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/* -*- 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 and methods used while laying out a single line of a block frame */
#ifndef nsLineLayout_h___
#define nsLineLayout_h___
#include "gfxTypes.h"
#include "gfxTextRun.h"
#include "JustificationUtils.h"
#include "mozilla/ArenaAllocator.h"
#include "mozilla/WritingModes.h"
#include "BlockReflowState.h"
#include "nsLineBox.h"
class nsFloatManager;
struct nsStyleText;
class nsLineLayout {
using BlockReflowState = mozilla::BlockReflowState;
using ReflowInput = mozilla::ReflowInput;
using ReflowOutput = mozilla::ReflowOutput;
* @param aBaseLineLayout the nsLineLayout for ruby base,
* nullptr if no separate base nsLineLayout is needed.
nsLineLayout(nsPresContext* aPresContext, nsFloatManager* aFloatManager,
const ReflowInput& aLineContainerRI,
const nsLineList::iterator* aLine,
nsLineLayout* aBaseLineLayout);
void Init(BlockReflowState* aState, nscoord aMinLineBSize,
int32_t aLineNumber) {
mBlockRS = aState;
mMinLineBSize = aMinLineBSize;
mLineNumber = aLineNumber;
int32_t GetLineNumber() const { return mLineNumber; }
void BeginLineReflow(nscoord aICoord, nscoord aBCoord, nscoord aISize,
nscoord aBSize, bool aImpactedByFloats,
bool aIsTopOfPage, mozilla::WritingMode aWritingMode,
const nsSize& aContainerSize,
// aInset is used during text-wrap:balance to reduce
// the effective available space on the line.
nscoord aInset = 0);
* Returns true if the line had to use an overflow-wrap break position.
bool EndLineReflow();
* Called when a float has been placed. This method updates the
* inline frame and span data to account for any change in positions
* due to available space for the line boxes changing.
* @param aX/aY/aWidth/aHeight are the new available
* space rectangle, relative to the containing block.
* @param aFloatFrame the float frame that was placed.
void UpdateBand(mozilla::WritingMode aWM,
const mozilla::LogicalRect& aNewAvailableSpace,
nsIFrame* aFloatFrame);
void BeginSpan(nsIFrame* aFrame, const ReflowInput* aSpanReflowInput,
nscoord aLeftEdge, nscoord aRightEdge, nscoord* aBaseline);
// Returns the width of the span
nscoord EndSpan(nsIFrame* aFrame);
// This method attaches the last frame reflowed in this line layout
// to that in the base line layout.
void AttachLastFrameToBaseLineLayout() {
// This method attaches the root frame of this line layout to the
// last reflowed frame in the base line layout.
void AttachRootFrameToBaseLineLayout() {
int32_t GetCurrentSpanCount() const;
void SplitLineTo(int32_t aNewCount);
bool IsZeroBSize();
// Reflows the frame and returns the reflow status. aPushedFrame is true
// if the frame is pushed to the next line because it doesn't fit.
void ReflowFrame(nsIFrame* aFrame, nsReflowStatus& aReflowStatus,
ReflowOutput* aMetrics, bool& aPushedFrame);
void AddMarkerFrame(nsIFrame* aFrame, const ReflowOutput& aMetrics);
void RemoveMarkerFrame(nsIFrame* aFrame);
* Place frames in the block direction (CSS property vertical-align)
void VerticalAlignLine();
bool TrimTrailingWhiteSpace();
* Place frames in the inline direction (CSS property text-align).
void TextAlignLine(nsLineBox* aLine, bool aIsLastLine);
* Handle all the relative positioning in the line, compute the
* combined area (== overflow area) for the line, and handle view
* sizing/positioning and the setting of the overflow rect.
