C++ nsHTMLReflowMetrics::TopAscent方法代码示例

void
nsMathMLmpaddedFrame::UpdateValue(int32_t                  aSign,
                                  int32_t                  aPseudoUnit,
                                  const nsCSSValue&        aCSSValue,
                                  const nsHTMLReflowMetrics& aDesiredSize,
                                  nscoord&                 aValueToUpdate) const
{
  nsCSSUnit unit = aCSSValue.GetUnit();
  if (NS_MATHML_SIGN_INVALID != aSign && eCSSUnit_Null != unit) {
    nscoord scaler = 0, amount = 0;

    if (eCSSUnit_Percent == unit || eCSSUnit_Number == unit) {
      switch(aPseudoUnit) {
        case NS_MATHML_PSEUDO_UNIT_WIDTH:
             scaler = aDesiredSize.Width();
             break;

        case NS_MATHML_PSEUDO_UNIT_HEIGHT:
             scaler = aDesiredSize.TopAscent();
             break;

        case NS_MATHML_PSEUDO_UNIT_DEPTH:
             scaler = aDesiredSize.Height() - aDesiredSize.TopAscent();
             break;

        default:
          // if we ever reach here, it would mean something is wrong 
          // somewhere with the setup and/or the caller
          NS_ERROR("Unexpected Pseudo Unit");
          return;
      }
    }

    if (eCSSUnit_Number == unit)
      amount = NSToCoordRound(float(scaler) * aCSSValue.GetFloatValue());
    else if (eCSSUnit_Percent == unit)
      amount = NSToCoordRound(float(scaler) * aCSSValue.GetPercentValue());
    else
      amount = CalcLength(PresContext(), mStyleContext, aCSSValue);

    if (NS_MATHML_SIGN_PLUS == aSign)
      aValueToUpdate += amount;
    else if (NS_MATHML_SIGN_MINUS == aSign)
      aValueToUpdate -= amount;
    else
      aValueToUpdate  = amount;
  }
}

// For token elements, mBoundingMetrics is computed at the ReflowToken
// pass, it is not computed here because our children may be text frames
// that do not implement the GetBoundingMetrics() interface.
/* virtual */ nsresult
nsMathMLTokenFrame::Place(nsRenderingContext& aRenderingContext,
                          bool                 aPlaceOrigin,
                          nsHTMLReflowMetrics& aDesiredSize)
{
  mBoundingMetrics = nsBoundingMetrics();
  for (nsIFrame* childFrame = GetFirstPrincipalChild(); childFrame;
       childFrame = childFrame->GetNextSibling()) {
    nsHTMLReflowMetrics childSize(aDesiredSize.GetWritingMode());
    GetReflowAndBoundingMetricsFor(childFrame, childSize,
                                   childSize.mBoundingMetrics, nullptr);
    // compute and cache the bounding metrics
    mBoundingMetrics += childSize.mBoundingMetrics;
  }

  nsRefPtr<nsFontMetrics> fm;
  nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm));
  nscoord ascent = fm->MaxAscent();
  nscoord descent = fm->MaxDescent();

  aDesiredSize.mBoundingMetrics = mBoundingMetrics;
  aDesiredSize.Width() = mBoundingMetrics.width;
  aDesiredSize.SetTopAscent(std::max(mBoundingMetrics.ascent, ascent));
  aDesiredSize.Height() = aDesiredSize.TopAscent() +
                        std::max(mBoundingMetrics.descent, descent);

  if (aPlaceOrigin) {
    nscoord dy, dx = 0;
    for (nsIFrame* childFrame = GetFirstPrincipalChild(); childFrame;
         childFrame = childFrame->GetNextSibling()) {
      nsHTMLReflowMetrics childSize(aDesiredSize.GetWritingMode());
      GetReflowAndBoundingMetricsFor(childFrame, childSize,
                                     childSize.mBoundingMetrics);

      // place and size the child; (dx,0) makes the caret happy - bug 188146
      dy = childSize.Height() == 0 ? 0 : aDesiredSize.TopAscent() - childSize.TopAscent();
      FinishReflowChild(childFrame, PresContext(), childSize, nullptr, dx, dy, 0);
      dx += childSize.Width();
    }
  }

