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fune/layout/generic/nsFlexContainerFrame.cpp
Ting-Yu Lin f66247db06 Bug 1792750 Part 1 - Remove an obsolete comment for FlexLine::LastBaselineOffset(). r=dholbert 
We've removed the ability to reverse flex container's axes internally in
bug 1639053.

Differential Revision: https://phabricator.services.mozilla.com/D181602
2023-06-23 00:39:46 +00:00

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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 http://mozilla.org/MPL/2.0/. */
/* rendering object for CSS "display: flex" */
#include "nsFlexContainerFrame.h"
#include <algorithm>
#include "gfxContext.h"
#include "mozilla/Baseline.h"
#include "mozilla/ComputedStyle.h"
#include "mozilla/CSSOrderAwareFrameIterator.h"
#include "mozilla/FloatingPoint.h"
#include "mozilla/Logging.h"
#include "mozilla/PresShell.h"
#include "mozilla/StaticPrefs_layout.h"
#include "mozilla/WritingModes.h"
#include "nsBlockFrame.h"
#include "nsContentUtils.h"
#include "nsCSSAnonBoxes.h"
#include "nsDebug.h"
#include "nsDisplayList.h"
#include "nsFieldSetFrame.h"
#include "nsIFrameInlines.h"
#include "nsLayoutUtils.h"
#include "nsPlaceholderFrame.h"
#include "nsPresContext.h"
using namespace mozilla;
using namespace mozilla::layout;
// Convenience typedefs for helper classes that we forward-declare in .h file
// (so that nsFlexContainerFrame methods can use them as parameters):
using FlexItem = nsFlexContainerFrame::FlexItem;
using FlexLine = nsFlexContainerFrame::FlexLine;
using FlexboxAxisTracker = nsFlexContainerFrame::FlexboxAxisTracker;
using StrutInfo = nsFlexContainerFrame::StrutInfo;
using CachedBAxisMeasurement = nsFlexContainerFrame::CachedBAxisMeasurement;
static mozilla::LazyLogModule gFlexContainerLog("FlexContainer");
#define FLEX_LOG(...) \
MOZ_LOG(gFlexContainerLog, LogLevel::Debug, (__VA_ARGS__));
#define FLEX_LOGV(...) \
MOZ_LOG(gFlexContainerLog, LogLevel::Verbose, (__VA_ARGS__));
// Returns true if aFlexContainer is a frame for some element that has
// display:-webkit-{inline-}box (or -moz-{inline-}box). aFlexContainer is
// expected to be an instance of nsFlexContainerFrame (enforced with an assert);
// otherwise, this function's state-bit-check here is bogus.
static bool IsLegacyBox(const nsIFrame* aFlexContainer) {
MOZ_ASSERT(aFlexContainer->IsFlexContainerFrame(),
"only flex containers may be passed to this function");
return aFlexContainer->HasAnyStateBits(
NS_STATE_FLEX_IS_EMULATING_LEGACY_WEBKIT_BOX);
}
// Returns the OrderState enum we should pass to CSSOrderAwareFrameIterator
// (depending on whether aFlexContainer has
// NS_STATE_FLEX_NORMAL_FLOW_CHILDREN_IN_CSS_ORDER state bit).
static CSSOrderAwareFrameIterator::OrderState OrderStateForIter(
const nsFlexContainerFrame* aFlexContainer) {
return aFlexContainer->HasAnyStateBits(
NS_STATE_FLEX_NORMAL_FLOW_CHILDREN_IN_CSS_ORDER)
? CSSOrderAwareFrameIterator::OrderState::Ordered
: CSSOrderAwareFrameIterator::OrderState::Unordered;
}
// Returns the OrderingProperty enum that we should pass to
// CSSOrderAwareFrameIterator (depending on whether it's a legacy box).
static CSSOrderAwareFrameIterator::OrderingProperty OrderingPropertyForIter(
const nsFlexContainerFrame* aFlexContainer) {
return IsLegacyBox(aFlexContainer)
? CSSOrderAwareFrameIterator::OrderingProperty::BoxOrdinalGroup
: CSSOrderAwareFrameIterator::OrderingProperty::Order;
}
// Returns the "align-items" value that's equivalent to the legacy "box-align"
// value in the given style struct.
static StyleAlignFlags ConvertLegacyStyleToAlignItems(
const nsStyleXUL* aStyleXUL) {
// -[moz|webkit]-box-align corresponds to modern "align-items"
switch (aStyleXUL->mBoxAlign) {
case StyleBoxAlign::Stretch:
return StyleAlignFlags::STRETCH;
case StyleBoxAlign::Start:
return StyleAlignFlags::FLEX_START;
case StyleBoxAlign::Center:
return StyleAlignFlags::CENTER;
case StyleBoxAlign::Baseline:
return StyleAlignFlags::BASELINE;
case StyleBoxAlign::End:
return StyleAlignFlags::FLEX_END;
}
MOZ_ASSERT_UNREACHABLE("Unrecognized mBoxAlign enum value");
// Fall back to default value of "align-items" property:
return StyleAlignFlags::STRETCH;
}
// Returns the "justify-content" value that's equivalent to the legacy
// "box-pack" value in the given style struct.
static StyleContentDistribution ConvertLegacyStyleToJustifyContent(
const nsStyleXUL* aStyleXUL) {
// -[moz|webkit]-box-pack corresponds to modern "justify-content"
switch (aStyleXUL->mBoxPack) {
case StyleBoxPack::Start:
return {StyleAlignFlags::FLEX_START};
case StyleBoxPack::Center:
return {StyleAlignFlags::CENTER};
case StyleBoxPack::End:
return {StyleAlignFlags::FLEX_END};
case StyleBoxPack::Justify:
return {StyleAlignFlags::SPACE_BETWEEN};
}
MOZ_ASSERT_UNREACHABLE("Unrecognized mBoxPack enum value");
// Fall back to default value of "justify-content" property:
return {StyleAlignFlags::FLEX_START};
}
/**
* Converts a "flex-relative" coordinate in a single axis (a main- or cross-axis
* coordinate) into a coordinate in the corresponding physical (x or y) axis. If
* the flex-relative axis in question already maps *directly* to a physical
* axis (i.e. if it's LTR or TTB), then the physical coordinate has the same
* numeric value as the provided flex-relative coordinate. Otherwise, we have to
* subtract the flex-relative coordinate from the flex container's size in that
* axis, to flip the polarity. (So e.g. a main-axis position of 2px in a RTL
* 20px-wide container would correspond to a physical coordinate (x-value) of
* 18px.)
*/
static nscoord PhysicalCoordFromFlexRelativeCoord(nscoord aFlexRelativeCoord,
nscoord aContainerSize,
mozilla::Side aStartSide) {
if (aStartSide == eSideLeft || aStartSide == eSideTop) {
return aFlexRelativeCoord;
}
return aContainerSize - aFlexRelativeCoord;
}
// Check if the size is auto or it is a keyword in the block axis.
// |aIsInline| should represent whether aSize is in the inline axis, from the
// perspective of the writing mode of the flex item that the size comes from.
//
// max-content and min-content should behave as property's initial value.
// Bug 567039: We treat -moz-fit-content and -moz-available as property's
// initial value for now.
static inline bool IsAutoOrEnumOnBSize(const StyleSize& aSize, bool aIsInline) {
return aSize.IsAuto() || (!aIsInline && !aSize.IsLengthPercentage());
}
// Encapsulates our flex container's main & cross axes. This class is backed by
// a FlexboxAxisInfo helper member variable, and it adds some convenience APIs
// on top of what that struct offers.
class MOZ_STACK_CLASS nsFlexContainerFrame::FlexboxAxisTracker {
public:
explicit FlexboxAxisTracker(const nsFlexContainerFrame* aFlexContainer);
// Accessors:
LogicalAxis MainAxis() const {
return IsRowOriented() ? eLogicalAxisInline : eLogicalAxisBlock;
}
LogicalAxis CrossAxis() const {
return IsRowOriented() ? eLogicalAxisBlock : eLogicalAxisInline;
}
LogicalSide MainAxisStartSide() const;
LogicalSide MainAxisEndSide() const {
return GetOppositeSide(MainAxisStartSide());
}
LogicalSide CrossAxisStartSide() const;
LogicalSide CrossAxisEndSide() const {
return GetOppositeSide(CrossAxisStartSide());
}
mozilla::Side MainAxisPhysicalStartSide() const {
return mWM.PhysicalSide(MainAxisStartSide());
}
mozilla::Side MainAxisPhysicalEndSide() const {
return mWM.PhysicalSide(MainAxisEndSide());
}
mozilla::Side CrossAxisPhysicalStartSide() const {
return mWM.PhysicalSide(CrossAxisStartSide());
}
mozilla::Side CrossAxisPhysicalEndSide() const {
return mWM.PhysicalSide(CrossAxisEndSide());
}
// Returns the flex container's writing mode.
WritingMode GetWritingMode() const { return mWM; }
// Returns true if our main axis is in the reverse direction of our
// writing mode's corresponding axis. (From 'flex-direction: *-reverse')
bool IsMainAxisReversed() const { return mAxisInfo.mIsMainAxisReversed; }
// Returns true if our cross axis is in the reverse direction of our
// writing mode's corresponding axis. (From 'flex-wrap: *-reverse')
bool IsCrossAxisReversed() const { return mAxisInfo.mIsCrossAxisReversed; }
bool IsRowOriented() const { return mAxisInfo.mIsRowOriented; }
bool IsColumnOriented() const { return !IsRowOriented(); }
// aSize is expected to match the flex container's WritingMode.
nscoord MainComponent(const LogicalSize& aSize) const {
return IsRowOriented() ? aSize.ISize(mWM) : aSize.BSize(mWM);
}
int32_t MainComponent(const LayoutDeviceIntSize& aIntSize) const {
return IsMainAxisHorizontal() ? aIntSize.width : aIntSize.height;
}
// aSize is expected to match the flex container's WritingMode.
nscoord CrossComponent(const LogicalSize& aSize) const {
return IsRowOriented() ? aSize.BSize(mWM) : aSize.ISize(mWM);
}
int32_t CrossComponent(const LayoutDeviceIntSize& aIntSize) const {
return IsMainAxisHorizontal() ? aIntSize.height : aIntSize.width;
}
// NOTE: aMargin is expected to use the flex container's WritingMode.
nscoord MarginSizeInMainAxis(const LogicalMargin& aMargin) const {
// If we're row-oriented, our main axis is the inline axis.
return IsRowOriented() ? aMargin.IStartEnd(mWM) : aMargin.BStartEnd(mWM);
}
nscoord MarginSizeInCrossAxis(const LogicalMargin& aMargin) const {
// If we're row-oriented, our cross axis is the block axis.
return IsRowOriented() ? aMargin.BStartEnd(mWM) : aMargin.IStartEnd(mWM);
}
/**
* Converts a "flex-relative" point (a main-axis & cross-axis coordinate)
* into a LogicalPoint, using the flex container's writing mode.
*
* @arg aMainCoord The main-axis coordinate -- i.e an offset from the
* main-start edge of the flex container's content box.
* @arg aCrossCoord The cross-axis coordinate -- i.e an offset from the
* cross-start edge of the flex container's content box.
* @arg aContainerMainSize The main size of flex container's content box.
* @arg aContainerCrossSize The cross size of flex container's content box.
* @return A LogicalPoint, with the flex container's writing mode, that
* represents the same position. The logical coordinates are
* relative to the flex container's content box.
*/
LogicalPoint LogicalPointFromFlexRelativePoint(
nscoord aMainCoord, nscoord aCrossCoord, nscoord aContainerMainSize,
nscoord aContainerCrossSize) const {
nscoord logicalCoordInMainAxis =
IsMainAxisReversed() ? aContainerMainSize - aMainCoord : aMainCoord;
nscoord logicalCoordInCrossAxis =
IsCrossAxisReversed() ? aContainerCrossSize - aCrossCoord : aCrossCoord;
return IsRowOriented() ? LogicalPoint(mWM, logicalCoordInMainAxis,
logicalCoordInCrossAxis)
: LogicalPoint(mWM, logicalCoordInCrossAxis,
logicalCoordInMainAxis);
}
/**
* Converts a "flex-relative" size (a main-axis & cross-axis size)
* into a LogicalSize, using the flex container's writing mode.
*
* @arg aMainSize The main-axis size.
* @arg aCrossSize The cross-axis size.
* @return A LogicalSize, with the flex container's writing mode, that
* represents the same size.
*/
LogicalSize LogicalSizeFromFlexRelativeSizes(nscoord aMainSize,
nscoord aCrossSize) const {
return IsRowOriented() ? LogicalSize(mWM, aMainSize, aCrossSize)
: LogicalSize(mWM, aCrossSize, aMainSize);
}
bool IsMainAxisHorizontal() const {
// If we're row-oriented, and our writing mode is NOT vertical,
// or we're column-oriented and our writing mode IS vertical,
// then our main axis is horizontal. This handles all cases:
return IsRowOriented() != mWM.IsVertical();
}
// Returns true if this flex item's inline axis in aItemWM is parallel (or
// antiparallel) to the container's main axis. Returns false, otherwise.
//
// Note: this is a helper used before constructing FlexItem. Inside of flex
// reflow code, FlexItem::IsInlineAxisMainAxis() is equivalent & more optimal.
bool IsInlineAxisMainAxis(WritingMode aItemWM) const {
return IsRowOriented() != GetWritingMode().IsOrthogonalTo(aItemWM);
}
// Maps justify-*: 'left' or 'right' to 'start' or 'end'.
StyleAlignFlags ResolveJustifyLeftRight(const StyleAlignFlags& aFlags) const {
MOZ_ASSERT(
aFlags == StyleAlignFlags::LEFT || aFlags == StyleAlignFlags::RIGHT,
"This helper accepts only 'LEFT' or 'RIGHT' flags!");
const auto wm = GetWritingMode();
const bool isJustifyLeft = aFlags == StyleAlignFlags::LEFT;
if (IsColumnOriented()) {
if (!wm.IsVertical()) {
// Container's alignment axis (main axis) is *not* parallel to the
// line-left <-> line-right axis or the physical left <-> physical right
// axis, so we map both 'left' and 'right' to 'start'.
return StyleAlignFlags::START;
}
MOZ_ASSERT(wm.PhysicalAxis(MainAxis()) == eAxisHorizontal,
"Vertical column-oriented flex container's main axis should "
"be parallel to physical left <-> right axis!");
// Map 'left' or 'right' to 'start' or 'end', depending on its block flow
// direction.
return isJustifyLeft == wm.IsVerticalLR() ? StyleAlignFlags::START
: StyleAlignFlags::END;
}
MOZ_ASSERT(MainAxis() == eLogicalAxisInline,
"Row-oriented flex container's main axis should be parallel to "
"line-left <-> line-right axis!");
// If we get here, we're operating on the flex container's inline axis,
// so we map 'left' to whichever of 'start' or 'end' corresponds to the
// *line-relative* left side; and similar for 'right'.
return isJustifyLeft == wm.IsBidiLTR() ? StyleAlignFlags::START
: StyleAlignFlags::END;
}
// Delete copy-constructor & reassignment operator, to prevent accidental
// (unnecessary) copying.
FlexboxAxisTracker(const FlexboxAxisTracker&) = delete;
FlexboxAxisTracker& operator=(const FlexboxAxisTracker&) = delete;
private:
const WritingMode mWM; // The flex container's writing mode.
const FlexboxAxisInfo mAxisInfo;
};
/**
* Represents a flex item.
* Includes the various pieces of input that the Flexbox Layout Algorithm uses
* to resolve a flexible width.
*/
class nsFlexContainerFrame::FlexItem final {
public:
// Normal constructor:
FlexItem(ReflowInput& aFlexItemReflowInput, float aFlexGrow,
float aFlexShrink, nscoord aFlexBaseSize, nscoord aMainMinSize,
nscoord aMainMaxSize, nscoord aTentativeCrossSize,
nscoord aCrossMinSize, nscoord aCrossMaxSize,
const FlexboxAxisTracker& aAxisTracker);
// Simplified constructor, to be used only for generating "struts":
// (NOTE: This "strut" constructor uses the *container's* writing mode, which
// we'll use on this FlexItem instead of the child frame's real writing mode.
// This is fine - it doesn't matter what writing mode we use for a
// strut, since it won't render any content and we already know its size.)
FlexItem(nsIFrame* aChildFrame, nscoord aCrossSize, WritingMode aContainerWM,
const FlexboxAxisTracker& aAxisTracker);
// Clone existing FlexItem for its underlying frame's continuation.
// @param aContinuation a continuation in our next-in-flow chain.
FlexItem CloneFor(nsIFrame* const aContinuation) const {
MOZ_ASSERT(Frame() == aContinuation->FirstInFlow(),
"aContinuation should be in aItem's continuation chain!");
FlexItem item(*this);
item.mFrame = aContinuation;
item.mHadMeasuringReflow = false;
return item;
}
// Accessors
nsIFrame* Frame() const { return mFrame; }
nscoord FlexBaseSize() const { return mFlexBaseSize; }
nscoord MainMinSize() const {
MOZ_ASSERT(!mNeedsMinSizeAutoResolution,
"Someone's using an unresolved 'auto' main min-size");
return mMainMinSize;
}
nscoord MainMaxSize() const { return mMainMaxSize; }
// Note: These return the main-axis position and size of our *content box*.
nscoord MainSize() const { return mMainSize; }
nscoord MainPosition() const { return mMainPosn; }
nscoord CrossMinSize() const { return mCrossMinSize; }
nscoord CrossMaxSize() const { return mCrossMaxSize; }
// Note: These return the cross-axis position and size of our *content box*.
nscoord CrossSize() const { return mCrossSize; }
nscoord CrossPosition() const { return mCrossPosn; }
// Lazy getter for mAscent.
nscoord ResolvedAscent(bool aUseFirstBaseline) const {
// XXXdholbert Two concerns to follow up on here:
// (1) We probably should be checking and reacting to aUseFirstBaseline
// for all of the cases here (e.g. this first one). Maybe we need to store
// two versions of mAscent and choose the appropriate one based on
// aUseFirstBaseline? This is roughly bug 1480850, I think.
// (2) We should be using the *container's* writing-mode (mCBWM) here,
// instead of the item's (mWM). This is essentially bug 1155322.
if (mAscent != ReflowOutput::ASK_FOR_BASELINE) {
return mAscent;
}
// Use GetFirstLineBaseline() or GetLastLineBaseline() as appropriate:
bool found =
aUseFirstBaseline
? nsLayoutUtils::GetFirstLineBaseline(mWM, mFrame, &mAscent)
: nsLayoutUtils::GetLastLineBaseline(mWM, mFrame, &mAscent);
if (found) {
return mAscent;
}
// If the nsLayoutUtils getter fails, then ask the frame directly:
auto baselineGroup = aUseFirstBaseline ? BaselineSharingGroup::First
: BaselineSharingGroup::Last;
if (auto baseline = mFrame->GetNaturalBaselineBOffset(
mWM, baselineGroup, BaselineExportContext::Other)) {
// Offset for last baseline from `GetNaturalBaselineBOffset` originates
// from the frame's block end, so convert it back.
mAscent = baselineGroup == BaselineSharingGroup::First
? *baseline
: mFrame->BSize(mWM) - *baseline;
return mAscent;
}
// We couldn't determine a baseline, so we synthesize one from border box:
mAscent = Baseline::SynthesizeBOffsetFromBorderBox(
mFrame, mWM, BaselineSharingGroup::First);
return mAscent;
}
// Convenience methods to compute the main & cross size of our *margin-box*.
nscoord OuterMainSize() const {
return mMainSize + MarginBorderPaddingSizeInMainAxis();
}
nscoord OuterCrossSize() const {
return mCrossSize + MarginBorderPaddingSizeInCrossAxis();
}
// Convenience methods to synthesize a style main size or a style cross size
// with box-size considered, to provide the size overrides when constructing
// ReflowInput for flex items.
StyleSize StyleMainSize() const {
nscoord mainSize = MainSize();
if (Frame()->StylePosition()->mBoxSizing == StyleBoxSizing::Border) {
mainSize += BorderPaddingSizeInMainAxis();
}
return StyleSize::LengthPercentage(
LengthPercentage::FromAppUnits(mainSize));
}
StyleSize StyleCrossSize() const {
nscoord crossSize = CrossSize();
if (Frame()->StylePosition()->mBoxSizing == StyleBoxSizing::Border) {
crossSize += BorderPaddingSizeInCrossAxis();
}
return StyleSize::LengthPercentage(
LengthPercentage::FromAppUnits(crossSize));
}
// Returns the distance between this FlexItem's baseline and the cross-start
// edge of its margin-box. Used in baseline alignment.
//
// (This function needs to be told which physical start side we're measuring
// the baseline from, so that it can look up the appropriate components from
// margin.)
nscoord BaselineOffsetFromOuterCrossEdge(mozilla::Side aStartSide,
bool aUseFirstLineBaseline) const;
double ShareOfWeightSoFar() const { return mShareOfWeightSoFar; }
bool IsFrozen() const { return mIsFrozen; }
bool HadMinViolation() const {
MOZ_ASSERT(!mIsFrozen, "min violation has no meaning for frozen items.");
return mHadMinViolation;
}
bool HadMaxViolation() const {
MOZ_ASSERT(!mIsFrozen, "max violation has no meaning for frozen items.");
return mHadMaxViolation;
}
bool WasMinClamped() const {
MOZ_ASSERT(mIsFrozen, "min clamping has no meaning for unfrozen items.");
return mHadMinViolation;
}
bool WasMaxClamped() const {
MOZ_ASSERT(mIsFrozen, "max clamping has no meaning for unfrozen items.");
return mHadMaxViolation;
}
// Indicates whether this item received a preliminary "measuring" reflow
// before its actual reflow.
bool HadMeasuringReflow() const { return mHadMeasuringReflow; }
// Indicates whether this item's computed cross-size property is 'auto'.
bool IsCrossSizeAuto() const;
// Indicates whether the cross-size property is set to something definite,
// for the purpose of preferred aspect ratio calculations.
bool IsCrossSizeDefinite(const ReflowInput& aItemReflowInput) const;
// Indicates whether this item's cross-size has been stretched (from having
// "align-self: stretch" with an auto cross-size and no auto margins in the
// cross axis).
bool IsStretched() const { return mIsStretched; }
// Indicates whether we need to resolve an 'auto' value for the main-axis
// min-[width|height] property.
bool NeedsMinSizeAutoResolution() const {
return mNeedsMinSizeAutoResolution;
}
bool HasAnyAutoMargin() const { return mHasAnyAutoMargin; }
// Indicates whether this item is a "strut" left behind by an element with
// visibility:collapse.
bool IsStrut() const { return mIsStrut; }
// The main axis and cross axis are relative to mCBWM.
LogicalAxis MainAxis() const { return mMainAxis; }
LogicalAxis CrossAxis() const { return GetOrthogonalAxis(mMainAxis); }
// IsInlineAxisMainAxis() returns true if this item's inline axis is parallel
// (or antiparallel) to the container's main axis. Otherwise (i.e. if this
// item's inline axis is orthogonal to the container's main axis), this
// function returns false. The next 3 methods are all other ways of asking
// the same question, and only exist for readability at callsites (depending
// on which axes those callsites are reasoning about).
bool IsInlineAxisMainAxis() const { return mIsInlineAxisMainAxis; }
bool IsInlineAxisCrossAxis() const { return !mIsInlineAxisMainAxis; }
bool IsBlockAxisMainAxis() const { return !mIsInlineAxisMainAxis; }
bool IsBlockAxisCrossAxis() const { return mIsInlineAxisMainAxis; }
WritingMode GetWritingMode() const { return mWM; }
WritingMode ContainingBlockWM() const { return mCBWM; }
StyleAlignSelf AlignSelf() const { return mAlignSelf; }
StyleAlignFlags AlignSelfFlags() const { return mAlignSelfFlags; }
// Returns the flex factor (flex-grow or flex-shrink), depending on
// 'aIsUsingFlexGrow'.
//
// Asserts fatally if called on a frozen item (since frozen items are not
// flexible).
float GetFlexFactor(bool aIsUsingFlexGrow) {
MOZ_ASSERT(!IsFrozen(), "shouldn't need flex factor after item is frozen");
return aIsUsingFlexGrow ? mFlexGrow : mFlexShrink;
}
// Returns the weight that we should use in the "resolving flexible lengths"
// algorithm. If we're using the flex grow factor, we just return that;
// otherwise, we return the "scaled flex shrink factor" (scaled by our flex
// base size, so that when both large and small items are shrinking, the large
// items shrink more).
//
// I'm calling this a "weight" instead of a "[scaled] flex-[grow|shrink]
// factor", to more clearly distinguish it from the actual flex-grow &
// flex-shrink factors.
//
// Asserts fatally if called on a frozen item (since frozen items are not
// flexible).
float GetWeight(bool aIsUsingFlexGrow) {
MOZ_ASSERT(!IsFrozen(), "shouldn't need weight after item is frozen");
if (aIsUsingFlexGrow) {
return mFlexGrow;
}
// We're using flex-shrink --> return mFlexShrink * mFlexBaseSize
if (mFlexBaseSize == 0) {
// Special-case for mFlexBaseSize == 0 -- we have no room to shrink, so
// regardless of mFlexShrink, we should just return 0.
// (This is really a special-case for when mFlexShrink is infinity, to
// avoid performing mFlexShrink * mFlexBaseSize = inf * 0 = undefined.)
return 0.0f;
}
return mFlexShrink * mFlexBaseSize;
}
bool TreatBSizeAsIndefinite() const { return mTreatBSizeAsIndefinite; }
const AspectRatio& GetAspectRatio() const { return mAspectRatio; }
bool HasAspectRatio() const { return !!mAspectRatio; }
// Getters for margin:
// ===================
LogicalMargin Margin() const { return mMargin; }
nsMargin PhysicalMargin() const { return mMargin.GetPhysicalMargin(mCBWM); }
// Returns the margin component for a given LogicalSide in flex container's
// writing-mode.
nscoord GetMarginComponentForSide(LogicalSide aSide) const {
return mMargin.Side(aSide, mCBWM);
}
// Returns the total space occupied by this item's margins in the given axis
nscoord MarginSizeInMainAxis() const {
return mMargin.StartEnd(MainAxis(), mCBWM);
}
nscoord MarginSizeInCrossAxis() const {
return mMargin.StartEnd(CrossAxis(), mCBWM);
}
// Getters for border/padding
// ==========================
// Returns the total space occupied by this item's borders and padding in
// the given axis
LogicalMargin BorderPadding() const { return mBorderPadding; }
nscoord BorderPaddingSizeInMainAxis() const {
return mBorderPadding.StartEnd(MainAxis(), mCBWM);
}
nscoord BorderPaddingSizeInCrossAxis() const {
return mBorderPadding.StartEnd(CrossAxis(), mCBWM);
}
// Getter for combined margin/border/padding
// =========================================
// Returns the total space occupied by this item's margins, borders and
// padding in the given axis
nscoord MarginBorderPaddingSizeInMainAxis() const {
return MarginSizeInMainAxis() + BorderPaddingSizeInMainAxis();
}
nscoord MarginBorderPaddingSizeInCrossAxis() const {
return MarginSizeInCrossAxis() + BorderPaddingSizeInCrossAxis();
}
// Setters
// =======
// Helper to set the resolved value of min-[width|height]:auto for the main
// axis. (Should only be used if NeedsMinSizeAutoResolution() returns true.)
void UpdateMainMinSize(nscoord aNewMinSize) {
NS_ASSERTION(aNewMinSize >= 0,
"How did we end up with a negative min-size?");
MOZ_ASSERT(
mMainMaxSize == NS_UNCONSTRAINEDSIZE || mMainMaxSize >= aNewMinSize,
"Should only use this function for resolving min-size:auto, "
"and main max-size should be an upper-bound for resolved val");
MOZ_ASSERT(
mNeedsMinSizeAutoResolution &&
(mMainMinSize == 0 || mFrame->IsThemed(mFrame->StyleDisplay())),
"Should only use this function for resolving min-size:auto, "
"so we shouldn't already have a nonzero min-size established "
"(unless it's a themed-widget-imposed minimum size)");
if (aNewMinSize > mMainMinSize) {
mMainMinSize = aNewMinSize;
// Also clamp main-size to be >= new min-size:
mMainSize = std::max(mMainSize, aNewMinSize);
}
mNeedsMinSizeAutoResolution = false;
}
// This sets our flex base size, and then sets our main size to the
// resulting "hypothetical main size" (the base size clamped to our
// main-axis [min,max] sizing constraints).
void SetFlexBaseSizeAndMainSize(nscoord aNewFlexBaseSize) {
MOZ_ASSERT(!mIsFrozen || mFlexBaseSize == NS_UNCONSTRAINEDSIZE,
"flex base size shouldn't change after we're frozen "
"(unless we're just resolving an intrinsic size)");
mFlexBaseSize = aNewFlexBaseSize;
// Before we've resolved flexible lengths, we keep mMainSize set to
// the 'hypothetical main size', which is the flex base size, clamped
// to the [min,max] range:
mMainSize = NS_CSS_MINMAX(mFlexBaseSize, mMainMinSize, mMainMaxSize);
FLEX_LOGV(
"Set flex base size: %d, hypothetical main size: %d for flex item %p",
mFlexBaseSize, mMainSize, mFrame);
}
// Setters used while we're resolving flexible lengths
// ---------------------------------------------------
// Sets the main-size of our flex item's content-box.
void SetMainSize(nscoord aNewMainSize) {
MOZ_ASSERT(!mIsFrozen, "main size shouldn't change after we're frozen");
mMainSize = aNewMainSize;
}
void SetShareOfWeightSoFar(double aNewShare) {
MOZ_ASSERT(!mIsFrozen || aNewShare == 0.0,
"shouldn't be giving this item any share of the weight "
"after it's frozen");
mShareOfWeightSoFar = aNewShare;
}
void Freeze() {
mIsFrozen = true;
// Now that we are frozen, the meaning of mHadMinViolation and
// mHadMaxViolation changes to indicate min and max clamping. Clear
// both of the member variables so that they are ready to be set
// as clamping state later, if necessary.
mHadMinViolation = false;
mHadMaxViolation = false;
}
void SetHadMinViolation() {
MOZ_ASSERT(!mIsFrozen,
"shouldn't be changing main size & having violations "
"after we're frozen");
mHadMinViolation = true;
}
void SetHadMaxViolation() {
MOZ_ASSERT(!mIsFrozen,
"shouldn't be changing main size & having violations "
"after we're frozen");
mHadMaxViolation = true;
}
void ClearViolationFlags() {
MOZ_ASSERT(!mIsFrozen,
"shouldn't be altering violation flags after we're "
"frozen");
mHadMinViolation = mHadMaxViolation = false;
}
void SetWasMinClamped() {
MOZ_ASSERT(!mHadMinViolation && !mHadMaxViolation, "only clamp once");
// This reuses the mHadMinViolation member variable to track clamping
// events. This is allowable because mHadMinViolation only reflects
// a violation up until the item is frozen.
MOZ_ASSERT(mIsFrozen, "shouldn't set clamping state when we are unfrozen");
mHadMinViolation = true;
}
void SetWasMaxClamped() {
MOZ_ASSERT(!mHadMinViolation && !mHadMaxViolation, "only clamp once");
// This reuses the mHadMaxViolation member variable to track clamping
// events. This is allowable because mHadMaxViolation only reflects
// a violation up until the item is frozen.
MOZ_ASSERT(mIsFrozen, "shouldn't set clamping state when we are unfrozen");
mHadMaxViolation = true;
}
// Setters for values that are determined after we've resolved our main size
// -------------------------------------------------------------------------
// Sets the main-axis position of our flex item's content-box.
