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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 */
* rendering object for CSS display:block, inline-block, and list-item
* boxes, also used for various anonymous boxes
#ifndef nsBlockFrame_h___
#define nsBlockFrame_h___
#include "nsContainerFrame.h"
#include "nsHTMLParts.h"
#include "nsLineBox.h"
#include "nsCSSPseudoElements.h"
#include "nsFloatManager.h"
enum class LineReflowStatus {
// The line was completely reflowed and fit in available width, and we should
// try to pull up content from the next line if possible.
// The line was completely reflowed and fit in available width, but we should
// not try to pull up content from the next line.
// We need to reflow the line again at its current vertical position. The
// new reflow should not try to pull up any frames from the next line.
// We need to reflow the line again using the floats from its height
// this reflow, since its height made it hit floats that were not
// adjacent to its top.
// We need to reflow the line again at a lower vertical postion where there
// may be more horizontal space due to different float configuration.
// The line did not fit in the available vertical space. Try pushing it to
// the next page or column if it's not the first line on the current
// page/column.
class nsBlockInFlowLineIterator;
namespace mozilla {
class BlockReflowState;
class PresShell;
class ServoRestyleState;
class ServoStyleSet;
} // namespace mozilla
* Some invariants:
* -- The overflow out-of-flows list contains the out-of-
* flow frames whose placeholders are in the overflow list.
* -- A given piece of content has at most one placeholder
* frame in a block's normal child list.
* -- While a block is being reflowed, and from then until
* its next-in-flow is reflowed it may have a
* PushedFloatProperty frame property that points to
* an nsFrameList. This list contains continuations for
* floats whose prev-in-flow is in the block's regular float
* list and first-in-flows of floats that did not fit, but
* whose placeholders are in the block or one of its
* prev-in-flows.
* -- In all these frame lists, if there are two frames for
* the same content appearing in the list, then the frames
* appear with the prev-in-flow before the next-in-flow.
* -- While reflowing a block, its overflow line list
* will usually be empty but in some cases will have lines
* (while we reflow the block at its shrink-wrap width).
* In this case any new overflowing content must be
* prepended to the overflow lines.
* Base class for block and inline frames.
* The block frame has an additional child list, FrameChildListID::Absolute,
* which contains the absolutely positioned frames.
class nsBlockFrame : public nsContainerFrame {
using BlockReflowState = mozilla::BlockReflowState;
typedef nsLineList::iterator LineIterator;
typedef nsLineList::const_iterator ConstLineIterator;
typedef nsLineList::reverse_iterator ReverseLineIterator;
typedef nsLineList::const_reverse_iterator ConstReverseLineIterator;
LineIterator LinesBegin() { return mLines.begin(); }
LineIterator LinesEnd() { return mLines.end(); }
ConstLineIterator LinesBegin() const { return mLines.begin(); }
ConstLineIterator LinesEnd() const { return mLines.end(); }
ReverseLineIterator LinesRBegin() { return mLines.rbegin(); }
ReverseLineIterator LinesREnd() { return mLines.rend(); }
ConstReverseLineIterator LinesRBegin() const { return mLines.rbegin(); }
ConstReverseLineIterator LinesREnd() const { return mLines.rend(); }
LineIterator LinesBeginFrom(nsLineBox* aList) { return mLines.begin(aList); }
ReverseLineIterator LinesRBeginFrom(nsLineBox* aList) {
return mLines.rbegin(aList);
// Methods declared to be used in 'range-based-for-loop'
nsLineList& Lines() { return mLines; }
const nsLineList& Lines() const { return mLines; }
friend nsBlockFrame* NS_NewBlockFrame(mozilla::PresShell* aPresShell,
ComputedStyle* aStyle);
// nsQueryFrame
// nsIFrame
void Init(nsIContent* aContent, nsContainerFrame* aParent,
nsIFrame* aPrevInFlow) override;
void SetInitialChildList(ChildListID aListID,
nsFrameList&& aChildList) override;
void AppendFrames(ChildListID aListID, nsFrameList&& aFrameList) override;
void InsertFrames(ChildListID aListID, nsIFrame* aPrevFrame,
const nsLineList::iterator* aPrevFrameLine,
nsFrameList&& aFrameList) override;
void RemoveFrame(DestroyContext&, ChildListID, nsIFrame* aOldFrame) override;
nsContainerFrame* GetContentInsertionFrame() override;
void AppendDirectlyOwnedAnonBoxes(nsTArray<OwnedAnonBox>& aResult) override;
const nsFrameList& GetChildList(ChildListID aListID) const override;
void GetChildLists(nsTArray<ChildList>* aLists) const override;
nscoord SynthesizeFallbackBaseline(
mozilla::WritingMode aWM,
BaselineSharingGroup aBaselineGroup) const override;
BaselineSharingGroup GetDefaultBaselineSharingGroup() const override {
return BaselineSharingGroup::Last;
Maybe<nscoord> GetNaturalBaselineBOffset(
mozilla::WritingMode aWM, BaselineSharingGroup aBaselineGroup,
BaselineExportContext aExportContext) const override;
nscoord GetCaretBaseline() const override;
void Destroy(DestroyContext&) override;
