReplaced() || mFrame->IsReplacedWithBlock();
+
+  InitConstraints(aPresContext, aContainingBlockSize, aBorder, aPadding, type);
+
+  InitResizeFlags(aPresContext, type);
+  InitDynamicReflowRoot();
+
+  nsIFrame* parent = mFrame->GetParent();
+  if (parent && parent->HasAnyStateBits(NS_FRAME_IN_CONSTRAINED_BSIZE) &&
+      !(parent->IsScrollFrame() &&
+        parent->StyleDisplay()->mOverflowY != StyleOverflow::Hidden)) {
+    mFrame->AddStateBits(NS_FRAME_IN_CONSTRAINED_BSIZE);
+  } else if (type == LayoutFrameType::SVGForeignObject) {
+    // An SVG foreignObject frame is inherently constrained block-size.
+    mFrame->AddStateBits(NS_FRAME_IN_CONSTRAINED_BSIZE);
+  } else {
+    const auto& bSizeCoord = mStylePosition->BSize(mWritingMode);
+    const auto& maxBSizeCoord = mStylePosition->MaxBSize(mWritingMode);
+    if ((!bSizeCoord.BehavesLikeInitialValueOnBlockAxis() ||
+         !maxBSizeCoord.BehavesLikeInitialValueOnBlockAxis()) &&
+        // Don't set NS_FRAME_IN_CONSTRAINED_BSIZE on body or html elements.
+        (mFrame->GetContent() && !(mFrame->GetContent()->IsAnyOfHTMLElements(
+                                     nsGkAtoms::body, nsGkAtoms::html)))) {
+      // If our block-size was specified as a percentage, then this could
+      // actually resolve to 'auto', based on:
+      // http://www.w3.org/TR/CSS21/visudet.html#the-height-property
+      nsIFrame* containingBlk = mFrame;
+      while (containingBlk) {
+        const nsStylePosition* stylePos = containingBlk->StylePosition();
+        const auto& bSizeCoord = stylePos->BSize(mWritingMode);
+        const auto& maxBSizeCoord = stylePos->MaxBSize(mWritingMode);
+        if ((bSizeCoord.IsLengthPercentage() && !bSizeCoord.HasPercent()) ||
+            (maxBSizeCoord.IsLengthPercentage() &&
+             !maxBSizeCoord.HasPercent())) {
+          mFrame->AddStateBits(NS_FRAME_IN_CONSTRAINED_BSIZE);
+          break;
+        } else if (bSizeCoord.HasPercent() || maxBSizeCoord.HasPercent()) {
+          if (!(containingBlk = containingBlk->GetContainingBlock())) {
+            // If we've reached the top of the tree, then we don't have
+            // a constrained block-size.
+            mFrame->RemoveStateBits(NS_FRAME_IN_CONSTRAINED_BSIZE);
+            break;
+          }
+
+          continue;
+        } else {
+          mFrame->RemoveStateBits(NS_FRAME_IN_CONSTRAINED_BSIZE);
+          break;
+        }
+      }
+    } else {
+      mFrame->RemoveStateBits(NS_FRAME_IN_CONSTRAINED_BSIZE);
+    }
+  }
+
+  if (mParentReflowInput &&
+      mParentReflowInput->GetWritingMode().IsOrthogonalTo(mWritingMode)) {
+    // Orthogonal frames are always reflowed with an unconstrained
+    // dimension to avoid incomplete reflow across an orthogonal
+    // boundary. Normally this is the block-size, but for column sets
+    // with auto-height it's the inline-size, so that they can add
+    // columns in the container's block direction
+    if (type == LayoutFrameType::ColumnSet &&
+        mStylePosition->ISize(mWritingMode).IsAuto()) {
+      SetComputedISize(NS_UNCONSTRAINEDSIZE, ResetResizeFlags::No);
+    } else {
+      SetAvailableBSize(NS_UNCONSTRAINEDSIZE);
+    }
+  }
+
+  if (mFrame->GetContainSizeAxes().mBContained) {
+    // In the case that a box is size contained in block axis, we want to ensure
+    // that it is also monolithic. We do this by setting AvailableBSize() to an
+    // unconstrained size to avoid fragmentation.
+    SetAvailableBSize(NS_UNCONSTRAINEDSIZE);
+  }
+
+  LAYOUT_WARN_IF_FALSE(
+      (mStyleDisplay->IsInlineOutsideStyle() && !mFrame->IsReplaced()) ||
+          type == LayoutFrameType::Text ||
+          ComputedISize() != NS_UNCONSTRAINEDSIZE,
+      "have unconstrained inline-size; this should only "
+      "result from very large sizes, not attempts at "
+      "intrinsic inline-size calculation");
+}
+
+static bool MightBeContainingBlockFor(nsIFrame* aMaybeContainingBlock,
+                                      nsIFrame* aFrame,
+                                      const nsStyleDisplay* aStyleDisplay) {
+  // Keep this in sync with nsIFrame::GetContainingBlock.
+  if (aFrame->IsAbsolutelyPositioned(aStyleDisplay) &&
+      aMaybeContainingBlock == aFrame->GetParent()) {
+    return true;
+  }
+  return aMaybeContainingBlock->IsBlockContainer();
+}
+
+void ReflowInput::InitCBReflowInput() {
+  if (!mParentReflowInput) {
+    mCBReflowInput = nullptr;
+    return;
+  }
+  if (mParentReflowInput->mFlags.mDummyParentReflowInput) {
+    mCBReflowInput = mParentReflowInput;
+    return;
+  }
+
+  // To avoid a long walk up the frame tree check if the parent frame can be a
+  // containing block for mFrame.
+  if (MightBeContainingBlockFor(mParentReflowInput->mFrame, mFrame,
+                                mStyleDisplay) &&
+      mParentReflowInput->mFrame ==
+          mFrame->GetContainingBlock(0, mStyleDisplay)) {
+    // Inner table frames need to use the containing block of the outer
+    // table frame.
+    if (mFrame->IsTableFrame()) {
+      mCBReflowInput = mParentReflowInput->mCBReflowInput;
+    } else {
+      mCBReflowInput = mParentReflowInput;
+    }
+  } else {
+    mCBReflowInput = mParentReflowInput->mCBReflowInput;
+  }
+}
+
+/* Check whether CalcQuirkContainingBlockHeight would stop on the
+ * given reflow input, using its block as a height.  (essentially
+ * returns false for any case in which CalcQuirkContainingBlockHeight
+ * has a "continue" in its main loop.)
+ *
+ * XXX Maybe refactor CalcQuirkContainingBlockHeight so it uses
+ * this function as well
+ */
+static bool IsQuirkContainingBlockHeight(const ReflowInput* rs,
+                                         LayoutFrameType aFrameType) {
+  if (LayoutFrameType::Block == aFrameType ||
+      LayoutFrameType::Scroll == aFrameType) {
+    // Note: This next condition could change due to a style change,
+    // but that would cause a style reflow anyway, which means we're ok.
+    if (NS_UNCONSTRAINEDSIZE == rs->ComputedHeight()) {
+      if (!rs->mFrame->IsAbsolutelyPositioned(rs->mStyleDisplay)) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+void ReflowInput::InitResizeFlags(nsPresContext* aPresContext,
+                                  LayoutFrameType aFrameType) {
+  SetBResize(false);
+  SetIResize(false);
+  mFlags.mIsBResizeForPercentages = false;
+
+  const WritingMode wm = mWritingMode;  // just a shorthand
+  // We should report that we have a resize in the inline dimension if
+  // *either* the border-box size or the content-box size in that
+  // dimension has changed.  It might not actually be necessary to do
+  // this if the border-box size has changed and the content-box size
+  // has not changed, but since we've historically used the flag to mean
+  // border-box size change, continue to do that. It's possible for
+  // the content-box size to change without a border-box size change or
+  // a style change given (1) a fixed width (possibly fixed by max-width
+  // or min-width), box-sizing:border-box, and percentage padding;
+  // (2) box-sizing:content-box, M% width, and calc(Npx - M%) padding.
+  //
+  // However, we don't actually have the information at this point to tell
+  // whether the content-box size has changed, since both style data and the
+  // UsedPaddingProperty() have already been updated in
+  // SizeComputationInput::InitOffsets(). So, we check the HasPaddingChange()
+  // bit for the cases where it's possible for the content-box size to have
+  // changed without either (a) a change in the border-box size or (b) an
+  // nsChangeHint_NeedDirtyReflow change hint due to change in border or
+  // padding.
+  //
+  // We don't clear the HasPaddingChange() bit here, since sometimes we
+  // construct reflow input (e.g. in nsBlockFrame::ReflowBlockFrame to compute
+  // margin collapsing) without reflowing the frame. Instead, we clear it in
+  // nsIFrame::DidReflow().
+  bool isIResize =
+      // is the border-box resizing?
+      mFrame->ISize(wm) !=
+          ComputedISize() + ComputedLogicalBorderPadding(wm).IStartEnd(wm) ||
+      // or is the content-box resizing?  (see comment above)
+      mFrame->HasPaddingChange();
+
+  if (mFrame->HasAnyStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT) &&
+      nsLayoutUtils::FontSizeInflationEnabled(aPresContext)) {
+    // Create our font inflation data if we don't have it already, and
+    // give it our current width information.
+    bool dirty = nsFontInflationData::UpdateFontInflationDataISizeFor(*this) &&
+                 // Avoid running this at the box-to-block interface
+                 // (where we shouldn't be inflating anyway, and where
+                 // reflow input construction is probably to construct a
+                 // dummy parent reflow input anyway).
+                 !mFlags.mDummyParentReflowInput;
+
+    if (dirty || (!mFrame->GetParent() && isIResize)) {
+      // When font size inflation is enabled, a change in either:
+      //  * the effective width of a font inflation flow root
+      //  * the width of the frame
+      // needs to cause a dirty reflow since they change the font size
+      // inflation calculations, which in turn change the size of text,
+      // line-heights, etc.  This is relatively similar to a classic
+      // case of style change reflow, except that because inflation
+      // doesn't affect the intrinsic sizing codepath, there's no need
+      // to invalidate intrinsic sizes.
+      //
+      // Note that this makes horizontal resizing a good bit more
+      // expensive.  However, font size inflation is targeted at a set of
+      // devices (zoom-and-pan devices) where the main use case for
+      // horizontal resizing needing to be efficient (window resizing) is
+      // not present.  It does still increase the cost of dynamic changes
+      // caused by script where a style or content change in one place
+      // causes a resize in another (e.g., rebalancing a table).
+
+      // FIXME: This isn't so great for the cases where
+      // ReflowInput::SetComputedWidth is called, if the first time
+      // we go through InitResizeFlags we set IsHResize() to true, and then
+      // the second time we'd set it to false even without the
+      // NS_FRAME_IS_DIRTY bit already set.
+      if (mFrame->IsSVGForeignObjectFrame()) {
+        // Foreign object frames use dirty bits in a special way.
+        mFrame->AddStateBits(NS_FRAME_HAS_DIRTY_CHILDREN);
+        nsIFrame* kid = mFrame->PrincipalChildList().FirstChild();
+        if (kid) {
+          kid->MarkSubtreeDirty();
+        }
+      } else {
+        mFrame->MarkSubtreeDirty();
+      }
+
+      // Mark intrinsic widths on all descendants dirty.  We need to do
+      // this (1) since we're changing the size of text and need to
+      // clear text runs on text frames and (2) since we actually are
+      // changing some intrinsic widths, but only those that live inside
+      // of containers.
+
+      // It makes sense to do this for descendants but not ancestors
+      // (which is unusual) because we're only changing the unusual
+      // inflation-dependent intrinsic widths (i.e., ones computed with
+      // nsPresContext::mInflationDisabledForShrinkWrap set to false),
+      // which should never affect anything outside of their inflation
+      // flow root (or, for that matter, even their inflation
+      // container).
+
+      // This is also different from what PresShell::FrameNeedsReflow
+      // does because it doesn't go through placeholders.  It doesn't
+      // need to because we're actually doing something that cares about
+      // frame tree geometry (the width on an ancestor) rather than
+      // style.
+
+      AutoTArray<nsIFrame*, 32> stack;
+      stack.AppendElement(mFrame);
+
+      do {
+        nsIFrame* f = stack.PopLastElement();
+        for (const auto& childList : f->ChildLists()) {
+          for (nsIFrame* kid : childList.mList) {
+            kid->MarkIntrinsicISizesDirty();
+            stack.AppendElement(kid);
+          }
+        }
+      } while (stack.Length() != 0);
+    }
+  }
+
+  SetIResize(!mFrame->HasAnyStateBits(NS_FRAME_IS_DIRTY) && isIResize);
+
+  // XXX Should we really need to null check mCBReflowInput?  (We do for
+  // at least nsBoxFrame).
+  if (mFrame->HasBSizeChange()) {
+    // When we have an nsChangeHint_UpdateComputedBSize, we'll set a bit
+    // on the frame to indicate we're resizing.  This might catch cases,
+    // such as a change between auto and a length, where the box doesn't
+    // actually resize but children with percentages resize (since those
+    // percentages become auto if their containing block is auto).
+    SetBResize(true);
+    mFlags.mIsBResizeForPercentages = true;
+    // We don't clear the HasBSizeChange state here, since sometimes we
+    // construct a ReflowInput (e.g. in nsBlockFrame::ReflowBlockFrame to
+    // compute margin collapsing) without reflowing the frame. Instead, we
+    // clear it in nsIFrame::DidReflow.
+  } else if (mCBReflowInput &&
+             mCBReflowInput->IsBResizeForPercentagesForWM(wm) &&
+             (mStylePosition->BSize(wm).HasPercent() ||
+              mStylePosition->MinBSize(wm).HasPercent() ||
+              mStylePosition->MaxBSize(wm).HasPercent())) {
+    // We have a percentage (or calc-with-percentage) block-size, and the
+    // value it's relative to has changed.
+    SetBResize(true);
+    mFlags.mIsBResizeForPercentages = true;
+  } else if (aFrameType == LayoutFrameType::TableCell &&
+             (mFlags.mSpecialBSizeReflow ||
+              mFrame->FirstInFlow()->HasAnyStateBits(
+                  NS_TABLE_CELL_HAD_SPECIAL_REFLOW)) &&
+             mFrame->HasAnyStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE)) {
+    // Need to set the bit on the cell so that
+    // mCBReflowInput->IsBResize() is set correctly below when
+    // reflowing descendant.
+    SetBResize(true);
+    mFlags.mIsBResizeForPercentages = true;
+  } else if (mCBReflowInput && mFrame->IsBlockWrapper()) {
+    // XXX Is this problematic for relatively positioned inlines acting
+    // as containing block for absolutely positioned elements?
+    // Possibly; in that case we should at least be checking
+    // IsSubtreeDirty(), I'd think.
+    SetBResize(mCBReflowInput->IsBResizeForWM(wm));
+    mFlags.mIsBResizeForPercentages =
+        mCBReflowInput->IsBResizeForPercentagesForWM(wm);
+  } else if (ComputedBSize() == NS_UNCONSTRAINEDSIZE) {
+    // We have an 'auto' block-size.
+    if (eCompatibility_NavQuirks == aPresContext->CompatibilityMode() &&
+        mCBReflowInput) {
+      // FIXME: This should probably also check IsIResize().
+      SetBResize(mCBReflowInput->IsBResizeForWM(wm));
+    } else {
+      SetBResize(IsIResize());
+    }
+    SetBResize(IsBResize() || mFrame->IsSubtreeDirty());
+  } else {
+    // We have a non-'auto' block-size, i.e., a length.  Set the BResize
+    // flag to whether the size is actually different.
+    SetBResize(mFrame->BSize(wm) !=
+               ComputedBSize() +
+                   ComputedLogicalBorderPadding(wm).BStartEnd(wm));
+  }
+
+  bool dependsOnCBBSize = (mStylePosition->BSizeDependsOnContainer(wm) &&
+                           // FIXME: condition this on not-abspos?