// (This is the distance between the main-start edge of the flex container
// and the main-start edge of the flex item's content-box.)
void SetMainPosition(nscoord aPosn) {
MOZ_ASSERT(mIsFrozen, "main size should be resolved before this");
mMainPosn = aPosn;
}
// Sets the cross-size of our flex item's content-box.
void SetCrossSize(nscoord aCrossSize) {
MOZ_ASSERT(!mIsStretched,
"Cross size shouldn't be modified after it's been stretched");
mCrossSize = aCrossSize;
}
// Sets the cross-axis position of our flex item's content-box.
// (This is the distance between the cross-start edge of the flex container
// and the cross-start edge of the flex item.)
void SetCrossPosition(nscoord aPosn) {
MOZ_ASSERT(mIsFrozen, "main size should be resolved before this");
mCrossPosn = aPosn;
}
// After a FlexItem has had a reflow, this method can be used to cache its
// (possibly-unresolved) ascent, in case it's needed later for
// baseline-alignment or to establish the container's baseline.
// (NOTE: This can be marked 'const' even though it's modifying mAscent,
// because mAscent is mutable. It's nice for this to be 'const', because it
// means our final reflow can iterate over const FlexItem pointers, and we
// can be sure it's not modifying those FlexItems, except via this method.)
void SetAscent(nscoord aAscent) const {
mAscent = aAscent; // NOTE: this may be ASK_FOR_BASELINE
}
void SetHadMeasuringReflow() { mHadMeasuringReflow = true; }
void SetIsStretched() {
MOZ_ASSERT(mIsFrozen, "main size should be resolved before this");
mIsStretched = true;
}
// Setter for margin components (for resolving "auto" margins)
void SetMarginComponentForSide(LogicalSide aSide, nscoord aLength) {
MOZ_ASSERT(mIsFrozen, "main size should be resolved before this");
mMargin.Side(aSide, mCBWM) = aLength;
}
void ResolveStretchedCrossSize(nscoord aLineCrossSize);
// Resolves flex base size if flex-basis' used value is 'content', using this
// item's preferred aspect ratio and cross size.
void ResolveFlexBaseSizeFromAspectRatio(const ReflowInput& aItemReflowInput);
uint32_t NumAutoMarginsInMainAxis() const {
return NumAutoMarginsInAxis(MainAxis());
};
uint32_t NumAutoMarginsInCrossAxis() const {
return NumAutoMarginsInAxis(CrossAxis());
};
// Once the main size has been resolved, should we bother doing layout to
// establish the cross size?
bool CanMainSizeInfluenceCrossSize() const;
// Returns a main size, clamped by any definite min and max cross size
// converted through the preferred aspect ratio. The caller is responsible for
// ensuring that the flex item's preferred aspect ratio is not zero.
nscoord ClampMainSizeViaCrossAxisConstraints(
nscoord aMainSize, const ReflowInput& aItemReflowInput) const;
// Indicates whether we think this flex item needs a "final" reflow
// (after its final flexed size & final position have been determined).
//
// @param aParentReflowInput the flex container's reflow input.
// @return true if such a reflow is needed, or false if we believe it can
// simply be moved to its final position and skip the reflow.
bool NeedsFinalReflow(const ReflowInput& aParentReflowInput) const;
// Gets the block frame that contains the flex item's content. This is
// Frame() itself or one of its descendants.
nsBlockFrame* BlockFrame() const;
protected:
bool IsMinSizeAutoResolutionNeeded() const;
uint32_t NumAutoMarginsInAxis(LogicalAxis aAxis) const;
// Values that we already know in constructor, and remain unchanged:
// The flex item's frame.
nsIFrame* mFrame = nullptr;
float mFlexGrow = 0.0f;
float mFlexShrink = 0.0f;
AspectRatio mAspectRatio;
// The flex item's writing mode.
WritingMode mWM;
// The flex container's writing mode.
WritingMode mCBWM;
// The flex container's main axis in flex container's writing mode.
LogicalAxis mMainAxis;
// Stored in flex container's writing mode.
LogicalMargin mBorderPadding;
// Stored in flex container's writing mode. Its value can change when we
// resolve "auto" marigns.
LogicalMargin mMargin;
// These are non-const so that we can lazily update them with the item's
// intrinsic size (obtained via a "measuring" reflow), when necessary.
// (e.g. for "flex-basis:auto;height:auto" & "min-height:auto")
nscoord mFlexBaseSize = 0;
nscoord mMainMinSize = 0;
nscoord mMainMaxSize = 0;
// mCrossMinSize and mCrossMaxSize are not changed after constructor.
nscoord mCrossMinSize = 0;
nscoord mCrossMaxSize = 0;
// Values that we compute after constructor:
nscoord mMainSize = 0;
nscoord mMainPosn = 0;
nscoord mCrossSize = 0;
nscoord mCrossPosn = 0;
// Mutable b/c it's set & resolved lazily, sometimes via const pointer. See
// comment above SetAscent().
// We initialize this to ASK_FOR_BASELINE, and opportunistically fill it in
// with a real value if we end up reflowing this flex item. (But if we don't
// reflow this flex item, then this sentinel tells us that we don't know it
// yet & anyone who cares will need to explicitly request it.)
mutable nscoord mAscent = ReflowOutput::ASK_FOR_BASELINE;
// Temporary state, while we're resolving flexible widths (for our main size)
// XXXdholbert To save space, we could use a union to make these variables
// overlay the same memory as some other member vars that aren't touched
// until after main-size has been resolved. In particular, these could share
// memory with mMainPosn through mAscent, and mIsStretched.
double mShareOfWeightSoFar = 0.0;
bool mIsFrozen = false;
bool mHadMinViolation = false;
bool mHadMaxViolation = false;
// Did this item get a preliminary reflow, to measure its desired height?
bool mHadMeasuringReflow = false;
// See IsStretched() documentation.
bool mIsStretched = false;
// Is this item a "strut" left behind by an element with visibility:collapse?
bool mIsStrut = false;
// See IsInlineAxisMainAxis() documentation. This is not changed after
// constructor.
bool mIsInlineAxisMainAxis = true;
// Does this item need to resolve a min-[width|height]:auto (in main-axis)?
//
// Note: mNeedsMinSizeAutoResolution needs to be declared towards the end of
// the member variables since it's initialized in a method that depends on
// other members declared above such as mCBWM, mMainAxis, and
// mIsInlineAxisMainAxis.
bool mNeedsMinSizeAutoResolution = false;
// Should we take care to treat this item's resolved BSize as indefinite?
bool mTreatBSizeAsIndefinite = false;
// Does this item have an auto margin in either main or cross axis?
bool mHasAnyAutoMargin = false;
// My "align-self" computed value (with "auto" swapped out for parent"s
// "align-items" value, in our constructor).
StyleAlignSelf mAlignSelf{StyleAlignFlags::AUTO};
// Flags for 'align-self' (safe/unsafe/legacy).
StyleAlignFlags mAlignSelfFlags{0};
};
/**
* Represents a single flex line in a flex container.
* Manages an array of the FlexItems that are in the line.
*/
class nsFlexContainerFrame::FlexLine final {
public:
explicit FlexLine(nscoord aMainGapSize) : mMainGapSize(aMainGapSize) {}
nscoord SumOfGaps() const {
return NumItems() > 0 ? (NumItems() - 1) * mMainGapSize : 0;
}
// Returns the sum of our FlexItems' outer hypothetical main sizes plus the
// sum of main axis {row,column}-gaps between items.
// ("outer" = margin-box, and "hypothetical" = before flexing)
AuCoord64 TotalOuterHypotheticalMainSize() const {
return mTotalOuterHypotheticalMainSize;
}
// Accessors for our FlexItems & information about them:
//
// Note: Using IsEmpty() to ensure that the FlexLine is non-empty before
// calling FirstItem() or LastItem().
FlexItem& FirstItem() { return mItems[0]; }
const FlexItem& FirstItem() const { return mItems[0]; }
FlexItem& LastItem() { return mItems.LastElement(); }
const FlexItem& LastItem() const { return mItems.LastElement(); }
bool IsEmpty() const { return mItems.IsEmpty(); }
uint32_t NumItems() const { return mItems.Length(); }
nsTArray<FlexItem>& Items() { return mItems; }
const nsTArray<FlexItem>& Items() const { return mItems; }
// Adds the last flex item's hypothetical outer main-size and
// margin/border/padding to our totals. This should be called exactly once for
// each flex item, after we've determined that this line is the correct home
// for that item.
void AddLastItemToMainSizeTotals() {
const FlexItem& lastItem = Items().LastElement();
// Update our various bookkeeping member-vars:
if (lastItem.IsFrozen()) {
mNumFrozenItems++;
}
mTotalItemMBP += lastItem.MarginBorderPaddingSizeInMainAxis();
mTotalOuterHypotheticalMainSize += lastItem.OuterMainSize();
// If the item added was not the first item in the line, we add in any gap
// space as needed.
if (NumItems() >= 2) {
mTotalOuterHypotheticalMainSize += mMainGapSize;
}
}
// Computes the cross-size and baseline position of this FlexLine, based on
// its FlexItems.
void ComputeCrossSizeAndBaseline(const FlexboxAxisTracker& aAxisTracker);
// Returns the cross-size of this line.
nscoord LineCrossSize() const { return mLineCrossSize; }
// Setter for line cross-size -- needed for cases where the flex container
// imposes a cross-size on the line. (e.g. for single-line flexbox, or for
// multi-line flexbox with 'align-content: stretch')
void SetLineCrossSize(nscoord aLineCrossSize) {
mLineCrossSize = aLineCrossSize;
}
/**
* Returns the offset within this line where any baseline-aligned FlexItems
* should place their baseline. The return value represents a distance from
* the line's cross-start edge.
*
* If there are no baseline-aligned FlexItems, returns nscoord_MIN.
*/
nscoord FirstBaselineOffset() const { return mFirstBaselineOffset; }
/**
* Returns the offset within this line where any last baseline-aligned
* FlexItems should place their baseline. Opposite the case of the first
* baseline offset, this represents a distance from the line's cross-end
* edge (since last baseline-aligned items are flush to the cross-end edge).
*
* If there are no last baseline-aligned FlexItems, returns nscoord_MIN.
*/
nscoord LastBaselineOffset() const { return mLastBaselineOffset; }
/**
* Returns the gap size in the main axis for this line. Used for gap
* calculations.
*/
nscoord MainGapSize() const { return mMainGapSize; }
// Runs the "Resolving Flexible Lengths" algorithm from section 9.7 of the
// CSS flexbox spec to distribute aFlexContainerMainSize among our flex items.
// https://drafts.csswg.org/css-flexbox-1/#resolve-flexible-lengths
void ResolveFlexibleLengths(nscoord aFlexContainerMainSize,
ComputedFlexLineInfo* aLineInfo);
void PositionItemsInMainAxis(const StyleContentDistribution& aJustifyContent,
nscoord aContentBoxMainSize,
const FlexboxAxisTracker& aAxisTracker);
void PositionItemsInCrossAxis(nscoord aLineStartPosition,
const FlexboxAxisTracker& aAxisTracker);
private:
// Helpers for ResolveFlexibleLengths():
void FreezeItemsEarly(bool aIsUsingFlexGrow, ComputedFlexLineInfo* aLineInfo);
void FreezeOrRestoreEachFlexibleSize(const nscoord aTotalViolation,
bool aIsFinalIteration);
// Stores this line's flex items.
nsTArray<FlexItem> mItems;
// Number of *frozen* FlexItems in this line, based on FlexItem::IsFrozen().
// Mostly used for optimization purposes, e.g. to bail out early from loops
// when we can tell they have nothing left to do.
uint32_t mNumFrozenItems = 0;
// Sum of margin/border/padding for the FlexItems in this FlexLine.
nscoord mTotalItemMBP = 0;
// Sum of FlexItems' outer hypothetical main sizes and all main-axis
// {row,columnm}-gaps between items.
// (i.e. their flex base sizes, clamped via their min/max-size properties,
// plus their main-axis margin/border/padding, plus the sum of the gaps.)
//
// This variable uses a 64-bit coord type to avoid integer overflow in case
// several of the individual items have huge hypothetical main sizes, which
// can happen with percent-width table-layout:fixed descendants. We have to
// avoid integer overflow in order to shrink items properly in that scenario.
AuCoord64 mTotalOuterHypotheticalMainSize = 0;
nscoord mLineCrossSize = 0;
nscoord mFirstBaselineOffset = nscoord_MIN;
nscoord mLastBaselineOffset = nscoord_MIN;
// Maintain size of each {row,column}-gap in the main axis
const nscoord mMainGapSize;
};
// Information about a strut left behind by a FlexItem that's been collapsed
// using "visibility:collapse".
struct nsFlexContainerFrame::StrutInfo {
StrutInfo(uint32_t aItemIdx, nscoord aStrutCrossSize)
: mItemIdx(aItemIdx), mStrutCrossSize(aStrutCrossSize) {}
uint32_t mItemIdx; // Index in the child list.
nscoord mStrutCrossSize; // The cross-size of this strut.
};
// Flex data shared by the flex container frames in a continuation chain, owned
// by the first-in-flow. The data is initialized at the end of the
// first-in-flow's Reflow().
struct nsFlexContainerFrame::SharedFlexData final {
// The flex lines generated in DoFlexLayout() by our first-in-flow.
nsTArray<FlexLine> mLines;
// The final content main/cross size computed by DoFlexLayout.
nscoord mContentBoxMainSize = NS_UNCONSTRAINEDSIZE;
nscoord mContentBoxCrossSize = NS_UNCONSTRAINEDSIZE;
// Update this struct. Called by the first-in-flow.
void Update(FlexLayoutResult&& aFlr) {
mLines = std::move(aFlr.mLines);
mContentBoxMainSize = aFlr.mContentBoxMainSize;
mContentBoxCrossSize = aFlr.mContentBoxCrossSize;
}
// The frame property under which this struct is stored. Set only on the
// first-in-flow.
NS_DECLARE_FRAME_PROPERTY_DELETABLE(Prop, SharedFlexData)
};
// Flex data stored in every flex container's in-flow fragment (continuation).
//
// It's intended to prevent quadratic operations resulting from each fragment
// having to walk its full prev-in-flow chain, and also serves as an argument to
// the flex container next-in-flow's ReflowChildren(), to compute the position
// offset for each flex item.
struct nsFlexContainerFrame::PerFragmentFlexData final {
// Suppose D is the distance from a flex container fragment's content-box
// block-start edge to whichever is larger of either (a) the block-end edge of
// its children, or (b) the available space's block-end edge. (Note: in case
// (b), D is conceptually the sum of the block-size of the children, the
// packing space before & in between them, and part of the packing space after
// them.)
//
// This variable stores the sum of the D values for the current flex container
// fragments and for all its previous fragments
nscoord mCumulativeContentBoxBSize = 0;
// This variable accumulates FirstLineOrFirstItemBAxisMetrics::mBEndEdgeShift,
// for the current flex container fragment and for all its previous fragments.
// See the comment of mBEndEdgeShift for its computation details. In short,
// this value is the net block-end edge shift, accumulated for the children in
// all the previous fragments. This number is non-negative.
//
// This value is also used to grow a flex container's block-size if the
// container's computed block-size is unconstrained. For example: a tall item
// may be pushed to the next page/column, which leaves some wasted area at the
// bottom of the current flex container fragment, and causes the flex
// container fragments to be (collectively) larger than the hypothetical
// unfragmented size. Another example: a tall flex item may be broken into
// multiple fragments, and those fragments may have a larger collective
// block-size as compared to the item's original unfragmented size; the
// container would need to increase its block-size to account for this.
nscoord mCumulativeBEndEdgeShift = 0;
// The frame property under which this struct is stored. Cached on every
// in-flow fragment (continuation) at the end of the flex container's
// Reflow().
NS_DECLARE_FRAME_PROPERTY_DELETABLE(Prop, PerFragmentFlexData)
};
static void BuildStrutInfoFromCollapsedItems(const nsTArray<FlexLine>& aLines,
nsTArray<StrutInfo>& aStruts) {
MOZ_ASSERT(aStruts.IsEmpty(),
"We should only build up StrutInfo once per reflow, so "
"aStruts should be empty when this is called");
uint32_t itemIdxInContainer = 0;
for (const FlexLine& line : aLines) {
for (const FlexItem& item : line.Items()) {
if (item.Frame()->StyleVisibility()->IsCollapse()) {
// Note the cross size of the line as the item's strut size.
aStruts.AppendElement(
StrutInfo(itemIdxInContainer, line.LineCrossSize()));
}
itemIdxInContainer++;
}
}
}
static mozilla::StyleAlignFlags SimplifyAlignOrJustifyContentForOneItem(
const StyleContentDistribution& aAlignmentVal, bool aIsAlign) {
// Mask away any explicit fallback, to get the main (non-fallback) part of
// the specified value:
StyleAlignFlags specified = aAlignmentVal.primary;
// XXX strip off <overflow-position> bits until we implement it (bug 1311892)
specified &= ~StyleAlignFlags::FLAG_BITS;
// FIRST: handle a special-case for "justify-content:stretch" (or equivalent),
// which requires that we ignore any author-provided explicit fallback value.
if (specified == StyleAlignFlags::NORMAL) {
// In a flex container, *-content: "'normal' behaves as 'stretch'".
// Do that conversion early, so it benefits from our 'stretch' special-case.
// https://drafts.csswg.org/css-align-3/#distribution-flex
specified = StyleAlignFlags::STRETCH;
}
if (!aIsAlign && specified == StyleAlignFlags::STRETCH) {
// In a flex container, in "justify-content Axis: [...] 'stretch' behaves
// as 'flex-start' (ignoring the specified fallback alignment, if any)."
// https://drafts.csswg.org/css-align-3/#distribution-flex
// So, we just directly return 'flex-start', & ignore explicit fallback..
return StyleAlignFlags::FLEX_START;
}
// TODO: Check for an explicit fallback value (and if it's present, use it)
// here once we parse it, see https://github.com/w3c/csswg-drafts/issues/1002.
// If there's no explicit fallback, use the implied fallback values for
// space-{between,around,evenly} (since those values only make sense with
// multiple alignment subjects), and otherwise just use the specified value:
if (specified == StyleAlignFlags::SPACE_BETWEEN) {
return StyleAlignFlags::FLEX_START;
}
if (specified == StyleAlignFlags::SPACE_AROUND ||
specified == StyleAlignFlags::SPACE_EVENLY) {
return StyleAlignFlags::CENTER;
}
return specified;
}
bool nsFlexContainerFrame::DrainSelfOverflowList() {
return DrainAndMergeSelfOverflowList();
}
void nsFlexContainerFrame::AppendFrames(ChildListID aListID,
nsFrameList&& aFrameList) {
NoteNewChildren(aListID, aFrameList);
nsContainerFrame::AppendFrames(aListID, std::move(aFrameList));
}
void nsFlexContainerFrame::InsertFrames(
ChildListID aListID, nsIFrame* aPrevFrame,
const nsLineList::iterator* aPrevFrameLine, nsFrameList&& aFrameList) {
NoteNewChildren(aListID, aFrameList);
nsContainerFrame::InsertFrames(aListID, aPrevFrame, aPrevFrameLine,
std::move(aFrameList));
}
void nsFlexContainerFrame::RemoveFrame(ChildListID aListID,
nsIFrame* aOldFrame) {
MOZ_ASSERT(aListID == FrameChildListID::Principal, "unexpected child list");
#ifdef DEBUG
SetDidPushItemsBitIfNeeded(aListID, aOldFrame);
#endif
nsContainerFrame::RemoveFrame(aListID, aOldFrame);
}
StyleAlignFlags nsFlexContainerFrame::CSSAlignmentForAbsPosChild(
const ReflowInput& aChildRI, LogicalAxis aLogicalAxis) const {
const FlexboxAxisTracker axisTracker(this);
// If we're row-oriented and the caller is asking about our inline axis (or
// alternately, if we're column-oriented and the caller is asking about our
// block axis), then the caller is really asking about our *main* axis.
// Otherwise, the caller is asking about our cross axis.
const bool isMainAxis =
(axisTracker.IsRowOriented() == (aLogicalAxis == eLogicalAxisInline));
const nsStylePosition* containerStylePos = StylePosition();
const bool isAxisReversed = isMainAxis ? axisTracker.IsMainAxisReversed()
: axisTracker.IsCrossAxisReversed();
StyleAlignFlags alignment{0};
StyleAlignFlags alignmentFlags{0};
if (isMainAxis) {
// We're aligning in the main axis: align according to 'justify-content'.
// (We don't care about justify-self; it has no effect on children of flex
// containers, unless https://github.com/w3c/csswg-drafts/issues/7644
// changes that.)
alignment = SimplifyAlignOrJustifyContentForOneItem(
containerStylePos->mJustifyContent,
/*aIsAlign = */ false);
} else {
// We're aligning in the cross axis: align according to 'align-self'.
// (We don't care about align-content; it has no effect on abspos flex
// children, per https://github.com/w3c/csswg-drafts/issues/7596 )
alignment = aChildRI.mStylePosition->UsedAlignSelf(Style())._0;
// Extract and strip align flag bits
alignmentFlags = alignment & StyleAlignFlags::FLAG_BITS;
alignment &= ~StyleAlignFlags::FLAG_BITS;
if (alignment == StyleAlignFlags::NORMAL) {
// "the 'normal' keyword behaves as 'start' on replaced
// absolutely-positioned boxes, and behaves as 'stretch' on all other
// absolutely-positioned boxes."
// https://drafts.csswg.org/css-align/#align-abspos
alignment = aChildRI.mFrame->IsFrameOfType(nsIFrame::eReplaced)
? StyleAlignFlags::START
: StyleAlignFlags::STRETCH;
}
}
if (alignment == StyleAlignFlags::STRETCH) {
// The default fallback alignment for 'stretch' is 'flex-start'.
alignment = StyleAlignFlags::FLEX_START;
}
// Resolve flex-start, flex-end, auto, left, right, baseline, last baseline;
if (alignment == StyleAlignFlags::FLEX_START) {
alignment = isAxisReversed ? StyleAlignFlags::END : StyleAlignFlags::START;
} else if (alignment == StyleAlignFlags::FLEX_END) {
alignment = isAxisReversed ? StyleAlignFlags::START : StyleAlignFlags::END;
} else if (alignment == StyleAlignFlags::LEFT ||
alignment == StyleAlignFlags::RIGHT) {
MOZ_ASSERT(isMainAxis, "Only justify-* can have 'left' and 'right'!");
alignment = axisTracker.ResolveJustifyLeftRight(alignment);
} else if (alignment == StyleAlignFlags::BASELINE) {
alignment = StyleAlignFlags::START;
} else if (alignment == StyleAlignFlags::LAST_BASELINE) {
alignment = StyleAlignFlags::END;
}
MOZ_ASSERT(alignment != StyleAlignFlags::STRETCH,
"We should've converted 'stretch' to the fallback alignment!");
MOZ_ASSERT(alignment != StyleAlignFlags::FLEX_START &&
alignment != StyleAlignFlags::FLEX_END,
"nsAbsoluteContainingBlock doesn't know how to handle "
"flex-relative axis for flex containers!");
return (alignment | alignmentFlags);
}
void nsFlexContainerFrame::GenerateFlexItemForChild(
FlexLine& aLine, nsIFrame* aChildFrame,
const ReflowInput& aParentReflowInput,
const FlexboxAxisTracker& aAxisTracker,
const nscoord aTentativeContentBoxCrossSize) {
const auto flexWM = aAxisTracker.GetWritingMode();
const auto childWM = aChildFrame->GetWritingMode();
// Note: we use GetStyleFrame() to access the sizing & flex properties here.
// This lets us correctly handle table wrapper frames as flex items since
// their inline-size and block-size properties are always 'auto'. In order for
// 'flex-basis:auto' to actually resolve to the author's specified inline-size
// or block-size, we need to dig through to the inner table.
const auto* stylePos =
nsLayoutUtils::GetStyleFrame(aChildFrame)->StylePosition();
// Construct a StyleSizeOverrides for this flex item so that its ReflowInput
// below will use and resolve its flex base size rather than its corresponding
// preferred main size property (only for modern CSS flexbox).
StyleSizeOverrides sizeOverrides;
if (!IsLegacyBox(this)) {
Maybe<StyleSize> styleFlexBaseSize;
// When resolving flex base size, flex items use their 'flex-basis' property
// in place of their preferred main size (e.g. 'width') for sizing purposes,
// *unless* they have 'flex-basis:auto' in which case they use their
// preferred main size after all.
const auto& flexBasis = stylePos->mFlexBasis;
const auto& styleMainSize = stylePos->Size(aAxisTracker.MainAxis(), flexWM);
if (IsUsedFlexBasisContent(flexBasis, styleMainSize)) {
// If we get here, we're resolving the flex base size for a flex item, and
// we fall into the flexbox spec section 9.2 step 3, substep C (if we have
// a definite cross size) or E (if not).
styleFlexBaseSize.emplace(StyleSize::MaxContent());
} else if (flexBasis.IsSize() && !flexBasis.IsAuto()) {
// For all other non-'auto' flex-basis values, we just swap in the
// flex-basis itself for the preferred main-size property.
styleFlexBaseSize.emplace(flexBasis.AsSize());
} else {
// else: flex-basis is 'auto', which is deferring to some explicit value
// in the preferred main size.
MOZ_ASSERT(flexBasis.IsAuto());
styleFlexBaseSize.emplace(styleMainSize);
}
MOZ_ASSERT(styleFlexBaseSize, "We should've emplace styleFlexBaseSize!");
// Provide the size override for the preferred main size property.
if (aAxisTracker.IsInlineAxisMainAxis(childWM)) {
sizeOverrides.mStyleISize = std::move(styleFlexBaseSize);
} else {
sizeOverrides.mStyleBSize = std::move(styleFlexBaseSize);
}
// 'flex-basis' should works on the inner table frame for a table flex item,
// just like how 'height' works on a table element.
sizeOverrides.mApplyOverridesVerbatim = true;
}
// Create temporary reflow input just for sizing -- to get hypothetical
// main-size and the computed values of min / max main-size property.
// (This reflow input will _not_ be used for reflow.)
ReflowInput childRI(PresContext(), aParentReflowInput, aChildFrame,
aParentReflowInput.ComputedSize(childWM), Nothing(), {},
sizeOverrides);
// FLEX GROW & SHRINK WEIGHTS
// --------------------------
float flexGrow, flexShrink;
if (IsLegacyBox(this)) {
flexGrow = flexShrink = aChildFrame->StyleXUL()->mBoxFlex;
} else {
flexGrow = stylePos->mFlexGrow;
flexShrink = stylePos->mFlexShrink;
}
// MAIN SIZES (flex base size, min/max size)
// -----------------------------------------
const LogicalSize computedSizeInFlexWM = childRI.ComputedSize(flexWM);
const LogicalSize computedMinSizeInFlexWM = childRI.ComputedMinSize(flexWM);
const LogicalSize computedMaxSizeInFlexWM = childRI.ComputedMaxSize(flexWM);
const nscoord flexBaseSize = aAxisTracker.MainComponent(computedSizeInFlexWM);
const nscoord mainMinSize =
aAxisTracker.MainComponent(computedMinSizeInFlexWM);
const nscoord mainMaxSize =
aAxisTracker.MainComponent(computedMaxSizeInFlexWM);
// This is enforced by the ReflowInput where these values come from:
MOZ_ASSERT(mainMinSize <= mainMaxSize, "min size is larger than max size");
// CROSS SIZES (tentative cross size, min/max cross size)
// ------------------------------------------------------
// Grab the cross size from the reflow input. This might be the right value,
// or we might resolve it to something else in SizeItemInCrossAxis(); hence,
// it's tentative. See comment under "Cross Size Determination" for more.
const nscoord tentativeCrossSize =
aAxisTracker.CrossComponent(computedSizeInFlexWM);
const nscoord crossMinSize =
aAxisTracker.CrossComponent(computedMinSizeInFlexWM);
const nscoord crossMaxSize =
aAxisTracker.CrossComponent(computedMaxSizeInFlexWM);
// Construct the flex item!
FlexItem& item = *aLine.Items().EmplaceBack(
childRI, flexGrow, flexShrink, flexBaseSize, mainMinSize, mainMaxSize,
tentativeCrossSize, crossMinSize, crossMaxSize, aAxisTracker);
// We may be about to do computations based on our item's cross-size
// (e.g. using it as a constraint when measuring our content in the
// main axis, or using it with the preferred aspect ratio to obtain a main
// size). BEFORE WE DO THAT, we need let the item "pre-stretch" its cross size
// (if it's got 'align-self:stretch'), for a certain case where the spec says
// the stretched cross size is considered "definite". That case is if we
// have a single-line (nowrap) flex container which itself has a definite
// cross-size. Otherwise, we'll wait to do stretching, since (in other
// cases) we don't know how much the item should stretch yet.
const bool isSingleLine =
StyleFlexWrap::Nowrap == aParentReflowInput.mStylePosition->mFlexWrap;
if (isSingleLine) {
// Is container's cross size "definite"?
// - If it's column-oriented, then "yes", because its cross size is its
// inline-size which is always definite from its descendants' perspective.
// - Otherwise (if it's row-oriented), then we check the actual size
// and call it definite if it's not NS_UNCONSTRAINEDSIZE.
if (aAxisTracker.IsColumnOriented() ||
aTentativeContentBoxCrossSize != NS_UNCONSTRAINEDSIZE) {
// Container's cross size is "definite", so we can resolve the item's
// stretched cross size using that.
item.ResolveStretchedCrossSize(aTentativeContentBoxCrossSize);
}
}
// Before thinking about freezing the item at its base size, we need to give
// it a chance to recalculate the base size from its cross size and aspect
// ratio (since its cross size might've *just* now become definite due to
// 'stretch' above)
item.ResolveFlexBaseSizeFromAspectRatio(childRI);
// If we're inflexible, we can just freeze to our hypothetical main-size
// up-front.
if (flexGrow == 0.0f && flexShrink == 0.0f) {
item.Freeze();
if (flexBaseSize < mainMinSize) {
item.SetWasMinClamped();
} else if (flexBaseSize > mainMaxSize) {
item.SetWasMaxClamped();
}
}
// Resolve "flex-basis:auto" and/or "min-[width|height]:auto" (which might
// require us to reflow the item to measure content height)
ResolveAutoFlexBasisAndMinSize(item, childRI, aAxisTracker);
}
// Static helper-functions for ResolveAutoFlexBasisAndMinSize():
// -------------------------------------------------------------
// Partially resolves "min-[width|height]:auto" and returns the resulting value.
// By "partially", I mean we don't consider the min-content size (but we do
// consider the main-size and main max-size properties, and the preferred aspect
// ratio). The caller is responsible for computing & considering the min-content
// size in combination with the partially-resolved value that this function
// returns.
//
// Basically, this function gets the specified size suggestion; if not, the
// transferred size suggestion; if both sizes do not exist, return nscoord_MAX.