bool IsFloatContainingBlock() const override;
void BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsDisplayListSet& aLists) override;
void InvalidateFrame(uint32_t aDisplayItemKey = 0,
bool aRebuildDisplayItems = true) override;
void InvalidateFrameWithRect(const nsRect& aRect,
uint32_t aDisplayItemKey = 0,
bool aRebuildDisplayItems = true) override;
void List(FILE* out = stderr, const char* aPrefix = "",
ListFlags aFlags = ListFlags()) const override;
nsresult GetFrameName(nsAString& aResult) const override;
#ifdef DEBUG
const char* LineReflowStatusToString(
LineReflowStatus aLineReflowStatus) const;
mozilla::a11y::AccType AccessibleType() override;
// Line cursor methods to speed up line searching in which one query result
// is expected to be close to the next in general. This is mainly for
// searching line(s) containing a point. It is also used as a cache for local
// computation. The basic idea for the former is that we set the cursor
// property if the lines' overflowArea.InkOverflow().ys and
// overflowArea.InkOverflow().yMosts are non-decreasing
// (considering only non-empty overflowArea.InkOverflow()s; empty
// overflowArea.InkOverflow()s never participate in event handling
// or painting), and the block has sufficient number of lines. The
// cursor property points to a "recently used" line. If we get a
// series of requests that work on lines
// "near" the cursor, then we can find those nearby lines quickly by
// starting our search at the cursor.
// We have two independent line cursors, one used for display-list building
// and the other for a11y or other frame queries. Either or both may be
// present at any given time. When we reflow or otherwise munge the lines,
// both cursors will be cleared.
// The display cursor is only created and used if the lines satisfy the non-
// decreasing y-coordinate condition (see SetupLineCursorForDisplay comment
// below), whereas the query cursor may be created for any block. The two
// are separated so creating a cursor for a11y queries (eg GetRenderedText)
// does not risk confusing the display-list building code.
// Clear out line cursors because we're disturbing the lines (i.e., Reflow)
void ClearLineCursors() {
if (MaybeHasLineCursor()) {
void ClearLineCursorForDisplay() {
void ClearLineCursorForQuery() { RemoveProperty(LineCursorPropertyQuery()); }
// Clear just the line-iterator property; this is used if we need to get a
// LineIterator temporarily during reflow, when using a persisted iterator
// would be invalid. So we clear the stored property immediately after use.
void ClearLineIterator() { RemoveProperty(LineIteratorProperty()); }
// Get the first line that might contain y-coord 'y', or nullptr if you must
// search all lines. If nonnull is returned then we guarantee that the lines'
// combinedArea.ys and combinedArea.yMosts are non-decreasing.
// The actual line returned might not contain 'y', but if not, it is
// guaranteed to be before any line which does contain 'y'.
nsLineBox* GetFirstLineContaining(nscoord y);
// Ensure the frame has a display-list line cursor, initializing it to the
// first line if it is not already present. (If there's an existing cursor,
// it is left untouched.) Only call this if you guarantee that the lines'
// combinedArea.ys and combinedArea.yMosts are non-decreasing.
void SetupLineCursorForDisplay();
// Ensure the frame has a query line cursor, initializing it to the first
// line if it is not already present. (If there's an existing cursor, it is
// left untouched.)
void SetupLineCursorForQuery();
void ChildIsDirty(nsIFrame* aChild) override;
bool IsEmpty() override;
bool CachedIsEmpty() override;
bool IsSelfEmpty() override;
// Given that we have a ::marker frame, does it actually draw something, i.e.,
// do we have either a 'list-style-type' or 'list-style-image' that is
// not 'none', and no 'content'?
bool MarkerIsEmpty() const;
// Return true if this frame has a ::marker frame.
bool HasMarker() const { return HasOutsideMarker() || HasInsideMarker(); }
// Return true if this frame has an inside ::marker frame.
bool HasInsideMarker() const {
// Return true if this frame has an outside ::marker frame.
bool HasOutsideMarker() const {
* @return the first-letter frame or nullptr if we don't have one.
nsIFrame* GetFirstLetter() const;
* @return the ::first-line frame or nullptr if we don't have one.
nsIFrame* GetFirstLineFrame() const;
void MarkIntrinsicISizesDirty() override;
// Whether CSS text-indent should be applied to the given line.
bool TextIndentAppliesTo(const LineIterator& aLine) const;
void CheckIntrinsicCacheAgainstShrinkWrapState();
template <typename LineIteratorType>
Maybe<nscoord> GetBaselineBOffset(LineIteratorType aStart,
LineIteratorType aEnd,
mozilla::WritingMode aWM,
BaselineSharingGroup aBaselineGroup,
BaselineExportContext aExportContext) const;
nscoord GetMinISize(gfxContext* aRenderingContext) override;
nscoord GetPrefISize(gfxContext* aRenderingContext) override;
nsRect ComputeTightBounds(DrawTarget* aDrawTarget) const override;
nsresult GetPrefWidthTightBounds(gfxContext* aContext, nscoord* aX,
nscoord* aXMost) override;
* Compute the final block size of this frame.
