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);
}

void DefaultArea::Draw(nsIFrame* aFrame, nsRenderingContext& aRC)
{
  if (mHasFocus) {
    nsRect r = aFrame->GetRect();
    r.MoveTo(0, 0);
    nscoord x1 = r.x;
    nscoord y1 = r.y;
    const nscoord kOnePixel = nsPresContext::CSSPixelsToAppUnits(1);
    nscoord x2 = r.XMost() - kOnePixel;
    nscoord y2 = r.YMost() - kOnePixel;
    // XXX aRC.DrawRect(r) result is ugly, that's why we use DrawLine.
    aRC.DrawLine(x1, y1, x1, y2);
    aRC.DrawLine(x1, y2, x2, y2);
    aRC.DrawLine(x1, y1, x2, y1);
    aRC.DrawLine(x2, y1, x2, y2);
  }
}

//------------------------------------------------------------------------------
void
nsSimplePageSequenceFrame::PaintPageSequence(nsRenderingContext& aRenderingContext,
                                             const nsRect&        aDirtyRect,
                                             nsPoint              aPt) {
  nsRect rect = aDirtyRect;
  float scale = PresContext()->GetPrintPreviewScale();
  aRenderingContext.PushState();
  nsPoint framePos = aPt;
  aRenderingContext.Translate(framePos);
  rect -= framePos;
  aRenderingContext.Scale(scale, scale);
  rect.ScaleRoundOut(1.0f / scale);

  // Now the rect and the rendering coordinates are are relative to this frame.
  // Loop over the pages and paint them.
  nsIFrame* child = GetFirstChild(nsnull);
  while (child) {
    nsPoint pt = child->GetPosition();
    // The rendering context has to be translated before each call to PaintFrame
    aRenderingContext.PushState();
    aRenderingContext.Translate(pt);
    nsLayoutUtils::PaintFrame(&aRenderingContext, child,
                              nsRegion(rect - pt), NS_RGBA(0,0,0,0),
                              nsLayoutUtils::PAINT_SYNC_DECODE_IMAGES);
    aRenderingContext.PopState();
    child = child->GetNextSibling();
  }

  aRenderingContext.PopState();
}

/* 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);
  }
}

void
nsTableCellFrame::DecorateForSelection(nsRenderingContext& aRenderingContext,
                                       nsPoint aPt)
{
  NS_ASSERTION(GetStateBits() & NS_FRAME_SELECTED_CONTENT,
               "Should only be called for selected cells");
  PRInt16 displaySelection;
  nsPresContext* presContext = PresContext();
  displaySelection = DisplaySelection(presContext);
  if (displaySelection) {
    nsRefPtr<nsFrameSelection> frameSelection =
      presContext->PresShell()->FrameSelection();

    if (frameSelection->GetTableCellSelection()) {
      nscolor       bordercolor;
      if (displaySelection == nsISelectionController::SELECTION_DISABLED) {
        bordercolor = NS_RGB(176,176,176);// disabled color
      }
      else {
        bordercolor =
          LookAndFeel::GetColor(LookAndFeel::eColorID_TextSelectBackground);
      }
      nscoord threePx = nsPresContext::CSSPixelsToAppUnits(3);
      if ((mRect.width > threePx) && (mRect.height > threePx))
      {
        //compare bordercolor to ((nsStyleColor *)myColor)->mBackgroundColor)
        bordercolor = EnsureDifferentColors(bordercolor,
                                            GetStyleBackground()->mBackgroundColor);
        nsRenderingContext::AutoPushTranslation
            translate(&aRenderingContext, aPt);
        nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);

        aRenderingContext.SetColor(bordercolor);
        aRenderingContext.DrawLine(onePixel, 0, mRect.width, 0);
        aRenderingContext.DrawLine(0, onePixel, 0, mRect.height);
        aRenderingContext.DrawLine(onePixel, mRect.height, mRect.width, mRect.height);
        aRenderingContext.DrawLine(mRect.width, onePixel, mRect.width, mRect.height);
        //middle
        aRenderingContext.DrawRect(onePixel, onePixel, mRect.width-onePixel,
                                   mRect.height-onePixel);
        //shading
        aRenderingContext.DrawLine(2*onePixel, mRect.height-2*onePixel,
                                   mRect.width-onePixel, mRect.height- (2*onePixel));
        aRenderingContext.DrawLine(mRect.width - (2*onePixel), 2*onePixel,
                                   mRect.width - (2*onePixel), mRect.height-onePixel);
      }
    }
  }
}

// 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.........