  SetReference(nsPoint(0, aDesiredSize.TopAscent()));

  return NS_OK;
}

void
nsMathMLmspaceFrame::Reflow(nsPresContext*          aPresContext,
                            nsHTMLReflowMetrics&     aDesiredSize,
                            const nsHTMLReflowState& aReflowState,
                            nsReflowStatus&          aStatus)
{
  ProcessAttributes(aPresContext);

  mBoundingMetrics = nsBoundingMetrics();
  mBoundingMetrics.width = mWidth;
  mBoundingMetrics.ascent = mHeight;
  mBoundingMetrics.descent = mDepth;
  mBoundingMetrics.leftBearing = 0;
  mBoundingMetrics.rightBearing = mBoundingMetrics.width;

  aDesiredSize.SetTopAscent(mHeight);
  aDesiredSize.Width() = std::max(0, mBoundingMetrics.width);
  aDesiredSize.Height() = aDesiredSize.TopAscent() + mDepth;
  // Also return our bounding metrics
  aDesiredSize.mBoundingMetrics = mBoundingMetrics;

  aStatus = NS_FRAME_COMPLETE;
  NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
}

nsresult
nsFirstLetterFrame::Reflow(nsPresContext*          aPresContext,
                           nsHTMLReflowMetrics&     aMetrics,
                           const nsHTMLReflowState& aReflowState,
                           nsReflowStatus&          aReflowStatus)
{
  DO_GLOBAL_REFLOW_COUNT("nsFirstLetterFrame");
  DISPLAY_REFLOW(aPresContext, this, aReflowState, aMetrics, aReflowStatus);
  nsresult rv = NS_OK;

  // Grab overflow list
  DrainOverflowFrames(aPresContext);

  nsIFrame* kid = mFrames.FirstChild();

  // Setup reflow state for our child
  nsSize availSize(aReflowState.AvailableWidth(), aReflowState.AvailableHeight());
  const nsMargin& bp = aReflowState.ComputedPhysicalBorderPadding();
  nscoord lr = bp.left + bp.right;
  nscoord tb = bp.top + bp.bottom;
  NS_ASSERTION(availSize.width != NS_UNCONSTRAINEDSIZE,
               "should no longer use unconstrained widths");
  availSize.width -= lr;
  if (NS_UNCONSTRAINEDSIZE != availSize.height) {
    availSize.height -= tb;
  }

  // Reflow the child
  if (!aReflowState.mLineLayout) {
    // When there is no lineLayout provided, we provide our own. The
    // only time that the first-letter-frame is not reflowing in a
    // line context is when its floating.
    nsHTMLReflowState rs(aPresContext, aReflowState, kid, availSize);
    nsLineLayout ll(aPresContext, nullptr, &aReflowState, nullptr);

    ll.BeginLineReflow(bp.left, bp.top, availSize.width, NS_UNCONSTRAINEDSIZE,
                       false, true,
                       ll.LineContainerFrame()->GetWritingMode(kid),
                       aReflowState.AvailableWidth());
    rs.mLineLayout = ≪
    ll.SetInFirstLetter(true);
    ll.SetFirstLetterStyleOK(true);

    kid->WillReflow(aPresContext);
    kid->Reflow(aPresContext, aMetrics, rs, aReflowStatus);

    ll.EndLineReflow();
    ll.SetInFirstLetter(false);

    // In the floating first-letter case, we need to set this ourselves;
    // nsLineLayout::BeginSpan will set it in the other case
    mBaseline = aMetrics.TopAscent();
  }
  else {
    // Pretend we are a span and reflow the child frame
    nsLineLayout* ll = aReflowState.mLineLayout;
    bool          pushedFrame;

    ll->SetInFirstLetter(
      mStyleContext->GetPseudo() == nsCSSPseudoElements::firstLetter);
    ll->BeginSpan(this, &aReflowState, bp.left, availSize.width, &mBaseline);
    ll->ReflowFrame(kid, aReflowStatus, &aMetrics, pushedFrame);
    ll->EndSpan(this);
    ll->SetInFirstLetter(false);
  }

  // Place and size the child and update the output metrics
  kid->SetRect(nsRect(bp.left, bp.top, aMetrics.Width(), aMetrics.Height()));
  kid->FinishAndStoreOverflow(&aMetrics);
  kid->DidReflow(aPresContext, nullptr, nsDidReflowStatus::FINISHED);

  aMetrics.Width() += lr;
  aMetrics.Height() += tb;
  aMetrics.SetTopAscent(aMetrics.TopAscent() + bp.top);

