Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 675 insertions, 0 deletions

diff --git a/layout/generic/nsFlexContainerFrame.h b/layout/generic/nsFlexContainerFrame.h
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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" and "display: -webkit-box" */
+
+#ifndef nsFlexContainerFrame_h___
+#define nsFlexContainerFrame_h___
+
+#include <tuple>
+
+#include "mozilla/dom/FlexBinding.h"
+#include "mozilla/UniquePtr.h"
+#include "nsContainerFrame.h"
+#include "nsILineIterator.h"
+
+namespace mozilla {
+class LogicalPoint;
+class PresShell;
+}  // namespace mozilla
+
+nsContainerFrame* NS_NewFlexContainerFrame(mozilla::PresShell* aPresShell,
+                                           mozilla::ComputedStyle* aStyle);
+
+/**
+ * These structures are used to capture data during reflow to be
+ * extracted by devtools via Chrome APIs. The structures are only
+ * created when requested in GetFlexFrameWithComputedInfo(), and
+ * the structures are attached to the nsFlexContainerFrame via the
+ * FlexContainerInfo property.
+ */
+struct ComputedFlexItemInfo {
+  nsCOMPtr<nsINode> mNode;
+  nsRect mFrameRect;
+  /**
+   * mMainBaseSize is a measure of the size of the item in the main
+   * axis before the flex sizing algorithm is applied. In the spec,
+   * this is called "flex base size", but we use this name to connect
+   * the value to the other main axis sizes.
+   */
+  nscoord mMainBaseSize;
+  /**
+   * mMainDeltaSize is the amount that the flex sizing algorithm
+   * adds to the mMainBaseSize, before clamping to mMainMinSize and
+   * mMainMaxSize. This can be thought of as the amount by which the
+   * flex layout algorithm "wants" to shrink or grow the item, and
+   * would do, if it was unconstrained. Since the flex sizing
+   * algorithm proceeds linearly, the mMainDeltaSize for an item only
+   * respects the resolved size of items already frozen.
+   */
+  nscoord mMainDeltaSize;
+  nscoord mMainMinSize;
+  nscoord mMainMaxSize;
+  nscoord mCrossMinSize;
+  nscoord mCrossMaxSize;
+  mozilla::dom::FlexItemClampState mClampState;
+};
+
+struct ComputedFlexLineInfo {
+  nsTArray<ComputedFlexItemInfo> mItems;
+  nscoord mCrossStart;
+  nscoord mCrossSize;
+  nscoord mFirstBaselineOffset;
+  nscoord mLastBaselineOffset;
+  mozilla::dom::FlexLineGrowthState mGrowthState;
+};
+
+struct ComputedFlexContainerInfo {
+  nsTArray<ComputedFlexLineInfo> mLines;
+  mozilla::dom::FlexPhysicalDirection mMainAxisDirection;
+  mozilla::dom::FlexPhysicalDirection mCrossAxisDirection;
+};
+
+/**
+ * Helper class to get the orientation of a flex container's axes.
+ */
+class MOZ_STACK_CLASS FlexboxAxisInfo final {
+ public:
+  explicit FlexboxAxisInfo(const nsIFrame* aFlexContainer);
+
+  // Is our main axis the inline axis? (Are we 'flex-direction:row[-reverse]'?)
+  bool mIsRowOriented = true;
+
+  // Is our main axis in the opposite direction as mWM's corresponding axis?
+  // (e.g. RTL vs LTR)
+  bool mIsMainAxisReversed = false;
+
+  // Is our cross axis in the opposite direction as mWM's corresponding axis?
+  // (e.g. BTT vs TTB)
+  bool mIsCrossAxisReversed = false;
+
+ private:
+  // Helpers for constructor which determine the orientation of our axes, based
+  // on legacy box properties (-webkit-box-orient, -webkit-box-direction) or
+  // modern flexbox properties (flex-direction, flex-wrap) depending on whether
+  // the flex container is a "legacy box" (as determined by IsLegacyBox).
