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

/* static */ void
nsMathMLFrame::GetAxisHeight(nsIRenderingContext& aRenderingContext,
                             nsIFontMetrics*      aFontMetrics,
                             nscoord&             aAxisHeight)
{
  // get the bounding metrics of the minus sign, the rendering context
  // is assumed to have been set with the font of the current style context
#ifdef NS_DEBUG
  nsCOMPtr<nsIFontMetrics> currFontMetrics;
  aRenderingContext.GetFontMetrics(*getter_AddRefs(currFontMetrics));
  NS_ASSERTION(currFontMetrics->Font().Equals(aFontMetrics->Font()),
	"unexpected state");
#endif
  nscoord xHeight;
  aFontMetrics->GetXHeight(xHeight);
  PRUnichar minus = 0x2212; // not '-', but official Unicode minus sign
  nsBoundingMetrics bm;
  nsresult rv = aRenderingContext.GetBoundingMetrics(&minus, PRUint32(1), bm);
  if (NS_SUCCEEDED(rv)) {
    aAxisHeight = bm.ascent - (bm.ascent + bm.descent)/2;
  }
  if (NS_FAILED(rv) || aAxisHeight <= 0 || aAxisHeight >= xHeight) {
    // fall-back to the other version
    GetAxisHeight(aFontMetrics, aAxisHeight);
  }
}

/* static */ void
nsMathMLFrame::GetRuleThickness(nsIRenderingContext& aRenderingContext,
                                nsIFontMetrics*      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
#ifdef NS_DEBUG
  nsCOMPtr<nsIFontMetrics> currFontMetrics;
  aRenderingContext.GetFontMetrics(*getter_AddRefs(currFontMetrics));
  NS_ASSERTION(currFontMetrics->Font().Equals(aFontMetrics->Font()),
      "unexpected state");
#endif
  nscoord xHeight;
  aFontMetrics->GetXHeight(xHeight);
  PRUnichar overBar = 0x00AF;
  nsBoundingMetrics bm;
  nsresult rv = aRenderingContext.GetBoundingMetrics(&overBar, PRUint32(1), bm);
  if (NS_SUCCEEDED(rv)) {
    aRuleThickness = bm.ascent + bm.descent;
  }
  if (NS_FAILED(rv) || aRuleThickness <= 0 || aRuleThickness >= xHeight) {
    // fall-back to the other version
    GetRuleThickness(aFontMetrics, aRuleThickness);
  }

#if 0
  nscoord oldRuleThickness;
  GetRuleThickness(aFontMetrics, oldRuleThickness);

  PRUnichar sqrt = 0xE063; // a sqrt glyph from TeX's CMEX font
  rv = aRenderingContext.GetBoundingMetrics(&sqrt, PRUint32(1), bm);
  nscoord sqrtrule = bm.ascent; // according to TeX, the ascent should be the rule

  printf("xheight:%4d rule:%4d oldrule:%4d  sqrtrule:%4d\n",
          xHeight, aRuleThickness, oldRuleThickness, sqrtrule);
#endif
}

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

  if (NS_MATHML_HAS_ERROR(mPresentationData.flags) || NS_FAILED(rv)) {
      DidReflowChildren(GetFirstChild(nsnull));
      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);
  nsCOMPtr<nsIFontMetrics> fm;
  nscoord mEmHeight;
  aRenderingContext.SetFont(GetStyleFont()->mFont,
                            PresContext()->GetUserFontSet());
  aRenderingContext.GetFontMetrics(*getter_AddRefs(fm));
  GetRuleThickness(aRenderingContext, fm, mRuleThickness);
  GetEmHeight(fm, mEmHeight);

  nsBoundingMetrics bmOne;
  aRenderingContext.GetBoundingMetrics(NS_LITERAL_STRING("1").get(), 1, bmOne);

  ///////////////
  // 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))
        fm->GetXHeight(phi);
      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.........