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gecko/layout/generic/nsFlexContainerFrame.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=2 et sw=2 tw=80: */
/* This Source Code is subject to the terms of the Mozilla Public License
* version 2.0 (the "License"). You can obtain a copy of the License at
* http://mozilla.org/MPL/2.0/. */
/* rendering object for CSS "display: flex" */
#include "nsFlexContainerFrame.h"
#include "nsContentUtils.h"
#include "nsCSSAnonBoxes.h"
#include "nsDisplayList.h"
#include "nsLayoutUtils.h"
#include "nsPlaceholderFrame.h"
#include "nsPresContext.h"
#include "nsStyleContext.h"
#include "prlog.h"
#include <algorithm>
using namespace mozilla::css;
using namespace mozilla::layout;
#ifdef PR_LOGGING
static PRLogModuleInfo*
GetFlexContainerLog()
{
static PRLogModuleInfo *sLog;
if (!sLog)
sLog = PR_NewLogModule("nsFlexContainerFrame");
return sLog;
}
#endif /* PR_LOGGING */
// XXXdholbert Some of this helper-stuff should be separated out into a general
// "LogicalAxisUtils.h" helper. Should that be a class, or a namespace (under
// what super-namespace?), or what?
// Helper enums
// ============
// Represents a physical orientation for an axis.
// The directional suffix indicates the direction in which the axis *grows*.
// So e.g. eAxis_LR means a horizontal left-to-right axis, whereas eAxis_BT
// means a vertical bottom-to-top axis.
// NOTE: The order here is important -- these values are used as indices into
// the static array 'kAxisOrientationToSidesMap', defined below.
enum AxisOrientationType {
eAxis_LR,
eAxis_RL,
eAxis_TB,
eAxis_BT,
eNumAxisOrientationTypes // For sizing arrays that use these values as indices
};
// Represents one or the other extreme of an axis (e.g. for the main axis, the
// main-start vs. main-end edge.
// NOTE: The order here is important -- these values are used as indices into
// the sub-arrays in 'kAxisOrientationToSidesMap', defined below.
enum AxisEdgeType {
eAxisEdge_Start,
eAxisEdge_End,
eNumAxisEdges // For sizing arrays that use these values as indices
};
// This array maps each axis orientation to a pair of corresponding
// [start, end] physical mozilla::css::Side values.
static const Side
kAxisOrientationToSidesMap[eNumAxisOrientationTypes][eNumAxisEdges] = {
{ eSideLeft, eSideRight }, // eAxis_LR
{ eSideRight, eSideLeft }, // eAxis_RL
{ eSideTop, eSideBottom }, // eAxis_TB
{ eSideBottom, eSideTop } // eAxis_BT
};
// Helper structs / classes / methods
// ==================================
// Indicates whether advancing along the given axis is equivalent to
// increasing our X or Y position (as opposed to decreasing it).
static inline bool
AxisGrowsInPositiveDirection(AxisOrientationType aAxis)
{
return eAxis_LR == aAxis || eAxis_TB == aAxis;
}
// Indicates whether the given axis is horizontal.
static inline bool
IsAxisHorizontal(AxisOrientationType aAxis)
{
return eAxis_LR == aAxis || eAxis_RL == aAxis;
}
// Given an AxisOrientationType, returns the "reverse" AxisOrientationType
// (in the same dimension, but the opposite direction)
static inline AxisOrientationType
GetReverseAxis(AxisOrientationType aAxis)
{
AxisOrientationType reversedAxis;
if (aAxis % 2 == 0) {
// even enum value. Add 1 to reverse.
reversedAxis = AxisOrientationType(aAxis + 1);
} else {
// odd enum value. Subtract 1 to reverse.
reversedAxis = AxisOrientationType(aAxis - 1);
}
// Check that we're still in the enum's valid range
MOZ_ASSERT(reversedAxis >= eAxis_LR &&
reversedAxis <= eAxis_BT);
return reversedAxis;
}
// Returns aFrame's computed value for 'height' or 'width' -- whichever is in
// the same dimension as aAxis.
static inline const nsStyleCoord&
GetSizePropertyForAxis(const nsIFrame* aFrame, AxisOrientationType aAxis)
{
const nsStylePosition* stylePos = aFrame->StylePosition();
return IsAxisHorizontal(aAxis) ?
stylePos->mWidth :
stylePos->mHeight;
}
static nscoord
MarginComponentForSide(const nsMargin& aMargin, Side aSide)
{
switch (aSide) {
case eSideLeft:
return aMargin.left;
case eSideRight:
return aMargin.right;
case eSideTop:
return aMargin.top;
case eSideBottom:
return aMargin.bottom;
}
NS_NOTREACHED("unexpected Side enum");
return aMargin.left; // have to return something
// (but something's busted if we got here)
}
static nscoord&
MarginComponentForSide(nsMargin& aMargin, Side aSide)
{
switch (aSide) {
case eSideLeft:
return aMargin.left;
case eSideRight:
return aMargin.right;
case eSideTop:
return aMargin.top;
case eSideBottom:
return aMargin.bottom;
}
NS_NOTREACHED("unexpected Side enum");
return aMargin.left; // have to return something
// (but something's busted if we got here)
}
// Helper-macro to let us pick one of two expressions to evaluate
// (a width expression vs. a height expression), to get a main-axis or
// cross-axis component.
// For code that has e.g. a nsSize object, FlexboxAxisTracker::GetMainComponent
// and GetCrossComponent are cleaner; but in cases where we simply have
// two separate expressions for width and height (which may be expensive to
// evaluate), these macros will ensure that only the expression for the correct
// axis gets evaluated.
#define GET_MAIN_COMPONENT(axisTracker_, width_, height_) \
IsAxisHorizontal((axisTracker_).GetMainAxis()) ? (width_) : (height_)
#define GET_CROSS_COMPONENT(axisTracker_, width_, height_) \
IsAxisHorizontal((axisTracker_).GetCrossAxis()) ? (width_) : (height_)
// Encapsulates our flex container's main & cross axes.
class MOZ_STACK_CLASS FlexboxAxisTracker {
public:
FlexboxAxisTracker(nsFlexContainerFrame* aFlexContainerFrame);
// Accessors:
AxisOrientationType GetMainAxis() const { return mMainAxis; }
AxisOrientationType GetCrossAxis() const { return mCrossAxis; }
nscoord GetMainComponent(const nsSize& aSize) const {
return GET_MAIN_COMPONENT(*this, aSize.width, aSize.height);
}
int32_t GetMainComponent(const nsIntSize& aIntSize) const {
return GET_MAIN_COMPONENT(*this, aIntSize.width, aIntSize.height);
}
nscoord GetCrossComponent(const nsSize& aSize) const {
return GET_CROSS_COMPONENT(*this, aSize.width, aSize.height);
}
int32_t GetCrossComponent(const nsIntSize& aIntSize) const {
return GET_CROSS_COMPONENT(*this, aIntSize.width, aIntSize.height);
}
nscoord GetMarginSizeInMainAxis(const nsMargin& aMargin) const {
return IsAxisHorizontal(mMainAxis) ?
aMargin.LeftRight() :
aMargin.TopBottom();
}
nscoord GetMarginSizeInCrossAxis(const nsMargin& aMargin) const {
return IsAxisHorizontal(mCrossAxis) ?
aMargin.LeftRight() :
aMargin.TopBottom();
}
/**
* Converts a logical position into a "physical" x,y position.
*
* In the simplest case where the main-axis is left-to-right and the
* cross-axis is top-to-bottom, this just returns
* nsPoint(aMainPosn, aCrossPosn).
*
* @arg aMainPosn The main-axis position -- i.e an offset from the
* main-start edge of the container's content box.
* @arg aCrossPosn The cross-axis position -- i.e an offset from the
* cross-start edge of the container's content box.
* @return A nsPoint representing the same position (in coordinates
* relative to the container's content box).
*/
nsPoint PhysicalPositionFromLogicalPosition(nscoord aMainPosn,
nscoord aCrossPosn,
nscoord aContainerMainSize,
nscoord aContainerCrossSize) const {
// If either of our logical axes are backwards with respect to our x,y
// coordinate system (e.g. right-to-left or bottom-to-top), then subtract
// that axis's logical coord them from the container size in that dimension,
// to flip the polarity around.
if (!AxisGrowsInPositiveDirection(mMainAxis)) {
aMainPosn = aContainerMainSize - aMainPosn;
}
if (!AxisGrowsInPositiveDirection(mCrossAxis)) {
aCrossPosn = aContainerCrossSize - aCrossPosn;
}
return IsAxisHorizontal(mMainAxis) ?
nsPoint(aMainPosn, aCrossPosn) :
nsPoint(aCrossPosn, aMainPosn);
}
nsSize PhysicalSizeFromLogicalSizes(nscoord aMainSize,
nscoord aCrossSize) const {
return IsAxisHorizontal(mMainAxis) ?
nsSize(aMainSize, aCrossSize) :
nsSize(aCrossSize, aMainSize);
}
private:
AxisOrientationType mMainAxis;
AxisOrientationType mCrossAxis;
};
// Represents a flex item.
// Includes the various pieces of input that the Flexbox Layout Algorithm uses
// to resolve a flexible width.
class FlexItem {
public:
FlexItem(nsIFrame* aChildFrame,
float aFlexGrow, float aFlexShrink, nscoord aMainBaseSize,
nscoord aMainMinSize, nscoord aMainMaxSize,
nscoord aCrossMinSize, nscoord aCrossMaxSize,
nsMargin aMargin, nsMargin aBorderPadding,
const FlexboxAxisTracker& aAxisTracker);
// Accessors
nsIFrame* Frame() const { return mFrame; }
nscoord GetFlexBaseSize() const { return mFlexBaseSize; }
nscoord GetMainMinSize() const { return mMainMinSize; }
nscoord GetMainMaxSize() const { return mMainMaxSize; }
// Note: These return the main-axis position and size of our *content box*.
nscoord GetMainSize() const { return mMainSize; }
nscoord GetMainPosition() const { return mMainPosn; }
nscoord GetCrossMinSize() const { return mCrossMinSize; }
nscoord GetCrossMaxSize() const { return mCrossMaxSize; }
// Note: These return the cross-axis position and size of our *content box*.
nscoord GetCrossSize() const { return mCrossSize; }
nscoord GetCrossPosition() const { return mCrossPosn; }
nscoord GetAscent() const { return mAscent; }
float GetShareOfFlexWeightSoFar() const { return mShareOfFlexWeightSoFar; }
bool IsFrozen() const { return mIsFrozen; }
bool HadMinViolation() const { return mHadMinViolation; }
bool HadMaxViolation() const { 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 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; }
uint8_t GetAlignSelf() const { return mAlignSelf; }
// Returns the flex weight that we should use in the "resolving flexible
// lengths" algorithm. If we've got a positive amount of free space, we use
// the flex-grow weight; otherwise, we use the "scaled flex shrink weight"
// (scaled by our flex base size)
float GetFlexWeightToUse(bool aHavePositiveFreeSpace)
{
if (IsFrozen()) {
return 0.0f;
}
return aHavePositiveFreeSpace ?