+                           !mStylePosition->BSize(wm).IsAuto()) ||
+                          mStylePosition->MinBSizeDependsOnContainer(wm) ||
+                          mStylePosition->MaxBSizeDependsOnContainer(wm) ||
+                          mStylePosition->mOffset.GetBStart(wm).HasPercent() ||
+                          !mStylePosition->mOffset.GetBEnd(wm).IsAuto();
+
+  // If mFrame is a flex item, and mFrame's block axis is the flex container's
+  // main axis (e.g. in a column-oriented flex container with same
+  // writing-mode), then its block-size depends on its CB size, if its
+  // flex-basis has a percentage.
+  if (mFrame->IsFlexItem() &&
+      !nsFlexContainerFrame::IsItemInlineAxisMainAxis(mFrame)) {
+    const auto& flexBasis = mStylePosition->mFlexBasis;
+    dependsOnCBBSize |= (flexBasis.IsSize() && flexBasis.AsSize().HasPercent());
+  }
+
+  if (mFrame->StyleFont()->mLineHeight.IsMozBlockHeight()) {
+    // line-height depends on block bsize
+    mFrame->AddStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE);
+    // but only on containing blocks if this frame is not a suitable block
+    dependsOnCBBSize |= !nsLayoutUtils::IsNonWrapperBlock(mFrame);
+  }
+
+  // If we're the descendant of a table cell that performs special bsize
+  // reflows and we could be the child that requires them, always set
+  // the block-axis resize in case this is the first pass before the
+  // special bsize reflow.  However, don't do this if it actually is
+  // the special bsize reflow, since in that case it will already be
+  // set correctly above if we need it set.
+  if (!IsBResize() && mCBReflowInput &&
+      (mCBReflowInput->mFrame->IsTableCellFrame() ||
+       mCBReflowInput->mFlags.mHeightDependsOnAncestorCell) &&
+      !mCBReflowInput->mFlags.mSpecialBSizeReflow && dependsOnCBBSize) {
+    SetBResize(true);
+    mFlags.mHeightDependsOnAncestorCell = true;
+  }
+
+  // Set NS_FRAME_CONTAINS_RELATIVE_BSIZE if it's needed.
+
+  // It would be nice to check that |ComputedBSize != NS_UNCONSTRAINEDSIZE|
+  // &&ed with the percentage bsize check.  However, this doesn't get
+  // along with table special bsize reflows, since a special bsize
+  // reflow (a quirk that makes such percentage height work on children
+  // of table cells) can cause not just a single percentage height to
+  // become fixed, but an entire descendant chain of percentage height
+  // to become fixed.
+  if (dependsOnCBBSize && mCBReflowInput) {
+    const ReflowInput* rs = this;
+    bool hitCBReflowInput = false;
+    do {
+      rs = rs->mParentReflowInput;
+      if (!rs) {
+        break;
+      }
+
+      if (rs->mFrame->HasAnyStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE)) {
+        break;  // no need to go further
+      }
+      rs->mFrame->AddStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE);
+
+      // Keep track of whether we've hit the containing block, because
+      // we need to go at least that far.
+      if (rs == mCBReflowInput) {
+        hitCBReflowInput = true;
+      }
+
+      // XXX What about orthogonal flows? It doesn't make sense to
+      // keep propagating this bit across an orthogonal boundary,
+      // where the meaning of BSize changes. Bug 1175517.
+    } while (!hitCBReflowInput ||
+             (eCompatibility_NavQuirks == aPresContext->CompatibilityMode() &&
+              !IsQuirkContainingBlockHeight(rs, rs->mFrame->Type())));
+    // Note: We actually don't need to set the
+    // NS_FRAME_CONTAINS_RELATIVE_BSIZE bit for the cases
+    // where we hit the early break statements in
+    // CalcQuirkContainingBlockHeight. But it doesn't hurt
+    // us to set the bit in these cases.
+  }
+  if (mFrame->HasAnyStateBits(NS_FRAME_IS_DIRTY)) {
+    // If we're reflowing everything, then we'll find out if we need
+    // to re-set this.
+    mFrame->RemoveStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE);
+  }
+}
+
+void ReflowInput::InitDynamicReflowRoot() {
+  if (mFrame->CanBeDynamicReflowRoot()) {
+    mFrame->AddStateBits(NS_FRAME_DYNAMIC_REFLOW_ROOT);
+  } else {
+    mFrame->RemoveStateBits(NS_FRAME_DYNAMIC_REFLOW_ROOT);
+  }
+}
+
+bool ReflowInput::ShouldApplyAutomaticMinimumOnBlockAxis() const {
+  MOZ_ASSERT(!mFrame->HasReplacedSizing());
+  return mFlags.mIsBSizeSetByAspectRatio &&
+         !mStyleDisplay->IsScrollableOverflow() &&
+         mStylePosition->MinBSize(GetWritingMode()).IsAuto();
+}
+
+bool ReflowInput::IsInFragmentedContext() const {
+  // We consider mFrame with a prev-in-flow being in a fragmented context
+  // because nsColumnSetFrame can reflow its last column with an unconstrained
+  // available block-size.
+  return AvailableBSize() != NS_UNCONSTRAINEDSIZE || mFrame->GetPrevInFlow();
+}
+
+/* static */
+LogicalMargin ReflowInput::ComputeRelativeOffsets(WritingMode aWM,
+                                                  nsIFrame* aFrame,
+                                                  const LogicalSize& aCBSize) {
+  LogicalMargin offsets(aWM);
+  const nsStylePosition* position = aFrame->StylePosition();
+
+  // Compute the 'inlineStart' and 'inlineEnd' values. 'inlineStart'
+  // moves the boxes to the end of the line, and 'inlineEnd' moves the
+  // boxes to the start of the line. The computed values are always:
+  // inlineStart=-inlineEnd
+  const auto& inlineStart = position->mOffset.GetIStart(aWM);
+  const auto& inlineEnd = position->mOffset.GetIEnd(aWM);
+  bool inlineStartIsAuto = inlineStart.IsAuto();
+  bool inlineEndIsAuto = inlineEnd.IsAuto();
+
+  // If neither 'inlineStart' nor 'inlineEnd' is auto, then we're
+  // over-constrained and we ignore one of them
+  if (!inlineStartIsAuto && !inlineEndIsAuto) {
+    inlineEndIsAuto = true;
+  }
+
+  if (inlineStartIsAuto) {
+    if (inlineEndIsAuto) {
+      // If both are 'auto' (their initial values), the computed values are 0
+      offsets.IStart(aWM) = offsets.IEnd(aWM) = 0;
+    } else {
+      // 'inlineEnd' isn't 'auto' so compute its value
+      offsets.IEnd(aWM) =
+          nsLayoutUtils::ComputeCBDependentValue(aCBSize.ISize(aWM), inlineEnd);
+
+      // Computed value for 'inlineStart' is minus the value of 'inlineEnd'
+      offsets.IStart(aWM) = -offsets.IEnd(aWM);
+    }
+
+  } else {
+    NS_ASSERTION(inlineEndIsAuto, "unexpected specified constraint");
+
+    // 'InlineStart' isn't 'auto' so compute its value
+    offsets.IStart(aWM) =
+        nsLayoutUtils::ComputeCBDependentValue(aCBSize.ISize(aWM), inlineStart);
+
+    // Computed value for 'inlineEnd' is minus the value of 'inlineStart'
+    offsets.IEnd(aWM) = -offsets.IStart(aWM);
+  }
+
+  // Compute the 'blockStart' and 'blockEnd' values. The 'blockStart'
+  // and 'blockEnd' properties move relatively positioned elements in
+  // the block progression direction. They also must be each other's
+  // negative
+  const auto& blockStart = position->mOffset.GetBStart(aWM);
+  const auto& blockEnd = position->mOffset.GetBEnd(aWM);
+  bool blockStartIsAuto = blockStart.IsAuto();
+  bool blockEndIsAuto = blockEnd.IsAuto();
+
+  // Check for percentage based values and a containing block block-size
+  // that depends on the content block-size. Treat them like 'auto'
+  if (NS_UNCONSTRAINEDSIZE == aCBSize.BSize(aWM)) {
+    if (blockStart.HasPercent()) {
+      blockStartIsAuto = true;
+    }
+    if (blockEnd.HasPercent()) {
+      blockEndIsAuto = true;
+    }
+  }
+
+  // If neither is 'auto', 'block-end' is ignored
+  if (!blockStartIsAuto && !blockEndIsAuto) {
+    blockEndIsAuto = true;
+  }
+
+  if (blockStartIsAuto) {
+    if (blockEndIsAuto) {
+      // If both are 'auto' (their initial values), the computed values are 0
+      offsets.BStart(aWM) = offsets.BEnd(aWM) = 0;
+    } else {
+      // 'blockEnd' isn't 'auto' so compute its value
+      offsets.BEnd(aWM) = nsLayoutUtils::ComputeBSizeDependentValue(
+          aCBSize.BSize(aWM), blockEnd);
+
+      // Computed value for 'blockStart' is minus the value of 'blockEnd'
+      offsets.BStart(aWM) = -offsets.BEnd(aWM);
+    }
+
+  } else {
+    NS_ASSERTION(blockEndIsAuto, "unexpected specified constraint");
+
+    // 'blockStart' isn't 'auto' so compute its value
+    offsets.BStart(aWM) = nsLayoutUtils::ComputeBSizeDependentValue(
+        aCBSize.BSize(aWM), blockStart);
+
+    // Computed value for 'blockEnd' is minus the value of 'blockStart'
+    offsets.BEnd(aWM) = -offsets.BStart(aWM);
+  }
+
+  // Convert the offsets to physical coordinates and store them on the frame
+  const nsMargin physicalOffsets = offsets.GetPhysicalMargin(aWM);
+  if (nsMargin* prop =
+          aFrame->GetProperty(nsIFrame::ComputedOffsetProperty())) {
+    *prop = physicalOffsets;
+  } else {
+    aFrame->AddProperty(nsIFrame::ComputedOffsetProperty(),
+                        new nsMargin(physicalOffsets));
+  }
+
+  NS_ASSERTION(offsets.IStart(aWM) == -offsets.IEnd(aWM) &&
+                   offsets.BStart(aWM) == -offsets.BEnd(aWM),
+               "ComputeRelativeOffsets should return valid results!");
+
+  return offsets;
+}
+
+/* static */
+void ReflowInput::ApplyRelativePositioning(nsIFrame* aFrame,
+                                           const nsMargin& aComputedOffsets,
+                                           nsPoint* aPosition) {
+  if (!aFrame->IsRelativelyOrStickyPositioned()) {
+    NS_ASSERTION(!aFrame->HasProperty(nsIFrame::NormalPositionProperty()),
+                 "We assume that changing the 'position' property causes "
+                 "frame reconstruction.  If that ever changes, this code "
+                 "should call "
+                 "aFrame->RemoveProperty(nsIFrame::NormalPositionProperty())");
+    return;
+  }
+
+  // Store the normal position
+  aFrame->SetProperty(nsIFrame::NormalPositionProperty(), *aPosition);
+
+  const nsStyleDisplay* display = aFrame->StyleDisplay();
+  if (StylePositionProperty::Relative == display->mPosition) {
+    *aPosition += nsPoint(aComputedOffsets.left, aComputedOffsets.top);
+  } else if (StylePositionProperty::Sticky == display->mPosition &&
+             !aFrame->GetNextContinuation() && !aFrame->GetPrevContinuation() &&
+             !aFrame->HasAnyStateBits(NS_FRAME_PART_OF_IBSPLIT)) {
+    // Sticky positioning for elements with multiple frames needs to be
+    // computed all at once. We can't safely do that here because we might be
+    // partway through (re)positioning the frames, so leave it until the scroll
+    // container reflows and calls StickyScrollContainer::UpdatePositions.
+    // For single-frame sticky positioned elements, though, go ahead and apply
+    // it now to avoid unnecessary overflow updates later.
+    StickyScrollContainer* ssc =
+        StickyScrollContainer::GetStickyScrollContainerForFrame(aFrame);
+    if (ssc) {
+      *aPosition = ssc->ComputePosition(aFrame);
+    }
+  }
+}
+
+// static
+void ReflowInput::ComputeAbsPosInlineAutoMargin(nscoord aAvailMarginSpace,
+                                                WritingMode aContainingBlockWM,
+                                                bool aIsMarginIStartAuto,
+                                                bool aIsMarginIEndAuto,
+                                                LogicalMargin& aMargin,
+                                                LogicalMargin& aOffsets) {
+  if (aIsMarginIStartAuto) {
+    if (aIsMarginIEndAuto) {
+      if (aAvailMarginSpace < 0) {
+        // Note that this case is different from the neither-'auto'
+        // case below, where the spec says to ignore 'left'/'right'.
+        // Ignore the specified value for 'margin-right'.
+        aMargin.IEnd(aContainingBlockWM) = aAvailMarginSpace;
+      } else {
+        // Both 'margin-left' and 'margin-right' are 'auto', so they get
+        // equal values
+        aMargin.IStart(aContainingBlockWM) = aAvailMarginSpace / 2;
+        aMargin.IEnd(aContainingBlockWM) =
+            aAvailMarginSpace - aMargin.IStart(aContainingBlockWM);
+      }
+    } else {
+      // Just 'margin-left' is 'auto'
+      aMargin.IStart(aContainingBlockWM) = aAvailMarginSpace;
+    }
+  } else {
+    if (aIsMarginIEndAuto) {
+      // Just 'margin-right' is 'auto'
+      aMargin.IEnd(aContainingBlockWM) = aAvailMarginSpace;
+    } else {
+      // We're over-constrained so use the direction of the containing
+      // block to dictate which value to ignore.  (And note that the
+      // spec says to ignore 'left' or 'right' rather than
+      // 'margin-left' or 'margin-right'.)
+      // Note that this case is different from the both-'auto' case
+      // above, where the spec says to ignore
+      // 'margin-left'/'margin-right'.
+      // Ignore the specified value for 'right'.
+      aOffsets.IEnd(aContainingBlockWM) += aAvailMarginSpace;
+    }
+  }
+}
+
+// static
+void ReflowInput::ComputeAbsPosBlockAutoMargin(nscoord aAvailMarginSpace,
+                                               WritingMode aContainingBlockWM,
+                                               bool aIsMarginBStartAuto,
+                                               bool aIsMarginBEndAuto,
+                                               LogicalMargin& aMargin,
+                                               LogicalMargin& aOffsets) {
+  if (aIsMarginBStartAuto) {
+    if (aIsMarginBEndAuto) {
+      // Both 'margin-top' and 'margin-bottom' are 'auto', so they get
+      // equal values
+      aMargin.BStart(aContainingBlockWM) = aAvailMarginSpace / 2;
+      aMargin.BEnd(aContainingBlockWM) =
+          aAvailMarginSpace - aMargin.BStart(aContainingBlockWM);
+    } else {
+      // Just margin-block-start is 'auto'
+      aMargin.BStart(aContainingBlockWM) = aAvailMarginSpace;
+    }
+  } else {
+    if (aIsMarginBEndAuto) {
+      // Just margin-block-end is 'auto'
+      aMargin.BEnd(aContainingBlockWM) = aAvailMarginSpace;
+    } else {
+      // We're over-constrained so ignore the specified value for
+      // block-end.  (And note that the spec says to ignore 'bottom'
+      // rather than 'margin-bottom'.)
+      aOffsets.BEnd(aContainingBlockWM) += aAvailMarginSpace;
+    }
+  }
+}
+
+void ReflowInput::ApplyRelativePositioning(
+    nsIFrame* aFrame, mozilla::WritingMode aWritingMode,
+    const mozilla::LogicalMargin& aComputedOffsets,
+    mozilla::LogicalPoint* aPosition, const nsSize& aContainerSize) {
+  // Subtract the size of the frame from the container size that we
+  // use for converting between the logical and physical origins of
+  // the frame. This accounts for the fact that logical origins in RTL
+  // coordinate systems are at the top right of the frame instead of
+  // the top left.
