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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 */
/* struct containing the input to nsIFrame::Reflow */
#ifndef mozilla_ReflowInput_h
#define mozilla_ReflowInput_h
#include "nsMargin.h"
#include "nsStyleConsts.h"
#include "mozilla/Assertions.h"
#include "mozilla/EnumSet.h"
#include "mozilla/Maybe.h"
#include "mozilla/WritingModes.h"
#include "LayoutConstants.h"
#include "ReflowOutput.h"
#include <algorithm>
class gfxContext;
class nsFloatManager;
struct nsHypotheticalPosition;
class nsIPercentBSizeObserver;
class nsLineLayout;
class nsPlaceholderFrame;
class nsPresContext;
class nsReflowStatus;
namespace mozilla {
enum class LayoutFrameType : uint8_t;
* A set of StyleSizes used as an input parameter to various functions that
* compute sizes like nsIFrame::ComputeSize(). If any of the member fields has a
* value, the function may use the value instead of retrieving it from the
* frame's style.
* The logical sizes are assumed to be in the associated frame's writing-mode.
struct StyleSizeOverrides {
Maybe<StyleSize> mStyleISize;
Maybe<StyleSize> mStyleBSize;
Maybe<AspectRatio> mAspectRatio;
bool HasAnyOverrides() const { return mStyleISize || mStyleBSize; }
bool HasAnyLengthOverrides() const {
return (mStyleISize && mStyleISize->ConvertsToLength()) ||
(mStyleBSize && mStyleBSize->ConvertsToLength());
// By default, table wrapper frame considers the size overrides applied to
// itself, so it creates any length size overrides for inner table frame by
// subtracting the area occupied by the caption and border & padding according
// to box-sizing.
// When this flag is true, table wrapper frame is required to apply the size
// overrides to the inner table frame directly, without any modification,
// which is useful for flex container to override the inner table frame's
// preferred main size with 'flex-basis'.
// Note: if mStyleISize is a LengthPercentage, the inner table frame will
// comply with the inline-size override without enforcing its min-content
// inline-size in nsTableFrame::ComputeSize(). This is necessary so that small
// flex-basis values like 'flex-basis:1%' can be resolved correctly; the
// flexbox layout algorithm does still explicitly clamp to min-sizes *at a
// later step*, after the flex-basis has been resolved -- so this flag won't
// actually produce any user-visible tables whose final inline size is smaller
// than their min-content inline size.
bool mApplyOverridesVerbatim = false;
} // namespace mozilla
* @return aValue clamped to [aMinValue, aMaxValue].
* @note This function needs to handle aMinValue > aMaxValue. In that case,
* aMinValue is returned. That's why we cannot use std::clamp() and
* mozilla::clamped() since they both assert max >= min.
* @note If aMinValue and aMaxValue are computed min block-size and max
* block-size, it is simpler to use ReflowInput::ApplyMinMaxBSize().
* Similarly, there is ReflowInput::ApplyMinMaxISize() for clamping an
* inline-size.
template <class NumericType>
NumericType NS_CSS_MINMAX(NumericType aValue, NumericType aMinValue,
NumericType aMaxValue) {
NumericType result = aValue;
if (aMaxValue < result) result = aMaxValue;
if (aMinValue > result) result = aMinValue;
return result;
namespace mozilla {
// A base class of ReflowInput that computes only the padding,
// border, and margin, since those values are needed more often.
struct SizeComputationInput {
// The frame being reflowed.
nsIFrame* const mFrame;
// Rendering context to use for measurement.
gfxContext* mRenderingContext;
nsMargin ComputedPhysicalMargin() const {
return mComputedMargin.GetPhysicalMargin(mWritingMode);
nsMargin ComputedPhysicalBorderPadding() const {
return mComputedBorderPadding.GetPhysicalMargin(mWritingMode);
nsMargin ComputedPhysicalBorder() const {
return ComputedLogicalBorder(mWritingMode).GetPhysicalMargin(mWritingMode);
nsMargin ComputedPhysicalPadding() const {
return mComputedPadding.GetPhysicalMargin(mWritingMode);
mozilla::LogicalMargin ComputedLogicalMargin(mozilla::WritingMode aWM) const {
return mComputedMargin.ConvertTo(aWM, mWritingMode);
mozilla::LogicalMargin ComputedLogicalBorderPadding(
mozilla::WritingMode aWM) const {
return mComputedBorderPadding.ConvertTo(aWM, mWritingMode);
mozilla::LogicalMargin ComputedLogicalPadding(
mozilla::WritingMode aWM) const {
return mComputedPadding.ConvertTo(aWM, mWritingMode);
mozilla::LogicalMargin ComputedLogicalBorder(mozilla::WritingMode aWM) const {
return (mComputedBorderPadding - mComputedPadding)
.ConvertTo(aWM, mWritingMode);
void SetComputedLogicalMargin(mozilla::WritingMode aWM,
const mozilla::LogicalMargin& aMargin) {
mComputedMargin = aMargin.ConvertTo(mWritingMode, aWM);
void SetComputedLogicalBorderPadding(
mozilla::WritingMode aWM, const mozilla::LogicalMargin& aBorderPadding) {
mComputedBorderPadding = aBorderPadding.ConvertTo(mWritingMode, aWM);
void SetComputedLogicalPadding(mozilla::WritingMode aWM,
const mozilla::LogicalMargin& aPadding) {
mComputedPadding = aPadding.ConvertTo(mWritingMode, aWM);
mozilla::WritingMode GetWritingMode() const { return mWritingMode; }
// cached copy of the frame's writing-mode, for logical coordinates
const mozilla::WritingMode mWritingMode;
// Cached mFrame->IsThemed().
