author Brian Hackett <>
Wed, 14 Nov 2018 16:09:58 -1000
changeset 446931 1c7fc8389e012c987347efefca6b35f3948b742a
parent 446544 488a0a90ca916e094358cf9766a8aef648e711a5
child 448947 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1507359 Part 2 - Bindings and internal changes to allow ReplayDebugger to control child pausing/resuming, r=mccr8.

/* -*- 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 */

/* state used in reflow of block frames */

#include "BlockReflowInput.h"

#include <algorithm>
#include "LayoutLogging.h"
#include "nsBlockFrame.h"
#include "nsLineLayout.h"
#include "nsPresContext.h"
#include "nsIFrameInlines.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/Preferences.h"
#include "TextOverflow.h"

#ifdef DEBUG
#include "nsBlockDebugFlags.h"

using namespace mozilla;
using namespace mozilla::layout;

static bool sFloatFragmentsInsideColumnEnabled;
static bool sFloatFragmentsInsideColumnPrefCached;

BlockReflowInput::BlockReflowInput(const ReflowInput& aReflowInput,
                                       nsPresContext* aPresContext,
                                       nsBlockFrame* aFrame,
                                       bool aBStartMarginRoot,
                                       bool aBEndMarginRoot,
                                       bool aBlockNeedsFloatManager,
                                       nscoord aConsumedBSize)
  : mBlock(aFrame),
  if (!sFloatFragmentsInsideColumnPrefCached) {
    sFloatFragmentsInsideColumnPrefCached = true;
  mFlags.mFloatFragmentsInsideColumnEnabled = sFloatFragmentsInsideColumnEnabled;

  WritingMode wm = aReflowInput.GetWritingMode();
  mFlags.mIsFirstInflow = !aFrame->GetPrevInFlow();
  mFlags.mIsOverflowContainer = IS_TRUE_OVERFLOW_CONTAINER(aFrame);

  nsIFrame::LogicalSides logicalSkipSides =

  // Note that mContainerSize is the physical size, needed to
  // convert logical block-coordinates in vertical-rl writing mode
  // (measured from a RHS origin) to physical coordinates within the
  // containing block.
  // If aReflowInput doesn't have a constrained ComputedWidth(), we set
  // mContainerSize.width to zero, which means lines will be positioned
  // (physically) incorrectly; we will fix them up at the end of
  // nsBlockFrame::Reflow, after we know the total block-size of the
  // frame.
  mContainerSize.width = aReflowInput.ComputedWidth();
  if (mContainerSize.width == NS_UNCONSTRAINEDSIZE) {
    mContainerSize.width = 0;

  mContainerSize.width += mBorderPadding.LeftRight(wm);

  // For now at least, we don't do that fix-up for mContainerHeight.
  // It's only used in nsBidiUtils::ReorderFrames for vertical rtl
  // writing modes, which aren't fully supported for the time being.
  mContainerSize.height = aReflowInput.ComputedHeight() +

  if ((aBStartMarginRoot && !logicalSkipSides.BStart()) ||
      0 != mBorderPadding.BStart(wm)) {
    mFlags.mIsBStartMarginRoot = true;
    mFlags.mShouldApplyBStartMargin = true;
  if ((aBEndMarginRoot && !logicalSkipSides.BEnd()) ||
      0 != mBorderPadding.BEnd(wm)) {
    mFlags.mIsBEndMarginRoot = true;
  if (aBlockNeedsFloatManager) {
    mFlags.mBlockNeedsFloatManager = true;
  mFlags.mCanHaveTextOverflow = css::TextOverflow::CanHaveTextOverflow(mBlock);

             "Float manager should be valid when creating BlockReflowInput!");

  // Save the coordinate system origin for later.
  FloatManager()->GetTranslation(mFloatManagerI, mFloatManagerB);
  FloatManager()->PushState(&mFloatManagerStateBefore); // never popped

  mNextInFlow = static_cast<nsBlockFrame*>(mBlock->GetNextInFlow());

                       "have unconstrained width; this should only result "
                       "from very large sizes, not attempts at intrinsic "
                       "width calculation");
  mContentArea.ISize(wm) = aReflowInput.ComputedISize();

  // Compute content area height. Unlike the width, if we have a
  // specified style height we ignore it since extra content is
  // managed by the "overflow" property. When we don't have a
  // specified style height then we may end up limiting our height if
  // the availableHeight is constrained (this situation occurs when we
  // are paginated).
  if (NS_UNCONSTRAINEDSIZE != aReflowInput.AvailableBSize()) {
    // We are in a paginated situation. The bottom edge is just inside
    // the bottom border and padding. The content area height doesn't
    // include either border or padding edge.
    mBEndEdge = aReflowInput.AvailableBSize() - mBorderPadding.BEnd(wm);
    mContentArea.BSize(wm) = std::max(0, mBEndEdge - mBorderPadding.BStart(wm));
  else {
    // When we are not in a paginated situation then we always use
    // a constrained height.
    mFlags.mHasUnconstrainedBSize = true;
    mContentArea.BSize(wm) = mBEndEdge = NS_UNCONSTRAINEDSIZE;
  mContentArea.IStart(wm) = mBorderPadding.IStart(wm);
  mBCoord = mContentArea.BStart(wm) = mBorderPadding.BStart(wm);

  mPrevChild = nullptr;
  mCurrentLine = aFrame->LinesEnd();

  mMinLineHeight = aReflowInput.CalcLineHeight();

  if (mConsumedBSize == NS_INTRINSICSIZE) {
    mConsumedBSize = mBlock->ConsumedBSize(mReflowInput.GetWritingMode());

  return mConsumedBSize;