+  nsSize frameSize = aFrame->GetSize();
+  nsPoint pos =
+      aPosition->GetPhysicalPoint(aWritingMode, aContainerSize - frameSize);
+  ApplyRelativePositioning(
+      aFrame, aComputedOffsets.GetPhysicalMargin(aWritingMode), &pos);
+  *aPosition =
+      mozilla::LogicalPoint(aWritingMode, pos, aContainerSize - frameSize);
+}
+
+nsIFrame* ReflowInput::GetHypotheticalBoxContainer(nsIFrame* aFrame,
+                                                   nscoord& aCBIStartEdge,
+                                                   LogicalSize& aCBSize) const {
+  aFrame = aFrame->GetContainingBlock();
+  NS_ASSERTION(aFrame != mFrame, "How did that happen?");
+
+  /* Now aFrame is the containing block we want */
+
+  /* Check whether the containing block is currently being reflowed.
+     If so, use the info from the reflow input. */
+  const ReflowInput* reflowInput;
+  if (aFrame->HasAnyStateBits(NS_FRAME_IN_REFLOW)) {
+    for (reflowInput = mParentReflowInput;
+         reflowInput && reflowInput->mFrame != aFrame;
+         reflowInput = reflowInput->mParentReflowInput) {
+      /* do nothing */
+    }
+  } else {
+    reflowInput = nullptr;
+  }
+
+  if (reflowInput) {
+    WritingMode wm = reflowInput->GetWritingMode();
+    NS_ASSERTION(wm == aFrame->GetWritingMode(), "unexpected writing mode");
+    aCBIStartEdge = reflowInput->ComputedLogicalBorderPadding(wm).IStart(wm);
+    aCBSize = reflowInput->ComputedSize(wm);
+  } else {
+    /* Didn't find a reflow reflowInput for aFrame.  Just compute the
+       information we want, on the assumption that aFrame already knows its
+       size.  This really ought to be true by now. */
+    NS_ASSERTION(!aFrame->HasAnyStateBits(NS_FRAME_IN_REFLOW),
+                 "aFrame shouldn't be in reflow; we'll lie if it is");
+    WritingMode wm = aFrame->GetWritingMode();
+    // Compute CB's offset & content-box size by subtracting borderpadding from
+    // frame size.
+    const auto& bp = aFrame->GetLogicalUsedBorderAndPadding(wm);
+    aCBIStartEdge = bp.IStart(wm);
+    aCBSize = aFrame->GetLogicalSize(wm) - bp.Size(wm);
+  }
+
+  return aFrame;
+}
+
+struct nsHypotheticalPosition {
+  // offset from inline-start edge of containing block (which is a padding edge)
+  nscoord mIStart;
+  // offset from block-start edge of containing block (which is a padding edge)
+  nscoord mBStart;
+  WritingMode mWritingMode;
+};
+
+/**
+ * aInsideBoxSizing returns the part of the padding, border, and margin
+ * in the aAxis dimension that goes inside the edge given by box-sizing;
+ * aOutsideBoxSizing returns the rest.
+ */
+void ReflowInput::CalculateBorderPaddingMargin(
+    LogicalAxis aAxis, nscoord aContainingBlockSize, nscoord* aInsideBoxSizing,
+    nscoord* aOutsideBoxSizing) const {
+  WritingMode wm = GetWritingMode();
+  mozilla::Side startSide =
+      wm.PhysicalSide(MakeLogicalSide(aAxis, eLogicalEdgeStart));
+  mozilla::Side endSide =
+      wm.PhysicalSide(MakeLogicalSide(aAxis, eLogicalEdgeEnd));
+
+  nsMargin styleBorder = mStyleBorder->GetComputedBorder();
+  nscoord borderStartEnd =
+      styleBorder.Side(startSide) + styleBorder.Side(endSide);
+
+  nscoord paddingStartEnd, marginStartEnd;
+
+  // See if the style system can provide us the padding directly
+  const auto* stylePadding = mFrame->StylePadding();
+  if (nsMargin padding; stylePadding->GetPadding(padding)) {
+    paddingStartEnd = padding.Side(startSide) + padding.Side(endSide);
+  } else {
+    // We have to compute the start and end values
+    nscoord start, end;
+    start = nsLayoutUtils::ComputeCBDependentValue(
+        aContainingBlockSize, stylePadding->mPadding.Get(startSide));
+    end = nsLayoutUtils::ComputeCBDependentValue(
+        aContainingBlockSize, stylePadding->mPadding.Get(endSide));
+    paddingStartEnd = start + end;
+  }
+
+  // See if the style system can provide us the margin directly
+  if (nsMargin margin; mStyleMargin->GetMargin(margin)) {
+    marginStartEnd = margin.Side(startSide) + margin.Side(endSide);
+  } else {
+    nscoord start, end;
+    // We have to compute the start and end values
+    if (mStyleMargin->mMargin.Get(startSide).IsAuto()) {
+      // We set this to 0 for now, and fix it up later in
+      // InitAbsoluteConstraints (which is caller of this function, via
+      // CalculateHypotheticalPosition).
+      start = 0;
+    } else {
+      start = nsLayoutUtils::ComputeCBDependentValue(
+          aContainingBlockSize, mStyleMargin->mMargin.Get(startSide));
+    }
+    if (mStyleMargin->mMargin.Get(endSide).IsAuto()) {
+      // We set this to 0 for now, and fix it up later in
+      // InitAbsoluteConstraints (which is caller of this function, via
+      // CalculateHypotheticalPosition).
+      end = 0;
+    } else {
+      end = nsLayoutUtils::ComputeCBDependentValue(
+          aContainingBlockSize, mStyleMargin->mMargin.Get(endSide));
+    }
+    marginStartEnd = start + end;
+  }
+
+  nscoord outside = paddingStartEnd + borderStartEnd + marginStartEnd;
+  nscoord inside = 0;
+  if (mStylePosition->mBoxSizing == StyleBoxSizing::Border) {
+    inside = borderStartEnd + paddingStartEnd;
+  }
+  outside -= inside;
+  *aInsideBoxSizing = inside;
+  *aOutsideBoxSizing = outside;
+}
+
+/**
+ * Returns true iff a pre-order traversal of the normal child
+ * frames rooted at aFrame finds no non-empty frame before aDescendant.
+ */
+static bool AreAllEarlierInFlowFramesEmpty(nsIFrame* aFrame,
+                                           nsIFrame* aDescendant,
+                                           bool* aFound) {
+  if (aFrame == aDescendant) {
+    *aFound = true;
+    return true;
+  }
+  if (aFrame->IsPlaceholderFrame()) {
+    auto ph = static_cast<nsPlaceholderFrame*>(aFrame);
+    MOZ_ASSERT(ph->IsSelfEmpty() && ph->PrincipalChildList().IsEmpty());
+    ph->SetLineIsEmptySoFar(true);
+  } else {
+    if (!aFrame->IsSelfEmpty()) {
+      *aFound = false;
+      return false;
+    }
+    for (nsIFrame* f : aFrame->PrincipalChildList()) {
+      bool allEmpty = AreAllEarlierInFlowFramesEmpty(f, aDescendant, aFound);
+      if (*aFound || !allEmpty) {
+        return allEmpty;
+      }
+    }
+  }
+  *aFound = false;
+  return true;
+}
+
+static bool AxisPolarityFlipped(LogicalAxis aThisAxis, WritingMode aThisWm,
+                                WritingMode aOtherWm) {
+  if (MOZ_LIKELY(aThisWm == aOtherWm)) {
+    // Dedicated short circuit for the common case.
+    return false;
+  }
+  LogicalAxis otherAxis = aThisWm.IsOrthogonalTo(aOtherWm)
+                              ? GetOrthogonalAxis(aThisAxis)
+                              : aThisAxis;
+  NS_ASSERTION(
+      aThisWm.PhysicalAxis(aThisAxis) == aOtherWm.PhysicalAxis(otherAxis),
+      "Physical axes must match!");
+  Side thisStartSide =
+      aThisWm.PhysicalSide(MakeLogicalSide(aThisAxis, eLogicalEdgeStart));
+  Side otherStartSide =
+      aOtherWm.PhysicalSide(MakeLogicalSide(otherAxis, eLogicalEdgeStart));
+  return thisStartSide != otherStartSide;
+}
+
+static bool InlinePolarityFlipped(WritingMode aThisWm, WritingMode aOtherWm) {
+  return AxisPolarityFlipped(eLogicalAxisInline, aThisWm, aOtherWm);
+}
+
+static bool BlockPolarityFlipped(WritingMode aThisWm, WritingMode aOtherWm) {
+  return AxisPolarityFlipped(eLogicalAxisBlock, aThisWm, aOtherWm);
+}
+
+// Calculate the position of the hypothetical box that the element would have
+// if it were in the flow.
+// The values returned are relative to the padding edge of the absolute
+// containing block. The writing-mode of the hypothetical box position will
+// have the same block direction as the absolute containing block, but may
+// differ in inline-bidi direction.
+// In the code below, |aCBReflowInput->frame| is the absolute containing block,
+// while |containingBlock| is the nearest block container of the placeholder
+// frame, which may be different from the absolute containing block.
+void ReflowInput::CalculateHypotheticalPosition(
+    nsPresContext* aPresContext, nsPlaceholderFrame* aPlaceholderFrame,
+    const ReflowInput* aCBReflowInput, nsHypotheticalPosition& aHypotheticalPos,
+    LayoutFrameType aFrameType) const {
+  NS_ASSERTION(mStyleDisplay->mOriginalDisplay != StyleDisplay::None,
+               "mOriginalDisplay has not been properly initialized");
+
+  // Find the nearest containing block frame to the placeholder frame,
+  // and its inline-start edge and width.
+  nscoord blockIStartContentEdge;
+  // Dummy writing mode for blockContentSize, will be changed as needed by
+  // GetHypotheticalBoxContainer.
+  WritingMode cbwm = aCBReflowInput->GetWritingMode();
+  LogicalSize blockContentSize(cbwm);
+  nsIFrame* containingBlock = GetHypotheticalBoxContainer(
+      aPlaceholderFrame, blockIStartContentEdge, blockContentSize);
+  // Now blockContentSize is in containingBlock's writing mode.
+
+  // If it's a replaced element and it has a 'auto' value for
+  //'inline size', see if we can get the intrinsic size. This will allow
+  // us to exactly determine both the inline edges
+  WritingMode wm = containingBlock->GetWritingMode();
+
+  const auto& styleISize = mStylePosition->ISize(wm);
+  bool isAutoISize = styleISize.IsAuto();
+  Maybe<nsSize> intrinsicSize;
+  if (mFlags.mIsReplaced && isAutoISize) {
+    // See if we can get the intrinsic size of the element
+    intrinsicSize = mFrame->GetIntrinsicSize().ToSize();
+  }
+
+  // See if we can calculate what the box inline size would have been if
+  // the element had been in the flow
+  Maybe<nscoord> boxISize;
+  if (mStyleDisplay->IsOriginalDisplayInlineOutside() && !mFlags.mIsReplaced) {
+    // For non-replaced inline-level elements the 'inline size' property
+    // doesn't apply, so we don't know what the inline size would have
+    // been without reflowing it
+
+  } else {
+    // It's either a replaced inline-level element or a block-level element
+
+    // Determine the total amount of inline direction
+    // border/padding/margin that the element would have had if it had
+    // been in the flow. Note that we ignore any 'auto' and 'inherit'
+    // values
+    nscoord insideBoxISizing, outsideBoxISizing;
+    CalculateBorderPaddingMargin(eLogicalAxisInline, blockContentSize.ISize(wm),
+                                 &insideBoxISizing, &outsideBoxISizing);
+
+    if (mFlags.mIsReplaced && isAutoISize) {
+      // It's a replaced element with an 'auto' inline size so the box
+      // inline size is its intrinsic size plus any border/padding/margin
+      if (intrinsicSize) {
+        boxISize.emplace(LogicalSize(wm, *intrinsicSize).ISize(wm) +
+                         outsideBoxISizing + insideBoxISizing);
+      }
+
+    } else if (isAutoISize) {
+      // The box inline size is the containing block inline size
+      boxISize.emplace(blockContentSize.ISize(wm));
+    } else {
+      // We need to compute it. It's important we do this, because if it's
+      // percentage based this computed value may be different from the computed
+      // value calculated using the absolute containing block width
+      nscoord insideBoxBSizing, dummy;
+      CalculateBorderPaddingMargin(eLogicalAxisBlock,
+                                   blockContentSize.ISize(wm),
+                                   &insideBoxBSizing, &dummy);
+      boxISize.emplace(
+          ComputeISizeValue(wm, blockContentSize,
+                            LogicalSize(wm, insideBoxISizing, insideBoxBSizing),
+                            outsideBoxISizing, styleISize) +
+          insideBoxISizing + outsideBoxISizing);
+    }
+  }
+
+  // Get the placeholder x-offset and y-offset in the coordinate
+  // space of its containing block
+  // XXXbz the placeholder is not fully reflowed yet if our containing block is
+  // relatively positioned...
+  nsSize containerSize =
+      containingBlock->HasAnyStateBits(NS_FRAME_IN_REFLOW)
+          ? aCBReflowInput->ComputedSizeAsContainerIfConstrained()
+          : containingBlock->GetSize();
+  LogicalPoint placeholderOffset(
+      wm, aPlaceholderFrame->GetOffsetToIgnoringScrolling(containingBlock),
+      containerSize);
+
+  // First, determine the hypothetical box's mBStart.  We want to check the
+  // content insertion frame of containingBlock for block-ness, but make
+  // sure to compute all coordinates in the coordinate system of
+  // containingBlock.
+  nsBlockFrame* blockFrame =
+      do_QueryFrame(containingBlock->GetContentInsertionFrame());
+  if (blockFrame) {
+    // Use a null containerSize to convert a LogicalPoint functioning as a
+    // vector into a physical nsPoint vector.
+    const nsSize nullContainerSize;
+    LogicalPoint blockOffset(
+        wm, blockFrame->GetOffsetToIgnoringScrolling(containingBlock),
+        nullContainerSize);
+    bool isValid;
+    nsBlockInFlowLineIterator iter(blockFrame, aPlaceholderFrame, &isValid);
+    if (!isValid) {
+      // Give up.  We're probably dealing with somebody using
+      // position:absolute inside native-anonymous content anyway.
+      aHypotheticalPos.mBStart = placeholderOffset.B(wm);
+    } else {
+      NS_ASSERTION(iter.GetContainer() == blockFrame,
+                   "Found placeholder in wrong block!");
+      nsBlockFrame::LineIterator lineBox = iter.GetLine();
+
+      // How we determine the hypothetical box depends on whether the element
+      // would have been inline-level or block-level
+      LogicalRect lineBounds = lineBox->GetBounds().ConvertTo(
+          wm, lineBox->mWritingMode, lineBox->mContainerSize);
+      if (mStyleDisplay->IsOriginalDisplayInlineOutside()) {
+        // Use the block-start of the inline box which the placeholder lives in
+        // as the hypothetical box's block-start.
+        aHypotheticalPos.mBStart = lineBounds.BStart(wm) + blockOffset.B(wm);
+      } else {
+        // The element would have been block-level which means it would
+        // be below the line containing the placeholder frame, unless
+        // all the frames before it are empty.  In that case, it would
+        // have been just before this line.
+        // XXXbz the line box is not fully reflowed yet if our
+        // containing block is relatively positioned...