const bool mIsThemed = false;
// Computed margin values
mozilla::LogicalMargin mComputedMargin;
// Cached copy of the border + padding values
mozilla::LogicalMargin mComputedBorderPadding;
// Computed padding values
mozilla::LogicalMargin mComputedPadding;
// Callers using this constructor must call InitOffsets on their own.
SizeComputationInput(nsIFrame* aFrame, gfxContext* aRenderingContext);
SizeComputationInput(nsIFrame* aFrame, gfxContext* aRenderingContext,
mozilla::WritingMode aContainingBlockWritingMode,
nscoord aContainingBlockISize,
const mozilla::Maybe<mozilla::LogicalMargin>& aBorder =
const mozilla::Maybe<mozilla::LogicalMargin>& aPadding =
* Computes margin values from the specified margin style information, and
* fills in the mComputedMargin member.
* @param aCBWM Writing mode of the containing block
* @param aPercentBasis
* Inline size of the containing block (in its own writing mode), to use
* for resolving percentage margin values in the inline and block axes.
* @return true if the margin is dependent on the containing block size.
bool ComputeMargin(mozilla::WritingMode aCBWM, nscoord aPercentBasis,
mozilla::LayoutFrameType aFrameType);
* Computes padding values from the specified padding style information, and
* fills in the mComputedPadding member.
* @param aCBWM Writing mode of the containing block
* @param aPercentBasis
* Inline size of the containing block (in its own writing mode), to use
* for resolving percentage padding values in the inline and block axes.
* @return true if the padding is dependent on the containing block size.
bool ComputePadding(mozilla::WritingMode aCBWM, nscoord aPercentBasis,
mozilla::LayoutFrameType aFrameType);
void InitOffsets(mozilla::WritingMode aCBWM, nscoord aPercentBasis,
mozilla::LayoutFrameType aFrameType,
mozilla::ComputeSizeFlags aFlags,
const mozilla::Maybe<mozilla::LogicalMargin>& aBorder,
const mozilla::Maybe<mozilla::LogicalMargin>& aPadding,
const nsStyleDisplay* aDisplay = nullptr);
* Convert StyleSize or StyleMaxSize to nscoord when percentages depend on the
* inline size of the containing block, and enumerated values are for inline
* size, min-inline-size, or max-inline-size. Does not handle auto inline
* sizes.
template <typename SizeOrMaxSize>
inline nscoord ComputeISizeValue(const WritingMode aWM,
const LogicalSize& aContainingBlockSize,
const LogicalSize& aContentEdgeToBoxSizing,
nscoord aBoxSizingToMarginEdge,
const SizeOrMaxSize&) const;
// same as previous, but using mComputedBorderPadding, mComputedPadding,
// and mComputedMargin
template <typename SizeOrMaxSize>
inline nscoord ComputeISizeValue(const LogicalSize& aContainingBlockSize,
mozilla::StyleBoxSizing aBoxSizing,
const SizeOrMaxSize&) const;
nscoord ComputeBSizeValue(nscoord aContainingBlockBSize,
mozilla::StyleBoxSizing aBoxSizing,
const mozilla::LengthPercentage& aCoord) const;
* State passed to a frame during reflow or intrinsic size calculation.
* XXX Refactor so only a base class (nsSizingState?) is used for intrinsic
* size calculation.
* @see nsIFrame#Reflow()
struct ReflowInput : public SizeComputationInput {
// the reflow inputs are linked together. this is the pointer to the
// parent's reflow input
const ReflowInput* mParentReflowInput = nullptr;
// A non-owning pointer to the float manager associated with this area,
// which points to the object owned by nsAutoFloatManager::mNew.
nsFloatManager* mFloatManager = nullptr;
// LineLayout object (only for inline reflow; set to nullptr otherwise)
nsLineLayout* mLineLayout = nullptr;
// The appropriate reflow input for the containing block (for
// percentage widths, etc.) of this reflow input's frame. It will be setup
// properly in InitCBReflowInput().
const ReflowInput* mCBReflowInput = nullptr;
// The amount the in-flow position of the block is moving vertically relative
// to its previous in-flow position (i.e. the amount the line containing the
// block is moving).
// This should be zero for anything which is not a block outside, and it
// should be zero for anything which has a non-block parent.