                      nsIFrame* aFrame,
                      const LogicalRect& aFloatAvailableSpace,
                      nscoord& aIStartResult,
                      nscoord& aIEndResult) const
  WritingMode wm = mReflowInput.GetWritingMode();
  // The frame is clueless about the float manager and therefore we
  // only give it free space. An example is a table frame - the
  // tables do not flow around floats.
  // However, we can let its margins intersect floats.
  NS_ASSERTION(aFloatAvailableSpace.IStart(wm) >= mContentArea.IStart(wm),
               "bad avail space rect inline-coord");
  NS_ASSERTION(aFloatAvailableSpace.ISize(wm) == 0 ||
               aFloatAvailableSpace.IEnd(wm) <= mContentArea.IEnd(wm),
               "bad avail space rect inline-size");

  nscoord iStartOffset, iEndOffset;
  if (aFloatAvailableSpace.ISize(wm) == mContentArea.ISize(wm)) {
    // We don't need to compute margins when there are no floats around.
    iStartOffset = 0;
    iEndOffset = 0;
  } else {
    LogicalMargin frameMargin(wm);
    SizeComputationInput os(aFrame, mReflowInput.mRenderingContext,
                        wm, mContentArea.ISize(wm));
    frameMargin =
      os.ComputedLogicalMargin().ConvertTo(wm, aFrame->GetWritingMode());

    nscoord iStartFloatIOffset =
      aFloatAvailableSpace.IStart(wm) - mContentArea.IStart(wm);
    iStartOffset = std::max(iStartFloatIOffset, frameMargin.IStart(wm)) -
    iStartOffset = std::max(iStartOffset, 0); // in case of negative margin
    nscoord iEndFloatIOffset =
      mContentArea.IEnd(wm) - aFloatAvailableSpace.IEnd(wm);
    iEndOffset = std::max(iEndFloatIOffset, frameMargin.IEnd(wm)) -
    iEndOffset = std::max(iEndOffset, 0); // in case of negative margin
  aIStartResult = iStartOffset;
  aIEndResult = iEndOffset;

static nscoord
GetBEndMarginClone(nsIFrame* aFrame,
                   gfxContext* aRenderingContext,
                   const LogicalRect& aContentArea,
                   WritingMode aWritingMode)
  if (aFrame->StyleBorder()->mBoxDecorationBreak ==
        StyleBoxDecorationBreak::Clone) {
    SizeComputationInput os(aFrame, aRenderingContext, aWritingMode,
    return os.ComputedLogicalMargin().
  return 0;

// Compute the amount of available space for reflowing a block frame
// at the current Y coordinate. This method assumes that
// GetAvailableSpace has already been called.
BlockReflowInput::ComputeBlockAvailSpace(nsIFrame* aFrame,
                                         const nsFlowAreaRect& aFloatAvailableSpace,
                                         bool aBlockAvoidsFloats,
                                         LogicalRect& aResult)
  printf("CBAS frame=%p has floats %d\n",
         aFrame, aFloatAvailableSpace.HasFloats());
  WritingMode wm = mReflowInput.GetWritingMode();
  aResult.BStart(wm) = mBCoord;
  aResult.BSize(wm) = mFlags.mHasUnconstrainedBSize
    : mReflowInput.AvailableBSize() - mBCoord
      - GetBEndMarginClone(aFrame, mReflowInput.mRenderingContext, mContentArea, wm);
  // mBCoord might be greater than mBEndEdge if the block's top margin pushes
  // it off the page/column. Negative available height can confuse other code
  // and is nonsense in principle.

  // XXX Do we really want this condition to be this restrictive (i.e.,
  // more restrictive than it used to be)?  The |else| here is allowed
  // by the CSS spec, but only out of desperation given implementations,
  // and the behavior it leads to is quite undesirable (it can cause
  // things to become extremely narrow when they'd fit quite well a
  // little bit lower).  Should the else be a quirk or something that
  // applies to a specific set of frame classes and no new ones?
  // If we did that, then for those frames where the condition below is
  // true but nsBlockFrame::BlockCanIntersectFloats is false,
  // nsBlockFrame::ISizeToClearPastFloats would need to use the
  // shrink-wrap formula, max(MIN_ISIZE, min(avail width, PREF_ISIZE))
  // rather than just using MIN_ISIZE.
  NS_ASSERTION(nsBlockFrame::BlockCanIntersectFloats(aFrame) ==
               "unexpected replaced width");
  if (!aBlockAvoidsFloats) {
    if (aFloatAvailableSpace.HasFloats()) {
      // Use the float-edge property to determine how the child block
      // will interact with the float.
      const nsStyleBorder* borderStyle = aFrame->StyleBorder();
      switch (borderStyle->mFloatEdge) {
        case StyleFloatEdge::ContentBox:  // content and only content does runaround of floats
          // The child block will flow around the float. Therefore
          // give it all of the available space.
          aResult.IStart(wm) = mContentArea.IStart(wm);
          aResult.ISize(wm) = mContentArea.ISize(wm);
        case StyleFloatEdge::MarginBox:
            // The child block's margins should be placed adjacent to,
            // but not overlap the float.
            aResult.IStart(wm) = aFloatAvailableSpace.mRect.IStart(wm);
            aResult.ISize(wm) = aFloatAvailableSpace.mRect.ISize(wm);
    else {
      // Since there are no floats present the float-edge property
      // doesn't matter therefore give the block element all of the
      // available space since it will flow around the float itself.
      aResult.IStart(wm) = mContentArea.IStart(wm);
      aResult.ISize(wm) = mContentArea.ISize(wm);
  else {
    nscoord iStartOffset, iEndOffset;
    ComputeReplacedBlockOffsetsForFloats(aFrame, aFloatAvailableSpace.mRect,
                                         iStartOffset, iEndOffset);
    aResult.IStart(wm) = mContentArea.IStart(wm) + iStartOffset;
    aResult.ISize(wm) = mContentArea.ISize(wm) - iStartOffset - iEndOffset;

  printf("  CBAS: result %d %d %d %d\n", aResult.IStart(wm), aResult.BStart(wm),
         aResult.ISize(wm), aResult.BSize(wm));