+        if (lineBox != iter.End()) {
+          nsIFrame* firstFrame = lineBox->mFirstChild;
+          bool allEmpty = false;
+          if (firstFrame == aPlaceholderFrame) {
+            aPlaceholderFrame->SetLineIsEmptySoFar(true);
+            allEmpty = true;
+          } else {
+            auto prev = aPlaceholderFrame->GetPrevSibling();
+            if (prev && prev->IsPlaceholderFrame()) {
+              auto ph = static_cast<nsPlaceholderFrame*>(prev);
+              if (ph->GetLineIsEmptySoFar(&allEmpty)) {
+                aPlaceholderFrame->SetLineIsEmptySoFar(allEmpty);
+              }
+            }
+          }
+          if (!allEmpty) {
+            bool found = false;
+            while (firstFrame) {  // See bug 223064
+              allEmpty = AreAllEarlierInFlowFramesEmpty(
+                  firstFrame, aPlaceholderFrame, &found);
+              if (found || !allEmpty) {
+                break;
+              }
+              firstFrame = firstFrame->GetNextSibling();
+            }
+            aPlaceholderFrame->SetLineIsEmptySoFar(allEmpty);
+          }
+          NS_ASSERTION(firstFrame, "Couldn't find placeholder!");
+
+          if (allEmpty) {
+            // The top of the hypothetical box is the top of the line
+            // containing the placeholder, since there is nothing in the
+            // line before our placeholder except empty frames.
+            aHypotheticalPos.mBStart =
+                lineBounds.BStart(wm) + blockOffset.B(wm);
+          } else {
+            // The top of the hypothetical box is just below the line
+            // containing the placeholder.
+            aHypotheticalPos.mBStart = lineBounds.BEnd(wm) + blockOffset.B(wm);
+          }
+        } else {
+          // Just use the placeholder's block-offset wrt the containing block
+          aHypotheticalPos.mBStart = placeholderOffset.B(wm);
+        }
+      }
+    }
+  } else {
+    // The containing block is not a block, so it's probably something
+    // like a XUL box, etc.
+    // Just use the placeholder's block-offset
+    aHypotheticalPos.mBStart = placeholderOffset.B(wm);
+  }
+
+  // Second, determine the hypothetical box's mIStart.
+  // How we determine the hypothetical box depends on whether the element
+  // would have been inline-level or block-level
+  if (mStyleDisplay->IsOriginalDisplayInlineOutside() ||
+      mFlags.mIOffsetsNeedCSSAlign) {
+    // The placeholder represents the IStart edge of the hypothetical box.
+    // (Or if mFlags.mIOffsetsNeedCSSAlign is set, it represents the IStart
+    // edge of the Alignment Container.)
+    aHypotheticalPos.mIStart = placeholderOffset.I(wm);
+  } else {
+    aHypotheticalPos.mIStart = blockIStartContentEdge;
+  }
+
+  // The current coordinate space is that of the nearest block to the
+  // placeholder. Convert to the coordinate space of the absolute containing
+  // block.
+  nsPoint cbOffset =
+      containingBlock->GetOffsetToIgnoringScrolling(aCBReflowInput->mFrame);
+
+  nsSize reflowSize = aCBReflowInput->ComputedSizeAsContainerIfConstrained();
+  LogicalPoint logCBOffs(wm, cbOffset, reflowSize - containerSize);
+  aHypotheticalPos.mIStart += logCBOffs.I(wm);
+  aHypotheticalPos.mBStart += logCBOffs.B(wm);
+
+  // If block direction doesn't match (whether orthogonal or antiparallel),
+  // we'll have to convert aHypotheticalPos to be in terms of cbwm.
+  // This upcoming conversion must be taken into account for border offsets.
+  const bool hypotheticalPosWillUseCbwm =
+      cbwm.GetBlockDir() != wm.GetBlockDir();
+  // The specified offsets are relative to the absolute containing block's
+  // padding edge and our current values are relative to the border edge, so
+  // translate.
+  const LogicalMargin border = aCBReflowInput->ComputedLogicalBorder(wm);
+  if (hypotheticalPosWillUseCbwm && InlinePolarityFlipped(wm, cbwm)) {
+    aHypotheticalPos.mIStart += border.IEnd(wm);
+  } else {
+    aHypotheticalPos.mIStart -= border.IStart(wm);
+  }
+
+  if (hypotheticalPosWillUseCbwm && BlockPolarityFlipped(wm, cbwm)) {
+    aHypotheticalPos.mBStart += border.BEnd(wm);
+  } else {
+    aHypotheticalPos.mBStart -= border.BStart(wm);
+  }
+  // At this point, we have computed aHypotheticalPos using the writing mode
+  // of the placeholder's containing block.
+
+  if (hypotheticalPosWillUseCbwm) {
+    // If the block direction we used in calculating aHypotheticalPos does not
+    // match the absolute containing block's, we need to convert here so that
+    // aHypotheticalPos is usable in relation to the absolute containing block.
+    // This requires computing or measuring the abspos frame's block-size,
+    // which is not otherwise required/used here (as aHypotheticalPos
+    // records only the block-start coordinate).
+
+    // This is similar to the inline-size calculation for a replaced
+    // inline-level element or a block-level element (above), except that
+    // 'auto' sizing is handled differently in the block direction for non-
+    // replaced elements and replaced elements lacking an intrinsic size.
+
+    // Determine the total amount of block direction
+    // border/padding/margin that the element would have had if it had
+    // been in the flow. Note that we ignore any 'auto' and 'inherit'
+    // values.
+    nscoord insideBoxSizing, outsideBoxSizing;
+    CalculateBorderPaddingMargin(eLogicalAxisBlock, blockContentSize.BSize(wm),
+                                 &insideBoxSizing, &outsideBoxSizing);
+
+    nscoord boxBSize;
+    const auto& styleBSize = mStylePosition->BSize(wm);
+    if (styleBSize.BehavesLikeInitialValueOnBlockAxis()) {
+      if (mFlags.mIsReplaced && intrinsicSize) {
+        // It's a replaced element with an 'auto' block size so the box
+        // block size is its intrinsic size plus any border/padding/margin
+        boxBSize = LogicalSize(wm, *intrinsicSize).BSize(wm) +
+                   outsideBoxSizing + insideBoxSizing;
+      } else {
+        // XXX Bug 1191801
+        // Figure out how to get the correct boxBSize here (need to reflow the
+        // positioned frame?)
+        boxBSize = 0;
+      }
+    } else {
+      // We need to compute it. It's important we do this, because if it's
+      // percentage-based this computed value may be different from the
+      // computed value calculated using the absolute containing block height.
+      boxBSize = nsLayoutUtils::ComputeBSizeValue(
+                     blockContentSize.BSize(wm), insideBoxSizing,
+                     styleBSize.AsLengthPercentage()) +
+                 insideBoxSizing + outsideBoxSizing;
+    }
+
+    LogicalSize boxSize(wm, boxISize.valueOr(0), boxBSize);
+
+    LogicalPoint origin(wm, aHypotheticalPos.mIStart, aHypotheticalPos.mBStart);
+    origin =
+        origin.ConvertTo(cbwm, wm, reflowSize - boxSize.GetPhysicalSize(wm));
+
+    aHypotheticalPos.mIStart = origin.I(cbwm);
+    aHypotheticalPos.mBStart = origin.B(cbwm);
+    aHypotheticalPos.mWritingMode = cbwm;
+  } else {
+    aHypotheticalPos.mWritingMode = wm;
+  }
+}
+
+bool ReflowInput::IsInlineSizeComputableByBlockSizeAndAspectRatio(
+    nscoord aBlockSize) const {
+  WritingMode wm = GetWritingMode();
+  MOZ_ASSERT(!mStylePosition->mOffset.GetBStart(wm).IsAuto() &&
+                 !mStylePosition->mOffset.GetBEnd(wm).IsAuto(),
+             "If any of the block-start and block-end are auto, aBlockSize "
+             "doesn't make sense");
+  NS_WARNING_ASSERTION(
+      aBlockSize >= 0 && aBlockSize != NS_UNCONSTRAINEDSIZE,
+      "The caller shouldn't give us an unresolved or invalid block size");
+
+  if (!mStylePosition->mAspectRatio.HasFiniteRatio()) {
+    return false;
+  }
+
+  // We don't have to compute the inline size by aspect-ratio and the resolved
+  // block size (from insets) for replaced elements.
+  if (mFrame->IsReplaced()) {
+    return false;
+  }
+
+  // If inline size is specified, we should have it by mFrame->ComputeSize()
+  // already.
+  if (mStylePosition->ISize(wm).IsLengthPercentage()) {
+    return false;
+  }
+
+  // If both inline insets are non-auto, mFrame->ComputeSize() should get a
+  // possible inline size by those insets, so we don't rely on aspect-ratio.
+  if (!mStylePosition->mOffset.GetIStart(wm).IsAuto() &&
+      !mStylePosition->mOffset.GetIEnd(wm).IsAuto()) {
+    return false;
+  }
+
+  // Just an error handling. If |aBlockSize| is NS_UNCONSTRAINEDSIZE, there must
+  // be something wrong, and we don't want to continue the calculation for
+  // aspect-ratio. So we return false if this happens.
+  return aBlockSize != NS_UNCONSTRAINEDSIZE;
+}
+
+// FIXME: Move this into nsIFrame::ComputeSize() if possible, so most of the
+// if-checks can be simplier.
+LogicalSize ReflowInput::CalculateAbsoluteSizeWithResolvedAutoBlockSize(
+    nscoord aAutoBSize, const LogicalSize& aTentativeComputedSize) {
+  LogicalSize resultSize = aTentativeComputedSize;
+  WritingMode wm = GetWritingMode();
+
+  // Two cases we don't want to early return:
+  // 1. If the block size behaves as initial value and we haven't resolved it in
+  //    ComputeSize() yet, we need to apply |aAutoBSize|.
+  //    Also, we check both computed style and |resultSize.BSize(wm)| to avoid
+  //    applying |aAutoBSize| when the resolved block size is saturated at
+  //    nscoord_MAX, and wrongly treated as NS_UNCONSTRAINEDSIZE because of a
+  //    giant specified block-size.
+  // 2. If the block size needs to be computed via aspect-ratio and
+  //    |aAutoBSize|, we need to apply |aAutoBSize|. In this case,
+  //    |resultSize.BSize(wm)| may not be NS_UNCONSTRAINEDSIZE because we apply
+  //    aspect-ratio in ComputeSize() for block axis by default, so we have to
+  //    check its computed style.
+  const bool bSizeBehavesAsInitial =
+      mStylePosition->BSize(wm).BehavesLikeInitialValueOnBlockAxis();
+  const bool bSizeIsStillUnconstrained =
+      bSizeBehavesAsInitial && resultSize.BSize(wm) == NS_UNCONSTRAINEDSIZE;
+  const bool needsComputeInlineSizeByAspectRatio =
+      bSizeBehavesAsInitial &&
+      IsInlineSizeComputableByBlockSizeAndAspectRatio(aAutoBSize);
+  if (!bSizeIsStillUnconstrained && !needsComputeInlineSizeByAspectRatio) {
+    return resultSize;
+  }
+
+  // For non-replaced elements with block-size auto, the block-size
+  // fills the remaining space, and we clamp it by min/max size constraints.
+  resultSize.BSize(wm) = ApplyMinMaxBSize(aAutoBSize);
+
+  if (!needsComputeInlineSizeByAspectRatio) {
+    return resultSize;
+  }
+
+  // Calculate transferred inline size through aspect-ratio.
+  // For non-replaced elements, we always take box-sizing into account.
+  const auto boxSizingAdjust =
+      mStylePosition->mBoxSizing == StyleBoxSizing::Border
+          ? ComputedLogicalBorderPadding(wm).Size(wm)
+          : LogicalSize(wm);
+  auto transferredISize =
+      mStylePosition->mAspectRatio.ToLayoutRatio().ComputeRatioDependentSize(
+          LogicalAxis::eLogicalAxisInline, wm, aAutoBSize, boxSizingAdjust);
+  resultSize.ISize(wm) = ApplyMinMaxISize(transferredISize);
+
+  MOZ_ASSERT(mFlags.mIsBSizeSetByAspectRatio,
+             "This flag should have been set because nsIFrame::ComputeSize() "
+             "returns AspectRatioUsage::ToComputeBSize unconditionally for "
+             "auto block-size");
+  mFlags.mIsBSizeSetByAspectRatio = false;
+
+  return resultSize;
+}
+
+void ReflowInput::InitAbsoluteConstraints(nsPresContext* aPresContext,
+                                          const ReflowInput* aCBReflowInput,
+                                          const LogicalSize& aCBSize,
+                                          LayoutFrameType aFrameType) {
+  WritingMode wm = GetWritingMode();
+  WritingMode cbwm = aCBReflowInput->GetWritingMode();
+  NS_WARNING_ASSERTION(aCBSize.BSize(cbwm) != NS_UNCONSTRAINEDSIZE,
+                       "containing block bsize must be constrained");
+
+  NS_ASSERTION(aFrameType != LayoutFrameType::Table,
+               "InitAbsoluteConstraints should not be called on table frames");
+  NS_ASSERTION(mFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW),
+               "Why are we here?");
+
+  const auto& styleOffset = mStylePosition->mOffset;
+  bool iStartIsAuto = styleOffset.GetIStart(cbwm).IsAuto();
+  bool iEndIsAuto = styleOffset.GetIEnd(cbwm).IsAuto();
+  bool bStartIsAuto = styleOffset.GetBStart(cbwm).IsAuto();
+  bool bEndIsAuto = styleOffset.GetBEnd(cbwm).IsAuto();
+
+  // If both 'left' and 'right' are 'auto' or both 'top' and 'bottom' are
+  // 'auto', then compute the hypothetical box position where the element would
+  // have been if it had been in the flow
+  nsHypotheticalPosition hypotheticalPos;
+  if ((iStartIsAuto && iEndIsAuto) || (bStartIsAuto && bEndIsAuto)) {
+    nsPlaceholderFrame* placeholderFrame = mFrame->GetPlaceholderFrame();
+    MOZ_ASSERT(placeholderFrame, "no placeholder frame");
+    nsIFrame* placeholderParent = placeholderFrame->GetParent();
+    MOZ_ASSERT(placeholderParent, "shouldn't have unparented placeholders");
+
+    if (placeholderFrame->HasAnyStateBits(
+            PLACEHOLDER_STATICPOS_NEEDS_CSSALIGN)) {
+      MOZ_ASSERT(placeholderParent->IsFlexOrGridContainer(),
+                 "This flag should only be set on grid/flex children");
+      // If the (as-yet unknown) static position will determine the inline
+      // and/or block offsets, set flags to note those offsets aren't valid
+      // until we can do CSS Box Alignment on the OOF frame.
+      mFlags.mIOffsetsNeedCSSAlign = (iStartIsAuto && iEndIsAuto);
+      mFlags.mBOffsetsNeedCSSAlign = (bStartIsAuto && bEndIsAuto);
+    }
+
+    if (mFlags.mStaticPosIsCBOrigin) {
+      hypotheticalPos.mWritingMode = cbwm;
+      hypotheticalPos.mIStart = nscoord(0);
+      hypotheticalPos.mBStart = nscoord(0);
+      if (placeholderParent->IsGridContainerFrame() &&
+          placeholderParent->HasAnyStateBits(NS_STATE_GRID_IS_COL_MASONRY |
+                                             NS_STATE_GRID_IS_ROW_MASONRY)) {
+        // Disable CSS alignment in Masonry layout since we don't have real grid
+        // areas in that axis.  We'll use the placeholder position instead as it
+        // was calculated by nsGridContainerFrame::MasonryLayout.
+        auto cbsz = aCBSize.GetPhysicalSize(cbwm);
+        LogicalPoint pos = placeholderFrame->GetLogicalPosition(cbwm, cbsz);
+        if (placeholderParent->HasAnyStateBits(NS_STATE_GRID_IS_COL_MASONRY)) {
+          mFlags.mIOffsetsNeedCSSAlign = false;
+          hypotheticalPos.mIStart = pos.I(cbwm);
+        } else {
+          mFlags.mBOffsetsNeedCSSAlign = false;
+          hypotheticalPos.mBStart = pos.B(cbwm);
+        }
+      }
+    } else {
+      // XXXmats all this is broken for orthogonal writing-modes: bug 1521988.