//
// Spec reference: https://drafts.csswg.org/css-flexbox-1/#min-size-auto
static nscoord PartiallyResolveAutoMinSize(
const FlexItem& aFlexItem, const ReflowInput& aItemReflowInput,
const FlexboxAxisTracker& aAxisTracker) {
MOZ_ASSERT(aFlexItem.NeedsMinSizeAutoResolution(),
"only call for FlexItems that need min-size auto resolution");
const auto itemWM = aFlexItem.GetWritingMode();
const auto cbWM = aAxisTracker.GetWritingMode();
const auto& mainStyleSize =
aItemReflowInput.mStylePosition->Size(aAxisTracker.MainAxis(), cbWM);
const auto& maxMainStyleSize =
aItemReflowInput.mStylePosition->MaxSize(aAxisTracker.MainAxis(), cbWM);
const auto boxSizingAdjust =
aItemReflowInput.mStylePosition->mBoxSizing == StyleBoxSizing::Border
? aFlexItem.BorderPadding().Size(cbWM)
: LogicalSize(cbWM);
// If this flex item is a compressible replaced element list in CSS Sizing 3
// §5.2.2, CSS Sizing 3 §5.2.1c requires us to resolve the percentage part of
// the preferred main size property against zero, yielding a definite
// specified size suggestion. Here we can use a zero percentage basis to
// fulfill this requirement.
const auto percentBasis =
aFlexItem.Frame()->IsPercentageResolvedAgainstZero(mainStyleSize,
maxMainStyleSize)
? LogicalSize(cbWM, 0, 0)
: aItemReflowInput.mContainingBlockSize.ConvertTo(cbWM, itemWM);
// Compute the specified size suggestion, which is the main-size property if
// it's definite.
nscoord specifiedSizeSuggestion = nscoord_MAX;
if (aAxisTracker.IsRowOriented()) {
if (mainStyleSize.IsLengthPercentage()) {
// NOTE: We ignore extremum inline-size. This is OK because the caller is
// responsible for computing the min-content inline-size and min()'ing it
// with the value we return.
specifiedSizeSuggestion = aFlexItem.Frame()->ComputeISizeValue(
cbWM, percentBasis, boxSizingAdjust,
mainStyleSize.AsLengthPercentage());
}
} else {
if (!nsLayoutUtils::IsAutoBSize(mainStyleSize, percentBasis.BSize(cbWM))) {
// NOTE: We ignore auto and extremum block-size. This is OK because the
// caller is responsible for computing the min-content block-size and
// min()'ing it with the value we return.
specifiedSizeSuggestion = nsLayoutUtils::ComputeBSizeValue(
percentBasis.BSize(cbWM), boxSizingAdjust.BSize(cbWM),
mainStyleSize.AsLengthPercentage());
}
}
if (specifiedSizeSuggestion != nscoord_MAX) {
// We have the specified size suggestion. Return it now since we don't need
// to consider transferred size suggestion.
FLEX_LOGV(" Specified size suggestion: %d", specifiedSizeSuggestion);
return specifiedSizeSuggestion;
}
// Compute the transferred size suggestion, which is the cross size converted
// through the aspect ratio (if the item is replaced, and it has an aspect
// ratio and a definite cross size).
if (const auto& aspectRatio = aFlexItem.GetAspectRatio();
aFlexItem.Frame()->IsFrameOfType(nsIFrame::eReplaced) && aspectRatio &&
aFlexItem.IsCrossSizeDefinite(aItemReflowInput)) {
// We have a usable aspect ratio. (not going to divide by 0)
nscoord transferredSizeSuggestion = aspectRatio.ComputeRatioDependentSize(
aFlexItem.MainAxis(), cbWM, aFlexItem.CrossSize(), boxSizingAdjust);
// Clamp the transferred size suggestion by any definite min and max
// cross size converted through the aspect ratio.
transferredSizeSuggestion = aFlexItem.ClampMainSizeViaCrossAxisConstraints(
transferredSizeSuggestion, aItemReflowInput);
FLEX_LOGV(" Transferred size suggestion: %d", transferredSizeSuggestion);
return transferredSizeSuggestion;
}
return nscoord_MAX;
}
// Note: If & when we handle "min-height: min-content" for flex items,
// we may want to resolve that in this function, too.
void nsFlexContainerFrame::ResolveAutoFlexBasisAndMinSize(
FlexItem& aFlexItem, const ReflowInput& aItemReflowInput,
const FlexboxAxisTracker& aAxisTracker) {
// (Note: We can guarantee that the flex-basis will have already been
// resolved if the main axis is the same as the item's inline
// axis. Inline-axis values should always be resolvable without reflow.)
const bool isMainSizeAuto =
(!aFlexItem.IsInlineAxisMainAxis() &&
NS_UNCONSTRAINEDSIZE == aFlexItem.FlexBaseSize());
const bool isMainMinSizeAuto = aFlexItem.NeedsMinSizeAutoResolution();
if (!isMainSizeAuto && !isMainMinSizeAuto) {
// Nothing to do; this function is only needed for flex items
// with a used flex-basis of "auto" or a min-main-size of "auto".
return;
}
FLEX_LOGV("Resolving auto main size or auto min main size for flex item %p",
aFlexItem.Frame());
nscoord resolvedMinSize; // (only set/used if isMainMinSizeAuto==true)
bool minSizeNeedsToMeasureContent = false; // assume the best
if (isMainMinSizeAuto) {
// Resolve the min-size, except for considering the min-content size.
// (We'll consider that later, if we need to.)
resolvedMinSize =
PartiallyResolveAutoMinSize(aFlexItem, aItemReflowInput, aAxisTracker);
if (resolvedMinSize > 0) {
// If resolvedMinSize were already at 0, we could skip calculating content
// size suggestion because it can't go any lower.
minSizeNeedsToMeasureContent = true;
}
}
const bool flexBasisNeedsToMeasureContent = isMainSizeAuto;
// Measure content, if needed (w/ intrinsic-width method or a reflow)
if (minSizeNeedsToMeasureContent || flexBasisNeedsToMeasureContent) {
// Compute the content size suggestion, which is the min-content size in the
// main axis.
nscoord contentSizeSuggestion = nscoord_MAX;
if (aFlexItem.IsInlineAxisMainAxis()) {
if (minSizeNeedsToMeasureContent) {
// Compute the flex item's content size suggestion, which is the
// 'min-content' size on the main axis.
// https://drafts.csswg.org/css-flexbox-1/#content-size-suggestion
const auto cbWM = aAxisTracker.GetWritingMode();
const auto itemWM = aFlexItem.GetWritingMode();
const nscoord availISize = 0; // for min-content size
StyleSizeOverrides sizeOverrides;
sizeOverrides.mStyleISize.emplace(StyleSize::Auto());
const auto sizeInItemWM = aFlexItem.Frame()->ComputeSize(
aItemReflowInput.mRenderingContext, itemWM,
aItemReflowInput.mContainingBlockSize, availISize,
aItemReflowInput.ComputedLogicalMargin(itemWM).Size(itemWM),
aItemReflowInput.ComputedLogicalBorderPadding(itemWM).Size(itemWM),
sizeOverrides, {ComputeSizeFlag::ShrinkWrap});
contentSizeSuggestion = aAxisTracker.MainComponent(
sizeInItemWM.mLogicalSize.ConvertTo(cbWM, itemWM));
}
NS_ASSERTION(!flexBasisNeedsToMeasureContent,
"flex-basis:auto should have been resolved in the "
"reflow input, for horizontal flexbox. It shouldn't need "
"special handling here");
} else {
// If this item is flexible (in its block axis)...
// OR if we're measuring its 'auto' min-BSize, with its main-size (in its
// block axis) being something non-"auto"...
// THEN: we assume that the computed BSize that we're reflowing with now
// could be different from the one we'll use for this flex item's
// "actual" reflow later on. In that case, we need to be sure the flex
// item treats this as a block-axis resize (regardless of whether there
// are actually any ancestors being resized in that axis).
// (Note: We don't have to do this for the inline axis, because
// InitResizeFlags will always turn on mIsIResize on when it sees that
// the computed ISize is different from current ISize, and that's all we
// need.)
bool forceBResizeForMeasuringReflow =
!aFlexItem.IsFrozen() || // Is the item flexible?
!flexBasisNeedsToMeasureContent; // Are we *only* measuring it for
// 'min-block-size:auto'?
const ReflowInput& flexContainerRI = *aItemReflowInput.mParentReflowInput;
nscoord contentBSize = MeasureFlexItemContentBSize(
aFlexItem, forceBResizeForMeasuringReflow, flexContainerRI);
if (minSizeNeedsToMeasureContent) {
contentSizeSuggestion = contentBSize;
}
if (flexBasisNeedsToMeasureContent) {
aFlexItem.SetFlexBaseSizeAndMainSize(contentBSize);
}
}
if (minSizeNeedsToMeasureContent) {
// Clamp the content size suggestion by any definite min and max cross
// size converted through the aspect ratio.
if (aFlexItem.HasAspectRatio()) {
contentSizeSuggestion = aFlexItem.ClampMainSizeViaCrossAxisConstraints(
contentSizeSuggestion, aItemReflowInput);
}
FLEX_LOGV(" Content size suggestion: %d", contentSizeSuggestion);
resolvedMinSize = std::min(resolvedMinSize, contentSizeSuggestion);
// Clamp the resolved min main size by the max main size if it's definite.
if (aFlexItem.MainMaxSize() != NS_UNCONSTRAINEDSIZE) {
resolvedMinSize = std::min(resolvedMinSize, aFlexItem.MainMaxSize());
} else if (MOZ_UNLIKELY(resolvedMinSize > nscoord_MAX)) {
NS_WARNING("Bogus resolved auto min main size!");
// Our resolved min-size is bogus, probably due to some huge sizes in
// the content. Clamp it to the valid nscoord range, so that we can at
// least depend on it being <= the max-size (which is also the
// nscoord_MAX sentinel value if we reach this point).
resolvedMinSize = nscoord_MAX;
}
FLEX_LOGV(" Resolved auto min main size: %d", resolvedMinSize);
}
}
if (isMainMinSizeAuto) {
aFlexItem.UpdateMainMinSize(resolvedMinSize);
}
}
/**
* A cached result for a flex item's block-axis measuring reflow. This cache
* prevents us from doing exponential reflows in cases of deeply nested flex
* and scroll frames.
*
* We store the cached value in the flex item's frame property table, for
* simplicity.
*
* Right now, we cache the following as a "key", from the item's ReflowInput:
* - its ComputedSize
* - its min/max block size (in case its ComputedBSize is unconstrained)
* - its AvailableBSize
* ...and we cache the following as the "value", from the item's ReflowOutput:
* - its final content-box BSize
*
* The assumption here is that a given flex item measurement from our "value"
* won't change unless one of the pieces of the "key" change, or the flex
* item's intrinsic size is marked as dirty (due to a style or DOM change).
* (The latter will cause the cached value to be discarded, in
* nsIFrame::MarkIntrinsicISizesDirty.)
*
* Note that the components of "Key" (mComputed{MinB,MaxB,}Size and
* mAvailableBSize) are sufficient to catch any changes to the flex container's
* size that the item may care about for its measuring reflow. Specifically:
* - If the item cares about the container's size (e.g. if it has a percent
* height and the container's height changes, in a horizontal-WM container)
* then that'll be detectable via the item's ReflowInput's "ComputedSize()"
* differing from the value in our Key. And the same applies for the
* inline axis.
* - If the item is fragmentable (pending bug 939897) and its measured BSize
* depends on where it gets fragmented, then that sort of change can be
* detected due to the item's ReflowInput's "AvailableBSize()" differing
* from the value in our Key.
*
* One particular case to consider (& need to be sure not to break when
* changing this class): the flex item's computed BSize may change between
* measuring reflows due to how the mIsFlexContainerMeasuringBSize flag affects
* size computation (see bug 1336708). This is one reason we need to use the
* computed BSize as part of the key.
*/
class nsFlexContainerFrame::CachedBAxisMeasurement {
struct Key {
const LogicalSize mComputedSize;
const nscoord mComputedMinBSize;
const nscoord mComputedMaxBSize;
const nscoord mAvailableBSize;
explicit Key(const ReflowInput& aRI)
: mComputedSize(aRI.ComputedSize()),
mComputedMinBSize(aRI.ComputedMinBSize()),
mComputedMaxBSize(aRI.ComputedMaxBSize()),
mAvailableBSize(aRI.AvailableBSize()) {}
bool operator==(const Key& aOther) const {
return mComputedSize == aOther.mComputedSize &&
mComputedMinBSize == aOther.mComputedMinBSize &&
mComputedMaxBSize == aOther.mComputedMaxBSize &&
mAvailableBSize == aOther.mAvailableBSize;
}
};
const Key mKey;
// This could/should be const, but it's non-const for now just because it's
// assigned via a series of steps in the constructor body:
nscoord mBSize;
public:
CachedBAxisMeasurement(const ReflowInput& aReflowInput,
const ReflowOutput& aReflowOutput)
: mKey(aReflowInput) {
// To get content-box bsize, we have to subtract off border & padding
// (and floor at 0 in case the border/padding are too large):
WritingMode itemWM = aReflowInput.GetWritingMode();
nscoord borderBoxBSize = aReflowOutput.BSize(itemWM);
mBSize =
borderBoxBSize -
aReflowInput.ComputedLogicalBorderPadding(itemWM).BStartEnd(itemWM);
mBSize = std::max(0, mBSize);
}
/**
* Returns true if this cached flex item measurement is valid for (i.e. can
* be expected to match the output of) a measuring reflow whose input
* parameters are given via aReflowInput.
*/
bool IsValidFor(const ReflowInput& aReflowInput) const {
return mKey == Key(aReflowInput);
}
nscoord BSize() const { return mBSize; }
};
/**
* A cached copy of various metrics from a flex item's most recent final reflow.
* It can be used to determine whether we can optimize away the flex item's
* final reflow, when we perform an incremental reflow of its flex container.
*/
class CachedFinalReflowMetrics final {
public:
CachedFinalReflowMetrics(const ReflowInput& aReflowInput,
const ReflowOutput& aReflowOutput)
: CachedFinalReflowMetrics(aReflowInput.GetWritingMode(), aReflowInput,
aReflowOutput) {}
CachedFinalReflowMetrics(const FlexItem& aItem, const LogicalSize& aSize)
: mBorderPadding(aItem.BorderPadding().ConvertTo(
aItem.GetWritingMode(), aItem.ContainingBlockWM())),
mSize(aSize),
mTreatBSizeAsIndefinite(aItem.TreatBSizeAsIndefinite()) {}
const LogicalSize& Size() const { return mSize; }
const LogicalMargin& BorderPadding() const { return mBorderPadding; }
bool TreatBSizeAsIndefinite() const { return mTreatBSizeAsIndefinite; }
private:
// A convenience constructor with a WritingMode argument.
CachedFinalReflowMetrics(WritingMode aWM, const ReflowInput& aReflowInput,
const ReflowOutput& aReflowOutput)
: mBorderPadding(aReflowInput.ComputedLogicalBorderPadding(aWM)),
mSize(aReflowOutput.Size(aWM) - mBorderPadding.Size(aWM)),
mTreatBSizeAsIndefinite(aReflowInput.mFlags.mTreatBSizeAsIndefinite) {}
// The flex item's border and padding, in its own writing-mode, that it used
// used during its most recent "final reflow".
LogicalMargin mBorderPadding;
// The flex item's content-box size, in its own writing-mode, that it used
// during its most recent "final reflow".
LogicalSize mSize;
// True if the flex item's BSize was considered "indefinite" in its most
// recent "final reflow". (For a flex item "final reflow", this is fully
// determined by the mTreatBSizeAsIndefinite flag in ReflowInput. See the
// flag's documentation for more information.)
bool mTreatBSizeAsIndefinite;
};
/**
* When we instantiate/update a CachedFlexItemData, this enum must be used to
* indicate the sort of reflow whose results we're capturing. This impacts
* what we cache & how we use the cached information.
*/
enum class FlexItemReflowType {
// A reflow to measure the block-axis size of a flex item (as an input to the
// flex layout algorithm).
Measuring,
// A reflow with the flex item's "final" size at the end of the flex layout
// algorithm.
Final,
};
/**
* This class stores information about the conditions and results for the most
* recent ReflowChild call that we made on a given flex item. This information
* helps us reason about whether we can assume that a subsequent ReflowChild()
* invocation is unnecessary & skippable.
*/
class nsFlexContainerFrame::CachedFlexItemData {
public:
CachedFlexItemData(const ReflowInput& aReflowInput,
const ReflowOutput& aReflowOutput,
FlexItemReflowType aType) {
Update(aReflowInput, aReflowOutput, aType);
}
// This method is intended to be called after we perform either a "measuring
// reflow" or a "final reflow" for a given flex item.
void Update(const ReflowInput& aReflowInput,
const ReflowOutput& aReflowOutput, FlexItemReflowType aType) {
if (aType == FlexItemReflowType::Measuring) {
mBAxisMeasurement.reset();
mBAxisMeasurement.emplace(aReflowInput, aReflowOutput);
// Clear any cached "last final reflow metrics", too, because now the most
// recent reflow was *not* a "final reflow".
mFinalReflowMetrics.reset();
return;
}
MOZ_ASSERT(aType == FlexItemReflowType::Final);
mFinalReflowMetrics.reset();
mFinalReflowMetrics.emplace(aReflowInput, aReflowOutput);
}
// This method is intended to be called for situations where we decide to
// skip a final reflow because we've just done a measuring reflow which left
// us (and our descendants) with the correct sizes. In this scenario, we
// still want to cache the size as if we did a final reflow (because we've
// determined that the recent measuring reflow was sufficient). That way,
// our flex container can still skip a final reflow for this item in the
// future as long as conditions are right.
void Update(const FlexItem& aItem, const LogicalSize& aSize) {
MOZ_ASSERT(!mFinalReflowMetrics,
"This version of the method is only intended to be called when "
"the most recent reflow was a 'measuring reflow'; and that "
"should have cleared out mFinalReflowMetrics");
mFinalReflowMetrics.reset(); // Just in case this assert^ fails.
mFinalReflowMetrics.emplace(aItem, aSize);
}
// If the flex container needs a measuring reflow for the flex item, then the
// resulting block-axis measurements can be cached here. If no measurement
// has been needed so far, then this member will be Nothing().
Maybe<CachedBAxisMeasurement> mBAxisMeasurement;
// The metrics that the corresponding flex item used in its most recent
// "final reflow". (Note: the assumption here is that this reflow was this
// item's most recent reflow of any type. If the item ends up undergoing a
// subsequent measuring reflow, then this value needs to be cleared, because
// at that point it's no longer an accurate way of reasoning about the
// current state of the frame tree.)
Maybe<CachedFinalReflowMetrics> mFinalReflowMetrics;
// Instances of this class are stored under this frame property, on
// frames that are flex items:
NS_DECLARE_FRAME_PROPERTY_DELETABLE(Prop, CachedFlexItemData)
};
void nsFlexContainerFrame::MarkCachedFlexMeasurementsDirty(
nsIFrame* aItemFrame) {
MOZ_ASSERT(aItemFrame->IsFlexItem());
if (auto* cache = aItemFrame->GetProperty(CachedFlexItemData::Prop())) {
cache->mBAxisMeasurement.reset();
cache->mFinalReflowMetrics.reset();
}
}
const CachedBAxisMeasurement& nsFlexContainerFrame::MeasureBSizeForFlexItem(
FlexItem& aItem, ReflowInput& aChildReflowInput) {
auto* cachedData = aItem.Frame()->GetProperty(CachedFlexItemData::Prop());
if (cachedData && cachedData->mBAxisMeasurement) {
if (!aItem.Frame()->IsSubtreeDirty() &&
cachedData->mBAxisMeasurement->IsValidFor(aChildReflowInput)) {
FLEX_LOG("[perf] MeasureBSizeForFlexItem accepted cached value");
return *(cachedData->mBAxisMeasurement);
}
FLEX_LOG("[perf] MeasureBSizeForFlexItem rejected cached value");
} else {
FLEX_LOG("[perf] MeasureBSizeForFlexItem didn't have a cached value");
}
// CachedFlexItemData is stored in item's writing mode, so we pass
// aChildReflowInput into ReflowOutput's constructor.
ReflowOutput childReflowOutput(aChildReflowInput);
nsReflowStatus childReflowStatus;
const ReflowChildFlags flags = ReflowChildFlags::NoMoveFrame;
const WritingMode outerWM = GetWritingMode();
const LogicalPoint dummyPosition(outerWM);
const nsSize dummyContainerSize;
// We use NoMoveFrame, so the position and container size used here are
// unimportant.
ReflowChild(aItem.Frame(), PresContext(), childReflowOutput,
aChildReflowInput, outerWM, dummyPosition, dummyContainerSize,
flags, childReflowStatus);
aItem.SetHadMeasuringReflow();
// We always use unconstrained available block-size to measure flex items,
// which means they should always complete.
MOZ_ASSERT(childReflowStatus.IsComplete(),
"We gave flex item unconstrained available block-size, so it "
"should be complete");
// Tell the child we're done with its initial reflow.
// (Necessary for e.g. GetBaseline() to work below w/out asserting)
FinishReflowChild(aItem.Frame(), PresContext(), childReflowOutput,
&aChildReflowInput, outerWM, dummyPosition,
dummyContainerSize, flags);
aItem.SetAscent(childReflowOutput.BlockStartAscent());
// Update (or add) our cached measurement, so that we can hopefully skip this
// measuring reflow the next time around:
if (cachedData) {
cachedData->Update(aChildReflowInput, childReflowOutput,
FlexItemReflowType::Measuring);
} else {
cachedData = new CachedFlexItemData(aChildReflowInput, childReflowOutput,
FlexItemReflowType::Measuring);
aItem.Frame()->SetProperty(CachedFlexItemData::Prop(), cachedData);
}
return *(cachedData->mBAxisMeasurement);
}
/* virtual */
void nsFlexContainerFrame::MarkIntrinsicISizesDirty() {
mCachedMinISize = NS_INTRINSIC_ISIZE_UNKNOWN;
mCachedPrefISize = NS_INTRINSIC_ISIZE_UNKNOWN;
nsContainerFrame::MarkIntrinsicISizesDirty();
}
nscoord nsFlexContainerFrame::MeasureFlexItemContentBSize(
FlexItem& aFlexItem, bool aForceBResizeForMeasuringReflow,
const ReflowInput& aParentReflowInput) {
FLEX_LOG("Measuring flex item's content block-size");
// Set up a reflow input for measuring the flex item's content block-size:
WritingMode wm = aFlexItem.Frame()->GetWritingMode();
LogicalSize availSize = aParentReflowInput.ComputedSize(wm);
availSize.BSize(wm) = NS_UNCONSTRAINEDSIZE;
StyleSizeOverrides sizeOverrides;
if (aFlexItem.IsStretched()) {
sizeOverrides.mStyleISize.emplace(aFlexItem.StyleCrossSize());
// Suppress any AspectRatio that we might have to prevent ComputeSize() from
// transferring our inline-size override through the aspect-ratio to set the
// block-size, because that would prevent us from measuring the content
// block-size.
sizeOverrides.mAspectRatio.emplace(AspectRatio());
FLEX_LOGV(" Cross size override: %d", aFlexItem.CrossSize());
}
sizeOverrides.mStyleBSize.emplace(StyleSize::Auto());
ReflowInput childRIForMeasuringBSize(
PresContext(), aParentReflowInput, aFlexItem.Frame(), availSize,
Nothing(), ReflowInput::InitFlag::CallerWillInit, sizeOverrides);
childRIForMeasuringBSize.Init(PresContext());
// When measuring flex item's content block-size, disregard the item's
// min-block-size and max-block-size by resetting both to to their
// unconstraining (extreme) values. The flexbox layout algorithm does still
// explicitly clamp both sizes when resolving the target main size.
childRIForMeasuringBSize.SetComputedMinBSize(0);
childRIForMeasuringBSize.SetComputedMaxBSize(NS_UNCONSTRAINEDSIZE);
if (aForceBResizeForMeasuringReflow) {
childRIForMeasuringBSize.SetBResize(true);
// Not 100% sure this is needed, but be conservative for now:
childRIForMeasuringBSize.mFlags.mIsBResizeForPercentages = true;
}
const CachedBAxisMeasurement& measurement =
MeasureBSizeForFlexItem(aFlexItem, childRIForMeasuringBSize);
return measurement.BSize();
}
FlexItem::FlexItem(ReflowInput& aFlexItemReflowInput, float aFlexGrow,
float aFlexShrink, nscoord aFlexBaseSize,
nscoord aMainMinSize, nscoord aMainMaxSize,
nscoord aTentativeCrossSize, nscoord aCrossMinSize,
nscoord aCrossMaxSize,
const FlexboxAxisTracker& aAxisTracker)
: mFrame(aFlexItemReflowInput.mFrame),
mFlexGrow(aFlexGrow),
mFlexShrink(aFlexShrink),
mAspectRatio(mFrame->GetAspectRatio()),
mWM(aFlexItemReflowInput.GetWritingMode()),
mCBWM(aAxisTracker.GetWritingMode()),
mMainAxis(aAxisTracker.MainAxis()),
mBorderPadding(aFlexItemReflowInput.ComputedLogicalBorderPadding(mCBWM)),
mMargin(aFlexItemReflowInput.ComputedLogicalMargin(mCBWM)),
mMainMinSize(aMainMinSize),
mMainMaxSize(aMainMaxSize),
mCrossMinSize(aCrossMinSize),
mCrossMaxSize(aCrossMaxSize),
mCrossSize(aTentativeCrossSize),
mIsInlineAxisMainAxis(aAxisTracker.IsInlineAxisMainAxis(mWM)),
mNeedsMinSizeAutoResolution(IsMinSizeAutoResolutionNeeded())
// mAlignSelf, mHasAnyAutoMargin see below
{
MOZ_ASSERT(mFrame, "expecting a non-null child frame");
MOZ_ASSERT(!mFrame->IsPlaceholderFrame(),
"placeholder frames should not be treated as flex items");
MOZ_ASSERT(!mFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW),
"out-of-flow frames should not be treated as flex items");
MOZ_ASSERT(mIsInlineAxisMainAxis ==
nsFlexContainerFrame::IsItemInlineAxisMainAxis(mFrame),
"public API should be consistent with internal state (about "
"whether flex item's inline axis is flex container's main axis)");
const ReflowInput* containerRS = aFlexItemReflowInput.mParentReflowInput;
if (IsLegacyBox(containerRS->mFrame)) {
// For -webkit-{inline-}box and -moz-{inline-}box, we need to:
// (1) Use prefixed "box-align" instead of "align-items" to determine the
// container's cross-axis alignment behavior.
// (2) Suppress the ability for flex items to override that with their own
// cross-axis alignment. (The legacy box model doesn't support this.)
// So, each FlexItem simply copies the container's converted "align-items"
// value and disregards their own "align-self" property.
const nsStyleXUL* containerStyleXUL = containerRS->mFrame->StyleXUL();
mAlignSelf = {ConvertLegacyStyleToAlignItems(containerStyleXUL)};
mAlignSelfFlags = {0};
} else {
mAlignSelf = aFlexItemReflowInput.mStylePosition->UsedAlignSelf(
containerRS->mFrame->Style());
if (MOZ_LIKELY(mAlignSelf._0 == StyleAlignFlags::NORMAL)) {
mAlignSelf = {StyleAlignFlags::STRETCH};
}
// Store and strip off the <overflow-position> bits
mAlignSelfFlags = mAlignSelf._0 & StyleAlignFlags::FLAG_BITS;
mAlignSelf._0 &= ~StyleAlignFlags::FLAG_BITS;
}
// Our main-size is considered definite if any of these are true:
// (a) main axis is the item's inline axis.
// (b) flex container has definite main size.
// (c) flex item has a definite flex basis.
//
// Hence, we need to take care to treat the final main-size as *indefinite*
// if none of these conditions are satisfied.
if (mIsInlineAxisMainAxis) {
// The item's block-axis is the flex container's cross axis. We don't need
// any special handling to treat cross sizes as indefinite, because the
// cases where we stomp on the cross size with a definite value are all...
// - situations where the spec requires us to treat the cross size as
// definite; specifically, `align-self:stretch` whose cross size is
// definite.
// - situations where definiteness doesn't matter (e.g. for an element with
// an aspect ratio, which for now are all leaf nodes and hence
// can't have any percent-height descendants that would care about the
// definiteness of its size. (Once bug 1528375 is fixed, we might need to
// be more careful about definite vs. indefinite sizing on flex items with
// aspect ratios.)
mTreatBSizeAsIndefinite = false;
} else {
// The item's block-axis is the flex container's main axis. So, the flex
// item's main size is its BSize, and is considered definite under certain
// conditions laid out for definite flex-item main-sizes in the spec.
if (aAxisTracker.IsRowOriented() ||
(containerRS->ComputedBSize() != NS_UNCONSTRAINEDSIZE &&
!containerRS->mFlags.mTreatBSizeAsIndefinite)) {
// The flex *container* has a definite main-size (either by being
// row-oriented [and using its own inline size which is by definition
// definite, or by being column-oriented and having a definite
// block-size). The spec says this means all of the flex items'
// post-flexing main sizes should *also* be treated as definite.
mTreatBSizeAsIndefinite = false;
} else if (aFlexBaseSize != NS_UNCONSTRAINEDSIZE) {
// The flex item has a definite flex basis, which we'll treat as making
// its main-size definite.
mTreatBSizeAsIndefinite = false;
} else {
// Otherwise, we have to treat the item's BSize as indefinite.
mTreatBSizeAsIndefinite = true;
}
}
SetFlexBaseSizeAndMainSize(aFlexBaseSize);
const nsStyleMargin* styleMargin = aFlexItemReflowInput.mStyleMargin;
mHasAnyAutoMargin = styleMargin->HasInlineAxisAuto(mCBWM) ||
styleMargin->HasBlockAxisAuto(mCBWM);
// Assert that any "auto" margin components are set to 0.
// (We'll resolve them later; until then, we want to treat them as 0-sized.)
#ifdef DEBUG
{
for (const auto side : AllLogicalSides()) {
if (styleMargin->mMargin.Get(mCBWM, side).IsAuto()) {
MOZ_ASSERT(GetMarginComponentForSide(side) == 0,
"Someone else tried to resolve our auto margin");
}
}
}
#endif // DEBUG
// Map align-self 'baseline' value to 'start' when baseline alignment
// is not possible because the FlexItem's block axis is orthogonal to
// the cross axis of the container. If that's the case, we just directly
// convert our align-self value here, so that we don't have to handle this
// with special cases elsewhere.
// We are treating this case as one where it is appropriate to use the
// fallback values defined at https://www.w3.org/TR/css-align/#baseline-values
if (!IsBlockAxisCrossAxis()) {
if (mAlignSelf._0 == StyleAlignFlags::BASELINE) {
mAlignSelf = {StyleAlignFlags::FLEX_START};
} else if (mAlignSelf._0 == StyleAlignFlags::LAST_BASELINE) {
mAlignSelf = {StyleAlignFlags::FLEX_END};
}
}
}
// Simplified constructor for creating a special "strut" FlexItem, for a child
// with visibility:collapse. The strut has 0 main-size, and it only exists to
// impose a minimum cross size on whichever FlexLine it ends up in.
FlexItem::FlexItem(nsIFrame* aChildFrame, nscoord aCrossSize,
WritingMode aContainerWM,
const FlexboxAxisTracker& aAxisTracker)
: mFrame(aChildFrame),
mWM(aChildFrame->GetWritingMode()),
mCBWM(aContainerWM),
mMainAxis(aAxisTracker.MainAxis()),
mBorderPadding(mCBWM),
mMargin(mCBWM),
mCrossSize(aCrossSize),
// Struts don't do layout, so its WM doesn't matter at this point. So, we
// just share container's WM for simplicity:
mIsFrozen(true),
mIsStrut(true), // (this is the constructor for making struts, after all)
mAlignSelf({StyleAlignFlags::FLEX_START}) {
MOZ_ASSERT(mFrame, "expecting a non-null child frame");
MOZ_ASSERT(mFrame->StyleVisibility()->IsCollapse(),
"Should only make struts for children with 'visibility:collapse'");
MOZ_ASSERT(!mFrame->IsPlaceholderFrame(),
"placeholder frames should not be treated as flex items");
MOZ_ASSERT(!mFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW),
"out-of-flow frames should not be treated as flex items");
}
bool FlexItem::IsMinSizeAutoResolutionNeeded() const {
// We'll need special behavior for "min-[width|height]:auto" (whichever is in
// the flex container's main axis) iff:
// (a) its computed value is "auto", and
// (b) the item is *not* a scroll container. (A scroll container's automatic
// minimum size is zero.)
// https://drafts.csswg.org/css-flexbox-1/#min-size-auto
const auto& mainMinSize =
Frame()->StylePosition()->MinSize(MainAxis(), ContainingBlockWM());
return IsAutoOrEnumOnBSize(mainMinSize, IsInlineAxisMainAxis()) &&
!Frame()->StyleDisplay()->IsScrollableOverflow();
}
nscoord FlexItem::BaselineOffsetFromOuterCrossEdge(
mozilla::Side aStartSide, bool aUseFirstLineBaseline) const {
// NOTE:
// * We only use baselines for aligning in the flex container's cross axis.