* @param aState BlockReflowState passed from parent during reflow.
* Note: aState.mReflowStatus is mostly an "input" parameter. When this
* method is called, it should represent what our status would be as if
* we were shrinkwrapping our children's block-size. This method will
* then adjust it before returning if our status is different in light
* of our actual final block-size and current page/column's available
* block-size.
* @param aBEndEdgeOfChildren The distance between this frame's block-start
* border-edge and the block-end edge of our last child's border-box.
* This is effectively our block-start border-padding plus the
* block-size of our children, precomputed outside of this function.
* @return our final block-size with respect to aReflowInput's writing-mode.
nscoord ComputeFinalBSize(BlockReflowState& aState,
nscoord aBEndEdgeOfChildren);
void Reflow(nsPresContext* aPresContext, ReflowOutput& aDesiredSize,
const ReflowInput& aReflowInput,
nsReflowStatus& aStatus) override;
* Move any frames on our overflow list to the end of our principal list.
* @return true if there were any overflow frames
bool DrainSelfOverflowList() override;
void StealFrame(nsIFrame* aChild) override;
void DeleteNextInFlowChild(DestroyContext&, nsIFrame* aNextInFlow,
bool aDeletingEmptyFrames) override;
* This is a special method that allows a child class of nsBlockFrame to
* return a special, customized nsStyleText object to the nsLineLayout
* constructor. It is used when the nsBlockFrame child needs to specify its
* custom rendering style.
virtual const nsStyleText* StyleTextForLineLayout();
* Determines whether the collapsed margin carried out of the last
* line includes the margin-top of a line with clearance (in which
* case we must avoid collapsing that margin with our bottom margin)
bool CheckForCollapsedBEndMarginFromClearanceLine();
static nsresult GetCurrentLine(BlockReflowState* aState,
nsLineBox** aOutCurrentLine);
* Determine if this block is a margin root at the top/bottom edges.
void IsMarginRoot(bool* aBStartMarginRoot, bool* aBEndMarginRoot);
static bool BlockNeedsFloatManager(nsIFrame* aBlock);
* Returns whether aFrame is a block frame that will wrap its contents
* around floats intruding on it from the outside. (aFrame need not
* be a block frame, but if it's not, the result will be false.)
* Note: We often use the term "float-avoiding block" to refer to
* block-level frames for whom this function returns false.
static bool BlockCanIntersectFloats(nsIFrame* aFrame);
* Returns the inline size that needs to be cleared past floats for
* blocks that avoid (i.e. cannot intersect) floats. aState must already
* have GetFloatAvailableSpace called on it for the block-dir position that
* we care about (which need not be its current mBCoord)
struct FloatAvoidingISizeToClear {
// Note that we care about the inline-start margin but can ignore
// the inline-end margin.
nscoord marginIStart, borderBoxISize;
static FloatAvoidingISizeToClear ISizeToClearPastFloats(
const BlockReflowState& aState,
const mozilla::LogicalRect& aFloatAvailableSpace,
nsIFrame* aFloatAvoidingBlock);
* Creates a contination for aFloat and adds it to the list of overflow
* floats. Also updates aState.mReflowStatus to include the float's
* incompleteness. Must only be called while this block frame is in reflow.
* aFloatStatus must be the float's true, unmodified reflow status.
void SplitFloat(BlockReflowState& aState, nsIFrame* aFloat,
const nsReflowStatus& aFloatStatus);
* Walks up the frame tree, starting with aCandidate, and returns the first
* block frame that it encounters.
static nsBlockFrame* GetNearestAncestorBlock(nsIFrame* aCandidate);
struct FrameLines {
nsLineList mLines;
nsFrameList mFrames;
* Update the styles of our various pseudo-elements (marker, first-line,
* etc, but _not_ first-letter).
void UpdatePseudoElementStyles(mozilla::ServoRestyleState& aRestyleState);
// Update our first-letter styles during stylo post-traversal. This needs to
// be done at a slightly different time than our other pseudo-elements.
