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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/. */
+
+/* class that manages rules for positioning floats */
+
+#ifndef nsFloatManager_h_
+#define nsFloatManager_h_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/TypedEnumBits.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WritingModes.h"
+#include "nsCoord.h"
+#include "nsFrameList.h" // for DEBUG_FRAME_DUMP
+#include "nsIntervalSet.h"
+#include "nsPoint.h"
+#include "nsTArray.h"
+
+class nsIFrame;
+class nsPresContext;
+namespace mozilla {
+struct ReflowInput;
+class PresShell;
+} // namespace mozilla
+
+enum class nsFlowAreaRectFlags : uint32_t {
+ NoFlags = 0,
+ HasFloats = 1 << 0,
+ MayWiden = 1 << 1,
+ ISizeIsActuallyNegative = 1 << 2,
+};
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(nsFlowAreaRectFlags)
+
+/**
+ * The available space for content not occupied by floats is divided
+ * into a sequence of rectangles in the block direction. However, we
+ * need to know not only the rectangle, but also whether it was reduced
+ * (from the content rectangle) by floats that actually intruded into
+ * the content rectangle. If it has been reduced by floats, then we also
+ * track whether the flow area might widen as the floats narrow in the
+ * block direction.
+ */
+struct nsFlowAreaRect {
+ mozilla::LogicalRect mRect;
+
+ nsFlowAreaRectFlags mAreaFlags;
+
+ nsFlowAreaRect(mozilla::WritingMode aWritingMode, nscoord aICoord,
+ nscoord aBCoord, nscoord aISize, nscoord aBSize,
+ nsFlowAreaRectFlags aAreaFlags)
+ : mRect(aWritingMode, aICoord, aBCoord, aISize, aBSize),
+ mAreaFlags(aAreaFlags) {}
+
+ bool HasFloats() const {
+ return (bool)(mAreaFlags & nsFlowAreaRectFlags::HasFloats);
+ }
+ bool MayWiden() const {
+ return (bool)(mAreaFlags & nsFlowAreaRectFlags::MayWiden);
+ }
+ bool ISizeIsActuallyNegative() const {
+ return (bool)(mAreaFlags & nsFlowAreaRectFlags::ISizeIsActuallyNegative);
+ }
+};
+
+#define NS_FLOAT_MANAGER_CACHE_SIZE 64
+
+/**
+ * nsFloatManager is responsible for implementing CSS's rules for
+ * positioning floats. An nsFloatManager object is created during reflow for
+ * any block with NS_BLOCK_BFC_STATE_BITS. During reflow, the float manager for
+ * the nearest such ancestor block is found in ReflowInput::mFloatManager.
+ *
+ * According to the line-relative mappings in CSS Writing Modes spec [1],
+ * line-right and line-left are calculated with respect to the writing mode
+ * of the containing block of the floats. All the writing modes passed to
+ * nsFloatManager methods should be the containing block's writing mode.
+ *
+ * However, according to the abstract-to-physical mappings table [2], the
+ * 'direction' property of the containing block doesn't affect the
+ * interpretation of line-right and line-left. We actually implement this by
+ * passing in the writing mode of the block formatting context (BFC), i.e.
+ * the of BlockReflowState's writing mode.
+ *
+ * nsFloatManager uses a special logical coordinate space with inline
+ * coordinates on the line-axis and block coordinates on the block-axis
+ * based on the writing mode of the block formatting context. All the
+ * physical types like nsRect, nsPoint, etc. use this coordinate space. See
+ * FloatInfo::mRect for an example.
+ *
+ * [1] https://drafts.csswg.org/css-writing-modes/#line-mappings
+ * [2] https://drafts.csswg.org/css-writing-modes/#logical-to-physical
+ */
+class nsFloatManager {
+ public:
+ explicit nsFloatManager(mozilla::PresShell* aPresShell,
+ mozilla::WritingMode aWM);
+ ~nsFloatManager();
+
+ void* operator new(size_t aSize) noexcept(true);
+ void operator delete(void* aPtr, size_t aSize);
+
+ static void Shutdown();
+
+ /**
+ * Get float region stored on the frame. (Defaults to mRect if it's
+ * not there.) The float region is the area impacted by this float;
+ * the coordinates are relative to the containing block frame.