+  void InitAxesFromLegacyProps(const nsIFrame* aFlexContainer);
+  void InitAxesFromModernProps(const nsIFrame* aFlexContainer);
+};
+
+/**
+ * This is the rendering object used for laying out elements with
+ * "display: flex" or "display: inline-flex".
+ *
+ * We also use this class for elements with "display: -webkit-box" or
+ * "display: -webkit-inline-box" (but not "-moz-box" / "-moz-inline-box" --
+ * those are rendered with old-school XUL frame classes).
+ *
+ * Note: we represent the -webkit-box family of properties (-webkit-box-orient,
+ * -webkit-box-flex, etc.) as aliases for their -moz equivalents.  And for
+ * -webkit-{inline-}box containers, nsFlexContainerFrame will honor those
+ * "legacy" properties for alignment/flexibility/etc. *instead of* honoring the
+ * modern flexbox & alignment properties.  For brevity, many comments in
+ * nsFlexContainerFrame.cpp simply refer to these properties using their
+ * "-webkit" versions, since we're mostly expecting to encounter them in that
+ * form. (Technically, the "-moz" versions of these properties *can* influence
+ * layout here as well (since that's what the -webkit versions are aliased to)
+ * -- but only inside of a "display:-webkit-{inline-}box" container.)
+ */
+class nsFlexContainerFrame final : public nsContainerFrame,
+                                   public nsILineIterator {
+ public:
+  NS_DECL_FRAMEARENA_HELPERS(nsFlexContainerFrame)
+  NS_DECL_QUERYFRAME
+
+  // Factory method:
+  friend nsContainerFrame* NS_NewFlexContainerFrame(
+      mozilla::PresShell* aPresShell, ComputedStyle* aStyle);
+
+  // Forward-decls of helper classes
+  class FlexItem;
+  class FlexLine;
+  class FlexboxAxisTracker;
+  struct StrutInfo;
+  class CachedBAxisMeasurement;
+  class CachedFlexItemData;
+  struct SharedFlexData;
+  struct PerFragmentFlexData;
+  class FlexItemIterator;
+
+  // nsIFrame overrides
+  void Init(nsIContent* aContent, nsContainerFrame* aParent,
+            nsIFrame* aPrevInFlow) override;
+
+  void BuildDisplayList(nsDisplayListBuilder* aBuilder,
+                        const nsDisplayListSet& aLists) override;
+
+  void MarkIntrinsicISizesDirty() override;
+
+  void Reflow(nsPresContext* aPresContext, ReflowOutput& aReflowOutput,
+              const ReflowInput& aReflowInput,
+              nsReflowStatus& aStatus) override;
+
+  nscoord GetMinISize(gfxContext* aRenderingContext) override;
+  nscoord GetPrefISize(gfxContext* aRenderingContext) override;
+
+#ifdef DEBUG_FRAME_DUMP
+  nsresult GetFrameName(nsAString& aResult) const override;
+#endif
+
+  Maybe<nscoord> GetNaturalBaselineBOffset(
+      mozilla::WritingMode aWM, BaselineSharingGroup aBaselineGroup,
+      BaselineExportContext) const override;
+
+  // Unions the child overflow from our in-flow children.
+  void UnionInFlowChildOverflow(mozilla::OverflowAreas&);
+
+  // Unions the child overflow from all our children, including out of flows.
+  void UnionChildOverflow(mozilla::OverflowAreas&) final;
+
+  // nsContainerFrame overrides
+  bool DrainSelfOverflowList() override;
+  void AppendFrames(ChildListID aListID, nsFrameList&& aFrameList) override;
+  void InsertFrames(ChildListID aListID, nsIFrame* aPrevFrame,
+                    const nsLineList::iterator* aPrevFrameLine,
+                    nsFrameList&& aFrameList) override;
+  void RemoveFrame(DestroyContext&, ChildListID, nsIFrame*) override;
+  mozilla::StyleAlignFlags CSSAlignmentForAbsPosChild(
+      const ReflowInput& aChildRI,
+      mozilla::LogicalAxis aLogicalAxis) const override;
+
+  /**
+   * Helper function to calculate packing space and initial offset of alignment
+   * subjects in MainAxisPositionTracker() and CrossAxisPositionTracker() for
+   * space-between, space-around, and space-evenly.