void UpdateFirstLetterStyle(mozilla::ServoRestyleState& aRestyleState);
explicit nsBlockFrame(ComputedStyle* aStyle, nsPresContext* aPresContext,
ClassID aID = kClassID)
: nsContainerFrame(aStyle, aPresContext, aID) {
#ifdef DEBUG
virtual ~nsBlockFrame();
void DidSetComputedStyle(ComputedStyle* aOldStyle) override;
#ifdef DEBUG
already_AddRefed<ComputedStyle> GetFirstLetterStyle(
nsPresContext* aPresContext);
// Note that the NS_BLOCK_HAS_LINE_CURSOR flag does not necessarily mean the
// cursor is present, as it covers both the "display" and "query" cursors,
// but may remain set if they have been separately deleted. In such a case,
// the Get* accessors will be slightly more expensive, but will still safely
// return null if the cursor is absent.
bool MaybeHasLineCursor() {
return HasAnyStateBits(NS_BLOCK_HAS_LINE_CURSOR);
nsLineBox* GetLineCursorForDisplay() {
return MaybeHasLineCursor() ? GetProperty(LineCursorPropertyDisplay())
: nullptr;
nsLineBox* GetLineCursorForQuery() {
return MaybeHasLineCursor() ? GetProperty(LineCursorPropertyQuery())
: nullptr;
nsLineBox* NewLineBox(nsIFrame* aFrame, bool aIsBlock) {
return NS_NewLineBox(PresShell(), aFrame, aIsBlock);
nsLineBox* NewLineBox(nsLineBox* aFromLine, nsIFrame* aFrame,
int32_t aCount) {
return NS_NewLineBox(PresShell(), aFromLine, aFrame, aCount);
void FreeLineBox(nsLineBox* aLine) {
if (aLine == GetLineCursorForDisplay()) {
if (aLine == GetLineCursorForQuery()) {
* Helper method for StealFrame.
void RemoveFrameFromLine(nsIFrame* aChild, nsLineList::iterator aLine,
nsFrameList& aFrameList, nsLineList& aLineList);
void TryAllLines(nsLineList::iterator* aIterator,
nsLineList::iterator* aStartIterator,
nsLineList::iterator* aEndIterator, bool* aInOverflowLines,
FrameLines** aOverflowLines);
/** move the frames contained by aLine by aDeltaBCoord
* if aLine is a block, its child floats are added to the state manager
void SlideLine(BlockReflowState& aState, nsLineBox* aLine,
nscoord aDeltaBCoord);
void UpdateLineContainerSize(nsLineBox* aLine,
const nsSize& aNewContainerSize);
// helper for SlideLine and UpdateLineContainerSize
void MoveChildFramesOfLine(nsLineBox* aLine, nscoord aDeltaBCoord);
// Returns block-end edge of children.
nscoord ComputeFinalSize(const ReflowInput& aReflowInput,
BlockReflowState& aState, ReflowOutput& aMetrics);
* Calculates the necessary shift to honor 'align-content' and applies it.
void AlignContent(BlockReflowState& aState, ReflowOutput& aMetrics,
nscoord aBEndEdgeOfChildren);
// Stash the effective align-content shift value between reflows
* Helper method for Reflow(). Computes the overflow areas created by our
* children, and includes them into aOverflowAreas.
void ComputeOverflowAreas(mozilla::OverflowAreas& aOverflowAreas,
nscoord aBEndEdgeOfChildren,
const nsStyleDisplay* aDisplay) const;
* Helper method for ComputeOverflowAreas(). Incorporates aBEndEdgeOfChildren
* into the aOverflowAreas.
void ConsiderBlockEndEdgeOfChildren(mozilla::OverflowAreas& aOverflowAreas,
nscoord aBEndEdgeOfChildren,
const nsStyleDisplay* aDisplay) const;
* Add the frames in aFrameList to this block after aPrevSibling.
* This block thinks in terms of lines, but the frame construction code
* knows nothing about lines at all so we need to find the line that
* contains aPrevSibling and add aFrameList after aPrevSibling on that line.
* New lines are created as necessary to handle block data in aFrameList.
* This function will clear aFrameList.
* aPrevSiblingLine, if present, must be the line containing aPrevSibling.
* Providing it will make this function faster.
void AddFrames(nsFrameList&& aFrameList, nsIFrame* aPrevSibling,
const nsLineList::iterator* aPrevSiblingLine);
// Return the :-moz-block-ruby-content child frame, if any.
// (It's non-null only if this block frame is for 'display:block ruby'.)
nsContainerFrame* GetRubyContentPseudoFrame();
* Perform Bidi resolution on this frame
nsresult ResolveBidi();
* Test whether the frame is a form control in a visual Bidi page.
