nsBlockReflowState.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 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/. */

/* state used in reflow of block frames */

#ifndef nsBlockReflowState_h__
#define nsBlockReflowState_h__

#include "nsFloatManager.h"
#include "nsLineBox.h"
#include "nsHTMLReflowState.h"

class nsBlockFrame;
class nsFrameList;
class nsOverflowContinuationTracker;

  // block reflow state flags
#define BRS_UNCONSTRAINEDBSIZE    0x00000001
#define BRS_ISBSTARTMARGINROOT    0x00000002  // Is this frame a root for block
#define BRS_ISBENDMARGINROOT      0x00000004  //  direction start/end margin collapsing?
#define BRS_APPLYBSTARTMARGIN     0x00000008  // See ShouldApplyTopMargin
#define BRS_ISFIRSTINFLOW         0x00000010
// Set when mLineAdjacentToTop is valid
#define BRS_HAVELINEADJACENTTOTOP 0x00000020
// Set when the block has the equivalent of NS_BLOCK_FLOAT_MGR
#define BRS_FLOAT_MGR             0x00000040
// Set when nsLineLayout::LineIsEmpty was true at the end of reflowing
// the current line
#define BRS_LINE_LAYOUT_EMPTY     0x00000080
#define BRS_ISOVERFLOWCONTAINER   0x00000100
// Our mPushedFloats list is stored on the blocks' proptable
#define BRS_PROPTABLE_FLOATCLIST  0x00000200
// Set when the pref layout.float-fragments-inside-column.enabled is true.
#define BRS_FLOAT_FRAGMENTS_INSIDE_COLUMN_ENABLED 0x00000400
#define BRS_LASTFLAG              BRS_FLOAT_FRAGMENTS_INSIDE_COLUMN_ENABLED

class nsBlockReflowState {
public:
  nsBlockReflowState(const nsHTMLReflowState& aReflowState,
                     nsPresContext* aPresContext,
                     nsBlockFrame* aFrame,
                     bool aBStartMarginRoot, bool aBEndMarginRoot,
                     bool aBlockNeedsFloatManager,
                     nscoord aConsumedBSize = NS_INTRINSICSIZE);

  /**
   * Get the available reflow space (the area not occupied by floats)
   * for the current y coordinate. The available space is relative to
   * our coordinate system, which is the content box, with (0, 0) in the
   * upper left.
   *
   * Returns whether there are floats present at the given block-direction
   * coordinate and within the inline size of the content rect.
   */
  nsFlowAreaRect GetFloatAvailableSpace() const
    { return GetFloatAvailableSpace(mBCoord); }
  nsFlowAreaRect GetFloatAvailableSpace(nscoord aBCoord) const
    { return GetFloatAvailableSpaceWithState(aBCoord, nullptr); }
  nsFlowAreaRect
    GetFloatAvailableSpaceWithState(nscoord aBCoord,
                                    nsFloatManager::SavedState *aState) const;
  nsFlowAreaRect
    GetFloatAvailableSpaceForBSize(nscoord aBCoord, nscoord aBSize,
                                   nsFloatManager::SavedState *aState) const;

  /*
   * The following functions all return true if they were able to
   * place the float, false if the float did not fit in available
   * space.
   * aLineLayout is null when we are reflowing pushed floats (because
   * they are not associated with a line box).
   */
  bool AddFloat(nsLineLayout*       aLineLayout,
                nsIFrame*           aFloat,
                nscoord             aAvailableISize);
private:
  bool CanPlaceFloat(nscoord aFloatISize,
                     const nsFlowAreaRect& aFloatAvailableSpace);
public:
  bool FlowAndPlaceFloat(nsIFrame* aFloat);
private:
  void PushFloatPastBreak(nsIFrame* aFloat);
public:
  void PlaceBelowCurrentLineFloats(nsFloatCacheFreeList& aFloats,
                                   nsLineBox* aLine);

  // Returns the first coordinate >= aBCoord that clears the
  // floats indicated by aBreakType and has enough inline size between floats
  // (or no floats remaining) to accomodate aReplacedBlock.
  nscoord ClearFloats(nscoord aBCoord, uint8_t aBreakType,
                      nsIFrame *aReplacedBlock = nullptr,
                      uint32_t aFlags = 0);