+   *    * @param aNumThingsToPack             Number of alignment subjects.
+   * @param aAlignVal                    Value for align-content or
+   *                                     justify-content.
+   * @param aFirstSubjectOffset          Outparam for first subject offset.
+   * @param aNumPackingSpacesRemaining   Outparam for number of equal-sized
+   *                                     packing spaces to apply between each
+   *                                     alignment subject.
+   * @param aPackingSpaceRemaining       Outparam for total amount of packing
+   *                                     space to be divided up.
+   */
+  static void CalculatePackingSpace(
+      uint32_t aNumThingsToPack,
+      const mozilla::StyleContentDistribution& aAlignVal,
+      nscoord* aFirstSubjectOffset, uint32_t* aNumPackingSpacesRemaining,
+      nscoord* aPackingSpaceRemaining);
+
+  /**
+   * This property is created by a call to
+   * nsFlexContainerFrame::GetFlexFrameWithComputedInfo.
+   */
+  NS_DECLARE_FRAME_PROPERTY_DELETABLE(FlexContainerInfo,
+                                      ComputedFlexContainerInfo)
+  /**
+   * This function should only be called on a nsFlexContainerFrame
+   * that has just been returned by a call to
+   * GetFlexFrameWithComputedInfo.
+   */
+  const ComputedFlexContainerInfo* GetFlexContainerInfo() {
+    const ComputedFlexContainerInfo* info = GetProperty(FlexContainerInfo());
+    NS_WARNING_ASSERTION(info,
+                         "Property generation wasn't requested. "
+                         "This is a known issue in Print Preview. "
+                         "See Bug 1157012.");
+    return info;
+  }
+
+  /**
+   * Return aFrame as a flex frame after ensuring it has computed flex info.
+   * @return nullptr if aFrame is null or doesn't have a flex frame
+   *         as its content insertion frame.
+   * @note this might destroy layout/style data since it may flush layout.
+   */
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  static nsFlexContainerFrame* GetFlexFrameWithComputedInfo(nsIFrame* aFrame);
+
+  /**
+   * Given a frame for a flex item, this method returns true IFF that flex
+   * item's inline axis is the same as (i.e. not orthogonal to) its flex
+   * container's main axis.
+   *
+   * (This method is only intended to be used from external
+   * callers. Inside of flex reflow code, FlexItem::IsInlineAxisMainAxis() is
+   * equivalent & more optimal.)
+   *
+   * @param aFrame a flex item (must return true from IsFlexItem)
+   * @return true iff aFrame's inline axis is the same as (i.e. not orthogonal
+   *              to) its flex container's main axis. Otherwise, false.
+   */
+  static bool IsItemInlineAxisMainAxis(nsIFrame* aFrame);
+
+  /**
+   * Returns true iff the given computed 'flex-basis' & main-size property
+   * values collectively represent a used flex-basis of 'content'.
+   * See https://drafts.csswg.org/css-flexbox-1/#valdef-flex-basis-auto
+   *
+   * @param aFlexBasis the computed 'flex-basis' for a flex item.
+   * @param aMainSize the computed main-size property for a flex item.
+   */
+  static bool IsUsedFlexBasisContent(const mozilla::StyleFlexBasis& aFlexBasis,
+                                     const mozilla::StyleSize& aMainSize);
+
+  /**
+   * Callback for nsIFrame::MarkIntrinsicISizesDirty() on a flex item.