* This is necessary for backwards-compatibility, because most visual
* pages use logical order for form controls so that they will
* display correctly on native widgets in OSs with Bidi support
* @param aPresContext the pres context
* @return whether the frame is a BIDI form control
bool IsVisualFormControl(nsPresContext* aPresContext);
/** Whether this block has an effective align-content property */
bool IsAligned() const {
return StylePosition()->mAlignContent.primary !=
nscoord GetAlignContentShift() const {
return IsAligned() ? GetProperty(AlignContentShift()) : 0;
* For text-wrap:balance, we iteratively try reflowing with adjusted inline
* size to find the "best" result (the tightest size that can be applied
* without increasing the total line count of the block).
* This record is used to manage the state of these "trial reflows", and
* return results from the final trial.
struct TrialReflowState {
// Values pre-computed at start of Reflow(), constant across trials.
const nscoord mConsumedBSize;
const nscoord mEffectiveContentBoxBSize;
bool mNeedFloatManager;
// [out] Whether reflowing resulted in use of an overflow-wrap break.
bool mUsedOverflowWrap = false;
// Settings for the current trial.
bool mBalancing = false;
nscoord mInset = 0;
// Results computed during the trial reflow. Values from the final trial
// will be used by the remainder of Reflow().
mozilla::OverflowAreas mOcBounds;
mozilla::OverflowAreas mFcBounds;
nscoord mBlockEndEdgeOfChildren = 0;
nscoord mContainerWidth = 0;
// Initialize for the initial trial reflow, with zero inset.
TrialReflowState(nscoord aConsumedBSize, nscoord aEffectiveContentBoxBSize,
bool aNeedFloatManager)
: mConsumedBSize(aConsumedBSize),
mNeedFloatManager(aNeedFloatManager) {}
// Adjust the inset amount, and reset state for a new trial.
void ResetForBalance(nscoord aInsetDelta) {
// Tells the reflow-lines loop we must consider all lines "dirty" (as we
// are modifying the effective inline-size to be used).
mBalancing = true;
// Adjust inset to apply.
mInset += aInsetDelta;
// Re-initialize state that the reflow loop will compute.
mBlockEndEdgeOfChildren = 0;
mContainerWidth = 0;
mUsedOverflowWrap = false;
* Internal helper for Reflow(); may be called repeatedly during a single
* Reflow() in order to implement text-wrap:balance.
* This method applies aTrialState.mInset during line-breaking to reduce
* the effective available inline-size (without affecting alignment).
nsReflowStatus TrialReflow(nsPresContext* aPresContext,
ReflowOutput& aMetrics,
const ReflowInput& aReflowInput,
TrialReflowState& aTrialState);
* Helper function for the frame ctor to register a ::marker frame.
void SetMarkerFrameForListItem(nsIFrame* aMarkerFrame);
* Does all the real work for removing aDeletedFrame
* -- finds the line containing aDeletedFrame
* -- removes all aDeletedFrame next-in-flows (or all continuations,
* -- marks lines dirty as needed
* -- marks textruns dirty (unless FRAMES_ARE_EMPTY is given, in which
* case textruns do not need to be dirtied)
* -- destroys all removed frames
void DoRemoveFrame(DestroyContext&, nsIFrame* aDeletedFrame, uint32_t aFlags);
void ReparentFloats(nsIFrame* aFirstFrame, nsBlockFrame* aOldParent,
bool aReparentSiblings);
bool ComputeCustomOverflow(mozilla::OverflowAreas&) override;
void UnionChildOverflow(mozilla::OverflowAreas&) override;
* Load all of aFrame's floats into the float manager iff aFrame is not a
* block formatting context. Handles all necessary float manager translations;
* assumes float manager is in aFrame's parent's coord system.
* Safe to call on non-blocks (does nothing).
static void RecoverFloatsFor(nsIFrame* aFrame, nsFloatManager& aFloatManager,
mozilla::WritingMode aWM,
const nsSize& aContainerSize);
* Determine if we have any pushed floats from a previous continuation.
* @returns true, if any of the floats at the beginning of our floats list
* have the NS_FRAME_IS_PUSHED_FLOAT bit set; false otherwise.
bool HasPushedFloatsFromPrevContinuation() const;
// @see nsIFrame::AddSizeOfExcludingThisForTree
void AddSizeOfExcludingThisForTree(nsWindowSizes&) const override;
* Clears any -webkit-line-clamp ellipsis on a line in this block or one
* of its descendants.
void ClearLineClampEllipsis();
* Returns whether this block is in a -webkit-line-clamp context. That is,
* whether this block is in a block formatting-context whose root block has
* -webkit-line-clamp: <n>.
bool IsInLineClampContext() const;
* @return false iff this block does not have a float on any child list.
* This function is O(1).
bool MaybeHasFloats() const;
/** grab overflow lines from this block's prevInFlow, and make them
* part of this block's mLines list.