  // Advances to the next band, i.e., the next horizontal stripe in
  // which there is a different set of floats.
  // Return false if it did not advance, which only happens for
  // constrained heights (and means that we should get pushed to the
  // next column/page).
  bool AdvanceToNextBand(const mozilla::LogicalRect& aFloatAvailableSpace,
                         nscoord *aBCoord) const {
    mozilla::WritingMode wm = mReflowState.GetWritingMode();
    if (aFloatAvailableSpace.BSize(wm) > 0) {
      // See if there's room in the next band.
      *aBCoord += aFloatAvailableSpace.BSize(wm);
    } else {
      if (mReflowState.AvailableHeight() != NS_UNCONSTRAINEDSIZE) {
        // Stop trying to clear here; we'll just get pushed to the
        // next column or page and try again there.
        return false;
      }
      NS_NOTREACHED("avail space rect with zero height!");
      *aBCoord += 1;
    }
    return true;
  }

  bool ReplacedBlockFitsInAvailSpace(nsIFrame* aReplacedBlock,
                            const nsFlowAreaRect& aFloatAvailableSpace) const;

  bool IsAdjacentWithTop() const {
    return mBCoord == mBorderPadding.BStart(mReflowState.GetWritingMode());
  }

  /**
   * Return mBlock's computed physical border+padding with GetSkipSides applied.
   */
  const mozilla::LogicalMargin& BorderPadding() const {
    return mBorderPadding;
  }

  /**
   * Retrieve the block-direction size "consumed" by any previous-in-flows.
   */
  nscoord GetConsumedBSize();

  // Reconstruct the previous block-end margin that goes before |aLine|.
  void ReconstructMarginBefore(nsLineList::iterator aLine);

  // Caller must have called GetAvailableSpace for the correct position
  // (which need not be the current mBCoord).
  void ComputeReplacedBlockOffsetsForFloats(nsIFrame* aFrame,
                          const mozilla::LogicalRect& aFloatAvailableSpace,
                                            nscoord&  aIStartResult,
                                            nscoord&  aIEndResult) const;

  // Caller must have called GetAvailableSpace for the current mBCoord
  void ComputeBlockAvailSpace(nsIFrame* aFrame,
                              const nsStyleDisplay* aDisplay,
                              const nsFlowAreaRect& aFloatAvailableSpace,
                              bool aBlockAvoidsFloats,
                              mozilla::LogicalRect& aResult);

protected:
  void RecoverFloats(nsLineList::iterator aLine, nscoord aDeltaBCoord);

public:
  void RecoverStateFrom(nsLineList::iterator aLine, nscoord aDeltaBCoord);

  void AdvanceToNextLine() {
    if (GetFlag(BRS_LINE_LAYOUT_EMPTY)) {
      SetFlag(BRS_LINE_LAYOUT_EMPTY, false);
    } else {
      mLineNumber++;
    }
  }

  //----------------------------------------

  // This state is the "global" state computed once for the reflow of
  // the block.

  // The block frame that is using this object
  nsBlockFrame* mBlock;

  nsPresContext* mPresContext;

  const nsHTMLReflowState& mReflowState;

  nsFloatManager* mFloatManager;

  // The coordinates within the float manager where the block is being
  // placed <b>after</b> taking into account the blocks border and
  // padding. This, therefore, represents the inner "content area" (in
  // spacemanager coordinates) where child frames will be placed,
  // including child blocks and floats.
  nscoord mFloatManagerI, mFloatManagerB;

  // XXX get rid of this
  nsReflowStatus mReflowStatus;

  // The float manager state as it was before the contents of this
  // block.  This is needed for positioning bullets, since we only want
  // to move the bullet to flow around floats that were before this
  // block, not floats inside of it.
  nsFloatManager::SavedState mFloatManagerStateBefore;

  nscoord mBEndEdge;

  // The content area to reflow child frames within.  This is within
  // this frame's coordinate system and writing mode, which means
  // mContentArea.IStart == BorderPadding().IStart and
  // mContentArea.BStart == BorderPadding().BStart.
  // The block size may be NS_UNCONSTRAINEDSIZE, which indicates that there
  // is no page/column boundary below (the common case).
  // mContentArea.BEnd() should only be called after checking that
  // mContentArea.BSize is not NS_UNCONSTRAINEDSIZE; otherwise
  // coordinate overflow may occur.
  mozilla::LogicalRect mContentArea;
  nscoord ContentIStart() const {
    return mContentArea.IStart(mReflowState.GetWritingMode());
  }
  nscoord ContentISize() const {
    return mContentArea.ISize(mReflowState.GetWritingMode());
  }
  nscoord ContentIEnd() const {
    return mContentArea.IEnd(mReflowState.GetWritingMode());
  }
  nscoord ContentBStart() const {
    return mContentArea.BStart(mReflowState.GetWritingMode());
  }
  nscoord ContentBSize() const {
    return mContentArea.BSize(mReflowState.GetWritingMode());
  }
  nscoord ContentBEnd() const {
    return mContentArea.BEnd(mReflowState.GetWritingMode());
  }
  mozilla::LogicalSize ContentSize(mozilla::WritingMode aWM) const {
    mozilla::WritingMode wm = mReflowState.GetWritingMode();
    return mContentArea.Size(wm).ConvertTo(aWM, wm);
  }

