Source code

Revision control

Other Tools

/* -*- 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 */
#ifndef BlockReflowInput_h
#define BlockReflowInput_h
#include <tuple>
#include "mozilla/ReflowInput.h"
#include "nsFloatManager.h"
#include "nsLineBox.h"
class nsBlockFrame;
class nsFrameList;
class nsOverflowContinuationTracker;
namespace mozilla {
// BlockReflowInput contains additional reflow input information that the
// block frame uses along with ReflowInput. Like ReflowInput, this
// is read-only data that is passed down from a parent frame to its children.
class BlockReflowInput {
using BandInfoType = nsFloatManager::BandInfoType;
using ShapeType = nsFloatManager::ShapeType;
// Block reflow input flags.
struct Flags {
: mIsBStartMarginRoot(false),
mCanHaveOverflowMarkers(false) {}
// Set in the BlockReflowInput constructor when reflowing a "block margin
// root" frame (i.e. a frame with the NS_BLOCK_MARGIN_ROOT flag set, for
// which margins apply by default).
// The flag is also set when reflowing a frame whose computed BStart border
// padding is non-zero.
bool mIsBStartMarginRoot : 1;
// Set in the BlockReflowInput constructor when reflowing a "block margin
// root" frame (i.e. a frame with the NS_BLOCK_MARGIN_ROOT flag set, for
// which margins apply by default).
// The flag is also set when reflowing a frame whose computed BEnd border
// padding is non-zero.
bool mIsBEndMarginRoot : 1;
// Set if the BStart margin should be considered when placing a linebox that
// contains a block frame. It may be set as a side-effect of calling
// nsBlockFrame::ShouldApplyBStartMargin(); once set,
// ShouldApplyBStartMargin() uses it as a fast-path way to return whether
// the BStart margin should apply.
// If the flag hasn't been set in the block reflow input, then
// ShouldApplyBStartMargin() will crawl the line list to see if a block
// frame precedes the specified frame. If so, the BStart margin should be
// applied, and the flag is set to cache the result. (If not, the BStart
// margin will be applied as a result of the generational margin collapsing
// logic in nsBlockReflowContext::ComputeCollapsedBStartMargin(). In this
// case, the flag won't be set, so subsequent calls to
// ShouldApplyBStartMargin() will continue crawl the line list.)
// This flag is also set in the BlockReflowInput constructor if
// mIsBStartMarginRoot is set; that is, the frame being reflowed is a margin
// root by default.
bool mShouldApplyBStartMargin : 1;
// Set when mLineAdjacentToTop is valid.
bool mHasLineAdjacentToTop : 1;
// Set when the block has the equivalent of NS_BLOCK_FLOAT_MGR.
bool mBlockNeedsFloatManager : 1;
// Set when nsLineLayout::LineIsEmpty was true at the end of reflowing
// the current line.
bool mIsLineLayoutEmpty : 1;
// Set when our mPushedFloats list is stored on the block's property table.
bool mIsFloatListInBlockPropertyTable : 1;
// Set when we need text-overflow or -webkit-line-clamp processing.
bool mCanHaveOverflowMarkers : 1;
BlockReflowInput(const ReflowInput& aReflowInput, nsPresContext* aPresContext,
nsBlockFrame* aFrame, bool aBStartMarginRoot,
bool aBEndMarginRoot, bool aBlockNeedsFloatManager,
nscoord aConsumedBSize = NS_UNCONSTRAINEDSIZE);
* Get the available reflow space (the area not occupied by floats)
* for the current y coordinate. The available space is relative to
* our coordinate system, which is the content box, with (0, 0) in the
* upper left.
* Returns whether there are floats present at the given block-direction
* coordinate and within the inline size of the content rect.
nsFlowAreaRect GetFloatAvailableSpace() const {
return GetFloatAvailableSpace(mBCoord);
nsFlowAreaRect GetFloatAvailableSpaceForPlacingFloat(nscoord aBCoord) const {
return GetFloatAvailableSpaceWithState(aBCoord, ShapeType::Margin, nullptr);
nsFlowAreaRect GetFloatAvailableSpace(nscoord aBCoord) const {
return GetFloatAvailableSpaceWithState(aBCoord, ShapeType::ShapeOutside,
nsFlowAreaRect GetFloatAvailableSpaceWithState(
nscoord aBCoord, ShapeType aShapeType,
nsFloatManager::SavedState* aState) const;
nsFlowAreaRect GetFloatAvailableSpaceForBSize(
nscoord aBCoord, nscoord aBSize,
nsFloatManager::SavedState* aState) const;
* The following functions all return true if they were able to
* place the float, false if the float did not fit in available
* space.