* @return true if any lines were drained.
bool DrainOverflowLines();
* Moves frames from our PushedFloats list back into our mFloats list.
void DrainSelfPushedFloats();
* First calls DrainSelfPushedFloats() then grabs pushed floats from this
* block's prev-in-flow, and splice them into this block's mFloats list too.
void DrainPushedFloats();
/** Load all our floats into the float manager (without reflowing them).
* Assumes float manager is in our own coordinate system.
void RecoverFloats(nsFloatManager& aFloatManager, mozilla::WritingMode aWM,
const nsSize& aContainerSize);
/** Reflow pushed floats
void ReflowPushedFloats(BlockReflowState& aState,
mozilla::OverflowAreas& aOverflowAreas);
* Find any trailing BR clear from the last line of this block (or from its
* prev-in-flows).
mozilla::StyleClear FindTrailingClear();
* Remove a float from our float list.
void RemoveFloat(nsIFrame* aFloat);
* Remove a float from the float cache for the line its placeholder is on.
void RemoveFloatFromFloatCache(nsIFrame* aFloat);
void CollectFloats(nsIFrame* aFrame, nsFrameList& aList,
bool aCollectFromSiblings) {
if (MaybeHasFloats()) {
DoCollectFloats(aFrame, aList, aCollectFromSiblings);
void DoCollectFloats(nsIFrame* aFrame, nsFrameList& aList,
bool aCollectFromSiblings);
// Remove a float, abs, rel positioned frame from the appropriate block's list
static void DoRemoveOutOfFlowFrame(DestroyContext&, nsIFrame*);
/** set up the conditions necessary for an resize reflow
* the primary task is to mark the minimumly sufficient lines dirty.
void PrepareResizeReflow(BlockReflowState& aState);
* Reflow all lines that have been marked dirty.
* Returns whether an overflow-wrap break was used anywhere.
bool ReflowDirtyLines(BlockReflowState& aState);
/** Mark a given line dirty due to reflow being interrupted on or before it */
void MarkLineDirtyForInterrupt(nsLineBox* aLine);
// Methods for line reflow
* Reflow a line.
* @param aState
* the current reflow input
* @param aLine
* the line to reflow. can contain a single block frame or contain 1 or
* more inline frames.
* @param aKeepReflowGoing [OUT]
* indicates whether the caller should continue to reflow more lines
* @returns
* whether an overflow-wrap breakpoint was used
bool ReflowLine(BlockReflowState& aState, LineIterator aLine,
bool* aKeepReflowGoing);
// Return false if it needs another reflow because of reduced space
// between floats that are next to it (but not next to its top), and
// return true otherwise.
bool PlaceLine(BlockReflowState& aState, nsLineLayout& aLineLayout,
LineIterator aLine,
nsFloatManager::SavedState* aFloatStateBeforeLine,
nsFlowAreaRect& aFlowArea, // in-out
nscoord& aAvailableSpaceBSize, // in-out
bool* aKeepReflowGoing);
* If NS_BLOCK_LOOK_FOR_DIRTY_FRAMES is set, call MarkLineDirty
* on any line with a child frame that is dirty.
void LazyMarkLinesDirty();
* Mark |aLine| dirty, and, if necessary because of possible
* pull-up, mark the previous line dirty as well. Also invalidates textruns
* on those lines because the text in the lines might have changed due to
* addition/removal of frames.
* @param aLine the line to mark dirty
* @param aLineList the line list containing that line
void MarkLineDirty(LineIterator aLine, const nsLineList* aLineList);
// XXX where to go
bool IsLastLine(BlockReflowState& aState, LineIterator aLine);
void DeleteLine(BlockReflowState& aState, nsLineList::iterator aLine,
nsLineList::iterator aLineEnd);
// Methods for individual frame reflow
bool ShouldApplyBStartMargin(BlockReflowState& aState, nsLineBox* aLine);
void ReflowBlockFrame(BlockReflowState& aState, LineIterator aLine,
bool* aKeepGoing);
// Returns whether an overflow-wrap break was used.
bool ReflowInlineFrames(BlockReflowState& aState, LineIterator aLine,
bool* aKeepLineGoing);
void DoReflowInlineFrames(
BlockReflowState& aState, nsLineLayout& aLineLayout, LineIterator aLine,
nsFlowAreaRect& aFloatAvailableSpace, nscoord& aAvailableSpaceBSize,
nsFloatManager::SavedState* aFloatStateBeforeLine, bool* aKeepReflowGoing,
LineReflowStatus* aLineReflowStatus, bool aAllowPullUp);
void ReflowInlineFrame(BlockReflowState& aState, nsLineLayout& aLineLayout,
LineIterator aLine, nsIFrame* aFrame,
LineReflowStatus* aLineReflowStatus);
// @param aReflowStatus an incomplete status indicates the float should be
// split but only if the available block-size is constrained.
void ReflowFloat(BlockReflowState& aState, ReflowInput& aFloatRI,
nsIFrame* aFloat, nsReflowStatus& aReflowStatus);
// Methods for pushing/pulling lines/frames
* Create a next-in-flow, if necessary, for aFrame. If a new frame is
* created, place it in aLine if aLine is not null.