+   */
+  static void MarkCachedFlexMeasurementsDirty(nsIFrame* aItemFrame);
+
+  bool CanProvideLineIterator() const final { return true; }
+  nsILineIterator* GetLineIterator() final { return this; }
+  int32_t GetNumLines() const final;
+  bool IsLineIteratorFlowRTL() final;
+  mozilla::Result<LineInfo, nsresult> GetLine(int32_t aLineNumber) final;
+  int32_t FindLineContaining(nsIFrame* aFrame, int32_t aStartLine = 0) final;
+  NS_IMETHOD FindFrameAt(int32_t aLineNumber, nsPoint aPos,
+                         nsIFrame** aFrameFound, bool* aPosIsBeforeFirstFrame,
+                         bool* aPosIsAfterLastFrame) final;
+  NS_IMETHOD CheckLineOrder(int32_t aLine, bool* aIsReordered,
+                            nsIFrame** aFirstVisual,
+                            nsIFrame** aLastVisual) final;
+
+ protected:
+  // Protected constructor & destructor
+  explicit nsFlexContainerFrame(ComputedStyle* aStyle,
+                                nsPresContext* aPresContext)
+      : nsContainerFrame(aStyle, aPresContext, kClassID) {}
+
+  virtual ~nsFlexContainerFrame();
+
+  // Protected flex-container-specific methods / member-vars
+
+  /**
+   * This method does the bulk of the flex layout, implementing the algorithm
+   * described at: https://drafts.csswg.org/css-flexbox-1/#layout-algorithm
+   * (with a few initialization pieces happening in the caller, Reflow().
+   *
+   * (The logic behind the division of work between Reflow and DoFlexLayout is
+   * as follows: DoFlexLayout() begins at the step that we have to jump back
+   * to, if we find any visibility:collapse children, and Reflow() does
+   * everything before that point.)
+   *
+   * @param aTentativeContentBoxMainSize the "tentative" content-box main-size
+   *                                     of the flex container; "tentative"
+   *                                     because it may be unconstrained or may
+   *                                     run off the page.
+   * @param aTentativeContentBoxCrossSize the "tentative" content-box cross-size
+   *                                      of the flex container; "tentative"
+   *                                      because it may be unconstrained or may
+   *                                      run off the page.
+   */
+  struct FlexLayoutResult final {
+    // The flex lines of the flex container.
+    nsTArray<FlexLine> mLines;
+
+    // The absolutely-positioned flex children.
+    nsTArray<nsIFrame*> mPlaceholders;
+
+    bool mHasCollapsedItems = false;
+
+    // The final content-box main-size of the flex container as if there's no
+    // fragmentation.
+    nscoord mContentBoxMainSize = NS_UNCONSTRAINEDSIZE;
+
+    // The final content-box cross-size of the flex container as if there's no
+    // fragmentation.
+    nscoord mContentBoxCrossSize = NS_UNCONSTRAINEDSIZE;
+
+    // The flex container's ascent for the "first baseline" alignment, derived
+    // from any baseline-aligned flex items in the startmost (from the
+    // perspective of the flex container's WM) flex line, if any such items
+    // exist. Otherwise, nscoord_MIN.
+    //
+    // Note: this is a distance from the border-box block-start edge.
+    nscoord mAscent = NS_UNCONSTRAINEDSIZE;
+
+    // The flex container's ascent for the "last baseline" alignment, derived
+    // from any baseline-aligned flex items in the endmost (from the perspective
+    // of the flex container's WM) flex line, if any such items exist.
+    // Otherwise, nscoord_MIN.
+    //
+    // Note: this is a distance from the border-box block-end edge. It's
+    // different from the identically-named-member FlexItem::mAscentForLast,
+    // which is a distance from the item frame's border-box block-start edge.