+      CalculateHypotheticalPosition(aPresContext, placeholderFrame,
+                                    aCBReflowInput, hypotheticalPos,
+                                    aFrameType);
+      if (aCBReflowInput->mFrame->IsGridContainerFrame()) {
+        // 'hypotheticalPos' is relative to the padding rect of the CB *frame*.
+        // In grid layout the CB is the grid area rectangle, so we translate
+        // 'hypotheticalPos' to be relative that rectangle here.
+        nsRect cb = nsGridContainerFrame::GridItemCB(mFrame);
+        nscoord left(0);
+        nscoord right(0);
+        if (cbwm.IsBidiLTR()) {
+          left = cb.X();
+        } else {
+          right = aCBReflowInput->ComputedWidth() +
+                  aCBReflowInput->ComputedPhysicalPadding().LeftRight() -
+                  cb.XMost();
+        }
+        LogicalMargin offsets(cbwm, nsMargin(cb.Y(), right, nscoord(0), left));
+        hypotheticalPos.mIStart -= offsets.IStart(cbwm);
+        hypotheticalPos.mBStart -= offsets.BStart(cbwm);
+      }
+    }
+  }
+
+  // Initialize the 'left' and 'right' computed offsets
+  // XXX Handle new 'static-position' value...
+
+  // Size of the containing block in its writing mode
+  LogicalSize cbSize = aCBSize;
+  LogicalMargin offsets = ComputedLogicalOffsets(cbwm);
+
+  if (iStartIsAuto) {
+    offsets.IStart(cbwm) = 0;
+  } else {
+    offsets.IStart(cbwm) = nsLayoutUtils::ComputeCBDependentValue(
+        cbSize.ISize(cbwm), styleOffset.GetIStart(cbwm));
+  }
+  if (iEndIsAuto) {
+    offsets.IEnd(cbwm) = 0;
+  } else {
+    offsets.IEnd(cbwm) = nsLayoutUtils::ComputeCBDependentValue(
+        cbSize.ISize(cbwm), styleOffset.GetIEnd(cbwm));
+  }
+
+  if (iStartIsAuto && iEndIsAuto) {
+    if (cbwm.IsBidiLTR() != hypotheticalPos.mWritingMode.IsBidiLTR()) {
+      offsets.IEnd(cbwm) = hypotheticalPos.mIStart;
+      iEndIsAuto = false;
+    } else {
+      offsets.IStart(cbwm) = hypotheticalPos.mIStart;
+      iStartIsAuto = false;
+    }
+  }
+
+  if (bStartIsAuto) {
+    offsets.BStart(cbwm) = 0;
+  } else {
+    offsets.BStart(cbwm) = nsLayoutUtils::ComputeBSizeDependentValue(
+        cbSize.BSize(cbwm), styleOffset.GetBStart(cbwm));
+  }
+  if (bEndIsAuto) {
+    offsets.BEnd(cbwm) = 0;
+  } else {
+    offsets.BEnd(cbwm) = nsLayoutUtils::ComputeBSizeDependentValue(
+        cbSize.BSize(cbwm), styleOffset.GetBEnd(cbwm));
+  }
+
+  if (bStartIsAuto && bEndIsAuto) {
+    // Treat 'top' like 'static-position'
+    offsets.BStart(cbwm) = hypotheticalPos.mBStart;
+    bStartIsAuto = false;
+  }
+
+  SetComputedLogicalOffsets(cbwm, offsets);
+
+  if (wm.IsOrthogonalTo(cbwm)) {
+    if (bStartIsAuto || bEndIsAuto) {
+      mComputeSizeFlags += ComputeSizeFlag::ShrinkWrap;
+    }
+  } else {
+    if (iStartIsAuto || iEndIsAuto) {
+      mComputeSizeFlags += ComputeSizeFlag::ShrinkWrap;
+    }
+  }
+
+  nsIFrame::SizeComputationResult sizeResult = {
+      LogicalSize(wm), nsIFrame::AspectRatioUsage::None};
+  {
+    AutoMaybeDisableFontInflation an(mFrame);
+
+    sizeResult = mFrame->ComputeSize(
+        mRenderingContext, wm, cbSize.ConvertTo(wm, cbwm),
+        cbSize.ConvertTo(wm, cbwm).ISize(wm),  // XXX or AvailableISize()?
+        ComputedLogicalMargin(wm).Size(wm) +
+            ComputedLogicalOffsets(wm).Size(wm),
+        ComputedLogicalBorderPadding(wm).Size(wm), {}, mComputeSizeFlags);
+    mComputedSize = sizeResult.mLogicalSize;
+    NS_ASSERTION(ComputedISize() >= 0, "Bogus inline-size");
+    NS_ASSERTION(
+        ComputedBSize() == NS_UNCONSTRAINEDSIZE || ComputedBSize() >= 0,
+        "Bogus block-size");
+  }
+
+  LogicalSize& computedSize = sizeResult.mLogicalSize;
+  computedSize = computedSize.ConvertTo(cbwm, wm);
+
+  mFlags.mIsBSizeSetByAspectRatio = sizeResult.mAspectRatioUsage ==
+                                    nsIFrame::AspectRatioUsage::ToComputeBSize;
+
+  // XXX Now that we have ComputeSize, can we condense many of the
+  // branches off of widthIsAuto?
+
+  LogicalMargin margin = ComputedLogicalMargin(cbwm);
+  const LogicalMargin borderPadding = ComputedLogicalBorderPadding(cbwm);
+
+  bool iSizeIsAuto = mStylePosition->ISize(cbwm).IsAuto();
+  bool marginIStartIsAuto = false;
+  bool marginIEndIsAuto = false;
+  bool marginBStartIsAuto = false;
+  bool marginBEndIsAuto = false;
+  if (iStartIsAuto) {
+    // We know 'right' is not 'auto' anymore thanks to the hypothetical
+    // box code above.
+    // Solve for 'left'.
+    if (iSizeIsAuto) {
+      // XXXldb This, and the corresponding code in
+      // nsAbsoluteContainingBlock.cpp, could probably go away now that
+      // we always compute widths.
+      offsets.IStart(cbwm) = NS_AUTOOFFSET;
+    } else {
+      offsets.IStart(cbwm) = cbSize.ISize(cbwm) - offsets.IEnd(cbwm) -
+                             computedSize.ISize(cbwm) - margin.IStartEnd(cbwm) -
+                             borderPadding.IStartEnd(cbwm);
+    }
+  } else if (iEndIsAuto) {
+    // We know 'left' is not 'auto' anymore thanks to the hypothetical
+    // box code above.
+    // Solve for 'right'.
+    if (iSizeIsAuto) {
+      // XXXldb This, and the corresponding code in
+      // nsAbsoluteContainingBlock.cpp, could probably go away now that
+      // we always compute widths.
+      offsets.IEnd(cbwm) = NS_AUTOOFFSET;
+    } else {
+      offsets.IEnd(cbwm) = cbSize.ISize(cbwm) - offsets.IStart(cbwm) -
+                           computedSize.ISize(cbwm) - margin.IStartEnd(cbwm) -
+                           borderPadding.IStartEnd(cbwm);
+    }
+  } else if (!mFrame->HasIntrinsicKeywordForBSize() ||
+             !wm.IsOrthogonalTo(cbwm)) {
+    // Neither 'inline-start' nor 'inline-end' is 'auto'.
+    if (wm.IsOrthogonalTo(cbwm)) {
+      // For orthogonal blocks, we need to handle the case where the block had
+      // unconstrained block-size, which mapped to unconstrained inline-size
+      // in the containing block's writing mode.
+      nscoord autoISize = cbSize.ISize(cbwm) - margin.IStartEnd(cbwm) -
+                          borderPadding.IStartEnd(cbwm) -
+                          offsets.IStartEnd(cbwm);
+      autoISize = std::max(autoISize, 0);
+      // FIXME: Bug 1602669: if |autoISize| happens to be numerically equal to
+      // NS_UNCONSTRAINEDSIZE, we may get some unexpected behavior. We need a
+      // better way to distinguish between unconstrained size and resolved
+      // size.
+      NS_WARNING_ASSERTION(autoISize != NS_UNCONSTRAINEDSIZE,
+                           "Unexpected size from inline-start and inline-end");
+
+      nscoord autoBSizeInWM = autoISize;
+      LogicalSize computedSizeInWM =
+          CalculateAbsoluteSizeWithResolvedAutoBlockSize(
+              autoBSizeInWM, computedSize.ConvertTo(wm, cbwm));
+      computedSize = computedSizeInWM.ConvertTo(cbwm, wm);
+    }
+
+    // However, the inline-size might
+    // still not fill all the available space (even though we didn't
+    // shrink-wrap) in case:
+    //  * inline-size was specified
+    //  * we're dealing with a replaced element
+    //  * width was constrained by min- or max-inline-size.
+
+    nscoord availMarginSpace =
+        aCBSize.ISize(cbwm) - offsets.IStartEnd(cbwm) - margin.IStartEnd(cbwm) -
+        borderPadding.IStartEnd(cbwm) - computedSize.ISize(cbwm);
+    marginIStartIsAuto = mStyleMargin->mMargin.GetIStart(cbwm).IsAuto();
+    marginIEndIsAuto = mStyleMargin->mMargin.GetIEnd(cbwm).IsAuto();
+    ComputeAbsPosInlineAutoMargin(availMarginSpace, cbwm, marginIStartIsAuto,
+                                  marginIEndIsAuto, margin, offsets);
+  }
+
+  bool bSizeIsAuto =
+      mStylePosition->BSize(cbwm).BehavesLikeInitialValueOnBlockAxis();
+  if (bStartIsAuto) {
+    // solve for block-start
+    if (bSizeIsAuto) {
+      offsets.BStart(cbwm) = NS_AUTOOFFSET;
+    } else {
+      offsets.BStart(cbwm) = cbSize.BSize(cbwm) - margin.BStartEnd(cbwm) -
+                             borderPadding.BStartEnd(cbwm) -
+                             computedSize.BSize(cbwm) - offsets.BEnd(cbwm);
+    }
+  } else if (bEndIsAuto) {
+    // solve for block-end
+    if (bSizeIsAuto) {
+      offsets.BEnd(cbwm) = NS_AUTOOFFSET;
+    } else {
+      offsets.BEnd(cbwm) = cbSize.BSize(cbwm) - margin.BStartEnd(cbwm) -
+                           borderPadding.BStartEnd(cbwm) -
+                           computedSize.BSize(cbwm) - offsets.BStart(cbwm);
+    }
+  } else if (!mFrame->HasIntrinsicKeywordForBSize() ||
+             wm.IsOrthogonalTo(cbwm)) {
+    // Neither block-start nor -end is 'auto'.
+    nscoord autoBSize = cbSize.BSize(cbwm) - margin.BStartEnd(cbwm) -
+                        borderPadding.BStartEnd(cbwm) - offsets.BStartEnd(cbwm);
+    autoBSize = std::max(autoBSize, 0);
+    // FIXME: Bug 1602669: if |autoBSize| happens to be numerically equal to
+    // NS_UNCONSTRAINEDSIZE, we may get some unexpected behavior. We need a
+    // better way to distinguish between unconstrained size and resolved size.
+    NS_WARNING_ASSERTION(autoBSize != NS_UNCONSTRAINEDSIZE,
+                         "Unexpected size from block-start and block-end");
+
+    // For orthogonal case, the inline size in |wm| should have been handled by
+    // ComputeSize(). In other words, we only have to apply |autoBSize| to
+    // the computed size if this value can represent the block size in |wm|.
+    if (!wm.IsOrthogonalTo(cbwm)) {
+      // We handle the unconstrained block-size in current block's writing
+      // mode 'wm'.
+      LogicalSize computedSizeInWM =
+          CalculateAbsoluteSizeWithResolvedAutoBlockSize(
+              autoBSize, computedSize.ConvertTo(wm, cbwm));
+      computedSize = computedSizeInWM.ConvertTo(cbwm, wm);
+    }
+
+    // The block-size might still not fill all the available space in case:
+    //  * bsize was specified
+    //  * we're dealing with a replaced element
+    //  * bsize was constrained by min- or max-bsize.
+    nscoord availMarginSpace = autoBSize - computedSize.BSize(cbwm);
+    marginBStartIsAuto = mStyleMargin->mMargin.GetBStart(cbwm).IsAuto();
+    marginBEndIsAuto = mStyleMargin->mMargin.GetBEnd(cbwm).IsAuto();
+
+    ComputeAbsPosBlockAutoMargin(availMarginSpace, cbwm, marginBStartIsAuto,
+                                 marginBEndIsAuto, margin, offsets);
+  }
+  mComputedSize = computedSize.ConvertTo(wm, cbwm);
+
+  SetComputedLogicalOffsets(cbwm, offsets);
+  SetComputedLogicalMargin(cbwm, margin);
+
+  // If we have auto margins, update our UsedMarginProperty. The property
+  // will have already been created by InitOffsets if it is needed.
+  if (marginIStartIsAuto || marginIEndIsAuto || marginBStartIsAuto ||
+      marginBEndIsAuto) {
+    nsMargin* propValue = mFrame->GetProperty(nsIFrame::UsedMarginProperty());
+    MOZ_ASSERT(propValue,
+               "UsedMarginProperty should have been created "
+               "by InitOffsets.");
+    *propValue = margin.GetPhysicalMargin(cbwm);
+  }
+}
+
+// This will not be converted to abstract coordinates because it's only
+// used in CalcQuirkContainingBlockHeight
+static nscoord GetBlockMarginBorderPadding(const ReflowInput* aReflowInput) {
+  nscoord result = 0;
+  if (!aReflowInput) return result;
+
+  // zero auto margins
+  nsMargin margin = aReflowInput->ComputedPhysicalMargin();
+  if (NS_AUTOMARGIN == margin.top) margin.top = 0;
+  if (NS_AUTOMARGIN == margin.bottom) margin.bottom = 0;
+
+  result += margin.top + margin.bottom;
+  result += aReflowInput->ComputedPhysicalBorderPadding().top +
+            aReflowInput->ComputedPhysicalBorderPadding().bottom;
+
+  return result;
+}
+
+/* Get the height based on the viewport of the containing block specified
+ * in aReflowInput when the containing block has mComputedHeight ==
+ * NS_UNCONSTRAINEDSIZE This will walk up the chain of containing blocks looking
+ * for a computed height until it finds the canvas frame, or it encounters a
+ * frame that is not a block, area, or scroll frame. This handles compatibility
+ * with IE (see bug 85016 and bug 219693)
+ *
+ * When we encounter scrolledContent block frames, we skip over them,
+ * since they are guaranteed to not be useful for computing the containing
+ * block.
+ *
+ * See also IsQuirkContainingBlockHeight.
+ */
+static nscoord CalcQuirkContainingBlockHeight(
+    const ReflowInput* aCBReflowInput) {
+  const ReflowInput* firstAncestorRI = nullptr;   // a candidate for html frame
+  const ReflowInput* secondAncestorRI = nullptr;  // a candidate for body frame
+
+  // initialize the default to NS_UNCONSTRAINEDSIZE as this is the containings
+  // block computed height when this function is called. It is possible that we
+  // don't alter this height especially if we are restricted to one level
+  nscoord result = NS_UNCONSTRAINEDSIZE;
+
+  const ReflowInput* ri = aCBReflowInput;
+  for (; ri; ri = ri->mParentReflowInput) {
+    LayoutFrameType frameType = ri->mFrame->Type();
+    // if the ancestor is auto height then skip it and continue up if it
+    // is the first block frame and possibly the body/html
+    if (LayoutFrameType::Block == frameType ||
+        LayoutFrameType::Scroll == frameType) {
+      secondAncestorRI = firstAncestorRI;
+      firstAncestorRI = ri;
+
+      // If the current frame we're looking at is positioned, we don't want to
+      // go any further (see bug 221784).  The behavior we want here is: 1) If
+      // not auto-height, use this as the percentage base.  2) If auto-height,
+      // keep looking, unless the frame is positioned.