mFlexGrow :
mFlexShrink * mFlexBaseSize;
}
// Getters for margin:
// ===================
const nsMargin& GetMargin() const { return mMargin; }
// Returns the margin component for a given mozilla::css::Side
nscoord GetMarginComponentForSide(Side aSide) const
{ return MarginComponentForSide(mMargin, aSide); }
// Returns the total space occupied by this item's margins in the given axis
nscoord GetMarginSizeInAxis(AxisOrientationType aAxis) const
{
Side startSide = kAxisOrientationToSidesMap[aAxis][eAxisEdge_Start];
Side endSide = kAxisOrientationToSidesMap[aAxis][eAxisEdge_End];
return GetMarginComponentForSide(startSide) +
GetMarginComponentForSide(endSide);
}
// Getters for border/padding
// ==========================
const nsMargin& GetBorderPadding() const { return mBorderPadding; }
// Returns the border+padding component for a given mozilla::css::Side
nscoord GetBorderPaddingComponentForSide(Side aSide) const
{ return MarginComponentForSide(mBorderPadding, aSide); }
// Returns the total space occupied by this item's borders and padding in
// the given axis
nscoord GetBorderPaddingSizeInAxis(AxisOrientationType aAxis) const
{
Side startSide = kAxisOrientationToSidesMap[aAxis][eAxisEdge_Start];
Side endSide = kAxisOrientationToSidesMap[aAxis][eAxisEdge_End];
return GetBorderPaddingComponentForSide(startSide) +
GetBorderPaddingComponentForSide(endSide);
}
// Getter for combined margin/border/padding
// =========================================
// Returns the total space occupied by this item's margins, borders and
// padding in the given axis
nscoord GetMarginBorderPaddingSizeInAxis(AxisOrientationType aAxis) const
{
return GetMarginSizeInAxis(aAxis) + GetBorderPaddingSizeInAxis(aAxis);
}
// Setters
// =======
// This sets our flex base size, and then updates the main size to the
// base size clamped to our main-axis [min,max] constraints.
void SetFlexBaseSizeAndMainSize(nscoord aNewFlexBaseSize)
{
MOZ_ASSERT(!mIsFrozen || mFlexBaseSize == NS_INTRINSICSIZE,
"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);
}
// 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 SetShareOfFlexWeightSoFar(float aNewShare)
{
MOZ_ASSERT(!mIsFrozen || aNewShare == 0.0f,
"shouldn't be giving this item any share of the weight "
"after it's frozen");
mShareOfFlexWeightSoFar = aNewShare;
}
void Freeze() { mIsFrozen = true; }
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()
{ mHadMinViolation = mHadMaxViolation = false; }
// 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;
}
void SetAscent(nscoord aAscent) {
mAscent = aAscent;
}
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(Side aSide, nscoord aLength)
{
MOZ_ASSERT(mIsFrozen, "main size should be resolved before this");
MarginComponentForSide(mMargin, aSide) = aLength;
}
void ResolveStretchedCrossSize(nscoord aLineCrossSize,
const FlexboxAxisTracker& aAxisTracker);
uint32_t GetNumAutoMarginsInAxis(AxisOrientationType aAxis) const;
protected:
// Our frame:
nsIFrame* const mFrame;
// Values that we already know in constructor: (and are hence mostly 'const')
const float mFlexGrow;
const float mFlexShrink;
const nsMargin mBorderPadding;
nsMargin mMargin; // non-const because we need to resolve auto margins
nscoord mFlexBaseSize;
const nscoord mMainMinSize;
const nscoord mMainMaxSize;
const nscoord mCrossMinSize;
const nscoord mCrossMaxSize;
// Values that we compute after constructor:
nscoord mMainSize;
nscoord mMainPosn;
nscoord mCrossSize;
nscoord mCrossPosn;
nscoord mAscent;
// 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.
float mShareOfFlexWeightSoFar;
bool mIsFrozen;
bool mHadMinViolation;
bool mHadMaxViolation;
// Misc:
bool mHadMeasuringReflow; // Did this item get a preliminary reflow,
// to measure its desired height?
bool mIsStretched; // See IsStretched() documentation
uint8_t mAlignSelf; // My "align-self" computed value (with "auto"
// swapped out for parent"s "align-items" value,
// in our constructor).
};
// Helper-function to find the first non-anonymous-box descendent of aFrame.
static nsIFrame*
GetFirstNonAnonBoxDescendant(nsIFrame* aFrame)
{
while (aFrame) {
nsIAtom* pseudoTag = aFrame->StyleContext()->GetPseudo();
// If aFrame isn't an anonymous container, then it'll do.
if (!pseudoTag || // No pseudotag.
!nsCSSAnonBoxes::IsAnonBox(pseudoTag) || // Pseudotag isn't anon.
pseudoTag == nsCSSAnonBoxes::mozNonElement) { // Text, not a container.
break;
}
// Otherwise, descend to its first child and repeat.
// SPECIAL CASE: if we're dealing with an anonymous table, then it might
// be wrapping something non-anonymous in its caption or col-group lists
// (instead of its principal child list), so we have to look there.
// (Note: For anonymous tables that have a non-anon cell *and* a non-anon
// column, we'll always return the column. This is fine; we're really just
// looking for a handle to *anything* with a meaningful content node inside
// the table, for use in DOM comparisons to things outside of the table.)
if (MOZ_UNLIKELY(aFrame->GetType() == nsGkAtoms::tableOuterFrame)) {
nsIFrame* captionDescendant =
GetFirstNonAnonBoxDescendant(aFrame->GetFirstChild(kCaptionList));
if (captionDescendant) {
return captionDescendant;
}
} else if (MOZ_UNLIKELY(aFrame->GetType() == nsGkAtoms::tableFrame)) {
nsIFrame* colgroupDescendant =
GetFirstNonAnonBoxDescendant(aFrame->GetFirstChild(kColGroupList));
if (colgroupDescendant) {
return colgroupDescendant;
}
}
// USUAL CASE: Descend to the first child in principal list.
aFrame = aFrame->GetFirstPrincipalChild();
}
return aFrame;
}
/**
* Sorting helper-function that compares two frames' "order" property-values,
* and if they're equal, compares the DOM positions of their corresponding
* content nodes. Returns true if aFrame1 is "less than or equal to" aFrame2
* according to this comparison.
*
* Note: This can't be a static function, because we need to pass it as a
* template argument. (Only functions with external linkage can be passed as
* template arguments.)
*
* @return true if the computed "order" property of aFrame1 is less than that
* of aFrame2, or if the computed "order" values are equal and aFrame1's
* corresponding DOM node is earlier than aFrame2's in the DOM tree.
* Otherwise, returns false.
*/
bool
IsOrderLEQWithDOMFallback(nsIFrame* aFrame1,
nsIFrame* aFrame2)
{
MOZ_ASSERT(aFrame1->IsFlexItem() && aFrame2->IsFlexItem(),
"this method only intended for comparing flex items");
if (aFrame1 == aFrame2) {
// Anything is trivially LEQ itself, so we return "true" here... but it's
// probably bad if we end up actually needing this, so let's assert.
NS_ERROR("Why are we checking if a frame is LEQ itself?");
return true;
}
// If we've got a placeholder frame, use its out-of-flow frame's 'order' val.
{
nsIFrame* aRealFrame1 = nsPlaceholderFrame::GetRealFrameFor(aFrame1);
nsIFrame* aRealFrame2 = nsPlaceholderFrame::GetRealFrameFor(aFrame2);
int32_t order1 = aRealFrame1->StylePosition()->mOrder;
int32_t order2 = aRealFrame2->StylePosition()->mOrder;
if (order1 != order2) {
return order1 < order2;
}
}
// The "order" values are equal, so we need to fall back on DOM comparison.
// For that, we need to dig through any anonymous box wrapper frames to find
// the actual frame that corresponds to our child content.
aFrame1 = GetFirstNonAnonBoxDescendant(aFrame1);
aFrame2 = GetFirstNonAnonBoxDescendant(aFrame2);
MOZ_ASSERT(aFrame1 && aFrame2,
"why do we have an anonymous box without any "
"non-anonymous descendants?");
// Special case:
// If either frame is for generated content from ::before or ::after, then
// we can't use nsContentUtils::PositionIsBefore(), since that method won't
// recognize generated content as being an actual sibling of other nodes.
// We know where ::before and ::after nodes *effectively* insert in the DOM
// tree, though (at the beginning & end), so we can just special-case them.
nsIAtom* pseudo1 = aFrame1->StyleContext()->GetPseudo();
nsIAtom* pseudo2 = aFrame2->StyleContext()->GetPseudo();
if (pseudo1 == nsCSSPseudoElements::before ||
pseudo2 == nsCSSPseudoElements::after) {
// frame1 is ::before and/or frame2 is ::after => frame1 is LEQ frame2.
return true;
}
if (pseudo1 == nsCSSPseudoElements::after ||
pseudo2 == nsCSSPseudoElements::before) {
// frame1 is ::after and/or frame2 is ::before => frame1 is not LEQ frame2.
return false;
}
// Usual case: Compare DOM position.
nsIContent* content1 = aFrame1->GetContent();
nsIContent* content2 = aFrame2->GetContent();
MOZ_ASSERT(content1 != content2,
"Two different flex items are using the same nsIContent node for "
"comparison, so we may be sorting them in an arbitrary order");
return nsContentUtils::PositionIsBefore(content1, content2);
}
/**
* Sorting helper-function that compares two frames' "order" property-values.
* Returns true if aFrame1 is "less than or equal to" aFrame2 according to this
* comparison.
*
* Note: This can't be a static function, because we need to pass it as a
* template argument. (Only functions with external linkage can be passed as
* template arguments.)
*
* @return true if the computed "order" property of aFrame1 is less than or
* equal to that of aFrame2. Otherwise, returns false.
*/
bool
IsOrderLEQ(nsIFrame* aFrame1,
nsIFrame* aFrame2)
{
MOZ_ASSERT(aFrame1->IsFlexItem() && aFrame2->IsFlexItem(),
"this method only intended for comparing flex items");
// If we've got a placeholder frame, use its out-of-flow frame's 'order' val.
nsIFrame* aRealFrame1 = nsPlaceholderFrame::GetRealFrameFor(aFrame1);
nsIFrame* aRealFrame2 = nsPlaceholderFrame::GetRealFrameFor(aFrame2);
int32_t order1 = aRealFrame1->StylePosition()->mOrder;
int32_t order2 = aRealFrame2->StylePosition()->mOrder;
return order1 <= order2;
}
bool
nsFlexContainerFrame::IsHorizontal()
{
const FlexboxAxisTracker axisTracker(this);
return IsAxisHorizontal(axisTracker.GetMainAxis());
}
FlexItem
nsFlexContainerFrame::GenerateFlexItemForChild(
nsPresContext* aPresContext,
nsIFrame* aChildFrame,
const nsHTMLReflowState& aParentReflowState,
const FlexboxAxisTracker& aAxisTracker)
{
// Create temporary reflow state just for sizing -- to get hypothetical
// main-size and the computed values of min / max main-size property.
