C++ nsRenderingContext::SetFont方法代码示例

void
nsPageFrame::PaintHeaderFooter(nsRenderingContext& aRenderingContext,
                               nsPoint aPt)
{
  nsPresContext* pc = PresContext();

  if (!mPD->mPrintSettings) {
    if (pc->Type() == nsPresContext::eContext_PrintPreview || pc->IsDynamic())
      mPD->mPrintSettings = pc->GetPrintSettings();
    if (!mPD->mPrintSettings)
      return;
  }

  nsRect rect(aPt, mRect.Size());
  aRenderingContext.SetColor(NS_RGB(0,0,0));

  // Get the FontMetrics to determine width.height of strings
  nsRefPtr<nsFontMetrics> fontMet;
  pc->DeviceContext()->GetMetricsFor(*mPD->mHeadFootFont, nullptr,
                                     pc->GetUserFontSet(),
                                     *getter_AddRefs(fontMet));

  aRenderingContext.SetFont(fontMet);

  nscoord ascent = 0;
  nscoord visibleHeight = 0;
  if (fontMet) {
    visibleHeight = fontMet->MaxHeight();
    ascent = fontMet->MaxAscent();
  }

  // print document headers and footers
  nsXPIDLString headerLeft, headerCenter, headerRight;
  mPD->mPrintSettings->GetHeaderStrLeft(getter_Copies(headerLeft));
  mPD->mPrintSettings->GetHeaderStrCenter(getter_Copies(headerCenter));
  mPD->mPrintSettings->GetHeaderStrRight(getter_Copies(headerRight));
  DrawHeaderFooter(aRenderingContext, eHeader,
                   headerLeft, headerCenter, headerRight,
                   rect, ascent, visibleHeight);

  nsXPIDLString footerLeft, footerCenter, footerRight;
  mPD->mPrintSettings->GetFooterStrLeft(getter_Copies(footerLeft));
  mPD->mPrintSettings->GetFooterStrCenter(getter_Copies(footerCenter));
  mPD->mPrintSettings->GetFooterStrRight(getter_Copies(footerRight));
  DrawHeaderFooter(aRenderingContext, eFooter,
                   footerLeft, footerCenter, footerRight,
                   rect, ascent, visibleHeight);
}

// exported routine that both munderover and msubsup share.
// munderover uses this when movablelimits is set.
nsresult
nsMathMLmsubsupFrame::PlaceSubSupScript(nsPresContext*      aPresContext,
                                        nsRenderingContext& aRenderingContext,
                                        PRBool               aPlaceOrigin,
                                        nsHTMLReflowMetrics& aDesiredSize,
                                        nsMathMLContainerFrame* aFrame,
                                        nscoord              aUserSubScriptShift,
                                        nscoord              aUserSupScriptShift,
                                        nscoord              aScriptSpace)
{
  // force the scriptSpace to be atleast 1 pixel
  nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
  aScriptSpace = NS_MAX(onePixel, aScriptSpace);

  ////////////////////////////////////
  // Get the children's desired sizes

  nsHTMLReflowMetrics baseSize;
  nsHTMLReflowMetrics subScriptSize;
  nsHTMLReflowMetrics supScriptSize;
  nsBoundingMetrics bmBase, bmSubScript, bmSupScript;
  nsIFrame* subScriptFrame = nsnull;
  nsIFrame* supScriptFrame = nsnull;
  nsIFrame* baseFrame = aFrame->GetFirstPrincipalChild();
  if (baseFrame)
    subScriptFrame = baseFrame->GetNextSibling();
  if (subScriptFrame)
    supScriptFrame = subScriptFrame->GetNextSibling();
  if (!baseFrame || !subScriptFrame || !supScriptFrame ||
      supScriptFrame->GetNextSibling()) {
    // report an error, encourage people to get their markups in order
    return aFrame->ReflowError(aRenderingContext, aDesiredSize);
  }
  GetReflowAndBoundingMetricsFor(baseFrame, baseSize, bmBase);
  GetReflowAndBoundingMetricsFor(subScriptFrame, subScriptSize, bmSubScript);
  GetReflowAndBoundingMetricsFor(supScriptFrame, supScriptSize, bmSupScript);

