/* -*- 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 }; 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); } }; #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_FLOAT_MGR. 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 BlockReflowInput'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 GetLowestFloatTop() const; /** * Return the coordinate of the lowest float matching aBreakType 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 aBreakType) 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 aBreakType) 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 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 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 mNew; // A non-owning pointer, which points to the object owned by // nsAutoFloatManager::mNew. nsFloatManager* mOld; }; #endif /* !defined(nsFloatManager_h_) */