// * Baselines are a measurement in the item's block axis.
// ...so we only expect to get here if the item's block axis is parallel (or
// antiparallel) to the container's cross axis. (Otherwise, the FlexItem
// constructor should've resolved mAlignSelf with a fallback value, which
// would prevent this function from being called.)
MOZ_ASSERT(IsBlockAxisCrossAxis(),
"Only expecting to be doing baseline computations when the "
"cross axis is the block axis");
mozilla::Side itemBlockStartSide = mWM.PhysicalSide(eLogicalSideBStart);
nscoord marginBStartToBaseline = ResolvedAscent(aUseFirstLineBaseline) +
PhysicalMargin().Side(itemBlockStartSide);
return (aStartSide == itemBlockStartSide)
? marginBStartToBaseline
: OuterCrossSize() - marginBStartToBaseline;
}
bool FlexItem::IsCrossSizeAuto() const {
const nsStylePosition* stylePos =
nsLayoutUtils::GetStyleFrame(mFrame)->StylePosition();
// Check whichever component is in the flex container's cross axis.
// (IsInlineAxisCrossAxis() tells us whether that's our ISize or BSize, in
// terms of our own WritingMode, mWM.)
return IsInlineAxisCrossAxis() ? stylePos->ISize(mWM).IsAuto()
: stylePos->BSize(mWM).IsAuto();
}
bool FlexItem::IsCrossSizeDefinite(const ReflowInput& aItemReflowInput) const {
if (IsStretched()) {
// Definite cross-size, imposed via 'align-self:stretch' & flex container.
return true;
}
const nsStylePosition* pos = aItemReflowInput.mStylePosition;
const auto itemWM = GetWritingMode();
// The logic here should be similar to the logic for isAutoISize/isAutoBSize
// in nsContainerFrame::ComputeSizeWithIntrinsicDimensions().
if (IsInlineAxisCrossAxis()) {
return !pos->ISize(itemWM).IsAuto();
}
nscoord cbBSize = aItemReflowInput.mContainingBlockSize.BSize(itemWM);
return !nsLayoutUtils::IsAutoBSize(pos->BSize(itemWM), cbBSize);
}
void FlexItem::ResolveFlexBaseSizeFromAspectRatio(
const ReflowInput& aItemReflowInput) {
// This implements the Flex Layout Algorithm Step 3B:
// https://drafts.csswg.org/css-flexbox-1/#algo-main-item
// If the flex item has ...
// - an aspect ratio,
// - a [used] flex-basis of 'content', and
// - a definite cross size
// then the flex base size is calculated from its inner cross size and the
// flex item's preferred aspect ratio.
if (HasAspectRatio() &&
nsFlexContainerFrame::IsUsedFlexBasisContent(
aItemReflowInput.mStylePosition->mFlexBasis,
aItemReflowInput.mStylePosition->Size(MainAxis(), mCBWM)) &&
IsCrossSizeDefinite(aItemReflowInput)) {
const LogicalSize contentBoxSizeToBoxSizingAdjust =
aItemReflowInput.mStylePosition->mBoxSizing == StyleBoxSizing::Border
? BorderPadding().Size(mCBWM)
: LogicalSize(mCBWM);
const nscoord mainSizeFromRatio = mAspectRatio.ComputeRatioDependentSize(
MainAxis(), mCBWM, CrossSize(), contentBoxSizeToBoxSizingAdjust);
SetFlexBaseSizeAndMainSize(mainSizeFromRatio);
}
}
uint32_t FlexItem::NumAutoMarginsInAxis(LogicalAxis aAxis) const {
uint32_t numAutoMargins = 0;
const auto& styleMargin = mFrame->StyleMargin()->mMargin;
for (const auto edge : {eLogicalEdgeStart, eLogicalEdgeEnd}) {
const auto side = MakeLogicalSide(aAxis, edge);
if (styleMargin.Get(mCBWM, side).IsAuto()) {
numAutoMargins++;
}
}
// Mostly for clarity:
MOZ_ASSERT(numAutoMargins <= 2,
"We're just looking at one item along one dimension, so we "
"should only have examined 2 margins");
return numAutoMargins;
}
bool FlexItem::CanMainSizeInfluenceCrossSize() const {
if (mIsStretched) {
// We've already had our cross-size stretched for "align-self:stretch").
// The container is imposing its cross size on us.
return false;
}
if (mIsStrut) {
// Struts (for visibility:collapse items) have a predetermined size;
// no need to measure anything.
return false;
}
if (HasAspectRatio()) {
// For flex items that have an aspect ratio (and maintain it, i.e. are
// not stretched, which we already checked above): changes to main-size
// *do* influence the cross size.
return true;
}
if (IsInlineAxisCrossAxis()) {
// If we get here, this function is really asking: "can changes to this
// item's block size have an influence on its inline size"? For blocks and
// tables, the answer is "no".
if (mFrame->IsBlockFrame() || mFrame->IsTableWrapperFrame()) {
// XXXdholbert (Maybe use an IsFrameOfType query or something more
// general to test this across all frame types? For now, I'm just
// optimizing for block and table, since those are common containers that
// can contain arbitrarily-large subtrees (and that reliably have ISize
// being unaffected by BSize, per CSS2). So optimizing away needless
// relayout is possible & especially valuable for these containers.)
return false;
}
// Other opt-outs can go here, as they're identified as being useful
// (particularly for containers where an extra reflow is expensive). But in
// general, we have to assume that a flexed BSize *could* influence the
// ISize. Some examples where this can definitely happen:
// * Intrinsically-sized multicol with fixed-ISize columns, which adds
// columns (i.e. grows in inline axis) depending on its block size.
// * Intrinsically-sized multi-line column-oriented flex container, which
// adds flex lines (i.e. grows in inline axis) depending on its block size.
}
// Default assumption, if we haven't proven otherwise: the resolved main size
// *can* change the cross size.
return true;
}
nscoord FlexItem::ClampMainSizeViaCrossAxisConstraints(
nscoord aMainSize, const ReflowInput& aItemReflowInput) const {
MOZ_ASSERT(HasAspectRatio(), "Caller should've checked the ratio is valid!");
const LogicalSize contentBoxSizeToBoxSizingAdjust =
aItemReflowInput.mStylePosition->mBoxSizing == StyleBoxSizing::Border
? BorderPadding().Size(mCBWM)
: LogicalSize(mCBWM);
const nscoord mainMinSizeFromRatio = mAspectRatio.ComputeRatioDependentSize(
MainAxis(), mCBWM, CrossMinSize(), contentBoxSizeToBoxSizingAdjust);
nscoord clampedMainSize = std::max(aMainSize, mainMinSizeFromRatio);
if (CrossMaxSize() != NS_UNCONSTRAINEDSIZE) {
const nscoord mainMaxSizeFromRatio = mAspectRatio.ComputeRatioDependentSize(
MainAxis(), mCBWM, CrossMaxSize(), contentBoxSizeToBoxSizingAdjust);
clampedMainSize = std::min(clampedMainSize, mainMaxSizeFromRatio);
}
return clampedMainSize;
}
/**
* Returns true if aFrame or any of its children have the
* NS_FRAME_CONTAINS_RELATIVE_BSIZE flag set -- i.e. if any of these frames (or
* their descendants) might have a relative-BSize dependency on aFrame (or its
* ancestors).
*/
static bool FrameHasRelativeBSizeDependency(nsIFrame* aFrame) {
if (aFrame->HasAnyStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE)) {
return true;
}
for (const auto& childList : aFrame->ChildLists()) {
for (nsIFrame* childFrame : childList.mList) {
if (childFrame->HasAnyStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE)) {
return true;
}
}
}
return false;
}
bool FlexItem::NeedsFinalReflow(const ReflowInput& aParentReflowInput) const {
if (!StaticPrefs::layout_flexbox_item_final_reflow_optimization_enabled()) {
FLEX_LOG(
"[perf] Flex item %p needed a final reflow due to optimization being "
"disabled via the preference",
mFrame);
return true;
}
// NOTE: We can have continuations from an earlier constrained reflow.
if (mFrame->GetPrevInFlow() || mFrame->GetNextInFlow()) {
// This is an item has continuation(s). Reflow it.
FLEX_LOG("[frag] Flex item %p needed a final reflow due to continuation(s)",
mFrame);
return true;
}
// A flex item can grow its block-size in a fragmented context if there's any
// force break within it (bug 1663079), or if it has a repeated table header
// or footer (bug 1744363). We currently always reflow it.
//
// Bug 1815294: investigate if we can design a more specific condition to
// prevent triggering O(n^2) behavior when printing a deeply-nested flex
// container.
if (aParentReflowInput.IsInFragmentedContext()) {
FLEX_LOG(
"[frag] Flex item %p needed both a measuring reflow and a final "
"reflow due to being in a fragmented context.",
mFrame);
return true;
}
// Flex item's final content-box size (in terms of its own writing-mode):
const LogicalSize finalSize = mIsInlineAxisMainAxis
? LogicalSize(mWM, mMainSize, mCrossSize)
: LogicalSize(mWM, mCrossSize, mMainSize);
if (HadMeasuringReflow()) {
// We've already reflowed this flex item once, to measure it. In that
// reflow, did its frame happen to end up with the correct final size
// that the flex container would like it to have?
if (finalSize != mFrame->ContentSize(mWM)) {
// The measuring reflow left the item with a different size than its
// final flexed size. So, we need to reflow to give it the correct size.
FLEX_LOG(
"[perf] Flex item %p needed both a measuring reflow and a final "
"reflow due to measured size disagreeing with final size",
mFrame);
return true;
}
if (FrameHasRelativeBSizeDependency(mFrame)) {
// This item has descendants with relative BSizes who may care that its
// size may now be considered "definite" in the final reflow (whereas it
// was indefinite during the measuring reflow).
FLEX_LOG(
"[perf] Flex item %p needed both a measuring reflow and a final "
"reflow due to BSize potentially becoming definite",
mFrame);
return true;
}
// If we get here, then this flex item had a measuring reflow, it left us
// with the correct size, none of its descendants care that its BSize may
// now be considered definite, and it can fit into the available block-size.
// So it doesn't need a final reflow.
//
// We now cache this size as if we had done a final reflow (because we've
// determined that the measuring reflow was effectively equivalent). This
// way, in our next time through flex layout, we may be able to skip both
// the measuring reflow *and* the final reflow (if conditions are the same
// as they are now).
if (auto* cache = mFrame->GetProperty(CachedFlexItemData::Prop())) {
cache->Update(*this, finalSize);
}
return false;
}
// This item didn't receive a measuring reflow (at least, not during this
// reflow of our flex container). We may still be able to skip reflowing it
// (i.e. return false from this function), if its subtree is clean & its most
// recent "final reflow" had it at the correct content-box size &
// definiteness.
// Let's check for each condition that would still require us to reflow:
if (mFrame->IsSubtreeDirty()) {
FLEX_LOG(
"[perf] Flex item %p needed a final reflow due to its subtree "
"being dirty",
mFrame);
return true;
}
// Cool; this item & its subtree haven't experienced any style/content
// changes that would automatically require a reflow.
// Did we cache the metrics from its most recent "final reflow"?
auto* cache = mFrame->GetProperty(CachedFlexItemData::Prop());
if (!cache || !cache->mFinalReflowMetrics) {
FLEX_LOG(
"[perf] Flex item %p needed a final reflow due to lacking a "
"cached mFinalReflowMetrics (maybe cache was cleared)",
mFrame);
return true;
}
// Does the cached size match our current size?
if (cache->mFinalReflowMetrics->Size() != finalSize) {
FLEX_LOG(
"[perf] Flex item %p needed a final reflow due to having a "
"different content box size vs. its most recent final reflow",
mFrame);
return true;
}
// Does the cached border and padding match our current ones?
//
// Note: this is just to detect cases where we have a percent padding whose
// basis has changed. Any other sort of change to BorderPadding() (e.g. a new
// specified value) should result in the frame being marked dirty via proper
// change hint (see nsStylePadding::CalcDifference()), which will force it to
// reflow.
if (cache->mFinalReflowMetrics->BorderPadding() !=
BorderPadding().ConvertTo(mWM, mCBWM)) {
FLEX_LOG(
"[perf] Flex item %p needed a final reflow due to having a "
"different border and padding vs. its most recent final reflow",
mFrame);
return true;
}
// The flex container is giving this flex item the same size that the item
// had on its most recent "final reflow". But if its definiteness changed and
// one of the descendants cares, then it would still need a reflow.
if (cache->mFinalReflowMetrics->TreatBSizeAsIndefinite() !=
mTreatBSizeAsIndefinite &&
FrameHasRelativeBSizeDependency(mFrame)) {
FLEX_LOG(
"[perf] Flex item %p needed a final reflow due to having "
"its BSize change definiteness & having a rel-BSize child",
mFrame);
return true;
}
// If we get here, we can skip the final reflow! (The item's subtree isn't
// dirty, and our current conditions are sufficiently similar to the most
// recent "final reflow" that it should have left our subtree in the correct
// state.)
FLEX_LOG("[perf] Flex item %p didn't need a final reflow", mFrame);
return false;
}
// Keeps track of our position along a particular axis (where a '0' position
// corresponds to the 'start' edge of that axis).
// This class shouldn't be instantiated directly -- rather, it should only be
// instantiated via its subclasses defined below.
class MOZ_STACK_CLASS PositionTracker {
public:
// Accessor for the current value of the position that we're tracking.
inline nscoord Position() const { return mPosition; }
inline LogicalAxis Axis() const { return mAxis; }
inline LogicalSide StartSide() {
return MakeLogicalSide(
mAxis, mIsAxisReversed ? eLogicalEdgeEnd : eLogicalEdgeStart);
}
inline LogicalSide EndSide() {
return MakeLogicalSide(
mAxis, mIsAxisReversed ? eLogicalEdgeStart : eLogicalEdgeEnd);
}
// Advances our position across the start edge of the given margin, in the
// axis we're tracking.
void EnterMargin(const LogicalMargin& aMargin) {
mPosition += aMargin.Side(StartSide(), mWM);
}
// Advances our position across the end edge of the given margin, in the axis
// we're tracking.
void ExitMargin(const LogicalMargin& aMargin) {
mPosition += aMargin.Side(EndSide(), mWM);
}
// Advances our current position from the start side of a child frame's
// border-box to the frame's upper or left edge (depending on our axis).
// (Note that this is a no-op if our axis grows in the same direction as
// the corresponding logical axis.)
void EnterChildFrame(nscoord aChildFrameSize) {
if (mIsAxisReversed) {
mPosition += aChildFrameSize;
}
}
// Advances our current position from a frame's upper or left border-box edge
// (whichever is in the axis we're tracking) to the 'end' side of the frame
// in the axis that we're tracking. (Note that this is a no-op if our axis
// is reversed with respect to the corresponding logical axis.)
void ExitChildFrame(nscoord aChildFrameSize) {
if (!mIsAxisReversed) {
mPosition += aChildFrameSize;
}
}
// Delete copy-constructor & reassignment operator, to prevent accidental
// (unnecessary) copying.
PositionTracker(const PositionTracker&) = delete;
PositionTracker& operator=(const PositionTracker&) = delete;
protected:
// Protected constructor, to be sure we're only instantiated via a subclass.
PositionTracker(WritingMode aWM, LogicalAxis aAxis, bool aIsAxisReversed)
: mWM(aWM), mAxis(aAxis), mIsAxisReversed(aIsAxisReversed) {}
// Member data:
// The position we're tracking.
nscoord mPosition = 0;
// The flex container's writing mode.
const WritingMode mWM;
// The axis along which we're moving.
const LogicalAxis mAxis = eLogicalAxisInline;
// Is the axis along which we're moving reversed (e.g. LTR vs RTL) with
// respect to the corresponding axis on the flex container's WM?
const bool mIsAxisReversed = false;
};
// Tracks our position in the main axis, when we're laying out flex items.
// The "0" position represents the main-start edge of the flex container's
// content-box.
class MOZ_STACK_CLASS MainAxisPositionTracker : public PositionTracker {
public:
MainAxisPositionTracker(const FlexboxAxisTracker& aAxisTracker,
const FlexLine* aLine,
const StyleContentDistribution& aJustifyContent,
nscoord aContentBoxMainSize);
~MainAxisPositionTracker() {
MOZ_ASSERT(mNumPackingSpacesRemaining == 0,
"miscounted the number of packing spaces");
MOZ_ASSERT(mNumAutoMarginsInMainAxis == 0,
"miscounted the number of auto margins");
}
// Advances past the gap space (if any) between two flex items
void TraverseGap(nscoord aGapSize) { mPosition += aGapSize; }
// Advances past the packing space (if any) between two flex items
void TraversePackingSpace();
// If aItem has any 'auto' margins in the main axis, this method updates the
// corresponding values in its margin.
void ResolveAutoMarginsInMainAxis(FlexItem& aItem);
private:
nscoord mPackingSpaceRemaining = 0;
uint32_t mNumAutoMarginsInMainAxis = 0;
uint32_t mNumPackingSpacesRemaining = 0;
StyleContentDistribution mJustifyContent = {StyleAlignFlags::AUTO};
};
// Utility class for managing our position along the cross axis along
// the whole flex container (at a higher level than a single line).
// The "0" position represents the cross-start edge of the flex container's
// content-box.
class MOZ_STACK_CLASS CrossAxisPositionTracker : public PositionTracker {
public:
CrossAxisPositionTracker(nsTArray<FlexLine>& aLines,
const ReflowInput& aReflowInput,
nscoord aContentBoxCrossSize,
bool aIsCrossSizeDefinite,
const FlexboxAxisTracker& aAxisTracker,
const nscoord aCrossGapSize);
// Advances past the gap (if any) between two flex lines
void TraverseGap() { mPosition += mCrossGapSize; }
// Advances past the packing space (if any) between two flex lines
void TraversePackingSpace();
// Advances past the given FlexLine
void TraverseLine(FlexLine& aLine) { mPosition += aLine.LineCrossSize(); }
// Redeclare the frame-related methods from PositionTracker with
// = delete, to be sure (at compile time) that no client code can invoke
// them. (Unlike the other PositionTracker derived classes, this class here
// deals with FlexLines, not with individual FlexItems or frames.)
void EnterMargin(const LogicalMargin& aMargin) = delete;
void ExitMargin(const LogicalMargin& aMargin) = delete;
void EnterChildFrame(nscoord aChildFrameSize) = delete;
void ExitChildFrame(nscoord aChildFrameSize) = delete;
private:
nscoord mPackingSpaceRemaining = 0;
uint32_t mNumPackingSpacesRemaining = 0;
StyleContentDistribution mAlignContent = {StyleAlignFlags::AUTO};
const nscoord mCrossGapSize;
};
// Utility class for managing our position along the cross axis, *within* a
// single flex line.
class MOZ_STACK_CLASS SingleLineCrossAxisPositionTracker
: public PositionTracker {
public:
explicit SingleLineCrossAxisPositionTracker(
const FlexboxAxisTracker& aAxisTracker);
void ResolveAutoMarginsInCrossAxis(const FlexLine& aLine, FlexItem& aItem);
void EnterAlignPackingSpace(const FlexLine& aLine, const FlexItem& aItem,
const FlexboxAxisTracker& aAxisTracker);
// Resets our position to the cross-start edge of this line.
inline void ResetPosition() { mPosition = 0; }
};
//----------------------------------------------------------------------
// Frame class boilerplate
// =======================
NS_QUERYFRAME_HEAD(nsFlexContainerFrame)
NS_QUERYFRAME_ENTRY(nsFlexContainerFrame)
NS_QUERYFRAME_TAIL_INHERITING(nsContainerFrame)
NS_IMPL_FRAMEARENA_HELPERS(nsFlexContainerFrame)
nsContainerFrame* NS_NewFlexContainerFrame(PresShell* aPresShell,
ComputedStyle* aStyle) {
return new (aPresShell)
nsFlexContainerFrame(aStyle, aPresShell->GetPresContext());
}
//----------------------------------------------------------------------
// nsFlexContainerFrame Method Implementations
// ===========================================
/* virtual */
nsFlexContainerFrame::~nsFlexContainerFrame() = default;
/* virtual */
void nsFlexContainerFrame::Init(nsIContent* aContent, nsContainerFrame* aParent,
nsIFrame* aPrevInFlow) {
nsContainerFrame::Init(aContent, aParent, aPrevInFlow);
if (HasAnyStateBits(NS_FRAME_FONT_INFLATION_CONTAINER)) {
AddStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT);
}
auto displayInside = StyleDisplay()->DisplayInside();
// If this frame is for a scrollable element, then it will actually have
// "display:block", and its *parent frame* will have the real
// flex-flavored display value. So in that case, check the parent frame to
// find out if we're legacy.
//
// TODO(emilio): Maybe ::-moz-scrolled-content and co should inherit `display`
// (or a blockified version thereof, to not hit bug 456484).
if (displayInside == StyleDisplayInside::Flow) {
MOZ_ASSERT(StyleDisplay()->mDisplay == StyleDisplay::Block);
MOZ_ASSERT(Style()->GetPseudoType() == PseudoStyleType::buttonContent ||
Style()->GetPseudoType() == PseudoStyleType::scrolledContent,
"The only way a nsFlexContainerFrame can have 'display:block' "
"should be if it's the inner part of a scrollable or button "
"element");
displayInside = GetParent()->StyleDisplay()->DisplayInside();
}
// Figure out if we should set a frame state bit to indicate that this frame
// represents a legacy -moz-{inline-}box or -webkit-{inline-}box container.
if (displayInside == StyleDisplayInside::WebkitBox) {
AddStateBits(NS_STATE_FLEX_IS_EMULATING_LEGACY_WEBKIT_BOX);
}
}
#ifdef DEBUG_FRAME_DUMP
nsresult nsFlexContainerFrame::GetFrameName(nsAString& aResult) const {
return MakeFrameName(u"FlexContainer"_ns, aResult);
}
#endif
void nsFlexContainerFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsDisplayListSet& aLists) {
nsDisplayListCollection tempLists(aBuilder);
DisplayBorderBackgroundOutline(aBuilder, tempLists);
if (GetPrevInFlow()) {
DisplayOverflowContainers(aBuilder, tempLists);
}
// Our children are all block-level, so their borders/backgrounds all go on
// the BlockBorderBackgrounds list.
nsDisplayListSet childLists(tempLists, tempLists.BlockBorderBackgrounds());
CSSOrderAwareFrameIterator iter(
this, FrameChildListID::Principal,
CSSOrderAwareFrameIterator::ChildFilter::IncludeAll,
OrderStateForIter(this), OrderingPropertyForIter(this));
const auto flags = DisplayFlagsForFlexOrGridItem();
for (; !iter.AtEnd(); iter.Next()) {
nsIFrame* childFrame = *iter;
BuildDisplayListForChild(aBuilder, childFrame, childLists, flags);
}
tempLists.MoveTo(aLists);
}
void FlexLine::FreezeItemsEarly(bool aIsUsingFlexGrow,
ComputedFlexLineInfo* aLineInfo) {
// After we've established the type of flexing we're doing (growing vs.
// shrinking), and before we try to flex any items, we freeze items that
// obviously *can't* flex.
//
// Quoting the spec:
// # Freeze, setting its target main size to its hypothetical main size...
// # - any item that has a flex factor of zero
// # - if using the flex grow factor: any item that has a flex base size
// # greater than its hypothetical main size
// # - if using the flex shrink factor: any item that has a flex base size
// # smaller than its hypothetical main size
// https://drafts.csswg.org/css-flexbox/#resolve-flexible-lengths
//
// (NOTE: At this point, item->MainSize() *is* the item's hypothetical
// main size, since SetFlexBaseSizeAndMainSize() sets it up that way, and the
// item hasn't had a chance to flex away from that yet.)
// Since this loop only operates on unfrozen flex items, we can break as
// soon as we have seen all of them.
uint32_t numUnfrozenItemsToBeSeen = NumItems() - mNumFrozenItems;
for (FlexItem& item : Items()) {
if (numUnfrozenItemsToBeSeen == 0) {
break;
}
if (!item.IsFrozen()) {
numUnfrozenItemsToBeSeen--;
bool shouldFreeze = (0.0f == item.GetFlexFactor(aIsUsingFlexGrow));
if (!shouldFreeze) {
if (aIsUsingFlexGrow) {
if (item.FlexBaseSize() > item.MainSize()) {
shouldFreeze = true;
}
} else { // using flex-shrink
if (item.FlexBaseSize() < item.MainSize()) {
shouldFreeze = true;
}
}
}
if (shouldFreeze) {
// Freeze item! (at its hypothetical main size)
item.Freeze();
if (item.FlexBaseSize() < item.MainSize()) {
item.SetWasMinClamped();
} else if (item.FlexBaseSize() > item.MainSize()) {
item.SetWasMaxClamped();
}
mNumFrozenItems++;
}
}
}
MOZ_ASSERT(numUnfrozenItemsToBeSeen == 0, "miscounted frozen items?");
}
// Based on the sign of aTotalViolation, this function freezes a subset of our
// flexible sizes, and restores the remaining ones to their initial pref sizes.
void FlexLine::FreezeOrRestoreEachFlexibleSize(const nscoord aTotalViolation,
bool aIsFinalIteration) {
enum FreezeType {
eFreezeEverything,
eFreezeMinViolations,
eFreezeMaxViolations
};
FreezeType freezeType;
if (aTotalViolation == 0) {
freezeType = eFreezeEverything;
} else if (aTotalViolation > 0) {
freezeType = eFreezeMinViolations;
} else { // aTotalViolation < 0
freezeType = eFreezeMaxViolations;
}
// Since this loop only operates on unfrozen flex items, we can break as
// soon as we have seen all of them.
uint32_t numUnfrozenItemsToBeSeen = NumItems() - mNumFrozenItems;
for (FlexItem& item : Items()) {
if (numUnfrozenItemsToBeSeen == 0) {
break;
}
if (!item.IsFrozen()) {
numUnfrozenItemsToBeSeen--;
MOZ_ASSERT(!item.HadMinViolation() || !item.HadMaxViolation(),
"Can have either min or max violation, but not both");
bool hadMinViolation = item.HadMinViolation();
bool hadMaxViolation = item.HadMaxViolation();
if (eFreezeEverything == freezeType ||
(eFreezeMinViolations == freezeType && hadMinViolation) ||
(eFreezeMaxViolations == freezeType && hadMaxViolation)) {
MOZ_ASSERT(item.MainSize() >= item.MainMinSize(),
"Freezing item at a size below its minimum");
MOZ_ASSERT(item.MainSize() <= item.MainMaxSize(),
"Freezing item at a size above its maximum");
item.Freeze();
if (hadMinViolation) {
item.SetWasMinClamped();
} else if (hadMaxViolation) {
item.SetWasMaxClamped();
}
mNumFrozenItems++;
} else if (MOZ_UNLIKELY(aIsFinalIteration)) {
// XXXdholbert If & when bug 765861 is fixed, we should upgrade this
// assertion to be fatal except in documents with enormous lengths.
NS_ERROR(
"Final iteration still has unfrozen items, this shouldn't"
" happen unless there was nscoord under/overflow.");
item.Freeze();
mNumFrozenItems++;
} // else, we'll reset this item's main size to its flex base size on the
// next iteration of this algorithm.
if (!item.IsFrozen()) {
// Clear this item's violation(s), now that we've dealt with them
item.ClearViolationFlags();
}
}
}
MOZ_ASSERT(numUnfrozenItemsToBeSeen == 0, "miscounted frozen items?");
}
void FlexLine::ResolveFlexibleLengths(nscoord aFlexContainerMainSize,
ComputedFlexLineInfo* aLineInfo) {
// In this function, we use 64-bit coord type to avoid integer overflow in
// case several of the individual items have huge hypothetical main sizes,
// which can happen with percent-width table-layout:fixed descendants. Here we
// promote the container's main size to 64-bit to make the arithmetic
// convenient.
AuCoord64 flexContainerMainSize(aFlexContainerMainSize);
// Before we start resolving sizes: if we have an aLineInfo structure to fill
// out, we inform it of each item's base size, and we initialize the "delta"
// for each item to 0. (And if the flex algorithm wants to grow or shrink the
// item, we'll update this delta further down.)
if (aLineInfo) {
uint32_t itemIndex = 0;
for (FlexItem& item : Items()) {
aLineInfo->mItems[itemIndex].mMainBaseSize = item.FlexBaseSize();
aLineInfo->mItems[itemIndex].mMainDeltaSize = 0;
++itemIndex;
}
}
// Determine whether we're going to be growing or shrinking items.
const bool isUsingFlexGrow =
(mTotalOuterHypotheticalMainSize < flexContainerMainSize);
if (aLineInfo) {
aLineInfo->mGrowthState =
isUsingFlexGrow ? mozilla::dom::FlexLineGrowthState::Growing
: mozilla::dom::FlexLineGrowthState::Shrinking;
}
// Do an "early freeze" for flex items that obviously can't flex in the
// direction we've chosen:
FreezeItemsEarly(isUsingFlexGrow, aLineInfo);
if ((mNumFrozenItems == NumItems()) && !aLineInfo) {
// All our items are frozen, so we have no flexible lengths to resolve,
// and we aren't being asked to generate computed line info.
FLEX_LOG("No flexible length to resolve");
return;
}
MOZ_ASSERT(!IsEmpty() || aLineInfo,
"empty lines should take the early-return above");
FLEX_LOG("Resolving flexible lengths for items");
// Subtract space occupied by our items' margins/borders/padding/gaps, so
// we can just be dealing with the space available for our flex items' content
// boxes.
const AuCoord64 totalItemMBPAndGaps = mTotalItemMBP + SumOfGaps();
const AuCoord64 spaceAvailableForFlexItemsContentBoxes =
flexContainerMainSize - totalItemMBPAndGaps;
Maybe<AuCoord64> origAvailableFreeSpace;
// NOTE: I claim that this chunk of the algorithm (the looping part) needs to
// run the loop at MOST NumItems() times. This claim should hold up
// because we'll freeze at least one item on each loop iteration, and once
// we've run out of items to freeze, there's nothing left to do. However,
// in most cases, we'll break out of this loop long before we hit that many
// iterations.
for (uint32_t iterationCounter = 0; iterationCounter < NumItems();
iterationCounter++) {
// Set every not-yet-frozen item's used main size to its
// flex base size, and subtract all the used main sizes from our
// total amount of space to determine the 'available free space'
// (positive or negative) to be distributed among our flexible items.
AuCoord64 availableFreeSpace = spaceAvailableForFlexItemsContentBoxes;
for (FlexItem& item : Items()) {
if (!item.IsFrozen()) {
item.SetMainSize(item.FlexBaseSize());
}
availableFreeSpace -= item.MainSize();
}
FLEX_LOG(" available free space: %" PRId64 "; flex items should \"%s\"",
availableFreeSpace.value, isUsingFlexGrow ? "grow" : "shrink");
// The sign of our free space should agree with the type of flexing
// (grow/shrink) that we're doing. Any disagreement should've made us use
// the other type of flexing, or should've been resolved in
// FreezeItemsEarly.
//
// Note: it's possible that an individual flex item has huge
// margin/border/padding that makes either its
// MarginBorderPaddingSizeInMainAxis() or OuterMainSize() negative due to
// integer overflow. If that happens, the accumulated
// mTotalOuterHypotheticalMainSize or mTotalItemMBP could be negative due to
// that one item's negative (overflowed) size. Likewise, a huge main gap
// size between flex items can also make our accumulated SumOfGaps()
// negative. In these case, we throw up our hands and don't require
// isUsingFlexGrow to agree with availableFreeSpace. Luckily, we won't get
// stuck in the algorithm below, and just distribute the wrong
// availableFreeSpace with the wrong grow/shrink factors.