  // get the subdrop from the subscript font
  nscoord subDrop;
  GetSubDropFromChild(subScriptFrame, subDrop);
  // parameter v, Rule 18a, App. G, TeXbook
  nscoord minSubScriptShift = bmBase.descent + subDrop;

  // get the supdrop from the supscript font
  nscoord supDrop;
  GetSupDropFromChild(supScriptFrame, supDrop);
  // parameter u, Rule 18a, App. G, TeXbook
  nscoord minSupScriptShift = bmBase.ascent - supDrop;

  //////////////////
  // Place Children
  //////////////////

  //////////////////////////////////////////////////
  // Get subscript shift
  // slightly different from nsMathMLmsubFrame.cpp
  //////////////////////////////////////////////////

  // subScriptShift{1,2}
  // = minimum amount to shift the subscript down
  // = sub{1,2} in TeXbook
  // subScriptShift1 = subscriptshift attribute * x-height
  nscoord subScriptShift1, subScriptShift2;

  nsRefPtr<nsFontMetrics> fm;
  nsLayoutUtils::GetFontMetricsForFrame(baseFrame, getter_AddRefs(fm));
  aRenderingContext.SetFont(fm);

  // get x-height (an ex)
  nscoord xHeight = fm->XHeight();

  nscoord ruleSize;
  GetRuleThickness (aRenderingContext, fm, ruleSize);

  // Get subScriptShift{1,2} default from font
  GetSubScriptShifts (fm, subScriptShift1, subScriptShift2);

  if (0 < aUserSubScriptShift) {
    // the user has set the subscriptshift attribute
    float scaler = ((float) subScriptShift2) / subScriptShift1;
    subScriptShift1 = NS_MAX(subScriptShift1, aUserSubScriptShift);
    subScriptShift2 = NSToCoordRound(scaler * subScriptShift1);
  }

  // get a tentative value for subscriptshift
  // Rule 18d, App. G, TeXbook
  nscoord subScriptShift =
    NS_MAX(minSubScriptShift,NS_MAX(subScriptShift1,subScriptShift2));

  //////////////////////////////////////////////////
  // Get supscript shift
  // same code from nsMathMLmsupFrame.cpp
  //////////////////////////////////////////////////

  // get min supscript shift limit from x-height
  // = d(x) + 1/4 * sigma_5, Rule 18c, App. G, TeXbook
  nscoord minShiftFromXHeight = (nscoord)
    (bmSupScript.descent + (1.0f/4.0f) * xHeight);
//.........这里部分代码省略.........

// NOTE: aDesiredStretchSize is an IN/OUT parameter
//       On input  - it contains our current size
//       On output - the same size or the new size that we want
NS_IMETHODIMP
nsMathMLmoFrame::Stretch(nsRenderingContext& aRenderingContext,
                         nsStretchDirection   aStretchDirection,
                         nsBoundingMetrics&   aContainerSize,
                         nsHTMLReflowMetrics& aDesiredStretchSize)
{
  if (NS_MATHML_STRETCH_WAS_DONE(mPresentationData.flags)) {
    NS_WARNING("it is wrong to fire stretch more than once on a frame");
    return NS_OK;
  }
  mPresentationData.flags |= NS_MATHML_STRETCH_DONE;

  nsIFrame* firstChild = mFrames.FirstChild();

  // get the axis height;
  nsRefPtr<nsFontMetrics> fm;
  nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm));
  aRenderingContext.SetFont(fm);
  nscoord axisHeight, height;
  GetAxisHeight(aRenderingContext, fm, axisHeight);