// The intended use of this value is to allow the accurate determination
// of the potential impact of a float
// This takes on an arbitrary value the first time a block is reflowed
nscoord mBlockDelta = 0;
// If a ReflowInput finds itself initialized with an unconstrained
// inline-size, it will look up its parentReflowInput chain for a reflow input
// with an orthogonal writing mode and a non-NS_UNCONSTRAINEDSIZE value for
// orthogonal limit; when it finds such a reflow input, it will use its
// orthogonal-limit value to constrain inline-size.
// This is initialized to NS_UNCONSTRAINEDSIZE (so it will be ignored),
// but reset to a suitable value for the reflow root by PresShell.
nscoord mOrthogonalLimit = NS_UNCONSTRAINEDSIZE;
// Physical accessors for the private fields. They are needed for
// compatibility with not-yet-updated code. New code should use the accessors
// for logical coordinates, unless the code really works on physical
// coordinates.
nscoord AvailableWidth() const { return mAvailableSize.Width(mWritingMode); }
nscoord AvailableHeight() const {
return mAvailableSize.Height(mWritingMode);
nscoord ComputedWidth() const { return mComputedSize.Width(mWritingMode); }
nscoord ComputedHeight() const { return mComputedSize.Height(mWritingMode); }
nscoord ComputedMinWidth() const {
return mComputedMinSize.Width(mWritingMode);
nscoord ComputedMaxWidth() const {
return mComputedMaxSize.Width(mWritingMode);
nscoord ComputedMinHeight() const {
return mComputedMinSize.Height(mWritingMode);
nscoord ComputedMaxHeight() const {
return mComputedMaxSize.Height(mWritingMode);
// Logical accessors for private fields in mWritingMode.
nscoord AvailableISize() const { return mAvailableSize.ISize(mWritingMode); }
nscoord AvailableBSize() const { return mAvailableSize.BSize(mWritingMode); }
nscoord ComputedISize() const { return mComputedSize.ISize(mWritingMode); }
nscoord ComputedBSize() const { return mComputedSize.BSize(mWritingMode); }
nscoord ComputedMinISize() const {
return mComputedMinSize.ISize(mWritingMode);
nscoord ComputedMaxISize() const {
return mComputedMaxSize.ISize(mWritingMode);
nscoord ComputedMinBSize() const {
return mComputedMinSize.BSize(mWritingMode);
nscoord ComputedMaxBSize() const {
return mComputedMaxSize.BSize(mWritingMode);
// WARNING: In general, adjusting available inline-size or block-size is not
// safe because ReflowInput has members whose values depend on the available
// size passing through the constructor. For example,
// CalculateBlockSideMargins() is called during initialization, and uses
// AvailableSize(). Make sure your use case doesn't lead to stale member
// values in ReflowInput!
void SetAvailableISize(nscoord aAvailableISize) {
mAvailableSize.ISize(mWritingMode) = aAvailableISize;
void SetAvailableBSize(nscoord aAvailableBSize) {
mAvailableSize.BSize(mWritingMode) = aAvailableBSize;
void SetComputedMinISize(nscoord aMinISize) {
mComputedMinSize.ISize(mWritingMode) = aMinISize;
void SetComputedMaxISize(nscoord aMaxISize) {
mComputedMaxSize.ISize(mWritingMode) = aMaxISize;
void SetComputedMinBSize(nscoord aMinBSize) {
mComputedMinSize.BSize(mWritingMode) = aMinBSize;
void SetComputedMaxBSize(nscoord aMaxBSize) {
mComputedMaxSize.BSize(mWritingMode) = aMaxBSize;
void SetPercentageBasisInBlockAxis(nscoord aBSize) {
mPercentageBasisInBlockAxis = Some(aBSize);
mozilla::LogicalSize AvailableSize() const { return mAvailableSize; }
mozilla::LogicalSize ComputedSize() const { return mComputedSize; }
template <typename F>
mozilla::LogicalSize ComputedSizeWithBSizeFallback(F&& aFallback) const {
auto size = mComputedSize;
if (size.BSize(mWritingMode) == NS_UNCONSTRAINEDSIZE) {
size.BSize(mWritingMode) = ApplyMinMaxBSize(aFallback());
return size;
mozilla::LogicalSize ComputedMinSize() const { return mComputedMinSize; }
mozilla::LogicalSize ComputedMaxSize() const { return mComputedMaxSize; }
mozilla::LogicalSize AvailableSize(mozilla::WritingMode aWM) const {
return AvailableSize().ConvertTo(aWM, mWritingMode);
mozilla::LogicalSize ComputedSize(mozilla::WritingMode aWM) const {
return ComputedSize().ConvertTo(aWM, mWritingMode);
mozilla::LogicalSize ComputedMinSize(mozilla::WritingMode aWM) const {
return ComputedMinSize().ConvertTo(aWM, mWritingMode);
mozilla::LogicalSize ComputedMaxSize(mozilla::WritingMode aWM) const {
return ComputedMaxSize().ConvertTo(aWM, mWritingMode);
mozilla::LogicalSize ComputedSizeWithPadding(mozilla::WritingMode aWM) const {
return ComputedSize(aWM) + ComputedLogicalPadding(aWM).Size(aWM);
mozilla::LogicalSize ComputedSizeWithBorderPadding(
mozilla::WritingMode aWM) const {
return ComputedSize(aWM) + ComputedLogicalBorderPadding(aWM).Size(aWM);
mozilla::LogicalSize ComputedSizeWithMarginBorderPadding(
mozilla::WritingMode aWM) const {
return ComputedSizeWithBorderPadding(aWM) +
nsSize ComputedPhysicalSize() const {
return mComputedSize.GetPhysicalSize(mWritingMode);
nsMargin ComputedPhysicalOffsets() const {
return mComputedOffsets.GetPhysicalMargin(mWritingMode);
LogicalMargin ComputedLogicalOffsets(mozilla::WritingMode aWM) const {
return mComputedOffsets.ConvertTo(aWM, mWritingMode);
void SetComputedLogicalOffsets(mozilla::WritingMode aWM,
const LogicalMargin& aOffsets) {
mComputedOffsets = aOffsets.ConvertTo(mWritingMode, aWM);
// Return ReflowInput's computed size including border-padding, with
// unconstrained dimensions replaced by zero.