  // Physical size. Use only for physical <-> logical coordinate conversion.
  nsSize mContainerSize;
  const nsSize& ContainerSize() const { return mContainerSize; }

  // Continuation out-of-flow float frames that need to move to our
  // next in flow are placed here during reflow.  It's a pointer to
  // a frame list stored in the block's property table.
  nsFrameList *mPushedFloats;
  // This method makes sure pushed floats are accessible to
  // StealFrame. Call it before adding any frames to mPushedFloats.
  void SetupPushedFloatList();
  /**
   * Append aFloatCont and its next-in-flows within the same block to
   * mPushedFloats.  aFloatCont should not be on any child list when
   * making this call.  Its next-in-flows will be removed from
   * mBlock using StealFrame() before being added to mPushedFloats.
   * All appended frames will be marked NS_FRAME_IS_PUSHED_FLOAT.
   */
  void AppendPushedFloatChain(nsIFrame* aFloatCont);

  // Track child overflow continuations.
  nsOverflowContinuationTracker* mOverflowTracker;

  //----------------------------------------

  // This state is "running" state updated by the reflow of each line
  // in the block. This same state is "recovered" when a line is not
  // dirty and is passed over during incremental reflow.

  // The current line being reflowed
  // If it is mBlock->end_lines(), then it is invalid.
  nsLineList::iterator mCurrentLine;

  // When BRS_HAVELINEADJACENTTOTOP is set, this refers to a line
  // which we know is adjacent to the top of the block (in other words,
  // all lines before it are empty and do not have clearance. This line is
  // always before the current line.
  nsLineList::iterator mLineAdjacentToTop;

  // The current block-direction coordinate in the block
  nscoord mBCoord;

  // mBlock's computed physical border+padding with GetSkipSides applied.
  mozilla::LogicalMargin mBorderPadding;

  // The overflow areas of all floats placed so far
  nsOverflowAreas mFloatOverflowAreas;

  nsFloatCacheFreeList mFloatCacheFreeList;

  // Previous child. This is used when pulling up a frame to update
  // the sibling list.
  nsIFrame* mPrevChild;

  // The previous child frames collapsed bottom margin value.
  nsCollapsingMargin mPrevBEndMargin;

  // The current next-in-flow for the block. When lines are pulled
  // from a next-in-flow, this is used to know which next-in-flow to
  // pull from. When a next-in-flow is emptied of lines, we advance
  // this to the next next-in-flow.
  nsBlockFrame* mNextInFlow;

  //----------------------------------------

  // Temporary line-reflow state. This state is used during the reflow
  // of a given line, but doesn't have meaning before or after.

  // The list of floats that are "current-line" floats. These are
  // added to the line after the line has been reflowed, to keep the
  // list fiddling from being N^2.
  nsFloatCacheFreeList mCurrentLineFloats;

  // The list of floats which are "below current-line"
  // floats. These are reflowed/placed after the line is reflowed
  // and placed. Again, this is done to keep the list fiddling from
  // being N^2.
  nsFloatCacheFreeList mBelowCurrentLineFloats;

  nscoord mMinLineHeight;

  int32_t mLineNumber;

  int16_t mFlags;
 
  uint8_t mFloatBreakType;

  // The amount of computed block-direction size "consumed" by previous-in-flows.
  nscoord mConsumedBSize;

  void SetFlag(uint32_t aFlag, bool aValue)
  {
    NS_ASSERTION(aFlag<=BRS_LASTFLAG, "bad flag");
    if (aValue) { // set flag
      mFlags |= aFlag;
    }
    else {        // unset flag
      mFlags &= ~aFlag;
    }
  }

  bool GetFlag(uint32_t aFlag) const
  {
    NS_ASSERTION(aFlag<=BRS_LASTFLAG, "bad flag");
    return !!(mFlags & aFlag);
  }
};

#endif // nsBlockReflowState_h__