DrawResult
nsFieldSetFrame::PaintBorderBackground(
  nsDisplayListBuilder* aBuilder,
  nsRenderingContext& aRenderingContext,
  nsPoint aPt,
  const nsRect& aDirtyRect)
{
  // if the border is smaller than the legend. Move the border down
  // to be centered on the legend.
  // FIXME: This means border-radius clamping is incorrect; we should
  // override nsIFrame::GetBorderRadii.
  WritingMode wm = GetWritingMode();
  nsRect rect = VisualBorderRectRelativeToSelf();
  nscoord off = wm.IsVertical() ? rect.x : rect.y;
  rect += aPt;
  nsPresContext* presContext = PresContext();

  uint32_t bgFlags = aBuilder->GetBackgroundPaintFlags();
  PaintBorderFlags borderFlags = aBuilder->ShouldSyncDecodeImages()
                               ? PaintBorderFlags::SYNC_DECODE_IMAGES
                               : PaintBorderFlags();

  DrawResult result =
    nsCSSRendering::PaintBackground(presContext, aRenderingContext, this,
                                    aDirtyRect, rect, bgFlags);

  nsCSSRendering::PaintBoxShadowInner(presContext, aRenderingContext,
                                      this, rect, aDirtyRect);

  if (nsIFrame* legend = GetLegend()) {
    css::Side legendSide = wm.PhysicalSide(eLogicalSideBStart);
    nscoord legendBorderWidth =
      StyleBorder()->GetComputedBorderWidth(legendSide);

    // Use the rect of the legend frame, not mLegendRect, so we draw our
    // border under the legend's inline-start and -end margins.
    LogicalRect legendRect(wm, legend->GetRect() + aPt, rect.Size());

    // Compute clipRect using logical coordinates, so that the legend space
    // will be clipped out of the appropriate physical side depending on mode.
    LogicalRect clipRect = LogicalRect(wm, rect, rect.Size());
    DrawTarget* drawTarget = aRenderingContext.GetDrawTarget();
    gfxContext* gfx = aRenderingContext.ThebesContext();
    int32_t appUnitsPerDevPixel = presContext->AppUnitsPerDevPixel();

    // draw inline-start portion of the block-start side of the border
    clipRect.ISize(wm) = legendRect.IStart(wm) - clipRect.IStart(wm);
    clipRect.BSize(wm) = legendBorderWidth;

    gfx->Save();
    gfx->Clip(NSRectToSnappedRect(clipRect.GetPhysicalRect(wm, rect.Size()),
                                  appUnitsPerDevPixel, *drawTarget));
    result &=
      nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                  aDirtyRect, rect, mStyleContext, borderFlags);
    gfx->Restore();

    // draw inline-end portion of the block-start side of the border
    clipRect = LogicalRect(wm, rect, rect.Size());
    clipRect.ISize(wm) = clipRect.IEnd(wm) - legendRect.IEnd(wm);
    clipRect.IStart(wm) = legendRect.IEnd(wm);
    clipRect.BSize(wm) = legendBorderWidth;

    gfx->Save();
    gfx->Clip(NSRectToSnappedRect(clipRect.GetPhysicalRect(wm, rect.Size()),
                                  appUnitsPerDevPixel, *drawTarget));
    result &=
      nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                  aDirtyRect, rect, mStyleContext, borderFlags);
    gfx->Restore();

    // draw remainder of the border (omitting the block-start side)
    clipRect = LogicalRect(wm, rect, rect.Size());
    clipRect.BStart(wm) += legendBorderWidth;
    clipRect.BSize(wm) = BSize(wm) - (off + legendBorderWidth);

    gfx->Save();
    gfx->Clip(NSRectToSnappedRect(clipRect.GetPhysicalRect(wm, rect.Size()),
                                  appUnitsPerDevPixel, *drawTarget));
    result &=
      nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                  aDirtyRect, rect, mStyleContext, borderFlags);
    gfx->Restore();
  } else {
    result &=
      nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                  aDirtyRect, nsRect(aPt, mRect.Size()),
                                  mStyleContext, borderFlags);
  }

  return result;
}

// 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.........