// (This reflow state will _not_ be used for reflow.)
nsHTMLReflowState childRS(aPresContext, aParentReflowState, aChildFrame,
nsSize(aParentReflowState.ComputedWidth(),
aParentReflowState.ComputedHeight()));
// FLEX GROW & SHRINK WEIGHTS
// --------------------------
const nsStylePosition* stylePos = aChildFrame->StylePosition();
float flexGrow = stylePos->mFlexGrow;
float flexShrink = stylePos->mFlexShrink;
// MAIN SIZES (flex base size, min/max size)
// -----------------------------------------
nscoord flexBaseSize = GET_MAIN_COMPONENT(aAxisTracker,
childRS.ComputedWidth(),
childRS.ComputedHeight());
nscoord mainMinSize = GET_MAIN_COMPONENT(aAxisTracker,
childRS.mComputedMinWidth,
childRS.mComputedMinHeight);
nscoord mainMaxSize = GET_MAIN_COMPONENT(aAxisTracker,
childRS.mComputedMaxWidth,
childRS.mComputedMaxHeight);
// This is enforced by the nsHTMLReflowState where these values come from:
MOZ_ASSERT(mainMinSize <= mainMaxSize, "min size is larger than max size");
// CROSS MIN/MAX SIZE
// ------------------
nscoord crossMinSize = GET_CROSS_COMPONENT(aAxisTracker,
childRS.mComputedMinWidth,
childRS.mComputedMinHeight);
nscoord crossMaxSize = GET_CROSS_COMPONENT(aAxisTracker,
childRS.mComputedMaxWidth,
childRS.mComputedMaxHeight);
// SPECIAL-CASE FOR WIDGET-IMPOSED SIZES
// Check if we're a themed widget, in which case we might have a minimum
// main & cross size imposed by our widget (which we can't go below), or
// (more severe) our widget might have only a single valid size.
bool isFixedSizeWidget = false;
const nsStyleDisplay* disp = aChildFrame->StyleDisplay();
if (aChildFrame->IsThemed(disp)) {
nsIntSize widgetMinSize(0, 0);
bool canOverride = true;
aPresContext->GetTheme()->
GetMinimumWidgetSize(childRS.rendContext, aChildFrame,
disp->mAppearance,
&widgetMinSize, &canOverride);
nscoord widgetMainMinSize =
aPresContext->DevPixelsToAppUnits(
aAxisTracker.GetMainComponent(widgetMinSize));
nscoord widgetCrossMinSize =
aPresContext->DevPixelsToAppUnits(
aAxisTracker.GetCrossComponent(widgetMinSize));
// GMWS() returns border-box; we need content-box
widgetMainMinSize -=
aAxisTracker.GetMarginSizeInMainAxis(childRS.mComputedBorderPadding);
widgetCrossMinSize -=
aAxisTracker.GetMarginSizeInCrossAxis(childRS.mComputedBorderPadding);
if (!canOverride) {
// Fixed-size widget: freeze our main-size at the widget's mandated size.
// (Set min and max main-sizes to that size, too, to keep us from
// clamping to any other size later on.)
flexBaseSize = mainMinSize = mainMaxSize = widgetMainMinSize;
crossMinSize = crossMaxSize = widgetCrossMinSize;
isFixedSizeWidget = true;
} else {
// Variable-size widget: ensure our min/max sizes are at least as large
// as the widget's mandated minimum size, so we don't flex below that.
mainMinSize = std::max(mainMinSize, widgetMainMinSize);
mainMaxSize = std::max(mainMaxSize, widgetMainMinSize);
crossMinSize = std::max(crossMinSize, widgetCrossMinSize);
crossMaxSize = std::max(crossMaxSize, widgetCrossMinSize);
}
}
// Construct the flex item!
FlexItem item(aChildFrame,
flexGrow, flexShrink, flexBaseSize,
mainMinSize, mainMaxSize,
crossMinSize, crossMaxSize,
childRS.mComputedMargin,
childRS.mComputedBorderPadding,
aAxisTracker);
// If we're inflexible, we can just freeze to our hypothetical main-size
// up-front. Similarly, if we're a fixed-size widget, we only have one
// valid size, so we freeze to keep ourselves from flexing.
if (isFixedSizeWidget || (flexGrow == 0.0f && flexShrink == 0.0f)) {
item.Freeze();
}
return item;
}
nsresult
nsFlexContainerFrame::
ResolveFlexItemMaxContentSizing(nsPresContext* aPresContext,
FlexItem& aFlexItem,
const nsHTMLReflowState& aParentReflowState,
const FlexboxAxisTracker& aAxisTracker)
{
if (IsAxisHorizontal(aAxisTracker.GetMainAxis())) {
// Nothing to do -- this function is only for measuring flex items
// in a vertical flex container.
return NS_OK;
}
if (NS_AUTOHEIGHT != aFlexItem.GetFlexBaseSize()) {
// Nothing to do; this function's only relevant for flex items
// with a base size of "auto" (or equivalent).
// XXXdholbert If & when we handle "min-height: min-content" for flex items,
// we'll want to resolve that in this function, too.
return NS_OK;
}
// If we get here, we're vertical and our main size ended up being
// unconstrained. We need to use our "max-content" height, which is what we
// get from reflowing into our available width.
// Note: This has to come *after* we construct the FlexItem, since we
// invoke at least one convenience method (ResolveStretchedCrossSize) which
// requires a FlexItem.
// Give the item a special reflow with "mIsFlexContainerMeasuringHeight"
// set. This tells it to behave as if it had "height: auto", regardless
// of what the "height" property is actually set to.
nsHTMLReflowState
childRSForMeasuringHeight(aPresContext, aParentReflowState,
aFlexItem.Frame(),
nsSize(aParentReflowState.ComputedWidth(),
NS_UNCONSTRAINEDSIZE),
-1, -1, nsHTMLReflowState::CALLER_WILL_INIT);
childRSForMeasuringHeight.mFlags.mIsFlexContainerMeasuringHeight = true;
childRSForMeasuringHeight.Init(aPresContext);
aFlexItem.ResolveStretchedCrossSize(aParentReflowState.ComputedWidth(),
aAxisTracker);
if (aFlexItem.IsStretched()) {
childRSForMeasuringHeight.SetComputedWidth(aFlexItem.GetCrossSize());
childRSForMeasuringHeight.mFlags.mHResize = true;
}
// If this item is flexible (vertically), then we assume that the
// computed-height 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
// vertical resize, even though none of its ancestors are necessarily
// being vertically resized.
// (Note: We don't have to do this for width, because InitResizeFlags
// will always turn on mHResize on when it sees that the computed width
// is different from current width, and that's all we need.)
if (!aFlexItem.IsFrozen()) { // Are we flexible?
childRSForMeasuringHeight.mFlags.mVResize = true;
}
nsHTMLReflowMetrics childDesiredSize;
nsReflowStatus childReflowStatus;
nsresult rv = ReflowChild(aFlexItem.Frame(), aPresContext,
childDesiredSize, childRSForMeasuringHeight,
0, 0, NS_FRAME_NO_MOVE_FRAME,
childReflowStatus);
NS_ENSURE_SUCCESS(rv, rv);
MOZ_ASSERT(NS_FRAME_IS_COMPLETE(childReflowStatus),
"We gave flex item unconstrained available height, so it "
"should be complete");
rv = FinishReflowChild(aFlexItem.Frame(), aPresContext,
&childRSForMeasuringHeight, childDesiredSize,
0, 0, 0);
NS_ENSURE_SUCCESS(rv, rv);
// Subtract border/padding in vertical axis, to get _just_
// the effective computed value of the "height" property.
nscoord childDesiredHeight = childDesiredSize.height -
childRSForMeasuringHeight.mComputedBorderPadding.TopBottom();
childDesiredHeight = std::max(0, childDesiredHeight);
aFlexItem.SetFlexBaseSizeAndMainSize(childDesiredHeight);
aFlexItem.SetHadMeasuringReflow();
return NS_OK;
}
FlexItem::FlexItem(nsIFrame* aChildFrame,
float aFlexGrow, float aFlexShrink, nscoord aFlexBaseSize,
nscoord aMainMinSize, nscoord aMainMaxSize,
nscoord aCrossMinSize, nscoord aCrossMaxSize,
nsMargin aMargin, nsMargin aBorderPadding,
const FlexboxAxisTracker& aAxisTracker)
: mFrame(aChildFrame),
mFlexGrow(aFlexGrow),
mFlexShrink(aFlexShrink),
mBorderPadding(aBorderPadding),
mMargin(aMargin),
mMainMinSize(aMainMinSize),
mMainMaxSize(aMainMaxSize),
mCrossMinSize(aCrossMinSize),
mCrossMaxSize(aCrossMaxSize),
mMainPosn(0),
mCrossSize(0),
mCrossPosn(0),
mAscent(0),
mShareOfFlexWeightSoFar(0.0f),
mIsFrozen(false),
mHadMinViolation(false),
mHadMaxViolation(false),
mHadMeasuringReflow(false),
mIsStretched(false),
mAlignSelf(aChildFrame->StylePosition()->mAlignSelf)
{
MOZ_ASSERT(aChildFrame, "expecting a non-null child frame");
SetFlexBaseSizeAndMainSize(aFlexBaseSize);
// 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
{
const nsStyleSides& styleMargin = mFrame->StyleMargin()->mMargin;
NS_FOR_CSS_SIDES(side) {
if (styleMargin.GetUnit(side) == eStyleUnit_Auto) {
MOZ_ASSERT(GetMarginComponentForSide(side) == 0,
"Someone else tried to resolve our auto margin");
}
}
}
#endif // DEBUG
// Resolve "align-self: auto" to parent's "align-items" value.
if (mAlignSelf == NS_STYLE_ALIGN_SELF_AUTO) {
mAlignSelf =
mFrame->StyleContext()->GetParent()->StylePosition()->mAlignItems;
}
// If the flex item's inline axis is the same as the cross axis, then
// 'align-self:baseline' is identical to 'flex-start'. 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.
// Moreover: for the time being (until we support writing-modes),
// all inline axes are horizontal -- so we can just check if the cross axis
// is horizontal.
// FIXME: Once we support writing-mode (vertical text), this IsAxisHorizontal
// check won't be sufficient anymore -- we'll actually need to compare our
// inline axis vs. the cross axis.
if (mAlignSelf == NS_STYLE_ALIGN_ITEMS_BASELINE &&
IsAxisHorizontal(aAxisTracker.GetCrossAxis())) {
mAlignSelf = NS_STYLE_ALIGN_ITEMS_FLEX_START;
}
}
uint32_t
FlexItem::GetNumAutoMarginsInAxis(AxisOrientationType aAxis) const
{
uint32_t numAutoMargins = 0;
const nsStyleSides& styleMargin = mFrame->StyleMargin()->mMargin;
for (uint32_t i = 0; i < eNumAxisEdges; i++) {
Side side = kAxisOrientationToSidesMap[aAxis][i];
if (styleMargin.GetUnit(side) == eStyleUnit_Auto) {
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;
}
// 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 GetPosition() const { return mPosition; }
inline AxisOrientationType GetAxis() const { return mAxis; }
// Advances our position across the start edge of the given margin, in the
// axis we're tracking.
void EnterMargin(const nsMargin& aMargin)
{
Side side = kAxisOrientationToSidesMap[mAxis][eAxisEdge_Start];
mPosition += MarginComponentForSide(aMargin, side);
}
// Advances our position across the end edge of the given margin, in the axis
// we're tracking.
void ExitMargin(const nsMargin& aMargin)
{
Side side = kAxisOrientationToSidesMap[mAxis][eAxisEdge_End];
mPosition += MarginComponentForSide(aMargin, side);
}
// 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 positive direction.)
void EnterChildFrame(nscoord aChildFrameSize)
{
if (!AxisGrowsInPositiveDirection(mAxis))
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
// grows in the negative direction.)
void ExitChildFrame(nscoord aChildFrameSize)
{
if (AxisGrowsInPositiveDirection(mAxis))
mPosition += aChildFrameSize;
}
protected:
// Protected constructor, to be sure we're only instantiated via a subclass.
