gecko-dev/layout/generic/nsBlockReflowContext.h

/* -*- 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 a parent frame uses to reflow a block frame */

#ifndef nsBlockReflowContext_h___
#define nsBlockReflowContext_h___

#include "nsIFrame.h"
#include "nsHTMLReflowMetrics.h"

class nsBlockReflowState;
struct nsHTMLReflowState;
class nsLineBox;
class nsPresContext;

/**
 * An encapsulation of the state and algorithm for reflowing block frames.
 */
class nsBlockReflowContext {
public:
  nsBlockReflowContext(nsPresContext* aPresContext,
                       const nsHTMLReflowState& aParentRS);
  ~nsBlockReflowContext() { }

  void ReflowBlock(const mozilla::LogicalRect& aSpace,
                   bool                        aApplyBStartMargin,
                   nsCollapsingMargin&         aPrevMargin,
                   nscoord                     aClearance,
                   bool                        aIsAdjacentWithBStart,
                   nsLineBox*                  aLine,
                   nsHTMLReflowState&          aReflowState,
                   nsReflowStatus&             aReflowStatus,
                   nsBlockReflowState&         aState);

  bool PlaceBlock(const nsHTMLReflowState& aReflowState,
                  bool                     aForceFit,
                  nsLineBox*               aLine,
                  nsCollapsingMargin&      aBEndMarginResult /* out */,
                  nsOverflowAreas&         aOverflowAreas,
                  nsReflowStatus           aReflowStatus);

  nsCollapsingMargin& GetCarriedOutBEndMargin() {
    return mMetrics.mCarriedOutBEndMargin;
  }

  const nsHTMLReflowMetrics& GetMetrics() const {
    return mMetrics;
  }

  /**
   * Computes the collapsed block-start margin (in the context's parent's
   * writing mode) for a block whose reflow state is in aRS.
   * The computed margin is added into aMargin, whose writing mode is the
   * parent's mode as found in mMetrics.GetWritingMode(); note this may not be
   * the block's own writing mode as found in aRS.
   * If aClearanceFrame is null then this is the first optimistic pass which
   * shall assume that no frames have clearance, and we clear the HasClearance
   * on all frames encountered.
   * If non-null, this is the second pass and the caller has decided
   * aClearanceFrame needs clearance (and we will therefore stop collapsing
   * there); also, this function is responsible for marking it with
   * SetHasClearance.
   * If in the optimistic pass any frame is encountered that might possibly
   * need clearance (i.e., if we really needed the optimism assumption) then
   * we set aMayNeedRetry to true.
   * We return true if we changed the clearance state of any line and marked it
   * dirty.
   */
  bool ComputeCollapsedBStartMargin(const nsHTMLReflowState& aRS,
                                    nsCollapsingMargin* aMargin,
                                    nsIFrame* aClearanceFrame,
                                    bool* aMayNeedRetry,
                                    bool* aIsEmpty = nullptr);

protected:
  nsPresContext* mPresContext;
  const nsHTMLReflowState& mOuterReflowState;

  nsIFrame* mFrame;
  mozilla::LogicalRect mSpace;

  nscoord mICoord, mBCoord;
  nsSize mContainerSize;
  mozilla::WritingMode mWritingMode;
  nsHTMLReflowMetrics mMetrics;
  nsCollapsingMargin mBStartMargin;
};

#endif /* nsBlockReflowContext_h___ */