+      if (NS_UNCONSTRAINEDSIZE == ri->ComputedHeight()) {
+        if (ri->mFrame->IsAbsolutelyPositioned(ri->mStyleDisplay)) {
+          break;
+        } else {
+          continue;
+        }
+      }
+    } else if (LayoutFrameType::Canvas == frameType) {
+      // Always continue on to the height calculation
+    } else if (LayoutFrameType::PageContent == frameType) {
+      nsIFrame* prevInFlow = ri->mFrame->GetPrevInFlow();
+      // only use the page content frame for a height basis if it is the first
+      // in flow
+      if (prevInFlow) break;
+    } else {
+      break;
+    }
+
+    // if the ancestor is the page content frame then the percent base is
+    // the avail height, otherwise it is the computed height
+    result = (LayoutFrameType::PageContent == frameType) ? ri->AvailableHeight()
+                                                         : ri->ComputedHeight();
+    // if unconstrained - don't sutract borders - would result in huge height
+    if (NS_UNCONSTRAINEDSIZE == result) return result;
+
+    // if we got to the canvas or page content frame, then subtract out
+    // margin/border/padding for the BODY and HTML elements
+    if ((LayoutFrameType::Canvas == frameType) ||
+        (LayoutFrameType::PageContent == frameType)) {
+      result -= GetBlockMarginBorderPadding(firstAncestorRI);
+      result -= GetBlockMarginBorderPadding(secondAncestorRI);
+
+#ifdef DEBUG
+      // make sure the first ancestor is the HTML and the second is the BODY
+      if (firstAncestorRI) {
+        nsIContent* frameContent = firstAncestorRI->mFrame->GetContent();
+        if (frameContent) {
+          NS_ASSERTION(frameContent->IsHTMLElement(nsGkAtoms::html),
+                       "First ancestor is not HTML");
+        }
+      }
+      if (secondAncestorRI) {
+        nsIContent* frameContent = secondAncestorRI->mFrame->GetContent();
+        if (frameContent) {
+          NS_ASSERTION(frameContent->IsHTMLElement(nsGkAtoms::body),
+                       "Second ancestor is not BODY");
+        }
+      }
+#endif
+
+    }
+    // if we got to the html frame (a block child of the canvas) ...
+    else if (LayoutFrameType::Block == frameType && ri->mParentReflowInput &&
+             ri->mParentReflowInput->mFrame->IsCanvasFrame()) {
+      // ... then subtract out margin/border/padding for the BODY element
+      result -= GetBlockMarginBorderPadding(secondAncestorRI);
+    }
+    break;
+  }
+
+  // Make sure not to return a negative height here!
+  return std::max(result, 0);
+}
+
+// Called by InitConstraints() to compute the containing block rectangle for
+// the element. Handles the special logic for absolutely positioned elements
+LogicalSize ReflowInput::ComputeContainingBlockRectangle(
+    nsPresContext* aPresContext, const ReflowInput* aContainingBlockRI) const {
+  // Unless the element is absolutely positioned, the containing block is
+  // formed by the content edge of the nearest block-level ancestor
+  LogicalSize cbSize = aContainingBlockRI->ComputedSize();
+
+  WritingMode wm = aContainingBlockRI->GetWritingMode();
+
+  if (aContainingBlockRI->mFlags.mTreatBSizeAsIndefinite) {
+    cbSize.BSize(wm) = NS_UNCONSTRAINEDSIZE;
+  } else if (aContainingBlockRI->mPercentageBasisInBlockAxis) {
+    MOZ_ASSERT(cbSize.BSize(wm) == NS_UNCONSTRAINEDSIZE,
+               "Why provide a percentage basis when the containing block's "
+               "block-size is definite?");
+    cbSize.BSize(wm) = *aContainingBlockRI->mPercentageBasisInBlockAxis;
+  }
+
+  if (((mFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW) &&
+        // XXXfr hack for making frames behave properly when in overflow
+        // container lists, see bug 154892; need to revisit later
+        !mFrame->GetPrevInFlow()) ||
+       (mFrame->IsTableFrame() &&
+        mFrame->GetParent()->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW))) &&
+      mStyleDisplay->IsAbsolutelyPositioned(mFrame)) {
+    // See if the ancestor is block-level or inline-level
+    const auto computedPadding = aContainingBlockRI->ComputedLogicalPadding(wm);
+    if (aContainingBlockRI->mStyleDisplay->IsInlineOutsideStyle()) {
+      // Base our size on the actual size of the frame.  In cases when this is
+      // completely bogus (eg initial reflow), this code shouldn't even be
+      // called, since the code in nsInlineFrame::Reflow will pass in
+      // the containing block dimensions to our constructor.
+      // XXXbz we should be taking the in-flows into account too, but
+      // that's very hard.
+
+      LogicalMargin computedBorder =
+          aContainingBlockRI->ComputedLogicalBorderPadding(wm) -
+          computedPadding;
+      cbSize.ISize(wm) =
+          aContainingBlockRI->mFrame->ISize(wm) - computedBorder.IStartEnd(wm);
+      NS_ASSERTION(cbSize.ISize(wm) >= 0, "Negative containing block isize!");
+      cbSize.BSize(wm) =
+          aContainingBlockRI->mFrame->BSize(wm) - computedBorder.BStartEnd(wm);
+      NS_ASSERTION(cbSize.BSize(wm) >= 0, "Negative containing block bsize!");
+    } else {
+      // If the ancestor is block-level, the containing block is formed by the
+      // padding edge of the ancestor
+      cbSize += computedPadding.Size(wm);
+    }
+  } else {
+    auto IsQuirky = [](const StyleSize& aSize) -> bool {
+      return aSize.ConvertsToPercentage();
+    };
+    // an element in quirks mode gets a containing block based on looking for a
+    // parent with a non-auto height if the element has a percent height.
+    // Note: We don't emulate this quirk for percents in calc(), or in vertical
+    // writing modes, or if the containing block is a flex or grid item.
+    if (!wm.IsVertical() && NS_UNCONSTRAINEDSIZE == cbSize.BSize(wm)) {
+      if (eCompatibility_NavQuirks == aPresContext->CompatibilityMode() &&
+          !aContainingBlockRI->mFrame->IsFlexOrGridItem() &&
+          (IsQuirky(mStylePosition->mHeight) ||
+           (mFrame->IsTableWrapperFrame() &&
+            IsQuirky(mFrame->PrincipalChildList()
+                         .FirstChild()
+                         ->StylePosition()
+                         ->mHeight)))) {
+        cbSize.BSize(wm) = CalcQuirkContainingBlockHeight(aContainingBlockRI);
+      }
+    }
+  }
+
+  return cbSize.ConvertTo(GetWritingMode(), wm);
+}
+
+// XXX refactor this code to have methods for each set of properties
+// we are computing: width,height,line-height; margin; offsets
+
+void ReflowInput::InitConstraints(
+    nsPresContext* aPresContext, const Maybe<LogicalSize>& aContainingBlockSize,
+    const Maybe<LogicalMargin>& aBorder, const Maybe<LogicalMargin>& aPadding,
+    LayoutFrameType aFrameType) {
+  WritingMode wm = GetWritingMode();
+  LogicalSize cbSize = aContainingBlockSize.valueOr(
+      LogicalSize(mWritingMode, NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE));
+  DISPLAY_INIT_CONSTRAINTS(mFrame, this, cbSize.ISize(wm), cbSize.BSize(wm),
+                           aBorder, aPadding);
+
+  // If this is a reflow root, then set the computed width and
+  // height equal to the available space
+  if (nullptr == mParentReflowInput || mFlags.mDummyParentReflowInput) {
+    // XXXldb This doesn't mean what it used to!
+    InitOffsets(wm, cbSize.ISize(wm), aFrameType, mComputeSizeFlags, aBorder,
+                aPadding, mStyleDisplay);
+    // Override mComputedMargin since reflow roots start from the
+    // frame's boundary, which is inside the margin.
+    SetComputedLogicalMargin(wm, LogicalMargin(wm));
+    SetComputedLogicalOffsets(wm, LogicalMargin(wm));
+
+    const auto borderPadding = ComputedLogicalBorderPadding(wm);
+    SetComputedISize(
+        std::max(0, AvailableISize() - borderPadding.IStartEnd(wm)),
+        ResetResizeFlags::No);
+    SetComputedBSize(
+        AvailableBSize() != NS_UNCONSTRAINEDSIZE
+            ? std::max(0, AvailableBSize() - borderPadding.BStartEnd(wm))
+            : NS_UNCONSTRAINEDSIZE,
+        ResetResizeFlags::No);
+
+    mComputedMinSize.SizeTo(mWritingMode, 0, 0);
+    mComputedMaxSize.SizeTo(mWritingMode, NS_UNCONSTRAINEDSIZE,
+                            NS_UNCONSTRAINEDSIZE);
+  } else {
+    // Get the containing block's reflow input
+    const ReflowInput* cbri = mCBReflowInput;
+    MOZ_ASSERT(cbri, "no containing block");
+    MOZ_ASSERT(mFrame->GetParent());
+
+    // If we weren't given a containing block size, then compute one.
+    if (aContainingBlockSize.isNothing()) {
+      cbSize = ComputeContainingBlockRectangle(aPresContext, cbri);
+    }
+
+    // See if the containing block height is based on the size of its
+    // content
+    if (NS_UNCONSTRAINEDSIZE == cbSize.BSize(wm)) {
+      // See if the containing block is a cell frame which needs
+      // to use the mComputedHeight of the cell instead of what the cell block
+      // passed in.
+      // XXX It seems like this could lead to bugs with min-height and friends
+      if (cbri->mParentReflowInput && cbri->mFrame->IsTableCellFrame()) {
+        cbSize.BSize(wm) = cbri->ComputedSize(wm).BSize(wm);
+      }
+    }
+
+    // XXX Might need to also pass the CB height (not width) for page boxes,
+    // too, if we implement them.
+
+    // For calculating positioning offsets, margins, borders and
+    // padding, we use the writing mode of the containing block
+    WritingMode cbwm = cbri->GetWritingMode();
+    InitOffsets(cbwm, cbSize.ConvertTo(cbwm, wm).ISize(cbwm), aFrameType,
+                mComputeSizeFlags, aBorder, aPadding, mStyleDisplay);
+
+    // For calculating the size of this box, we use its own writing mode
+    const auto& blockSize = mStylePosition->BSize(wm);
+    bool isAutoBSize = blockSize.BehavesLikeInitialValueOnBlockAxis();
+
+    // Check for a percentage based block size and a containing block
+    // block size that depends on the content block size
+    if (blockSize.HasPercent()) {
+      if (NS_UNCONSTRAINEDSIZE == cbSize.BSize(wm)) {
+        // this if clause enables %-blockSize on replaced inline frames,
+        // such as images.  See bug 54119.  The else clause "blockSizeUnit =
+        // eStyleUnit_Auto;" used to be called exclusively.
+        if (mFlags.mIsReplaced && mStyleDisplay->IsInlineOutsideStyle()) {
+          // Get the containing block's reflow input
+          NS_ASSERTION(nullptr != cbri, "no containing block");
+          // in quirks mode, get the cb height using the special quirk method
+          if (!wm.IsVertical() &&
+              eCompatibility_NavQuirks == aPresContext->CompatibilityMode()) {
+            if (!cbri->mFrame->IsTableCellFrame() &&
+                !cbri->mFrame->IsFlexOrGridItem()) {
+              cbSize.BSize(wm) = CalcQuirkContainingBlockHeight(cbri);
+              if (cbSize.BSize(wm) == NS_UNCONSTRAINEDSIZE) {
+                isAutoBSize = true;
+              }
+            } else {
+              isAutoBSize = true;
+            }
+          }
+          // in standard mode, use the cb block size.  if it's "auto",
+          // as will be the case by default in BODY, use auto block size
+          // as per CSS2 spec.
+          else {
+            nscoord computedBSize = cbri->ComputedSize(wm).BSize(wm);
+            if (NS_UNCONSTRAINEDSIZE != computedBSize) {
+              cbSize.BSize(wm) = computedBSize;
+            } else {
+              isAutoBSize = true;
+            }
+          }
+        } else {
+          // default to interpreting the blockSize like 'auto'
+          isAutoBSize = true;
+        }
+      }
+    }
+
+    // Compute our offsets if the element is relatively positioned.  We
+    // need the correct containing block inline-size and block-size
+    // here, which is why we need to do it after all the quirks-n-such
+    // above. (If the element is sticky positioned, we need to wait
+    // until the scroll container knows its size, so we compute offsets
+    // from StickyScrollContainer::UpdatePositions.)
+    if (mStyleDisplay->IsRelativelyPositioned(mFrame)) {
+      const LogicalMargin offsets =
+          ComputeRelativeOffsets(cbwm, mFrame, cbSize.ConvertTo(cbwm, wm));
+      SetComputedLogicalOffsets(cbwm, offsets);
+    } else {
+      // Initialize offsets to 0
+      SetComputedLogicalOffsets(wm, LogicalMargin(wm));
+    }
+
+    // Calculate the computed values for min and max properties.  Note that
+    // this MUST come after we've computed our border and padding.
+    ComputeMinMaxValues(cbSize);
+
+    // Calculate the computed inlineSize and blockSize.
+    // This varies by frame type.
+
+    if (IsInternalTableFrame()) {
+      // Internal table elements. The rules vary depending on the type.
+      // Calculate the computed isize
+      bool rowOrRowGroup = false;
+      const auto& inlineSize = mStylePosition->ISize(wm);
+      bool isAutoISize = inlineSize.IsAuto();
+      if ((StyleDisplay::TableRow == mStyleDisplay->mDisplay) ||
+          (StyleDisplay::TableRowGroup == mStyleDisplay->mDisplay)) {
+        // 'inlineSize' property doesn't apply to table rows and row groups
+        isAutoISize = true;
+        rowOrRowGroup = true;
+      }
+
+      // calc() with both percentages and lengths act like auto on internal
+      // table elements
+      if (isAutoISize || inlineSize.HasLengthAndPercentage()) {
+        if (AvailableISize() != NS_UNCONSTRAINEDSIZE && !rowOrRowGroup) {
+          // Internal table elements don't have margins. Only tables and
+          // cells have border and padding
+          SetComputedISize(
+              std::max(0, AvailableISize() -
+                              ComputedLogicalBorderPadding(wm).IStartEnd(wm)),
+              ResetResizeFlags::No);
+        } else {
+          SetComputedISize(AvailableISize(), ResetResizeFlags::No);
+        }
+        NS_ASSERTION(ComputedISize() >= 0, "Bogus computed isize");
+
+      } else {
+        SetComputedISize(
+            ComputeISizeValue(cbSize, mStylePosition->mBoxSizing, inlineSize),
+            ResetResizeFlags::No);
+      }
+
+      // Calculate the computed block size
+      if (StyleDisplay::TableColumn == mStyleDisplay->mDisplay ||
+          StyleDisplay::TableColumnGroup == mStyleDisplay->mDisplay) {
+        // 'blockSize' property doesn't apply to table columns and column groups
+        isAutoBSize = true;
+      }
+      // calc() with both percentages and lengths acts like 'auto' on internal
+      // table elements
+      if (isAutoBSize || blockSize.HasLengthAndPercentage()) {
+        SetComputedBSize(NS_UNCONSTRAINEDSIZE, ResetResizeFlags::No);
+      } else {
+        SetComputedBSize(
+            ComputeBSizeValue(cbSize.BSize(wm), mStylePosition->mBoxSizing,
+                              blockSize.AsLengthPercentage()),
+            ResetResizeFlags::No);
+      }
+
+      // Doesn't apply to internal table elements
+      mComputedMinSize.SizeTo(mWritingMode, 0, 0);
+      mComputedMaxSize.SizeTo(mWritingMode, NS_UNCONSTRAINEDSIZE,
+                              NS_UNCONSTRAINEDSIZE);
+    } else if (mFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW) &&
+               mStyleDisplay->IsAbsolutelyPositionedStyle() &&
+               // XXXfr hack for making frames behave properly when in overflow
+               // container lists, see bug 154892; need to revisit later
+               !mFrame->GetPrevInFlow()) {
+      InitAbsoluteConstraints(aPresContext, cbri,
+                              cbSize.ConvertTo(cbri->GetWritingMode(), wm),
+                              aFrameType);
+    } else {
+      AutoMaybeDisableFontInflation an(mFrame);
+
+      const bool isBlockLevel =
+          ((!mStyleDisplay->IsInlineOutsideStyle() &&
+            // internal table values on replaced elements behaves as inline
+            // https://drafts.csswg.org/css-tables-3/#table-structure
+            // "... it is handled instead as though the author had declared
+            //  either 'block' (for 'table' display) or 'inline' (for all
+            //  other values)"
+            !(mFlags.mIsReplaced && (mStyleDisplay->IsInnerTableStyle() ||
+                                     mStyleDisplay->DisplayOutside() ==
+                                         StyleDisplayOutside::TableCaption))) ||
+           // The inner table frame always fills its outer wrapper table frame,
+           // even for 'inline-table'.