void RelativePositionFrames(mozilla::OverflowAreas& aOverflowAreas) {
RelativePositionFrames(mRootSpan, aOverflowAreas);
// Support methods for word-wrapping during line reflow
void SetJustificationInfo(const mozilla::JustificationInfo& aInfo) {
mJustificationInfo = aInfo;
* @return true if so far during reflow no non-empty content has been
* placed in the line (according to nsIFrame::IsEmpty())
bool LineIsEmpty() const { return mLineIsEmpty; }
* @return true if so far during reflow no non-empty leaf content
* (non-collapsed whitespace, replaced element, inline-block, etc) has been
* placed in the line
bool LineAtStart() const { return mLineAtStart; }
bool LineIsBreakable() const;
bool GetLineEndsInBR() const { return mLineEndsInBR; }
void SetLineEndsInBR(bool aOn) { mLineEndsInBR = aOn; }
// Inform the line-layout about the presence of a floating frame
// XXX get rid of this: use get-frame-type?
bool AddFloat(nsIFrame* aFloat, nscoord aAvailableISize) {
// When reflowing ruby text frames, no block reflow state is
// provided to the line layout. However, floats should never be
// associated with ruby text containers, hence this method should
// not be called in that case.
"Should not call this method if there is no block reflow state "
return mBlockRS->AddFloat(this, aFloat, aAvailableISize);
void SetTrimmableISize(nscoord aTrimmableISize) {
mTrimmableISize = aTrimmableISize;
bool GetFirstLetterStyleOK() const { return mFirstLetterStyleOK; }
void SetFirstLetterStyleOK(bool aSetting) { mFirstLetterStyleOK = aSetting; }
bool GetInFirstLetter() const { return mInFirstLetter; }
void SetInFirstLetter(bool aSetting) { mInFirstLetter = aSetting; }
bool GetInFirstLine() const { return mInFirstLine; }
void SetInFirstLine(bool aSetting) { mInFirstLine = aSetting; }
// Calling this during block reflow ensures that the next line of inlines
// will be marked dirty, if there is one.
void SetDirtyNextLine() { mDirtyNextLine = true; }
bool GetDirtyNextLine() { return mDirtyNextLine; }
nsPresContext* mPresContext;
* Record where an optional break could have been placed. During line reflow,
* frames containing optional break points (e.g., whitespace in text frames)
* can call SetLastOptionalBreakPosition to record where a break could
* have been made, but wasn't because we decided to place more content on
* the line. For non-text frames, offset 0 means before the frame, offset
* INT32_MAX means after the frame.
* Currently this is used to handle cases where a single word comprises
* multiple frames, and the first frame fits on the line but the whole word
* doesn't. We look back to the last optional break position and
* reflow the whole line again, forcing a break at that position. The last
* optional break position could be in a text frame or else after a frame
* that cannot be part of a text run, so those are the positions we record.
* @param aFrame the frame which contains the optional break position.
* @param aFits set to true if the break position is within the available
* width.
* @param aPriority the priority of the break opportunity. If we are
* prioritizing break opportunities, we will not set a break if we have
* already set a break with a higher priority. @see gfxBreakPriority.
* @return true if we are actually reflowing with forced break position and we
* should break here
bool NotifyOptionalBreakPosition(nsIFrame* aFrame, int32_t aOffset,
bool aFits, gfxBreakPriority aPriority);
// Tries to place a float, and records whether the float actually was placed.
bool TryToPlaceFloat(nsIFrame* aFloat);
// Records a floating frame in a nowrap context for it to be placed on the
// next break opportunity.
void RecordNoWrapFloat(nsIFrame* aFloat);
// Tries to place the floats from the nowrap context.
void FlushNoWrapFloats();
* Like NotifyOptionalBreakPosition, but here it's OK for mNeedBackup
* to be set, because the caller is merely pruning some saved break
* position(s) that are actually not feasible.
void RestoreSavedBreakPosition(nsIFrame* aFrame, int32_t aOffset,
gfxBreakPriority aPriority) {
mLastOptionalBreakFrame = aFrame;
mLastOptionalBreakFrameOffset = aOffset;
mLastOptionalBreakPriority = aPriority;
* Signal that no backing up will be required after all.