* @param aState the block reflow state
* @param aLine where to put a new frame
* @param aFrame the frame
* @return true if a new frame was created, false if not
bool CreateContinuationFor(BlockReflowState& aState, nsLineBox* aLine,
nsIFrame* aFrame);
* Set line-break-before status in aState.mReflowStatus because aLine cannot
* be placed on this page/column and we don't want to break within ourselves.
* Also, mark the aLine dirty, and set aKeepReflowGoing to false;
void SetBreakBeforeStatusBeforeLine(BlockReflowState& aState,
LineIterator aLine,
bool* aKeepReflowGoing);
* Indicates if we need to compute a page name for the next page when pushing
* a truncated line.
* Using a value of No saves work when a new page name has already been set
* with nsCSSFrameConstructor::SetNextPageContentFramePageName.
enum class ComputeNewPageNameIfNeeded : uint8_t { Yes, No };
* Push aLine (and any after it), since it cannot be placed on this
* page/column. Set aKeepReflowGoing to false and set
* flag aState.mReflowStatus as incomplete.
void PushTruncatedLine(BlockReflowState& aState, LineIterator aLine,
bool* aKeepReflowGoing,
ComputeNewPageNameIfNeeded aComputeNewPageName =
void SplitLine(BlockReflowState& aState, nsLineLayout& aLineLayout,
LineIterator aLine, nsIFrame* aFrame,
LineReflowStatus* aLineReflowStatus);
* Pull a frame from the next available location (one of our lines or
* one of our next-in-flows lines).
* @return the pulled frame or nullptr
nsIFrame* PullFrame(BlockReflowState& aState, LineIterator aLine);
* Try to pull a frame out of a line pointed at by aFromLine.
* Note: pulling a frame from a line that is a place-holder frame
* doesn't automatically remove the corresponding float from the
* line's float array. This happens indirectly: either the line gets
* emptied (and destroyed) or the line gets reflowed (because we mark
* it dirty) and the code at the top of ReflowLine empties the
* array. So eventually, it will be removed, just not right away.
* @return the pulled frame or nullptr
nsIFrame* PullFrameFrom(nsLineBox* aLine, nsBlockFrame* aFromContainer,
nsLineList::iterator aFromLine);
* Push the line after aLineBefore to the overflow line list.
* @param aLineBefore a line in 'mLines' (or LinesBegin() when
* pushing the first line)
void PushLines(BlockReflowState& aState, nsLineList::iterator aLineBefore);
void PropagateFloatDamage(BlockReflowState& aState, nsLineBox* aLine,
nscoord aDeltaBCoord);
void CheckFloats(BlockReflowState& aState);
// List handling kludge
void ReflowOutsideMarker(nsIFrame* aMarkerFrame, BlockReflowState& aState,
ReflowOutput& aMetrics, nscoord aLineTop);
NS_DECLARE_FRAME_PROPERTY_DELETABLE(LineIteratorProperty, nsLineIterator);
bool CanProvideLineIterator() const final { return true; }
nsILineIterator* GetLineIterator() final;
bool HasOverflowLines() const {
FrameLines* GetOverflowLines() const;
FrameLines* RemoveOverflowLines();
void SetOverflowLines(FrameLines* aOverflowLines);
void DestroyOverflowLines();
* This class is useful for efficiently modifying the out of flow
* overflow list. It gives the client direct writable access to
* the frame list temporarily but ensures that property is only
* written back if absolutely necessary.
struct nsAutoOOFFrameList {
nsFrameList mList;
explicit nsAutoOOFFrameList(nsBlockFrame* aBlock)
: mPropValue(aBlock->GetOverflowOutOfFlows()), mBlock(aBlock) {
if (mPropValue) {
mList = std::move(*mPropValue);
~nsAutoOOFFrameList() {
mBlock->SetOverflowOutOfFlows(std::move(mList), mPropValue);
nsFrameList* const mPropValue;
nsBlockFrame* const mBlock;
friend struct nsAutoOOFFrameList;
nsFrameList* GetOverflowOutOfFlows() const;
// This takes ownership of the frames in aList.
void SetOverflowOutOfFlows(nsFrameList&& aList, nsFrameList* aPropValue);
// Return the ::marker frame or nullptr if we don't have one.
nsIFrame* GetMarker() const {
nsIFrame* outside = GetOutsideMarker();
return outside ? outside : GetInsideMarker();
// Return the inside ::marker frame or nullptr if we don't have one.
nsIFrame* GetInsideMarker() const;
// Return the outside ::marker frame or nullptr if we don't have one.
nsIFrame* GetOutsideMarker() const;
// Return the outside ::marker frame list frame property.
nsFrameList* GetOutsideMarkerList() const;
// Return true if this frame has floats.
bool HasFloats() const;
// Get the floats list, or nullptr if there isn't one.
nsFrameList* GetFloats() const;
// Get the floats list, or if there is not currently one, make a new empty
// one.
nsFrameList* EnsureFloats() MOZ_NONNULL_RETURN;
// Get the float list and remove the property from this frame.