BlockReflowInput::ReplacedBlockFitsInAvailSpace(nsIFrame* aReplacedBlock,
                            const nsFlowAreaRect& aFloatAvailableSpace) const
  if (!aFloatAvailableSpace.HasFloats()) {
    // If there aren't any floats here, then we always fit.
    // We check this before calling ISizeToClearPastFloats, which is
    // somewhat expensive.
    return true;
  WritingMode wm = mReflowInput.GetWritingMode();
  nsBlockFrame::ReplacedElementISizeToClear replacedISize =
    nsBlockFrame::ISizeToClearPastFloats(*this, aFloatAvailableSpace.mRect,
  // The inline-start side of the replaced element should be offset by
  // the larger of the float intrusion or the replaced element's own
  // start margin.  The inline-end side is similar, except for Web
  // compatibility we ignore the margin.
  return std::max(aFloatAvailableSpace.mRect.IStart(wm) -
                  replacedISize.marginIStart) +
           replacedISize.borderBoxISize +
           (mContentArea.IEnd(wm) -
            aFloatAvailableSpace.mRect.IEnd(wm)) <=

                    nscoord aBCoord, ShapeType aShapeType,
                    nsFloatManager::SavedState* aState) const
  WritingMode wm = mReflowInput.GetWritingMode();
#ifdef DEBUG
  // Verify that the caller setup the coordinate system properly
  nscoord wI, wB;
  FloatManager()->GetTranslation(wI, wB);

  NS_ASSERTION((wI == mFloatManagerI) && (wB == mFloatManagerB),
               "bad coord system");

  nscoord blockSize = (mContentArea.BSize(wm) == nscoord_MAX)
    ? nscoord_MAX : std::max(mContentArea.BEnd(wm) - aBCoord, 0);
  nsFlowAreaRect result =
    FloatManager()->GetFlowArea(wm, aBCoord, blockSize,
                                BandInfoType::BandFromPoint, aShapeType,
                                mContentArea, aState, ContainerSize());
  // Keep the inline size >= 0 for compatibility with nsSpaceManager.
  if (result.mRect.ISize(wm) < 0) {
    result.mRect.ISize(wm) = 0;

#ifdef DEBUG
  if (nsBlockFrame::gNoisyReflow) {
    nsFrame::IndentBy(stdout, nsBlockFrame::gNoiseIndent);
    printf("%s: band=%d,%d,%d,%d hasfloats=%d\n", __func__,
           result.mRect.IStart(wm), result.mRect.BStart(wm),
           result.mRect.ISize(wm), result.mRect.BSize(wm), result.HasFloats());
  return result;

                      nscoord aBCoord, nscoord aBSize,
                      nsFloatManager::SavedState *aState) const
  WritingMode wm = mReflowInput.GetWritingMode();
#ifdef DEBUG
  // Verify that the caller setup the coordinate system properly
  nscoord wI, wB;
  FloatManager()->GetTranslation(wI, wB);

  NS_ASSERTION((wI == mFloatManagerI) && (wB == mFloatManagerB),
               "bad coord system");
  nsFlowAreaRect result =
    FloatManager()->GetFlowArea(wm, aBCoord, aBSize,
                                mContentArea, aState, ContainerSize());
  // Keep the width >= 0 for compatibility with nsSpaceManager.
  if (result.mRect.ISize(wm) < 0) {
    result.mRect.ISize(wm) = 0;

#ifdef DEBUG
  if (nsBlockFrame::gNoisyReflow) {
    nsFrame::IndentBy(stdout, nsBlockFrame::gNoiseIndent);
    printf("%s: space=%d,%d,%d,%d hasfloats=%d\n", __func__,
           result.mRect.IStart(wm), result.mRect.BStart(wm),
           result.mRect.ISize(wm), result.mRect.BSize(wm), result.HasFloats());
  return result;

 * Reconstruct the vertical margin before the line |aLine| in order to
 * do an incremental reflow that begins with |aLine| without reflowing
 * the line before it.  |aLine| may point to the fencepost at the end of
 * the line list, and it is used this way since we (for now, anyway)
 * always need to recover margins at the end of a block.
 * The reconstruction involves walking backward through the line list to
 * find any collapsed margins preceding the line that would have been in
 * the reflow state's |mPrevBEndMargin| when we reflowed that line in
 * a full reflow (under the rule in CSS2 that all adjacent vertical
 * margins of blocks collapse).
BlockReflowInput::ReconstructMarginBefore(nsLineList::iterator aLine)
  nsBlockFrame *block = mBlock;

  nsLineList::iterator firstLine = block->LinesBegin();
  for (;;) {
    if (aLine->IsBlock()) {
      mPrevBEndMargin = aLine->GetCarriedOutBEndMargin();
    if (!aLine->IsEmpty()) {
    if (aLine == firstLine) {
      // If the top margin was carried out (and thus already applied),
      // set it to zero.  Either way, we're done.
      if (!mFlags.mIsBStartMarginRoot) {