nsSize ComputedSizeAsContainerIfConstrained() const;
// Our saved containing block dimensions.
LogicalSize mContainingBlockSize{mWritingMode};
// Cached pointers to the various style structs used during initialization.
const nsStyleDisplay* mStyleDisplay = nullptr;
const nsStylePosition* mStylePosition = nullptr;
const nsStyleBorder* mStyleBorder = nullptr;
const nsStyleMargin* mStyleMargin = nullptr;
enum class BreakType : uint8_t {
BreakType mBreakType = BreakType::Auto;
// a frame (e.g. nsTableCellFrame) which may need to generate a special
// reflow for percent bsize calculations
nsIPercentBSizeObserver* mPercentBSizeObserver = nullptr;
// CSS margin collapsing sometimes requires us to reflow
// optimistically assuming that margins collapse to see if clearance
// is required. When we discover that clearance is required, we
// store the frame in which clearance was discovered to the location
// requested here.
nsIFrame** mDiscoveredClearance = nullptr;
struct Flags {
Flags() { memset(this, 0, sizeof(*this)); }
// cached mFrame->IsReplaced() || mFrame->IsReplacedWithBlock()
bool mIsReplaced : 1;
// used by tables to communicate special reflow (in process) to handle
// percent bsize frames inside cells which may not have computed bsizes
bool mSpecialBSizeReflow : 1;
// nothing in the frame's next-in-flow (or its descendants) is changing
bool mNextInFlowUntouched : 1;
// Is the current context at the top of a page? When true, we force
// something that's too tall for a page/column to fit anyway to avoid
// infinite loops.
bool mIsTopOfPage : 1;
// parent frame is an nsIScrollableFrame and it is assuming a horizontal
// scrollbar
bool mAssumingHScrollbar : 1;
// parent frame is an nsIScrollableFrame and it is assuming a vertical
// scrollbar
bool mAssumingVScrollbar : 1;
// Is frame a different inline-size than before?
bool mIsIResize : 1;
// Is frame (potentially) a different block-size than before?
// This includes cases where the block-size is 'auto' and the
// contents or width have changed.
bool mIsBResize : 1;
// Has this frame changed block-size in a way that affects
// block-size percentages on frames for which it is the containing
// block? This includes a change between 'auto' and a length that
// doesn't actually change the frame's block-size. It does not
// include cases where the block-size is 'auto' and the frame's
// contents have changed.
// In the current code, this is only true when mIsBResize is also
// true, although it doesn't necessarily need to be that way (e.g.,
// in the case of a frame changing from 'auto' to a length that
// produces the same height).
bool mIsBResizeForPercentages : 1;
// tables are splittable, this should happen only inside a page and never
// insider a column frame
bool mTableIsSplittable : 1;
// Does frame height depend on an ancestor table-cell?
bool mHeightDependsOnAncestorCell : 1;
// nsColumnSetFrame is balancing columns
bool mIsColumnBalancing : 1;
// We have an ancestor nsColumnSetFrame performing the last column balancing
// reflow. The available block-size of the last column might become
// unconstrained.
bool mIsInLastColumnBalancingReflow : 1;
// True if ColumnSetWrapperFrame has a constrained block-size, and is going
// to consume all of its block-size in this fragment. This bit is passed to
// nsColumnSetFrame to determine whether to give up balancing and create
// overflow columns.
bool mColumnSetWrapperHasNoBSizeLeft : 1;
// If this flag is set, the BSize of this frame should be considered
// indefinite for the purposes of percent resolution on child frames (we
// should behave as if ComputedBSize() were NS_UNCONSTRAINEDSIZE when doing
// percent resolution against this.ComputedBSize()). For example: flex
// items may have their ComputedBSize() resolved ahead-of-time by their
// flex container, and yet their BSize might have to be considered
bool mTreatBSizeAsIndefinite : 1;
// a "fake" reflow input made in order to be the parent of a real one
bool mDummyParentReflowInput : 1;
// Should this frame reflow its place-holder children? If the available
// height of this frame didn't change, but its in a paginated environment
// (e.g. columns), it should always reflow its placeholder children.
bool mMustReflowPlaceholders : 1;
// the STATIC_POS_IS_CB_ORIGIN ctor flag
bool mStaticPosIsCBOrigin : 1;
// If set, the following two flags indicate that:
// (1) this frame is absolutely-positioned (or fixed-positioned).