void ClearOptionalBreakPosition() {
mNeedBackup = false;
mLastOptionalBreakFrame = nullptr;
mLastOptionalBreakFrameOffset = -1;
mLastOptionalBreakPriority = gfxBreakPriority::eNoBreak;
// Retrieve last set optional break position. When this returns null, no
// optional break has been recorded (which means that the line can't break
// yet).
nsIFrame* GetLastOptionalBreakPosition(int32_t* aOffset,
gfxBreakPriority* aPriority) {
*aOffset = mLastOptionalBreakFrameOffset;
*aPriority = mLastOptionalBreakPriority;
return mLastOptionalBreakFrame;
// Whether any optional break position has been recorded.
bool HasOptionalBreakPosition() const {
return mLastOptionalBreakFrame != nullptr;
// Get the priority of the last optional break position recorded.
gfxBreakPriority LastOptionalBreakPriority() const {
return mLastOptionalBreakPriority;
* Check whether frames overflowed the available width and CanPlaceFrame
* requested backing up to a saved break position.
bool NeedsBackup() { return mNeedBackup; }
// Line layout may place too much content on a line, overflowing its available
// width. When that happens, if SetLastOptionalBreakPosition has been
// used to record an optional break that wasn't taken, we can reflow the line
// again and force the break to happen at that point (i.e., backtracking
// to the last choice point).
// Record that we want to break at the given content+offset (which
// should have been previously returned by GetLastOptionalBreakPosition
// from another nsLineLayout).
void ForceBreakAtPosition(nsIFrame* aFrame, int32_t aOffset) {
mForceBreakFrame = aFrame;
mForceBreakFrameOffset = aOffset;
bool HaveForcedBreakPosition() { return mForceBreakFrame != nullptr; }
int32_t GetForcedBreakPosition(nsIFrame* aFrame) {
return mForceBreakFrame == aFrame ? mForceBreakFrameOffset : -1;
* This can't be null. It usually returns a block frame but may return
* some other kind of frame when inline frames are reflowed in a non-block
* context (e.g. MathML or floating first-letter).
nsIFrame* LineContainerFrame() const { return mLineContainerRI.mFrame; }
const ReflowInput& LineContainerRI() const { return mLineContainerRI; }
const nsLineList::iterator* GetLine() const {
return mGotLineBox ? &mLineBox : nullptr;
nsLineList::iterator* GetLine() { return mGotLineBox ? &mLineBox : nullptr; }
* Returns the accumulated advance width of frames before the current frame
* on the line, plus the line container's left border+padding.
* This is always positive, the advance width is measured from
* the right edge for RTL blocks and from the left edge for LTR blocks.
* In other words, the current frame's distance from the line container's
* start content edge is:
* <code>GetCurrentFrameInlineDistanceFromBlock() -
* lineContainer->GetUsedBorderAndPadding().left</code> Note the use of
* <code>.left</code> for both LTR and RTL line containers.
nscoord GetCurrentFrameInlineDistanceFromBlock();
* Move the inline position where the next frame will be reflowed forward by
* aAmount.
void AdvanceICoord(nscoord aAmount) { mCurrentSpan->mICoord += aAmount; }
* Returns the writing mode for the root span.
mozilla::WritingMode GetWritingMode() { return mRootSpan->mWritingMode; }
* Returns the inline position where the next frame will be reflowed.
nscoord GetCurrentICoord() { return mCurrentSpan->mICoord; }
void SetSuppressLineWrap(bool aEnabled) { mSuppressLineWrap = aEnabled; }
* Record that the line had to resort to an overflow-wrap break.
void SetUsedOverflowWrap() { mUsedOverflowWrap = true; }
// This state is constant for a given block frame doing line layout
// A non-owning pointer, which points to the object owned by
// nsAutoFloatManager::mNew.
nsFloatManager* mFloatManager;
const nsStyleText* mStyleText; // for the block
const ReflowInput& mLineContainerRI;
// The line layout for the base text. It is usually nullptr.