MOZ_ASSERT(!(mTotalOuterHypotheticalMainSize >= 0 && mTotalItemMBP >= 0 &&
totalItemMBPAndGaps >= 0) ||
(isUsingFlexGrow && availableFreeSpace >= 0) ||
(!isUsingFlexGrow && availableFreeSpace <= 0),
"availableFreeSpace's sign should match isUsingFlexGrow");
// If we have any free space available, give each flexible item a portion
// of availableFreeSpace.
if (availableFreeSpace != AuCoord64(0)) {
// The first time we do this, we initialize origAvailableFreeSpace.
if (!origAvailableFreeSpace) {
origAvailableFreeSpace.emplace(availableFreeSpace);
}
// STRATEGY: On each item, we compute & store its "share" of the total
// weight that we've seen so far:
// curWeight / weightSum
//
// Then, when we go to actually distribute the space (in the next loop),
// we can simply walk backwards through the elements and give each item
// its "share" multiplied by the remaining available space.
//
// SPECIAL CASE: If the sum of the weights is larger than the
// maximum representable double (overflowing to infinity), then we can't
// sensibly divide out proportional shares anymore. In that case, we
// simply treat the flex item(s) with the largest weights as if
// their weights were infinite (dwarfing all the others), and we
// distribute all of the available space among them.
double weightSum = 0.0;
double flexFactorSum = 0.0;
double largestWeight = 0.0;
uint32_t numItemsWithLargestWeight = 0;
// Since this loop only operates on unfrozen flex items, we can break as
// soon as we have seen all of them.
uint32_t numUnfrozenItemsToBeSeen = NumItems() - mNumFrozenItems;
for (FlexItem& item : Items()) {
if (numUnfrozenItemsToBeSeen == 0) {
break;
}
if (!item.IsFrozen()) {
numUnfrozenItemsToBeSeen--;
const double curWeight = item.GetWeight(isUsingFlexGrow);
const double curFlexFactor = item.GetFlexFactor(isUsingFlexGrow);
MOZ_ASSERT(curWeight >= 0.0, "weights are non-negative");
MOZ_ASSERT(curFlexFactor >= 0.0, "flex factors are non-negative");
weightSum += curWeight;
flexFactorSum += curFlexFactor;
if (std::isfinite(weightSum)) {
if (curWeight == 0.0) {
item.SetShareOfWeightSoFar(0.0);
} else {
item.SetShareOfWeightSoFar(curWeight / weightSum);
}
} // else, the sum of weights overflows to infinity, in which
// case we don't bother with "SetShareOfWeightSoFar" since
// we know we won't use it. (instead, we'll just give every
// item with the largest weight an equal share of space.)
// Update our largest-weight tracking vars
if (curWeight > largestWeight) {
largestWeight = curWeight;
numItemsWithLargestWeight = 1;
} else if (curWeight == largestWeight) {
numItemsWithLargestWeight++;
}
}
}
MOZ_ASSERT(numUnfrozenItemsToBeSeen == 0, "miscounted frozen items?");
if (weightSum != 0.0) {
MOZ_ASSERT(flexFactorSum != 0.0,
"flex factor sum can't be 0, if a weighted sum "
"of its components (weightSum) is nonzero");
if (flexFactorSum < 1.0) {
// Our unfrozen flex items don't want all of the original free space!
// (Their flex factors add up to something less than 1.)
// Hence, make sure we don't distribute any more than the portion of
// our original free space that these items actually want.
auto totalDesiredPortionOfOrigFreeSpace =
AuCoord64::FromRound(*origAvailableFreeSpace * flexFactorSum);
// Clamp availableFreeSpace to be no larger than that ^^.
// (using min or max, depending on sign).
// This should not change the sign of availableFreeSpace (except
// possibly by setting it to 0), as enforced by this assertion:
NS_ASSERTION(totalDesiredPortionOfOrigFreeSpace == AuCoord64(0) ||
((totalDesiredPortionOfOrigFreeSpace > 0) ==
(availableFreeSpace > 0)),
"When we reduce available free space for flex "
"factors < 1, we shouldn't change the sign of the "
"free space...");
if (availableFreeSpace > 0) {
availableFreeSpace = std::min(availableFreeSpace,
totalDesiredPortionOfOrigFreeSpace);
} else {
availableFreeSpace = std::max(availableFreeSpace,
totalDesiredPortionOfOrigFreeSpace);
}
}
FLEX_LOG(" Distributing available space:");
// Since this loop only operates on unfrozen flex items, we can break as
// soon as we have seen all of them.
numUnfrozenItemsToBeSeen = NumItems() - mNumFrozenItems;
// NOTE: It's important that we traverse our items in *reverse* order
// here, for correct width distribution according to the items'
// "ShareOfWeightSoFar" progressively-calculated values.
for (FlexItem& item : Reversed(Items())) {
if (numUnfrozenItemsToBeSeen == 0) {
break;
}
if (!item.IsFrozen()) {
numUnfrozenItemsToBeSeen--;
// To avoid rounding issues, we compute the change in size for this
// item, and then subtract it from the remaining available space.
AuCoord64 sizeDelta = 0;
if (std::isfinite(weightSum)) {
double myShareOfRemainingSpace = item.ShareOfWeightSoFar();
MOZ_ASSERT(myShareOfRemainingSpace >= 0.0 &&
myShareOfRemainingSpace <= 1.0,
"my share should be nonnegative fractional amount");
if (myShareOfRemainingSpace == 1.0) {
// (We special-case 1.0 to avoid float error from converting
// availableFreeSpace from integer*1.0 --> double --> integer)
sizeDelta = availableFreeSpace;
} else if (myShareOfRemainingSpace > 0.0) {
sizeDelta = AuCoord64::FromRound(availableFreeSpace *
myShareOfRemainingSpace);
}
} else if (item.GetWeight(isUsingFlexGrow) == largestWeight) {
// Total flexibility is infinite, so we're just distributing
// the available space equally among the items that are tied for
// having the largest weight (and this is one of those items).
sizeDelta = AuCoord64::FromRound(
availableFreeSpace / double(numItemsWithLargestWeight));
numItemsWithLargestWeight--;
}
availableFreeSpace -= sizeDelta;
item.SetMainSize(item.MainSize() +
nscoord(sizeDelta.ToMinMaxClamped()));
FLEX_LOG(" flex item %p receives %" PRId64 ", for a total of %d",
item.Frame(), sizeDelta.value, item.MainSize());
}
}
MOZ_ASSERT(numUnfrozenItemsToBeSeen == 0, "miscounted frozen items?");
// If we have an aLineInfo structure to fill out, capture any
// size changes that may have occurred in the previous loop.
// We don't do this inside the previous loop, because we don't
// want to burden layout when aLineInfo is null.
if (aLineInfo) {
uint32_t itemIndex = 0;
for (FlexItem& item : Items()) {
if (!item.IsFrozen()) {
// Calculate a deltaSize that represents how much the flex sizing
// algorithm "wants" to stretch or shrink this item during this
// pass through the algorithm. Later passes through the algorithm
// may overwrite this, until this item is frozen. Note that this
// value may not reflect how much the size of the item is
// actually changed, since the size of the item will be clamped
// to min and max values later in this pass. That's intentional,
// since we want to report the value that the sizing algorithm
// tried to stretch or shrink the item.
nscoord deltaSize =
item.MainSize() - aLineInfo->mItems[itemIndex].mMainBaseSize;
aLineInfo->mItems[itemIndex].mMainDeltaSize = deltaSize;
}
++itemIndex;
}
}
}
}
// Fix min/max violations:
nscoord totalViolation = 0; // keeps track of adjustments for min/max
FLEX_LOG(" Checking for violations:");
// Since this loop only operates on unfrozen flex items, we can break as
// soon as we have seen all of them.
uint32_t numUnfrozenItemsToBeSeen = NumItems() - mNumFrozenItems;
for (FlexItem& item : Items()) {
if (numUnfrozenItemsToBeSeen == 0) {
break;
}
if (!item.IsFrozen()) {
numUnfrozenItemsToBeSeen--;
if (item.MainSize() < item.MainMinSize()) {
// min violation
totalViolation += item.MainMinSize() - item.MainSize();
item.SetMainSize(item.MainMinSize());
item.SetHadMinViolation();
} else if (item.MainSize() > item.MainMaxSize()) {
// max violation
totalViolation += item.MainMaxSize() - item.MainSize();
item.SetMainSize(item.MainMaxSize());
item.SetHadMaxViolation();
}
}
}
MOZ_ASSERT(numUnfrozenItemsToBeSeen == 0, "miscounted frozen items?");
FreezeOrRestoreEachFlexibleSize(totalViolation,
iterationCounter + 1 == NumItems());
FLEX_LOG(" Total violation: %d", totalViolation);
if (mNumFrozenItems == NumItems()) {
break;
}
MOZ_ASSERT(totalViolation != 0,
"Zero violation should've made us freeze all items & break");
}
#ifdef DEBUG
// Post-condition: all items should've been frozen.
// Make sure the counts match:
MOZ_ASSERT(mNumFrozenItems == NumItems(), "All items should be frozen");
// For good measure, check each item directly, in case our counts are busted:
for (const FlexItem& item : Items()) {
MOZ_ASSERT(item.IsFrozen(), "All items should be frozen");
}
#endif // DEBUG
}
MainAxisPositionTracker::MainAxisPositionTracker(
const FlexboxAxisTracker& aAxisTracker, const FlexLine* aLine,
const StyleContentDistribution& aJustifyContent,
nscoord aContentBoxMainSize)
: PositionTracker(aAxisTracker.GetWritingMode(), aAxisTracker.MainAxis(),
aAxisTracker.IsMainAxisReversed()),
// we chip away at this below
mPackingSpaceRemaining(aContentBoxMainSize),
mJustifyContent(aJustifyContent) {
// Extract the flag portion of mJustifyContent and strip off the flag bits
// NOTE: This must happen before any assignment to mJustifyContent to
// avoid overwriting the flag bits.
StyleAlignFlags justifyContentFlags =
mJustifyContent.primary & StyleAlignFlags::FLAG_BITS;
mJustifyContent.primary &= ~StyleAlignFlags::FLAG_BITS;
// 'normal' behaves as 'stretch', and 'stretch' behaves as 'flex-start',
// in the main axis
// https://drafts.csswg.org/css-align-3/#propdef-justify-content
if (mJustifyContent.primary == StyleAlignFlags::NORMAL ||
mJustifyContent.primary == StyleAlignFlags::STRETCH) {
mJustifyContent.primary = StyleAlignFlags::FLEX_START;
}
// mPackingSpaceRemaining is initialized to the container's main size. Now
// we'll subtract out the main sizes of our flex items, so that it ends up
// with the *actual* amount of packing space.
for (const FlexItem& item : aLine->Items()) {
mPackingSpaceRemaining -= item.OuterMainSize();
mNumAutoMarginsInMainAxis += item.NumAutoMarginsInMainAxis();
}
// Subtract space required for row/col gap from the remaining packing space
mPackingSpaceRemaining -= aLine->SumOfGaps();
if (mPackingSpaceRemaining <= 0) {
// No available packing space to use for resolving auto margins.
mNumAutoMarginsInMainAxis = 0;
// If packing space is negative and <overflow-position> is set to 'safe'
// all justify options fall back to 'start'
if (justifyContentFlags & StyleAlignFlags::SAFE) {
mJustifyContent.primary = StyleAlignFlags::START;
}
}
// If packing space is negative or we only have one item, 'space-between'
// falls back to 'flex-start', and 'space-around' & 'space-evenly' fall back
// to 'center'. In those cases, it's simplest to just pretend we have a
// different 'justify-content' value and share code.
if (mPackingSpaceRemaining < 0 || aLine->NumItems() == 1) {
if (mJustifyContent.primary == StyleAlignFlags::SPACE_BETWEEN) {
mJustifyContent.primary = StyleAlignFlags::FLEX_START;
} else if (mJustifyContent.primary == StyleAlignFlags::SPACE_AROUND ||
mJustifyContent.primary == StyleAlignFlags::SPACE_EVENLY) {
mJustifyContent.primary = StyleAlignFlags::CENTER;
}
}
// Map 'left'/'right' to 'start'/'end'
if (mJustifyContent.primary == StyleAlignFlags::LEFT ||
mJustifyContent.primary == StyleAlignFlags::RIGHT) {
mJustifyContent.primary =
aAxisTracker.ResolveJustifyLeftRight(mJustifyContent.primary);
}
// Map 'start'/'end' to 'flex-start'/'flex-end'.
if (mJustifyContent.primary == StyleAlignFlags::START) {
mJustifyContent.primary = aAxisTracker.IsMainAxisReversed()
? StyleAlignFlags::FLEX_END
: StyleAlignFlags::FLEX_START;
} else if (mJustifyContent.primary == StyleAlignFlags::END) {
mJustifyContent.primary = aAxisTracker.IsMainAxisReversed()
? StyleAlignFlags::FLEX_START
: StyleAlignFlags::FLEX_END;
}
// Figure out how much space we'll set aside for auto margins or
// packing spaces, and advance past any leading packing-space.
if (mNumAutoMarginsInMainAxis == 0 && mPackingSpaceRemaining != 0 &&
!aLine->IsEmpty()) {
if (mJustifyContent.primary == StyleAlignFlags::FLEX_START) {
// All packing space should go at the end --> nothing to do here.
} else if (mJustifyContent.primary == StyleAlignFlags::FLEX_END) {
// All packing space goes at the beginning
mPosition += mPackingSpaceRemaining;
} else if (mJustifyContent.primary == StyleAlignFlags::CENTER) {
// Half the packing space goes at the beginning
mPosition += mPackingSpaceRemaining / 2;
} else if (mJustifyContent.primary == StyleAlignFlags::SPACE_BETWEEN ||
mJustifyContent.primary == StyleAlignFlags::SPACE_AROUND ||
mJustifyContent.primary == StyleAlignFlags::SPACE_EVENLY) {
nsFlexContainerFrame::CalculatePackingSpace(
aLine->NumItems(), mJustifyContent, &mPosition,
&mNumPackingSpacesRemaining, &mPackingSpaceRemaining);
} else {
MOZ_ASSERT_UNREACHABLE("Unexpected justify-content value");
}
}
MOZ_ASSERT(mNumPackingSpacesRemaining == 0 || mNumAutoMarginsInMainAxis == 0,
"extra space should either go to packing space or to "
"auto margins, but not to both");
}
void MainAxisPositionTracker::ResolveAutoMarginsInMainAxis(FlexItem& aItem) {
if (mNumAutoMarginsInMainAxis) {
const auto& styleMargin = aItem.Frame()->StyleMargin()->mMargin;
for (const auto side : {StartSide(), EndSide()}) {
if (styleMargin.Get(mWM, side).IsAuto()) {
// NOTE: This integer math will skew the distribution of remainder
// app-units towards the end, which is fine.
nscoord curAutoMarginSize =
mPackingSpaceRemaining / mNumAutoMarginsInMainAxis;
MOZ_ASSERT(aItem.GetMarginComponentForSide(side) == 0,
"Expecting auto margins to have value '0' before we "
"resolve them");
aItem.SetMarginComponentForSide(side, curAutoMarginSize);
mNumAutoMarginsInMainAxis--;
mPackingSpaceRemaining -= curAutoMarginSize;
}
}
}
}
void MainAxisPositionTracker::TraversePackingSpace() {
if (mNumPackingSpacesRemaining) {
MOZ_ASSERT(mJustifyContent.primary == StyleAlignFlags::SPACE_BETWEEN ||
mJustifyContent.primary == StyleAlignFlags::SPACE_AROUND ||
mJustifyContent.primary == StyleAlignFlags::SPACE_EVENLY,
"mNumPackingSpacesRemaining only applies for "
"space-between/space-around/space-evenly");
MOZ_ASSERT(mPackingSpaceRemaining >= 0,
"ran out of packing space earlier than we expected");
// NOTE: This integer math will skew the distribution of remainder
// app-units towards the end, which is fine.
nscoord curPackingSpace =
mPackingSpaceRemaining / mNumPackingSpacesRemaining;
mPosition += curPackingSpace;
mNumPackingSpacesRemaining--;
mPackingSpaceRemaining -= curPackingSpace;
}
}
CrossAxisPositionTracker::CrossAxisPositionTracker(
nsTArray<FlexLine>& aLines, const ReflowInput& aReflowInput,
nscoord aContentBoxCrossSize, bool aIsCrossSizeDefinite,
const FlexboxAxisTracker& aAxisTracker, const nscoord aCrossGapSize)
: PositionTracker(aAxisTracker.GetWritingMode(), aAxisTracker.CrossAxis(),
aAxisTracker.IsCrossAxisReversed()),
mAlignContent(aReflowInput.mStylePosition->mAlignContent),
mCrossGapSize(aCrossGapSize) {
// Extract and strip the flag bits from alignContent
StyleAlignFlags alignContentFlags =
mAlignContent.primary & StyleAlignFlags::FLAG_BITS;
mAlignContent.primary &= ~StyleAlignFlags::FLAG_BITS;
// 'normal' behaves as 'stretch'
if (mAlignContent.primary == StyleAlignFlags::NORMAL) {
mAlignContent.primary = StyleAlignFlags::STRETCH;
}
const bool isSingleLine =
StyleFlexWrap::Nowrap == aReflowInput.mStylePosition->mFlexWrap;
if (isSingleLine) {
MOZ_ASSERT(aLines.Length() == 1,
"If we're styled as single-line, we should only have 1 line");
// "If the flex container is single-line and has a definite cross size, the
// cross size of the flex line is the flex container's inner cross size."
//
// SOURCE: https://drafts.csswg.org/css-flexbox/#algo-cross-line
// NOTE: This means (by definition) that there's no packing space, which
// means we don't need to be concerned with "align-content" at all and we
// can return early. This is handy, because this is the usual case (for
// single-line flexbox).
if (aIsCrossSizeDefinite) {
aLines[0].SetLineCrossSize(aContentBoxCrossSize);
return;
}
// "If the flex container is single-line, then clamp the line's
// cross-size to be within the container's computed min and max cross-size
// properties."
aLines[0].SetLineCrossSize(NS_CSS_MINMAX(aLines[0].LineCrossSize(),
aReflowInput.ComputedMinBSize(),
aReflowInput.ComputedMaxBSize()));
}
// NOTE: The rest of this function should essentially match
// MainAxisPositionTracker's constructor, though with FlexLines instead of
// FlexItems, and with the additional value "stretch" (and of course with
// cross sizes instead of main sizes.)
// Figure out how much packing space we have (container's cross size minus
// all the lines' cross sizes). Also, share this loop to count how many
// lines we have. (We need that count in some cases below.)
mPackingSpaceRemaining = aContentBoxCrossSize;
uint32_t numLines = 0;
for (FlexLine& line : aLines) {
mPackingSpaceRemaining -= line.LineCrossSize();
numLines++;
}
// Subtract space required for row/col gap from the remaining packing space
MOZ_ASSERT(numLines >= 1,
"GenerateFlexLines should've produced at least 1 line");
mPackingSpaceRemaining -= aCrossGapSize * (numLines - 1);
// If <overflow-position> is 'safe' and packing space is negative
// all align options fall back to 'start'
if ((alignContentFlags & StyleAlignFlags::SAFE) &&
mPackingSpaceRemaining < 0) {
mAlignContent.primary = StyleAlignFlags::START;
}
// If packing space is negative, 'space-between' and 'stretch' behave like
// 'flex-start', and 'space-around' and 'space-evenly' behave like 'center'.
// In those cases, it's simplest to just pretend we have a different
// 'align-content' value and share code. (If we only have one line, all of
// the 'space-*' keywords fall back as well, but 'stretch' doesn't because
// even a single line can still stretch.)
if (mPackingSpaceRemaining < 0 &&
mAlignContent.primary == StyleAlignFlags::STRETCH) {
mAlignContent.primary = StyleAlignFlags::FLEX_START;
} else if (mPackingSpaceRemaining < 0 || numLines == 1) {
if (mAlignContent.primary == StyleAlignFlags::SPACE_BETWEEN) {
mAlignContent.primary = StyleAlignFlags::FLEX_START;
} else if (mAlignContent.primary == StyleAlignFlags::SPACE_AROUND ||
mAlignContent.primary == StyleAlignFlags::SPACE_EVENLY) {
mAlignContent.primary = StyleAlignFlags::CENTER;
}
}
// Map 'start'/'end' to 'flex-start'/'flex-end'.
if (mAlignContent.primary == StyleAlignFlags::START) {
mAlignContent.primary = aAxisTracker.IsCrossAxisReversed()
? StyleAlignFlags::FLEX_END
: StyleAlignFlags::FLEX_START;
} else if (mAlignContent.primary == StyleAlignFlags::END) {
mAlignContent.primary = aAxisTracker.IsCrossAxisReversed()
? StyleAlignFlags::FLEX_START
: StyleAlignFlags::FLEX_END;
}
// Figure out how much space we'll set aside for packing spaces, and advance
// past any leading packing-space.
if (mPackingSpaceRemaining != 0) {
if (mAlignContent.primary == StyleAlignFlags::BASELINE ||
mAlignContent.primary == StyleAlignFlags::LAST_BASELINE) {
// TODO: Bug 1480850 will implement 'align-content: [first/last] baseline'
// for flexbox. Until then, behaves as if align-content is 'flex-start' by
// doing nothing.
} else if (mAlignContent.primary == StyleAlignFlags::FLEX_START) {
// All packing space should go at the end --> nothing to do here.
} else if (mAlignContent.primary == StyleAlignFlags::FLEX_END) {
// All packing space goes at the beginning
mPosition += mPackingSpaceRemaining;
} else if (mAlignContent.primary == StyleAlignFlags::CENTER) {
// Half the packing space goes at the beginning
mPosition += mPackingSpaceRemaining / 2;
} else if (mAlignContent.primary == StyleAlignFlags::SPACE_BETWEEN ||
mAlignContent.primary == StyleAlignFlags::SPACE_AROUND ||
mAlignContent.primary == StyleAlignFlags::SPACE_EVENLY) {
nsFlexContainerFrame::CalculatePackingSpace(
numLines, mAlignContent, &mPosition, &mNumPackingSpacesRemaining,
&mPackingSpaceRemaining);
} else if (mAlignContent.primary == StyleAlignFlags::STRETCH) {
// Split space equally between the lines:
MOZ_ASSERT(mPackingSpaceRemaining > 0,
"negative packing space should make us use 'flex-start' "
"instead of 'stretch' (and we shouldn't bother with this "
"code if we have 0 packing space)");
uint32_t numLinesLeft = numLines;
for (FlexLine& line : aLines) {
// Our share is the amount of space remaining, divided by the number
// of lines remainig.
MOZ_ASSERT(numLinesLeft > 0, "miscalculated num lines");
nscoord shareOfExtraSpace = mPackingSpaceRemaining / numLinesLeft;
nscoord newSize = line.LineCrossSize() + shareOfExtraSpace;
line.SetLineCrossSize(newSize);
mPackingSpaceRemaining -= shareOfExtraSpace;
numLinesLeft--;
}
MOZ_ASSERT(numLinesLeft == 0, "miscalculated num lines");
} else {
MOZ_ASSERT_UNREACHABLE("Unexpected align-content value");
}
}
}
void CrossAxisPositionTracker::TraversePackingSpace() {
if (mNumPackingSpacesRemaining) {
MOZ_ASSERT(mAlignContent.primary == StyleAlignFlags::SPACE_BETWEEN ||
mAlignContent.primary == StyleAlignFlags::SPACE_AROUND ||
mAlignContent.primary == StyleAlignFlags::SPACE_EVENLY,
"mNumPackingSpacesRemaining only applies for "
"space-between/space-around/space-evenly");
MOZ_ASSERT(mPackingSpaceRemaining >= 0,
"ran out of packing space earlier than we expected");
// NOTE: This integer math will skew the distribution of remainder
// app-units towards the end, which is fine.
nscoord curPackingSpace =
mPackingSpaceRemaining / mNumPackingSpacesRemaining;
mPosition += curPackingSpace;
mNumPackingSpacesRemaining--;
mPackingSpaceRemaining -= curPackingSpace;
}
}
SingleLineCrossAxisPositionTracker::SingleLineCrossAxisPositionTracker(
const FlexboxAxisTracker& aAxisTracker)
: PositionTracker(aAxisTracker.GetWritingMode(), aAxisTracker.CrossAxis(),
aAxisTracker.IsCrossAxisReversed()) {}
void FlexLine::ComputeCrossSizeAndBaseline(
const FlexboxAxisTracker& aAxisTracker) {
nscoord crossStartToFurthestFirstBaseline = nscoord_MIN;
nscoord crossEndToFurthestFirstBaseline = nscoord_MIN;
nscoord crossStartToFurthestLastBaseline = nscoord_MIN;
nscoord crossEndToFurthestLastBaseline = nscoord_MIN;
nscoord largestOuterCrossSize = 0;
for (const FlexItem& item : Items()) {
nscoord curOuterCrossSize = item.OuterCrossSize();
if ((item.AlignSelf()._0 == StyleAlignFlags::BASELINE ||
item.AlignSelf()._0 == StyleAlignFlags::LAST_BASELINE) &&
item.NumAutoMarginsInCrossAxis() == 0) {
const bool useFirst = (item.AlignSelf()._0 == StyleAlignFlags::BASELINE);
// FIXME: Once we support "writing-mode", we'll have to do baseline
// alignment in vertical flex containers here (w/ horizontal cross-axes).
// Find distance from our item's cross-start and cross-end margin-box
// edges to its baseline.
//
// Here's a diagram of a flex-item that we might be doing this on.
// "mmm" is the margin-box, "bbb" is the border-box. The bottom of
// the text "BASE" is the baseline.
//
// ---(cross-start)---
// ___ ___ ___
// mmmmmmmmmmmm | |margin-start |
// m m | _|_ ___ |
// m bbbbbbbb m |curOuterCrossSize | |crossStartToBaseline
// m b b m | |ascent |
// m b BASE b m | _|_ _|_
// m b b m | |
// m bbbbbbbb m | |crossEndToBaseline
// m m | |
// mmmmmmmmmmmm _|_ _|_
//
// ---(cross-end)---
//
// We already have the curOuterCrossSize, margin-start, and the ascent.
// * We can get crossStartToBaseline by adding margin-start + ascent.
// * If we subtract that from the curOuterCrossSize, we get
// crossEndToBaseline.
nscoord crossStartToBaseline = item.BaselineOffsetFromOuterCrossEdge(
aAxisTracker.CrossAxisPhysicalStartSide(), useFirst);
nscoord crossEndToBaseline = curOuterCrossSize - crossStartToBaseline;
// Now, update our "largest" values for these (across all the flex items
// in this flex line), so we can use them in computing the line's cross
// size below:
if (useFirst) {
crossStartToFurthestFirstBaseline =
std::max(crossStartToFurthestFirstBaseline, crossStartToBaseline);
crossEndToFurthestFirstBaseline =
std::max(crossEndToFurthestFirstBaseline, crossEndToBaseline);
} else {
crossStartToFurthestLastBaseline =
std::max(crossStartToFurthestLastBaseline, crossStartToBaseline);
crossEndToFurthestLastBaseline =
std::max(crossEndToFurthestLastBaseline, crossEndToBaseline);
}
} else {
largestOuterCrossSize =
std::max(largestOuterCrossSize, curOuterCrossSize);
}
}
// The line's baseline offset is the distance from the line's edge to the
// furthest item-baseline. The item(s) with that baseline will be exactly
// aligned with the line's edge.
mFirstBaselineOffset = crossStartToFurthestFirstBaseline;
mLastBaselineOffset = crossEndToFurthestLastBaseline;
// The line's cross-size is the larger of:
// (a) [largest cross-start-to-baseline + largest baseline-to-cross-end] of
// all baseline-aligned items with no cross-axis auto margins...
// and
// (b) [largest cross-start-to-baseline + largest baseline-to-cross-end] of
// all last baseline-aligned items with no cross-axis auto margins...
// and
// (c) largest cross-size of all other children.
mLineCrossSize = std::max(
std::max(
crossStartToFurthestFirstBaseline + crossEndToFurthestFirstBaseline,
crossStartToFurthestLastBaseline + crossEndToFurthestLastBaseline),
largestOuterCrossSize);
}
void FlexItem::ResolveStretchedCrossSize(nscoord aLineCrossSize) {
// We stretch IFF we are align-self:stretch, have no auto margins in
// cross axis, and have cross-axis size property == "auto". If any of those
// conditions don't hold up, we won't stretch.
if (mAlignSelf._0 != StyleAlignFlags::STRETCH ||
NumAutoMarginsInCrossAxis() != 0 || !IsCrossSizeAuto()) {
return;
}
// If we've already been stretched, we can bail out early, too.
// No need to redo the calculation.
if (mIsStretched) {
return;
}
// Reserve space for margins & border & padding, and then use whatever
// remains as our item's cross-size (clamped to its min/max range).
nscoord stretchedSize = aLineCrossSize - MarginBorderPaddingSizeInCrossAxis();
stretchedSize = NS_CSS_MINMAX(stretchedSize, mCrossMinSize, mCrossMaxSize);
// Update the cross-size & make a note that it's stretched, so we know to
// override the reflow input's computed cross-size in our final reflow.
SetCrossSize(stretchedSize);
mIsStretched = true;
}
static nsBlockFrame* FindFlexItemBlockFrame(nsIFrame* aFrame) {
if (nsBlockFrame* block = do_QueryFrame(aFrame)) {
return block;
}
for (nsIFrame* f : aFrame->PrincipalChildList()) {
if (nsBlockFrame* block = FindFlexItemBlockFrame(f)) {
return block;
}
}
return nullptr;
}
nsBlockFrame* FlexItem::BlockFrame() const {
return FindFlexItemBlockFrame(Frame());
}
void SingleLineCrossAxisPositionTracker::ResolveAutoMarginsInCrossAxis(
const FlexLine& aLine, FlexItem& aItem) {
// Subtract the space that our item is already occupying, to see how much
// space (if any) is available for its auto margins.
nscoord spaceForAutoMargins = aLine.LineCrossSize() - aItem.OuterCrossSize();
if (spaceForAutoMargins <= 0) {
return; // No available space --> nothing to do
}
uint32_t numAutoMargins = aItem.NumAutoMarginsInCrossAxis();
if (numAutoMargins == 0) {
return; // No auto margins --> nothing to do.
}
// OK, we have at least one auto margin and we have some available space.
// Give each auto margin a share of the space.
const auto& styleMargin = aItem.Frame()->StyleMargin()->mMargin;
for (const auto side : {StartSide(), EndSide()}) {
if (styleMargin.Get(mWM, side).IsAuto()) {
MOZ_ASSERT(aItem.GetMarginComponentForSide(side) == 0,
"Expecting auto margins to have value '0' before we "
"update them");
// NOTE: integer divison is fine here; numAutoMargins is either 1 or 2.