  // Ensure that the overflow rect contains the child textframe's overflow rect.
  // Note that if this is floating, the overline/underline drawable area is in
  // the overflow rect of the child textframe.
  aMetrics.UnionOverflowAreasWithDesiredBounds();
  ConsiderChildOverflow(aMetrics.mOverflowAreas, kid);

  if (!NS_INLINE_IS_BREAK_BEFORE(aReflowStatus)) {
    // Create a continuation or remove existing continuations based on
    // the reflow completion status.
    if (NS_FRAME_IS_COMPLETE(aReflowStatus)) {
      if (aReflowState.mLineLayout) {
        aReflowState.mLineLayout->SetFirstLetterStyleOK(false);
      }
      nsIFrame* kidNextInFlow = kid->GetNextInFlow();
      if (kidNextInFlow) {
        // Remove all of the childs next-in-flows
        static_cast<nsContainerFrame*>(kidNextInFlow->GetParent())
          ->DeleteNextInFlowChild(kidNextInFlow, true);
      }
    }
    else {
      // Create a continuation for the child frame if it doesn't already
      // have one.
      if (!IsFloating()) {
        nsIFrame* nextInFlow;
//.........这里部分代码省略.........

//.........这里部分代码省略.........
          break;
        }
        // Keep reparenting the remaining siblings, but don't reflow them.
        nsFrameList* pushedFrames = GetOverflowFrames();
        if (pushedFrames && pushedFrames->FirstChild() == frame) {
          // Don't bother if |frame| was pushed to our overflow list.
          break;
        }
      } else {
        irs.mPrevFrame = frame;
      }
    }
    frame = frame->GetNextSibling();
  }

  // Attempt to pull frames from our next-in-flow until we can't
  if (!done && GetNextInFlow()) {
    while (true) {
      bool reflowingFirstLetter = lineLayout->GetFirstLetterStyleOK();
      bool isComplete;
      if (!frame) { // Could be non-null if we pulled a first-letter frame and
                    // it created a continuation, since we don't push those.
        frame = PullOneFrame(aPresContext, irs, &isComplete);
      }
#ifdef NOISY_PUSHING
      printf("%p pulled up %p\n", this, frame);
#endif
      if (nullptr == frame) {
        if (!isComplete) {
          aStatus = NS_FRAME_NOT_COMPLETE;
        }
        break;
      }
      ReflowInlineFrame(aPresContext, aReflowState, irs, frame, aStatus);
      if (NS_INLINE_IS_BREAK(aStatus) || 
          (!reflowingFirstLetter && NS_FRAME_IS_NOT_COMPLETE(aStatus))) {
        break;
      }
      irs.mPrevFrame = frame;
      frame = frame->GetNextSibling();
    }
  }

  NS_ASSERTION(!NS_FRAME_IS_COMPLETE(aStatus) || !GetOverflowFrames(),
               "We can't be complete AND have overflow frames!");

  // If after reflowing our children they take up no area then make
  // sure that we don't either.
  //
  // Note: CSS demands that empty inline elements still affect the
  // line-height calculations. However, continuations of an inline
  // that are empty we force to empty so that things like collapsed
  // whitespace in an inline element don't affect the line-height.
  aMetrics.ISize(lineWM) = lineLayout->EndSpan(this);

  // Compute final width.

  // XXX Note that that the padding start and end are in the frame's
  //     writing mode, but the metrics' inline-size is in the line's
  //     writing mode. This makes sense if the line and frame are both
  //     vertical or both horizontal, but what should happen with
  //     orthogonal inlines?