DrawResult
nsImageBoxFrame::PaintImage(nsRenderingContext& aRenderingContext,
                            const nsRect& aDirtyRect, nsPoint aPt,
                            uint32_t aFlags)
{
  nsRect constraintRect;
  GetClientRect(constraintRect);

  constraintRect += aPt;

  if (!mImageRequest) {
    // This probably means we're drawn by a native theme.
    return DrawResult::SUCCESS;
  }

  // don't draw if the image is not dirty
  // XXX(seth): Can this actually happen anymore?
  nsRect dirty;
  if (!dirty.IntersectRect(aDirtyRect, constraintRect)) {
    return DrawResult::TEMPORARY_ERROR;
  }

  nsCOMPtr<imgIContainer> imgCon;
  mImageRequest->GetImage(getter_AddRefs(imgCon));

  if (!imgCon) {
    return DrawResult::NOT_READY;
  }

  bool hasSubRect = !mUseSrcAttr && (mSubRect.width > 0 || mSubRect.height > 0);

  Maybe<nsPoint> anchorPoint;
  nsRect dest;
  if (!mUseSrcAttr) {
    // Our image (if we have one) is coming from the CSS property
    // 'list-style-image' (combined with '-moz-image-region'). For now, ignore
    // 'object-fit' & 'object-position' in this case, and just fill our rect.
    // XXXdholbert Should we even honor these properties in this case? They only
    // apply to replaced elements, and I'm not sure we count as a replaced
    // element when our image data is determined by CSS.
    dest = constraintRect;
  } else {
    // Determine dest rect based on intrinsic size & ratio, along with
    // 'object-fit' & 'object-position' properties:
    IntrinsicSize intrinsicSize;
    nsSize intrinsicRatio;
    if (mIntrinsicSize.width > 0 && mIntrinsicSize.height > 0) {
      // Image has a valid size; use it as intrinsic size & ratio.
      intrinsicSize.width.SetCoordValue(mIntrinsicSize.width);
      intrinsicSize.height.SetCoordValue(mIntrinsicSize.height);
      intrinsicRatio = mIntrinsicSize;
    } else {
      // Image doesn't have a (valid) intrinsic size.
      // Try to look up intrinsic ratio and use that at least.
      imgCon->GetIntrinsicRatio(&intrinsicRatio);
    }
    anchorPoint.emplace();
    dest = nsLayoutUtils::ComputeObjectDestRect(constraintRect,
                                                intrinsicSize,
                                                intrinsicRatio,
                                                StylePosition(),
                                                anchorPoint.ptr());
  }


  return nsLayoutUtils::DrawSingleImage(
           *aRenderingContext.ThebesContext(),
           PresContext(), imgCon,
           nsLayoutUtils::GetGraphicsFilterForFrame(this),
           dest, dirty, nullptr, aFlags,
           anchorPoint.ptrOr(nullptr),
           hasSubRect ? &mSubRect : nullptr);
}

/* 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.........

DrawResult
nsGroupBoxFrame::PaintBorderBackground(nsRenderingContext& aRenderingContext,
    nsPoint aPt, const nsRect& aDirtyRect) {

  DrawTarget* drawTarget = aRenderingContext.GetDrawTarget();
  gfxContext* gfx = aRenderingContext.ThebesContext();

  Sides skipSides;
  const nsStyleBorder* borderStyleData = StyleBorder();
  const nsMargin& border = borderStyleData->GetComputedBorder();
  nscoord yoff = 0;
  nsPresContext* presContext = PresContext();

  nsRect groupRect;
  nsIFrame* groupBox = GetCaptionBox(presContext, groupRect);

  if (groupBox) {        
    // if the border is smaller than the legend. Move the border down
    // to be centered on the legend. 
    nsMargin groupMargin;
    groupBox->StyleMargin()->GetMargin(groupMargin);
    groupRect.Inflate(groupMargin);
 
    if (border.top < groupRect.height)
        yoff = (groupRect.height - border.top)/2 + groupRect.y;
  }

  nsRect rect(aPt.x, aPt.y + yoff, mRect.width, mRect.height - yoff);

  groupRect += aPt;

  DrawResult result =
    nsCSSRendering::PaintBackground(presContext, aRenderingContext, this,
                                    aDirtyRect, rect,
                                    nsCSSRendering::PAINTBG_SYNC_DECODE_IMAGES);

  if (groupBox) {
    int32_t appUnitsPerDevPixel = PresContext()->AppUnitsPerDevPixel();

    // we should probably use PaintBorderEdges to do this but for now just use clipping
    // to achieve the same effect.