  MOZ_ASSERT(!mFlags.mIsFloatListInBlockPropertyTable == !mPushedFloats,
             "flag mismatch");
  if (!mFlags.mIsFloatListInBlockPropertyTable) {
    // If we're being re-Reflow'd without our next-in-flow having been
    // reflowed, some pushed floats from our previous reflow might
    // still be on our pushed floats list.  However, that's
    // actually fine, since they'll all end up being stolen and
    // reordered into the correct order again.
    // (nsBlockFrame::ReflowDirtyLines ensures that any lines with
    // pushed floats are reflowed.)
    mPushedFloats = mBlock->EnsurePushedFloats();
    mFlags.mIsFloatListInBlockPropertyTable = true;

BlockReflowInput::AppendPushedFloatChain(nsIFrame* aFloatCont)
  while (true) {
    mPushedFloats->AppendFrame(mBlock, aFloatCont);
    aFloatCont = aFloatCont->GetNextInFlow();
    if (!aFloatCont || aFloatCont->GetParent() != mBlock) {
    DebugOnly<nsresult> rv = mBlock->StealFrame(aFloatCont);
    NS_ASSERTION(NS_SUCCEEDED(rv), "StealFrame should succeed");

 * Restore information about floats into the float manager for an
 * incremental reflow, and simultaneously push the floats by
 * |aDeltaBCoord|, which is the amount |aLine| was pushed relative to its
 * parent.  The recovery of state is one of the things that makes
 * incremental reflow O(N^2) and this state should really be kept
 * around, attached to the frame tree.
BlockReflowInput::RecoverFloats(nsLineList::iterator aLine,
                                  nscoord aDeltaBCoord)
  WritingMode wm = mReflowInput.GetWritingMode();
  if (aLine->HasFloats()) {
    // Place the floats into the float manager again. Also slide
    // them, just like the regular frames on the line.
    nsFloatCache* fc = aLine->GetFirstFloat();
    while (fc) {
      nsIFrame* floatFrame = fc->mFloat;
      if (aDeltaBCoord != 0) {
        floatFrame->MovePositionBy(nsPoint(0, aDeltaBCoord));
#ifdef DEBUG
      if (nsBlockFrame::gNoisyReflow || nsBlockFrame::gNoisyFloatManager) {
        nscoord tI, tB;
        FloatManager()->GetTranslation(tI, tB);
        nsFrame::IndentBy(stdout, nsBlockFrame::gNoiseIndent);
        printf("RecoverFloats: tIB=%d,%d (%d,%d) ",
               tI, tB, mFloatManagerI, mFloatManagerB);
        nsFrame::ListTag(stdout, floatFrame);
        LogicalRect region = nsFloatManager::GetRegionFor(wm, floatFrame,
        printf(" aDeltaBCoord=%d region={%d,%d,%d,%d}\n",
               aDeltaBCoord, region.IStart(wm), region.BStart(wm),
               region.ISize(wm), region.BSize(wm));
                               nsFloatManager::GetRegionFor(wm, floatFrame,
                               wm, ContainerSize());
      fc = fc->Next();
  } else if (aLine->IsBlock()) {
    nsBlockFrame::RecoverFloatsFor(aLine->mFirstChild, *FloatManager(), wm,

 * Everything done in this function is done O(N) times for each pass of
 * reflow so it is O(N*M) where M is the number of incremental reflow
 * passes.  That's bad.  Don't do stuff here.
 * When this function is called, |aLine| has just been slid by |aDeltaBCoord|
 * and the purpose of RecoverStateFrom is to ensure that the
 * BlockReflowInput is in the same state that it would have been in
 * had the line just been reflowed.
 * Most of the state recovery that we have to do involves floats.
BlockReflowInput::RecoverStateFrom(nsLineList::iterator aLine,
                                     nscoord aDeltaBCoord)
  // Make the line being recovered the current line
  mCurrentLine = aLine;

  // Place floats for this line into the float manager
  if (aLine->HasFloats() || aLine->IsBlock()) {
    RecoverFloats(aLine, aDeltaBCoord);

#ifdef DEBUG
    if (nsBlockFrame::gNoisyReflow || nsBlockFrame::gNoisyFloatManager) {

// This is called by the line layout's AddFloat method when a
// place-holder frame is reflowed in a line. If the float is a
// left-most child (it's x coordinate is at the line's left margin)
// then the float is place immediately, otherwise the float
// placement is deferred until the line has been reflowed.

// XXXldb This behavior doesn't quite fit with CSS1 and CSS2 --
// technically we're supposed let the current line flow around the
// float as well unless it won't fit next to what we already have.
// But nobody else implements it that way...
BlockReflowInput::AddFloat(nsLineLayout*       aLineLayout,
                             nsIFrame*           aFloat,
                             nscoord             aAvailableISize)
  MOZ_ASSERT(aLineLayout, "must have line layout");
  MOZ_ASSERT(mBlock->LinesEnd() != mCurrentLine, "null ptr");
  MOZ_ASSERT(aFloat->GetStateBits() & NS_FRAME_OUT_OF_FLOW,
             "aFloat must be an out-of-flow frame");

  MOZ_ASSERT(aFloat->GetParent(), "float must have parent");
             "float's parent must be block");
  if (aFloat->HasAnyStateBits(NS_FRAME_IS_PUSHED_FLOAT) ||
      aFloat->GetParent() != mBlock) {
               "float should be in this block unless it was marked as "
               "pushed float, or just inserted");
    MOZ_ASSERT(aFloat->GetParent()->FirstContinuation() == mBlock->FirstContinuation());
    // If, in a previous reflow, the float was pushed entirely to
    // another column/page, we need to steal it back.  (We might just
    // push it again, though.)  Likewise, if that previous reflow
    // reflowed this block but not its next continuation, we might need
    // to steal it from our own float-continuations list.
    // For more about pushed floats, see the comment above
    // nsBlockFrame::DrainPushedFloats.
    auto* floatParent = static_cast<nsBlockFrame*>(aFloat->GetParent());