// If it's 2 & spaceForAutoMargins is odd, 1st margin gets smaller half.
nscoord curAutoMarginSize = spaceForAutoMargins / numAutoMargins;
aItem.SetMarginComponentForSide(side, curAutoMarginSize);
numAutoMargins--;
spaceForAutoMargins -= curAutoMarginSize;
}
}
}
void SingleLineCrossAxisPositionTracker::EnterAlignPackingSpace(
const FlexLine& aLine, const FlexItem& aItem,
const FlexboxAxisTracker& aAxisTracker) {
// We don't do align-self alignment on items that have auto margins
// in the cross axis.
if (aItem.NumAutoMarginsInCrossAxis()) {
return;
}
StyleAlignFlags alignSelf = aItem.AlignSelf()._0;
// NOTE: 'stretch' behaves like 'flex-start' once we've stretched any
// auto-sized items (which we've already done).
if (alignSelf == StyleAlignFlags::STRETCH) {
alignSelf = StyleAlignFlags::FLEX_START;
}
// Map 'self-start'/'self-end' to 'start'/'end'
if (alignSelf == StyleAlignFlags::SELF_START ||
alignSelf == StyleAlignFlags::SELF_END) {
const LogicalAxis logCrossAxis =
aAxisTracker.IsRowOriented() ? eLogicalAxisBlock : eLogicalAxisInline;
const WritingMode cWM = aAxisTracker.GetWritingMode();
const bool sameStart =
cWM.ParallelAxisStartsOnSameSide(logCrossAxis, aItem.GetWritingMode());
alignSelf = sameStart == (alignSelf == StyleAlignFlags::SELF_START)
? StyleAlignFlags::START
: StyleAlignFlags::END;
}
// Map 'start'/'end' to 'flex-start'/'flex-end'.
if (alignSelf == StyleAlignFlags::START) {
alignSelf = aAxisTracker.IsCrossAxisReversed()
? StyleAlignFlags::FLEX_END
: StyleAlignFlags::FLEX_START;
} else if (alignSelf == StyleAlignFlags::END) {
alignSelf = aAxisTracker.IsCrossAxisReversed() ? StyleAlignFlags::FLEX_START
: StyleAlignFlags::FLEX_END;
}
// 'align-self' falls back to 'flex-start' if it is 'center'/'flex-end' and we
// have cross axis overflow
// XXX we should really be falling back to 'start' as of bug 1472843
if (aLine.LineCrossSize() < aItem.OuterCrossSize() &&
(aItem.AlignSelfFlags() & StyleAlignFlags::SAFE)) {
alignSelf = StyleAlignFlags::FLEX_START;
}
if (alignSelf == StyleAlignFlags::FLEX_START) {
// No space to skip over -- we're done.
} else if (alignSelf == StyleAlignFlags::FLEX_END) {
mPosition += aLine.LineCrossSize() - aItem.OuterCrossSize();
} else if (alignSelf == StyleAlignFlags::CENTER) {
// Note: If cross-size is odd, the "after" space will get the extra unit.
mPosition += (aLine.LineCrossSize() - aItem.OuterCrossSize()) / 2;
} else if (alignSelf == StyleAlignFlags::BASELINE ||
alignSelf == StyleAlignFlags::LAST_BASELINE) {
const bool useFirst = (alignSelf == StyleAlignFlags::BASELINE);
// Baseline-aligned items are collectively aligned with the line's physical
// cross-start or cross-end side, depending on whether we're doing
// first-baseline or last-baseline alignment.
const mozilla::Side baselineAlignStartSide =
useFirst ? aAxisTracker.CrossAxisPhysicalStartSide()
: aAxisTracker.CrossAxisPhysicalEndSide();
nscoord itemBaselineOffset = aItem.BaselineOffsetFromOuterCrossEdge(
baselineAlignStartSide, useFirst);
nscoord lineBaselineOffset =
useFirst ? aLine.FirstBaselineOffset() : aLine.LastBaselineOffset();
NS_ASSERTION(lineBaselineOffset >= itemBaselineOffset,
"failed at finding largest baseline offset");
// How much do we need to adjust our position (from the line edge),
// to get the item's baseline to hit the line's baseline offset:
nscoord baselineDiff = lineBaselineOffset - itemBaselineOffset;
if (useFirst) {
// mPosition is already at line's flex-start edge.
// From there, we step *forward* by the baseline adjustment:
mPosition += baselineDiff;
} else {
// Advance to align item w/ line's flex-end edge (as in FLEX_END case):
mPosition += aLine.LineCrossSize() - aItem.OuterCrossSize();
// ...and step *back* by the baseline adjustment:
mPosition -= baselineDiff;
}
} else {
MOZ_ASSERT_UNREACHABLE("Unexpected align-self value");
}
}
FlexboxAxisInfo::FlexboxAxisInfo(const nsIFrame* aFlexContainer) {
MOZ_ASSERT(aFlexContainer && aFlexContainer->IsFlexContainerFrame(),
"Only flex containers may be passed to this constructor!");
if (IsLegacyBox(aFlexContainer)) {
InitAxesFromLegacyProps(aFlexContainer);
} else {
InitAxesFromModernProps(aFlexContainer);
}
}
void FlexboxAxisInfo::InitAxesFromLegacyProps(const nsIFrame* aFlexContainer) {
const nsStyleXUL* styleXUL = aFlexContainer->StyleXUL();
const bool boxOrientIsVertical =
styleXUL->mBoxOrient == StyleBoxOrient::Vertical;
const bool wmIsVertical = aFlexContainer->GetWritingMode().IsVertical();
// If box-orient agrees with our writing-mode, then we're "row-oriented"
// (i.e. the flexbox main axis is the same as our writing mode's inline
// direction). Otherwise, we're column-oriented (i.e. the flexbox's main
// axis is perpendicular to the writing-mode's inline direction).
mIsRowOriented = (boxOrientIsVertical == wmIsVertical);
// Legacy flexbox can use "-webkit-box-direction: reverse" to reverse the
// main axis (so it runs in the reverse direction of the inline axis):
mIsMainAxisReversed = styleXUL->mBoxDirection == StyleBoxDirection::Reverse;
// Legacy flexbox does not support reversing the cross axis -- it has no
// equivalent of modern flexbox's "flex-wrap: wrap-reverse".
mIsCrossAxisReversed = false;
}
void FlexboxAxisInfo::InitAxesFromModernProps(const nsIFrame* aFlexContainer) {
const nsStylePosition* stylePos = aFlexContainer->StylePosition();
StyleFlexDirection flexDirection = stylePos->mFlexDirection;
// Determine main axis:
switch (flexDirection) {
case StyleFlexDirection::Row:
mIsRowOriented = true;
mIsMainAxisReversed = false;
break;
case StyleFlexDirection::RowReverse:
mIsRowOriented = true;
mIsMainAxisReversed = true;
break;
case StyleFlexDirection::Column:
mIsRowOriented = false;
mIsMainAxisReversed = false;
break;
case StyleFlexDirection::ColumnReverse:
mIsRowOriented = false;
mIsMainAxisReversed = true;
break;
}
// "flex-wrap: wrap-reverse" reverses our cross axis.
mIsCrossAxisReversed = stylePos->mFlexWrap == StyleFlexWrap::WrapReverse;
}
FlexboxAxisTracker::FlexboxAxisTracker(
const nsFlexContainerFrame* aFlexContainer)
: mWM(aFlexContainer->GetWritingMode()), mAxisInfo(aFlexContainer) {}
LogicalSide FlexboxAxisTracker::MainAxisStartSide() const {
return MakeLogicalSide(
MainAxis(), IsMainAxisReversed() ? eLogicalEdgeEnd : eLogicalEdgeStart);
}
LogicalSide FlexboxAxisTracker::CrossAxisStartSide() const {
return MakeLogicalSide(
CrossAxis(), IsCrossAxisReversed() ? eLogicalEdgeEnd : eLogicalEdgeStart);
}
void nsFlexContainerFrame::GenerateFlexLines(
const ReflowInput& aReflowInput, const nscoord aTentativeContentBoxMainSize,
const nscoord aTentativeContentBoxCrossSize,
const nsTArray<StrutInfo>& aStruts, const FlexboxAxisTracker& aAxisTracker,
nscoord aMainGapSize, nsTArray<nsIFrame*>& aPlaceholders,
nsTArray<FlexLine>& aLines, bool& aHasCollapsedItems) {
MOZ_ASSERT(aLines.IsEmpty(), "Expecting outparam to start out empty");
auto ConstructNewFlexLine = [&aLines, aMainGapSize]() {
return aLines.EmplaceBack(aMainGapSize);
};
const bool isSingleLine =
StyleFlexWrap::Nowrap == aReflowInput.mStylePosition->mFlexWrap;
// We have at least one FlexLine. Even an empty flex container has a single
// (empty) flex line.
FlexLine* curLine = ConstructNewFlexLine();
nscoord wrapThreshold;
if (isSingleLine) {
// Not wrapping. Set threshold to sentinel value that tells us not to wrap.
wrapThreshold = NS_UNCONSTRAINEDSIZE;
} else {
// Wrapping! Set wrap threshold to flex container's content-box main-size.
wrapThreshold = aTentativeContentBoxMainSize;
// If the flex container doesn't have a definite content-box main-size
// (e.g. if main axis is vertical & 'height' is 'auto'), make sure we at
// least wrap when we hit its max main-size.
if (wrapThreshold == NS_UNCONSTRAINEDSIZE) {
const nscoord flexContainerMaxMainSize =
aAxisTracker.MainComponent(aReflowInput.ComputedMaxSize());
wrapThreshold = flexContainerMaxMainSize;
}
}
// Tracks the index of the next strut, in aStruts (and when this hits
// aStruts.Length(), that means there are no more struts):
uint32_t nextStrutIdx = 0;
// Overall index of the current flex item in the flex container. (This gets
// checked against entries in aStruts.)
uint32_t itemIdxInContainer = 0;
CSSOrderAwareFrameIterator iter(
this, FrameChildListID::Principal,
CSSOrderAwareFrameIterator::ChildFilter::IncludeAll,
CSSOrderAwareFrameIterator::OrderState::Unknown,
OrderingPropertyForIter(this));
AddOrRemoveStateBits(NS_STATE_FLEX_NORMAL_FLOW_CHILDREN_IN_CSS_ORDER,
iter.ItemsAreAlreadyInOrder());
const bool useMozBoxCollapseBehavior =
StyleVisibility()->UseLegacyCollapseBehavior();
for (; !iter.AtEnd(); iter.Next()) {
nsIFrame* childFrame = *iter;
// Don't create flex items / lines for placeholder frames:
if (childFrame->IsPlaceholderFrame()) {
aPlaceholders.AppendElement(childFrame);
continue;
}
const bool collapsed = childFrame->StyleVisibility()->IsCollapse();
aHasCollapsedItems = aHasCollapsedItems || collapsed;
if (useMozBoxCollapseBehavior && collapsed) {
// Legacy visibility:collapse behavior: make a 0-sized strut. (No need to
// bother with aStruts and remembering cross size.)
curLine->Items().EmplaceBack(childFrame, 0, aReflowInput.GetWritingMode(),
aAxisTracker);
} else if (nextStrutIdx < aStruts.Length() &&
aStruts[nextStrutIdx].mItemIdx == itemIdxInContainer) {
// Use the simplified "strut" FlexItem constructor:
curLine->Items().EmplaceBack(childFrame,
aStruts[nextStrutIdx].mStrutCrossSize,
aReflowInput.GetWritingMode(), aAxisTracker);
nextStrutIdx++;
} else {
GenerateFlexItemForChild(*curLine, childFrame, aReflowInput, aAxisTracker,
aTentativeContentBoxCrossSize);
}
// Check if we need to wrap the newly appended item to a new line, i.e. if
// its outer hypothetical main size pushes our line over the threshold.
// But we don't wrap if the line-length is unconstrained, nor do we wrap if
// this was the first item on the line.
if (wrapThreshold != NS_UNCONSTRAINEDSIZE &&
curLine->Items().Length() > 1) {
// If the line will be longer than wrapThreshold or at least as long as
// nscoord_MAX because of the newly appended item, then wrap and move the
// item to a new line.
auto newOuterSize = curLine->TotalOuterHypotheticalMainSize();
newOuterSize += curLine->Items().LastElement().OuterMainSize();
// Account for gap between this line's previous item and this item.
newOuterSize += aMainGapSize;
if (newOuterSize >= nscoord_MAX || newOuterSize > wrapThreshold) {
curLine = ConstructNewFlexLine();
// Get the previous line after adding a new line because the address can
// change if nsTArray needs to reallocate a new space for the new line.
FlexLine& prevLine = aLines[aLines.Length() - 2];
// Move the item from the end of prevLine to the end of curLine.
curLine->Items().AppendElement(prevLine.Items().PopLastElement());
}
}
// Update the line's bookkeeping about how large its items collectively are.
curLine->AddLastItemToMainSizeTotals();
itemIdxInContainer++;
}
}
nsFlexContainerFrame::FlexLayoutResult
nsFlexContainerFrame::GenerateFlexLayoutResult() {
MOZ_ASSERT(GetPrevInFlow(), "This should be called by non-first-in-flows!");
auto* data = FirstInFlow()->GetProperty(SharedFlexData::Prop());
MOZ_ASSERT(data, "SharedFlexData should be set by our first-in-flow!");
FlexLayoutResult flr;
// The order state of the children is consistent across entire continuation
// chain due to calling nsContainerFrame::NormalizeChildLists() at the
// beginning of Reflow(), so we can align our state bit with our
// prev-in-flow's state. Setup here before calling OrderStateForIter() below.
AddOrRemoveStateBits(NS_STATE_FLEX_NORMAL_FLOW_CHILDREN_IN_CSS_ORDER,
GetPrevInFlow()->HasAnyStateBits(
NS_STATE_FLEX_NORMAL_FLOW_CHILDREN_IN_CSS_ORDER));
// Construct flex items for this flex container fragment from existing flex
// items in SharedFlexData.
CSSOrderAwareFrameIterator iter(
this, FrameChildListID::Principal,
CSSOrderAwareFrameIterator::ChildFilter::SkipPlaceholders,
OrderStateForIter(this), OrderingPropertyForIter(this));
auto ConstructNewFlexLine = [&flr]() {
// Use zero main gap size since it doesn't matter in flex container's
// next-in-flows. We've computed flex items' positions in first-in-flow.
return flr.mLines.EmplaceBack(0);
};
// We have at least one FlexLine. Even an empty flex container has a single
// (empty) flex line.
FlexLine* currentLine = ConstructNewFlexLine();
if (!iter.AtEnd()) {
nsIFrame* child = *iter;
nsIFrame* childFirstInFlow = child->FirstInFlow();
// We are iterating nested for-loops over the FlexLines and FlexItems
// generated by GenerateFlexLines() and cached in flex container's
// first-in-flow. For each flex item, check if its frame (must be a
// first-in-flow) is the first-in-flow of the first child frame in this flex
// container continuation. If so, clone the data from that FlexItem into a
// FlexLine. When we find a match for the item, we know that the next child
// frame might have its first-in-flow as the next item in the same original
// line. In this case, we'll put the cloned data in the same line here as
// well.
for (const FlexLine& line : data->mLines) {
// If currentLine is empty, either it is the first line, or all the items
// in the previous line have been placed in our prev-in-flows. No need to
// construct a new line.
if (!currentLine->IsEmpty()) {
currentLine = ConstructNewFlexLine();
}
for (const FlexItem& item : line.Items()) {
if (item.Frame() == childFirstInFlow) {
currentLine->Items().AppendElement(item.CloneFor(child));
iter.Next();
if (iter.AtEnd()) {
// We've constructed flex items for all children. No need to check
// rest of the items.
child = childFirstInFlow = nullptr;
break;
}
child = *iter;
childFirstInFlow = child->FirstInFlow();
}
}
if (iter.AtEnd()) {
// We've constructed flex items for all children. No need to check
// rest of the lines.
break;
}
}
}
flr.mContentBoxMainSize = data->mContentBoxMainSize;
flr.mContentBoxCrossSize = data->mContentBoxCrossSize;
return flr;
}
// Returns the largest outer hypothetical main-size of any line in |aLines|.
// (i.e. the hypothetical main-size of the largest line)
static AuCoord64 GetLargestLineMainSize(nsTArray<FlexLine>& aLines) {
AuCoord64 largestLineOuterSize = 0;
for (const FlexLine& line : aLines) {
largestLineOuterSize =
std::max(largestLineOuterSize, line.TotalOuterHypotheticalMainSize());
}
return largestLineOuterSize;
}
nscoord nsFlexContainerFrame::ComputeMainSize(
const ReflowInput& aReflowInput, const FlexboxAxisTracker& aAxisTracker,
const nscoord aTentativeContentBoxMainSize,
nsTArray<FlexLine>& aLines) const {
if (aAxisTracker.IsRowOriented()) {
// Row-oriented --> our main axis is the inline axis, so our main size
// is our inline size (which should already be resolved).
return aTentativeContentBoxMainSize;
}
const bool shouldApplyAutomaticMinimumOnBlockAxis =
aReflowInput.ShouldApplyAutomaticMinimumOnBlockAxis();
if (aTentativeContentBoxMainSize != NS_UNCONSTRAINEDSIZE &&
!shouldApplyAutomaticMinimumOnBlockAxis) {
// Column-oriented case, with fixed BSize:
// Just use our fixed block-size because we always assume the available
// block-size is unconstrained, and the reflow input has already done the
// appropriate min/max-BSize clamping.
return aTentativeContentBoxMainSize;
}
// Column-oriented case, with size-containment in block axis:
// Behave as if we had no content and just use our MinBSize.
if (Maybe<nscoord> containBSize =
aReflowInput.mFrame->ContainIntrinsicBSize()) {
return NS_CSS_MINMAX(*containBSize, aReflowInput.ComputedMinBSize(),
aReflowInput.ComputedMaxBSize());
}
const AuCoord64 largestLineMainSize = GetLargestLineMainSize(aLines);
const nscoord contentBSize = NS_CSS_MINMAX(
nscoord(largestLineMainSize.ToMinMaxClamped()),
aReflowInput.ComputedMinBSize(), aReflowInput.ComputedMaxBSize());
// If the clamped largest FlexLine length is larger than the tentative main
// size (which is resolved by aspect-ratio), we extend it to contain the
// entire FlexLine.
// https://drafts.csswg.org/css-sizing-4/#aspect-ratio-minimum
if (shouldApplyAutomaticMinimumOnBlockAxis) {
// Column-oriented case, with auto BSize which is resolved by
// aspect-ratio.
return std::max(contentBSize, aTentativeContentBoxMainSize);
}
// Column-oriented case, with auto BSize:
// Resolve auto BSize to the largest FlexLine length, clamped to our
// computed min/max main-size properties.
return contentBSize;
}
nscoord nsFlexContainerFrame::ComputeCrossSize(
const ReflowInput& aReflowInput, const FlexboxAxisTracker& aAxisTracker,
const nscoord aTentativeContentBoxCrossSize, nscoord aSumLineCrossSizes,
bool* aIsDefinite) const {
MOZ_ASSERT(aIsDefinite, "outparam pointer must be non-null");
if (aAxisTracker.IsColumnOriented()) {
// Column-oriented --> our cross axis is the inline axis, so our cross size
// is our inline size (which should already be resolved).
*aIsDefinite = true;
// FIXME: Bug 1661847 - there are cases where aTentativeContentBoxCrossSize
// (i.e. aReflowInput.ComputedISize()) might not be the right thing to
// return here. Specifically: if our cross size is an intrinsic size, and we
// have flex items that are flexible and have aspect ratios, then we may
// need to take their post-flexing main sizes into account (multiplied
// through their aspect ratios to get their cross sizes), in order to
// determine their flex line's size & the flex container's cross size (e.g.
// as `aSumLineCrossSizes`).
return aTentativeContentBoxCrossSize;
}
const bool shouldApplyAutomaticMinimumOnBlockAxis =
aReflowInput.ShouldApplyAutomaticMinimumOnBlockAxis();
const nscoord computedBSize = aReflowInput.ComputedBSize();
if (computedBSize != NS_UNCONSTRAINEDSIZE &&
!shouldApplyAutomaticMinimumOnBlockAxis) {
// Row-oriented case (cross axis is block-axis), with fixed BSize:
*aIsDefinite = true;
// Just use our fixed block-size because we always assume the available
// block-size is unconstrained, and the reflow input has already done the
// appropriate min/max-BSize clamping.
return computedBSize;
}
// Row-oriented case, with size-containment in block axis:
// Behave as if we had no content and just use our MinBSize.
if (Maybe<nscoord> containBSize =
aReflowInput.mFrame->ContainIntrinsicBSize()) {
*aIsDefinite = true;
return NS_CSS_MINMAX(*containBSize, aReflowInput.ComputedMinBSize(),
aReflowInput.ComputedMaxBSize());
}
// The cross size must not be definite in the following cases.
*aIsDefinite = false;
const nscoord contentBSize =
NS_CSS_MINMAX(aSumLineCrossSizes, aReflowInput.ComputedMinBSize(),
aReflowInput.ComputedMaxBSize());
// If the content block-size is larger than the effective computed
// block-size, we extend the block-size to contain all the content.
// https://drafts.csswg.org/css-sizing-4/#aspect-ratio-minimum
if (shouldApplyAutomaticMinimumOnBlockAxis) {
// Row-oriented case (cross axis is block-axis), with auto BSize which is
// resolved by aspect-ratio or content size.
return std::max(contentBSize, computedBSize);
}
// Row-oriented case (cross axis is block axis), with auto BSize:
// Shrink-wrap our line(s), subject to our min-size / max-size
// constraints in that (block) axis.
return contentBSize;
}
LogicalSize nsFlexContainerFrame::ComputeAvailableSizeForItems(
const ReflowInput& aReflowInput,
const mozilla::LogicalMargin& aBorderPadding) const {
const WritingMode wm = GetWritingMode();
nscoord availableBSize = aReflowInput.AvailableBSize();
if (availableBSize != NS_UNCONSTRAINEDSIZE) {
// Available block-size is constrained. Subtract block-start border and
// padding from it.
availableBSize -= aBorderPadding.BStart(wm);
if (aReflowInput.mStyleBorder->mBoxDecorationBreak ==
StyleBoxDecorationBreak::Clone) {
// We have box-decoration-break:clone. Subtract block-end border and
// padding from the available block-size as well.
availableBSize -= aBorderPadding.BEnd(wm);
}
// Available block-size can became negative after subtracting block-axis
// border and padding. Per spec, to guarantee progress, fragmentainers are
// assumed to have a minimum block size of 1px regardless of their used
// size. https://drafts.csswg.org/css-break/#breaking-rules
availableBSize =
std::max(nsPresContext::CSSPixelsToAppUnits(1), availableBSize);
}
return LogicalSize(wm, aReflowInput.ComputedISize(), availableBSize);
}
void FlexLine::PositionItemsInMainAxis(
const StyleContentDistribution& aJustifyContent,
nscoord aContentBoxMainSize, const FlexboxAxisTracker& aAxisTracker) {
MainAxisPositionTracker mainAxisPosnTracker(
aAxisTracker, this, aJustifyContent, aContentBoxMainSize);
for (FlexItem& item : Items()) {
nscoord itemMainBorderBoxSize =
item.MainSize() + item.BorderPaddingSizeInMainAxis();
// Resolve any main-axis 'auto' margins on aChild to an actual value.
mainAxisPosnTracker.ResolveAutoMarginsInMainAxis(item);
// Advance our position tracker to child's upper-left content-box corner,
// and use that as its position in the main axis.
mainAxisPosnTracker.EnterMargin(item.Margin());
mainAxisPosnTracker.EnterChildFrame(itemMainBorderBoxSize);
item.SetMainPosition(mainAxisPosnTracker.Position());
mainAxisPosnTracker.ExitChildFrame(itemMainBorderBoxSize);
mainAxisPosnTracker.ExitMargin(item.Margin());
mainAxisPosnTracker.TraversePackingSpace();
if (&item != &Items().LastElement()) {
mainAxisPosnTracker.TraverseGap(mMainGapSize);
}
}
}
/**
* Given the flex container's "flex-relative ascent" (i.e. distance from the
* flex container's content-box cross-start edge to its baseline), returns
* its actual physical ascent value (the distance from the *border-box* top
* edge to its baseline).
*/
static nscoord ComputePhysicalAscentFromFlexRelativeAscent(
nscoord aFlexRelativeAscent, nscoord aContentBoxCrossSize,
const ReflowInput& aReflowInput, const FlexboxAxisTracker& aAxisTracker) {
return aReflowInput.ComputedPhysicalBorderPadding().top +
PhysicalCoordFromFlexRelativeCoord(
aFlexRelativeAscent, aContentBoxCrossSize,
aAxisTracker.CrossAxisPhysicalStartSide());
}
void nsFlexContainerFrame::SizeItemInCrossAxis(ReflowInput& aChildReflowInput,
FlexItem& aItem) {
// If cross axis is the item's inline axis, just use ISize from reflow input,
// and don't bother with a full reflow.
if (aItem.IsInlineAxisCrossAxis()) {
aItem.SetCrossSize(aChildReflowInput.ComputedISize());
return;
}
MOZ_ASSERT(!aItem.HadMeasuringReflow(),
"We shouldn't need more than one measuring reflow");
if (aItem.AlignSelf()._0 == StyleAlignFlags::STRETCH) {
// This item's got "align-self: stretch", so we probably imposed a
// stretched computed cross-size on it during its previous
// reflow. We're not imposing that BSize for *this* "measuring" reflow, so
// we need to tell it to treat this reflow as a resize in its block axis
// (regardless of whether any of its ancestors are actually being resized).
// (Note: we know that the cross axis is the item's *block* axis -- if it
// weren't, then we would've taken the early-return above.)
aChildReflowInput.SetBResize(true);
// Not 100% sure this is needed, but be conservative for now:
aChildReflowInput.mFlags.mIsBResizeForPercentages = true;
}
// Potentially reflow the item, and get the sizing info.
const CachedBAxisMeasurement& measurement =
MeasureBSizeForFlexItem(aItem, aChildReflowInput);
// Save the sizing info that we learned from this reflow
// -----------------------------------------------------
// Tentatively store the child's desired content-box cross-size.
aItem.SetCrossSize(measurement.BSize());
}
void FlexLine::PositionItemsInCrossAxis(
nscoord aLineStartPosition, const FlexboxAxisTracker& aAxisTracker) {
SingleLineCrossAxisPositionTracker lineCrossAxisPosnTracker(aAxisTracker);
for (FlexItem& item : Items()) {
// First, stretch the item's cross size (if appropriate), and resolve any
// auto margins in this axis.
item.ResolveStretchedCrossSize(mLineCrossSize);
lineCrossAxisPosnTracker.ResolveAutoMarginsInCrossAxis(*this, item);
// Compute the cross-axis position of this item
nscoord itemCrossBorderBoxSize =
item.CrossSize() + item.BorderPaddingSizeInCrossAxis();
lineCrossAxisPosnTracker.EnterAlignPackingSpace(*this, item, aAxisTracker);
lineCrossAxisPosnTracker.EnterMargin(item.Margin());
lineCrossAxisPosnTracker.EnterChildFrame(itemCrossBorderBoxSize);
item.SetCrossPosition(aLineStartPosition +
lineCrossAxisPosnTracker.Position());
// Back out to cross-axis edge of the line.
lineCrossAxisPosnTracker.ResetPosition();
}
}
void nsFlexContainerFrame::Reflow(nsPresContext* aPresContext,
ReflowOutput& aReflowOutput,
const ReflowInput& aReflowInput,
nsReflowStatus& aStatus) {
if (IsHiddenByContentVisibilityOfInFlowParentForLayout()) {
return;
}
MarkInReflow();
DO_GLOBAL_REFLOW_COUNT("nsFlexContainerFrame");
DISPLAY_REFLOW(aPresContext, this, aReflowInput, aReflowOutput, aStatus);
MOZ_ASSERT(aStatus.IsEmpty(), "Caller should pass a fresh reflow status!");
MOZ_ASSERT(aPresContext == PresContext());
NS_WARNING_ASSERTION(
aReflowInput.ComputedISize() != NS_UNCONSTRAINEDSIZE,
"Unconstrained inline size; this should only result from huge sizes "
"(not intrinsic sizing w/ orthogonal flows)");
FLEX_LOG("Reflow() for nsFlexContainerFrame %p", this);
if (IsFrameTreeTooDeep(aReflowInput, aReflowOutput, aStatus)) {
return;
}
NormalizeChildLists();
#ifdef DEBUG
mDidPushItemsBitMayLie = false;
SanityCheckChildListsBeforeReflow();
#endif // DEBUG
// We (and our children) can only depend on our ancestor's bsize if we have
// a percent-bsize, or if we're positioned and we have "block-start" and
// "block-end" set and have block-size:auto. (There are actually other cases,
// too -- e.g. if our parent is itself a block-dir flex container and we're
// flexible -- but we'll let our ancestors handle those sorts of cases.)
//
// TODO(emilio): the !bsize.IsLengthPercentage() preserves behavior, but it's
// too conservative. min/max-content don't really depend on the container.
WritingMode wm = aReflowInput.GetWritingMode();
const nsStylePosition* stylePos = StylePosition();
const auto& bsize = stylePos->BSize(wm);
if (bsize.HasPercent() || (StyleDisplay()->IsAbsolutelyPositionedStyle() &&
(bsize.IsAuto() || !bsize.IsLengthPercentage()) &&
!stylePos->mOffset.GetBStart(wm).IsAuto() &&
!stylePos->mOffset.GetBEnd(wm).IsAuto())) {
AddStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE);
}
const FlexboxAxisTracker axisTracker(this);
// Check to see if we need to create a computed info structure, to
// be filled out for use by devtools.
ComputedFlexContainerInfo* containerInfo = CreateOrClearFlexContainerInfo();
FlexLayoutResult flr;
PerFragmentFlexData fragmentData;
const nsIFrame* prevInFlow = GetPrevInFlow();
if (!prevInFlow) {
const LogicalSize tentativeContentBoxSize = aReflowInput.ComputedSize();
const nscoord tentativeContentBoxMainSize =
axisTracker.MainComponent(tentativeContentBoxSize);
const nscoord tentativeContentBoxCrossSize =
axisTracker.CrossComponent(tentativeContentBoxSize);
// Calculate gap sizes for main and cross axis. We only need them in
// DoFlexLayout in the first-in-flow, so no need to worry about consumed
// block-size.
const auto& mainGapStyle =
axisTracker.IsRowOriented() ? stylePos->mColumnGap : stylePos->mRowGap;
const auto& crossGapStyle =
axisTracker.IsRowOriented() ? stylePos->mRowGap : stylePos->mColumnGap;
const nscoord mainGapSize = nsLayoutUtils::ResolveGapToLength(
mainGapStyle, tentativeContentBoxMainSize);
const nscoord crossGapSize = nsLayoutUtils::ResolveGapToLength(
crossGapStyle, tentativeContentBoxCrossSize);
// When fragmenting a flex container, we run the flex algorithm without
// regards to pagination in order to compute the flex container's desired
// content-box size. https://drafts.csswg.org/css-flexbox-1/#pagination-algo
//
// Note: For a multi-line column-oriented flex container, the sample
// algorithm suggests we wrap the flex line at the block-end edge of a
// column/page, but we do not implement it intentionally. This brings the
// layout result closer to the one as if there's no fragmentation.
AutoTArray<StrutInfo, 1> struts;
flr = DoFlexLayout(aReflowInput, tentativeContentBoxMainSize,
tentativeContentBoxCrossSize, axisTracker, mainGapSize,
crossGapSize, struts, containerInfo);
if (!struts.IsEmpty()) {
// We're restarting flex layout, with new knowledge of collapsed items.
flr.mLines.Clear();
flr.mPlaceholders.Clear();
flr = DoFlexLayout(aReflowInput, tentativeContentBoxMainSize,
tentativeContentBoxCrossSize, axisTracker, mainGapSize,
crossGapSize, struts, containerInfo);
}
} else {
flr = GenerateFlexLayoutResult();
auto* fragmentDataProp =
prevInFlow->GetProperty(PerFragmentFlexData::Prop());
MOZ_ASSERT(fragmentDataProp,
"PerFragmentFlexData should be set in our prev-in-flow!");
fragmentData = *fragmentDataProp;
}
LogicalSize contentBoxSize = axisTracker.LogicalSizeFromFlexRelativeSizes(
flr.mContentBoxMainSize, flr.mContentBoxCrossSize);
const nscoord consumedBSize = CalcAndCacheConsumedBSize();
const nscoord effectiveContentBSize =
contentBoxSize.BSize(wm) - consumedBSize;
LogicalMargin borderPadding = aReflowInput.ComputedLogicalBorderPadding(wm);
if (MOZ_UNLIKELY(aReflowInput.AvailableBSize() != NS_UNCONSTRAINEDSIZE)) {
// We assume we are the last fragment by using
// PreReflowBlockLevelLogicalSkipSides(), and skip block-end border and
// padding if needed.
borderPadding.ApplySkipSides(PreReflowBlockLevelLogicalSkipSides());
}
// Determine this frame's tentative border-box size. This is used for logical
// to physical coordinate conversion when positioning children.