+    nscoord mAscentForLast = NS_UNCONSTRAINEDSIZE;
+  };
+  FlexLayoutResult DoFlexLayout(
+      const ReflowInput& aReflowInput,
+      const nscoord aTentativeContentBoxMainSize,
+      const nscoord aTentativeContentBoxCrossSize,
+      const FlexboxAxisTracker& aAxisTracker, nscoord aMainGapSize,
+      nscoord aCrossGapSize, nsTArray<StrutInfo>& aStruts,
+      ComputedFlexContainerInfo* const aContainerInfo);
+
+  /**
+   * If our devtools have requested a ComputedFlexContainerInfo for this flex
+   * container, this method ensures that we have one (and if one already exists,
+   * this method reinitializes it to look like a freshly-created one).
+   *
+   * @return the pointer to a freshly created or reinitialized
+   *         ComputedFlexContainerInfo if our devtools have requested it;
+   *         otherwise nullptr.
+   */
+  ComputedFlexContainerInfo* CreateOrClearFlexContainerInfo();
+
+  /**
+   * Helpers for DoFlexLayout to computed fields in ComputedFlexContainerInfo.
+   */
+  static void CreateFlexLineAndFlexItemInfo(
+      ComputedFlexContainerInfo& aContainerInfo,
+      const nsTArray<FlexLine>& aLines);
+
+  static void ComputeFlexDirections(ComputedFlexContainerInfo& aContainerInfo,
+                                    const FlexboxAxisTracker& aAxisTracker);
+
+  static void UpdateFlexLineAndItemInfo(
+      ComputedFlexContainerInfo& aContainerInfo,
+      const nsTArray<FlexLine>& aLines);
+
+  /**
+   * Helper to query flex item's consumed block-size.
+   */
+  static nscoord FlexItemConsumedBSize(const FlexItem& aItem);
+
+#ifdef DEBUG
+  void SanityCheckAnonymousFlexItems() const;
+#endif  // DEBUG
+
+  /**
+   * Construct a new FlexItem for the given child frame, directly at the end of
+   * aLine.
+   *
+   * Before returning, this method also processes the FlexItem to resolve its
+   * flex basis (including e.g. auto-height) as well as to resolve
+   * "min-height:auto", via ResolveAutoFlexBasisAndMinSize(). (Basically, the
+   * constructed FlexItem will be ready to participate in the "Resolve the
+   * Flexible Lengths" step of the Flex Layout Algorithm.)
+   * https://drafts.csswg.org/css-flexbox-1/#algo-flex
+   *
+   * Note that this method **does not** update aLine's main-size bookkeeping to
+   * account for the newly-constructed flex item. The caller is responsible for
+   * determining whether this line is a good fit for the new item. If so, the
+   * caller should update aLine's bookkeeping (via
+   * FlexLine::AddLastItemToMainSizeTotals), or move the new item to a new line.
+   */
+  void GenerateFlexItemForChild(FlexLine& aLine, nsIFrame* aChildFrame,
+                                const ReflowInput& aParentReflowInput,
+                                const FlexboxAxisTracker& aAxisTracker,
+                                const nscoord aTentativeContentBoxCrossSize);
+
+  /**
+   * This method looks up cached block-axis measurements for a flex item, or
+   * does a measuring reflow and caches those measurements.
+   *
+   * This avoids exponential reflows - see the comment above the
+   * CachedBAxisMeasurement struct.
+   */
+  const CachedBAxisMeasurement& MeasureBSizeForFlexItem(
+      FlexItem& aItem, ReflowInput& aChildReflowInput);
+
+  /**
+   * This method performs a "measuring" reflow to get the content BSize of
+   * aFlexItem.Frame() (treating it as if it had a computed BSize of "auto"),
+   * and returns the resulting BSize measurement.
+   * (Helper for ResolveAutoFlexBasisAndMinSize().)
+   */
+  nscoord MeasureFlexItemContentBSize(FlexItem& aFlexItem,
+                                      bool aForceBResizeForMeasuringReflow,
+                                      const ReflowInput& aParentReflowInput);
+
+  /**
+   * This method resolves an "auto" flex-basis and/or min-main-size value
+   * on aFlexItem, if needed.
+   * (Helper for GenerateFlexItemForChild().)