    // Appending is fine, since if a float was pushed to the next
    // page/column, all later floats were also pushed.
    mBlock->mFloats.AppendFrame(mBlock, aFloat);

  // Because we are in the middle of reflowing a placeholder frame
  // within a line (and possibly nested in an inline frame or two
  // that's a child of our block) we need to restore the space
  // manager's translation to the space that the block resides in
  // before placing the float.
  nscoord oI, oB;
  FloatManager()->GetTranslation(oI, oB);
  nscoord dI = oI - mFloatManagerI;
  nscoord dB = oB - mFloatManagerB;
  FloatManager()->Translate(-dI, -dB);

  bool placed;

  // Now place the float immediately if possible. Otherwise stash it
  // away in mBelowCurrentLineFloats and place it later.
  // If one or more floats has already been pushed to the next line,
  // don't let this one go on the current line, since that would violate
  // float ordering.
  LogicalRect floatAvailableSpace =
  if (mBelowCurrentLineFloats.IsEmpty() &&
      (aLineLayout->LineIsEmpty() ||
       mBlock->ComputeFloatISize(*this, floatAvailableSpace, aFloat)
       <= aAvailableISize)) {
    // And then place it
    placed = FlowAndPlaceFloat(aFloat);
    if (placed) {
      // Pass on updated available space to the current inline reflow engine
      WritingMode wm = mReflowInput.GetWritingMode();
      // If we have mLineBSize, we are reflowing the line again due to
      // LineReflowStatus::RedoMoreFloats. We should use mLineBSize to query the
      // correct available space.
      nsFlowAreaRect floatAvailSpace =
        ? GetFloatAvailableSpace(mBCoord)
        : GetFloatAvailableSpaceForBSize(mBCoord, mLineBSize.value(), nullptr);
      LogicalRect availSpace(wm, floatAvailSpace.mRect.IStart(wm), mBCoord,
      aLineLayout->UpdateBand(wm, availSpace, aFloat);
      // Record this float in the current-line list
    } else {
  else {
    // Always claim to be placed; we don't know whether we fit yet, so we
    // deal with this in PlaceBelowCurrentLineFloats
    placed = true;
    // This float will be placed after the line is done (it is a
    // below-current-line float).

  // Restore coordinate system
  FloatManager()->Translate(dI, dB);

  return placed;

BlockReflowInput::CanPlaceFloat(nscoord aFloatISize,
                                  const nsFlowAreaRect& aFloatAvailableSpace)
  // A float fits at a given block-dir position if there are no floats
  // at its inline-dir position (no matter what its inline size) or if
  // its inline size fits in the space remaining after prior floats have
  // been placed.
  // FIXME: We should allow overflow by up to half a pixel here (bug 21193).
  return !aFloatAvailableSpace.HasFloats() ||
    aFloatAvailableSpace.mRect.ISize(mReflowInput.GetWritingMode()) >=

// Return the inline-size that the float (including margins) will take up
// in the writing mode of the containing block. If this returns
// NS_UNCONSTRAINEDSIZE, we're dealing with an orthogonal block that
// has block-size:auto, and we'll need to actually reflow it to find out
// how much inline-size it will occupy in the containing block's mode.
static nscoord
FloatMarginISize(const ReflowInput& aCBReflowInput,
                 nscoord aFloatAvailableISize,
                 nsIFrame *aFloat,
                 const SizeComputationInput& aFloatOffsetState)
  AutoMaybeDisableFontInflation an(aFloat);
  WritingMode wm = aFloatOffsetState.GetWritingMode();

  LogicalSize floatSize =
              aFloatOffsetState.ComputedLogicalBorderPadding().Size(wm) -

  WritingMode cbwm = aCBReflowInput.GetWritingMode();
  nscoord floatISize = floatSize.ConvertTo(cbwm, wm).ISize(cbwm);
  if (floatISize == NS_UNCONSTRAINEDSIZE) {
    return NS_UNCONSTRAINEDSIZE; // reflow is needed to get the true size

  return floatISize +
           ConvertTo(cbwm, wm).ISize(cbwm) +
           ConvertTo(cbwm, wm).ISize(cbwm);

// A frame property that stores the last shape source / margin / etc. if there's
// any shape, in order to invalidate the float area properly when it changes.
// TODO(emilio): This could really belong to GetRegionFor / StoreRegionFor, but
// when I tried it was a bit awkward because of the logical -> physical
// conversion that happens there.
// Maybe all this code could be refactored to make this cleaner, but keeping the
// two properties separated was slightly nicer.
struct ShapeInvalidationData

  StyleShapeSource mShapeOutside;
  float mShapeImageThreshold = 0.0;
  nsStyleCoord mShapeMargin;

  ShapeInvalidationData() = default;

  explicit ShapeInvalidationData(const nsStyleDisplay& aDisplay)

  static bool IsNeeded(const nsStyleDisplay& aDisplay)
    return aDisplay.mShapeOutside.GetType() != StyleShapeSourceType::None;

  void Update(const nsStyleDisplay& aDisplay)
    mShapeOutside = aDisplay.mShapeOutside;
    mShapeImageThreshold = aDisplay.mShapeImageThreshold;
    mShapeMargin = aDisplay.mShapeMargin;

  bool Matches(const nsStyleDisplay& aDisplay) const
    return mShapeOutside == aDisplay.mShapeOutside &&
           mShapeImageThreshold == aDisplay.mShapeImageThreshold &&
           mShapeMargin == aDisplay.mShapeMargin;