//
// Note that vertical-rl writing-mode is the only case where the block flow
// direction progresses in a negative physical direction, and therefore block
// direction coordinate conversion depends on knowing the width of the
// coordinate space in order to translate between the logical and physical
// origins. As a result, if our final border-box block-size is different from
// this tentative one, and we are in vertical-rl writing mode, we need to
// adjust our children's position after reflowing them.
const LogicalSize tentativeBorderBoxSize(
wm, contentBoxSize.ISize(wm) + borderPadding.IStartEnd(wm),
std::min(effectiveContentBSize + borderPadding.BStartEnd(wm),
aReflowInput.AvailableBSize()));
const nsSize containerSize = tentativeBorderBoxSize.GetPhysicalSize(wm);
OverflowAreas ocBounds;
nsReflowStatus ocStatus;
if (prevInFlow) {
ReflowOverflowContainerChildren(
aPresContext, aReflowInput, ocBounds, ReflowChildFlags::Default,
ocStatus, MergeSortedFrameListsFor, Some(containerSize));
}
const LogicalSize availableSizeForItems =
ComputeAvailableSizeForItems(aReflowInput, borderPadding);
const auto [maxBlockEndEdgeOfChildren, anyChildIncomplete] =
ReflowChildren(aReflowInput, containerSize, availableSizeForItems,
borderPadding, axisTracker, flr, fragmentData);
bool mayNeedNextInFlow = false;
if (aReflowInput.AvailableBSize() != NS_UNCONSTRAINEDSIZE) {
// maxBlockEndEdgeOfChildren is relative to border-box, so we need to
// subtract block-start border and padding to make it relative to our
// content-box. Note that if there is a packing space in between the last
// flex item's block-end edge and the available space's block-end edge, we
// want to record the available size of item to consume part of the packing
// space.
fragmentData.mCumulativeContentBoxBSize +=
std::max(maxBlockEndEdgeOfChildren - borderPadding.BStart(wm),
availableSizeForItems.BSize(wm));
// mCumulativeBEndEdgeShift was updated in ReflowChildren(). If our
// block-size in unconstrained, use that to grow our block-size, subject to
// min/max constraints.
if (aReflowInput.ComputedBSize() == NS_UNCONSTRAINEDSIZE) {
contentBoxSize.BSize(wm) = aReflowInput.ApplyMinMaxBSize(
contentBoxSize.BSize(wm) + fragmentData.mCumulativeBEndEdgeShift);
}
// Check if we may need a next-in-flow. If so, we'll need to skip block-end
// border and padding.
mayNeedNextInFlow = contentBoxSize.BSize(wm) - consumedBSize >
availableSizeForItems.BSize(wm);
if (mayNeedNextInFlow && aReflowInput.mStyleBorder->mBoxDecorationBreak ==
StyleBoxDecorationBreak::Slice) {
borderPadding.BEnd(wm) = 0;
}
}
PopulateReflowOutput(aReflowOutput, aReflowInput, aStatus, contentBoxSize,
borderPadding, consumedBSize, mayNeedNextInFlow,
maxBlockEndEdgeOfChildren, anyChildIncomplete,
flr.mAscent, flr.mLines, axisTracker);
if (wm.IsVerticalRL()) {
// If the final border-box block-size is different from the tentative one,
// adjust our children's position.
const nscoord deltaBCoord =
tentativeBorderBoxSize.BSize(wm) - aReflowOutput.Size(wm).BSize(wm);
if (deltaBCoord != 0) {
const LogicalPoint delta(wm, 0, deltaBCoord);
for (const FlexLine& line : flr.mLines) {
for (const FlexItem& item : line.Items()) {
item.Frame()->MovePositionBy(wm, delta);
}
}
}
}
// Overflow area = union(my overflow area, children's overflow areas)
aReflowOutput.SetOverflowAreasToDesiredBounds();
UnionInFlowChildOverflow(aReflowOutput.mOverflowAreas);
// Merge overflow container bounds and status.
aReflowOutput.mOverflowAreas.UnionWith(ocBounds);
aStatus.MergeCompletionStatusFrom(ocStatus);
FinishReflowWithAbsoluteFrames(PresContext(), aReflowOutput, aReflowInput,
aStatus);
// Finally update our line and item measurements in our containerInfo.
if (MOZ_UNLIKELY(containerInfo)) {
UpdateFlexLineAndItemInfo(*containerInfo, flr.mLines);
}
// If we are the first-in-flow, we want to store data for our next-in-flows,
// or clear the existing data if it is not needed.
if (!prevInFlow) {
SharedFlexData* sharedData = GetProperty(SharedFlexData::Prop());
if (!aStatus.IsFullyComplete()) {
if (!sharedData) {
sharedData = new SharedFlexData;
SetProperty(SharedFlexData::Prop(), sharedData);
}
sharedData->Update(std::move(flr));
} else if (sharedData && !GetNextInFlow()) {
// We are fully-complete, so no next-in-flow is needed. However, if we
// report SetInlineLineBreakBeforeAndReset() in an incremental reflow, our
// next-in-flow might still exist. It can be reflowed again before us if
// it is an overflow container. Delete the existing data only if we don't
// have a next-in-flow.
RemoveProperty(SharedFlexData::Prop());
}
}
PerFragmentFlexData* fragmentDataProp =
GetProperty(PerFragmentFlexData::Prop());
if (!aStatus.IsFullyComplete()) {
if (!fragmentDataProp) {
fragmentDataProp = new PerFragmentFlexData;
SetProperty(PerFragmentFlexData::Prop(), fragmentDataProp);
}
*fragmentDataProp = fragmentData;
} else if (fragmentDataProp && !GetNextInFlow()) {
// Similar to the condition to remove SharedFlexData, delete the
// existing data only if we don't have a next-in-flow.
RemoveProperty(PerFragmentFlexData::Prop());
}
}
Maybe<nscoord> nsFlexContainerFrame::GetNaturalBaselineBOffset(
WritingMode aWM, BaselineSharingGroup aBaselineGroup,
BaselineExportContext) const {
if (StyleDisplay()->IsContainLayout() ||
HasAnyStateBits(NS_STATE_FLEX_SYNTHESIZE_BASELINE)) {
return Nothing{};
}
return Some(aBaselineGroup == BaselineSharingGroup::First
? mBaselineFromLastReflow
: mLastBaselineFromLastReflow);
}
void nsFlexContainerFrame::UnionInFlowChildOverflow(
OverflowAreas& aOverflowAreas) {
// The CSS Overflow spec [1] requires that a scrollable container's
// scrollable overflow should include the following areas.
//
// a) "the box's own content and padding areas": we treat the *content* as
// the scrolled inner frame's theoretical content-box that's intrinsically
// sized to the union of all the flex items' margin boxes, _without_
// relative positioning applied. The *padding areas* is just inflation on
// top of the theoretical content-box by the flex container's padding.
//
// b) "the margin areas of grid item and flex item boxes for which the box
// establishes a containing block": a) already includes the flex items'
// normal-positioned margin boxes into the scrollable overflow, but their
// relative-positioned margin boxes should also be included because relpos
// children are still flex items.
//
// [1] https://drafts.csswg.org/css-overflow-3/#scrollable.
const bool isScrolledContent =
Style()->GetPseudoType() == PseudoStyleType::scrolledContent;
bool anyScrolledContentItem = false;
// Union of normal-positioned margin boxes for all the items.
nsRect itemMarginBoxes;
// Union of relative-positioned margin boxes for the relpos items only.
nsRect relPosItemMarginBoxes;
const bool useMozBoxCollapseBehavior =
StyleVisibility()->UseLegacyCollapseBehavior();
for (nsIFrame* f : mFrames) {
if (useMozBoxCollapseBehavior && f->StyleVisibility()->IsCollapse()) {
continue;
}
ConsiderChildOverflow(aOverflowAreas, f);
if (!isScrolledContent) {
continue;
}
if (f->IsPlaceholderFrame()) {
continue;
}
anyScrolledContentItem = true;
if (MOZ_UNLIKELY(f->IsRelativelyOrStickyPositioned())) {
const nsRect marginRect = f->GetMarginRectRelativeToSelf();
itemMarginBoxes =
itemMarginBoxes.Union(marginRect + f->GetNormalPosition());
relPosItemMarginBoxes =
relPosItemMarginBoxes.Union(marginRect + f->GetPosition());
} else {
itemMarginBoxes = itemMarginBoxes.Union(f->GetMarginRect());
}
}
if (anyScrolledContentItem) {
itemMarginBoxes.Inflate(GetUsedPadding());
aOverflowAreas.UnionAllWith(itemMarginBoxes);
aOverflowAreas.UnionAllWith(relPosItemMarginBoxes);
}
}
void nsFlexContainerFrame::UnionChildOverflow(OverflowAreas& aOverflowAreas) {
UnionInFlowChildOverflow(aOverflowAreas);
// Union with child frames, skipping the principal list since we already
// handled those above.
nsLayoutUtils::UnionChildOverflow(this, aOverflowAreas,
{FrameChildListID::Principal});
}
void nsFlexContainerFrame::CalculatePackingSpace(
uint32_t aNumThingsToPack, const StyleContentDistribution& aAlignVal,
nscoord* aFirstSubjectOffset, uint32_t* aNumPackingSpacesRemaining,
nscoord* aPackingSpaceRemaining) {
StyleAlignFlags val = aAlignVal.primary;
MOZ_ASSERT(val == StyleAlignFlags::SPACE_BETWEEN ||
val == StyleAlignFlags::SPACE_AROUND ||
val == StyleAlignFlags::SPACE_EVENLY,
"Unexpected alignment value");
MOZ_ASSERT(*aPackingSpaceRemaining >= 0,
"Should not be called with negative packing space");
// Note: In the aNumThingsToPack==1 case, the fallback behavior for
// 'space-between' depends on precise information about the axes that we
// don't have here. So, for that case, we just depend on the caller to
// explicitly convert 'space-{between,around,evenly}' keywords to the
// appropriate fallback alignment and skip this function.
MOZ_ASSERT(aNumThingsToPack > 1,
"Should not be called unless there's more than 1 thing to pack");
// Packing spaces between items:
*aNumPackingSpacesRemaining = aNumThingsToPack - 1;
if (val == StyleAlignFlags::SPACE_BETWEEN) {
// No need to reserve space at beginning/end, so we're done.
return;
}
// We need to add 1 or 2 packing spaces, split between beginning/end, for
// space-around / space-evenly:
size_t numPackingSpacesForEdges =
val == StyleAlignFlags::SPACE_AROUND ? 1 : 2;
// How big will each "full" packing space be:
nscoord packingSpaceSize =
*aPackingSpaceRemaining /
(*aNumPackingSpacesRemaining + numPackingSpacesForEdges);
// How much packing-space are we allocating to the edges:
nscoord totalEdgePackingSpace = numPackingSpacesForEdges * packingSpaceSize;
// Use half of that edge packing space right now:
*aFirstSubjectOffset += totalEdgePackingSpace / 2;
// ...but we need to subtract all of it right away, so that we won't
// hand out any of it to intermediate packing spaces.
*aPackingSpaceRemaining -= totalEdgePackingSpace;
}
ComputedFlexContainerInfo*
nsFlexContainerFrame::CreateOrClearFlexContainerInfo() {
if (!ShouldGenerateComputedInfo()) {
return nullptr;
}
// The flag that sets ShouldGenerateComputedInfo() will never be cleared.
// That's acceptable because it's only set in a Chrome API invoked by
// devtools, and won't impact normal browsing.
// Re-use the ComputedFlexContainerInfo, if it exists.
ComputedFlexContainerInfo* info = GetProperty(FlexContainerInfo());
if (info) {
// We can reuse, as long as we clear out old data.
info->mLines.Clear();
} else {
info = new ComputedFlexContainerInfo();
SetProperty(FlexContainerInfo(), info);
}
return info;
}
void nsFlexContainerFrame::CreateFlexLineAndFlexItemInfo(
ComputedFlexContainerInfo& aContainerInfo,
const nsTArray<FlexLine>& aLines) {
for (const FlexLine& line : aLines) {
ComputedFlexLineInfo* lineInfo = aContainerInfo.mLines.AppendElement();
// Most of the remaining lineInfo properties will be filled out in
// UpdateFlexLineAndItemInfo (some will be provided by other functions),
// when we have real values. But we still add all the items here, so
// we can capture computed data for each item as we proceed.
for (const FlexItem& item : line.Items()) {
nsIFrame* frame = item.Frame();
// The frame may be for an element, or it may be for an
// anonymous flex item, e.g. wrapping one or more text nodes.
// DevTools wants the content node for the actual child in
// the DOM tree, so we descend through anonymous boxes.
nsIFrame* targetFrame = GetFirstNonAnonBoxInSubtree(frame);
nsIContent* content = targetFrame->GetContent();
// Skip over content that is only whitespace, which might
// have been broken off from a text node which is our real
// target.
while (content && content->TextIsOnlyWhitespace()) {
// If content is only whitespace, try the frame sibling.
targetFrame = targetFrame->GetNextSibling();
if (targetFrame) {
content = targetFrame->GetContent();
} else {
content = nullptr;
}
}
ComputedFlexItemInfo* itemInfo = lineInfo->mItems.AppendElement();
itemInfo->mNode = content;
// itemInfo->mMainBaseSize and mMainDeltaSize will be filled out
// in ResolveFlexibleLengths(). Other measurements will be captured in
// UpdateFlexLineAndItemInfo.
}
}
}
void nsFlexContainerFrame::ComputeFlexDirections(
ComputedFlexContainerInfo& aContainerInfo,
const FlexboxAxisTracker& aAxisTracker) {
auto ConvertPhysicalStartSideToFlexPhysicalDirection =
[](mozilla::Side aStartSide) {
switch (aStartSide) {
case eSideLeft:
return dom::FlexPhysicalDirection::Horizontal_lr;
case eSideRight:
return dom::FlexPhysicalDirection::Horizontal_rl;
case eSideTop:
return dom::FlexPhysicalDirection::Vertical_tb;
case eSideBottom:
return dom::FlexPhysicalDirection::Vertical_bt;
}
MOZ_ASSERT_UNREACHABLE("We should handle all sides!");
return dom::FlexPhysicalDirection::Horizontal_lr;
};
aContainerInfo.mMainAxisDirection =
ConvertPhysicalStartSideToFlexPhysicalDirection(
aAxisTracker.MainAxisPhysicalStartSide());
aContainerInfo.mCrossAxisDirection =
ConvertPhysicalStartSideToFlexPhysicalDirection(
aAxisTracker.CrossAxisPhysicalStartSide());
}
void nsFlexContainerFrame::UpdateFlexLineAndItemInfo(
ComputedFlexContainerInfo& aContainerInfo,
const nsTArray<FlexLine>& aLines) {
uint32_t lineIndex = 0;
for (const FlexLine& line : aLines) {
ComputedFlexLineInfo& lineInfo = aContainerInfo.mLines[lineIndex];
lineInfo.mCrossSize = line.LineCrossSize();
lineInfo.mFirstBaselineOffset = line.FirstBaselineOffset();
lineInfo.mLastBaselineOffset = line.LastBaselineOffset();
uint32_t itemIndex = 0;
for (const FlexItem& item : line.Items()) {
ComputedFlexItemInfo& itemInfo = lineInfo.mItems[itemIndex];
itemInfo.mFrameRect = item.Frame()->GetRect();
itemInfo.mMainMinSize = item.MainMinSize();
itemInfo.mMainMaxSize = item.MainMaxSize();
itemInfo.mCrossMinSize = item.CrossMinSize();
itemInfo.mCrossMaxSize = item.CrossMaxSize();
itemInfo.mClampState =
item.WasMinClamped()
? mozilla::dom::FlexItemClampState::Clamped_to_min
: (item.WasMaxClamped()
? mozilla::dom::FlexItemClampState::Clamped_to_max
: mozilla::dom::FlexItemClampState::Unclamped);
++itemIndex;
}
++lineIndex;
}
}
nsFlexContainerFrame* nsFlexContainerFrame::GetFlexFrameWithComputedInfo(
nsIFrame* aFrame) {
// Prepare a lambda function that we may need to call multiple times.
auto GetFlexContainerFrame = [](nsIFrame* aFrame) {
// Return the aFrame's content insertion frame, iff it is
// a flex container frame.
nsFlexContainerFrame* flexFrame = nullptr;
if (aFrame) {
nsIFrame* inner = aFrame;
if (MOZ_UNLIKELY(aFrame->IsFieldSetFrame())) {
inner = static_cast<nsFieldSetFrame*>(aFrame)->GetInner();
}
// Since "Get" methods like GetInner and GetContentInsertionFrame can
// return null, we check the return values before dereferencing. Our
// calling pattern makes this unlikely, but we're being careful.
nsIFrame* insertionFrame =
inner ? inner->GetContentInsertionFrame() : nullptr;
nsIFrame* possibleFlexFrame = insertionFrame ? insertionFrame : aFrame;
flexFrame = possibleFlexFrame->IsFlexContainerFrame()
? static_cast<nsFlexContainerFrame*>(possibleFlexFrame)
: nullptr;
}
return flexFrame;
};
nsFlexContainerFrame* flexFrame = GetFlexContainerFrame(aFrame);
if (flexFrame) {
// Generate the FlexContainerInfo data, if it's not already there.
bool reflowNeeded = !flexFrame->HasProperty(FlexContainerInfo());
if (reflowNeeded) {
// Trigger a reflow that generates additional flex property data.
// Hold onto aFrame while we do this, in case reflow destroys it.
AutoWeakFrame weakFrameRef(aFrame);
RefPtr<mozilla::PresShell> presShell = flexFrame->PresShell();
flexFrame->SetShouldGenerateComputedInfo(true);
presShell->FrameNeedsReflow(flexFrame, IntrinsicDirty::None,
NS_FRAME_IS_DIRTY);
presShell->FlushPendingNotifications(FlushType::Layout);
// Since the reflow may have side effects, get the flex frame
// again. But if the weakFrameRef is no longer valid, then we
// must bail out.
if (!weakFrameRef.IsAlive()) {
return nullptr;
}
flexFrame = GetFlexContainerFrame(weakFrameRef.GetFrame());
NS_WARNING_ASSERTION(
!flexFrame || flexFrame->HasProperty(FlexContainerInfo()),
"The state bit should've made our forced-reflow "
"generate a FlexContainerInfo object");
}
}
return flexFrame;
}
/* static */
bool nsFlexContainerFrame::IsItemInlineAxisMainAxis(nsIFrame* aFrame) {
MOZ_ASSERT(aFrame && aFrame->IsFlexItem(), "expecting arg to be a flex item");
const WritingMode flexItemWM = aFrame->GetWritingMode();
const nsIFrame* flexContainer = aFrame->GetParent();
if (IsLegacyBox(flexContainer)) {
// For legacy boxes, the main axis is determined by "box-orient", and we can
// just directly check if that's vertical, and compare that to whether the
// item's WM is also vertical:
bool boxOrientIsVertical =
flexContainer->StyleXUL()->mBoxOrient == StyleBoxOrient::Vertical;
return flexItemWM.IsVertical() == boxOrientIsVertical;
}
// For modern CSS flexbox, we get our return value by asking two questions
// and comparing their answers.
// Question 1: does aFrame have the same inline axis as its flex container?
bool itemInlineAxisIsParallelToParent =
!flexItemWM.IsOrthogonalTo(flexContainer->GetWritingMode());
// Question 2: is aFrame's flex container row-oriented? (This tells us
// whether the flex container's main axis is its inline axis.)
auto flexDirection = flexContainer->StylePosition()->mFlexDirection;
bool flexContainerIsRowOriented =
flexDirection == StyleFlexDirection::Row ||
flexDirection == StyleFlexDirection::RowReverse;
// aFrame's inline axis is its flex container's main axis IFF the above
// questions have the same answer.
return flexContainerIsRowOriented == itemInlineAxisIsParallelToParent;
}
/* static */
bool nsFlexContainerFrame::IsUsedFlexBasisContent(
const StyleFlexBasis& aFlexBasis, const StyleSize& aMainSize) {
// We have a used flex-basis of 'content' if flex-basis explicitly has that
// value, OR if flex-basis is 'auto' (deferring to the main-size property)
// and the main-size property is also 'auto'.
// See https://drafts.csswg.org/css-flexbox-1/#valdef-flex-basis-auto
if (aFlexBasis.IsContent()) {
return true;
}
return aFlexBasis.IsAuto() && aMainSize.IsAuto();
}
nsFlexContainerFrame::FlexLayoutResult nsFlexContainerFrame::DoFlexLayout(
const ReflowInput& aReflowInput, const nscoord aTentativeContentBoxMainSize,
const nscoord aTentativeContentBoxCrossSize,
const FlexboxAxisTracker& aAxisTracker, nscoord aMainGapSize,
nscoord aCrossGapSize, nsTArray<StrutInfo>& aStruts,
ComputedFlexContainerInfo* const aContainerInfo) {
FlexLayoutResult flr;
GenerateFlexLines(aReflowInput, aTentativeContentBoxMainSize,
aTentativeContentBoxCrossSize, aStruts, aAxisTracker,
aMainGapSize, flr.mPlaceholders, flr.mLines,
flr.mHasCollapsedItems);
if ((flr.mLines.Length() == 1 && flr.mLines[0].IsEmpty()) ||
aReflowInput.mStyleDisplay->IsContainLayout()) {
// We have no flex items, or we're layout-contained. So, we have no
// baseline, and our parent should synthesize a baseline if needed.
AddStateBits(NS_STATE_FLEX_SYNTHESIZE_BASELINE);
} else {
RemoveStateBits(NS_STATE_FLEX_SYNTHESIZE_BASELINE);
}
// Construct our computed info if we've been asked to do so. This is
// necessary to do now so we can capture some computed values for
// FlexItems during layout that would not otherwise be saved (like
// size adjustments). We'll later fix up the line properties,
// because the correct values aren't available yet.
if (aContainerInfo) {
MOZ_ASSERT(ShouldGenerateComputedInfo(),
"We should only have the info struct if "
"ShouldGenerateComputedInfo() is true!");
if (!aStruts.IsEmpty()) {
// We restarted DoFlexLayout, and may have stale mLines to clear:
aContainerInfo->mLines.Clear();
} else {
MOZ_ASSERT(aContainerInfo->mLines.IsEmpty(), "Shouldn't have lines yet.");
}
CreateFlexLineAndFlexItemInfo(*aContainerInfo, flr.mLines);
ComputeFlexDirections(*aContainerInfo, aAxisTracker);
}
flr.mContentBoxMainSize = ComputeMainSize(
aReflowInput, aAxisTracker, aTentativeContentBoxMainSize, flr.mLines);
uint32_t lineIndex = 0;
for (FlexLine& line : flr.mLines) {
ComputedFlexLineInfo* lineInfo =
aContainerInfo ? &aContainerInfo->mLines[lineIndex] : nullptr;
line.ResolveFlexibleLengths(flr.mContentBoxMainSize, lineInfo);
++lineIndex;
}
// Cross Size Determination - Flexbox spec section 9.4
// https://drafts.csswg.org/css-flexbox-1/#cross-sizing
// ===================================================
// Calculate the hypothetical cross size of each item:
// 'sumLineCrossSizes' includes the size of all gaps between lines. We
// initialize it with the sum of all the gaps, and add each line's cross size
// at the end of the following for-loop.
nscoord sumLineCrossSizes = aCrossGapSize * (flr.mLines.Length() - 1);
for (FlexLine& line : flr.mLines) {
for (FlexItem& item : line.Items()) {
// The item may already have the correct cross-size; only recalculate
// if the item's main size resolution (flexing) could have influenced it:
if (item.CanMainSizeInfluenceCrossSize()) {
StyleSizeOverrides sizeOverrides;
if (item.IsInlineAxisMainAxis()) {
sizeOverrides.mStyleISize.emplace(item.StyleMainSize());
} else {
sizeOverrides.mStyleBSize.emplace(item.StyleMainSize());
}
FLEX_LOG("Sizing flex item %p in cross axis", item.Frame());
FLEX_LOGV(" Main size override: %d", item.MainSize());
const WritingMode wm = item.GetWritingMode();
LogicalSize availSize = aReflowInput.ComputedSize(wm);
availSize.BSize(wm) = NS_UNCONSTRAINEDSIZE;
ReflowInput childReflowInput(PresContext(), aReflowInput, item.Frame(),
availSize, Nothing(), {}, sizeOverrides);
if (item.IsBlockAxisMainAxis() && item.TreatBSizeAsIndefinite()) {
childReflowInput.mFlags.mTreatBSizeAsIndefinite = true;
}
SizeItemInCrossAxis(childReflowInput, item);
}
}
// Now that we've finished with this line's items, size the line itself:
line.ComputeCrossSizeAndBaseline(aAxisTracker);
sumLineCrossSizes += line.LineCrossSize();
}
bool isCrossSizeDefinite;
flr.mContentBoxCrossSize = ComputeCrossSize(
aReflowInput, aAxisTracker, aTentativeContentBoxCrossSize,
sumLineCrossSizes, &isCrossSizeDefinite);
// Set up state for cross-axis alignment, at a high level (outside the
// scope of a particular flex line)
CrossAxisPositionTracker crossAxisPosnTracker(
flr.mLines, aReflowInput, flr.mContentBoxCrossSize, isCrossSizeDefinite,
aAxisTracker, aCrossGapSize);
// Now that we know the cross size of each line (including
// "align-content:stretch" adjustments, from the CrossAxisPositionTracker
// constructor), we can create struts for any flex items with
// "visibility: collapse" (and restart flex layout).
// Make sure to only do this if we had no struts.
if (aStruts.IsEmpty() && flr.mHasCollapsedItems &&
!StyleVisibility()->UseLegacyCollapseBehavior()) {
BuildStrutInfoFromCollapsedItems(flr.mLines, aStruts);
if (!aStruts.IsEmpty()) {
// Restart flex layout, using our struts.
return flr;
}
}
// If the container should derive its baseline from the first FlexLine,
// do that here (while crossAxisPosnTracker is conveniently pointing
// at the cross-start edge of that line, which the line's baseline offset is
// measured from):
if (nscoord firstLineBaselineOffset = flr.mLines[0].FirstBaselineOffset();
firstLineBaselineOffset == nscoord_MIN) {
// No baseline-aligned items in line. Use sentinel value to prompt us to
// get baseline from the first FlexItem after we've reflowed it.
flr.mAscent = nscoord_MIN;
} else {
flr.mAscent = ComputePhysicalAscentFromFlexRelativeAscent(
crossAxisPosnTracker.Position() + firstLineBaselineOffset,
flr.mContentBoxCrossSize, aReflowInput, aAxisTracker);
}
const auto justifyContent =
IsLegacyBox(aReflowInput.mFrame)
? ConvertLegacyStyleToJustifyContent(StyleXUL())
: aReflowInput.mStylePosition->mJustifyContent;
lineIndex = 0;
for (FlexLine& line : flr.mLines) {
// Main-Axis Alignment - Flexbox spec section 9.5
// https://drafts.csswg.org/css-flexbox-1/#main-alignment
// ==============================================
line.PositionItemsInMainAxis(justifyContent, flr.mContentBoxMainSize,
aAxisTracker);
// See if we need to extract some computed info for this line.
if (MOZ_UNLIKELY(aContainerInfo)) {
ComputedFlexLineInfo& lineInfo = aContainerInfo->mLines[lineIndex];
lineInfo.mCrossStart = crossAxisPosnTracker.Position();
}
// Cross-Axis Alignment - Flexbox spec section 9.6
// https://drafts.csswg.org/css-flexbox-1/#cross-alignment
// ===============================================
line.PositionItemsInCrossAxis(crossAxisPosnTracker.Position(),
aAxisTracker);
crossAxisPosnTracker.TraverseLine(line);
crossAxisPosnTracker.TraversePackingSpace();
if (&line != &flr.mLines.LastElement()) {
crossAxisPosnTracker.TraverseGap();
}
++lineIndex;
}
return flr;
}
// This data structure is used in fragmentation, storing the block coordinate
// metrics when reflowing 1) the BStart-most line in each fragment of a
// row-oriented flex container or, 2) the BStart-most item in each fragment of a
// single-line column-oriented flex container.
//
// When we lay out a row-oriented flex container fragment, its first line might
// contain one or more monolithic items that were pushed from the previous
// fragment specifically to avoid having those monolithic items overlap the
// page/column break. The situation is similar for single-row column-oriented
// flex container fragments, but a bit simpler; only their first item might have
// been pushed to avoid overlapping a page/column break.
//
// We'll have to place any such pushed items at the block-start edge of the
// current fragment's content-box, which is as close as we can get them to their
// theoretical/unfragmented position (without slicing them); but it does
// represent a shift away from their theoretical/unfragmented position (which
// was somewhere in the previous fragment).
//
// When that happens, we need to record the maximum such shift that we had to
// perform so that we can apply the same block-endwards shift to "downstream"
// items (items towards the block-end edge) that we could otherwise collide
// with. We also potentially apply the same shift when computing the block-end
// edge of this flex container fragment's content-box so that we don't
// inadvertently shift the last item (or line-of-items) to overlap the flex
// container's border, or content beyond the flex container.
//
// We use this structure to keep track of several metrics, in service of this
// goal. This structure is also necessary to adjust PerFragmentFlexData at the
// end of ReflowChildren().
//
// Note: "First" in the struct name means "BStart-most", not the order in the
// flex line array or flex item array.
//
// TODO: Currently, we assume (for proper fragmentation) that the main-axis (or
// cross-axis) is in the same direction as the corresponding writing-mode
// inline-axis (or block-axis). Bug 1812485 will support pushing tall flex items
// for flex containers with a "reversed" main-axis (or cross-axis).
struct FirstLineOrFirstItemBAxisMetrics final {
// This value stores the block-end edge shift for 1) the BStart-most line in
// the current fragment of a row-oriented flex container, or 2) the
// BStart-most item in the current fragment of a single-line column-oriented
// flex container. This number is non-negative.
//
// This value may become positive when any item is a first-in-flow and also
// satisfies either the above condition 1) or 2), since that's a hint that it
// could be monolithic or have a monolithic first descendant, and therefore an
// item that might incur a page/column-break-dodging position-shift that this
// variable needs to track.
nscoord mBEndEdgeShift = 0;
// The first and second value in the pair store the max block-end edges for
// items before and after applying the per-item position-shift in the block
// axis. We only record the block-end edges for items with first-in-flow
// frames placed in the current flex container fragment. This is used only by
// row-oriented flex containers.
Maybe<std::pair<nscoord, nscoord>> mMaxBEndEdge;
};
std::tuple<nscoord, bool> nsFlexContainerFrame::ReflowChildren(
const ReflowInput& aReflowInput, const nsSize& aContainerSize,
const LogicalSize& aAvailableSizeForItems,
const LogicalMargin& aBorderPadding, const FlexboxAxisTracker& aAxisTracker,
FlexLayoutResult& aFlr, PerFragmentFlexData& aFragmentData) {
if (HidesContentForLayout()) {
return {0, false};
}
// Before giving each child a final reflow, calculate the origin of the
// flex container's content box (with respect to its border-box), so that
// we can compute our flex item's final positions.
WritingMode flexWM = aReflowInput.GetWritingMode();
const LogicalPoint containerContentBoxOrigin(
flexWM, aBorderPadding.IStart(flexWM), aBorderPadding.BStart(flexWM));
// If the flex container has no baseline-aligned items, it will use the first
// item to determine its baseline:
const FlexItem* firstItem =
aFlr.mLines[0].IsEmpty() ? nullptr : &aFlr.mLines[0].FirstItem();
// The block-end of children is relative to the flex container's border-box.
nscoord maxBlockEndEdgeOfChildren = containerContentBoxOrigin.B(flexWM);
FirstLineOrFirstItemBAxisMetrics bAxisMetrics;
FrameHashtable pushedItems;
FrameHashtable incompleteItems;
FrameHashtable overflowIncompleteItems;
const bool isSingleLine =
StyleFlexWrap::Nowrap == aReflowInput.mStylePosition->mFlexWrap;
// FINAL REFLOW: Give each child frame another chance to reflow, now that
// we know its final size and position.
for (const FlexLine& line : aFlr.mLines) {
const bool isInFirstLine = &line == &aFlr.mLines[0];
for (const FlexItem& item : line.Items()) {
LogicalPoint framePos = aAxisTracker.LogicalPointFromFlexRelativePoint(
item.MainPosition(), item.CrossPosition(), aFlr.mContentBoxMainSize,
aFlr.mContentBoxCrossSize);
// This variable records the item's block-end edge before we give it a
// per-item-position-shift, if the item is a first-in-flow in the first
// line of a row-oriented flex container fragment. It is used to determine
// the block-end edge shift for the first line at the end of the outer
// loop.