* aLineLayout is null when we are reflowing pushed floats (because
* they are not associated with a line box).
bool AddFloat(nsLineLayout* aLineLayout, nsIFrame* aFloat,
nscoord aAvailableISize);
bool FlowAndPlaceFloat(nsIFrame* aFloat);
void PlaceBelowCurrentLineFloats(nsLineBox* aLine);
// Returns the first coordinate >= aBCoord that clears the
// floats indicated by aBreakType and has enough inline size between floats
// (or no floats remaining) to accomodate aReplacedBlock.
enum class ClearFloatsResult : uint8_t {
std::tuple<nscoord, ClearFloatsResult> ClearFloats(
nscoord aBCoord, mozilla::StyleClear aBreakType,
nsIFrame* aReplacedBlock = nullptr);
nsFloatManager* FloatManager() const {
"Float manager should be valid during the lifetime of "
return mReflowInput.mFloatManager;
// Advances to the next band, i.e., the next horizontal stripe in
// which there is a different set of floats.
// Return false if it did not advance, which only happens for
// constrained heights (and means that we should get pushed to the
// next column/page).
bool AdvanceToNextBand(const mozilla::LogicalRect& aFloatAvailableSpace,
nscoord* aBCoord) const {
mozilla::WritingMode wm = mReflowInput.GetWritingMode();
if (aFloatAvailableSpace.BSize(wm) > 0) {
// See if there's room in the next band.
*aBCoord += aFloatAvailableSpace.BSize(wm);
} else {
if (mReflowInput.AvailableHeight() != NS_UNCONSTRAINEDSIZE) {
// Stop trying to clear here; we'll just get pushed to the
// next column or page and try again there.
return false;
MOZ_ASSERT_UNREACHABLE("avail space rect with zero height!");
*aBCoord += 1;
return true;
bool ReplacedBlockFitsInAvailSpace(
nsIFrame* aReplacedBlock,
const nsFlowAreaRect& aFloatAvailableSpace) const;
bool IsAdjacentWithTop() const {
return mBCoord == mBorderPadding.BStart(mReflowInput.GetWritingMode());
* Return mBlock's computed physical border+padding with GetSkipSides applied.
const mozilla::LogicalMargin& BorderPadding() const { return mBorderPadding; }
// Reconstruct the previous block-end margin that goes before |aLine|.
void ReconstructMarginBefore(nsLineList::iterator aLine);
// Caller must have called GetFloatAvailableSpace for the correct position
// (which need not be the current mBCoord).
void ComputeReplacedBlockOffsetsForFloats(
nsIFrame* aFrame, const mozilla::LogicalRect& aFloatAvailableSpace,
nscoord& aIStartResult, nscoord& aIEndResult) const;
// Caller must have called GetFloatAvailableSpace for the current mBCoord
void ComputeBlockAvailSpace(nsIFrame* aFrame,
const nsFlowAreaRect& aFloatAvailableSpace,
bool aBlockAvoidsFloats,
mozilla::LogicalRect& aResult);
void RecoverStateFrom(nsLineList::iterator aLine, nscoord aDeltaBCoord);
void AdvanceToNextLine() {
if (mFlags.mIsLineLayoutEmpty) {
mFlags.mIsLineLayoutEmpty = false;
} else {
// This state is the "global" state computed once for the reflow of
// the block.
// The block frame that is using this object
nsBlockFrame* mBlock;
nsPresContext* mPresContext;
const ReflowInput& mReflowInput;
// The coordinates within the float manager where the block is being
// placed <b>after</b> taking into account the blocks border and
// padding. This, therefore, represents the inner "content area" (in
// float manager coordinates) where child frames will be placed,
// including child blocks and floats.
nscoord mFloatManagerI, mFloatManagerB;
// XXX get rid of this
nsReflowStatus mReflowStatus;
// The float manager state as it was before the contents of this
// block. This is needed for positioning bullets, since we only want
// to move the bullet to flow around floats that were before this
// block, not floats inside of it.
nsFloatManager::SavedState mFloatManagerStateBefore;
// The content area to reflow child frames within. This is within
// this frame's coordinate system and writing mode, which means
// mContentArea.IStart == BorderPadding().IStart and
// mContentArea.BStart == BorderPadding().BStart.
// The block size may be NS_UNCONSTRAINEDSIZE, which indicates that there
// is no page/column boundary below (the common case).