  // get the leading to be left at the top and the bottom of the stretched char
  // this seems more reliable than using fm->GetLeading() on suspicious fonts
  nscoord em;
  GetEmHeight(fm, em);
  nscoord leading = NSToCoordRound(0.2f * em);

  // Operators that are stretchy, or those that are to be centered
  // to cater for fonts that are not math-aware, are handled by the MathMLChar
  // ('form' is reset if stretch fails -- i.e., we don't bother to stretch next time)
  bool useMathMLChar = UseMathMLChar();

  nsBoundingMetrics charSize;
  nsBoundingMetrics container = aDesiredStretchSize.mBoundingMetrics;
  bool isVertical = false;

  if (((aStretchDirection == NS_STRETCH_DIRECTION_VERTICAL) ||
       (aStretchDirection == NS_STRETCH_DIRECTION_DEFAULT))  &&
      (mEmbellishData.direction == NS_STRETCH_DIRECTION_VERTICAL)) {
    isVertical = true;
  }

  uint32_t stretchHint =
    GetStretchHint(mFlags, mPresentationData, isVertical);

  if (useMathMLChar) {
    nsBoundingMetrics initialSize = aDesiredStretchSize.mBoundingMetrics;

    if (stretchHint != NS_STRETCH_NONE) {

      container = aContainerSize;

      // some adjustments if the operator is symmetric and vertical

      if (isVertical && NS_MATHML_OPERATOR_IS_SYMMETRIC(mFlags)) {
        // we need to center about the axis
        nscoord delta = std::max(container.ascent - axisHeight,
                               container.descent + axisHeight);
        container.ascent = delta + axisHeight;
        container.descent = delta - axisHeight;

        // get ready in case we encounter user-desired min-max size
        delta = std::max(initialSize.ascent - axisHeight,
                       initialSize.descent + axisHeight);
        initialSize.ascent = delta + axisHeight;
        initialSize.descent = delta - axisHeight;
      }

      // check for user-desired min-max size

      if (mMaxSize != NS_MATHML_OPERATOR_SIZE_INFINITY && mMaxSize > 0.0f) {
        // if we are here, there is a user defined maxsize ...
        //XXX Set stretchHint = NS_STRETCH_NORMAL? to honor the maxsize as close as possible?
        if (NS_MATHML_OPERATOR_MAXSIZE_IS_ABSOLUTE(mFlags)) {
          // there is an explicit value like maxsize="20pt"
          // try to maintain the aspect ratio of the char
          float aspect = mMaxSize / float(initialSize.ascent + initialSize.descent);
          container.ascent =
            std::min(container.ascent, nscoord(initialSize.ascent * aspect));
          container.descent =
            std::min(container.descent, nscoord(initialSize.descent * aspect));
          // below we use a type cast instead of a conversion to avoid a VC++ bug
          // see http://support.microsoft.com/support/kb/articles/Q115/7/05.ASP
          container.width =
            std::min(container.width, (nscoord)mMaxSize);
        }
        else { // multiplicative value
          container.ascent =
            std::min(container.ascent, nscoord(initialSize.ascent * mMaxSize));
          container.descent =
            std::min(container.descent, nscoord(initialSize.descent * mMaxSize));
          container.width =
            std::min(container.width, nscoord(initialSize.width * mMaxSize));
        }

        if (isVertical && !NS_MATHML_OPERATOR_IS_SYMMETRIC(mFlags)) {
          // re-adjust to align the char with the bottom of the initial container
//.........这里部分代码省略.........