+           mFrame->IsTableFrame()) &&
+          // XXX abs.pos. continuations treated like blocks, see comment in
+          // the else-if condition above.
+          (!mFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW) ||
+           mStyleDisplay->IsAbsolutelyPositionedStyle());
+
+      if (!isBlockLevel) {
+        mComputeSizeFlags += ComputeSizeFlag::ShrinkWrap;
+      }
+
+      nsIFrame* alignCB = mFrame->GetParent();
+      if (alignCB->IsTableWrapperFrame()) {
+        nsIFrame* alignCBParent = alignCB->GetParent();
+        if (alignCBParent && alignCBParent->IsGridContainerFrame()) {
+          alignCB = alignCBParent;
+        }
+      }
+      if (!alignCB->IsGridContainerFrame()) {
+        // Shrink-wrap blocks that are orthogonal to their container.
+        if (isBlockLevel && mCBReflowInput &&
+            mCBReflowInput->GetWritingMode().IsOrthogonalTo(mWritingMode)) {
+          mComputeSizeFlags += ComputeSizeFlag::ShrinkWrap;
+        }
+      }
+
+      if (cbSize.ISize(wm) == NS_UNCONSTRAINEDSIZE) {
+        // For orthogonal flows, where we found a parent orthogonal-limit
+        // for AvailableISize() in Init(), we'll use the same here as well.
+        cbSize.ISize(wm) = AvailableISize();
+      }
+
+      auto size =
+          mFrame->ComputeSize(mRenderingContext, wm, cbSize, AvailableISize(),
+                              ComputedLogicalMargin(wm).Size(wm),
+                              ComputedLogicalBorderPadding(wm).Size(wm),
+                              mStyleSizeOverrides, mComputeSizeFlags);
+
+      mComputedSize = size.mLogicalSize;
+      NS_ASSERTION(ComputedISize() >= 0, "Bogus inline-size");
+      NS_ASSERTION(
+          ComputedBSize() == NS_UNCONSTRAINEDSIZE || ComputedBSize() >= 0,
+          "Bogus block-size");
+
+      mFlags.mIsBSizeSetByAspectRatio =
+          size.mAspectRatioUsage == nsIFrame::AspectRatioUsage::ToComputeBSize;
+
+      const bool shouldCalculateBlockSideMargins = [&]() {
+        if (!isBlockLevel) {
+          return false;
+        }
+        if (mStyleDisplay->mDisplay == StyleDisplay::InlineTable) {
+          return false;
+        }
+        if (mFrame->IsTableFrame()) {
+          return false;
+        }
+        if (alignCB->IsFlexOrGridContainer()) {
+          // Exclude flex and grid items.
+          return false;
+        }
+        const auto pseudoType = mFrame->Style()->GetPseudoType();
+        if (pseudoType == PseudoStyleType::marker &&
+            mFrame->GetParent()->StyleList()->mListStylePosition ==
+                StyleListStylePosition::Outside) {
+          // Exclude outside ::markers.
+          return false;
+        }
+        if (pseudoType == PseudoStyleType::columnContent) {
+          // Exclude -moz-column-content since it cannot have any margin.
+          return false;
+        }
+        return true;
+      }();
+
+      if (shouldCalculateBlockSideMargins) {
+        CalculateBlockSideMargins();
+      }
+    }
+  }
+
+  // Save our containing block dimensions
+  mContainingBlockSize = cbSize;
+}
+
+static void UpdateProp(nsIFrame* aFrame,
+                       const FramePropertyDescriptor<nsMargin>* aProperty,
+                       bool aNeeded, const nsMargin& aNewValue) {
+  if (aNeeded) {
+    if (nsMargin* propValue = aFrame->GetProperty(aProperty)) {
+      *propValue = aNewValue;
+    } else {
+      aFrame->AddProperty(aProperty, new nsMargin(aNewValue));
+    }
+  } else {
+    aFrame->RemoveProperty(aProperty);
+  }
+}
+
+void SizeComputationInput::InitOffsets(WritingMode aCBWM, nscoord aPercentBasis,
+                                       LayoutFrameType aFrameType,
+                                       ComputeSizeFlags aFlags,
+                                       const Maybe<LogicalMargin>& aBorder,
+                                       const Maybe<LogicalMargin>& aPadding,
+                                       const nsStyleDisplay* aDisplay) {
+  DISPLAY_INIT_OFFSETS(mFrame, this, aPercentBasis, aCBWM, aBorder, aPadding);
+  nsPresContext* presContext = mFrame->PresContext();
+
+  // Compute margins from the specified margin style information. These
+  // become the default computed values, and may be adjusted below
+  // XXX fix to provide 0,0 for the top&bottom margins for
+  // inline-non-replaced elements
+  bool needMarginProp = ComputeMargin(aCBWM, aPercentBasis, aFrameType);
+  // Note that ComputeMargin() simplistically resolves 'auto' margins to 0.
+  // In formatting contexts where this isn't correct, some later code will
+  // need to update the UsedMargin() property with the actual resolved value.
+  // One example of this is ::CalculateBlockSideMargins().
+  ::UpdateProp(mFrame, nsIFrame::UsedMarginProperty(), needMarginProp,
+               ComputedPhysicalMargin());
+
+  const WritingMode wm = GetWritingMode();
+  const nsStyleDisplay* disp = mFrame->StyleDisplayWithOptionalParam(aDisplay);
+  bool needPaddingProp;
+  LayoutDeviceIntMargin widgetPadding;
+  if (mIsThemed && presContext->Theme()->GetWidgetPadding(
+                       presContext->DeviceContext(), mFrame,
+                       disp->EffectiveAppearance(), &widgetPadding)) {
+    const nsMargin padding = LayoutDevicePixel::ToAppUnits(
+        widgetPadding, presContext->AppUnitsPerDevPixel());
+    SetComputedLogicalPadding(wm, LogicalMargin(wm, padding));
+    needPaddingProp = false;
+  } else if (mFrame->IsInSVGTextSubtree()) {
+    SetComputedLogicalPadding(wm, LogicalMargin(wm));
+    needPaddingProp = false;
+  } else if (aPadding) {  // padding is an input arg
+    SetComputedLogicalPadding(wm, *aPadding);
+    nsMargin stylePadding;
+    // If the caller passes a padding that doesn't match our style (like
+    // nsTextControlFrame might due due to theming), then we also need a
+    // padding prop.
+    needPaddingProp = !mFrame->StylePadding()->GetPadding(stylePadding) ||
+                      aPadding->GetPhysicalMargin(wm) != stylePadding;
+  } else {
+    needPaddingProp = ComputePadding(aCBWM, aPercentBasis, aFrameType);
+  }
+
+  // Add [align|justify]-content:baseline padding contribution.
+  typedef const FramePropertyDescriptor<SmallValueHolder<nscoord>>* Prop;
+  auto ApplyBaselinePadding = [this, wm, &needPaddingProp](LogicalAxis aAxis,
+                                                           Prop aProp) {
+    bool found;
+    nscoord val = mFrame->GetProperty(aProp, &found);
+    if (found) {
+      NS_ASSERTION(val != nscoord(0), "zero in this property is useless");
+      LogicalSide side;
+      if (val > 0) {
+        side = MakeLogicalSide(aAxis, eLogicalEdgeStart);
+      } else {
+        side = MakeLogicalSide(aAxis, eLogicalEdgeEnd);
+        val = -val;
+      }
+      mComputedPadding.Side(side, wm) += val;
+      needPaddingProp = true;
+      if (aAxis == eLogicalAxisBlock && val > 0) {
+        // We have a baseline-adjusted block-axis start padding, so
+        // we need this to mark lines dirty when mIsBResize is true:
+        this->mFrame->AddStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE);
+      }
+    }
+  };
+  if (!aFlags.contains(ComputeSizeFlag::IsGridMeasuringReflow)) {
+    ApplyBaselinePadding(eLogicalAxisBlock, nsIFrame::BBaselinePadProperty());
+  }
+  if (!aFlags.contains(ComputeSizeFlag::ShrinkWrap)) {
+    ApplyBaselinePadding(eLogicalAxisInline, nsIFrame::IBaselinePadProperty());
+  }
+
+  LogicalMargin border(wm);
+  if (mIsThemed) {
+    const LayoutDeviceIntMargin widgetBorder =
+        presContext->Theme()->GetWidgetBorder(
+            presContext->DeviceContext(), mFrame, disp->EffectiveAppearance());
+    border = LogicalMargin(
+        wm, LayoutDevicePixel::ToAppUnits(widgetBorder,
+                                          presContext->AppUnitsPerDevPixel()));
+  } else if (mFrame->IsInSVGTextSubtree()) {
+    // Do nothing since the border local variable is initialized all zero.
+  } else if (aBorder) {  // border is an input arg
+    border = *aBorder;
+  } else {
+    border = LogicalMargin(wm, mFrame->StyleBorder()->GetComputedBorder());
+  }
+  SetComputedLogicalBorderPadding(wm, border + ComputedLogicalPadding(wm));
+
+  if (aFrameType == LayoutFrameType::Scrollbar) {
+    // scrollbars may have had their width or height smashed to zero
+    // by the associated scrollframe, in which case we must not report
+    // any padding or border.
+    nsSize size(mFrame->GetSize());
+    if (size.width == 0 || size.height == 0) {
+      SetComputedLogicalPadding(wm, LogicalMargin(wm));
+      SetComputedLogicalBorderPadding(wm, LogicalMargin(wm));
+    }
+  }
+
+  bool hasPaddingChange;
+  if (nsMargin* oldPadding =
+          mFrame->GetProperty(nsIFrame::UsedPaddingProperty())) {
+    // Note: If a padding change is already detectable without resolving the
+    // percentage, e.g. a padding is changing from 50px to 50%,
+    // nsIFrame::DidSetComputedStyle() will cache the old padding in
+    // UsedPaddingProperty().
+    hasPaddingChange = *oldPadding != ComputedPhysicalPadding();
+  } else {
+    // Our padding may have changed, but we can't tell at this point.
+    hasPaddingChange = needPaddingProp;
+  }
+  // Keep mHasPaddingChange bit set until we've done reflow. We'll clear it in
+  // nsIFrame::DidReflow()
+  mFrame->SetHasPaddingChange(mFrame->HasPaddingChange() || hasPaddingChange);
+
+  ::UpdateProp(mFrame, nsIFrame::UsedPaddingProperty(), needPaddingProp,
+               ComputedPhysicalPadding());
+}
+
+// This code enforces section 10.3.3 of the CSS2 spec for this formula:
+//
+// 'margin-left' + 'border-left-width' + 'padding-left' + 'width' +
+//   'padding-right' + 'border-right-width' + 'margin-right'
+//   = width of containing block
+//
+// Note: the width unit is not auto when this is called
+void ReflowInput::CalculateBlockSideMargins() {
+  MOZ_ASSERT(!mFrame->IsTableFrame(),
+             "Inner table frame cannot have computed margins!");
+
+  // Calculations here are done in the containing block's writing mode,
+  // which is where margins will eventually be applied: we're calculating
+  // margins that will be used by the container in its inline direction,
+  // which in the case of an orthogonal contained block will correspond to
+  // the block direction of this reflow input. So in the orthogonal-flow
+  // case, "CalculateBlock*Side*Margins" will actually end up adjusting
+  // the BStart/BEnd margins; those are the "sides" of the block from its
+  // container's point of view.
+  WritingMode cbWM =
+      mCBReflowInput ? mCBReflowInput->GetWritingMode() : GetWritingMode();
+
+  nscoord availISizeCBWM = AvailableSize(cbWM).ISize(cbWM);
+  nscoord computedISizeCBWM = ComputedSize(cbWM).ISize(cbWM);
+  if (computedISizeCBWM == NS_UNCONSTRAINEDSIZE) {
+    // For orthogonal flows, where we found a parent orthogonal-limit
+    // for AvailableISize() in Init(), we don't have meaningful sizes to
+    // adjust.  Act like the sum is already correct (below).
+    return;
+  }
+
+  LAYOUT_WARN_IF_FALSE(NS_UNCONSTRAINEDSIZE != computedISizeCBWM &&
+                           NS_UNCONSTRAINEDSIZE != availISizeCBWM,
+                       "have unconstrained inline-size; this should only "
+                       "result from very large sizes, not attempts at "
+                       "intrinsic inline-size calculation");
+
+  LogicalMargin margin = ComputedLogicalMargin(cbWM);
+  LogicalMargin borderPadding = ComputedLogicalBorderPadding(cbWM);
+  nscoord sum = margin.IStartEnd(cbWM) + borderPadding.IStartEnd(cbWM) +
+                computedISizeCBWM;
+  if (sum == availISizeCBWM) {
+    // The sum is already correct
+    return;
+  }
+
+  // Determine the start and end margin values. The isize value
+  // remains constant while we do this.
+
+  // Calculate how much space is available for margins
+  nscoord availMarginSpace = availISizeCBWM - sum;
+
+  // If the available margin space is negative, then don't follow the
+  // usual overconstraint rules.
+  if (availMarginSpace < 0) {
+    margin.IEnd(cbWM) += availMarginSpace;
+    SetComputedLogicalMargin(cbWM, margin);
+    return;
+  }
+
+  // The css2 spec clearly defines how block elements should behave
+  // in section 10.3.3.
+  const auto& styleSides = mStyleMargin->mMargin;
+  bool isAutoStartMargin = styleSides.GetIStart(cbWM).IsAuto();
+  bool isAutoEndMargin = styleSides.GetIEnd(cbWM).IsAuto();
+  if (!isAutoStartMargin && !isAutoEndMargin) {
+    // Neither margin is 'auto' so we're over constrained. Use the
+    // 'direction' property of the parent to tell which margin to
+    // ignore
+    // First check if there is an HTML alignment that we should honor
+    const StyleTextAlign* textAlign =
+        mParentReflowInput
+            ? &mParentReflowInput->mFrame->StyleText()->mTextAlign
+            : nullptr;
+    if (textAlign && (*textAlign == StyleTextAlign::MozLeft ||
+                      *textAlign == StyleTextAlign::MozCenter ||
+                      *textAlign == StyleTextAlign::MozRight)) {
+      if (mParentReflowInput->mWritingMode.IsBidiLTR()) {
+        isAutoStartMargin = *textAlign != StyleTextAlign::MozLeft;
+        isAutoEndMargin = *textAlign != StyleTextAlign::MozRight;
+      } else {
+        isAutoStartMargin = *textAlign != StyleTextAlign::MozRight;
+        isAutoEndMargin = *textAlign != StyleTextAlign::MozLeft;
+      }
+    }
+    // Otherwise apply the CSS rules, and ignore one margin by forcing
+    // it to 'auto', depending on 'direction'.
