C++ nsRenderingContext::GetBoundingMetrics方法代码示例

/* static */ void
nsMathMLFrame::GetRuleThickness(nsRenderingContext& aRenderingContext,
                                nsFontMetrics*      aFontMetrics,
                                nscoord&             aRuleThickness)
{
  // get the bounding metrics of the overbar char, the rendering context
  // is assumed to have been set with the font of the current style context
  NS_ASSERTION(aRenderingContext.FontMetrics()->Font().
               Equals(aFontMetrics->Font()),
               "unexpected state");

  nscoord xHeight = aFontMetrics->XHeight();
  PRUnichar overBar = 0x00AF;
  nsBoundingMetrics bm = aRenderingContext.GetBoundingMetrics(&overBar, 1);
  aRuleThickness = bm.ascent + bm.descent;
  if (aRuleThickness <= 0 || aRuleThickness >= xHeight) {
    // fall-back to the other version
    GetRuleThickness(aFontMetrics, aRuleThickness);
  }
}

// helper functions to perform the common task of formatting our chars
/*static*/ nsresult
nsMathMLmfencedFrame::ReflowChar(nsPresContext*      aPresContext,
                                 nsRenderingContext& aRenderingContext,
                                 nsMathMLChar*        aMathMLChar,
                                 nsOperatorFlags      aForm,
                                 PRInt32              aScriptLevel,
                                 nscoord              axisHeight,
                                 nscoord              leading,
                                 nscoord              em,
                                 nsBoundingMetrics&   aContainerSize,
                                 nscoord&             aAscent,
                                 nscoord&             aDescent)
{
  if (aMathMLChar && 0 < aMathMLChar->Length()) {
    nscoord leftSpace;
    nscoord rightSpace;
    GetCharSpacing(aMathMLChar, aForm, aScriptLevel, em, leftSpace, rightSpace);

    // stretch the char to the appropriate height if it is not big enough.
    nsBoundingMetrics charSize;
    nsresult res = aMathMLChar->Stretch(aPresContext, aRenderingContext,
                                        NS_STRETCH_DIRECTION_VERTICAL,
                                        aContainerSize, charSize);

    if (NS_STRETCH_DIRECTION_UNSUPPORTED != aMathMLChar->GetStretchDirection()) {
      // has changed... so center the char around the axis
      nscoord height = charSize.ascent + charSize.descent;
      charSize.ascent = height/2 + axisHeight;
      charSize.descent = height - charSize.ascent;
    }
    else {
      // either it hasn't changed or stretching the char failed (i.e.,
      // GetBoundingMetrics failed)
      leading = 0;
      if (NS_FAILED(res)) {
        nsAutoString data;
        aMathMLChar->GetData(data);
        nsBoundingMetrics metrics =
          aRenderingContext.GetBoundingMetrics(data.get(), data.Length());
        charSize.ascent = metrics.ascent;
        charSize.descent = metrics.descent;
        charSize.width = metrics.width;
        // Set this as the bounding metrics of the MathMLChar to leave
        // the necessary room to paint the char.
        aMathMLChar->SetBoundingMetrics(charSize);
      }
    }

    if (aAscent < charSize.ascent + leading) 
      aAscent = charSize.ascent + leading;
    if (aDescent < charSize.descent + leading) 
      aDescent = charSize.descent + leading;

    // account the spacing
    charSize.width += leftSpace + rightSpace;

    // x-origin is used to store lspace ...
    // y-origin is used to stored the ascent ... 
    aMathMLChar->SetRect(nsRect(leftSpace, 
                                charSize.ascent, charSize.width,
                                charSize.ascent + charSize.descent));
  }
  return NS_OK;
}

/* 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.........