PositionTracker(AxisOrientationType aAxis)
: mPosition(0),
mAxis(aAxis)
{}
private:
// Private copy-constructor, since we don't want any instances of our
// subclasses to be accidentally copied.
PositionTracker(const PositionTracker& aOther)
: mPosition(aOther.mPosition),
mAxis(aOther.mAxis)
{}
protected:
// Member data:
nscoord mPosition; // The position we're tracking
const AxisOrientationType mAxis; // The axis along which we're moving
};
// 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(nsFlexContainerFrame* aFlexContainerFrame,
const FlexboxAxisTracker& aAxisTracker,
const nsHTMLReflowState& aReflowState,
const nsTArray<FlexItem>& aItems,
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 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;
uint32_t mNumAutoMarginsInMainAxis;
uint32_t mNumPackingSpacesRemaining;
uint8_t mJustifyContent;
};
// 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(nsFlexContainerFrame* aFlexContainerFrame,
const FlexboxAxisTracker& aAxisTracker,
const nsHTMLReflowState& aReflowState)
: PositionTracker(aAxisTracker.GetCrossAxis()) {}
// XXXdholbert This probably needs a ResolveStretchedLines() method,
// (which takes an array of SingleLineCrossAxisPositionTracker objects
// and distributes an equal amount of space to each one).
// For now, we just have Reflow directly call
// SingleLineCrossAxisPositionTracker::SetLineCrossSize().
};
// Utility class for managing our position along the cross axis, *within* a
// single flex line.
class MOZ_STACK_CLASS SingleLineCrossAxisPositionTracker : public PositionTracker {
public:
SingleLineCrossAxisPositionTracker(nsFlexContainerFrame* aFlexContainerFrame,
const FlexboxAxisTracker& aAxisTracker,
const nsTArray<FlexItem>& aItems);
void ComputeLineCrossSize(const nsTArray<FlexItem>& aItems);
inline nscoord GetLineCrossSize() const { return mLineCrossSize; }
// Used to override the flex line's size, for cases when the flex container is
// single-line and has a fixed size, and also in cases where
// "align-self: stretch" triggers some space-distribution between lines
// (when we support that property).
inline void SetLineCrossSize(nscoord aNewLineCrossSize) {
mLineCrossSize = aNewLineCrossSize;
}
void ResolveAutoMarginsInCrossAxis(FlexItem& aItem);
void EnterAlignPackingSpace(const FlexItem& aItem);
// Resets our position to the cross-start edge of this line.
inline void ResetPosition() { mPosition = 0; }
// Returns the ascent of the line.
nscoord GetCrossStartToFurthestBaseline() { return mCrossStartToFurthestBaseline; }
private:
// Returns the distance from the cross-start side of the given flex item's
// margin-box to its baseline. (Used in baseline alignment.)
nscoord GetBaselineOffsetFromCrossStart(const FlexItem& aItem) const;
nscoord mLineCrossSize;
// Largest distance from a baseline-aligned item's cross-start margin-box
// edge to its baseline. Computed in ComputeLineCrossSize, and used for
// alignment of any "align-self: baseline" items in this line (and possibly
// used for computing the baseline of the flex container, as well).
nscoord mCrossStartToFurthestBaseline;
};
//----------------------------------------------------------------------
// Frame class boilerplate
// =======================
NS_QUERYFRAME_HEAD(nsFlexContainerFrame)
NS_QUERYFRAME_ENTRY(nsFlexContainerFrame)
NS_QUERYFRAME_TAIL_INHERITING(nsFlexContainerFrameSuper)
NS_IMPL_FRAMEARENA_HELPERS(nsFlexContainerFrame)
nsIFrame*
NS_NewFlexContainerFrame(nsIPresShell* aPresShell,
nsStyleContext* aContext)
{
return new (aPresShell) nsFlexContainerFrame(aContext);
}
//----------------------------------------------------------------------
// nsFlexContainerFrame Method Implementations
// ===========================================
/* virtual */
nsFlexContainerFrame::~nsFlexContainerFrame()
{
}
template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
/* static */ bool
nsFlexContainerFrame::SortChildrenIfNeeded()
{
if (nsIFrame::IsFrameListSorted<IsLessThanOrEqual>(mFrames)) {
return false;
}
nsIFrame::SortFrameList<IsLessThanOrEqual>(mFrames);
return true;
}
/* virtual */
nsIAtom*
nsFlexContainerFrame::GetType() const
{
return nsGkAtoms::flexContainerFrame;
}
#ifdef DEBUG
NS_IMETHODIMP
nsFlexContainerFrame::GetFrameName(nsAString& aResult) const
{
return MakeFrameName(NS_LITERAL_STRING("FlexContainer"), aResult);
}
#endif // DEBUG
// Helper for BuildDisplayList, to implement this special-case for flex items
// from the spec:
// Flex items paint exactly the same as block-level elements in the
// normal flow, except that 'z-index' values other than 'auto' create
// a stacking context even if 'position' is 'static'.
// http://www.w3.org/TR/2012/CR-css3-flexbox-20120918/#painting
uint32_t
GetDisplayFlagsForFlexItem(nsIFrame* aFrame)
{
MOZ_ASSERT(aFrame->IsFlexItem(), "Should only be called on flex items");
const nsStylePosition* pos = aFrame->StylePosition();
if (pos->mZIndex.GetUnit() == eStyleUnit_Integer) {
return nsIFrame::DISPLAY_CHILD_FORCE_STACKING_CONTEXT;
}
return nsIFrame::DISPLAY_CHILD_FORCE_PSEUDO_STACKING_CONTEXT;
}
void
nsFlexContainerFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
const nsRect& aDirtyRect,
const nsDisplayListSet& aLists)
{
NS_ASSERTION(
nsIFrame::IsFrameListSorted<IsOrderLEQWithDOMFallback>(mFrames),
"Child frames aren't sorted correctly");
DisplayBorderBackgroundOutline(aBuilder, aLists);
// Our children are all block-level, so their borders/backgrounds all go on
// the BlockBorderBackgrounds list.
nsDisplayListSet childLists(aLists, aLists.BlockBorderBackgrounds());
for (nsFrameList::Enumerator e(mFrames); !e.AtEnd(); e.Next()) {
BuildDisplayListForChild(aBuilder, e.get(), aDirtyRect, childLists,
GetDisplayFlagsForFlexItem(e.get()));
}
}
#ifdef DEBUG
// helper for the debugging method below
bool
FrameWantsToBeInAnonymousFlexItem(nsIFrame* aFrame)
{
// Note: This needs to match the logic in
// nsCSSFrameConstructor::FrameConstructionItem::NeedsAnonFlexItem()
return (aFrame->IsFrameOfType(nsIFrame::eLineParticipant) ||
nsGkAtoms::placeholderFrame == aFrame->GetType());
}
// Debugging method, to let us assert that our anonymous flex items are
// set up correctly -- in particular, we assert:
// (1) we don't have any inline non-replaced children
// (2) we don't have any consecutive anonymous flex items
// (3) we don't have any empty anonymous flex items
//
// XXXdholbert This matches what nsCSSFrameConstructor currently does, and what
// the spec used to say. However, the spec has now changed regarding what
// types of content get wrapped in an anonymous flexbox item. The patch that
// implements those changes (in nsCSSFrameConstructor) will need to change
// this method as well.
void
nsFlexContainerFrame::SanityCheckAnonymousFlexItems() const
{
bool prevChildWasAnonFlexItem = false;
for (nsIFrame* child = mFrames.FirstChild(); child;
child = child->GetNextSibling()) {
MOZ_ASSERT(!FrameWantsToBeInAnonymousFlexItem(child),
"frame wants to be inside an anonymous flex item, "
"but it isn't");
if (child->StyleContext()->GetPseudo() ==
nsCSSAnonBoxes::anonymousFlexItem) {
MOZ_ASSERT(!prevChildWasAnonFlexItem,
"two anon flex items in a row (shouldn't happen)");
nsIFrame* firstWrappedChild = child->GetFirstPrincipalChild();
MOZ_ASSERT(firstWrappedChild,
"anonymous flex item is empty (shouldn't happen)");
prevChildWasAnonFlexItem = true;
} else {
prevChildWasAnonFlexItem = false;
}
}
}
#endif // DEBUG
// 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.
static void
FreezeOrRestoreEachFlexibleSize(
const nscoord aTotalViolation,
nsTArray<FlexItem>& aItems)
{
enum FreezeType {
eFreezeEverything,
eFreezeMinViolations,
eFreezeMaxViolations
};
FreezeType freezeType;
if (aTotalViolation == 0) {
freezeType = eFreezeEverything;
} else if (aTotalViolation > 0) {
freezeType = eFreezeMinViolations;
} else { // aTotalViolation < 0
freezeType = eFreezeMaxViolations;
}
for (uint32_t i = 0; i < aItems.Length(); i++) {
FlexItem& item = aItems[i];
MOZ_ASSERT(!item.HadMinViolation() || !item.HadMaxViolation(),
"Can have either min or max violation, but not both");
if (!item.IsFrozen()) {
if (eFreezeEverything == freezeType ||
(eFreezeMinViolations == freezeType && item.HadMinViolation()) ||
(eFreezeMaxViolations == freezeType && item.HadMaxViolation())) {
MOZ_ASSERT(item.GetMainSize() >= item.GetMainMinSize(),
"Freezing item at a size below its minimum");
MOZ_ASSERT(item.GetMainSize() <= item.GetMainMaxSize(),
"Freezing item at a size above its maximum");
item.Freeze();
} // else, we'll reset this item's main size to its flex base size on the
// next iteration of this algorithm.
// Clear this item's violation(s), now that we've dealt with them
item.ClearViolationFlags();
}
}
}
// Implementation of flexbox spec's "Determine sign of flexibility" step.
// NOTE: aTotalFreeSpace should already have the flex items' margin, border,
// & padding values subtracted out.
static bool
ShouldUseFlexGrow(nscoord aTotalFreeSpace,
nsTArray<FlexItem>& aItems)
{
// NOTE: The FlexItem constructor sets its main-size to the
// *hypothetical main size*, which is the flex base size, clamped
// to the min/max range. That's what we want here. Good.
for (uint32_t i = 0; i < aItems.Length(); i++) {
aTotalFreeSpace -= aItems[i].GetMainSize();
if (aTotalFreeSpace <= 0) {
return false;
}
}
MOZ_ASSERT(aTotalFreeSpace > 0,
"if we used up all the space, should've already returned");
return true;
}
// Implementation of flexbox spec's "resolve the flexible lengths" algorithm.