  // Make sure to not include our start border and padding if we have a prev
  // continuation or if we're in a part of an {ib} split other than the first
  // one.  For box-decoration-break:clone we always include our start border
  // and padding since all continuations have them.
  if ((!GetPrevContinuation() && !FrameIsNonFirstInIBSplit()) ||
      boxDecorationBreakClone) {
    aMetrics.ISize(lineWM) += framePadding.IStart(frameWM);
  }

  /*
   * We want to only apply the end border and padding if we're the last
   * continuation and either not in an {ib} split or the last part of it.  To
   * be the last continuation we have to be complete (so that we won't get a
   * next-in-flow) and have no non-fluid continuations on our continuation
   * chain.  For box-decoration-break:clone we always apply the end border and
   * padding since all continuations have them.
   */
  if ((NS_FRAME_IS_COMPLETE(aStatus) &&
       !LastInFlow()->GetNextContinuation() &&
       !FrameIsNonLastInIBSplit()) ||
      boxDecorationBreakClone) {
    aMetrics.ISize(lineWM) += framePadding.IEnd(frameWM);
  }

  nsLayoutUtils::SetBSizeFromFontMetrics(this, aMetrics, aReflowState,
                                         framePadding, lineWM, frameWM);

  // For now our overflow area is zero. The real value will be
  // computed in |nsLineLayout::RelativePositionFrames|.
  aMetrics.mOverflowAreas.Clear();

#ifdef NOISY_FINAL_SIZE
  ListTag(stdout);
  printf(": metrics=%d,%d ascent=%d\n",
         aMetrics.Width(), aMetrics.Height(), aMetrics.TopAscent());
#endif
}

/* virtual */ nsresult
nsMathMLmpaddedFrame::Place(nsRenderingContext& aRenderingContext,
                            bool                 aPlaceOrigin,
                            nsHTMLReflowMetrics& aDesiredSize)
{
  nsresult rv =
    nsMathMLContainerFrame::Place(aRenderingContext, false, aDesiredSize);
  if (NS_MATHML_HAS_ERROR(mPresentationData.flags) || NS_FAILED(rv)) {
    DidReflowChildren(GetFirstPrincipalChild());
    return rv;
  }

  nscoord height = aDesiredSize.TopAscent();
  nscoord depth  = aDesiredSize.Height() - aDesiredSize.TopAscent();
  // The REC says:
  //
  // "The lspace attribute ('leading' space) specifies the horizontal location
  // of the positioning point of the child content with respect to the
  // positioning point of the mpadded element. By default they coincide, and
  // therefore absolute values for lspace have the same effect as relative
  // values."
  //
  // "MathML renderers should ensure that, except for the effects of the
  // attributes, the relative spacing between the contents of the mpadded
  // element and surrounding MathML elements would not be modified by replacing
  // an mpadded element with an mrow element with the same content, even if
  // linebreaking occurs within the mpadded element."
  //
  // (http://www.w3.org/TR/MathML/chapter3.html#presm.mpadded)
  // 
  // "In those discussions, the terms leading and trailing are used to specify
  // a side of an object when which side to use depends on the directionality;
  // ie. leading means left in LTR but right in RTL."
  // (http://www.w3.org/TR/MathML/chapter3.html#presm.bidi.math)
  nscoord lspace = 0;
  // In MathML3, "width" will be the bounding box width and "advancewidth" will
  // refer "to the horizontal distance between the positioning point of the
  // mpadded and the positioning point for the following content".  MathML2
  // doesn't make the distinction.
  nscoord width  = aDesiredSize.Width();
  nscoord voffset = 0;

  int32_t pseudoUnit;
  nscoord initialWidth = width;

  // update width
  pseudoUnit = (mWidthPseudoUnit == NS_MATHML_PSEUDO_UNIT_ITSELF)
             ? NS_MATHML_PSEUDO_UNIT_WIDTH : mWidthPseudoUnit;
  UpdateValue(mWidthSign, pseudoUnit, mWidth,
              aDesiredSize, width);
  width = std::max(0, width);

  // update "height" (this is the ascent in the terminology of the REC)
  pseudoUnit = (mHeightPseudoUnit == NS_MATHML_PSEUDO_UNIT_ITSELF)
             ? NS_MATHML_PSEUDO_UNIT_HEIGHT : mHeightPseudoUnit;
  UpdateValue(mHeightSign, pseudoUnit, mHeight,
              aDesiredSize, height);
  height = std::max(0, height);

  // update "depth" (this is the descent in the terminology of the REC)
  pseudoUnit = (mDepthPseudoUnit == NS_MATHML_PSEUDO_UNIT_ITSELF)
             ? NS_MATHML_PSEUDO_UNIT_DEPTH : mDepthPseudoUnit;
  UpdateValue(mDepthSign, pseudoUnit, mDepth,
              aDesiredSize, depth);
  depth = std::max(0, depth);