    // draw left side
    nsRect clipRect(rect);
    clipRect.width = groupRect.x - rect.x;
    clipRect.height = border.top;

    gfx->Save();
    gfx->Clip(NSRectToSnappedRect(clipRect, appUnitsPerDevPixel, *drawTarget));
    result &=
      nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                  aDirtyRect, rect, mStyleContext,
                                  PaintBorderFlags::SYNC_DECODE_IMAGES, skipSides);
    gfx->Restore();

    // draw right side
    clipRect = rect;
    clipRect.x = groupRect.XMost();
    clipRect.width = rect.XMost() - groupRect.XMost();
    clipRect.height = border.top;

    gfx->Save();
    gfx->Clip(NSRectToSnappedRect(clipRect, appUnitsPerDevPixel, *drawTarget));
    result &=
      nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                  aDirtyRect, rect, mStyleContext,
                                  PaintBorderFlags::SYNC_DECODE_IMAGES, skipSides);
    gfx->Restore();
  
    // draw bottom

    clipRect = rect;
    clipRect.y += border.top;
    clipRect.height = mRect.height - (yoff + border.top);
  
    gfx->Save();
    gfx->Clip(NSRectToSnappedRect(clipRect, appUnitsPerDevPixel, *drawTarget));
    result &=
      nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                  aDirtyRect, rect, mStyleContext,
                                  PaintBorderFlags::SYNC_DECODE_IMAGES, skipSides);
    gfx->Restore();
    
  } else {
    result &=
      nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                  aDirtyRect, nsRect(aPt, GetSize()),
                                  mStyleContext,
                                  PaintBorderFlags::SYNC_DECODE_IMAGES, skipSides);
  }

  return result;
}

// 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;
}

// 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.........

void
nsFieldSetFrame::PaintBorderBackground(nsRenderingContext& aRenderingContext,
    nsPoint aPt, const nsRect& aDirtyRect, uint32_t aBGFlags)
{
  // if the border is smaller than the legend. Move the border down
  // to be centered on the legend. 
  // FIXME: This means border-radius clamping is incorrect; we should
  // override nsIFrame::GetBorderRadii.
  nsRect rect = VisualBorderRectRelativeToSelf();
  nscoord yoff = rect.y;
  rect += aPt;
  nsPresContext* presContext = PresContext();

  nsCSSRendering::PaintBackground(presContext, aRenderingContext, this,
                                  aDirtyRect, rect, aBGFlags);

  nsCSSRendering::PaintBoxShadowInner(presContext, aRenderingContext,
                                      this, rect, aDirtyRect);

   if (nsIFrame* legend = GetLegend()) {
     nscoord topBorder = StyleBorder()->GetComputedBorderWidth(NS_SIDE_TOP);

    // Use the rect of the legend frame, not mLegendRect, so we draw our
    // border under the legend's left and right margins.
    nsRect legendRect = legend->GetRect() + aPt;
    
    // we should probably use PaintBorderEdges to do this but for now just use clipping
    // to achieve the same effect.

    // draw left side
    nsRect clipRect(rect);
    clipRect.width = legendRect.x - rect.x;
    clipRect.height = topBorder;

    aRenderingContext.PushState();
    aRenderingContext.IntersectClip(clipRect);
    nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                aDirtyRect, rect, mStyleContext);

    aRenderingContext.PopState();


    // draw right side
    clipRect = rect;
    clipRect.x = legendRect.XMost();
    clipRect.width = rect.XMost() - legendRect.XMost();
    clipRect.height = topBorder;

    aRenderingContext.PushState();
    aRenderingContext.IntersectClip(clipRect);
    nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                aDirtyRect, rect, mStyleContext);

    aRenderingContext.PopState();

    
    // draw bottom
    clipRect = rect;
    clipRect.y += topBorder;
    clipRect.height = mRect.height - (yoff + topBorder);
    
    aRenderingContext.PushState();
    aRenderingContext.IntersectClip(clipRect);
    nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                aDirtyRect, rect, mStyleContext);

    aRenderingContext.PopState();
  } else {

    nsCSSRendering::PaintBorder(presContext, aRenderingContext, this,
                                aDirtyRect,
                                nsRect(aPt, mRect.Size()),
                                mStyleContext);
  }
}

nsresult
nsMathMLmfracFrame::PlaceInternal(nsRenderingContext& aRenderingContext,
                                  bool