// It becomes not null when the current line layout is for ruby
// annotations. When there is nested ruby inside annotation, it
// forms a linked list from the inner annotation to the outermost
// line layout. The outermost line layout, which has this member
// being nullptr, is responsible for managing the life cycle of
// per-frame data and per-span data, and handling floats.
nsLineLayout* const mBaseLineLayout;
nsLineLayout* GetOutermostLineLayout() {
nsLineLayout* lineLayout = this;
while (lineLayout->mBaseLineLayout) {
lineLayout = lineLayout->mBaseLineLayout;
return lineLayout;
nsIFrame* mLastOptionalBreakFrame;
nsIFrame* mForceBreakFrame;
// XXX remove this when landing bug 154892 (splitting absolute positioned
// frames)
friend class nsInlineFrame;
// XXX Take care that nsRubyBaseContainer would give nullptr to this
// member. It should not be a problem currently, since the only
// code use it is handling float, which does not affect ruby.
// See comment in nsLineLayout::AddFloat
BlockReflowState* mBlockRS = nullptr; /* XXX hack! */
nsLineList::iterator mLineBox;
// Per-frame data recorded by the line-layout reflow logic. This
// state is the state needed to post-process the line after reflow
// has completed (block-direction alignment, inline-direction alignment,
// justification and relative positioning).
struct PerSpanData;
struct PerFrameData;
friend struct PerSpanData;
friend struct PerFrameData;
struct PerFrameData {
// link to next/prev frame in same span
PerFrameData* mNext;
PerFrameData* mPrev;
// Link to the frame of next ruby annotation. It is a linked list
// through this pointer from ruby base to all its annotations. It
// could be nullptr if there is no more annotation.
// If PFD_ISLINKEDTOBASE is set, the current PFD is one of the ruby
// annotations in the base's list, otherwise it is the ruby base,
// and its mNextAnnotation is the start of the linked list.
PerFrameData* mNextAnnotation;
// pointer to child span data if this is an inline container frame
PerSpanData* mSpan;
// The frame
nsIFrame* mFrame;
// From metrics
nscoord mAscent;
// note that mBounds is a logical rect in the *line*'s writing mode.
// When setting frame coordinates, we have to convert to the frame's
// writing mode
mozilla::LogicalRect mBounds;
mozilla::OverflowAreas mOverflowAreas;
// From reflow-state
mozilla::LogicalMargin mMargin; // in *line* writing mode
mozilla::LogicalMargin mBorderPadding; // in *line* writing mode
mozilla::LogicalMargin mOffsets; // in *frame* writing mode
// state for text justification
// Note that, although all frames would have correct inner
// opportunities computed after ComputeFrameJustification, start
// and end justifiable info are not reliable for non-text frames.
mozilla::JustificationInfo mJustificationInfo;
mozilla::JustificationAssignment mJustificationAssignment;
// PerFrameData flags
bool mIsRelativelyOrStickyPos : 1;
bool mIsTextFrame : 1;
bool mIsNonEmptyTextFrame : 1;
bool mIsNonWhitespaceTextFrame : 1;
bool mIsLetterFrame : 1;
bool mRecomputeOverflow : 1;
bool mIsMarker : 1;
bool mSkipWhenTrimmingWhitespace : 1;
bool mIsEmpty : 1;
bool mIsPlaceholder : 1;
bool mIsLinkedToBase : 1;
// Other state we use
uint8_t mBlockDirAlign;
mozilla::WritingMode mWritingMode;
PerFrameData* Last() {
PerFrameData* pfd = this;
while (pfd->mNext) {
pfd = pfd->mNext;
return pfd;
bool IsStartJustifiable() const {
return mJustificationInfo.mIsStartJustifiable;
bool IsEndJustifiable() const {
return mJustificationInfo.mIsEndJustifiable;
bool ParticipatesInJustification() const;
PerFrameData* mFrameFreeList;
// In nsLineLayout, a "span" is a container inline frame, and a "frame" is one
// of its children.