+    else {
+      isAutoEndMargin = true;
+    }
+  }
+
+  // Logic which is common to blocks and tables
+  // The computed margins need not be zero because the 'auto' could come from
+  // overconstraint or from HTML alignment so values need to be accumulated
+
+  if (isAutoStartMargin) {
+    if (isAutoEndMargin) {
+      // Both margins are 'auto' so the computed addition should be equal
+      nscoord forStart = availMarginSpace / 2;
+      margin.IStart(cbWM) += forStart;
+      margin.IEnd(cbWM) += availMarginSpace - forStart;
+    } else {
+      margin.IStart(cbWM) += availMarginSpace;
+    }
+  } else if (isAutoEndMargin) {
+    margin.IEnd(cbWM) += availMarginSpace;
+  }
+  SetComputedLogicalMargin(cbWM, margin);
+
+  if (isAutoStartMargin || isAutoEndMargin) {
+    // Update the UsedMargin property if we were tracking it already.
+    nsMargin* propValue = mFrame->GetProperty(nsIFrame::UsedMarginProperty());
+    if (propValue) {
+      *propValue = margin.GetPhysicalMargin(cbWM);
+    }
+  }
+}
+
+// For "normal" we use the font's normal line height (em height + leading).
+// If both internal leading and  external leading specified by font itself are
+// zeros, we should compensate this by creating extra (external) leading.
+// This is necessary because without this compensation, normal line height might
+// look too tight.
+constexpr float kNormalLineHeightFactor = 1.2f;
+static nscoord GetNormalLineHeight(nsFontMetrics* aFontMetrics) {
+  MOZ_ASSERT(aFontMetrics, "no font metrics");
+  nscoord externalLeading = aFontMetrics->ExternalLeading();
+  nscoord internalLeading = aFontMetrics->InternalLeading();
+  nscoord emHeight = aFontMetrics->EmHeight();
+  if (!internalLeading && !externalLeading) {
+    return NSToCoordRound(emHeight * kNormalLineHeightFactor);
+  }
+  return emHeight + internalLeading + externalLeading;
+}
+
+static inline nscoord ComputeLineHeight(const StyleLineHeight& aLh,
+                                        const nsStyleFont& aRelativeToFont,
+                                        nsPresContext* aPresContext,
+                                        bool aIsVertical, nscoord aBlockBSize,
+                                        float aFontSizeInflation) {
+  if (aLh.IsLength()) {
+    nscoord result = aLh.AsLength().ToAppUnits();
+    if (aFontSizeInflation != 1.0f) {
+      result = NSToCoordRound(result * aFontSizeInflation);
+    }
+    return result;
+  }
+
+  if (aLh.IsNumber()) {
+    // For factor units the computed value of the line-height property
+    // is found by multiplying the factor by the font's computed size
+    // (adjusted for min-size prefs and text zoom).
+    return aRelativeToFont.mFont.size
+        .ScaledBy(aLh.AsNumber() * aFontSizeInflation)
+        .ToAppUnits();
+  }
+
+  MOZ_ASSERT(aLh.IsNormal() || aLh.IsMozBlockHeight());
+  if (aLh.IsMozBlockHeight() && aBlockBSize != NS_UNCONSTRAINEDSIZE) {
+    return aBlockBSize;
+  }
+
+  auto size = aRelativeToFont.mFont.size;
+  size.ScaleBy(aFontSizeInflation);
+
+  if (aPresContext) {
+    RefPtr<nsFontMetrics> fm = nsLayoutUtils::GetMetricsFor(
+        aPresContext, aIsVertical, &aRelativeToFont, size,
+        /* aUseUserFontSet = */ true);
+    return GetNormalLineHeight(fm);
+  }
+  // If we don't have a pres context, use a 1.2em fallback.
+  size.ScaleBy(kNormalLineHeightFactor);
+  return size.ToAppUnits();
+}
+
+nscoord ReflowInput::GetLineHeight() const {
+  if (mLineHeight != NS_UNCONSTRAINEDSIZE) {
+    return mLineHeight;
+  }
+
+  nscoord blockBSize = nsLayoutUtils::IsNonWrapperBlock(mFrame)
+                           ? ComputedBSize()
+                           : (mCBReflowInput ? mCBReflowInput->ComputedBSize()
+                                             : NS_UNCONSTRAINEDSIZE);
+  mLineHeight = CalcLineHeight(*mFrame->Style(), mFrame->PresContext(),
+                               mFrame->GetContent(), blockBSize,
+                               nsLayoutUtils::FontSizeInflationFor(mFrame));
+  return mLineHeight;
+}
+
+void ReflowInput::SetLineHeight(nscoord aLineHeight) {
+  MOZ_ASSERT(aLineHeight >= 0, "aLineHeight must be >= 0!");
+
+  if (mLineHeight != aLineHeight) {
+    mLineHeight = aLineHeight;
+    // Setting used line height can change a frame's block-size if mFrame's
+    // block-size behaves as auto.
+    InitResizeFlags(mFrame->PresContext(), mFrame->Type());
+  }
+}
+
+/* static */
+nscoord ReflowInput::CalcLineHeight(const ComputedStyle& aStyle,
+                                    nsPresContext* aPresContext,
+                                    const nsIContent* aContent,
+                                    nscoord aBlockBSize,
+                                    float aFontSizeInflation) {
+  const StyleLineHeight& lh = aStyle.StyleFont()->mLineHeight;
+  WritingMode wm(&aStyle);
+  const bool vertical = wm.IsVertical() && !wm.IsSideways();
+  return CalcLineHeight(lh, *aStyle.StyleFont(), aPresContext, vertical,
+                        aContent, aBlockBSize, aFontSizeInflation);
+}
+
+nscoord ReflowInput::CalcLineHeight(
+    const StyleLineHeight& aLh, const nsStyleFont& aRelativeToFont,
+    nsPresContext* aPresContext, bool aIsVertical, const nsIContent* aContent,
+    nscoord aBlockBSize, float aFontSizeInflation) {
+  nscoord lineHeight =
+      ComputeLineHeight(aLh, aRelativeToFont, aPresContext, aIsVertical,
+                        aBlockBSize, aFontSizeInflation);
+
+  NS_ASSERTION(lineHeight >= 0, "ComputeLineHeight screwed up");
+
+  const auto* input = HTMLInputElement::FromNodeOrNull(aContent);
+  if (input && input->IsSingleLineTextControl()) {
+    // For Web-compatibility, single-line text input elements cannot
+    // have a line-height smaller than 'normal'.
+    if (!aLh.IsNormal()) {
+      nscoord normal = ComputeLineHeight(
+          StyleLineHeight::Normal(), aRelativeToFont, aPresContext, aIsVertical,
+          aBlockBSize, aFontSizeInflation);
+      if (lineHeight < normal) {
+        lineHeight = normal;
+      }
+    }
+  }
+
+  return lineHeight;
+}
+
+bool SizeComputationInput::ComputeMargin(WritingMode aCBWM,
+                                         nscoord aPercentBasis,
+                                         LayoutFrameType aFrameType) {
+  // SVG text frames have no margin.
+  if (mFrame->IsInSVGTextSubtree()) {
+    return false;
+  }
+
+  if (aFrameType == LayoutFrameType::Table) {
+    // Table frame's margin is inherited to the table wrapper frame via the
+    // ::-moz-table-wrapper rule in ua.css, so don't set any margins for it.
+    SetComputedLogicalMargin(mWritingMode, LogicalMargin(mWritingMode));
+    return false;
+  }
+
+  // If style style can provide us the margin directly, then use it.
+  const nsStyleMargin* styleMargin = mFrame->StyleMargin();
+
+  nsMargin margin;
+  const bool isCBDependent = !styleMargin->GetMargin(margin);
+  if (isCBDependent) {
+    // We have to compute the value. Note that this calculation is
+    // performed according to the writing mode of the containing block
+    // (http://dev.w3.org/csswg/css-writing-modes-3/#orthogonal-flows)
+    if (aPercentBasis == NS_UNCONSTRAINEDSIZE) {
+      aPercentBasis = 0;
+    }
+    LogicalMargin m(aCBWM);
+    m.IStart(aCBWM) = nsLayoutUtils::ComputeCBDependentValue(
+        aPercentBasis, styleMargin->mMargin.GetIStart(aCBWM));
+    m.IEnd(aCBWM) = nsLayoutUtils::ComputeCBDependentValue(
+        aPercentBasis, styleMargin->mMargin.GetIEnd(aCBWM));
+
+    m.BStart(aCBWM) = nsLayoutUtils::ComputeCBDependentValue(
+        aPercentBasis, styleMargin->mMargin.GetBStart(aCBWM));
+    m.BEnd(aCBWM) = nsLayoutUtils::ComputeCBDependentValue(
+        aPercentBasis, styleMargin->mMargin.GetBEnd(aCBWM));
+
+    SetComputedLogicalMargin(aCBWM, m);
+  } else {
+    SetComputedLogicalMargin(mWritingMode, LogicalMargin(mWritingMode, margin));
+  }
+
+  // ... but font-size-inflation-based margin adjustment uses the
+  // frame's writing mode
+  nscoord marginAdjustment = FontSizeInflationListMarginAdjustment(mFrame);
+
+  if (marginAdjustment > 0) {
+    LogicalMargin m = ComputedLogicalMargin(mWritingMode);
+    m.IStart(mWritingMode) += marginAdjustment;
+    SetComputedLogicalMargin(mWritingMode, m);
+  }
+
+  return isCBDependent;
+}
+
+bool SizeComputationInput::ComputePadding(WritingMode aCBWM,
+                                          nscoord aPercentBasis,
+                                          LayoutFrameType aFrameType) {
+  // If style can provide us the padding directly, then use it.
+  const nsStylePadding* stylePadding = mFrame->StylePadding();
+  nsMargin padding;
+  bool isCBDependent = !stylePadding->GetPadding(padding);
+  // a table row/col group, row/col doesn't have padding
+  // XXXldb Neither do border-collapse tables.
+  if (LayoutFrameType::TableRowGroup == aFrameType ||
+      LayoutFrameType::TableColGroup == aFrameType ||
+      LayoutFrameType::TableRow == aFrameType ||
+      LayoutFrameType::TableCol == aFrameType) {
+    SetComputedLogicalPadding(mWritingMode, LogicalMargin(mWritingMode));
+  } else if (isCBDependent) {
+    // We have to compute the value. This calculation is performed
+    // according to the writing mode of the containing block
+    // (http://dev.w3.org/csswg/css-writing-modes-3/#orthogonal-flows)
+    // clamp negative calc() results to 0
+    if (aPercentBasis == NS_UNCONSTRAINEDSIZE) {
+      aPercentBasis = 0;
+    }
+    LogicalMargin p(aCBWM);
+    p.IStart(aCBWM) = std::max(
+        0, nsLayoutUtils::ComputeCBDependentValue(
+               aPercentBasis, stylePadding->mPadding.GetIStart(aCBWM)));
+    p.IEnd(aCBWM) =
+        std::max(0, nsLayoutUtils::ComputeCBDependentValue(
+                        aPercentBasis, stylePadding->mPadding.GetIEnd(aCBWM)));
+
+    p.BStart(aCBWM) = std::max(
+        0, nsLayoutUtils::ComputeCBDependentValue(
+               aPercentBasis, stylePadding->mPadding.GetBStart(aCBWM)));
+    p.BEnd(aCBWM) =
+        std::max(0, nsLayoutUtils::ComputeCBDependentValue(
+                        aPercentBasis, stylePadding->mPadding.GetBEnd(aCBWM)));
+
+    SetComputedLogicalPadding(aCBWM, p);
+  } else {
+    SetComputedLogicalPadding(mWritingMode,
+                              LogicalMargin(mWritingMode, padding));
+  }
+  return isCBDependent;
+}
+
+void ReflowInput::ComputeMinMaxValues(const LogicalSize& aCBSize) {
+  WritingMode wm = GetWritingMode();
+
+  const auto& minISize = mStylePosition->MinISize(wm);
+  const auto& maxISize = mStylePosition->MaxISize(wm);
+  const auto& minBSize = mStylePosition->MinBSize(wm);
+  const auto& maxBSize = mStylePosition->MaxBSize(wm);
+
+  LogicalSize minWidgetSize(wm);
+  if (mIsThemed) {
+    nsPresContext* pc = mFrame->PresContext();
+    const LayoutDeviceIntSize widget = pc->Theme()->GetMinimumWidgetSize(
+        pc, mFrame, mStyleDisplay->EffectiveAppearance());
+
+    // Convert themed widget's physical dimensions to logical coords.
+    minWidgetSize = {
+        wm, LayoutDeviceIntSize::ToAppUnits(widget, pc->AppUnitsPerDevPixel())};
+
+    // GetMinimumWidgetSize() returns border-box; we need content-box.
+    minWidgetSize -= ComputedLogicalBorderPadding(wm).Size(wm);
+  }
+
+  // NOTE: min-width:auto resolves to 0, except on a flex item. (But
+  // even there, it's supposed to be ignored (i.e. treated as 0) until
+  // the flex container explicitly resolves & considers it.)
+  if (minISize.IsAuto()) {
+    SetComputedMinISize(0);
+  } else {
+    SetComputedMinISize(
+        ComputeISizeValue(aCBSize, mStylePosition->mBoxSizing, minISize));
+  }
+
+  if (mIsThemed) {
+    SetComputedMinISize(std::max(ComputedMinISize(), minWidgetSize.ISize(wm)));
+  }
+
+  if (maxISize.IsNone()) {
+    // Specified value of 'none'
+    SetComputedMaxISize(NS_UNCONSTRAINEDSIZE);
+  } else {
+    SetComputedMaxISize(
+        ComputeISizeValue(aCBSize, mStylePosition->mBoxSizing, maxISize));
+  }
+
+  // If the computed value of 'min-width' is greater than the value of
+  // 'max-width', 'max-width' is set to the value of 'min-width'
+  if (ComputedMinISize() > ComputedMaxISize()) {
+    SetComputedMaxISize(ComputedMinISize());
+  }
+
+  // Check for percentage based values and a containing block height that
+  // depends on the content height. Treat them like the initial value.
+  // Likewise, check for calc() with percentages on internal table elements;
+  // that's treated as the initial value too.
+  const bool isInternalTableFrame = IsInternalTableFrame();
+  const nscoord& bPercentageBasis = aCBSize.BSize(wm);
+  auto BSizeBehavesAsInitialValue = [&](const auto& aBSize) {
+    if (nsLayoutUtils::IsAutoBSize(aBSize, bPercentageBasis)) {
+      return true;
+    }
+    if (isInternalTableFrame) {
+      return aBSize.HasLengthAndPercentage();
+    }
+    return false;
+  };
+
+  // NOTE: min-height:auto resolves to 0, except on a flex item. (But
+  // even there, it's supposed to be ignored (i.e. treated as 0) until
+  // the flex container explicitly resolves & considers it.)
+  if (BSizeBehavesAsInitialValue(minBSize)) {
+    SetComputedMinBSize(0);
+  } else {
+    SetComputedMinBSize(ComputeBSizeValue(bPercentageBasis,
+                                          mStylePosition->mBoxSizing,
+                                          minBSize.AsLengthPercentage()));
+  }
+
+  if (mIsThemed) {
+    SetComputedMinBSize(std::max(ComputedMinBSize(), minWidgetSize.BSize(wm)));
+  }
+
+  if (BSizeBehavesAsInitialValue(maxBSize)) {
+    // Specified value of 'none'
+    SetComputedMaxBSize(NS_UNCONSTRAINEDSIZE);
+  } else {
+    SetComputedMaxBSize(ComputeBSizeValue(bPercentageBasis,
+                                          mStylePosition->mBoxSizing,
+                                          maxBSize.AsLengthPercentage()));
+  }
+
+  // If the computed value of 'min-height' is greater than the value of
+  // 'max-height', 'max-height' is set to the value of 'min-height'
+  if (ComputedMinBSize() > ComputedMaxBSize()) {
+    SetComputedMaxBSize(ComputedMinBSize());
+  }
+}
+
+bool ReflowInput::IsInternalTableFrame() const {
+  return mFrame->IsTableRowGroupFrame() || mFrame->IsTableColGroupFrame() ||
+         mFrame->IsTableRowFrame() || mFrame->IsTableCellFrame();
+}