  // update lspace
  if (mLeadingSpacePseudoUnit != NS_MATHML_PSEUDO_UNIT_ITSELF) {
    pseudoUnit = mLeadingSpacePseudoUnit;
    UpdateValue(mLeadingSpaceSign, pseudoUnit, mLeadingSpace,
                aDesiredSize, lspace);
  }

  // update voffset
  if (mVerticalOffsetPseudoUnit != NS_MATHML_PSEUDO_UNIT_ITSELF) {
    pseudoUnit = mVerticalOffsetPseudoUnit;
    UpdateValue(mVerticalOffsetSign, pseudoUnit, mVerticalOffset,
                aDesiredSize, voffset);
  }
  // do the padding now that we have everything
  // The idea here is to maintain the invariant that <mpadded>...</mpadded> (i.e.,
  // with no attributes) looks the same as <mrow>...</mrow>. But when there are
  // attributes, tweak our metrics and move children to achieve the desired visual
  // effects.

  if ((StyleVisibility()->mDirection ?
       mWidthSign : mLeadingSpaceSign) != NS_MATHML_SIGN_INVALID) {
    // there was padding on the left. dismiss the left italic correction now
    // (so that our parent won't correct us)
    mBoundingMetrics.leftBearing = 0;
  }

  if ((StyleVisibility()->mDirection ?
       mLeadingSpaceSign : mWidthSign) != NS_MATHML_SIGN_INVALID) {
    // there was padding on the right. dismiss the right italic correction now
    // (so that our parent won't correct us)
    mBoundingMetrics.width = width;
    mBoundingMetrics.rightBearing = mBoundingMetrics.width;
  }

//.........这里部分代码省略.........

//.........这里部分代码省略.........

      // Update vertical parameters
      radicalAscent = bmBase.ascent + psi + mRuleThickness;
      radicalDescent = std::max(bmBase.descent,
                              (bmRadicalChar.ascent + bmRadicalChar.descent -
                               radicalAscent));

      mBoundingMetrics.ascent = std::max(mBoundingMetrics.ascent,
                                       radicalAscent);
      mBoundingMetrics.descent = std::max(mBoundingMetrics.descent,
                                        radicalDescent);
    }
  }

  ///////////////
  //
  if (IsToDraw(NOTATION_CIRCLE) ||
      IsToDraw(NOTATION_ROUNDEDBOX) ||
      (IsToDraw(NOTATION_LEFT) && IsToDraw(NOTATION_RIGHT))) {
    // center the menclose around the content (horizontally)
    dx_left = dx_right = std::max(dx_left, dx_right);
  }

  ///////////////
  // The maximum size is now computed: set the remaining parameters
  mBoundingMetrics.width = dx_left + bmBase.width + dx_right;

  mBoundingMetrics.leftBearing = std::min(0, dx_left + bmBase.leftBearing);
  mBoundingMetrics.rightBearing =
    std::max(mBoundingMetrics.width, dx_left + bmBase.rightBearing);
  
  aDesiredSize.Width() = mBoundingMetrics.width;

  aDesiredSize.SetTopAscent(std::max(mBoundingMetrics.ascent, baseSize.TopAscent()));
  aDesiredSize.Height() = aDesiredSize.TopAscent() +
    std::max(mBoundingMetrics.descent, baseSize.Height() - baseSize.TopAscent());

  if (IsToDraw(NOTATION_LONGDIV) || IsToDraw(NOTATION_RADICAL)) {
    // get the leading to be left at the top of the resulting frame
    // this seems more reliable than using fm->GetLeading() on suspicious
    // fonts
    nscoord leading = nscoord(0.2f * mEmHeight);
    nscoord desiredSizeAscent = aDesiredSize.TopAscent();
    nscoord desiredSizeDescent = aDesiredSize.Height() - aDesiredSize.TopAscent();
    
    if (IsToDraw(NOTATION_LONGDIV)) {
      desiredSizeAscent = std::max(desiredSizeAscent,
                                 longdivAscent + leading);
      desiredSizeDescent = std::max(desiredSizeDescent,
                                  longdivDescent + mRuleThickness);
    }
    
    if (IsToDraw(NOTATION_RADICAL)) {
      desiredSizeAscent = std::max(desiredSizeAscent,
                                 radicalAscent + leading);
      desiredSizeDescent = std::max(desiredSizeDescent,
                                  radicalDescent + mRuleThickness);
    }