/* virtual */ nsresult
nsMathMLmmultiscriptsFrame::Place(nsRenderingContext& aRenderingContext,
                                  bool                 aPlaceOrigin,
                                  nsHTMLReflowMetrics& aDesiredSize)
{
  ////////////////////////////////////
  // Get the children's desired sizes

  nscoord minShiftFromXHeight, subDrop, supDrop;

  ////////////////////////////////////////
  // Initialize super/sub shifts that
  // depend only on the current font
  ////////////////////////////////////////

  ProcessAttributes();

  // get x-height (an ex)
  const nsStyleFont* font = GetStyleFont();
  nsRefPtr<nsFontMetrics> fm;
  nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm));
  aRenderingContext.SetFont(fm);

  nscoord xHeight = fm->XHeight();

  nscoord ruleSize;
  GetRuleThickness (aRenderingContext, fm, ruleSize);

  // scriptspace from TeX for extra spacing after sup/subscript (0.5pt in plain TeX)
  // forced to be at least 1 pixel here
  nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
  nscoord scriptSpace = NS_MAX(nsPresContext::CSSPointsToAppUnits(0.5f), onePixel);

  /////////////////////////////////////
  // first the shift for the subscript

  // subScriptShift{1,2}
  // = minimum amount to shift the subscript down
  // = sub{1,2} in TeXbook
  // subScriptShift1 = subscriptshift attribute * x-height
  nscoord subScriptShift1, subScriptShift2;

  // Get subScriptShift{1,2} default from font
  GetSubScriptShifts (fm, subScriptShift1, subScriptShift2);
  if (0 < mSubScriptShift) {
    // the user has set the subscriptshift attribute
    float scaler = ((float) subScriptShift2) / subScriptShift1;
    subScriptShift1 = NS_MAX(subScriptShift1, mSubScriptShift);
    subScriptShift2 = NSToCoordRound(scaler * subScriptShift1);
  }
  // the font dependent shift
  nscoord subScriptShift = NS_MAX(subScriptShift1,subScriptShift2);

  /////////////////////////////////////
  // next the shift for the superscript

  // supScriptShift{1,2,3}
  // = minimum amount to shift the supscript up
  // = sup{1,2,3} in TeX
  // supScriptShift1 = superscriptshift attribute * x-height
  // Note that there are THREE values for supscript shifts depending
  // on the current style
  nscoord supScriptShift1, supScriptShift2, supScriptShift3;
  // Set supScriptShift{1,2,3} default from font
  GetSupScriptShifts (fm, supScriptShift1, supScriptShift2, supScriptShift3);
  if (0 < mSupScriptShift) {
    // the user has set the superscriptshift attribute
    float scaler2 = ((float) supScriptShift2) / supScriptShift1;
    float scaler3 = ((float) supScriptShift3) / supScriptShift1;
    supScriptShift1 = NS_MAX(supScriptShift1, mSupScriptShift);
    supScriptShift2 = NSToCoordRound(scaler2 * supScriptShift1);
    supScriptShift3 = NSToCoordRound(scaler3 * supScriptShift1);
  }

  // get sup script shift depending on current script level and display style
  // Rule 18c, App. G, TeXbook
  nscoord supScriptShift;
  if ( font->mScriptLevel == 0 &&
       NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags) &&
      !NS_MATHML_IS_COMPRESSED(mPresentationData.flags)) {
    // Style D in TeXbook
    supScriptShift = supScriptShift1;
  }
  else if (NS_MATHML_IS_COMPRESSED(mPresentationData.flags)) {
    // Style C' in TeXbook = D',T',S',SS'
    supScriptShift = supScriptShift3;
  }
  else {
    // everything else = T,S,SS
    supScriptShift = supScriptShift2;
  }

  ////////////////////////////////////
  // Get the children's sizes
  ////////////////////////////////////

  nscoord width = 0, prescriptsWidth = 0, rightBearing = 0;
  nsIFrame* mprescriptsFrame = nsnull; // frame of <mprescripts/>, if there.
  bool isSubScript = false;
  nscoord minSubScriptShift = 0, minSupScriptShift = 0;
//.........这里部分代码省略.........

