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       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          90 :     explicit gfxFT2LockedFace(gfxFT2FontBase *aFont) :
      26             :         mGfxFont(aFont),
      27          90 :         mFace(cairo_ft_scaled_font_lock_face(aFont->CairoScaledFont()))
      28          90 :     { }
      29          90 :     ~gfxFT2LockedFace()
      30          90 :     {
      31          90 :         if (mFace) {
      32          90 :             cairo_ft_scaled_font_unlock_face(mGfxFont->CairoScaledFont());
      33             :         }
      34          90 :     }
      35             : 
      36           6 :     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           8 :     gfxFloat XScale()
      54             :     {
      55           8 :         if (MOZ_UNLIKELY(!mFace))
      56           0 :             return 0.0;
      57             : 
      58           8 :         const FT_Size_Metrics& ftMetrics = mFace->size->metrics;
      59             : 
      60           8 :         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           8 :             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           0 :         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             :     RefPtr<gfxFT2FontBase> mGfxFont;
      91             :     FT_Face mFace;
      92             : };
      93             : 
      94             : #endif /* GFX_FT2UTILS_H */