NS_DECLARE_FRAME_PROPERTY_DELETABLE(ShapeInvalidationDataProperty, ShapeInvalidationData)

BlockReflowInput::FlowAndPlaceFloat(nsIFrame* aFloat)
  MOZ_ASSERT(aFloat->GetParent() == mBlock);

  WritingMode wm = mReflowInput.GetWritingMode();
  // Save away the Y coordinate before placing the float. We will
  // restore mBCoord at the end after placing the float. This is
  // necessary because any adjustments to mBCoord during the float
  // placement are for the float only, not for any non-floating
  // content.
  AutoRestore<nscoord> restoreBCoord(mBCoord);

  // Grab the float's display information
  const nsStyleDisplay* floatDisplay = aFloat->StyleDisplay();

  // The float's old region, so we can propagate damage.
  LogicalRect oldRegion = nsFloatManager::GetRegionFor(wm, aFloat,

  ShapeInvalidationData* invalidationData =

  // Enforce CSS2 9.5.1 rule [2], i.e., make sure that a float isn't
  // ``above'' another float that preceded it in the flow.
  mBCoord = std::max(FloatManager()->GetLowestFloatTop(), mBCoord);

  // See if the float should clear any preceding floats...
  // XXX We need to mark this float somehow so that it gets reflowed
  // when floats are inserted before it.
  if (StyleClear::None != floatDisplay->mBreakType) {
    // XXXldb Does this handle vertical margins correctly?
    mBCoord = ClearFloats(mBCoord, floatDisplay->mBreakType);
  // Get the band of available space with respect to margin box.
  nsFlowAreaRect floatAvailableSpace =
  LogicalRect adjustedAvailableSpace =
    mBlock->AdjustFloatAvailableSpace(*this, floatAvailableSpace.mRect, aFloat);

  NS_ASSERTION(aFloat->GetParent() == mBlock,
               "Float frame has wrong parent");

  SizeComputationInput offsets(aFloat, mReflowInput.mRenderingContext,
                           wm, mReflowInput.ComputedISize());

  nscoord floatMarginISize = FloatMarginISize(mReflowInput,
                                              aFloat, offsets);

  LogicalMargin floatMargin(wm); // computed margin
  LogicalMargin floatOffsets(wm);
  nsReflowStatus reflowStatus;

  // If it's a floating first-letter, we need to reflow it before we
  // know how wide it is (since we don't compute which letters are part
  // of the first letter until reflow!).
  // We also need to do this early reflow if FloatMarginISize returned
  // an unconstrained inline-size, which can occur if the float had an
  // orthogonal writing mode and 'auto' block-size (in its mode).
  bool earlyFloatReflow =
    aFloat->IsLetterFrame() || floatMarginISize == NS_UNCONSTRAINEDSIZE;
  if (earlyFloatReflow) {
    mBlock->ReflowFloat(*this, adjustedAvailableSpace, aFloat, floatMargin,
                        floatOffsets, false, reflowStatus);
    floatMarginISize = aFloat->ISize(wm) + floatMargin.IStartEnd(wm);
                 "letter frames and orthogonal floats with auto block-size "
                 "shouldn't break, and if they do now, then they're breaking "
                 "at the wrong point");

  // Find a place to place the float. The CSS2 spec doesn't want
  // floats overlapping each other or sticking out of the containing
  // block if possible (CSS2 spec section 9.5.1, see the rule list).
  StyleFloat floatStyle = floatDisplay->mFloat;
  MOZ_ASSERT(StyleFloat::Left == floatStyle || StyleFloat::Right == floatStyle,
             "Invalid float type!");

  // Can the float fit here?
  bool keepFloatOnSameLine = false;

  // Are we required to place at least part of the float because we're
  // at the top of the page (to avoid an infinite loop of pushing and
  // breaking).
  bool mustPlaceFloat =
    mReflowInput.mFlags.mIsTopOfPage && IsAdjacentWithTop();

  for (;;) {
    if (mReflowInput.AvailableHeight() != NS_UNCONSTRAINEDSIZE &&
        floatAvailableSpace.mRect.BSize(wm) <= 0 &&
        !mustPlaceFloat) {
      // No space, nowhere to put anything.
      return false;

    if (CanPlaceFloat(floatMarginISize, floatAvailableSpace)) {
      // We found an appropriate place.

    // Nope. try to advance to the next band.
    if (StyleDisplay::Table != floatDisplay->mDisplay ||
          eCompatibility_NavQuirks != mPresContext->CompatibilityMode() ) {

      mBCoord += floatAvailableSpace.mRect.BSize(wm);
      if (adjustedAvailableSpace.BSize(wm) != NS_UNCONSTRAINEDSIZE) {
        adjustedAvailableSpace.BSize(wm) -= floatAvailableSpace.mRect.BSize(wm);
      floatAvailableSpace = GetFloatAvailableSpaceForPlacingFloat(mBCoord);
    } else {
      // This quirk matches the one in nsBlockFrame::AdjustFloatAvailableSpace
      // IE handles float tables in a very special way

      // see if the previous float is also a table and has "align"
      nsFloatCache* fc = mCurrentLineFloats.Head();
      nsIFrame* prevFrame = nullptr;
      while (fc) {
        if (fc->mFloat == aFloat) {
        prevFrame = fc->mFloat;
        fc = fc->Next();

      if (prevFrame) {
        //get the frame type
        if (prevFrame->IsTableWrapperFrame()) {
          //see if it has "align="
          // IE makes a difference between align and the float property.
          // We're interested only if previous frame is align=left IE messes
          // things up when "right" (overlapping frames).
          // FIXME(emilio, bug 1426747): This looks fishy.
          nsIContent* content = prevFrame->GetContent();
          if (content &&
              content->IsElement() &&
                                                eIgnoreCase)) {
            keepFloatOnSameLine = true;
            // don't advance to next line (IE quirkie behaviour)
            // it breaks rule CSS2/9.5.1/1, but what the hell
            // since we cannot evangelize the world