nsresult
nsMathMLmfracFrame::PlaceInternal(nsRenderingContext& aRenderingContext,
                                  bool                 aPlaceOrigin,
                                  nsHTMLReflowMetrics& aDesiredSize,
                                  bool                 aWidthOnly)
{
  ////////////////////////////////////
  // Get the children's desired sizes
  nsBoundingMetrics bmNum, bmDen;
  nsHTMLReflowMetrics sizeNum;
  nsHTMLReflowMetrics sizeDen;
  nsIFrame* frameDen = nsnull;
  nsIFrame* frameNum = mFrames.FirstChild();
  if (frameNum) 
    frameDen = frameNum->GetNextSibling();
  if (!frameNum || !frameDen || frameDen->GetNextSibling()) {
    // report an error, encourage people to get their markups in order
    return ReflowError(aRenderingContext, aDesiredSize);
  }
  GetReflowAndBoundingMetricsFor(frameNum, sizeNum, bmNum);
  GetReflowAndBoundingMetricsFor(frameDen, sizeDen, bmDen);

  nsPresContext* presContext = PresContext();
  nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);

  nsRefPtr<nsFontMetrics> fm;
  nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm));
  aRenderingContext.SetFont(fm);

  nscoord defaultRuleThickness, axisHeight;
  GetRuleThickness(aRenderingContext, fm, defaultRuleThickness);
  GetAxisHeight(aRenderingContext, fm, axisHeight);

  nsEmbellishData coreData;
  GetEmbellishDataFrom(mEmbellishData.coreFrame, coreData);

  // see if the linethickness attribute is there 
  nsAutoString value;
  GetAttribute(mContent, mPresentationData.mstyle, nsGkAtoms::linethickness_,
               value);

  mLineThickness = CalcLineThickness(presContext, mStyleContext, value,
                                     onePixel, defaultRuleThickness);

  // bevelled attribute
  GetAttribute(mContent, mPresentationData.mstyle, nsGkAtoms::bevelled_,
               value);
  mIsBevelled = value.EqualsLiteral("true");

  if (!mIsBevelled) {
    mLineRect.height = mLineThickness;
    
    // by default, leave at least one-pixel padding at either end, or use
    // lspace & rspace that may come from <mo> if we are an embellished
    // container (we fetch values from the core since they may use units that
    // depend on style data, and style changes could have occurred in the
    // core since our last visit there)
    nscoord leftSpace = NS_MAX(onePixel, coreData.leftSpace);
    nscoord rightSpace = NS_MAX(onePixel, coreData.rightSpace);

    //////////////////
    // Get shifts
    nscoord numShift = 0;
    nscoord denShift = 0;

    // Rule 15b, App. G, TeXbook
    nscoord numShift1, numShift2, numShift3;
    nscoord denShift1, denShift2;

    GetNumeratorShifts(fm, numShift1, numShift2, numShift3);
    GetDenominatorShifts(fm, denShift1, denShift2);
    if (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) {
      // C > T
      numShift = numShift1;
      denShift = denShift1;
    }
    else {
      numShift = (0 < mLineRect.height) ? numShift2 : numShift3;
      denShift = denShift2;
    }

    nscoord minClearance = 0;
    nscoord actualClearance = 0;

    nscoord actualRuleThickness =  mLineThickness;

    if (0 == actualRuleThickness) {
      // Rule 15c, App. G, TeXbook

      // min clearance between numerator and denominator
      minClearance = (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) ?
        7 * defaultRuleThickness : 3 * defaultRuleThickness;
      actualClearance =
        (numShift - bmNum.descent) - (bmDen.ascent - denShift);
      // actualClearance should be >= minClearance
      if (actualClearance < minClearance) {
        nscoord halfGap = (minClearance - actualClearance)/2;
        numShift += halfGap;
        denShift += halfGap;
      }
//.........这里部分代码省略.........

