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123 lines
4.7 KiB
C++
123 lines
4.7 KiB
C++
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef GFX_MATH_TABLE_H
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#define GFX_MATH_TABLE_H
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#include "gfxFont.h"
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struct Coverage;
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struct GlyphAssembly;
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struct MATHTableHeader;
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struct MathConstants;
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struct MathGlyphConstruction;
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struct MathGlyphInfo;
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struct MathVariants;
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/**
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* Used by |gfxFontEntry| to represent the MATH table of an OpenType font.
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* Each |gfxFontEntry| owns at most one |gfxMathTable| instance.
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*/
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class gfxMathTable
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{
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public:
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/**
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* @param aMathTable The MATH table from the OpenType font
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*
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* The gfxMathTable object takes over ownership of the blob references
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* that are passed in, and will hb_blob_destroy() them when finished;
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* the caller should -not- destroy this reference.
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*/
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explicit gfxMathTable(hb_blob_t* aMathTable);
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/**
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* Releases our reference to the MATH table and cleans up everything else.
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*/
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~gfxMathTable();
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/**
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* Returns the value of the specified constant from the MATH table.
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*/
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int32_t GetMathConstant(gfxFontEntry::MathConstant aConstant);
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/**
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* If the MATH table contains an italic correction for that glyph, this
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* function gets the value and returns true. Otherwise it returns false.
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*/
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bool
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GetMathItalicsCorrection(uint32_t aGlyphID, int16_t* aItalicCorrection);
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/**
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* @param aGlyphID glyph index of the character we want to stretch
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* @param aVertical direction of the stretching (vertical/horizontal)
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* @param aSize the desired size variant
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*
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* Returns the glyph index of the desired size variant or 0 if there is not
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* any such size variant.
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*/
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uint32_t GetMathVariantsSize(uint32_t aGlyphID, bool aVertical,
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uint16_t aSize);
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/**
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* @param aGlyphID glyph index of the character we want to stretch
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* @param aVertical direction of the stretching (vertical/horizontal)
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* @param aGlyphs pre-allocated buffer of 4 elements where the glyph
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* indexes (or 0 for absent parts) will be stored. The parts are stored in
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* the order expected by the nsMathMLChar: Top (or Left), Middle, Bottom
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* (or Right), Glue.
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*
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* Tries to fill-in aGlyphs with the relevant glyph indexes and returns
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* whether the operation was successful. The function returns false if
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* there is not any assembly for the character we want to stretch or if
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* the format is not supported by the nsMathMLChar code.
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*
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*/
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bool GetMathVariantsParts(uint32_t aGlyphID, bool aVertical,
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uint32_t aGlyphs[4]);
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protected:
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friend class gfxFontEntry;
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// This allows gfxFontEntry to verify the validity of the main headers
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// before starting to use the MATH table.
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bool HasValidHeaders();
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private:
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// HarfBuzz blob where the MATH table is stored.
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hb_blob_t* mMathTable;
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// Cached values for the latest (mGlyphID, mVertical) pair that has been
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// accessed and the corresponding glyph construction. These are verified
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// by SelectGlyphConstruction and updated if necessary.
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// mGlyphConstruction will be set to nullptr if no construction is defined
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// for the glyph. If non-null, its mGlyphAssembly and mVariantCount fields
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// may be safely read, but no further validation will have been done.
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const MathGlyphConstruction* mGlyphConstruction;
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uint32_t mGlyphID;
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bool mVertical;
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void SelectGlyphConstruction(uint32_t aGlyphID, bool aVertical);
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// Access to some structures of the MATH table.
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// These accessors just return a pointer, but do NOT themselves check the
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// validity of anything. Until we've checked that HasValidHeaders (which
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// does validate them) returns true, they might return pointers that cannot
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// even safely be dereferenced. GetGlyphAssembly may return nullptr if the
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// given glyph has no assembly defined.
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const MATHTableHeader* GetMATHTableHeader();
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const MathConstants* GetMathConstants();
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const MathGlyphInfo* GetMathGlyphInfo();
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const MathVariants* GetMathVariants();
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const GlyphAssembly* GetGlyphAssembly(uint32_t aGlyphID, bool aVertical);
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// Verify whether a structure or an offset belongs to the math data and can
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// be read safely.
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bool ValidStructure(const char* aStructStart, uint16_t aStructSize);
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bool ValidOffset(const char* aOffsetStart, uint16_t aOffset);
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// Get the coverage index of a glyph index from an Open Type coverage table
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// or -1 if the glyph index is not found.
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int32_t GetCoverageIndex(const Coverage* aCoverage, uint32_t aGlyph);
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};
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#endif
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