Maybe<nscoord> frameBPosBeforePerItemShift;
if (item.Frame()->GetPrevInFlow()) {
// The item is a continuation. Lay it out at the beginning of the
// available space.
framePos.B(flexWM) = 0;
} else if (GetPrevInFlow()) {
// The item we're placing is not a continuation; though we're placing it
// into a flex container fragment which *is* a continuation. To compute
// the item's correct position in this fragment, we adjust the item's
// theoretical/unfragmented block-direction position by subtracting the
// cumulative content-box block-size for all the previous fragments and
// adding the cumulative block-end edge shift.
//
// Note that the item's position in this fragment has not been finalized
// yet. At this point, we've adjusted the item's
// theoretical/unfragmented position to be relative to the block-end
// edge of the previous container fragment's content-box. Later, we'll
// compute per-item position-shift to finalize its position.
framePos.B(flexWM) -= aFragmentData.mCumulativeContentBoxBSize;
framePos.B(flexWM) += aFragmentData.mCumulativeBEndEdgeShift;
// This helper gets the per-item position-shift in the block-axis.
auto GetPerItemPositionShiftToBEnd = [&]() {
if (framePos.B(flexWM) >= 0) {
// The item final position might be in current flex container
// fragment or in any of the later fragments. No adjustment needed.
return 0;
}
// The item's block position is negative, but we want to place it at
// the content-box block-start edge of this container fragment. To
// achieve this, return a negated (positive) value to make the final
// block position zero.
//
// This scenario occurs when fragmenting a row-oriented flex container
// where this item is pushed to this container fragment.
return -framePos.B(flexWM);
};
if (aAxisTracker.IsRowOriented()) {
if (isInFirstLine) {
frameBPosBeforePerItemShift.emplace(framePos.B(flexWM));
framePos.B(flexWM) += GetPerItemPositionShiftToBEnd();
} else {
// We've computed how far the block-end edge of the first line had
// to shift at the end of outer loop. Here, we just shift all items
// in rest of the lines by the same amount.
framePos.B(flexWM) += bAxisMetrics.mBEndEdgeShift;
}
} else {
MOZ_ASSERT(aAxisTracker.IsColumnOriented());
if (isSingleLine) {
if (&item == firstItem) {
bAxisMetrics.mBEndEdgeShift = GetPerItemPositionShiftToBEnd();
}
framePos.B(flexWM) += bAxisMetrics.mBEndEdgeShift;
} else {
// Bug 1806717: We need a more sophisticated solution for multi-line
// column-oriented flex container when each line has a different
// position-shift value. For now, we don't shift them.
}
}
}
// Adjust available block-size for the item. (We compute it here because
// framePos is still relative to the container's content-box.)
//
// Note: The available block-size can become negative if item's
// block-direction position is below available space's block-end.
const nscoord availableBSizeForItem =
aAvailableSizeForItems.BSize(flexWM) == NS_UNCONSTRAINEDSIZE
? NS_UNCONSTRAINEDSIZE
: aAvailableSizeForItems.BSize(flexWM) - framePos.B(flexWM);
// Adjust framePos to be relative to the container's border-box
// (i.e. its frame rect), instead of the container's content-box:
framePos += containerContentBoxOrigin;
// Check if we actually need to reflow the item -- if the item's position
// is below the available space's block-end, push it to our next-in-flow;
// if it does need a reflow, and we already reflowed it with the right
// content-box size.
const bool childBPosExceedAvailableSpaceBEnd =
availableBSizeForItem != NS_UNCONSTRAINEDSIZE &&
availableBSizeForItem <= 0;
bool itemInPushedItems = false;
if (childBPosExceedAvailableSpaceBEnd) {
// Note: Even if all of our items are beyond the available space & get
// pushed here, we'll be guaranteed to place at least one of them (and
// make progress) in one of the flex container's *next* fragment. It's
// because ComputeAvailableSizeForItems() always reserves at least 1px
// available block-size for its children, and we consume all available
// block-size and add it to
// PerFragmentFlexData::mCumulativeContentBoxBSize even if we are not
// laying out any child.
FLEX_LOG(
"[frag] Flex item %p needed to be pushed to container's "
"next-in-flow due to position below available space's block-end",
item.Frame());
pushedItems.Insert(item.Frame());
itemInPushedItems = true;
} else if (item.NeedsFinalReflow(aReflowInput)) {
// The available size must be in item's writing-mode.
const WritingMode itemWM = item.GetWritingMode();
const auto availableSize =
LogicalSize(flexWM, aAvailableSizeForItems.ISize(flexWM),
availableBSizeForItem)
.ConvertTo(itemWM, flexWM);
const nsReflowStatus childReflowStatus =
ReflowFlexItem(aAxisTracker, aReflowInput, item, framePos,
availableSize, aContainerSize);
const bool shouldPushItem = [&]() {
if (availableBSizeForItem == NS_UNCONSTRAINEDSIZE) {
// If the available block-size is unconstrained, then we're not
// fragmenting and we don't want to push the item.
return false;
}
if (framePos.B(flexWM) == containerContentBoxOrigin.B(flexWM)) {
// The flex item is adjacent with block-start of the container's
// content-box. Don't push it, or we'll trap in an infinite loop.
return false;
}
if (item.Frame()->BSize() <= availableBSizeForItem) {
return false;
}
if (aAxisTracker.IsColumnOriented() &&
item.Frame()->StyleDisplay()->mBreakBefore ==
StyleBreakBetween::Avoid) {
return false;
}
return true;
}();
if (shouldPushItem) {
FLEX_LOG(
"[frag] Flex item %p needed to be pushed to container's "
"next-in-flow because its block-size is larger than the "
"available space",
item.Frame());
pushedItems.Insert(item.Frame());
itemInPushedItems = true;
} else if (childReflowStatus.IsIncomplete()) {
incompleteItems.Insert(item.Frame());
} else if (childReflowStatus.IsOverflowIncomplete()) {
overflowIncompleteItems.Insert(item.Frame());
}
} else {
MoveFlexItemToFinalPosition(item, framePos, aContainerSize);
}
if (!itemInPushedItems) {
const nscoord itemBSize = item.Frame()->BSize(flexWM);
const nscoord bEndEdgeAfterPerItemShift =
framePos.B(flexWM) + itemBSize;
// The item (or a fragment thereof) was placed in this flex container
// fragment. Update the max block-end edge with the item's block-end
// edge.
maxBlockEndEdgeOfChildren =
std::max(maxBlockEndEdgeOfChildren, bEndEdgeAfterPerItemShift);
if (frameBPosBeforePerItemShift) {
// Make the block-end edge relative to flex container's border-box
// because bEndEdgeAfterPerItemShift is relative to the border-box.
const nscoord bEndEdgeBeforePerItemShift =
containerContentBoxOrigin.B(flexWM) +
*frameBPosBeforePerItemShift + itemBSize;
if (bAxisMetrics.mMaxBEndEdge) {
auto& [before, after] = *bAxisMetrics.mMaxBEndEdge;
before = std::max(before, bEndEdgeBeforePerItemShift);
after = std::max(after, bEndEdgeAfterPerItemShift);
} else {
bAxisMetrics.mMaxBEndEdge.emplace(bEndEdgeBeforePerItemShift,
bEndEdgeAfterPerItemShift);
}
}
}
// If the item has auto margins, and we were tracking the UsedMargin
// property, set the property to the computed margin values.
if (item.HasAnyAutoMargin()) {
nsMargin* propValue =
item.Frame()->GetProperty(nsIFrame::UsedMarginProperty());
if (propValue) {
*propValue = item.PhysicalMargin();
}
}
// If this is our first item and we haven't established a baseline for
// the container yet (i.e. if we don't have 'align-self: baseline' on any
// children), then use this child's first baseline as the container's
// baseline.
if (&item == firstItem && aFlr.mAscent == nscoord_MIN) {
aFlr.mAscent = framePos.B(flexWM) + item.ResolvedAscent(true);
}
}
// Now we've finished processing all the items in the first line. Determine
// the amount by which the first line's block-end edge has shifted, so we
// can apply the same shift for the remaining lines.
if (GetPrevInFlow() && aAxisTracker.IsRowOriented() && isInFirstLine &&
bAxisMetrics.mMaxBEndEdge) {
auto& [before, after] = *bAxisMetrics.mMaxBEndEdge;
bAxisMetrics.mBEndEdgeShift = after - before;
}
}
if (!aFlr.mPlaceholders.IsEmpty()) {
ReflowPlaceholders(aReflowInput, aFlr.mPlaceholders,
containerContentBoxOrigin, aContainerSize);
}
const bool anyChildIncomplete = PushIncompleteChildren(
pushedItems, incompleteItems, overflowIncompleteItems);
// TODO: Try making this a fatal assertion after we fix bug 1751260.
NS_ASSERTION(!anyChildIncomplete ||
aAvailableSizeForItems.BSize(flexWM) != NS_UNCONSTRAINEDSIZE,
"We shouldn't have any incomplete children if the available "
"block-size is unconstrained!");
if (!pushedItems.IsEmpty()) {
AddStateBits(NS_STATE_FLEX_DID_PUSH_ITEMS);
}
if (GetPrevInFlow()) {
aFragmentData.mCumulativeBEndEdgeShift += bAxisMetrics.mBEndEdgeShift;
}
return {maxBlockEndEdgeOfChildren, anyChildIncomplete};
}
void nsFlexContainerFrame::PopulateReflowOutput(
ReflowOutput& aReflowOutput, const ReflowInput& aReflowInput,
nsReflowStatus& aStatus, const LogicalSize& aContentBoxSize,
const LogicalMargin& aBorderPadding, const nscoord aConsumedBSize,
const bool aMayNeedNextInFlow, const nscoord aMaxBlockEndEdgeOfChildren,
const bool aAnyChildIncomplete, nscoord aFlexContainerAscent,
nsTArray<FlexLine>& aLines, const FlexboxAxisTracker& aAxisTracker) {
const WritingMode flexWM = aReflowInput.GetWritingMode();
// Compute flex container's desired size (in its own writing-mode).
LogicalSize desiredSizeInFlexWM(flexWM);
desiredSizeInFlexWM.ISize(flexWM) =
aContentBoxSize.ISize(flexWM) + aBorderPadding.IStartEnd(flexWM);
// Unconditionally skip adding block-end border and padding for now. We add it
// lower down, after we've established baseline and decided whether bottom
// border-padding fits (if we're fragmented).
const nscoord effectiveContentBSizeWithBStartBP =
aContentBoxSize.BSize(flexWM) - aConsumedBSize +
aBorderPadding.BStart(flexWM);
nscoord blockEndContainerBP = aBorderPadding.BEnd(flexWM);
if (aMayNeedNextInFlow) {
// We assume our status should be reported as incomplete because we may need
// a next-in-flow.
bool isStatusIncomplete = true;
const nscoord availableBSizeMinusBEndBP =
aReflowInput.AvailableBSize() - aBorderPadding.BEnd(flexWM);
if (aMaxBlockEndEdgeOfChildren <= availableBSizeMinusBEndBP) {
// Consume all the available block-size.
desiredSizeInFlexWM.BSize(flexWM) = availableBSizeMinusBEndBP;
} else {
// This case happens if we have some tall unbreakable children exceeding
// the available block-size.
desiredSizeInFlexWM.BSize(flexWM) = std::min(
effectiveContentBSizeWithBStartBP, aMaxBlockEndEdgeOfChildren);
if ((aReflowInput.ComputedBSize() != NS_UNCONSTRAINEDSIZE ||
!aAnyChildIncomplete) &&
aMaxBlockEndEdgeOfChildren >= effectiveContentBSizeWithBStartBP) {
// We have some tall unbreakable child that's sticking off the end of
// our fragment, *and* forcing us to consume all of our remaining
// content block-size and call ourselves complete.
//
// - If we have a definite block-size: we get here if the tall child
// makes us reach that block-size.
// - If we have a content-based block-size: we get here if the tall
// child makes us reach the content-based block-size from a
// theoretical unfragmented layout, *and* all our children are
// complete. (Note that if we have some incomplete child, then we
// instead prefer to return an incomplete status, so we can get a
// next-in-flow to include that child's requested next-in-flow, in the
// spirit of having a block-size that fits the content.)
//
// TODO: the auto-height case might need more subtlety; see bug 1828977.
isStatusIncomplete = false;
// We also potentially need to get the unskipped block-end border and
// padding (if we assumed it'd be skipped as part of our tentative
// assumption that we'd be incomplete).
if (aReflowInput.mStyleBorder->mBoxDecorationBreak ==
StyleBoxDecorationBreak::Slice) {
blockEndContainerBP =
aReflowInput.ComputedLogicalBorderPadding(flexWM).BEnd(flexWM);
}
}
}
if (isStatusIncomplete) {
aStatus.SetIncomplete();
}
} else {
// Our own effective content-box block-size can fit within the available
// block-size.
desiredSizeInFlexWM.BSize(flexWM) = effectiveContentBSizeWithBStartBP;
}
if (aFlexContainerAscent == nscoord_MIN) {
// Still don't have our baseline set -- this happens if we have no
// children, if our children are huge enough that they have nscoord_MIN
// as their baseline, or our content is hidden in which case, we'll use the
// wrong baseline (but no big deal).
NS_WARNING_ASSERTION(
HidesContentForLayout() || aLines[0].IsEmpty(),
"Have flex items but didn't get an ascent - that's odd (or there are "
"just gigantic sizes involved)");
// Per spec, synthesize baseline from the flex container's content box
// (i.e. use block-end side of content-box)
// XXXdholbert This only makes sense if parent's writing mode is
// horizontal (& even then, really we should be using the BSize in terms
// of the parent's writing mode, not ours). Clean up in bug 1155322.
aFlexContainerAscent = desiredSizeInFlexWM.BSize(flexWM);
}
if (HasAnyStateBits(NS_STATE_FLEX_SYNTHESIZE_BASELINE)) {
// This will force our parent to call GetLogicalBaseline, which will
// synthesize a margin-box baseline.
aReflowOutput.SetBlockStartAscent(ReflowOutput::ASK_FOR_BASELINE);
} else {
// XXXdholbert aFlexContainerAscent needs to be in terms of
// our parent's writing-mode here. See bug 1155322.
aReflowOutput.SetBlockStartAscent(aFlexContainerAscent);
}
// Now, we account for how the block-end border and padding (if any) impacts
// our desired size. If adding it pushes us over the available block-size,
// then we become incomplete (unless we already weren't asking for any
// block-size, in which case we stay complete to avoid looping forever).
//
// NOTE: If we have auto block-size, we allow our block-end border and padding
// to push us over the available block-size without requesting a continuation,
// for consistency with the behavior of "display:block" elements.
const nscoord effectiveContentBSizeWithBStartEndBP =
desiredSizeInFlexWM.BSize(flexWM) + blockEndContainerBP;
if (aReflowInput.AvailableBSize() != NS_UNCONSTRAINEDSIZE &&
effectiveContentBSizeWithBStartEndBP > aReflowInput.AvailableBSize() &&
desiredSizeInFlexWM.BSize(flexWM) != 0 &&
aReflowInput.ComputedBSize() != NS_UNCONSTRAINEDSIZE) {
// We couldn't fit with the block-end border and padding included, so we'll
// need a continuation.
aStatus.SetIncomplete();
if (aReflowInput.mStyleBorder->mBoxDecorationBreak ==
StyleBoxDecorationBreak::Slice) {
blockEndContainerBP = 0;
}
}
// The variable "blockEndContainerBP" now accurately reflects how much (if
// any) block-end border and padding we want for this frame, so we can proceed
// to add it in.
desiredSizeInFlexWM.BSize(flexWM) += blockEndContainerBP;
if (aStatus.IsComplete() && aAnyChildIncomplete) {
aStatus.SetOverflowIncomplete();
aStatus.SetNextInFlowNeedsReflow();
}
// If we are the first-in-flow and not fully complete (either our block-size
// or any of our flex items cannot fit in the available block-size), and the
// style requires us to avoid breaking inside, set the status to prompt our
// parent to push us to the next page/column.
if (!GetPrevInFlow() && !aStatus.IsFullyComplete() &&
ShouldAvoidBreakInside(aReflowInput)) {
aStatus.SetInlineLineBreakBeforeAndReset();
return;
}
// Calculate the container baselines so that our parent can baseline-align us.
mBaselineFromLastReflow = aFlexContainerAscent;
mLastBaselineFromLastReflow = aLines.LastElement().LastBaselineOffset();
if (mLastBaselineFromLastReflow == nscoord_MIN) {
// XXX we fall back to a mirrored first baseline here for now, but this
// should probably use the last baseline of the last item or something.
mLastBaselineFromLastReflow =
desiredSizeInFlexWM.BSize(flexWM) - aFlexContainerAscent;
}
// Convert flex container's final desired size to parent's WM, for outparam.
aReflowOutput.SetSize(flexWM, desiredSizeInFlexWM);
}
void nsFlexContainerFrame::MoveFlexItemToFinalPosition(
const FlexItem& aItem, const LogicalPoint& aFramePos,
const nsSize& aContainerSize) {
const WritingMode outerWM = aItem.ContainingBlockWM();
const nsStyleDisplay* display = aItem.Frame()->StyleDisplay();
LogicalPoint pos(aFramePos);
if (display->IsRelativelyOrStickyPositionedStyle()) {
// If the item is relatively positioned, look up its offsets (cached from
// previous reflow). A sticky positioned item can pass a dummy
// logicalOffsets into ApplyRelativePositioning().
LogicalMargin logicalOffsets(outerWM);
if (display->IsRelativelyPositionedStyle()) {
nsMargin* cachedOffsets =
aItem.Frame()->GetProperty(nsIFrame::ComputedOffsetProperty());
MOZ_ASSERT(
cachedOffsets,
"relpos previously-reflowed frame should've cached its offsets");
logicalOffsets = LogicalMargin(outerWM, *cachedOffsets);
}
ReflowInput::ApplyRelativePositioning(aItem.Frame(), outerWM,
logicalOffsets, &pos, aContainerSize);
}
FLEX_LOG("Moving flex item %p to its desired position %s", aItem.Frame(),
ToString(pos).c_str());
aItem.Frame()->SetPosition(outerWM, pos, aContainerSize);
PositionFrameView(aItem.Frame());
PositionChildViews(aItem.Frame());
}
nsReflowStatus nsFlexContainerFrame::ReflowFlexItem(
const FlexboxAxisTracker& aAxisTracker, const ReflowInput& aReflowInput,
const FlexItem& aItem, const LogicalPoint& aFramePos,
const LogicalSize& aAvailableSize, const nsSize& aContainerSize) {
FLEX_LOG("Doing final reflow for flex item %p", aItem.Frame());
WritingMode outerWM = aReflowInput.GetWritingMode();
StyleSizeOverrides sizeOverrides;
// Override flex item's main size.
if (aItem.IsInlineAxisMainAxis()) {
sizeOverrides.mStyleISize.emplace(aItem.StyleMainSize());
FLEX_LOGV(" Main size (inline-size) override: %d", aItem.MainSize());
} else {
sizeOverrides.mStyleBSize.emplace(aItem.StyleMainSize());
FLEX_LOGV(" Main size (block-size) override: %d", aItem.MainSize());
}
// Override flex item's cross size if it was stretched in the cross axis (in
// which case we're imposing a cross size).
if (aItem.IsStretched()) {
if (aItem.IsInlineAxisCrossAxis()) {
sizeOverrides.mStyleISize.emplace(aItem.StyleCrossSize());
FLEX_LOGV(" Cross size (inline-size) override: %d", aItem.CrossSize());
} else {
sizeOverrides.mStyleBSize.emplace(aItem.StyleCrossSize());
FLEX_LOGV(" Cross size (block-size) override: %d", aItem.CrossSize());
}
}
if (sizeOverrides.mStyleBSize) {
// We are overriding the block-size. For robustness, we always assume that
// this represents a block-axis resize for the frame. This may be
// conservative, but we do capture all the conditions in the block-axis
// (checked in NeedsFinalReflow()) that make this item require a final
// reflow. This sets relevant flags in ReflowInput::InitResizeFlags().
aItem.Frame()->SetHasBSizeChange(true);
}
ReflowInput childReflowInput(PresContext(), aReflowInput, aItem.Frame(),
aAvailableSize, Nothing(), {}, sizeOverrides);
if (aItem.TreatBSizeAsIndefinite() && aItem.IsBlockAxisMainAxis()) {
childReflowInput.mFlags.mTreatBSizeAsIndefinite = true;
}
if (aItem.IsStretched() && aItem.IsBlockAxisCrossAxis()) {
// This item is stretched (in the cross axis), and that axis is its block
// axis. That stretching effectively gives it a relative BSize.
// XXXdholbert This flag only makes a difference if we use the flex items'
// frame-state when deciding whether to reflow them -- and we don't, as of
// the changes in bug 851607. So this has no effect right now, but it might
// make a difference if we optimize to use dirty bits in the
// future. (Reftests flexbox-resizeviewport-1.xhtml and -2.xhtml are
// intended to catch any regressions here, if we end up relying on this bit
// & neglecting to set it.)
aItem.Frame()->AddStateBits(NS_FRAME_CONTAINS_RELATIVE_BSIZE);
}
// NOTE: Be very careful about doing anything else with childReflowInput
// after this point, because some of its methods (e.g. SetComputedWidth)
// internally call InitResizeFlags and stomp on mVResize & mHResize.
FLEX_LOG("Reflowing flex item %p at its desired position %s", aItem.Frame(),
ToString(aFramePos).c_str());
// CachedFlexItemData is stored in item's writing mode, so we pass
// aChildReflowInput into ReflowOutput's constructor.
ReflowOutput childReflowOutput(childReflowInput);
nsReflowStatus childReflowStatus;
ReflowChild(aItem.Frame(), PresContext(), childReflowOutput, childReflowInput,
outerWM, aFramePos, aContainerSize, ReflowChildFlags::Default,
childReflowStatus);
// XXXdholbert Perhaps we should call CheckForInterrupt here; see bug 1495532.
FinishReflowChild(aItem.Frame(), PresContext(), childReflowOutput,
&childReflowInput, outerWM, aFramePos, aContainerSize,
ReflowChildFlags::ApplyRelativePositioning);
aItem.SetAscent(childReflowOutput.BlockStartAscent());
// Update our cached flex item info:
if (auto* cached = aItem.Frame()->GetProperty(CachedFlexItemData::Prop())) {
cached->Update(childReflowInput, childReflowOutput,
FlexItemReflowType::Final);
} else {
cached = new CachedFlexItemData(childReflowInput, childReflowOutput,
FlexItemReflowType::Final);
aItem.Frame()->SetProperty(CachedFlexItemData::Prop(), cached);
}
return childReflowStatus;
}
void nsFlexContainerFrame::ReflowPlaceholders(
const ReflowInput& aReflowInput, nsTArray<nsIFrame*>& aPlaceholders,
const LogicalPoint& aContentBoxOrigin, const nsSize& aContainerSize) {
WritingMode outerWM = aReflowInput.GetWritingMode();
// As noted in this method's documentation, we'll reflow every entry in
// |aPlaceholders| at the container's content-box origin.
for (nsIFrame* placeholder : aPlaceholders) {
MOZ_ASSERT(placeholder->IsPlaceholderFrame(),
"placeholders array should only contain placeholder frames");
WritingMode wm = placeholder->GetWritingMode();
LogicalSize availSize = aReflowInput.ComputedSize(wm);
ReflowInput childReflowInput(PresContext(), aReflowInput, placeholder,
availSize);
// No need to set the -webkit-line-clamp related flags when reflowing
// a placeholder.
ReflowOutput childReflowOutput(outerWM);
nsReflowStatus childReflowStatus;
ReflowChild(placeholder, PresContext(), childReflowOutput, childReflowInput,
outerWM, aContentBoxOrigin, aContainerSize,
ReflowChildFlags::Default, childReflowStatus);
FinishReflowChild(placeholder, PresContext(), childReflowOutput,
&childReflowInput, outerWM, aContentBoxOrigin,
aContainerSize, ReflowChildFlags::Default);
// Mark the placeholder frame to indicate that it's not actually at the
// element's static position, because we need to apply CSS Alignment after
// we determine the OOF's size:
placeholder->AddStateBits(PLACEHOLDER_STATICPOS_NEEDS_CSSALIGN);
}
}
nscoord nsFlexContainerFrame::IntrinsicISize(gfxContext* aRenderingContext,
IntrinsicISizeType aType) {
nscoord containerISize = 0;
const nsStylePosition* stylePos = StylePosition();
const FlexboxAxisTracker axisTracker(this);
nscoord mainGapSize;
if (axisTracker.IsRowOriented()) {
mainGapSize = nsLayoutUtils::ResolveGapToLength(stylePos->mColumnGap,
NS_UNCONSTRAINEDSIZE);
} else {
mainGapSize = nsLayoutUtils::ResolveGapToLength(stylePos->mRowGap,
NS_UNCONSTRAINEDSIZE);
}
const bool useMozBoxCollapseBehavior =
StyleVisibility()->UseLegacyCollapseBehavior();
// The loop below sets aside space for a gap before each item besides the
// first. This bool helps us handle that special-case.
bool onFirstChild = true;
for (nsIFrame* childFrame : mFrames) {
// Skip out-of-flow children because they don't participate in flex layout.
if (childFrame->IsPlaceholderFrame()) {
continue;
}
if (useMozBoxCollapseBehavior &&
childFrame->StyleVisibility()->IsCollapse()) {
// If we're using legacy "visibility:collapse" behavior, then we don't
// care about the sizes of any collapsed children.
continue;
}
nscoord childISize = nsLayoutUtils::IntrinsicForContainer(
aRenderingContext, childFrame, aType);
// * For a row-oriented single-line flex container, the intrinsic
// {min/pref}-isize is the sum of its items' {min/pref}-isizes and
// (n-1) column gaps.
// * For a column-oriented flex container, the intrinsic min isize
// is the max of its items' min isizes.
// * For a row-oriented multi-line flex container, the intrinsic
// pref isize is former (sum), and its min isize is the latter (max).
bool isSingleLine = (StyleFlexWrap::Nowrap == stylePos->mFlexWrap);
if (axisTracker.IsRowOriented() &&
(isSingleLine || aType == IntrinsicISizeType::PrefISize)) {
containerISize += childISize;
if (!onFirstChild) {
containerISize += mainGapSize;
}
onFirstChild = false;
} else { // (col-oriented, or MinISize for multi-line row flex container)
containerISize = std::max(containerISize, childISize);
}
}
return containerISize;
}
/* virtual */
nscoord nsFlexContainerFrame::GetMinISize(gfxContext* aRenderingContext) {
DISPLAY_MIN_INLINE_SIZE(this, mCachedMinISize);
if (mCachedMinISize == NS_INTRINSIC_ISIZE_UNKNOWN) {
if (Maybe<nscoord> containISize = ContainIntrinsicISize()) {
mCachedMinISize = *containISize;
} else {
mCachedMinISize =
IntrinsicISize(aRenderingContext, IntrinsicISizeType::MinISize);
}
}
return mCachedMinISize;
}
/* virtual */
nscoord nsFlexContainerFrame::GetPrefISize(gfxContext* aRenderingContext) {
DISPLAY_PREF_INLINE_SIZE(this, mCachedPrefISize);
if (mCachedPrefISize == NS_INTRINSIC_ISIZE_UNKNOWN) {
if (Maybe<nscoord> containISize = ContainIntrinsicISize()) {
mCachedPrefISize = *containISize;
} else {
mCachedPrefISize =
IntrinsicISize(aRenderingContext, IntrinsicISizeType::PrefISize);
}
}
return mCachedPrefISize;
}
int32_t nsFlexContainerFrame::GetNumLines() const {
// TODO(emilio, bug 1793251): Treating all row oriented frames as single-lines
// might not be great for flex-wrap'd containers, consider trying to do
// better? We probably would need to persist more stuff than we do after
// layout.
return FlexboxAxisInfo(this).mIsRowOriented ? 1 : mFrames.GetLength();
}
bool nsFlexContainerFrame::IsLineIteratorFlowRTL() {
FlexboxAxisInfo info(this);
if (info.mIsRowOriented) {
const bool isRtl = StyleVisibility()->mDirection == StyleDirection::Rtl;
return info.mIsMainAxisReversed != isRtl;
}
return false;
}
Result<nsILineIterator::LineInfo, nsresult> nsFlexContainerFrame::GetLine(
int32_t aLineNumber) {
if (aLineNumber < 0 || aLineNumber >= GetNumLines()) {
return Err(NS_ERROR_FAILURE);
}
FlexboxAxisInfo info(this);
LineInfo lineInfo;
if (info.mIsRowOriented) {
lineInfo.mLineBounds = GetRect();
lineInfo.mFirstFrameOnLine = mFrames.FirstChild();
// This isn't quite ideal for multi-line row flexbox, see bug 1793251.
lineInfo.mNumFramesOnLine = mFrames.GetLength();
} else {
// TODO(emilio, bug 1793322): Deal with column-reverse (mIsMainAxisReversed)
nsIFrame* f = mFrames.FrameAt(aLineNumber);
lineInfo.mLineBounds = f->GetRect();
lineInfo.mFirstFrameOnLine = f;
lineInfo.mNumFramesOnLine = 1;
}
return lineInfo;
}
int32_t nsFlexContainerFrame::FindLineContaining(nsIFrame* aFrame,
int32_t aStartLine) {
const int32_t index = mFrames.IndexOf(aFrame);
if (index < 0) {
return -1;
}
const FlexboxAxisInfo info(this);
if (info.mIsRowOriented) {
return 0;
}
if (index < aStartLine) {
return -1;
}
return index;
}
NS_IMETHODIMP
nsFlexContainerFrame::CheckLineOrder(int32_t aLine, bool* aIsReordered,
nsIFrame** aFirstVisual,
nsIFrame** aLastVisual) {
*aIsReordered = false;
*aFirstVisual = nullptr;
*aLastVisual = nullptr;
return NS_OK;
}
NS_IMETHODIMP
nsFlexContainerFrame::FindFrameAt(int32_t aLineNumber, nsPoint aPos,
nsIFrame** aFrameFound,
bool* aPosIsBeforeFirstFrame,
bool* aPosIsAfterLastFrame) {
const auto wm = GetWritingMode();
const LogicalPoint pos(wm, aPos, GetSize());
const FlexboxAxisInfo info(this);
*aFrameFound = nullptr;
*aPosIsBeforeFirstFrame = true;
*aPosIsAfterLastFrame = false;
if (!info.mIsRowOriented) {
nsIFrame* f = mFrames.FrameAt(aLineNumber);
if (!f) {
return NS_OK;
}
auto rect = f->GetLogicalRect(wm, GetSize());
*aFrameFound = f;
*aPosIsBeforeFirstFrame = pos.I(wm) < rect.IStart(wm);
*aPosIsAfterLastFrame = pos.I(wm) > rect.IEnd(wm);
return NS_OK;
}
LineFrameFinder finder(aPos, GetSize(), GetWritingMode(),
IsLineIteratorFlowRTL());
for (nsIFrame* f : mFrames) {
finder.Scan(f);
if (finder.IsDone()) {
break;
}
}
finder.Finish(aFrameFound, aPosIsBeforeFirstFrame, aPosIsAfterLastFrame);
return NS_OK;
}
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