+ */
+ static mozilla::LogicalRect GetRegionFor(mozilla::WritingMode aWM,
+ nsIFrame* aFloatFrame,
+ const nsSize& aContainerSize);
+ /**
+ * Calculate the float region for this frame using aMargin and the
+ * frame's mRect. The region includes the margins around the float,
+ * but doesn't include the relative offsets.
+ * Note that if the frame is or has a continuation, aMargin's top
+ * and/or bottom must be zeroed by the caller.
+ */
+ static mozilla::LogicalRect CalculateRegionFor(
+ mozilla::WritingMode aWM, nsIFrame* aFloatFrame,
+ const mozilla::LogicalMargin& aMargin, const nsSize& aContainerSize);
+ /**
+ * Store the float region on the frame. The region is stored
+ * as a delta against the mRect, so repositioning the frame will
+ * also reposition the float region.
+ */
+ static void StoreRegionFor(mozilla::WritingMode aWM, nsIFrame* aFloat,
+ const mozilla::LogicalRect& aRegion,
+ const nsSize& aContainerSize);
+
+ // Structure that stores the current state of a float manager for
+ // Save/Restore purposes.
+ struct SavedState {
+ explicit SavedState()
+ : mFloatInfoCount(0),
+ mLineLeft(0),
+ mBlockStart(0),
+ mPushedLeftFloatPastBreak(false),
+ mPushedRightFloatPastBreak(false),
+ mSplitLeftFloatAcrossBreak(false),
+ mSplitRightFloatAcrossBreak(false) {}
+
+ private:
+ uint32_t mFloatInfoCount;
+ nscoord mLineLeft, mBlockStart;
+ bool mPushedLeftFloatPastBreak;
+ bool mPushedRightFloatPastBreak;
+ bool mSplitLeftFloatAcrossBreak;
+ bool mSplitRightFloatAcrossBreak;
+
+ friend class nsFloatManager;
+ };
+
+ /**
+ * Translate the current origin by the specified offsets. This
+ * creates a new local coordinate space relative to the current
+ * coordinate space.
+ */
+ void Translate(nscoord aLineLeft, nscoord aBlockStart) {
+ mLineLeft += aLineLeft;
+ mBlockStart += aBlockStart;
+ }
+
+ /**
+ * Returns the current translation from local coordinate space to
+ * world coordinate space. This represents the accumulated calls to
+ * Translate().
+ */
+ void GetTranslation(nscoord& aLineLeft, nscoord& aBlockStart) const {
+ aLineLeft = mLineLeft;
+ aBlockStart = mBlockStart;
+ }
+
+ /**
+ * Get information about the area available to content that flows
+ * around floats. Two different types of space can be requested:
+ * BandFromPoint: returns the band containing block-dir coordinate
+ * |aBCoord| (though actually with the top truncated to begin at
+ * aBCoord), but up to at most |aBSize| (which may be nscoord_MAX).
+ * This will return the tallest rectangle whose block start is
+ * |aBCoord| and in which there are no changes in what floats are
+ * on the sides of that rectangle, but will limit the block size
+ * of the rectangle to |aBSize|. The inline start and end edges
+ * of the rectangle give the area available for line boxes in that
+ * space. The inline size of this resulting rectangle will not be
+ * negative.
+ * WidthWithinHeight: This returns a rectangle whose block start
+ * is aBCoord and whose block size is exactly aBSize. Its inline
+ * start and end edges give the corresponding edges of the space
+ * that can be used for line boxes *throughout* that space. (It
+ * is possible that more inline space could be used in part of the
+ * space if a float begins or ends in it.) The inline size of the
+ * resulting rectangle can be negative.