// mContentArea.BEnd() should only be called after checking that
// mContentArea.BSize is not NS_UNCONSTRAINEDSIZE; otherwise
// coordinate overflow may occur.
mozilla::LogicalRect mContentArea;
nscoord ContentIStart() const {
return mContentArea.IStart(mReflowInput.GetWritingMode());
nscoord ContentISize() const {
return mContentArea.ISize(mReflowInput.GetWritingMode());
nscoord ContentIEnd() const {
return mContentArea.IEnd(mReflowInput.GetWritingMode());
nscoord ContentBStart() const {
return mContentArea.BStart(mReflowInput.GetWritingMode());
nscoord ContentBSize() const {
return mContentArea.BSize(mReflowInput.GetWritingMode());
nscoord ContentBEnd() const {
"ContentBSize() is unconstrained, so ContentBEnd() may overflow.");
return mContentArea.BEnd(mReflowInput.GetWritingMode());
mozilla::LogicalSize ContentSize(mozilla::WritingMode aWM) const {
mozilla::WritingMode wm = mReflowInput.GetWritingMode();
return mContentArea.Size(wm).ConvertTo(aWM, wm);
// Physical size. Use only for physical <-> logical coordinate conversion.
nsSize mContainerSize;
const nsSize& ContainerSize() const { return mContainerSize; }
// Continuation out-of-flow float frames that need to move to our
// next in flow are placed here during reflow. It's a pointer to
// a frame list stored in the block's property table.
nsFrameList* mPushedFloats;
// This method makes sure pushed floats are accessible to
// StealFrame. Call it before adding any frames to mPushedFloats.
void SetupPushedFloatList();
* Append aFloatCont and its next-in-flows within the same block to
* mPushedFloats. aFloatCont should not be on any child list when
* making this call. Its next-in-flows will be removed from
* mBlock using StealFrame() before being added to mPushedFloats.
* All appended frames will be marked NS_FRAME_IS_PUSHED_FLOAT.
void AppendPushedFloatChain(nsIFrame* aFloatCont);
// Track child overflow continuations.
nsOverflowContinuationTracker* mOverflowTracker;
// This state is "running" state updated by the reflow of each line
// in the block. This same state is "recovered" when a line is not
// dirty and is passed over during incremental reflow.
// The current line being reflowed
// If it is mBlock->end_lines(), then it is invalid.
nsLineList::iterator mCurrentLine;
// When mHasLineAdjacentToTop is set, this refers to a line
// which we know is adjacent to the top of the block (in other words,
// all lines before it are empty and do not have clearance. This line is
// always before the current line.
nsLineList::iterator mLineAdjacentToTop;
// The current block-direction coordinate in the block
nscoord mBCoord;
// mBlock's computed physical border+padding with GetSkipSides applied.
mozilla::LogicalMargin mBorderPadding;
// The overflow areas of all floats placed so far
mozilla::OverflowAreas mFloatOverflowAreas;
nsFloatCacheFreeList mFloatCacheFreeList;
// Previous child. This is used when pulling up a frame to update
// the sibling list.
nsIFrame* mPrevChild;
// The previous child frames collapsed bottom margin value.
nsCollapsingMargin mPrevBEndMargin;
// The current next-in-flow for the block. When lines are pulled
// from a next-in-flow, this is used to know which next-in-flow to
// pull from. When a next-in-flow is emptied of lines, we advance
// this to the next next-in-flow.
nsBlockFrame* mNextInFlow;
// Temporary state, for line-reflow. This state is used during the reflow
// of a given line, but doesn't have meaning before or after.
// The list of floats that are "current-line" floats. These are
// added to the line after the line has been reflowed, to keep the
// list fiddling from being N^2.
nsFloatCacheFreeList mCurrentLineFloats;
// The list of floats which are "below current-line"
// floats. These are reflowed/placed after the line is reflowed
// and placed. Again, this is done to keep the list fiddling from
// being N^2.
nsFloatCacheFreeList mBelowCurrentLineFloats;
// The list of floats that are waiting on a break opportunity in order to be
// placed, since we're on a nowrap context.
nsTArray<nsIFrame*> mNoWrapFloats;
nscoord mMinLineHeight;
int32_t mLineNumber;
Flags mFlags;
StyleClear mFloatBreakType;
// The amount of computed content block-size "consumed" by our previous
// continuations.
const nscoord mConsumedBSize;
// Cache the current line's BSize if nsBlockFrame::PlaceLine() fails to
// place the line. When redoing the line, it will be used to query the
// accurate float available space in AddFloat() and
// nsBlockFrame::PlaceLine().
mozilla::Maybe<nscoord> mLineBSize;
bool CanPlaceFloat(nscoord aFloatISize,
const nsFlowAreaRect& aFloatAvailableSpace);
void PushFloatPastBreak(nsIFrame* aFloat);
void RecoverFloats(nsLineList::iterator aLine, nscoord aDeltaBCoord);
}; // namespace mozilla
#endif // BlockReflowInput_h