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Diffstat (limited to 'layout/generic/nsFloatManager.h')
| -rw-r--r-- | layout/generic/nsFloatManager.h | 464 |
1 files changed, 464 insertions, 0 deletions
diff --git a/layout/generic/nsFloatManager.h b/layout/generic/nsFloatManager.h new file mode 100644 index 0000000000..f947567383 --- /dev/null +++ b/layout/generic/nsFloatManager.h @@ -0,0 +1,464 @@ +/* -*- 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_) */ |