/* virtual */ nsresult
nsMathMLmencloseFrame::PlaceInternal(nsRenderingContext& aRenderingContext,
                                     bool                 aPlaceOrigin,
                                     nsHTMLReflowMetrics& aDesiredSize,
                                     bool                 aWidthOnly)
{
  ///////////////
  // Measure the size of our content using the base class to format like an
  // inferred mrow.
  nsHTMLReflowMetrics baseSize;
  nsresult rv =
    nsMathMLContainerFrame::Place(aRenderingContext, false, baseSize);

  if (NS_MATHML_HAS_ERROR(mPresentationData.flags) || NS_FAILED(rv)) {
      DidReflowChildren(GetFirstPrincipalChild());
      return rv;
    }

  nsBoundingMetrics bmBase = baseSize.mBoundingMetrics;
  nscoord dx_left = 0, dx_right = 0;
  nsBoundingMetrics bmLongdivChar, bmRadicalChar;
  nscoord radicalAscent = 0, radicalDescent = 0;
  nscoord longdivAscent = 0, longdivDescent = 0;
  nscoord psi = 0;

  ///////////////
  // Thickness of bars and font metrics
  nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);

  nscoord mEmHeight;
  nsRefPtr<nsFontMetrics> fm;
  nsLayoutUtils::GetFontMetricsForFrame(this, getter_AddRefs(fm));
  aRenderingContext.SetFont(fm);
  GetRuleThickness(aRenderingContext, fm, mRuleThickness);
  GetEmHeight(fm, mEmHeight);

  PRUnichar one = '1';
  nsBoundingMetrics bmOne = aRenderingContext.GetBoundingMetrics(&one, 1);

  ///////////////
  // General rules: the menclose element takes the size of the enclosed content.
  // We add a padding when needed.

  // determine padding & psi
  nscoord padding = 3 * mRuleThickness;
  nscoord delta = padding % onePixel;
  if (delta)
    padding += onePixel - delta; // round up

  if (IsToDraw(NOTATION_LONGDIV) || IsToDraw(NOTATION_RADICAL)) {
      nscoord phi;
      // Rule 11, App. G, TeXbook
      // psi = clearance between rule and content
      if (NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags))
        phi = fm->XHeight();
      else
        phi = mRuleThickness;
      psi = mRuleThickness + phi / 4;

      delta = psi % onePixel;
      if (delta)
        psi += onePixel - delta; // round up
    }

  if (mRuleThickness < onePixel)
    mRuleThickness = onePixel;
 
  // Set horizontal parameters
  if (IsToDraw(NOTATION_ROUNDEDBOX) ||
      IsToDraw(NOTATION_TOP) ||
      IsToDraw(NOTATION_LEFT) ||
      IsToDraw(NOTATION_BOTTOM) ||
      IsToDraw(NOTATION_CIRCLE))
    dx_left = padding;

  if (IsToDraw(NOTATION_ROUNDEDBOX) ||
      IsToDraw(NOTATION_TOP) ||
      IsToDraw(NOTATION_RIGHT) ||
      IsToDraw(NOTATION_BOTTOM) ||
      IsToDraw(NOTATION_CIRCLE))
    dx_right = padding;

  // Set vertical parameters
  if (IsToDraw(NOTATION_RIGHT) ||
      IsToDraw(NOTATION_LEFT) ||
      IsToDraw(NOTATION_UPDIAGONALSTRIKE) ||
      IsToDraw(NOTATION_DOWNDIAGONALSTRIKE) ||
      IsToDraw(NOTATION_VERTICALSTRIKE) ||
      IsToDraw(NOTATION_CIRCLE) ||
      IsToDraw(NOTATION_ROUNDEDBOX) ||
      IsToDraw(NOTATION_RADICAL) ||
      IsToDraw(NOTATION_LONGDIV)) {
      // set a minimal value for the base height
      bmBase.ascent = NS_MAX(bmOne.ascent, bmBase.ascent);
      bmBase.descent = NS_MAX(0, bmBase.descent);
  }

  mBoundingMetrics.ascent = bmBase.ascent;
  mBoundingMetrics.descent = bmBase.descent;
    
//.........这里部分代码省略.........