      // the table does not fit anymore in this line so advance to next band
      mBCoord += floatAvailableSpace.mRect.BSize(wm);
      // To match nsBlockFrame::AdjustFloatAvailableSpace, we have to
      // get a new width for the new band.
      floatAvailableSpace = GetFloatAvailableSpaceForPlacingFloat(mBCoord);
      adjustedAvailableSpace = mBlock->AdjustFloatAvailableSpace(*this,
                                 floatAvailableSpace.mRect, aFloat);
      floatMarginISize = FloatMarginISize(mReflowInput,
                                          aFloat, offsets);

    mustPlaceFloat = false;

  // If the float is continued, it will get the same absolute x value as its prev-in-flow

  // We don't worry about the geometry of the prev in flow, let the continuation
  // place and size itself as required.

  // Assign inline and block dir coordinates to the float. We don't use
  // LineLeft() and LineRight() here, because we would only have to
  // convert the result back into this block's writing mode.
  LogicalPoint floatPos(wm);
  bool leftFloat = floatStyle == StyleFloat::Left;

  if (leftFloat == wm.IsBidiLTR()) {
    floatPos.I(wm) = floatAvailableSpace.mRect.IStart(wm);
  else {
    if (!keepFloatOnSameLine) {
      floatPos.I(wm) = floatAvailableSpace.mRect.IEnd(wm) - floatMarginISize;
    else {
      // this is the IE quirk (see few lines above)
      // the table is kept in the same line: don't let it overlap the
      // previous float
      floatPos.I(wm) = floatAvailableSpace.mRect.IStart(wm);
  // CSS2 spec, 9.5.1 rule [4]: "A floating box's outer top may not
  // be higher than the top of its containing block."  (Since the
  // containing block is the content edge of the block box, this
  // means the margin edge of the float can't be higher than the
  // content edge of the block that contains it.)
  floatPos.B(wm) = std::max(mBCoord, ContentBStart());

  // Reflow the float after computing its vertical position so it knows
  // where to break.
  if (!earlyFloatReflow) {
    bool pushedDown = mBCoord != restoreBCoord.SavedValue();
    mBlock->ReflowFloat(*this, adjustedAvailableSpace, aFloat, floatMargin,
                        floatOffsets, pushedDown, reflowStatus);
  if (aFloat->GetPrevInFlow())
    floatMargin.BStart(wm) = 0;
  if (reflowStatus.IsIncomplete())
    floatMargin.BEnd(wm) = 0;

  // In the case that we're in columns and not splitting floats, we need
  // to check here that the float's height fit, and if it didn't, bail.
  // (controlled by the pref "layout.float-fragments-inside-column.enabled")
  // Likewise, if none of the float fit, and it needs to be pushed in
  // its entirety to the next page (IsTruncated() or IsInlineBreakBefore()),
  // we need to do the same.
  if ((ContentBSize() != NS_UNCONSTRAINEDSIZE &&
       !mFlags.mFloatFragmentsInsideColumnEnabled &&
       adjustedAvailableSpace.BSize(wm) == NS_UNCONSTRAINEDSIZE &&
       !mustPlaceFloat &&
       aFloat->BSize(wm) + floatMargin.BStartEnd(wm) >
       ContentBEnd() - floatPos.B(wm)) ||
      reflowStatus.IsTruncated() ||
      reflowStatus.IsInlineBreakBefore()) {
    return false;

  // We can't use aFloat->ShouldAvoidBreakInside(mReflowInput) here since
  // its mIsTopOfPage may be true even though the float isn't at the
  // top when floatPos.B(wm) > 0.
  if (ContentBSize() != NS_UNCONSTRAINEDSIZE &&
      !mustPlaceFloat &&
      (!mReflowInput.mFlags.mIsTopOfPage || floatPos.B(wm) > 0) &&
      StyleBreakWithin::Avoid == aFloat->StyleDisplay()->mBreakInside &&
      (!reflowStatus.IsFullyComplete() ||
       aFloat->BSize(wm) + floatMargin.BStartEnd(wm) >
       ContentBEnd() - floatPos.B(wm)) &&
      !aFloat->GetPrevInFlow()) {
    return false;

  // Calculate the actual origin of the float frame's border rect
  // relative to the parent block; the margin must be added in
  // to get the border rect
  LogicalPoint origin(wm, floatMargin.IStart(wm) + floatPos.I(wm),
                      floatMargin.BStart(wm) + floatPos.B(wm));

  // If float is relatively positioned, factor that in as well
  ReflowInput::ApplyRelativePositioning(aFloat, wm, floatOffsets,
                                              &origin, ContainerSize());

  // Position the float and make sure and views are properly
  // positioned. We need to explicitly position its child views as
  // well, since we're moving the float after flowing it.
  bool moved = aFloat->GetLogicalPosition(wm, ContainerSize()) != origin;
  if (moved) {
    aFloat->SetPosition(wm, origin, ContainerSize());

  // Update the float combined area state
  // XXX Floats should really just get invalidated here if necessary
  mFloatOverflowAreas.UnionWith(aFloat->GetOverflowAreas() +