// (2) this frame's static position depends on the CSS Box Alignment.
// (3) we do need to compute the static position, because the frame's
// {Inline and/or Block} offsets actually depend on it.
// When these bits are set, the offset values (IStart/IEnd, BStart/BEnd)
// represent the "start" edge of the frame's CSS Box Alignment container
// area, in that axis -- and these offsets need to be further-resolved
// (with CSS Box Alignment) after we know the OOF frame's size.
// NOTE: The "I" and "B" (for "Inline" and "Block") refer the axes of the
// *containing block's writing-mode*, NOT mFrame's own writing-mode. This
// is purely for convenience, since that's the writing-mode we're dealing
// with when we set & react to these bits.
bool mIOffsetsNeedCSSAlign : 1;
bool mBOffsetsNeedCSSAlign : 1;
// Is this frame or one of its ancestors being reflowed in a different
// continuation than the one in which it was previously reflowed? In
// other words, has it moved to a different column or page than it was in
// the previous reflow?
// FIXME: For now, we only ensure that this is set correctly for blocks.
// This is okay because the only thing that uses it only cares about
// whether there's been a fragment change within the same block formatting
// context.
bool mMovedBlockFragments : 1;
// Is the block-size computed by aspect-ratio and inline size (i.e. block
// axis is the ratio-dependent axis)? We set this flag so that we can check
// whether to apply automatic content-based minimum sizes once we know the
// children's block-size (after reflowing them).
bool mIsBSizeSetByAspectRatio : 1;
// If true, then children of this frame can generate class A breakpoints
// for paginated reflow.
bool mCanHaveClassABreakpoints : 1;
Flags mFlags;
mozilla::StyleSizeOverrides mStyleSizeOverrides;
mozilla::ComputeSizeFlags mComputeSizeFlags;
// This value keeps track of how deeply nested a given reflow input
// is from the top of the frame tree.
int16_t mReflowDepth = 0;
// Logical and physical accessors for the resize flags.
bool IsHResize() const {
return mWritingMode.IsVertical() ? mFlags.mIsBResize : mFlags.mIsIResize;
bool IsVResize() const {
return mWritingMode.IsVertical() ? mFlags.mIsIResize : mFlags.mIsBResize;
bool IsIResize() const { return mFlags.mIsIResize; }
bool IsBResize() const { return mFlags.mIsBResize; }
bool IsBResizeForWM(mozilla::WritingMode aWM) const {
return aWM.IsOrthogonalTo(mWritingMode) ? mFlags.mIsIResize
: mFlags.mIsBResize;
bool IsBResizeForPercentagesForWM(mozilla::WritingMode aWM) const {
// This uses the relatively-accurate mIsBResizeForPercentages flag
// when the writing modes are parallel, and is a bit more
// pessimistic when orthogonal.
return !aWM.IsOrthogonalTo(mWritingMode) ? mFlags.mIsBResizeForPercentages
: IsIResize();
void SetHResize(bool aValue) {
if (mWritingMode.IsVertical()) {
mFlags.mIsBResize = aValue;
} else {
mFlags.mIsIResize = aValue;
void SetVResize(bool aValue) {
if (mWritingMode.IsVertical()) {
mFlags.mIsIResize = aValue;
} else {
mFlags.mIsBResize = aValue;
void SetIResize(bool aValue) { mFlags.mIsIResize = aValue; }
void SetBResize(bool aValue) { mFlags.mIsBResize = aValue; }
// Values for |aFlags| passed to constructor
enum class InitFlag : uint8_t {
// Indicates that the parent of this reflow input is "fake" (see
// mDummyParentReflowInput in mFlags).
// Indicates that the calling function will initialize the reflow input, and
// that the constructor should not call Init().
// The caller wants the abs.pos. static-position resolved at the origin of
// the containing block, i.e. at LogicalPoint(0, 0). (Note that this
// doesn't necessarily mean that (0, 0) is the *correct* static position
// for the frame in question.)
// @note In a Grid container's masonry axis we'll always use
// the placeholder's position in that axis regardless of this flag.
using InitFlags = mozilla::EnumSet<InitFlag>;
// Note: The copy constructor is written by the compiler automatically. You
// can use that and then override specific values if you want, or you can
// call Init as desired...
* Initialize a ROOT reflow input.
* @param aPresContext Must be equal to aFrame->PresContext().
* @param aFrame The frame for whose reflow input is being constructed.
* @param aRenderingContext The rendering context to be used for measurements.
* @param aAvailableSpace The available space to reflow aFrame (in aFrame's
* writing-mode). See comments for mAvailableSize for more information.