+ *
+ * ShapeType can be used to request two different types of flow areas.
+ * (This is the float area defined in CSS Shapes Module Level 1 ยง1.4):
+ * Margin: uses the float element's margin-box to request the flow area.
+ * ShapeOutside: uses the float element's shape-outside value to request
+ * the float area.
+ *
+ * @param aBCoord [in] block-dir coordinate for block start of available space
+ * desired, which are positioned relative to the current translation.
+ * @param aBSize [in] see above
+ * @param aContentArea [in] an nsRect representing the content area
+ * @param aState [in] If null, use the current state, otherwise, do
+ * computation based only on floats present in the given
+ * saved state.
+ * @return An nsFlowAreaRect whose:
+ * mRect is the resulting rectangle for line boxes. It will not
+ * extend beyond aContentArea's inline bounds, but may be
+ * narrower when floats are present.
+ * mHasFloats is whether there are floats at the sides of the
+ * return value including those that do not reduce the line box
+ * inline size at all (because they are entirely in the margins)
+ */
+ enum class BandInfoType { BandFromPoint, WidthWithinHeight };
+ enum class ShapeType { Margin, ShapeOutside };
+ nsFlowAreaRect GetFlowArea(mozilla::WritingMode aWM, nscoord aBCoord,
+ nscoord aBSize, BandInfoType aBandInfoType,
+ ShapeType aShapeType,
+ mozilla::LogicalRect aContentArea,
+ SavedState* aState,
+ const nsSize& aContainerSize) const;
+
+ /**
+ * Add a float that comes after all floats previously added. Its
+ * block start must be even with or below the top of all previous
+ * floats.
+ *
+ * aMarginRect is relative to the current translation. The caller
+ * must ensure aMarginRect.height >= 0 and aMarginRect.width >= 0.
+ */
+ void AddFloat(nsIFrame* aFloatFrame, const mozilla::LogicalRect& aMarginRect,
+ mozilla::WritingMode aWM, const nsSize& aContainerSize);
+
+ /**
+ * Notify that we tried to place a float that could not fit at all and
+ * had to be pushed to the next page/column? (If so, we can't place
+ * any more floats in this page/column because of the rule that the
+ * top of a float cannot be above the top of an earlier float. It
+ * also means that any clear needs to continue to the next column.)
+ */
+ void SetPushedLeftFloatPastBreak() { mPushedLeftFloatPastBreak = true; }
+ void SetPushedRightFloatPastBreak() { mPushedRightFloatPastBreak = true; }
+
+ /**
+ * Notify that we split a float, with part of it needing to be pushed
+ * to the next page/column. (This means that any 'clear' needs to
+ * continue to the next page/column.)
+ */
+ void SetSplitLeftFloatAcrossBreak() { mSplitLeftFloatAcrossBreak = true; }
+ void SetSplitRightFloatAcrossBreak() { mSplitRightFloatAcrossBreak = true; }
+
+ /**
+ * Remove the regions associated with this floating frame and its
+ * next-sibling list. Some of the frames may never have been added;
+ * we just skip those. This is not fully general; it only works as
+ * long as the N frames to be removed are the last N frames to have
+ * been added; if there's a frame in the middle of them that should
+ * not be removed, YOU LOSE.
+ */
+ nsresult RemoveTrailingRegions(nsIFrame* aFrameList);
+
+ bool HasAnyFloats() const { return !mFloats.IsEmpty(); }
+
+ /**
+ * Methods for dealing with the propagation of float damage during
+ * reflow.
