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gfxMathTable.h (4948B)

      1 /* This Source Code Form is subject to the terms of the Mozilla Public
      2 * License, v. 2.0. If a copy of the MPL was not distributed with this
      3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      4 
      5 #ifndef GFX_MATH_TABLE_H
      6 #define GFX_MATH_TABLE_H
      7 
      8 #include "gfxFont.h"
      9 
     10 /**
     11 * Used by |gfxFont| to represent the MATH table of an OpenType font.
     12 * Each |gfxFont| owns at most one |gfxMathTable| instance.
     13 */
     14 class gfxMathTable {
     15 public:
     16  /**
     17   * @param aFace The HarfBuzz face containing the math table.
     18   * @param aSize The font size to pass to HarfBuzz.
     19   */
     20  gfxMathTable(hb_face_t* aFace, gfxFloat aSize);
     21 
     22  /**
     23   * Releases our reference to the MATH table and cleans up everything else.
     24   */
     25  ~gfxMathTable();
     26 
     27  enum MathConstant {
     28    // The order of the constants must match the order of the fields
     29    // defined in the MATH table.
     30    ScriptPercentScaleDown,
     31    ScriptScriptPercentScaleDown,
     32    DelimitedSubFormulaMinHeight,
     33    DisplayOperatorMinHeight,
     34    MathLeading,
     35    AxisHeight,
     36    AccentBaseHeight,
     37    FlattenedAccentBaseHeight,
     38    SubscriptShiftDown,
     39    SubscriptTopMax,
     40    SubscriptBaselineDropMin,
     41    SuperscriptShiftUp,
     42    SuperscriptShiftUpCramped,
     43    SuperscriptBottomMin,
     44    SuperscriptBaselineDropMax,
     45    SubSuperscriptGapMin,
     46    SuperscriptBottomMaxWithSubscript,
     47    SpaceAfterScript,
     48    UpperLimitGapMin,
     49    UpperLimitBaselineRiseMin,
     50    LowerLimitGapMin,
     51    LowerLimitBaselineDropMin,
     52    StackTopShiftUp,
     53    StackTopDisplayStyleShiftUp,
     54    StackBottomShiftDown,
     55    StackBottomDisplayStyleShiftDown,
     56    StackGapMin,
     57    StackDisplayStyleGapMin,
     58    StretchStackTopShiftUp,
     59    StretchStackBottomShiftDown,
     60    StretchStackGapAboveMin,
     61    StretchStackGapBelowMin,
     62    FractionNumeratorShiftUp,
     63    FractionNumeratorDisplayStyleShiftUp,
     64    FractionDenominatorShiftDown,
     65    FractionDenominatorDisplayStyleShiftDown,
     66    FractionNumeratorGapMin,
     67    FractionNumDisplayStyleGapMin,
     68    FractionRuleThickness,
     69    FractionDenominatorGapMin,
     70    FractionDenomDisplayStyleGapMin,
     71    SkewedFractionHorizontalGap,
     72    SkewedFractionVerticalGap,
     73    OverbarVerticalGap,
     74    OverbarRuleThickness,
     75    OverbarExtraAscender,
     76    UnderbarVerticalGap,
     77    UnderbarRuleThickness,
     78    UnderbarExtraDescender,
     79    RadicalVerticalGap,
     80    RadicalDisplayStyleVerticalGap,
     81    RadicalRuleThickness,
     82    RadicalExtraAscender,
     83    RadicalKernBeforeDegree,
     84    RadicalKernAfterDegree,
     85    RadicalDegreeBottomRaisePercent
     86  };
     87 
     88  /**
     89   * Returns the value of the specified constant from the MATH table.
     90   */
     91  gfxFloat Constant(MathConstant aConstant) const;
     92 
     93  /**
     94   * Returns the value of the specified constant in app units.
     95   */
     96  nscoord Constant(MathConstant aConstant,
     97                   uint32_t aAppUnitsPerDevPixel) const {
     98    return NSToCoordRound(Constant(aConstant) * aAppUnitsPerDevPixel);
     99  }
    100 
    101  /**
    102   *  If the MATH table contains an italic correction for that glyph, this
    103   *  function returns the corresponding value. Otherwise it returns 0.
    104   */
    105  gfxFloat ItalicsCorrection(uint32_t aGlyphID) const;
    106 
    107  /**
    108   * @param aGlyphID  glyph index of the character we want to stretch
    109   * @param aVertical direction of the stretching (vertical/horizontal)
    110   * @param aRTL      writing direction (LTR/RTL)
    111   * @param aSize     the desired size variant
    112   *
    113   * Returns the glyph index of the desired size variant or 0 if there is not
    114   * any such size variant.
    115   */
    116  uint32_t VariantsSize(uint32_t aGlyphID, bool aVertical, bool aRTL,
    117                        uint16_t aSize) const;
    118 
    119  /**
    120   * @param aGlyphID  glyph index of the character we want to stretch
    121   * @param aVertical direction of the stretching (vertical/horizontal)
    122   * @param aRTL      writing direction (LTR/RTL)
    123   * @param aGlyphs   pre-allocated buffer of 4 elements where the glyph
    124   * indexes (or 0 for absent parts) will be stored. The parts are stored in
    125   * the order expected by the nsMathMLChar: Top (or Left), Middle, Bottom
    126   * (or Right), Glue.
    127   *
    128   * Tries to fill-in aGlyphs with the relevant glyph indexes and returns
    129   * whether the operation was successful. The function returns false if
    130   * there is not any assembly for the character we want to stretch or if
    131   * the format is not supported by the nsMathMLChar code.
    132   *
    133   */
    134  bool VariantsParts(uint32_t aGlyphID, bool aVertical, bool aRTL,
    135                     uint32_t aGlyphs[4]) const;
    136 
    137 private:
    138  // size-specific font object, owned by the gfxMathTable
    139  hb_font_t* mHBFont;
    140 
    141  static const unsigned int kMaxCachedSizeCount = 10;
    142  struct MathVariantCacheEntry {
    143    uint32_t glyphID;
    144    bool vertical;
    145    bool isRTL;
    146    uint32_t sizes[kMaxCachedSizeCount];
    147    uint32_t parts[4];
    148    bool arePartsValid;
    149  };
    150  mutable MathVariantCacheEntry mMathVariantCache;
    151  void ClearCache() const;
    152  void UpdateMathVariantCache(uint32_t aGlyphID, bool aVertical,
    153                              bool aRTL) const;
    154 };
    155 
    156 #endif