gfx/thebes/gfxMathTable.h

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