+ */
+ bool HasFloatDamage() const { return !mFloatDamage.IsEmpty(); }
+
+ void IncludeInDamage(nscoord aIntervalBegin, nscoord aIntervalEnd) {
+ mFloatDamage.IncludeInterval(aIntervalBegin + mBlockStart,
+ aIntervalEnd + mBlockStart);
+ }
+
+ bool IntersectsDamage(nscoord aIntervalBegin, nscoord aIntervalEnd) const {
+ return mFloatDamage.Intersects(aIntervalBegin + mBlockStart,
+ aIntervalEnd + mBlockStart);
+ }
+
+ /**
+ * Saves the current state of the float manager into aState.
+ */
+ void PushState(SavedState* aState);
+
+ /**
+ * Restores the float manager to the saved state.
+ *
+ * These states must be managed using stack discipline. PopState can only
+ * be used after PushState has been used to save the state, and it can only
+ * be used once --- although it can be omitted; saved states can be ignored.
+ * States must be popped in the reverse order they were pushed. A
+ * call to PopState invalidates any saved states Pushed after the
+ * state passed to PopState was pushed.
+ */
+ void PopState(SavedState* aState);
+
+ /**
+ * Get the block start of the last float placed into the float
+ * manager, to enforce the rule that a float can't be above an earlier
+ * float. Returns the minimum nscoord value if there are no floats.
+ *
+ * The result is relative to the current translation.
+ */
+ nscoord LowestFloatBStart() const;
+
+ /**
+ * Return the coordinate of the lowest float matching aClearType in
+ * this float manager. Returns aBCoord if there are no matching
+ * floats.
+ *
+ * Both aBCoord and the result are relative to the current translation.
+ */
+ nscoord ClearFloats(nscoord aBCoord, mozilla::StyleClear aClearType) const;
+
+ /**
+ * Checks if clear would pass into the floats' BFC's next-in-flow,
+ * i.e. whether floats affecting this clear have continuations.
+ */
+ bool ClearContinues(mozilla::StyleClear aClearType) const;
+
+ void AssertStateMatches(SavedState* aState) const {
+ NS_ASSERTION(
+ aState->mLineLeft == mLineLeft && aState->mBlockStart == mBlockStart &&
+ aState->mPushedLeftFloatPastBreak == mPushedLeftFloatPastBreak &&
+ aState->mPushedRightFloatPastBreak == mPushedRightFloatPastBreak &&
+ aState->mSplitLeftFloatAcrossBreak == mSplitLeftFloatAcrossBreak &&
+ aState->mSplitRightFloatAcrossBreak ==
+ mSplitRightFloatAcrossBreak &&
+ aState->mFloatInfoCount == mFloats.Length(),
+ "float manager state should match saved state");
+ }
+
+#ifdef DEBUG_FRAME_DUMP
+ /**
+ * Dump the state of the float manager out to a file.
+ */
+ nsresult List(FILE* out) const;
+#endif
+
+ private:
+ class ShapeInfo;
+ class RoundedBoxShapeInfo;
+ class EllipseShapeInfo;
+ class PolygonShapeInfo;
+ class ImageShapeInfo;
+
+ struct FloatInfo {
+ nsIFrame* const mFrame;
+ // The lowest block-ends of left/right floats up to and including
+ // this one.
+ nscoord mLeftBEnd, mRightBEnd;
+
+ FloatInfo(nsIFrame* aFrame, nscoord aLineLeft, nscoord aBlockStart,
+ const mozilla::LogicalRect& aMarginRect, mozilla::WritingMode aWM,
+ const nsSize& aContainerSize);
+
+ nscoord LineLeft() const { return mRect.x; }
+ nscoord LineRight() const { return mRect.XMost(); }
+ nscoord ISize() const { return mRect.width; }
+ nscoord BStart() const { return mRect.y; }
+ nscoord BEnd() const { return mRect.YMost(); }
+ nscoord BSize() const { return mRect.height; }
+ bool IsEmpty() const { return mRect.IsEmpty(); }
+
+ // aBStart and aBEnd are the starting and ending coordinate of a band.
+ // LineLeft() and LineRight() return the innermost line-left extent and
+ // line-right extent within the given band, respectively.
