gecko-dev/layout/generic/nsHTMLReflowMetrics.h

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/* struct containing the output from nsIFrame::Reflow */

#ifndef nsHTMLReflowMetrics_h___
#define nsHTMLReflowMetrics_h___

#include <stdio.h>
#include "nsISupports.h"
#include "nsMargin.h"
#include "nsRect.h"
// for MOZ_MATHML
#include "nsIRenderingContext.h" //to get struct nsBoundingMetrics

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

// Option flags
#ifdef MOZ_MATHML
#define NS_REFLOW_CALC_BOUNDING_METRICS  0x0001
#endif

/**
 * An nsCollapsingMargin represents a vertical collapsing margin between
 * blocks as described in section 8.3.1 of CSS2,
 * <URL: http://www.w3.org/TR/REC-CSS2/box.html#collapsing-margins >.
 *
 * All adjacent vertical margins collapse, and the resulting margin is
 * the sum of the largest positive margin included and the smallest (most
 * negative) negative margin included.
 */
struct nsCollapsingMargin {
  private:
    nscoord mMostPos;  // the largest positive margin included
    nscoord mMostNeg;  // the smallest negative margin included

  public:
    nsCollapsingMargin()
        : mMostPos(0),
          mMostNeg(0)
      {
      }

    nsCollapsingMargin(const nsCollapsingMargin& aOther)
        : mMostPos(aOther.mMostPos),
          mMostNeg(aOther.mMostNeg)
      {
      }

    PRBool operator==(const nsCollapsingMargin& aOther)
      {
        return mMostPos == aOther.mMostPos &&
          mMostNeg == aOther.mMostNeg;
      }

    PRBool operator!=(const nsCollapsingMargin& aOther)
      {
        return !(*this == aOther);
      }

    nsCollapsingMargin& operator=(const nsCollapsingMargin& aOther)
      {
        mMostPos = aOther.mMostPos;
        mMostNeg = aOther.mMostNeg;
        return *this;
      }

    void Include(nscoord aCoord)
      {
        if (aCoord > mMostPos)
          mMostPos = aCoord;
        else if (aCoord < mMostNeg)
          mMostNeg = aCoord;
      }

    void Include(const nsCollapsingMargin& aOther)
      {
        if (aOther.mMostPos > mMostPos)
          mMostPos = aOther.mMostPos;
        if (aOther.mMostNeg < mMostNeg)
          mMostNeg = aOther.mMostNeg;
      }

    void Zero()
      {
        mMostPos = 0;
        mMostNeg = 0;
      }

    PRBool IsZero() const
      {
        return (mMostPos == 0) && (mMostNeg == 0);
      }

    nscoord get() const
      {
        return mMostPos + mMostNeg;
      }
};

/**
 * Reflow metrics used to return the frame's desired size and alignment
 * information.
 *
 * @see #Reflow()
 */
struct nsHTMLReflowMetrics {
  nscoord width, height;    // [OUT] desired width and height (border-box)
  nscoord ascent;           // [OUT] baseline (from top), or ASK_FOR_BASELINE

  enum { ASK_FOR_BASELINE = nscoord_MAX };

#ifdef MOZ_MATHML
  // Metrics that _exactly_ enclose the text to allow precise MathML placements.
  // If the NS_REFLOW_CALC_BOUNDING_METRICS flag is set, then the caller is 
  // requesting that you also compute additional details about your inner
  // bounding box and italic correction. For example, the bounding box of
  // msup is the smallest rectangle that _exactly_ encloses both the text
  // of the base and the text of the superscript.
  nsBoundingMetrics mBoundingMetrics;  // [OUT]
#endif

  // Carried out bottom margin values. This is the collapsed
  // (generational) bottom margin value.
  nsCollapsingMargin mCarriedOutBottomMargin;
  
  // For frames that have content that overflow their content area
  // (NS_FRAME_OUTSIDE_CHILDREN) this rectangle represents the total area
  // of the frame including visible overflow, i.e., don't include overflowing
  // content that is hidden.
  // The rect is in the local coordinate space of the frame, and should be at
  // least as big as the desired size. If there is no content that overflows,
  // then the overflow area is identical to the desired size and should be
  // {0, 0, mWidth, mHeight}.
  nsRect mOverflowArea;

  PRUint32 mFlags;
 
  // XXXldb Should |aFlags| generally be passed from parent to child?
  // Some places do it, and some don't.  |aFlags| should perhaps go away
  // entirely.
  nsHTMLReflowMetrics(PRUint32 aFlags = 0) {
    mFlags = aFlags;
    mOverflowArea.x = 0;
    mOverflowArea.y = 0;
    mOverflowArea.width = 0;
    mOverflowArea.height = 0;
#ifdef MOZ_MATHML
    mBoundingMetrics.Clear();
#endif

    // XXX These are OUT parameters and so they shouldn't have to be
    // initialized, but there are some bad frame classes that aren't
    // properly setting them when returning from Reflow()...
    width = height = 0;
    ascent = ASK_FOR_BASELINE;
  }

  nsHTMLReflowMetrics& operator=(const nsHTMLReflowMetrics& aOther)
  {
    mFlags = aOther.mFlags;
    mCarriedOutBottomMargin = aOther.mCarriedOutBottomMargin;
    mOverflowArea.x = aOther.mOverflowArea.x;
    mOverflowArea.y = aOther.mOverflowArea.y;
    mOverflowArea.width = aOther.mOverflowArea.width;
    mOverflowArea.height = aOther.mOverflowArea.height;
#ifdef MOZ_MATHML
    mBoundingMetrics = aOther.mBoundingMetrics;
#endif

    width = aOther.width;
    height = aOther.height;
    ascent = aOther.ascent;
    return *this;
  }

};

#endif /* nsHTMLReflowMetrics_h___ */