// exported routine that both munderover and mmultiscripts share.
// munderover uses this when movablelimits is set.
nsresult
nsMathMLmmultiscriptsFrame::PlaceMultiScript(nsPresContext*      aPresContext,
                                        nsRenderingContext& aRenderingContext,
                                        bool                 aPlaceOrigin,
                                        nsHTMLReflowMetrics& aDesiredSize,
                                        nsMathMLContainerFrame* aFrame,
                                        nscoord              aUserSubScriptShift,
                                        nscoord              aUserSupScriptShift,
                                        nscoord              aScriptSpace)
{
  nsIAtom* tag = aFrame->GetContent()->Tag();

  // This function deals with both munderover etc. as well as msubsup etc.
  // As the former behaves identically to the later, we treat it as such
  // to avoid additional checks later.
  if (tag == nsGkAtoms::mover_)
    tag = nsGkAtoms::msup_;
  else if (tag == nsGkAtoms::munder_)
    tag = nsGkAtoms::msub_;
  else if (tag  == nsGkAtoms::munderover_)
    tag = nsGkAtoms::msubsup_;

  nsBoundingMetrics bmFrame;

  nscoord minShiftFromXHeight, subDrop, supDrop;

  ////////////////////////////////////////
  // Initialize super/sub shifts that
  // depend only on the current font
  ////////////////////////////////////////

  nsIFrame* baseFrame = aFrame->GetFirstPrincipalChild();

  if (!baseFrame) {
    if (tag == nsGkAtoms::mmultiscripts_)
      aFrame->ReportErrorToConsole("NoBase");
    else
      aFrame->ReportChildCountError();
    return aFrame->ReflowError(aRenderingContext, aDesiredSize);
  }


  // get x-height (an ex)
  const nsStyleFont* font = aFrame->StyleFont();
  nsRefPtr<nsFontMetrics> fm;
  nsLayoutUtils::GetFontMetricsForFrame(baseFrame, getter_AddRefs(fm));
  aRenderingContext.SetFont(fm);

  nscoord xHeight = fm->XHeight();

  nscoord ruleSize;
  GetRuleThickness (aRenderingContext, fm, ruleSize);

  // force the scriptSpace to be at least 1 pixel
  nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
  aScriptSpace = std::max(onePixel, aScriptSpace);

  /////////////////////////////////////
  // first the shift for the subscript

  // subScriptShift{1,2}
  // = minimum amount to shift the subscript down
  // = sub{1,2} in TeXbook
  // subScriptShift1 = subscriptshift attribute * x-height
  nscoord subScriptShift1, subScriptShift2;

  // Get subScriptShift{1,2} default from font
  GetSubScriptShifts (fm, subScriptShift1, subScriptShift2);
  nscoord subScriptShift;
  if (tag == nsGkAtoms::msub_) {
    subScriptShift = subScriptShift1;
  } else {
    subScriptShift = std::max(subScriptShift1, subScriptShift2);
  }
  if (0 < aUserSubScriptShift) {
    // the user has set the subscriptshift attribute
    subScriptShift = std::max(subScriptShift, aUserSubScriptShift);
  }

  /////////////////////////////////////
  // next the shift for the superscript

  // supScriptShift{1,2,3}
  // = minimum amount to shift the supscript up
  // = sup{1,2,3} in TeX
  // supScriptShift1 = superscriptshift attribute * x-height
  // Note that there are THREE values for supscript shifts depending
  // on the current style
  nscoord supScriptShift1, supScriptShift2, supScriptShift3;
  // Set supScriptShift{1,2,3} default from font
  GetSupScriptShifts (fm, supScriptShift1, supScriptShift2, supScriptShift3);

  // get sup script shift depending on current script level and display style
  // Rule 18c, App. G, TeXbook
  nsPresentationData presentationData;
  aFrame->GetPresentationData(presentationData);
  nscoord supScriptShift;
  if (font->mScriptLevel == 0 &&
//.........这里部分代码省略.........