gfx/thebes/gfxHarfBuzzShaper.h

   1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef GFX_HARFBUZZSHAPER_H
   7 #define GFX_HARFBUZZSHAPER_H
   8
   9 #include "gfxTypes.h"
  10 #include "gfxFont.h"
  11 #include "nsDataHashtable.h"
  12 #include "nsPoint.h"
  13
  14 #include "harfbuzz/hb.h"
  15
  16 class gfxHarfBuzzShaper : public gfxFontShaper {
  17 public:
  18     gfxHarfBuzzShaper(gfxFont *aFont);
  19     virtual ~gfxHarfBuzzShaper();
  20
  21     virtual bool ShapeText(gfxContext      *aContext,
  22                            const PRUnichar *aText,
  23                            uint32_t         aOffset,
  24                            uint32_t         aLength,
  25                            int32_t          aScript,
  26                            gfxShapedText   *aShapedText);
  27
  28     // get a given font table in harfbuzz blob form
  29     hb_blob_t * GetFontTable(hb_tag_t aTag) const;
  30
  31     // map unicode character to glyph ID
  32     hb_codepoint_t GetGlyph(hb_codepoint_t unicode,
  33                             hb_codepoint_t variation_selector) const;
  34
  35     // get harfbuzz glyph advance, in font design units
  36     hb_position_t GetGlyphHAdvance(gfxContext *aContext,
  37                                    hb_codepoint_t glyph) const;
  38
  39     hb_position_t GetHKerning(uint16_t aFirstGlyph,
  40                               uint16_t aSecondGlyph) const;
  41
  42 protected:
  43     nsresult SetGlyphsFromRun(gfxContext      *aContext,
  44                               gfxShapedText   *aShapedText,
  45                               uint32_t         aOffset,
  46                               uint32_t         aLength,
  47                               const PRUnichar *aText,
  48                               hb_buffer_t     *aBuffer);
  49
  50     // retrieve glyph positions, applying advance adjustments and attachments
  51     // returns results in appUnits
  52     nscoord GetGlyphPositions(gfxContext *aContext,
  53                               hb_buffer_t *aBuffer,
  54                               nsTArray<nsPoint>& aPositions,
  55                               uint32_t aAppUnitsPerDevUnit);
  56
  57     // harfbuzz face object, created on first use (caches font tables)
  58     hb_face_t         *mHBFace;
  59
  60     // Following table references etc are declared "mutable" because the
  61     // harfbuzz callback functions take a const ptr to the shaper, but
  62     // wish to cache tables here to avoid repeatedly looking them up
  63     // in the font.
  64
  65     // Old-style TrueType kern table, if we're not doing GPOS kerning
  66     mutable hb_blob_t *mKernTable;
  67
  68     // Cached copy of the hmtx table and numLongMetrics field from hhea,
  69     // for use when looking up glyph metrics; initialized to 0 by the
  70     // constructor so we can tell it hasn't been set yet.
  71     // This is a signed value so that we can use -1 to indicate
  72     // an error (if the hhea table was not available).
  73     mutable hb_blob_t *mHmtxTable;
  74     mutable int32_t    mNumLongMetrics;
  75
  76     // Cached pointer to cmap subtable to be used for char-to-glyph mapping.
  77     // This comes from GetFontTablePtr; if it is non-null, our destructor
  78     // must call ReleaseFontTablePtr to avoid permanently caching the table.
  79     mutable hb_blob_t *mCmapTable;
  80     mutable int32_t    mCmapFormat;
  81     mutable uint32_t   mSubtableOffset;
  82     mutable uint32_t   mUVSTableOffset;
  83
  84     // Whether the font implements GetGlyph, or we should read tables
  85     // directly
  86     bool mUseFontGetGlyph;
  87     // Whether the font implements GetGlyphWidth, or we should read tables
  88     // directly to get ideal widths
  89     bool mUseFontGlyphWidths;
  90 };
  91
  92 #endif /* GFX_HARFBUZZSHAPER_H */