    aDesiredSize.SetTopAscent(desiredSizeAscent);
    aDesiredSize.Height() = desiredSizeAscent + desiredSizeDescent;
  }
    
  if (IsToDraw(NOTATION_CIRCLE) ||
      IsToDraw(NOTATION_ROUNDEDBOX) ||
      (IsToDraw(NOTATION_TOP) && IsToDraw(NOTATION_BOTTOM))) {

nsresult
nsMathMLmfencedFrame::Reflow(nsPresContext*          aPresContext,
                             nsHTMLReflowMetrics&     aDesiredSize,
                             const nsHTMLReflowState& aReflowState,
                             nsReflowStatus&          aStatus)
{
  nsresult rv;
  aDesiredSize.Width() = aDesiredSize.Height() = 0;
  aDesiredSize.SetTopAscent(0);
  aDesiredSize.mBoundingMetrics = nsBoundingMetrics();

  int32_t i;
  const nsStyleFont* font = StyleFont();
  nsRefPtr<nsFontMetrics> fm;
  nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm));
  aReflowState.rendContext->SetFont(fm);
  nscoord axisHeight, em;
  GetAxisHeight(*aReflowState.rendContext, fm, axisHeight);
  GetEmHeight(fm, em);
  // leading to be left at the top and the bottom of stretched chars
  nscoord leading = NSToCoordRound(0.2f * em); 

  /////////////
  // Reflow children
  // Asking each child to cache its bounding metrics

  // Note that we don't use the base method nsMathMLContainerFrame::Reflow()
  // because we want to stretch our fences, separators and stretchy frames using
  // the *same* initial aDesiredSize.mBoundingMetrics. If we were to use the base
  // method here, our stretchy frames will be stretched and placed, and we may
  // end up stretching our fences/separators with a different aDesiredSize.
  // XXX The above decision was revisited in bug 121748 and this code can be
  // refactored to use nsMathMLContainerFrame::Reflow() at some stage.

  nsReflowStatus childStatus;
  nsSize availSize(aReflowState.ComputedWidth(), NS_UNCONSTRAINEDSIZE);
  nsIFrame* firstChild = GetFirstPrincipalChild();
  nsIFrame* childFrame = firstChild;
  nscoord ascent = 0, descent = 0;
  if (firstChild || mOpenChar || mCloseChar || mSeparatorsCount > 0) {
    // We use the ASCII metrics to get our minimum height. This way,
    // if we have borders or a background, they will fit better with
    // other elements on the line.
    ascent = fm->MaxAscent();
    descent = fm->MaxDescent();
  }
  while (childFrame) {
    nsHTMLReflowMetrics childDesiredSize(aReflowState.GetWritingMode(),
                                         aDesiredSize.mFlags
                                         | NS_REFLOW_CALC_BOUNDING_METRICS);
    nsHTMLReflowState childReflowState(aPresContext, aReflowState,
                                       childFrame, availSize);
    rv = ReflowChild(childFrame, aPresContext, childDesiredSize,
                     childReflowState, childStatus);
    //NS_ASSERTION(NS_FRAME_IS_COMPLETE(childStatus), "bad status");
    if (NS_FAILED(rv)) {
      // Call DidReflow() for the child frames we successfully did reflow.
      DidReflowChildren(firstChild, childFrame);
      return rv;
    }

    SaveReflowAndBoundingMetricsFor(childFrame, childDesiredSize,
                                    childDesiredSize.mBoundingMetrics);

    nscoord childDescent = childDesiredSize.Height() - childDesiredSize.TopAscent();
    if (descent < childDescent)
      descent = childDescent;
    if (ascent < childDesiredSize.TopAscent())
      ascent = childDesiredSize.TopAscent();

    childFrame = childFrame->GetNextSibling();
  }

  /////////////
  // Ask stretchy children to stretch themselves

  nsBoundingMetrics containerSize;
  nsStretchDirection stretchDir = NS_STRETCH_DIRECTION_VERTICAL;