// nsLineLayout::BeginLineReflow() creates the initial PerSpanData which is
// called the "root span". nsInlineFrame::ReflowFrames() creates a new
// PerSpanData when it calls nsLineLayout::BeginSpan(); at this time, the
// nsLineLayout object's mCurrentSpan is switched to the new span. The new
// span records the old mCurrentSpan as its parent. After reflowing the child
// inline frames, nsInlineFrame::ReflowFrames() calls nsLineLayout::EndSpan(),
// which pops the PerSpanData and re-sets mCurrentSpan.
struct PerSpanData {
union {
PerSpanData* mParent;
PerSpanData* mNextFreeSpan;
// The PerFrameData of the inline frame that "owns" the span, or null if
// this is the root span. mFrame is initialized to the containing inline
// frame's PerFrameData when a new PerSpanData is pushed in
// nsLineLayout::BeginSpan().
PerFrameData* mFrame;
// The first PerFrameData structure in the span.
PerFrameData* mFirstFrame;
// The last PerFrameData structure in the span. PerFrameData structures are
// added to the span as they are reflowed. mLastFrame may also be directly
// manipulated if a line is split, or if frames are pushed from one line to
// the next.
PerFrameData* mLastFrame;
const ReflowInput* mReflowInput;
bool mNoWrap;
mozilla::WritingMode mWritingMode;
bool mContainsFloat;
bool mHasNonemptyContent;
nscoord mIStart;
nscoord mICoord;
nscoord mIEnd;
nscoord mInset;
nscoord mBStartLeading, mBEndLeading;
nscoord mLogicalBSize;
nscoord mMinBCoord, mMaxBCoord;
nscoord* mBaseline;
void AppendFrame(PerFrameData* pfd) {
if (!mLastFrame) {
mFirstFrame = pfd;
} else {
mLastFrame->mNext = pfd;
pfd->mPrev = mLastFrame;
mLastFrame = pfd;
PerSpanData* mSpanFreeList;
PerSpanData* mRootSpan;
PerSpanData* mCurrentSpan;
// The container size to use when converting between logical and
// physical coordinates for frames in this span. For the root span
// this is the size of the block cached in mContainerSize; for
// child spans it's the size of the root span.
nsSize ContainerSizeForSpan(PerSpanData* aPSD) {
return (aPSD == mRootSpan)
? mContainerSize
: aPSD->mFrame->mBounds.Size(mRootSpan->mWritingMode)
// Get the advance of any trailing hangable whitespace. If the whitespace
// has directionality opposite to the line, the result is negated.
nscoord GetHangFrom(const PerSpanData* aSpan, bool aLineIsRTL) const;
gfxTextRun::TrimmableWS GetTrimFrom(const PerSpanData* aSpan,
bool aLineIsRTL) const;
gfxBreakPriority mLastOptionalBreakPriority;
int32_t mLastOptionalBreakFrameOffset;
int32_t mForceBreakFrameOffset;
nscoord mMinLineBSize;
// The amount of text indent that we applied to this line, needed for
// max-element-size calculation.
nscoord mTextIndent;
// This state varies during the reflow of a line but is line
// "global" state not span "local" state.
int32_t mLineNumber;
mozilla::JustificationInfo mJustificationInfo;
int32_t mTotalPlacedFrames;
nscoord mBStartEdge;
nscoord mMaxStartBoxBSize;
nscoord mMaxEndBoxBSize;
nscoord mInflationMinFontSize;
// Final computed line-bSize value after VerticalAlignFrames for
// the block has been called.
nscoord mFinalLineBSize;
// Amount of trimmable whitespace inline size for the trailing text
// frame, if any
nscoord mTrimmableISize;
// Physical size. Use only for physical <-> logical coordinate conversion.
nsSize mContainerSize;
const nsSize& ContainerSize() const { return mContainerSize; }
bool mFirstLetterStyleOK : 1;
bool mIsTopOfPage : 1;
bool mImpactedByFloats : 1;
bool mLastFloatWasLetterFrame : 1;
bool mLineIsEmpty : 1;
bool mLineEndsInBR : 1;
bool mNeedBackup : 1;
bool mInFirstLine : 1;
bool mGotLineBox : 1;
bool mInFirstLetter : 1;
bool mHasMarker : 1;
bool mDirtyNextLine : 1;
bool mLineAtStart : 1;
bool mHasRuby : 1;
bool mSuppressLineWrap : 1;
bool mUsedOverflowWrap : 1;
int32_t mSpanDepth;
#ifdef DEBUG
int32_t mSpansAllocated, mSpansFreed;
int32_t mFramesAllocated, mFramesFreed;
* Per span and per frame data.
mozilla::ArenaAllocator<1024, sizeof(void*)> mArena;
* Allocate a PerFrameData from the mArena pool. The allocation is infallible.