+   */
+  void ResolveAutoFlexBasisAndMinSize(FlexItem& aFlexItem,
+                                      const ReflowInput& aItemReflowInput,
+                                      const FlexboxAxisTracker& aAxisTracker);
+
+  /**
+   * This method:
+   *  - Creates FlexItems for all of our child frames (except placeholders).
+   *  - Groups those FlexItems into FlexLines.
+   *  - Returns those FlexLines in the outparam |aLines|.
+   *
+   * This corresponds to "Collect flex items into flex lines" step in the spec.
+   * https://drafts.csswg.org/css-flexbox-1/#algo-line-break
+   *
+   * For any child frames which are placeholders, this method will instead just
+   * append that child to the outparam |aPlaceholders| for separate handling.
+   * (Absolutely positioned children of a flex container are *not* flex items.)
+   */
+  void 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);
+
+  /**
+   * Generates and returns a FlexLayoutResult that contains the FlexLines and
+   * some sizing metrics that should be used to lay out a particular flex
+   * container continuation (i.e. don't call this on the first-in-flow).
+   */
+  FlexLayoutResult GenerateFlexLayoutResult();
+
+  /**
+   * Resolves the content-box main-size of a flex container frame,
+   * primarily based on:
+   * - the "tentative" main size, taken from the reflow input ("tentative"
+   *   because it may be unconstrained or may run off the page).
+   * - the sizes of our lines of flex items.
+   *
+   * We assume the available block-size is always *unconstrained* because this
+   * is called only in flex algorithm to measure the flex container's size
+   * without regards to pagination.
+   *
+   * Guaranteed to return a definite length, i.e. not NS_UNCONSTRAINEDSIZE,
+   * aside from cases with huge lengths which happen to compute to that value.
+   *
+   * This corresponds to "Determine the main size of the flex container" step in
+   * the spec. https://drafts.csswg.org/css-flexbox-1/#algo-main-container
+   *
+   * (Note: This function should be structurally similar to
+   *  ComputeCrossSize().)
+   */
+  nscoord ComputeMainSize(const ReflowInput& aReflowInput,
+                          const FlexboxAxisTracker& aAxisTracker,
+                          const nscoord aTentativeContentBoxMainSize,
+                          nsTArray<FlexLine>& aLines) const;
+
+  nscoord ComputeCrossSize(const ReflowInput& aReflowInput,
+                           const FlexboxAxisTracker& aAxisTracker,
+                           const nscoord aTentativeContentBoxCrossSize,
+                           nscoord aSumLineCrossSizes, bool* aIsDefinite) const;
+
+  /**
+   * Compute the size of the available space that we'll give to our children to
+   * reflow into. In particular, compute the available size that we would give
+   * to a hypothetical child placed at the IStart/BStart corner of this flex
+   * container's content-box.
+   *
+   * @param aReflowInput the flex container's reflow input.
+   * @param aBorderPadding the border and padding of this frame with the
+   *                       assumption that this is the last fragment.
+   *
+   * @return the size of the available space for our children to reflow into.
+   */
+  mozilla::LogicalSize ComputeAvailableSizeForItems(
+      const ReflowInput& aReflowInput,
+      const mozilla::LogicalMargin& aBorderPadding) const;
+
+  void SizeItemInCrossAxis(ReflowInput& aChildReflowInput, FlexItem& aItem);
+
+  /**
+   * This method computes the metrics to be reported via the flex container's
+   * ReflowOutput & nsReflowStatus output parameters in Reflow().
+   *
+   * @param aContentBoxSize the final content-box size for the flex container as
+   *                        a whole, converted from the flex container's
+   *                        main/cross sizes. The main/cross sizes are computed
+   *                        by DoFlexLayout() if this frame is the
+   *                        first-in-flow, or are the stored ones in
+   *                        SharedFlexData if this frame is a not the
+   *                        first-in-flow.
+   * @param aBorderPadding the border and padding for this frame (possibly with
+   *                       some sides skipped as-appropriate, if we're in a
+   *                       continuation chain).
