C++ GlyphPage::glyphForCharacter方法代码示例

void SimpleFontData::platformGlyphInit()
{
    GlyphPage* glyphPageZero = GlyphPageTreeNode::getRootChild(this, 0)->page();
    if (!glyphPageZero) {
        WTF_LOG_ERROR("Failed to get glyph page zero.");
        m_spaceGlyph = 0;
        m_spaceWidth = 0;
        m_zeroGlyph = 0;
        m_adjustedSpaceWidth = 0;
        determinePitch();
        m_zeroWidthSpaceGlyph = 0;
        m_missingGlyphData.fontData = this;
        m_missingGlyphData.glyph = 0;
        return;
    }

    m_zeroWidthSpaceGlyph = glyphPageZero->glyphForCharacter(0);

    // Nasty hack to determine if we should round or ceil space widths.
    // If the font is monospace or fake monospace we ceil to ensure that
    // every character and the space are the same width.  Otherwise we round.
    m_spaceGlyph = glyphPageZero->glyphForCharacter(' ');
    float width = widthForGlyph(m_spaceGlyph);
    m_spaceWidth = width;
    m_zeroGlyph = glyphPageZero->glyphForCharacter('0');
    m_fontMetrics.setZeroWidth(widthForGlyph(m_zeroGlyph));
    determinePitch();
    m_adjustedSpaceWidth = m_treatAsFixedPitch ? ceilf(width) : roundf(width);

    // Force the glyph for ZERO WIDTH SPACE to have zero width, unless it is shared with SPACE.
    // Helvetica is an example of a non-zero width ZERO WIDTH SPACE glyph.
    // See <http://bugs.webkit.org/show_bug.cgi?id=13178>
    // Ask for the glyph for 0 to avoid paging in ZERO WIDTH SPACE. Control characters, including 0,
    // are mapped to the ZERO WIDTH SPACE glyph.
    if (m_zeroWidthSpaceGlyph == m_spaceGlyph) {
        m_zeroWidthSpaceGlyph = 0;
        WTF_LOG_ERROR("Font maps SPACE and ZERO WIDTH SPACE to the same glyph. Glyph width will not be overridden.");
    }

    m_missingGlyphData.fontData = this;
    m_missingGlyphData.glyph = 0;
}

// Estimates of avgCharWidth and maxCharWidth for platforms that don't support accessing these values from the font.
void SimpleFontData::initCharWidths()
{
    GlyphPage* glyphPageZero = GlyphPageTreeNode::getRootChild(this, 0)->page();

    // Treat the width of a '0' as the avgCharWidth.
    if (m_avgCharWidth <= 0.f && glyphPageZero) {
        static const UChar32 digitZeroChar = '0';
        Glyph digitZeroGlyph = glyphPageZero->glyphForCharacter(digitZeroChar);
        if (digitZeroGlyph)
            m_avgCharWidth = widthForGlyph(digitZeroGlyph);
    }

    // If we can't retrieve the width of a '0', fall back to the x height.
    if (m_avgCharWidth <= 0.f)
        m_avgCharWidth = m_fontMetrics.xHeight();

    if (m_maxCharWidth <= 0.f)
        m_maxCharWidth = max(m_avgCharWidth, m_fontMetrics.floatAscent());
}

//.........这里部分代码省略.........
      fastFree(vdmxTable);
    }
  }
#endif

  float ascent;
  float descent;

  // Beware those who step here: This code is designed to match Win32 font
  // metrics *exactly* (except the adjustment of ascent/descent on
  // Linux/Android).
  if (isVDMXValid) {
    ascent = vdmxAscent;
    descent = -vdmxDescent;
  } else {
    ascent = SkScalarRoundToInt(-metrics.fAscent);
    descent = SkScalarRoundToInt(metrics.fDescent);
#if OS(LINUX) || OS(ANDROID)
    // When subpixel positioning is enabled, if the descent is rounded down, the
    // descent part of the glyph may be truncated when displayed in a 'overflow:
    // hidden' container. To avoid that, borrow 1 unit from the ascent when
    // possible.
    // FIXME: This can be removed if sub-pixel ascent/descent is supported.
    if (platformData().fontRenderStyle().useSubpixelPositioning &&
        descent < SkScalarToFloat(metrics.fDescent) && ascent >= 1) {
      ++descent;
      --ascent;
    }
#endif
  }

  m_fontMetrics.setAscent(ascent);
  m_fontMetrics.setDescent(descent);

  float xHeight;
  if (metrics.fXHeight) {
    xHeight = metrics.fXHeight;
    m_fontMetrics.setXHeight(xHeight);
  } else {
    xHeight = ascent * 0.56;  // Best guess from Windows font metrics.
    m_fontMetrics.setXHeight(xHeight);
    m_fontMetrics.setHasXHeight(false);
  }

  float lineGap = SkScalarToFloat(metrics.fLeading);
  m_fontMetrics.setLineGap(lineGap);
  m_fontMetrics.setLineSpacing(lroundf(ascent) + lroundf(descent) +
                               lroundf(lineGap));

  SkScalar underlineThickness, underlinePosition;
  if (metrics.hasUnderlineThickness(&underlineThickness) &&
      metrics.hasUnderlinePosition(&underlinePosition)) {
    m_fontMetrics.setUnderlineThickness(SkScalarToFloat(underlineThickness));
    m_fontMetrics.setUnderlinePosition(SkScalarToFloat(-underlinePosition));
  }

  if (platformData().orientation() == Vertical &&
      !isTextOrientationFallback()) {
    static const uint32_t vheaTag = SkSetFourByteTag('v', 'h', 'e', 'a');
    static const uint32_t vorgTag = SkSetFourByteTag('V', 'O', 'R', 'G');
    size_t vheaSize = face->getTableSize(vheaTag);
    size_t vorgSize = face->getTableSize(vorgTag);
    if ((vheaSize > 0) || (vorgSize > 0))
      m_hasVerticalGlyphs = true;
  }

  // In WebKit/WebCore/platform/graphics/SimpleFontData.cpp, m_spaceWidth is
  // calculated for us, but we need to calculate m_maxCharWidth and
  // m_avgCharWidth in order for text entry widgets to be sized correctly.
  // FIXME: This seems incorrect and should probably use fMaxCharWidth as
  // the code path above.
  SkScalar xRange = metrics.fXMax - metrics.fXMin;
  m_maxCharWidth =
      SkScalarRoundToInt(xRange * SkScalarRoundToInt(m_platformData.size()));

  if (metrics.fAvgCharWidth)
    m_avgCharWidth = SkScalarRoundToInt(metrics.fAvgCharWidth);
  else {
    m_avgCharWidth = xHeight;

    GlyphPage* glyphPageZero = GlyphPageTreeNode::getRootChild(this, 0)->page();

    if (glyphPageZero) {
      static const UChar32 xChar = 'x';
      const Glyph xGlyph = glyphPageZero->glyphForCharacter(xChar);

      if (xGlyph) {
        // In widthForGlyph(), xGlyph will be compared with
        // m_zeroWidthSpaceGlyph, which isn't initialized yet here.
        // Initialize it with zero to make sure widthForGlyph() returns
        // the right width.
        m_zeroWidthSpaceGlyph = 0;
        m_avgCharWidth = widthForGlyph(xGlyph);
      }
    }
  }

  if (int unitsPerEm = face->getUnitsPerEm())
    m_fontMetrics.setUnitsPerEm(unitsPerEm);
}