  GetPreferredStretchSize(*aReflowState.rendContext,
                          0, /* i.e., without embellishments */
                          stretchDir, containerSize);
  childFrame = firstChild;
  while (childFrame) {
    nsIMathMLFrame* mathmlChild = do_QueryFrame(childFrame);
    if (mathmlChild) {
      nsHTMLReflowMetrics childDesiredSize(aReflowState.GetWritingMode());
      // retrieve the metrics that was stored at the previous pass
      GetReflowAndBoundingMetricsFor(childFrame, childDesiredSize,
                                     childDesiredSize.mBoundingMetrics);
      
      mathmlChild->Stretch(*aReflowState.rendContext, 
                           stretchDir, containerSize, childDesiredSize);
      // store the updated metrics
      SaveReflowAndBoundingMetricsFor(childFrame, childDesiredSize,
                                      childDesiredSize.mBoundingMetrics);
      
      nscoord childDescent = childDesiredSize.Height() - childDesiredSize.TopAscent();
      if (descent < childDescent)
        descent = childDescent;
//.........这里部分代码省略.........

//.........这里部分代码省略.........
            (container.ascent + container.descent)/2 - container.ascent;
        } // else align the baselines
        mBoundingMetrics.ascent = height - mBoundingMetrics.descent;
      }
    }
  }

  // Fixup for the final height.
  // On one hand, our stretchy height can sometimes be shorter than surrounding
  // ASCII chars, e.g., arrow symbols have |mBoundingMetrics.ascent + leading|
  // that is smaller than the ASCII's ascent, hence when painting the background
  // later, it won't look uniform along the line.
  // On the other hand, sometimes we may leave too much gap when our glyph happens
  // to come from a font with tall glyphs. For example, since CMEX10 has very tall
  // glyphs, its natural font metrics are large, even if we pick a small glyph
  // whose size is comparable to the size of a normal ASCII glyph.
  // So to avoid uneven spacing in either of these two cases, we use the height
  // of the ASCII font as a reference and try to match it if possible.

  // special case for accents... keep them short to improve mouse operations...
  // an accent can only be the non-first child of <mover>, <munder>, <munderover>
  bool isAccent =
    NS_MATHML_EMBELLISH_IS_ACCENT(mEmbellishData.flags);
  if (isAccent) {
    nsEmbellishData parentData;
    GetEmbellishDataFrom(mParent, parentData);
    isAccent =
       (NS_MATHML_EMBELLISH_IS_ACCENTOVER(parentData.flags) ||
        NS_MATHML_EMBELLISH_IS_ACCENTUNDER(parentData.flags)) &&
       parentData.coreFrame != this;
  }
  if (isAccent && firstChild) {
    // see bug 188467 for what is going on here
    nscoord dy = aDesiredStretchSize.TopAscent() - (mBoundingMetrics.ascent + leading);
    aDesiredStretchSize.SetTopAscent(mBoundingMetrics.ascent + leading);
    aDesiredStretchSize.Height() = aDesiredStretchSize.TopAscent() + mBoundingMetrics.descent;

    firstChild->SetPosition(firstChild->GetPosition() - nsPoint(0, dy));
  }
  else if (useMathMLChar) {
    nscoord ascent = fm->MaxAscent();
    nscoord descent = fm->MaxDescent();
    aDesiredStretchSize.SetTopAscent(std::max(mBoundingMetrics.ascent + leading, ascent));
    aDesiredStretchSize.Height() = aDesiredStretchSize.TopAscent() +
                                 std::max(mBoundingMetrics.descent + leading, descent);
  }
  aDesiredStretchSize.Width() = mBoundingMetrics.width;
  aDesiredStretchSize.mBoundingMetrics = mBoundingMetrics;
  mReference.x = 0;
  mReference.y = aDesiredStretchSize.TopAscent();
  // Place our mMathMLChar, its origin is in our coordinate system
  if (useMathMLChar) {
    nscoord dy = aDesiredStretchSize.TopAscent() - mBoundingMetrics.ascent;
    mMathMLChar.SetRect(nsRect(0, dy, charSize.width, charSize.ascent + charSize.descent));
  }

  // Before we leave... there is a last item in the check-list:
  // If our parent is not embellished, it means we are the outermost embellished
  // container and so we put the spacing, otherwise we don't include the spacing,
  // the outermost embellished container will take care of it.

  if (!NS_MATHML_OPERATOR_HAS_EMBELLISH_ANCESTOR(mFlags)) {

    // Account the spacing if we are not an accent with explicit attributes
    nscoord leadingSpace = mEmbellishData.leadingSpace;
    if (isAccent && !NS_MATHML_OPERATOR_HAS_LSPACE_ATTR(mFlags)) {