+   * @param aConsumedBSize the sum of our content-box block-size consumed by our
+   *                       prev-in-flows.
+   * @param aMayNeedNextInFlow true if we may need a next-in-flow because our
+   *                           effective content-box block-size exceeds the
+   *                           available block-size.
+   * @param aMaxBlockEndEdgeOfChildren the maximum block-end edge of the
+   *                                   children of this fragment in this frame's
+   *                                   coordinate space (as returned by
+   *                                   ReflowChildren()).
+   * @param aChildrenStatus the reflow status of children (as returned by
+   *                        ReflowChildren()).
+   * @param aFlr the result returned by DoFlexLayout.
+   *             Note: aFlr is mostly an "input" parameter, but we use
+   *             aFlr.mAscent as an "in/out" parameter; it's initially the
+   *             "tentative" flex container ascent computed in DoFlexLayout; or
+   *             nscoord_MIN if the ascent hasn't been established yet. If the
+   *             latter, this will be updated with an ascent derived from the
+   *             (WM-relative) startmost flex item (if there are any flex
+   *             items). Similar for aFlr.mAscentForLast.
+   */
+  void PopulateReflowOutput(
+      ReflowOutput& aReflowOutput, const ReflowInput& aReflowInput,
+      nsReflowStatus& aStatus, const mozilla::LogicalSize& aContentBoxSize,
+      const mozilla::LogicalMargin& aBorderPadding,
+      const nscoord aConsumedBSize, const bool aMayNeedNextInFlow,
+      const nscoord aMaxBlockEndEdgeOfChildren,
+      const nsReflowStatus& aChildrenStatus,
+      const FlexboxAxisTracker& aAxisTracker, FlexLayoutResult& aFlr);
+
+  /**
+   * Perform a final Reflow for our child frames.
+   *
+   * @param aContainerSize this frame's tentative physical border-box size, used
+   *                       only for logical to physical coordinate conversion.
+   * @param aAvailableSizeForItems the size of the available space for our
+   *                               children to reflow into.
+   * @param aBorderPadding the border and padding for this frame (possibly with
+   *                       some sides skipped as-appropriate, if we're in a
+   *                       continuation chain).
+   * @param aSumOfPrevInFlowsChildrenBlockSize See the comment for
+   *                                           SumOfChildrenBlockSizeProperty.
+   * @param aFlr the result returned by DoFlexLayout.
+   * @param aFragmentData See the comment for PerFragmentFlexData.
+   *                      Note: aFragmentData is an "in/out" parameter. It is
+   *                      initialized by the data stored in our prev-in-flow's
+   *                      PerFragmentFlexData::Prop(); its fields will then be
+   *                      updated and become our PerFragmentFlexData.
+   * @return nscoord the maximum block-end edge of children of this fragment in
+   *                 flex container's coordinate space.
+   * @return nsReflowStatus the reflow status of children (i.e. flex items). If
+   *                        any child had an incomplete reflow status, then this
+   *                        will be Incomplete. Otherwise, if any child had an
+   *                        overflow-incomplete reflow status, this will be
+   *                        OverflowIncomplete.
+   */
+  std::tuple<nscoord, nsReflowStatus> ReflowChildren(
+      const ReflowInput& aReflowInput, const nsSize& aContainerSize,
+      const mozilla::LogicalSize& aAvailableSizeForItems,
+      const mozilla::LogicalMargin& aBorderPadding,
+      const FlexboxAxisTracker& aAxisTracker, FlexLayoutResult& aFlr,
+      PerFragmentFlexData& aFragmentData);
+
+  /**
+   * Moves the given flex item's frame to the given LogicalPosition (modulo any
+   * relative positioning).
+   *
+   * This can be used in cases where we've already done a "measuring reflow"
+   * for the flex item at the correct size, and hence can skip its final reflow
+   * (but still need to move it to the right final position).