// NOTE: aTotalFreeSpace should already have the flex items' margin, border,
// & padding values subtracted out, so that all we need to do is distribute the
// remaining free space among content-box sizes. (The spec deals with
// margin-box sizes, but we can have fewer values in play & a simpler algorithm
// if we subtract margin/border/padding up front.)
void
nsFlexContainerFrame::ResolveFlexibleLengths(
const FlexboxAxisTracker& aAxisTracker,
nscoord aFlexContainerMainSize,
nsTArray<FlexItem>& aItems)
{
PR_LOG(GetFlexContainerLog(), PR_LOG_DEBUG, ("ResolveFlexibleLengths\n"));
if (aItems.IsEmpty()) {
return;
}
// Subtract space occupied by our items' margins/borders/padding, so we can
// just be dealing with the space available for our flex items' content
// boxes.
nscoord spaceAvailableForFlexItemsContentBoxes = aFlexContainerMainSize;
for (uint32_t i = 0; i < aItems.Length(); i++) {
spaceAvailableForFlexItemsContentBoxes -=
aItems[i].GetMarginBorderPaddingSizeInAxis(aAxisTracker.GetMainAxis());
}
// Determine whether we're going to be growing or shrinking items.
bool havePositiveFreeSpace =
ShouldUseFlexGrow(spaceAvailableForFlexItemsContentBoxes, aItems);
// NOTE: I claim that this chunk of the algorithm (the looping part) needs to
// run the loop at MOST aItems.Length() 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 < aItems.Length(); 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.
nscoord availableFreeSpace = spaceAvailableForFlexItemsContentBoxes;
for (uint32_t i = 0; i < aItems.Length(); i++) {
FlexItem& item = aItems[i];
if (!item.IsFrozen()) {
item.SetMainSize(item.GetFlexBaseSize());
}
availableFreeSpace -= item.GetMainSize();
}
PR_LOG(GetFlexContainerLog(), PR_LOG_DEBUG,
(" available free space = %d\n", availableFreeSpace));
// If sign of free space matches flexType, give each flexible
// item a portion of availableFreeSpace.
if ((availableFreeSpace > 0 && havePositiveFreeSpace) ||
(availableFreeSpace < 0 && !havePositiveFreeSpace)) {
// STRATEGY: On each item, we compute & store its "share" of the total
// flex weight that we've seen so far:
// curFlexWeight / runningFlexWeightSum
//
// 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 flex weights is larger than the
// maximum representable float (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 flex weights as if
// their weights were infinite (dwarfing all the others), and we
// distribute all of the available space among them.
float runningFlexWeightSum = 0.0f;
float largestFlexWeight = 0.0f;
uint32_t numItemsWithLargestFlexWeight = 0;
for (uint32_t i = 0; i < aItems.Length(); i++) {
FlexItem& item = aItems[i];
float curFlexWeight = item.GetFlexWeightToUse(havePositiveFreeSpace);
MOZ_ASSERT(curFlexWeight >= 0.0f, "weights are non-negative");
runningFlexWeightSum += curFlexWeight;
if (NS_finite(runningFlexWeightSum)) {
if (curFlexWeight == 0.0f) {
item.SetShareOfFlexWeightSoFar(0.0f);
} else {
item.SetShareOfFlexWeightSoFar(curFlexWeight /
runningFlexWeightSum);
}
} // else, the sum of weights overflows to infinity, in which
// case we don't bother with "SetShareOfFlexWeightSoFar" since
// we know we won't use it. (instead, we'll just give every
// item with the largest flex weight an equal share of space.)
// Update our largest-flex-weight tracking vars
if (curFlexWeight > largestFlexWeight) {
largestFlexWeight = curFlexWeight;
numItemsWithLargestFlexWeight = 1;
} else if (curFlexWeight == largestFlexWeight) {
numItemsWithLargestFlexWeight++;
}
}
if (runningFlexWeightSum != 0.0f) { // no distribution if no flexibility
PR_LOG(GetFlexContainerLog(), PR_LOG_DEBUG,
(" Distributing available space:"));
for (uint32_t i = aItems.Length() - 1; i < aItems.Length(); --i) {
FlexItem& item = aItems[i];
if (!item.IsFrozen()) {
// To avoid rounding issues, we compute the change in size for this
// item, and then subtract it from the remaining available space.
nscoord sizeDelta = 0;
if (NS_finite(runningFlexWeightSum)) {
float myShareOfRemainingSpace =
item.GetShareOfFlexWeightSoFar();
MOZ_ASSERT(myShareOfRemainingSpace >= 0.0f &&
myShareOfRemainingSpace <= 1.0f,
"my share should be nonnegative fractional amount");
if (myShareOfRemainingSpace == 1.0f) {
// (We special-case 1.0f to avoid float error from converting
// availableFreeSpace from integer*1.0f --> float --> integer)
sizeDelta = availableFreeSpace;
} else if (myShareOfRemainingSpace > 0.0f) {
sizeDelta = NSToCoordRound(availableFreeSpace *
myShareOfRemainingSpace);
}
} else if (item.GetFlexWeightToUse(havePositiveFreeSpace) ==
largestFlexWeight) {
// 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 =
NSToCoordRound(availableFreeSpace /
float(numItemsWithLargestFlexWeight));
numItemsWithLargestFlexWeight--;
}
availableFreeSpace -= sizeDelta;
item.SetMainSize(item.GetMainSize() + sizeDelta);
PR_LOG(GetFlexContainerLog(), PR_LOG_DEBUG,
(" child %d receives %d, for a total of %d\n",
i, sizeDelta, item.GetMainSize()));
}
}
}
}
// Fix min/max violations:
nscoord totalViolation = 0; // keeps track of adjustments for min/max
PR_LOG(GetFlexContainerLog(), PR_LOG_DEBUG,
(" Checking for violations:"));
for (uint32_t i = 0; i < aItems.Length(); i++) {
FlexItem& item = aItems[i];
if (!item.IsFrozen()) {
if (item.GetMainSize() < item.GetMainMinSize()) {
// min violation
totalViolation += item.GetMainMinSize() - item.GetMainSize();
item.SetMainSize(item.GetMainMinSize());
item.SetHadMinViolation();
} else if (item.GetMainSize() > item.GetMainMaxSize()) {
// max violation
totalViolation += item.GetMainMaxSize() - item.GetMainSize();
item.SetMainSize(item.GetMainMaxSize());
item.SetHadMaxViolation();
}
}
}
FreezeOrRestoreEachFlexibleSize(totalViolation, aItems);
PR_LOG(GetFlexContainerLog(), PR_LOG_DEBUG,
(" Total violation: %d\n", totalViolation));
if (totalViolation == 0) {
break;
}
}
// Post-condition: all lengths should've been frozen.
#ifdef DEBUG
for (uint32_t i = 0; i < aItems.Length(); ++i) {
MOZ_ASSERT(aItems[i].IsFrozen(),
"All flexible lengths should've been resolved");
}
#endif // DEBUG
}
MainAxisPositionTracker::
MainAxisPositionTracker(nsFlexContainerFrame* aFlexContainerFrame,
const FlexboxAxisTracker& aAxisTracker,
const nsHTMLReflowState& aReflowState,
const nsTArray<FlexItem>& aItems,
nscoord aContentBoxMainSize)
: PositionTracker(aAxisTracker.GetMainAxis()),
mPackingSpaceRemaining(aContentBoxMainSize), // we chip away at this below
mNumAutoMarginsInMainAxis(0),
mNumPackingSpacesRemaining(0)
{
MOZ_ASSERT(aReflowState.frame == aFlexContainerFrame,
"Expecting the reflow state for the flex container frame");
// 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 (uint32_t i = 0; i < aItems.Length(); i++) {
const FlexItem& curItem = aItems[i];
nscoord itemMarginBoxMainSize =
curItem.GetMainSize() +
curItem.GetMarginBorderPaddingSizeInAxis(aAxisTracker.GetMainAxis());
mPackingSpaceRemaining -= itemMarginBoxMainSize;
mNumAutoMarginsInMainAxis += curItem.GetNumAutoMarginsInAxis(mAxis);
}
if (mPackingSpaceRemaining <= 0) {
// No available packing space to use for resolving auto margins.
mNumAutoMarginsInMainAxis = 0;
}
mJustifyContent = aFlexContainerFrame->StylePosition()->mJustifyContent;
// If packing space is negative, 'justify' behaves like 'start', and
// 'distribute' behaves like 'center'. In those cases, it's simplest to
// just pretend we have a different 'justify-content' value and share code.
if (mPackingSpaceRemaining < 0) {
if (mJustifyContent == NS_STYLE_JUSTIFY_CONTENT_SPACE_BETWEEN) {
mJustifyContent = NS_STYLE_JUSTIFY_CONTENT_FLEX_START;
} else if (mJustifyContent == NS_STYLE_JUSTIFY_CONTENT_SPACE_AROUND) {
mJustifyContent = NS_STYLE_JUSTIFY_CONTENT_CENTER;
}
}
// 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 &&
!aItems.IsEmpty()) {
switch (mJustifyContent) {
case NS_STYLE_JUSTIFY_CONTENT_FLEX_START:
// All packing space should go at the end --> nothing to do here.
break;
case NS_STYLE_JUSTIFY_CONTENT_FLEX_END:
// All packing space goes at the beginning
mPosition += mPackingSpaceRemaining;
break;
case NS_STYLE_JUSTIFY_CONTENT_CENTER:
// Half the packing space goes at the beginning
mPosition += mPackingSpaceRemaining / 2;
break;
case NS_STYLE_JUSTIFY_CONTENT_SPACE_BETWEEN:
MOZ_ASSERT(mPackingSpaceRemaining >= 0,
"negative packing space should make us use 'flex-start' "
"instead of 'space-between'");
// 1 packing space between each flex item, no packing space at ends.
mNumPackingSpacesRemaining = aItems.Length() - 1;
break;
case NS_STYLE_JUSTIFY_CONTENT_SPACE_AROUND:
MOZ_ASSERT(mPackingSpaceRemaining >= 0,
"negative packing space should make us use 'center' "
"instead of 'space-around'");
// 1 packing space between each flex item, plus half a packing space
// at beginning & end. So our number of full packing-spaces is equal
// to the number of flex items.
mNumPackingSpacesRemaining = aItems.Length();
if (mNumPackingSpacesRemaining > 0) {
// The edges (start/end) share one full packing space
nscoord totalEdgePackingSpace =
mPackingSpaceRemaining / mNumPackingSpacesRemaining;
// ...and we'll use half of that right now, at the start
mPosition += 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.
mPackingSpaceRemaining -= totalEdgePackingSpace;
mNumPackingSpacesRemaining--;
}
break;
default:
MOZ_CRASH("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 nsStyleSides& styleMargin = aItem.Frame()->StyleMargin()->mMargin;
for (uint32_t i = 0; i < eNumAxisEdges; i++) {
Side side = kAxisOrientationToSidesMap[mAxis][i];
if (styleMargin.GetUnit(side) == eStyleUnit_Auto) {
// 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 == NS_STYLE_JUSTIFY_CONTENT_SPACE_BETWEEN ||
mJustifyContent == NS_STYLE_JUSTIFY_CONTENT_SPACE_AROUND,
"mNumPackingSpacesRemaining only applies for "
"space-between/space-around");
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(nsFlexContainerFrame* aFlexContainerFrame,
const FlexboxAxisTracker& aAxisTracker,
const nsTArray<FlexItem>& aItems)
: PositionTracker(aAxisTracker.GetCrossAxis()),
mLineCrossSize(0),
mCrossStartToFurthestBaseline(nscoord_MIN) // Starts at -infinity, and then
// we progressively increase it.
