diff -r 000000000000 -r 6474c204b198 layout/generic/nsFloatManager.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/layout/generic/nsFloatManager.h Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,349 @@ +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +// vim:cindent:ts=2:et:sw=2: +/* 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 "nsIntervalSet.h" +#include "nsCoord.h" +#include "nsRect.h" +#include "nsTArray.h" +#include "nsFrameList.h" // for DEBUG_FRAME_DUMP + +class nsIPresShell; +class nsIFrame; +struct nsHTMLReflowState; +class nsPresContext; + +/** + * The available space for content not occupied by floats is divided + * into a (vertical) sequence of rectangles. 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. + */ +struct nsFlowAreaRect { + nsRect mRect; + bool mHasFloats; + + nsFlowAreaRect(nscoord aX, nscoord aY, nscoord aWidth, nscoord aHeight, + bool aHasFloats) + : mRect(aX, aY, aWidth, aHeight), mHasFloats(aHasFloats) {} +}; + +#define NS_FLOAT_MANAGER_CACHE_SIZE 4 + +class nsFloatManager { +public: + nsFloatManager(nsIPresShell* aPresShell); + ~nsFloatManager(); + + void* operator new(size_t aSize) CPP_THROW_NEW; + 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 nsRect GetRegionFor(nsIFrame* aFloatFrame); + /** + * 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 nsRect CalculateRegionFor(nsIFrame* aFloatFrame, + const nsMargin& aMargin); + /** + * 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(nsIFrame* aFloat, nsRect& aRegion); + + // Structure that stores the current state of a frame manager for + // Save/Restore purposes. + struct SavedState; + friend struct SavedState; + struct SavedState { + private: + uint32_t mFloatInfoCount; + nscoord mX, mY; + bool mPushedLeftFloatPastBreak; + bool mPushedRightFloatPastBreak; + bool mSplitLeftFloatAcrossBreak; + bool mSplitRightFloatAcrossBreak; + + friend class nsFloatManager; + }; + + /** + * Translate the current origin by the specified (dx, dy). This + * creates a new local coordinate space relative to the current + * coordinate space. + */ + void Translate(nscoord aDx, nscoord aDy) { mX += aDx; mY += aDy; } + + /** + * Returns the current translation from local coordinate space to + * world coordinate space. This represents the accumulated calls to + * Translate(). + */ + void GetTranslation(nscoord& aX, nscoord& aY) const { aX = mX; aY = mY; } + + /** + * Get information about the area available to content that flows + * around floats. Two different types of space can be requested: + * BAND_FROM_POINT: returns the band containing vertical coordinate + * |aY| (though actually with the top truncated to begin at aY), + * but up to at most |aHeight| (which may be nscoord_MAX). + * This will return the tallest rectangle whose top is |aY| and in + * which there are no changes in what floats are on the sides of + * that rectangle, but will limit the height of the rectangle to + * |aHeight|. The left and right edges of the rectangle give the + * area available for line boxes in that space. The width of this + * resulting rectangle will not be negative. + * WIDTH_WITHIN_HEIGHT: This returns a rectangle whose top is aY and + * whose height is exactly aHeight. Its left and right edges give + * the left and right edges of the space that can be used for line + * boxes *throughout* that space. (It is possible that more + * horizontal space could be used in part of the space if a float + * begins or ends in it.) The width of the resulting rectangle + * can be negative. + * + * @param aY [in] vertical coordinate for top of available space + * desired + * @param aHeight [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 horizontal bounds, but may be + * narrower when floats are present. + * mBandHasFloats is whether there are floats at the sides of the + * return value including those that do not reduce the line box + * width at all (because they are entirely in the margins) + * + * aY and aAvailSpace are positioned relative to the current translation + */ + enum BandInfoType { BAND_FROM_POINT, WIDTH_WITHIN_HEIGHT }; + nsFlowAreaRect GetFlowArea(nscoord aY, BandInfoType aInfoType, + nscoord aHeight, nsRect aContentArea, + SavedState* aState) const; + + /** + * Add a float that comes after all floats previously added. Its top + * 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. + */ + nsresult AddFloat(nsIFrame* aFloatFrame, const nsRect& aMarginRect); + + /** + * 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); + +private: + struct FloatInfo; +public: + + 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 + mY, aIntervalEnd + mY); + } + + bool IntersectsDamage(nscoord aIntervalBegin, nscoord aIntervalEnd) const + { + return mFloatDamage.Intersects(aIntervalBegin + mY, aIntervalEnd + mY); + } + + /** + * 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 top 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 aY if there are no matching floats. + * + * Both aY and the result are relative to the current translation. + */ + enum { + // Tell ClearFloats not to push to nscoord_MAX when floats have been + // pushed to the next page/column. + DONT_CLEAR_PUSHED_FLOATS = (1<<0) + }; + nscoord ClearFloats(nscoord aY, uint8_t aBreakType, uint32_t aFlags = 0) 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(uint8_t aBreakType) const; + + void AssertStateMatches(SavedState *aState) const + { + NS_ASSERTION(aState->mX == mX && aState->mY == mY && + 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: + + struct FloatInfo { + nsIFrame *const mFrame; + nsRect mRect; + // The lowest bottoms of left/right floats up to and including this one. + nscoord mLeftYMost, mRightYMost; + + FloatInfo(nsIFrame* aFrame, const nsRect& aRect); +#ifdef NS_BUILD_REFCNT_LOGGING + FloatInfo(const FloatInfo& aOther); + ~FloatInfo(); +#endif + }; + + nscoord mX, mY; // translation from local to global coordinate space + nsTArray 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&) MOZ_DELETE; + void operator=(const nsFloatManager&) MOZ_DELETE; +}; + +/** + * A helper class to manage maintenance of the float manager during + * nsBlockFrame::Reflow. It automatically restores the old float + * manager in the reflow state when the object goes out of scope. + */ +class nsAutoFloatManager { +public: + nsAutoFloatManager(nsHTMLReflowState& aReflowState) + : mReflowState(aReflowState), + mNew(nullptr), + 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 state. + */ + nsresult + CreateFloatManager(nsPresContext *aPresContext); + +protected: + nsHTMLReflowState &mReflowState; + nsFloatManager *mNew; + nsFloatManager *mOld; +}; + +#endif /* !defined(nsFloatManager_h_) */