+   *
+   * @param aItem           The flex item whose frame should be moved.
+   * @param aFramePos       The position where the flex item's frame should
+   *                        be placed. (pre-relative positioning)
+   * @param aContainerSize  The flex container's size (required by some methods
+   *                        that we call, to interpret aFramePos correctly).
+   */
+  void MoveFlexItemToFinalPosition(const FlexItem& aItem,
+                                   const mozilla::LogicalPoint& aFramePos,
+                                   const nsSize& aContainerSize);
+  /**
+   * Helper-function to reflow a child frame, at its final position determined
+   * by flex layout.
+   *
+   * @param aAxisTracker    A FlexboxAxisTracker with the flex container's axes.
+   * @param aReflowInput    The flex container's reflow input.
+   * @param aItem           The flex item to be reflowed.
+   * @param aFramePos       The position where the flex item's frame should
+   *                        be placed. (pre-relative positioning)
+   * @param aAvailableSize  The available size to reflow the child frame (in the
+   *                        child frame's writing-mode).
+   * @param aContainerSize  The flex container's size (required by some methods
+   *                        that we call, to interpret aFramePos correctly).
+   * @return the child frame's reflow status.
+   */
+  nsReflowStatus ReflowFlexItem(const FlexboxAxisTracker& aAxisTracker,
+                                const ReflowInput& aReflowInput,
+                                const FlexItem& aItem,
+                                const mozilla::LogicalPoint& aFramePos,
+                                const mozilla::LogicalSize& aAvailableSize,
+                                const nsSize& aContainerSize);
+
+  /**
+   * Helper-function to perform a "dummy reflow" on all our nsPlaceholderFrame
+   * children, at the container's content-box origin.
+   *
+   * This doesn't actually represent the static position of the placeholders'
+   * out-of-flow (OOF) frames -- we can't compute that until we've reflowed the
+   * OOF, because (depending on the CSS Align properties) the static position
+   * may be influenced by the OOF's size.  So for now, we just co-opt the
+   * placeholder to store the flex container's logical content-box origin, and
+   * we defer to nsAbsoluteContainingBlock to determine the OOF's actual static
+   * position (using this origin, the OOF's size, and the CSS Align
+   * properties).
+   *
+   * @param aReflowInput       The flex container's reflow input.
+   * @param aPlaceholders      An array of all the flex container's
+   *                           nsPlaceholderFrame children.
+   * @param aContentBoxOrigin  The flex container's logical content-box
+   *                           origin (in its own coordinate space).
+   * @param aContainerSize     The flex container's size (required by some
+   *                           reflow methods to interpret positions correctly).
+   */
+  void ReflowPlaceholders(const ReflowInput& aReflowInput,
+                          nsTArray<nsIFrame*>& aPlaceholders,
+                          const mozilla::LogicalPoint& aContentBoxOrigin,
+                          const nsSize& aContainerSize);
+
+  /**
+   * Helper for GetMinISize / GetPrefISize.
+   */
+  nscoord IntrinsicISize(gfxContext* aRenderingContext,
+                         mozilla::IntrinsicISizeType aType);
+
+  /**
+   * Cached values to optimize GetMinISize/GetPrefISize.
+   */
+  nscoord mCachedMinISize = NS_INTRINSIC_ISIZE_UNKNOWN;
+  nscoord mCachedPrefISize = NS_INTRINSIC_ISIZE_UNKNOWN;
+
+  /**
+   * Cached baselines computed in our last reflow to optimize
+   * GetNaturalBaselineBOffset().
+   */
+  // Note: the first baseline is a distance from our border-box block-start
+  // edge.
+  nscoord mFirstBaseline = NS_INTRINSIC_ISIZE_UNKNOWN;
+  // Note: the last baseline is a distance from our border-box block-end edge.
+  nscoord mLastBaseline = NS_INTRINSIC_ISIZE_UNKNOWN;
+};
+
+#endif /* nsFlexContainerFrame_h___ */