{
}
void
SingleLineCrossAxisPositionTracker::
ComputeLineCrossSize(const nsTArray<FlexItem>& aItems)
{
// NOTE: mCrossStartToFurthestBaseline is a member var rather than a local
// var, because we'll need it for baseline-alignment and for computing the
// container's baseline later on.
MOZ_ASSERT(mCrossStartToFurthestBaseline == nscoord_MIN,
"Computing largest baseline offset more than once");
nscoord crossEndToFurthestBaseline = nscoord_MIN;
nscoord largestOuterCrossSize = 0;
for (uint32_t i = 0; i < aItems.Length(); ++i) {
const FlexItem& curItem = aItems[i];
nscoord curOuterCrossSize = curItem.GetCrossSize() +
curItem.GetMarginBorderPaddingSizeInAxis(mAxis);
if (curItem.GetAlignSelf() == NS_STYLE_ALIGN_ITEMS_BASELINE &&
curItem.GetNumAutoMarginsInAxis(mAxis) == 0) {
// FIXME: Once we support multi-line flexbox with "wrap-reverse", that'll
// give us bottom-to-top cross axes. (But for now, we assume eAxis_TB.)
// FIXME: Once we support "writing-mode", we'll have to do baseline
// alignment in vertical flex containers here (w/ horizontal cross-axes).
MOZ_ASSERT(mAxis == eAxis_TB,
"Only expecting to do baseline-alignment in horizontal "
"flex containers, with top-to-bottom cross axis");
// 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 = GetBaselineOffsetFromCrossStart(curItem);
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 mLineCrossSize
// below:
mCrossStartToFurthestBaseline = std::max(mCrossStartToFurthestBaseline,
crossStartToBaseline);
crossEndToFurthestBaseline = std::max(crossEndToFurthestBaseline,
crossEndToBaseline);
} else {
largestOuterCrossSize = std::max(largestOuterCrossSize, curOuterCrossSize);
}
}
// 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-size of all other children.
mLineCrossSize = std::max(mCrossStartToFurthestBaseline +
crossEndToFurthestBaseline,
largestOuterCrossSize);
}
nscoord
SingleLineCrossAxisPositionTracker::
GetBaselineOffsetFromCrossStart(const FlexItem& aItem) const
{
Side crossStartSide = kAxisOrientationToSidesMap[mAxis][eAxisEdge_Start];
// XXXdholbert This assumes cross axis is Top-To-Bottom.
// For bottom-to-top support, probably want to make this depend on
// AxisGrowsInPositiveDirection(mAxis)
return NSCoordSaturatingAdd(aItem.GetAscent(),
aItem.GetMarginComponentForSide(crossStartSide));
}
void
FlexItem::ResolveStretchedCrossSize(nscoord aLineCrossSize,
const FlexboxAxisTracker& aAxisTracker)
{
AxisOrientationType crossAxis = aAxisTracker.GetCrossAxis();
// 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 != NS_STYLE_ALIGN_ITEMS_STRETCH ||
GetNumAutoMarginsInAxis(crossAxis) != 0 ||
eStyleUnit_Auto != GetSizePropertyForAxis(mFrame, crossAxis).GetUnit()) {
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 -
GetMarginBorderPaddingSizeInAxis(crossAxis);
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 state's computed cross-size in our final reflow.
SetCrossSize(stretchedSize);
mIsStretched = true;
}
void
SingleLineCrossAxisPositionTracker::
ResolveAutoMarginsInCrossAxis(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 = mLineCrossSize -
(aItem.GetCrossSize() + aItem.GetMarginBorderPaddingSizeInAxis(mAxis));
if (spaceForAutoMargins <= 0) {
return; // No available space --> nothing to do
}
uint32_t numAutoMargins = aItem.GetNumAutoMarginsInAxis(mAxis);
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 nsStyleSides& styleMargin = aItem.Frame()->StyleMargin()->mMargin;
for (uint32_t i = 0; i < eNumAxisEdges; i++) {
Side side = kAxisOrientationToSidesMap[mAxis][i];
if (styleMargin.GetUnit(side) == eStyleUnit_Auto) {
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 FlexItem& aItem)
{
// We don't do align-self alignment on items that have auto margins
// in the cross axis.
if (aItem.GetNumAutoMarginsInAxis(mAxis)) {
return;
}
switch (aItem.GetAlignSelf()) {
case NS_STYLE_ALIGN_ITEMS_FLEX_START:
case NS_STYLE_ALIGN_ITEMS_STRETCH:
// No space to skip over -- we're done.
// NOTE: 'stretch' behaves like 'start' once we've stretched any
// auto-sized items (which we've already done).
break;
case NS_STYLE_ALIGN_ITEMS_FLEX_END:
mPosition +=
mLineCrossSize -
(aItem.GetCrossSize() +
aItem.GetMarginBorderPaddingSizeInAxis(mAxis));
break;
case NS_STYLE_ALIGN_ITEMS_CENTER:
// Note: If cross-size is odd, the "after" space will get the extra unit.
mPosition +=
(mLineCrossSize -
(aItem.GetCrossSize() +
aItem.GetMarginBorderPaddingSizeInAxis(mAxis))) / 2;
break;
case NS_STYLE_ALIGN_ITEMS_BASELINE:
NS_WARN_IF_FALSE(mCrossStartToFurthestBaseline != nscoord_MIN,
"using uninitialized baseline offset (or working with "
"content that has bogus huge values)");
MOZ_ASSERT(mCrossStartToFurthestBaseline >=
GetBaselineOffsetFromCrossStart(aItem),
"failed at finding largest ascent");
// Advance so that aItem's baseline is aligned with
// largest baseline offset.
mPosition += (mCrossStartToFurthestBaseline -
GetBaselineOffsetFromCrossStart(aItem));
break;
default:
NS_NOTREACHED("Unexpected align-self value");
break;
}
}
FlexboxAxisTracker::FlexboxAxisTracker(nsFlexContainerFrame* aFlexContainerFrame)
{
uint32_t flexDirection =
aFlexContainerFrame->StylePosition()->mFlexDirection;
uint32_t cssDirection =
aFlexContainerFrame->StyleVisibility()->mDirection;
MOZ_ASSERT(cssDirection == NS_STYLE_DIRECTION_LTR ||
cssDirection == NS_STYLE_DIRECTION_RTL,
"Unexpected computed value for 'direction' property");
// (Not asserting for flexDirection here; it's checked by the switch below.)
// These are defined according to writing-modes' definitions of
// start/end (for the inline dimension) and before/after (for the block
// dimension), here:
// http://www.w3.org/TR/css3-writing-modes/#logical-directions
// (NOTE: I'm intentionally not calling this "inlineAxis"/"blockAxis", since
// those terms have explicit definition in the writing-modes spec, which are
// the opposite of how I'd be using them here.)
// XXXdholbert Once we support the 'writing-mode' property, use its value
// here to further customize inlineDimension & blockDimension.
// Inline dimension ("start-to-end"):
AxisOrientationType inlineDimension =
cssDirection == NS_STYLE_DIRECTION_RTL ? eAxis_RL : eAxis_LR;
// Block dimension ("before-to-after"):
AxisOrientationType blockDimension = eAxis_TB;
// Determine main axis:
switch (flexDirection) {
case NS_STYLE_FLEX_DIRECTION_ROW:
mMainAxis = inlineDimension;
break;
case NS_STYLE_FLEX_DIRECTION_ROW_REVERSE:
mMainAxis = GetReverseAxis(inlineDimension);
break;
case NS_STYLE_FLEX_DIRECTION_COLUMN:
mMainAxis = blockDimension;
break;
case NS_STYLE_FLEX_DIRECTION_COLUMN_REVERSE:
mMainAxis = GetReverseAxis(blockDimension);
break;
default:
MOZ_CRASH("Unexpected computed value for 'flex-flow' property");
}
// Determine cross axis:
// (This is set up so that a bogus |flexDirection| value will
// give us blockDimension.
if (flexDirection == NS_STYLE_FLEX_DIRECTION_COLUMN ||
flexDirection == NS_STYLE_FLEX_DIRECTION_COLUMN_REVERSE) {
mCrossAxis = inlineDimension;
} else {
mCrossAxis = blockDimension;
}
// FIXME: Once we support "flex-wrap", check if it's "wrap-reverse"
// here to determine whether we should reverse mCrossAxis.
MOZ_ASSERT(IsAxisHorizontal(mMainAxis) != IsAxisHorizontal(mCrossAxis),
"main & cross axes should be in different dimensions");
// NOTE: Right now, cross axis is never bottom-to-top.
// The only way for it to be different would be if we used a vertical
// "writing-mode" or if we had "flex-wrap: wrap-reverse" -- but we don't
// support either of those yet, so that can't happen right now.
// (When we add support for either of those properties, this assert will
// no longer hold.)
MOZ_ASSERT(mCrossAxis != eAxis_BT, "Not expecting bottom-to-top cross axis");
}
nsresult
nsFlexContainerFrame::GenerateFlexItems(
nsPresContext* aPresContext,
const nsHTMLReflowState& aReflowState,
const FlexboxAxisTracker& aAxisTracker,
nsTArray<FlexItem>& aFlexItems)
{
MOZ_ASSERT(aFlexItems.IsEmpty(), "Expecting outparam to start out empty");
aFlexItems.SetCapacity(mFrames.GetLength());
for (nsFrameList::Enumerator e(mFrames); !e.AtEnd(); e.Next()) {
FlexItem* item = aFlexItems.AppendElement(
GenerateFlexItemForChild(aPresContext, e.get(),
aReflowState, aAxisTracker));
nsresult rv = ResolveFlexItemMaxContentSizing(aPresContext, *item,
aReflowState, aAxisTracker);
NS_ENSURE_SUCCESS(rv,rv);
}
return NS_OK;
}
// Computes the content-box main-size of our flex container.
nscoord
nsFlexContainerFrame::ComputeFlexContainerMainSize(
const nsHTMLReflowState& aReflowState,
const FlexboxAxisTracker& aAxisTracker,
const nsTArray<FlexItem>& aItems)
{
if (IsAxisHorizontal(aAxisTracker.GetMainAxis())) {
// Horizontal case is easy -- our main size is our computed width
// (which is already resolved).
return aReflowState.ComputedWidth();
}
// Vertical case, with non-auto-height:
if (aReflowState.ComputedHeight() != NS_AUTOHEIGHT) {
return aReflowState.ComputedHeight();
}
// Vertical case, with auto-height:
// Resolve auto-height to the sum of our items' hypothetical outer main
// sizes (their outer heights), clamped to our computed min/max main-size
// properties (min-height & max-height).