* @param aFlags A set of flags used for additional boolean parameters (see
* InitFlags above).
ReflowInput(nsPresContext* aPresContext, nsIFrame* aFrame,
gfxContext* aRenderingContext,
const mozilla::LogicalSize& aAvailableSpace,
InitFlags aFlags = {});
* Initialize a reflow input for a child frame's reflow. Some parts of the
* state are copied from the parent's reflow input. The remainder is computed.
* @param aPresContext Must be equal to aFrame->PresContext().
* @param aParentReflowInput A reference to an ReflowInput object that
* is to be the parent of this object.
* @param aFrame The frame for whose reflow input is being constructed.
* @param aAvailableSpace The available space to reflow aFrame (in aFrame's
* writing-mode). See comments for mAvailableSize for more information.
* @param aContainingBlockSize An optional size (in aFrame's writing mode),
* specifying the containing block size to use instead of the default
* size computed by ComputeContainingBlockRectangle(). If
* InitFlag::CallerWillInit is used, this is ignored. Pass it via
* Init() instead.
* @param aFlags A set of flags used for additional boolean parameters (see
* InitFlags above).
* @param aStyleSizeOverrides The style data used to override mFrame's when we
* call nsIFrame::ComputeSize() internally.
* @param aComputeSizeFlags A set of flags used when we call
* nsIFrame::ComputeSize() internally.
ReflowInput(nsPresContext* aPresContext,
const ReflowInput& aParentReflowInput, nsIFrame* aFrame,
const mozilla::LogicalSize& aAvailableSpace,
const mozilla::Maybe<mozilla::LogicalSize>& aContainingBlockSize =
InitFlags aFlags = {},
const mozilla::StyleSizeOverrides& aSizeOverrides = {},
mozilla::ComputeSizeFlags aComputeSizeFlags = {});
* This method initializes various data members. It is automatically called by
* the constructors if InitFlags::CallerWillInit is *not* used.
* @param aContainingBlockSize An optional size (in mFrame's writing mode),
* specifying the containing block size to use instead of the default
* size computed by ComputeContainingBlockRectangle().
* @param aBorder An optional border (in mFrame's writing mode). If given, use
* it instead of the border computed from mFrame's StyleBorder.
* @param aPadding An optional padding (in mFrame's writing mode). If given,
* use it instead of the padding computing from mFrame's StylePadding.
void Init(nsPresContext* aPresContext,
const mozilla::Maybe<mozilla::LogicalSize>& aContainingBlockSize =
const mozilla::Maybe<mozilla::LogicalMargin>& aBorder =
const mozilla::Maybe<mozilla::LogicalMargin>& aPadding =
* Get the used line-height property. The return value will be >= 0.
nscoord GetLineHeight() const;
* Set the used line-height. aLineHeight must be >= 0.
void SetLineHeight(nscoord aLineHeight);
* Calculate the used line-height property without a reflow input instance.
* The return value will be >= 0.
* @param aBlockBSize The computed block size of the content rect of the block
* that the line should fill. Only used with
* line-height:-moz-block-height. NS_UNCONSTRAINEDSIZE
* results in a normal line-height for
* line-height:-moz-block-height.
* @param aFontSizeInflation The result of the appropriate
* nsLayoutUtils::FontSizeInflationFor call,
* or 1.0 if during intrinsic size
* calculation.
static nscoord CalcLineHeight(const ComputedStyle&,
nsPresContext* aPresContext,
const nsIContent* aContent, nscoord aBlockBSize,
float aFontSizeInflation);
static nscoord CalcLineHeight(const StyleLineHeight&,
const nsStyleFont& aRelativeToFont,
nsPresContext* aPresContext, bool aIsVertical,
const nsIContent* aContent, nscoord aBlockBSize,
float aFontSizeInflation);
mozilla::LogicalSize ComputeContainingBlockRectangle(
nsPresContext* aPresContext, const ReflowInput* aContainingBlockRI) const;
* Apply the mComputed(Min/Max)ISize constraints to the content
* size computed so far.
nscoord ApplyMinMaxISize(nscoord aISize) const {
if (NS_UNCONSTRAINEDSIZE != ComputedMaxISize()) {
aISize = std::min(aISize, ComputedMaxISize());
return std::max(aISize, ComputedMinISize());
* Apply the mComputed(Min/Max)BSize constraints to the content
* size computed so far.
* @param aBSize The block-size that we've computed an to which we want to
* apply min/max constraints.