  // Place the float in the float manager
  // calculate region
  LogicalRect region =
    nsFloatManager::CalculateRegionFor(wm, aFloat, floatMargin,
  // if the float split, then take up all of the vertical height
  if (reflowStatus.IsIncomplete() &&
      (NS_UNCONSTRAINEDSIZE != ContentBSize())) {
    region.BSize(wm) = std::max(region.BSize(wm),
                                ContentBSize() - floatPos.B(wm));
  FloatManager()->AddFloat(aFloat, region, wm, ContainerSize());

  // store region
  nsFloatManager::StoreRegionFor(wm, aFloat, region, ContainerSize());

  const bool invalidationDataNeeded =

  // If the float's dimensions or shape have changed, note the damage in the
  // float manager.
  if (!region.IsEqualEdges(oldRegion) ||
      !!invalidationData != invalidationDataNeeded ||
      (invalidationData && !invalidationData->Matches(*floatDisplay))) {
    // XXXwaterson conservative: we could probably get away with noting
    // less damage; e.g., if only height has changed, then only note the
    // area into which the float has grown or from which the float has
    // shrunk.
    nscoord blockStart = std::min(region.BStart(wm), oldRegion.BStart(wm));
    nscoord blockEnd = std::max(region.BEnd(wm), oldRegion.BEnd(wm));
    FloatManager()->IncludeInDamage(blockStart, blockEnd);

  if (invalidationDataNeeded) {
    if (invalidationData) {
    } else {
                          new ShapeInvalidationData(*floatDisplay));
  } else if (invalidationData) {
    invalidationData = nullptr;

  if (!reflowStatus.IsFullyComplete()) {
    mBlock->SplitFloat(*this, aFloat, reflowStatus);
  } else {

#ifdef DEBUG
  if (nsBlockFrame::gNoisyFloatManager) {
    nscoord tI, tB;
    FloatManager()->GetTranslation(tI, tB);
    nsIFrame::ListTag(stdout, mBlock);
    printf(": FlowAndPlaceFloat: AddFloat: tIB=%d,%d (%d,%d) {%d,%d,%d,%d}\n",
           tI, tB, mFloatManagerI, mFloatManagerB,
           region.IStart(wm), region.BStart(wm),
           region.ISize(wm), region.BSize(wm));

  if (nsBlockFrame::gNoisyReflow) {
    nsRect r = aFloat->GetRect();
    nsFrame::IndentBy(stdout, nsBlockFrame::gNoiseIndent);
    printf("placed float: ");
    nsFrame::ListTag(stdout, aFloat);
    printf(" %d,%d,%d,%d\n", r.x, r.y, r.width, r.height);

  return true;

BlockReflowInput::PushFloatPastBreak(nsIFrame *aFloat)
  // This ensures that we:
  //  * don't try to place later but smaller floats (which CSS says
  //    must have their tops below the top of this float)
  //  * don't waste much time trying to reflow this float again until
  //    after the break
  StyleFloat floatStyle = aFloat->StyleDisplay()->mFloat;
  if (floatStyle == StyleFloat::Left) {
  } else {
    MOZ_ASSERT(floatStyle == StyleFloat::Right, "Unexpected float value!");

  // Put the float on the pushed floats list, even though it
  // isn't actually a continuation.
  DebugOnly<nsresult> rv = mBlock->StealFrame(aFloat);
  NS_ASSERTION(NS_SUCCEEDED(rv), "StealFrame should succeed");

 * Place below-current-line floats.
BlockReflowInput::PlaceBelowCurrentLineFloats(nsLineBox* aLine)
  nsFloatCache* fc = mBelowCurrentLineFloats.Head();
  while (fc) {
#ifdef DEBUG
    if (nsBlockFrame::gNoisyReflow) {
      nsFrame::IndentBy(stdout, nsBlockFrame::gNoiseIndent);
      printf("placing bcl float: ");
      nsFrame::ListTag(stdout, fc->mFloat);
    // Place the float
    bool placed = FlowAndPlaceFloat(fc->mFloat);
    nsFloatCache *next = fc->Next();
    if (!placed) {
      delete fc;
    fc = next;

BlockReflowInput::ClearFloats(nscoord aBCoord, StyleClear aBreakType,
                                nsIFrame *aReplacedBlock,
                                uint32_t aFlags)
#ifdef DEBUG
  if (nsBlockFrame::gNoisyReflow) {
    nsFrame::IndentBy(stdout, nsBlockFrame::gNoiseIndent);
    printf("clear floats: in: aBCoord=%d\n", aBCoord);

  printf("BlockReflowInput::ClearFloats: aBCoord=%d breakType=%s\n",
         aBCoord, nsLineBox::BreakTypeToString(aBreakType));

  if (!FloatManager()->HasAnyFloats()) {
    return aBCoord;

  nscoord newBCoord = aBCoord;

  if (aBreakType != StyleClear::None) {
    newBCoord = FloatManager()->ClearFloats(newBCoord, aBreakType, aFlags);

  if (aReplacedBlock) {
    for (;;) {
      nsFlowAreaRect floatAvailableSpace = GetFloatAvailableSpace(newBCoord);
      if (ReplacedBlockFitsInAvailSpace(aReplacedBlock, floatAvailableSpace)) {
      // See the analogous code for inlines in nsBlockFrame::DoReflowInlineFrames
      if (!AdvanceToNextBand(floatAvailableSpace.mRect, &newBCoord)) {
        // Stop trying to clear here; we'll just get pushed to the
        // next column or page and try again there.

#ifdef DEBUG
  if (nsBlockFrame::gNoisyReflow) {
    nsFrame::IndentBy(stdout, nsBlockFrame::gNoiseIndent);
    printf("clear floats: out: y=%d\n", newBCoord);

  return newBCoord;