nscoord sumOfChildHeights = 0;
for (uint32_t i = 0; i < aItems.Length(); ++i) {
sumOfChildHeights +=
aItems[i].GetMainSize() +
aItems[i].GetMarginBorderPaddingSizeInAxis(aAxisTracker.GetMainAxis());
}
return NS_CSS_MINMAX(sumOfChildHeights,
aReflowState.mComputedMinHeight,
aReflowState.mComputedMaxHeight);
}
void
nsFlexContainerFrame::PositionItemInMainAxis(
MainAxisPositionTracker& aMainAxisPosnTracker,
FlexItem& aItem)
{
nscoord itemMainBorderBoxSize =
aItem.GetMainSize() +
aItem.GetBorderPaddingSizeInAxis(aMainAxisPosnTracker.GetAxis());
// Resolve any main-axis 'auto' margins on aChild to an actual value.
aMainAxisPosnTracker.ResolveAutoMarginsInMainAxis(aItem);
// Advance our position tracker to child's upper-left content-box corner,
// and use that as its position in the main axis.
aMainAxisPosnTracker.EnterMargin(aItem.GetMargin());
aMainAxisPosnTracker.EnterChildFrame(itemMainBorderBoxSize);
aItem.SetMainPosition(aMainAxisPosnTracker.GetPosition());
aMainAxisPosnTracker.ExitChildFrame(itemMainBorderBoxSize);
aMainAxisPosnTracker.ExitMargin(aItem.GetMargin());
aMainAxisPosnTracker.TraversePackingSpace();
}
// Helper method to take care of children who ASK_FOR_BASELINE, when
// we need their baseline.
static void
ResolveReflowedChildAscent(nsIFrame* aFrame,
nsHTMLReflowMetrics& aChildDesiredSize)
{
if (aChildDesiredSize.ascent == nsHTMLReflowMetrics::ASK_FOR_BASELINE) {
// Use GetFirstLineBaseline(), or just GetBaseline() if that fails.
if (!nsLayoutUtils::GetFirstLineBaseline(aFrame,
&aChildDesiredSize.ascent)) {
aChildDesiredSize.ascent = aFrame->GetBaseline();
}
}
}
nsresult
nsFlexContainerFrame::SizeItemInCrossAxis(
nsPresContext* aPresContext,
const FlexboxAxisTracker& aAxisTracker,
nsHTMLReflowState& aChildReflowState,
FlexItem& aItem)
{
// In vertical flexbox (with horizontal cross-axis), we can just trust the
// reflow state's computed-width as our cross-size. We also don't need to
// record the baseline because we'll have converted any "align-self:baseline"
// items to be "align-self:flex-start" in the FlexItem constructor.
// FIXME: Once we support writing-mode (vertical text), we will be able to
// have baseline-aligned items in a vertical flexbox, and we'll need to
// record baseline information here.
if (IsAxisHorizontal(aAxisTracker.GetCrossAxis())) {
MOZ_ASSERT(aItem.GetAlignSelf() != NS_STYLE_ALIGN_ITEMS_BASELINE,
"In vert flex container, we depend on FlexItem constructor to "
"convert 'align-self: baseline' to 'align-self: flex-start'");
aItem.SetCrossSize(aChildReflowState.ComputedWidth());
return NS_OK;
}
MOZ_ASSERT(!aItem.HadMeasuringReflow(),
"We shouldn't need more than one measuring reflow");
if (aItem.GetAlignSelf() == NS_STYLE_ALIGN_ITEMS_STRETCH) {
// This item's got "align-self: stretch", so we probably imposed a
// stretched computed height on it during its previous reflow. We're
// not imposing that height for *this* measuring reflow, so we need to
// tell it to treat this reflow as a vertical resize (regardless of
// whether any of its ancestors are being resized).
aChildReflowState.mFlags.mVResize = true;
}
nsHTMLReflowMetrics childDesiredSize;
nsReflowStatus childReflowStatus;
nsresult rv = ReflowChild(aItem.Frame(), aPresContext,
childDesiredSize, aChildReflowState,
0, 0, NS_FRAME_NO_MOVE_FRAME,
childReflowStatus);
aItem.SetHadMeasuringReflow();
NS_ENSURE_SUCCESS(rv, rv);
// XXXdholbert Once we do pagination / splitting, we'll need to actually
// handle incomplete childReflowStatuses. But for now, we give our kids
// unconstrained available height, which means they should always complete.
MOZ_ASSERT(NS_FRAME_IS_COMPLETE(childReflowStatus),
"We gave flex item unconstrained available height, 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)
rv = FinishReflowChild(aItem.Frame(), aPresContext,
&aChildReflowState, childDesiredSize, 0, 0, 0);
NS_ENSURE_SUCCESS(rv, rv);
// Save the sizing info that we learned from this reflow
// -----------------------------------------------------
// Tentatively store the child's desired content-box cross-size.
// Note that childDesiredSize is the border-box size, so we have to
// subtract border & padding to get the content-box size.
// (Note that at this point in the code, we know our cross axis is vertical,
// so we don't bother with making aAxisTracker pick the cross-axis component
// for us.)
nscoord crossAxisBorderPadding = aItem.GetBorderPadding().TopBottom();
if (childDesiredSize.height < crossAxisBorderPadding) {
// Child's requested size isn't large enough for its border/padding!
// This is OK for the trivial nsFrame::Reflow() impl, but other frame
// classes should know better. So, if we get here, the child had better be
// an instance of nsFrame (i.e. it should return null from GetType()).
// XXXdholbert Once we've fixed bug 765861, we should upgrade this to an
// assertion that trivially passes if bug 765861's flag has been flipped.
NS_WARN_IF_FALSE(!aItem.Frame()->GetType(),
"Child should at least request space for border/padding");
aItem.SetCrossSize(0);
} else {
// (normal case)
aItem.SetCrossSize(childDesiredSize.height - crossAxisBorderPadding);
}
// If we need to do baseline-alignment, store the child's ascent.
if (aItem.GetAlignSelf() == NS_STYLE_ALIGN_ITEMS_BASELINE) {
ResolveReflowedChildAscent(aItem.Frame(), childDesiredSize);
aItem.SetAscent(childDesiredSize.ascent);
}
return NS_OK;
}
void
nsFlexContainerFrame::PositionItemInCrossAxis(
nscoord aLineStartPosition,
SingleLineCrossAxisPositionTracker& aLineCrossAxisPosnTracker,
FlexItem& aItem)
{
MOZ_ASSERT(aLineCrossAxisPosnTracker.GetPosition() == 0,
"per-line cross-axis position tracker wasn't correctly reset");
aLineCrossAxisPosnTracker.ResolveAutoMarginsInCrossAxis(aItem);
// Compute the cross-axis position of this item
nscoord itemCrossBorderBoxSize =
aItem.GetCrossSize() +
aItem.GetBorderPaddingSizeInAxis(aLineCrossAxisPosnTracker.GetAxis());
aLineCrossAxisPosnTracker.EnterAlignPackingSpace(aItem);
aLineCrossAxisPosnTracker.EnterMargin(aItem.GetMargin());
aLineCrossAxisPosnTracker.EnterChildFrame(itemCrossBorderBoxSize);
aItem.SetCrossPosition(aLineStartPosition +
aLineCrossAxisPosnTracker.GetPosition());
// Back out to cross-axis edge of the line.
aLineCrossAxisPosnTracker.ResetPosition();
}
NS_IMETHODIMP
nsFlexContainerFrame::Reflow(nsPresContext* aPresContext,
nsHTMLReflowMetrics& aDesiredSize,
const nsHTMLReflowState& aReflowState,
nsReflowStatus& aStatus)
{
DO_GLOBAL_REFLOW_COUNT("nsFlexContainerFrame");
DISPLAY_REFLOW(aPresContext, this, aReflowState, aDesiredSize, aStatus);
PR_LOG(GetFlexContainerLog(), PR_LOG_DEBUG,
("Reflow() for nsFlexContainerFrame %p\n", this));
if (IsFrameTreeTooDeep(aReflowState, aDesiredSize, aStatus)) {
return NS_OK;
}
aStatus = NS_FRAME_COMPLETE;
// We (and our children) can only depend on our ancestor's height if we have
// a percent-height, or if we're positioned and we have "top" and "bottom"
// set and have height:auto. (There are actually other cases, too -- e.g. if
// our parent is itself a vertical flex container and we're flexible -- but
// we'll let our ancestors handle those sorts of cases.)
const nsStylePosition* stylePos = StylePosition();
if (stylePos->mHeight.HasPercent() ||
(StyleDisplay()->IsAbsolutelyPositionedStyle() &&
eStyleUnit_Auto == stylePos->mHeight.GetUnit() &&
eStyleUnit_Auto != stylePos->mOffset.GetTopUnit() &&
eStyleUnit_Auto != stylePos->mOffset.GetBottomUnit())) {
AddStateBits(NS_FRAME_CONTAINS_RELATIVE_HEIGHT);
}
#ifdef DEBUG
SanityCheckAnonymousFlexItems();
#endif // DEBUG
// If we've never reordered our children, then we can trust that they're
// already in DOM-order, and we only need to consider their "order" property
// when checking them for sortedness & sorting them.
//
// After we actually sort them, though, we can't trust that they're in DOM
// order anymore. So, from that point on, our sort & sorted-order-checking
// operations need to use a fancier LEQ function that also takes DOM order
// into account, so that we can honor the spec's requirement that frames w/
// equal "order" values are laid out in DOM order.
if (!mChildrenHaveBeenReordered) {
mChildrenHaveBeenReordered =
SortChildrenIfNeeded<IsOrderLEQ>();
} else {
SortChildrenIfNeeded<IsOrderLEQWithDOMFallback>();
}
const FlexboxAxisTracker axisTracker(this);
// Generate a list of our flex items (already sorted).
nsTArray<FlexItem> items;
nsresult rv = GenerateFlexItems(aPresContext, aReflowState,
axisTracker, items);
NS_ENSURE_SUCCESS(rv, rv);
const nscoord contentBoxMainSize =
ComputeFlexContainerMainSize(aReflowState, axisTracker, items);
ResolveFlexibleLengths(axisTracker, contentBoxMainSize, items);
// Cross Size Determination - Flexbox spec section 9.4
// ===================================================
// Calculate the hypothetical cross size of each item:
for (uint32_t i = 0; i < items.Length(); ++i) {
FlexItem& curItem = items[i];
// (If the item's already been stretched, then it already knows its
// cross size. Don't bother trying to recalculate it.)
if (!curItem.IsStretched()) {
nsHTMLReflowState childReflowState(aPresContext, aReflowState,
curItem.Frame(),
nsSize(aReflowState.ComputedWidth(),
NS_UNCONSTRAINEDSIZE));
// Override computed main-size
if (IsAxisHorizontal(axisTracker.GetMainAxis())) {
childReflowState.SetComputedWidth(curItem.GetMainSize());
} else {
childReflowState.SetComputedHeight(curItem.GetMainSize());
}
nsresult rv = SizeItemInCrossAxis(aPresContext, axisTracker,
childReflowState, curItem);
NS_ENSURE_SUCCESS(rv, rv);
}
}
// Calculate the cross size of our (single) flex line:
// Set up state for cross-axis alignment, at a high level (outside the
// scope of a particular flex line)
CrossAxisPositionTracker
crossAxisPosnTracker(this, axisTracker, aReflowState);
// Set up state for cross-axis-positioning of children _within_ a single
// flex line.