//.........这里部分代码省略.........
      bool reflowingFirstLetter = lineLayout->GetFirstLetterStyleOK();
      bool isComplete;
      if (!frame) { // Could be non-null if we pulled a first-letter frame and
                    // it created a continuation, since we don't push those.
        frame = PullOneFrame(aPresContext, irs, &isComplete);
      }
#ifdef NOISY_PUSHING
      printf("%p pulled up %p\n", this, frame);
#endif
      if (nullptr == frame) {
        if (!isComplete) {
          aStatus = NS_FRAME_NOT_COMPLETE;
        }
        break;
      }
      rv = ReflowInlineFrame(aPresContext, aReflowState, irs, frame, aStatus);
      if (NS_FAILED(rv) ||
          NS_INLINE_IS_BREAK(aStatus) || 
          (!reflowingFirstLetter && NS_FRAME_IS_NOT_COMPLETE(aStatus))) {
        break;
      }
      irs.mPrevFrame = frame;
      frame = frame->GetNextSibling();
    }
  }

  NS_ASSERTION(!NS_FRAME_IS_COMPLETE(aStatus) || !GetOverflowFrames(),
               "We can't be complete AND have overflow frames!");

  // If after reflowing our children they take up no area then make
  // sure that we don't either.
  //
  // Note: CSS demands that empty inline elements still affect the
  // line-height calculations. However, continuations of an inline
  // that are empty we force to empty so that things like collapsed
  // whitespace in an inline element don't affect the line-height.
  aMetrics.Width() = lineLayout->EndSpan(this);

  // Compute final width.

  // Make sure to not include our start border and padding if we have a prev
  // continuation or if we're in a part of an {ib} split other than the first
  // one.
  if (!GetPrevContinuation() && !FrameIsNonFirstInIBSplit()) {
    aMetrics.Width() += ltr ? aReflowState.ComputedPhysicalBorderPadding().left
                          : aReflowState.ComputedPhysicalBorderPadding().right;
  }

  /*
   * We want to only apply the end border and padding if we're the last
   * continuation and either not in an {ib} split or the last part of it.  To
   * be the last continuation we have to be complete (so that we won't get a
   * next-in-flow) and have no non-fluid continuations on our continuation
   * chain.
   */
  if (NS_FRAME_IS_COMPLETE(aStatus) &&
      !LastInFlow()->GetNextContinuation() &&
      !FrameIsNonLastInIBSplit()) {
    aMetrics.Width() += ltr ? aReflowState.ComputedPhysicalBorderPadding().right
                          : aReflowState.ComputedPhysicalBorderPadding().left;
  }

  nsRefPtr<nsFontMetrics> fm;
  float inflation = nsLayoutUtils::FontSizeInflationFor(this);
  nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm), inflation);
  aReflowState.rendContext->SetFont(fm);

  if (fm) {
    // Compute final height of the frame.
    //
    // Do things the standard css2 way -- though it's hard to find it
    // in the css2 spec! It's actually found in the css1 spec section
    // 4.4 (you will have to read between the lines to really see
    // it).
    //
    // The height of our box is the sum of our font size plus the top
    // and bottom border and padding. The height of children do not
    // affect our height.
    aMetrics.SetTopAscent(fm->MaxAscent());
    aMetrics.Height() = fm->MaxHeight();
  } else {
    NS_WARNING("Cannot get font metrics - defaulting sizes to 0");
    aMetrics.SetTopAscent(aMetrics.Height() = 0);
  }
  aMetrics.SetTopAscent(aMetrics.TopAscent() + aReflowState.ComputedPhysicalBorderPadding().top);
  aMetrics.Height() += aReflowState.ComputedPhysicalBorderPadding().top +
    aReflowState.ComputedPhysicalBorderPadding().bottom;

  // For now our overflow area is zero. The real value will be
  // computed in |nsLineLayout::RelativePositionFrames|.
  aMetrics.mOverflowAreas.Clear();

#ifdef NOISY_FINAL_SIZE
  ListTag(stdout);
  printf(": metrics=%d,%d ascent=%d\n",
         aMetrics.Width(), aMetrics.Height(), aMetrics.TopAscent());
#endif

  return rv;
}