* @param aConsumed The amount of the computed block-size that was consumed by
* our prev-in-flows.
nscoord ApplyMinMaxBSize(nscoord aBSize, nscoord aConsumed = 0) const {
aBSize += aConsumed;
if (NS_UNCONSTRAINEDSIZE != ComputedMaxBSize()) {
aBSize = std::min(aBSize, ComputedMaxBSize());
if (NS_UNCONSTRAINEDSIZE != ComputedMinBSize()) {
aBSize = std::max(aBSize, ComputedMinBSize());
return aBSize - aConsumed;
bool ShouldReflowAllKids() const;
// This method doesn't apply min/max computed widths to the value passed in.
void SetComputedWidth(nscoord aComputedWidth) {
if (mWritingMode.IsVertical()) {
} else {
// This method doesn't apply min/max computed heights to the value passed in.
void SetComputedHeight(nscoord aComputedHeight) {
if (mWritingMode.IsVertical()) {
} else {
// Use "No" to request SetComputedISize/SetComputedBSize not to reset resize
// flags.
enum class ResetResizeFlags : bool { No, Yes };
// This method doesn't apply min/max computed inline-sizes to the value passed
// in.
void SetComputedISize(nscoord aComputedISize,
ResetResizeFlags aFlags = ResetResizeFlags::Yes);
// These methods don't apply min/max computed block-sizes to the value passed
// in.
void SetComputedBSize(nscoord aComputedBSize,
ResetResizeFlags aFlags = ResetResizeFlags::Yes);
bool WillReflowAgainForClearance() const {
return mDiscoveredClearance && *mDiscoveredClearance;
// Returns true if we should apply automatic minimum on the block axis.
// The automatic minimum size in the ratio-dependent axis of a box with a
// preferred aspect ratio that is neither a replaced element nor a scroll
// container is its min-content size clamped from above by its maximum size.
bool ShouldApplyAutomaticMinimumOnBlockAxis() const;
// Returns true if mFrame has a constrained available block-size, or if mFrame
// is a continuation. When this method returns true, mFrame can be considered
// to be in a "fragmented context."
// Note: this method usually returns true when mFrame is in a paged
// environment (e.g. printing) or has a multi-column container ancestor.
// However, this doesn't include several cases when we're intentionally
// performing layout in a fragmentation-ignoring way, e.g. 1) mFrame is a flex
// or grid item, and this ReflowInput is for a measuring reflow with an
// unconstrained available block-size, or 2) mFrame is (or is inside of) an
// element that forms an orthogonal writing-mode.
bool IsInFragmentedContext() const;
// Compute the offsets for a relative position element
// @param aWM the writing mode of aCBSize and the returned offsets.
static mozilla::LogicalMargin ComputeRelativeOffsets(
mozilla::WritingMode aWM, nsIFrame* aFrame,
const mozilla::LogicalSize& aCBSize);
// If aFrame is a relatively or sticky positioned element, adjust aPosition
// appropriately.
// @param aComputedOffsets aFrame's relative offset, either from the cached
// nsIFrame::ComputedOffsetProperty() or ComputedPhysicalOffsets().
// Note: This parameter is used only when aFrame is relatively
// positioned, not sticky positioned.
// @param aPosition [in/out] Pass aFrame's normal position (pre-relative
// positioning), and this method will update it to indicate aFrame's
// actual position.
static void ApplyRelativePositioning(nsIFrame* aFrame,
const nsMargin& aComputedOffsets,
nsPoint* aPosition);
static void ApplyRelativePositioning(
nsIFrame* aFrame, mozilla::WritingMode aWritingMode,
const mozilla::LogicalMargin& aComputedOffsets,
mozilla::LogicalPoint* aPosition, const nsSize& aContainerSize);
// Resolve any block-axis 'auto' margins (if any) for an absolutely positioned
// frame. aMargin and aOffsets are both outparams (though we only touch
// aOffsets if the position is overconstrained)
static void ComputeAbsPosBlockAutoMargin(nscoord aAvailMarginSpace,
WritingMode aContainingBlockWM,
bool aIsMarginBStartAuto,
bool aIsMarginBEndAuto,
LogicalMargin& aMargin,
LogicalMargin& aOffsets);
// Resolve any inline-axis 'auto' margins (if any) for an absolutely
// positioned frame. aMargin and aOffsets are both outparams (though we only
// touch aOffsets if the position is overconstrained)
static void ComputeAbsPosInlineAutoMargin(nscoord aAvailMarginSpace,
WritingMode aContainingBlockWM,
bool aIsMarginIStartAuto,
bool aIsMarginIEndAuto,
LogicalMargin& aMargin,
LogicalMargin& aOffsets);
void InitCBReflowInput();
void InitResizeFlags(nsPresContext* aPresContext,
mozilla::LayoutFrameType aFrameType);
void InitDynamicReflowRoot();
void InitConstraints(
nsPresContext* aPresContext,
const mozilla::Maybe<mozilla::LogicalSize>& aContainingBlockSize,
const mozilla::Maybe<mozilla::LogicalMargin>& aBorder,
const mozilla::Maybe<mozilla::LogicalMargin>& aPadding,
mozilla::LayoutFrameType aFrameType);
// Returns the nearest containing block or block frame (whether or not
// it is a containing block) for the specified frame. Also returns
// the inline-start edge and logical size of the containing block's
// content area.