SingleLineCrossAxisPositionTracker
lineCrossAxisPosnTracker(this, axisTracker, items);
lineCrossAxisPosnTracker.ComputeLineCrossSize(items);
// XXXdholbert Once we've got multi-line flexbox support: here, after we've
// computed the cross size of all lines, we need to check if if
// 'align-content' is 'stretch' -- if it is, we need to give each line an
// additional share of our flex container's desired cross-size. (if it's
// not NS_AUTOHEIGHT and there's any cross-size left over to distribute)
// Calculate the content-box cross size of our flex container:
nscoord contentBoxCrossSize =
GET_CROSS_COMPONENT(axisTracker,
aReflowState.ComputedWidth(),
aReflowState.ComputedHeight());
if (contentBoxCrossSize == NS_AUTOHEIGHT) {
// Unconstrained 'auto' cross-size: shrink-wrap our line(s), subject
// to our min-size / max-size constraints in that axis.
nscoord minCrossSize = GET_CROSS_COMPONENT(axisTracker,
aReflowState.mComputedMinWidth,
aReflowState.mComputedMinHeight);
nscoord maxCrossSize = GET_CROSS_COMPONENT(axisTracker,
aReflowState.mComputedMaxWidth,
aReflowState.mComputedMaxHeight);
contentBoxCrossSize =
NS_CSS_MINMAX(lineCrossAxisPosnTracker.GetLineCrossSize(),
minCrossSize, maxCrossSize);
}
if (lineCrossAxisPosnTracker.GetLineCrossSize() !=
contentBoxCrossSize) {
// XXXdholbert When we support multi-line flex containers, we should
// distribute any extra space among or between our lines here according
// to 'align-content'. For now, we do the single-line special behavior:
// "If the flex container has only a single line (even if it's a
// multi-line flex container), the cross size of the flex line is the
// flex container's inner cross size."
lineCrossAxisPosnTracker.SetLineCrossSize(contentBoxCrossSize);
}
// Set the flex container's baseline, from its baseline-aligned items.
// (This might give us nscoord_MIN if we don't have any baseline-aligned
// flex items. That's OK, we'll update it below.)
nscoord flexContainerAscent =
lineCrossAxisPosnTracker.GetCrossStartToFurthestBaseline();
if (flexContainerAscent != nscoord_MIN) {
// Add top borderpadding, so our ascent is w.r.t. border-box
flexContainerAscent += aReflowState.mComputedBorderPadding.top;
}
// Main-Axis Alignment - Flexbox spec section 9.5
// ==============================================
MainAxisPositionTracker mainAxisPosnTracker(this, axisTracker,
aReflowState, items,
contentBoxMainSize);
for (uint32_t i = 0; i < items.Length(); ++i) {
PositionItemInMainAxis(mainAxisPosnTracker, items[i]);
}
// Cross-Axis Alignment - Flexbox spec section 9.6
// ===============================================
for (uint32_t i = 0; i < items.Length(); ++i) {
// Resolve stretched cross-size, if appropriate
nscoord lineCrossSize = lineCrossAxisPosnTracker.GetLineCrossSize();
items[i].ResolveStretchedCrossSize(lineCrossSize, axisTracker);
// ...and position.
PositionItemInCrossAxis(crossAxisPosnTracker.GetPosition(),
lineCrossAxisPosnTracker, items[i]);
}
// 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.
nsMargin containerBorderPadding(aReflowState.mComputedBorderPadding);
ApplySkipSides(containerBorderPadding, &aReflowState);
const nsPoint containerContentBoxOrigin(containerBorderPadding.left,
containerBorderPadding.top);
// FINAL REFLOW: Give each child frame another chance to reflow, now that
// we know its final size and position.
for (uint32_t i = 0; i < items.Length(); ++i) {
FlexItem& curItem = items[i];
nsPoint physicalPosn = axisTracker.PhysicalPositionFromLogicalPosition(
curItem.GetMainPosition(),
curItem.GetCrossPosition(),
contentBoxMainSize,
contentBoxCrossSize);
// Adjust physicalPosn to be relative to the container's border-box
// (i.e. its frame rect), instead of the container's content-box:
physicalPosn += containerContentBoxOrigin;
nsHTMLReflowState childReflowState(aPresContext, aReflowState,
curItem.Frame(),
nsSize(aReflowState.ComputedWidth(),
NS_UNCONSTRAINEDSIZE));
// Keep track of whether we've overriden the child's computed height
// and/or width, so we can set its resize flags accordingly.
bool didOverrideComputedWidth = false;
bool didOverrideComputedHeight = false;
// Override computed main-size
if (IsAxisHorizontal(axisTracker.GetMainAxis())) {
childReflowState.SetComputedWidth(curItem.GetMainSize());
didOverrideComputedWidth = true;
} else {
childReflowState.SetComputedHeight(curItem.GetMainSize());
didOverrideComputedHeight = true;
}
// Override reflow state's computed cross-size, for stretched items.
if (curItem.IsStretched()) {
MOZ_ASSERT(curItem.GetAlignSelf() == NS_STYLE_ALIGN_ITEMS_STRETCH,
"stretched item w/o 'align-self: stretch'?");
if (IsAxisHorizontal(axisTracker.GetCrossAxis())) {
childReflowState.SetComputedWidth(curItem.GetCrossSize());
didOverrideComputedWidth = true;
} else {
// If this item's height is stretched, it's a relative height.
curItem.Frame()->AddStateBits(NS_FRAME_CONTAINS_RELATIVE_HEIGHT);
childReflowState.SetComputedHeight(curItem.GetCrossSize());
didOverrideComputedHeight = true;
}
}
// XXXdholbert Might need to actually set the correct margins in the
// reflow state at some point, so that they can be saved on the frame for
// UsedMarginProperty(). Maybe doesn't matter though...?
// If we're overriding the computed width or height, *and* we had an
// earlier "measuring" reflow, then this upcoming reflow needs to be
// treated as a resize.
if (curItem.HadMeasuringReflow()) {
if (didOverrideComputedWidth) {
// (This is somewhat redundant, since the reflow state already
// sets mHResize whenever our computed width has changed since the
// previous reflow. Still, it's nice for symmetry, and it may become
// necessary once we support orthogonal flows.)
childReflowState.mFlags.mHResize = true;
}
if (didOverrideComputedHeight) {
childReflowState.mFlags.mVResize = true;
}
}
// NOTE: Be very careful about doing anything else with childReflowState
// after this point, because some of its methods (e.g. SetComputedWidth)
// internally call InitResizeFlags and stomp on mVResize & mHResize.
nsHTMLReflowMetrics childDesiredSize;
nsReflowStatus childReflowStatus;
nsresult rv = ReflowChild(curItem.Frame(), aPresContext,
childDesiredSize, childReflowState,
physicalPosn.x, physicalPosn.y,
0, childReflowStatus);
NS_ENSURE_SUCCESS(rv, rv);
// XXXdholbert Once we do pagination / splitting, we'll need to actually
// handle incomplete childReflowStatuses. But for now, we give our kids
// unconstrained available height, which means they should always
// complete.
MOZ_ASSERT(NS_FRAME_IS_COMPLETE(childReflowStatus),
"We gave flex item unconstrained available height, so it "
"should be complete");
childReflowState.ApplyRelativePositioning(&physicalPosn);
rv = FinishReflowChild(curItem.Frame(), aPresContext,
&childReflowState, childDesiredSize,
physicalPosn.x, physicalPosn.y, 0);
NS_ENSURE_SUCCESS(rv, rv);
// If this is our first child and we haven't established a baseline for
// the container yet, then use this child's baseline as the container's
// baseline.
if (i == 0 && flexContainerAscent == nscoord_MIN) {
ResolveReflowedChildAscent(curItem.Frame(), childDesiredSize);
// (We use GetNormalPosition() instead of physicalPosn because we don't
// want relative positioning on the child to affect the baseline that we
// read from it).
flexContainerAscent = curItem.Frame()->GetNormalPosition().y +
childDesiredSize.ascent;
}
}
nsSize desiredContentBoxSize =
axisTracker.PhysicalSizeFromLogicalSizes(contentBoxMainSize,
contentBoxCrossSize);
aDesiredSize.width = desiredContentBoxSize.width +
containerBorderPadding.LeftRight();
aDesiredSize.height = desiredContentBoxSize.height +
containerBorderPadding.TopBottom();
if (flexContainerAscent == nscoord_MIN) {
// Still don't have our baseline set -- this happens if we have no
// children (or if our children are huge enough that they have nscoord_MIN
// as their baseline... in which case, we'll use the wrong baseline, but no
// big deal)
NS_WARN_IF_FALSE(items.IsEmpty(),
"Have flex items but didn't get an ascent - that's odd "
"(or there are just gigantic sizes involved)");
// Per spec, just use the bottom of content-box.
flexContainerAscent = aDesiredSize.height -
aReflowState.mComputedBorderPadding.bottom;
}
aDesiredSize.ascent = flexContainerAscent;
// Overflow area = union(my overflow area, kids' overflow areas)
aDesiredSize.SetOverflowAreasToDesiredBounds();
for (nsFrameList::Enumerator e(mFrames); !e.AtEnd(); e.Next()) {
ConsiderChildOverflow(aDesiredSize.mOverflowAreas, e.get());
}
FinishReflowWithAbsoluteFrames(aPresContext, aDesiredSize,
aReflowState, aStatus);
NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize)
return NS_OK;
}
/* virtual */ nscoord
nsFlexContainerFrame::GetMinWidth(nsRenderingContext* aRenderingContext)
{
FlexboxAxisTracker axisTracker(this);
nscoord minWidth = 0;
for (nsFrameList::Enumerator e(mFrames); !e.AtEnd(); e.Next()) {
nscoord childMinWidth =
nsLayoutUtils::IntrinsicForContainer(aRenderingContext, e.get(),
nsLayoutUtils::MIN_WIDTH);
if (IsAxisHorizontal(axisTracker.GetMainAxis())) {
minWidth += childMinWidth;
} else {
minWidth = std::max(minWidth, childMinWidth);
}
}
return minWidth;
}
/* virtual */ nscoord
nsFlexContainerFrame::GetPrefWidth(nsRenderingContext* aRenderingContext)
{
// XXXdholbert Optimization: We could cache our intrinsic widths like
// nsBlockFrame does (and return it early from this function if it's set).
// Whenever anything happens that might change it, set it to
// NS_INTRINSIC_WIDTH_UNKNOWN (like nsBlockFrame::MarkIntrinsicWidthsDirty
// does)
FlexboxAxisTracker axisTracker(this);
nscoord prefWidth = 0;
for (nsFrameList::Enumerator e(mFrames); !e.AtEnd(); e.Next()) {
nscoord childPrefWidth =
nsLayoutUtils::IntrinsicForContainer(aRenderingContext, e.get(),
nsLayoutUtils::PREF_WIDTH);
if (IsAxisHorizontal(axisTracker.GetMainAxis())) {
prefWidth += childPrefWidth;
} else {
prefWidth = std::max(prefWidth, childPrefWidth);
}
}
return prefWidth;
}
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