// The caller is responsible for deleting the returned list and managing the
// ownership of all frames in the list.
[[nodiscard]] nsFrameList* StealFloats();
// Return true if this frame has pushed floats.
bool HasPushedFloats() const;
// Get the pushed floats list, or nullptr if there isn't one.
// The pushed floats list is used for *temporary* storage of floats during
// reflow, between when we decide they don't fit in this block until our next
// continuation takes them.
nsFrameList* GetPushedFloats() const;
// Get the pushed floats list, or if there is not currently one,
// make a new empty one.
nsFrameList* EnsurePushedFloats() MOZ_NONNULL_RETURN;
// Get the pushed float list and remove the property from this frame.
// The caller is responsible for deleting the returned list and managing the
// ownership of all frames in the list.
[[nodiscard]] nsFrameList* StealPushedFloats();
#ifdef DEBUG
void VerifyLines(bool aFinalCheckOK);
void VerifyOverflowSituation();
int32_t GetDepth() const;
nscoord mCachedPrefISize = NS_INTRINSIC_ISIZE_UNKNOWN;
nsLineList mLines;
friend class mozilla::BlockReflowState;
friend class nsBlockInFlowLineIterator;
#ifdef DEBUG
static bool gLamePaintMetrics;
static bool gLameReflowMetrics;
static bool gNoisy;
static bool gNoisyDamageRepair;
static bool gNoisyIntrinsic;
static bool gNoisyReflow;
static bool gReallyNoisyReflow;
static bool gNoisyFloatManager;
static bool gVerifyLines;
static bool gDisableResizeOpt;
static int32_t gNoiseIndent;
static const char* kReflowCommandType[];
static void InitDebugFlags();
#ifdef DEBUG
class AutoNoisyIndenter {
explicit AutoNoisyIndenter(bool aDoIndent) : mIndented(aDoIndent) {
if (mIndented) {
~AutoNoisyIndenter() {
if (mIndented) {
bool mIndented;
* Iterates over all lines in the prev-in-flows/next-in-flows of this block.
class nsBlockInFlowLineIterator {
typedef nsBlockFrame::LineIterator LineIterator;
* Set up the iterator to point to aLine which must be a normal line
* in aFrame (not an overflow line).
nsBlockInFlowLineIterator(nsBlockFrame* aFrame, LineIterator aLine);
* Set up the iterator to point to the first line found starting from
* aFrame. Sets aFoundValidLine to false if there is no such line.
* After aFoundValidLine has returned false, don't call any methods on this
* object again.
nsBlockInFlowLineIterator(nsBlockFrame* aFrame, bool* aFoundValidLine);
* Set up the iterator to point to the line that contains aFindFrame (either
* directly or indirectly). If aFrame is out of flow, or contained in an
* out-of-flow, finds the line containing the out-of-flow's placeholder. If
* the frame is not found, sets aFoundValidLine to false. After
* aFoundValidLine has returned false, don't call any methods on this
* object again.
nsBlockInFlowLineIterator(nsBlockFrame* aFrame, nsIFrame* aFindFrame,
bool* aFoundValidLine);
// Allow to be uninitialized (and then assigned from another object).
nsBlockInFlowLineIterator() : mFrame(nullptr) {}
LineIterator GetLine() { return mLine; }
bool IsLastLineInList();
nsBlockFrame* GetContainer() { return mFrame; }
bool GetInOverflow() { return mLineList != &mFrame->mLines; }
* Returns the current line list we're iterating, null means
* we're iterating |mLines| of the container.
nsLineList* GetLineList() { return mLineList; }
* Returns the end-iterator of whatever line list we're in.
LineIterator End();
* Returns false if there are no more lines. After this has returned false,
* don't call any methods on this object again.
bool Next();
* Returns false if there are no more lines. After this has returned false,
* don't call any methods on this object again.
bool Prev();
// XXX nsBlockFrame uses this internally in one place. Try to remove it.
// XXX uhm, and nsBidiPresUtils::Resolve too.
nsBlockInFlowLineIterator(nsBlockFrame* aFrame, LineIterator aLine,
bool aInOverflow);
nsBlockFrame* mFrame;
LineIterator mLine;
nsLineList* mLineList; // the line list mLine is in
* Moves iterator to next valid line reachable from the current block.
* Returns false if there are no valid lines.
bool FindValidLine();
#endif /* nsBlockFrame_h___ */