gfx/thebes/gfxFT2Utils.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_FT2UTILS_H
   7 #define GFX_FT2UTILS_H
   8
   9 #include "cairo-ft.h"
  10 #include "gfxFT2FontBase.h"
  11 #include "mozilla/Likely.h"
  12
  13 // Rounding and truncation functions for a FreeType fixed point number
  14 // (FT26Dot6) stored in a 32bit integer with high 26 bits for the integer
  15 // part and low 6 bits for the fractional part.
  16 #define FLOAT_FROM_26_6(x) ((x) / 64.0)
  17 #define FLOAT_FROM_16_16(x) ((x) / 65536.0)
  18 #define ROUND_26_6_TO_INT(x) ((x) >= 0 ?  ((32 + (x)) >> 6) \
  19                                        : -((32 - (x)) >> 6))
  20
  21 typedef struct FT_FaceRec_* FT_Face;
  22
  23 class gfxFT2LockedFace {
  24 public:
  25     gfxFT2LockedFace(gfxFT2FontBase *aFont) :
  26         mGfxFont(aFont),
  27         mFace(cairo_ft_scaled_font_lock_face(aFont->CairoScaledFont()))
  28     { }
  29     ~gfxFT2LockedFace()
  30     {
  31         if (mFace) {
  32             cairo_ft_scaled_font_unlock_face(mGfxFont->CairoScaledFont());
  33         }
  34     }
  35
  36     FT_Face get() { return mFace; };
  37
  38     /**
  39      * Get the glyph id for a Unicode character representable by a single
  40      * glyph, or return zero if there is no such glyph.  This does no caching,
  41      * so you probably want gfxFcFont::GetGlyph.
  42      */
  43     uint32_t GetGlyph(uint32_t aCharCode);
  44     /**
  45      * Returns 0 if there is no variation selector cmap subtable.
  46      */
  47     uint32_t GetUVSGlyph(uint32_t aCharCode, uint32_t aVariantSelector);
  48
  49     void GetMetrics(gfxFont::Metrics* aMetrics, uint32_t* aSpaceGlyph);
  50
  51     // A scale factor for use in converting horizontal metrics from font units
  52     // to pixels.
  53     gfxFloat XScale()
  54     {
  55         if (MOZ_UNLIKELY(!mFace))
  56             return 0.0;
  57
  58         const FT_Size_Metrics& ftMetrics = mFace->size->metrics;
  59
  60         if (FT_IS_SCALABLE(mFace)) {
  61             // Prefer FT_Size_Metrics::x_scale to x_ppem as x_ppem does not
  62             // have subpixel accuracy.
  63             //
  64             // FT_Size_Metrics::x_scale is in 16.16 fixed point format.  Its
  65             // (fractional) value is a factor that converts vertical metrics
  66             // from design units to units of 1/64 pixels, so that the result
  67             // may be interpreted as pixels in 26.6 fixed point format.
  68             return FLOAT_FROM_26_6(FLOAT_FROM_16_16(ftMetrics.x_scale));
  69         }
  70
  71         // Not scalable.
  72         // FT_Size_Metrics doc says x_scale is "only relevant for scalable
  73         // font formats".
  74         return gfxFloat(ftMetrics.x_ppem) / gfxFloat(mFace->units_per_EM);
  75     }
  76
  77 protected:
  78     /**
  79      * Get extents for a simple character representable by a single glyph.
  80      * The return value is the glyph id of that glyph or zero if no such glyph
  81      * exists.  aExtents is only set when this returns a non-zero glyph id.
  82      */
  83     uint32_t GetCharExtents(char aChar, cairo_text_extents_t* aExtents);
  84
  85     typedef FT_UInt (*CharVariantFunction)(FT_Face  face,
  86                                            FT_ULong charcode,
  87                                            FT_ULong variantSelector);
  88     CharVariantFunction FindCharVariantFunction();
  89
  90     nsRefPtr<gfxFT2FontBase> mGfxFont;
  91     FT_Face mFace;
  92 };
  93
  94 #endif /* GFX_FT2UTILS_H */