// These are returned in the coordinate space of the containing block.
nsIFrame* GetHypotheticalBoxContainer(nsIFrame* aFrame,
nscoord& aCBIStartEdge,
mozilla::LogicalSize& aCBSize) const;
// Calculate a "hypothetical box" position where the placeholder frame
// (for a position:fixed/absolute element) would have been placed if it were
// positioned statically. The hypothetical box position will have a writing
// mode with the same block direction as the absolute containing block
// (aCBReflowInput->frame), though it may differ in inline direction.
void CalculateHypotheticalPosition(nsPresContext* aPresContext,
nsPlaceholderFrame* aPlaceholderFrame,
const ReflowInput* aCBReflowInput,
nsHypotheticalPosition& aHypotheticalPos,
mozilla::LayoutFrameType aFrameType) const;
// Check if we can use the resolved auto block size (by insets) to compute
// the inline size through aspect-ratio on absolute-positioned elements.
// This is only needed for non-replaced elements.
bool IsInlineSizeComputableByBlockSizeAndAspectRatio(
nscoord aBlockSize) const;
// This calculates the size by using the resolved auto block size (from
// non-auto block insets), according to the writing mode of current block.
LogicalSize CalculateAbsoluteSizeWithResolvedAutoBlockSize(
nscoord aAutoBSize, const LogicalSize& aTentativeComputedSize);
void InitAbsoluteConstraints(nsPresContext* aPresContext,
const ReflowInput* aCBReflowInput,
const mozilla::LogicalSize& aContainingBlockSize,
mozilla::LayoutFrameType aFrameType);
// Calculates the computed values for the 'min-inline-size',
// 'max-inline-size', 'min-block-size', and 'max-block-size' properties, and
// stores them in the assorted data members
void ComputeMinMaxValues(const mozilla::LogicalSize& aCBSize);
// aInsideBoxSizing returns the part of the padding, border, and margin
// in the aAxis dimension that goes inside the edge given by box-sizing;
// aOutsideBoxSizing returns the rest.
void CalculateBorderPaddingMargin(mozilla::LogicalAxis aAxis,
nscoord aContainingBlockSize,
nscoord* aInsideBoxSizing,
nscoord* aOutsideBoxSizing) const;
void CalculateBlockSideMargins();
* @return true if mFrame is an internal table frame, i.e. an
* ns[RowGroup|ColGroup|Row|Cell]Frame. (We exclude nsTableColFrame
* here since we never setup a ReflowInput for those.)
bool IsInternalTableFrame() const;
// The available size in which to reflow the frame. The space represents the
// amount of room for the frame's margin, border, padding, and content area.
// The available inline-size should be constrained. The frame's inline-size
// you choose should fit within it.
// In galley mode, the available block-size is always unconstrained, and only
// page mode or multi-column layout involves a constrained available
// block-size.
// An unconstrained available block-size means you can choose whatever size
// you want. If the value is constrained, the frame's block-start border,
// padding, and content, must fit. If a frame is fully-complete after reflow,
// then its block-end border, padding, and margin (and similar for its
// fully-complete ancestors) will need to fit within this available
// block-size. However, if a frame is monolithic, it may choose a block-size
// larger than the available block-size.
mozilla::LogicalSize mAvailableSize{mWritingMode};
// The computed size specifies the frame's content area, and it does not apply
// to inline non-replaced elements.
// For block-level frames, the computed inline-size is based on the
// inline-size of the containing block, the margin/border/padding areas, and
// the min/max inline-size.
// For non-replaced block-level frames in the flow and floated, if the
// computed block-size is NS_UNCONSTRAINEDSIZE, you should choose a block-size
// to shrink wrap around the normal flow child frames. The block-size must be
// within the limit of the min/max block-size if there is such a limit.
mozilla::LogicalSize mComputedSize{mWritingMode};
// Computed values for 'inset' properties. Only applies to 'positioned'
// elements.
mozilla::LogicalMargin mComputedOffsets{mWritingMode};
// Computed value for 'min-inline-size'/'min-block-size'.
mozilla::LogicalSize mComputedMinSize{mWritingMode};
// Computed value for 'max-inline-size'/'max-block-size'.
mozilla::LogicalSize mComputedMaxSize{mWritingMode, NS_UNCONSTRAINEDSIZE,
// Percentage basis in the block axis for the purpose of percentage resolution
// on children.
// This will be ignored when mTreatBSizeAsIndefinite flag is true, or when a
// customized containing block size is provided via ReflowInput's constructor
// or Init(). When this percentage basis exists, it will be used to replace
// the containing block's ComputedBSize() in
// ComputeContainingBlockRectangle().
// This is currently used in a special scenario where we treat certain
// sized-to-content flex items as having an 'auto' block-size for their final
// reflow to accomodate fragmentation-imposed block-size growth. This sort of
// flex item does nonetheless have a known block-size (from the flex layout
// algorithm) that it needs to use as a definite percentage-basis for its
// children during its final reflow; and we represent that here.
Maybe<nscoord> mPercentageBasisInBlockAxis;
// Cache the used line-height property.
mutable nscoord mLineHeight = NS_UNCONSTRAINEDSIZE;
} // namespace mozilla
#endif // mozilla_ReflowInput_h