PerFrameData* NewPerFrameData(nsIFrame* aFrame);
* Allocate a PerSpanData from the mArena pool. The allocation is infallible.
PerSpanData* NewPerSpanData();
PerFrameData* LastFrame() const { return mCurrentSpan->mLastFrame; }
* Unlink the given PerFrameData and all the siblings after it from
* the span. The unlinked PFDs are usually freed immediately.
* However, if PFD_ISLINKEDTOBASE is set, it won't be freed until
* the frame of its base is unlinked.
void UnlinkFrame(PerFrameData* pfd);
* Free the given PerFrameData.
void FreeFrame(PerFrameData* pfd);
void FreeSpan(PerSpanData* psd);
bool InBlockContext() const { return mSpanDepth == 0; }
void PushFrame(nsIFrame* aFrame);
void AllowForStartMargin(PerFrameData* pfd, ReflowInput& aReflowInput);
void SyncAnnotationBounds(PerFrameData* aRubyFrame);
bool CanPlaceFrame(PerFrameData* pfd, bool aNotSafeToBreak,
bool aFrameCanContinueTextRun,
bool aCanRollBackBeforeFrame, ReflowOutput& aMetrics,
nsReflowStatus& aStatus, bool* aOptionalBreakAfterFits);
void PlaceFrame(PerFrameData* pfd, ReflowOutput& aMetrics);
void AdjustLeadings(nsIFrame* spanFrame, PerSpanData* psd,
const nsStyleText* aStyleText, float aInflation,
bool* aZeroEffectiveSpanBox);
void VerticalAlignFrames(PerSpanData* psd);
void PlaceTopBottomFrames(PerSpanData* psd, nscoord aDistanceFromStart,
nscoord aLineBSize);
void ApplyRelativePositioning(PerFrameData* aPFD);
void RelativePositionAnnotations(PerSpanData* aRubyPSD,
mozilla::OverflowAreas& aOverflowAreas);
void RelativePositionFrames(PerSpanData* psd,
mozilla::OverflowAreas& aOverflowAreas);
bool TrimTrailingWhiteSpaceIn(PerSpanData* psd, nscoord* aDeltaISize);
struct JustificationComputationState;
static int AssignInterframeJustificationGaps(
PerFrameData* aFrame, JustificationComputationState& aState);
int32_t ComputeFrameJustification(PerSpanData* psd,
JustificationComputationState& aState);
void AdvanceAnnotationInlineBounds(PerFrameData* aPFD,
const nsSize& aContainerSize,
nscoord aDeltaICoord, nscoord aDeltaISize);
void ApplyLineJustificationToAnnotations(PerFrameData* aPFD,
nscoord aDeltaICoord,
nscoord aDeltaISize);
// Apply justification. The return value is the amount by which the width of
// the span corresponding to aPSD got increased due to justification.
nscoord ApplyFrameJustification(
PerSpanData* aPSD, mozilla::JustificationApplicationState& aState);
void ExpandRubyBox(PerFrameData* aFrame, nscoord aReservedISize,
const nsSize& aContainerSize);
void ExpandRubyBoxWithAnnotations(PerFrameData* aFrame,
const nsSize& aContainerSize);
void ExpandInlineRubyBoxes(PerSpanData* aSpan);
void AttachFrameToBaseLineLayout(PerFrameData* aFrame);
#ifdef DEBUG
void DumpPerSpanData(PerSpanData* psd, int32_t aIndent);
static bool ShouldApplyLineHeightInPreserveWhiteSpace(const PerSpanData* psd);
#endif /* nsLineLayout_h___ */