+ nscoord LineLeft(ShapeType aShapeType, const nscoord aBStart,
+ const nscoord aBEnd) const;
+ nscoord LineRight(ShapeType aShapeType, const nscoord aBStart,
+ const nscoord aBEnd) const;
+ nscoord BStart(ShapeType aShapeType) const;
+ nscoord BEnd(ShapeType aShapeType) const;
+ bool IsEmpty(ShapeType aShapeType) const;
+ bool MayNarrowInBlockDirection(ShapeType aShapeType) const;
+
+#ifdef NS_BUILD_REFCNT_LOGGING
+ FloatInfo(FloatInfo&& aOther);
+ ~FloatInfo();
+#endif
+
+ // NB! This is really a logical rect in a writing mode suitable for
+ // placing floats, which is not necessarily the actual writing mode
+ // either of the block which created the float manager or the block
+ // that is calling the float manager. The inline coordinates are in
+ // the line-relative axis of the float manager and its block
+ // coordinates are in the float manager's block direction.
+ nsRect mRect;
+ // Pointer to a concrete subclass of ShapeInfo or null, which means that
+ // there is no shape-outside.
+ mozilla::UniquePtr<ShapeInfo> mShapeInfo;
+ };
+
+#ifdef DEBUG
+ // Store the writing mode from the block frame which establishes the block
+ // formatting context (BFC) when the nsFloatManager is created.
+ mozilla::WritingMode mWritingMode;
+#endif
+
+ // Translation from local to global coordinate space.
+ nscoord mLineLeft, mBlockStart;
+ // We use 11 here in order to fill up the jemalloc allocatoed chunk nicely,
+ // see https://bugzilla.mozilla.org/show_bug.cgi?id=1362876#c6.
+ AutoTArray<FloatInfo, 11> mFloats;
+ nsIntervalSet mFloatDamage;
+
+ // Did we try to place a float that could not fit at all and had to be
+ // pushed to the next page/column? If so, we can't place any more
+ // floats in this page/column because of the rule that the top of a
+ // float cannot be above the top of an earlier float. And we also
+ // need to apply this information to 'clear', and thus need to
+ // separate left and right floats.
+ bool mPushedLeftFloatPastBreak;
+ bool mPushedRightFloatPastBreak;
+
+ // Did we split a float, with part of it needing to be pushed to the
+ // next page/column. This means that any 'clear' needs to continue to
+ // the next page/column.
+ bool mSplitLeftFloatAcrossBreak;
+ bool mSplitRightFloatAcrossBreak;
+
+ static int32_t sCachedFloatManagerCount;
+ static void* sCachedFloatManagers[NS_FLOAT_MANAGER_CACHE_SIZE];
+
+ nsFloatManager(const nsFloatManager&) = delete;
+ void operator=(const nsFloatManager&) = delete;
+};
+
+/**
+ * A helper class to manage maintenance of the float manager during
+ * nsBlockFrame::Reflow. It automatically restores the old float
+ * manager in the reflow input when the object goes out of scope.
+ */
+class nsAutoFloatManager {
+ using ReflowInput = mozilla::ReflowInput;
+
+ public:
+ explicit nsAutoFloatManager(ReflowInput& aReflowInput)
+ : mReflowInput(aReflowInput), mOld(nullptr) {}
+
+ ~nsAutoFloatManager();
+
+ /**
+ * Create a new float manager for the specified frame. This will
+ * `remember' the old float manager, and install the new float
+ * manager in the reflow input.
+ */
+ void CreateFloatManager(nsPresContext* aPresContext);
+
+ protected:
+ ReflowInput& mReflowInput;
+ mozilla::UniquePtr<nsFloatManager> mNew;
+
+ // A non-owning pointer, which points to the object owned by
+ // nsAutoFloatManager::mNew.
+ nsFloatManager* mOld;
+};
+
+#endif /* !defined(nsFloatManager_h_) */