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 "gfxFont.h"
  10
  11 #include "harfbuzz/hb.h"
  12 #include "nsUnicodeProperties.h"
  13
  14 class gfxHarfBuzzShaper : public gfxFontShaper {
  15 public:
  16     explicit gfxHarfBuzzShaper(gfxFont *aFont);
  17     virtual ~gfxHarfBuzzShaper();
  18
  19     /*
  20      * For HarfBuzz font callback functions, font_data is a ptr to a
  21      * FontCallbackData struct
  22      */
  23     struct FontCallbackData {
  24         gfxHarfBuzzShaper *mShaper;
  25         gfxContext        *mContext;
  26     };
  27
  28     bool Initialize();
  29     virtual bool ShapeText(gfxContext      *aContext,
  30                            const char16_t *aText,
  31                            uint32_t         aOffset,
  32                            uint32_t         aLength,
  33                            int32_t          aScript,
  34                            gfxShapedText   *aShapedText);
  35
  36     // get a given font table in harfbuzz blob form
  37     hb_blob_t * GetFontTable(hb_tag_t aTag) const;
  38
  39     // map unicode character to glyph ID
  40     hb_codepoint_t GetGlyph(hb_codepoint_t unicode,
  41                             hb_codepoint_t variation_selector) const;
  42
  43     // get harfbuzz glyph advance, in font design units
  44     hb_position_t GetGlyphHAdvance(gfxContext *aContext,
  45                                    hb_codepoint_t glyph) const;
  46
  47     // get harfbuzz horizontal advance in 16.16 fixed point format.
  48     static hb_position_t
  49     HBGetGlyphHAdvance(hb_font_t *font, void *font_data,
  50                        hb_codepoint_t glyph, void *user_data);
  51
  52     hb_position_t GetHKerning(uint16_t aFirstGlyph,
  53                               uint16_t aSecondGlyph) const;
  54
  55     static hb_script_t
  56     GetHBScriptUsedForShaping(int32_t aScript) {
  57         // Decide what harfbuzz script code will be used for shaping
  58         hb_script_t hbScript;
  59         if (aScript <= MOZ_SCRIPT_INHERITED) {
  60             // For unresolved "common" or "inherited" runs,
  61             // default to Latin for now.
  62             hbScript = HB_SCRIPT_LATIN;
  63         } else {
  64             hbScript =
  65                 hb_script_t(mozilla::unicode::GetScriptTagForCode(aScript));
  66         }
  67         return hbScript;
  68     }
  69
  70 protected:
  71     nsresult SetGlyphsFromRun(gfxContext      *aContext,
  72                               gfxShapedText   *aShapedText,
  73                               uint32_t         aOffset,
  74                               uint32_t         aLength,
  75                               const char16_t *aText,
  76                               hb_buffer_t     *aBuffer);
  77
  78     // retrieve glyph positions, applying advance adjustments and attachments
  79     // returns results in appUnits
  80     nscoord GetGlyphPositions(gfxContext *aContext,
  81                               hb_buffer_t *aBuffer,
  82                               nsTArray<nsPoint>& aPositions,
  83                               uint32_t aAppUnitsPerDevUnit);
  84
  85     // harfbuzz face object: we acquire a reference from the font entry
  86     // on shaper creation, and release it in our destructor
  87     hb_face_t         *mHBFace;
  88
  89     // size-specific font object, owned by the gfxHarfBuzzShaper
  90     hb_font_t         *mHBFont;
  91
  92     FontCallbackData   mCallbackData;
  93
  94     // Following table references etc are declared "mutable" because the
  95     // harfbuzz callback functions take a const ptr to the shaper, but
  96     // wish to cache tables here to avoid repeatedly looking them up
  97     // in the font.
  98
  99     // Old-style TrueType kern table, if we're not doing GPOS kerning
 100     mutable hb_blob_t *mKernTable;
 101
 102     // Cached copy of the hmtx table and numLongMetrics field from hhea,
 103     // for use when looking up glyph metrics; initialized to 0 by the
 104     // constructor so we can tell it hasn't been set yet.
 105     // This is a signed value so that we can use -1 to indicate
 106     // an error (if the hhea table was not available).
 107     mutable hb_blob_t *mHmtxTable;
 108     mutable int32_t    mNumLongMetrics;
 109
 110     // Cached pointer to cmap subtable to be used for char-to-glyph mapping.
 111     // This comes from GetFontTablePtr; if it is non-null, our destructor
 112     // must call ReleaseFontTablePtr to avoid permanently caching the table.
 113     mutable hb_blob_t *mCmapTable;
 114     mutable int32_t    mCmapFormat;
 115     mutable uint32_t   mSubtableOffset;
 116     mutable uint32_t   mUVSTableOffset;
 117
 118     // Whether the font implements GetGlyph, or we should read tables
 119     // directly
 120     bool mUseFontGetGlyph;
 121     // Whether the font implements GetGlyphWidth, or we should read tables
 122     // directly to get ideal widths
 123     bool mUseFontGlyphWidths;
 124
 125     bool mInitialized;
 126 };
 127
 128 #endif /* GFX_HARFBUZZSHAPER_H */