ttgload.c

下载来的一个看图软件的源代码

#ifdef FT_CONFIG_OPTION_INCREMENTAL
    if ( glyph_data_loaded )
      face->root.internal->incremental_interface->funcs->free_glyph_data(
        face->root.internal->incremental_interface->object,
        &glyph_data );
#endif

    return error;
  }


  static FT_Error
  compute_glyph_metrics( TT_Loader   loader,
                         FT_UInt     glyph_index )
  {
    FT_BBox       bbox;
    TT_Face       face = (TT_Face)loader->face;
    FT_Fixed      y_scale;
    TT_GlyphSlot  glyph = loader->glyph;
    TT_Size       size = (TT_Size)loader->size;


    y_scale = 0x10000L;
    if ( ( loader->load_flags & FT_LOAD_NO_SCALE ) == 0 )
      y_scale = size->root.metrics.y_scale;

    if ( glyph->format != FT_GLYPH_FORMAT_COMPOSITE )
    {
      glyph->outline.flags &= ~FT_OUTLINE_SINGLE_PASS;

      /* copy outline to our glyph slot */
      FT_GlyphLoader_CopyPoints( glyph->internal->loader, loader->gloader );
      glyph->outline = glyph->internal->loader->base.outline;

      /* translate array so that (0,0) is the glyph's origin */
      FT_Outline_Translate( &glyph->outline, -loader->pp1.x, 0 );

      FT_Outline_Get_CBox( &glyph->outline, &bbox );

      if ( IS_HINTED( loader->load_flags ) )
      {
        /* grid-fit the bounding box */
        bbox.xMin &= -64;
        bbox.yMin &= -64;
        bbox.xMax  = ( bbox.xMax + 63 ) & -64;
        bbox.yMax  = ( bbox.yMax + 63 ) & -64;
      }
    }
    else
      bbox = loader->bbox;

    /* get the device-independent horizontal advance.  It is scaled later */
    /* by the base layer.                                                 */
    {
      FT_Pos  advance = loader->linear;


      /* the flag FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH was introduced to */
      /* correctly support DynaLab fonts, which have an incorrect       */
      /* `advance_Width_Max' field!  It is used, to my knowledge,       */
      /* exclusively in the X-TrueType font server.                     */
      /*                                                                */
      if ( face->postscript.isFixedPitch                                     &&
           ( loader->load_flags & FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH ) == 0 )
        advance = face->horizontal.advance_Width_Max;

      /* we need to return the advance in font units in linearHoriAdvance, */
      /* it will be scaled later by the base layer.                        */
      glyph->linearHoriAdvance = advance;
    }

    glyph->metrics.horiBearingX = bbox.xMin;
    glyph->metrics.horiBearingY = bbox.yMax;
    glyph->metrics.horiAdvance  = loader->pp2.x - loader->pp1.x;

    /* don't forget to hint the advance when we need to */
    if ( IS_HINTED( loader->load_flags ) )
      glyph->metrics.horiAdvance = ( glyph->metrics.horiAdvance + 32 ) & -64;

    /* Now take care of vertical metrics.  In the case where there is    */
    /* no vertical information within the font (relatively common), make */
    /* up some metrics by `hand'...                                      */

    {
      FT_Short   top_bearing;    /* vertical top side bearing (EM units) */
      FT_UShort  advance_height; /* vertical advance height   (EM units) */

      FT_Pos     left;     /* scaled vertical left side bearing */
      FT_Pos     top;      /* scaled vertical top side bearing  */
      FT_Pos     advance;  /* scaled vertical advance height    */

      /* Get the unscaled top bearing and advance height. */
      if ( face->vertical_info &&
           face->vertical.number_Of_VMetrics > 0 )
      {
        /* Don't assume that both the vertical header and vertical */
        /* metrics are present in the same font :-)                */

        TT_Get_Metrics( (TT_HoriHeader*)&face->vertical,
                        glyph_index,
                        &top_bearing,
                        &advance_height );
      }
      else
      {
        /* Make up the distances from the horizontal header.   */

        /* NOTE: The OS/2 values are the only `portable' ones, */
        /*       which is why we use them, if there is an OS/2 */
        /*       table in the font.  Otherwise, we use the     */
        /*       values defined in the horizontal header.      */
        /*                                                     */
        /* NOTE2: The sTypoDescender is negative, which is why */
        /*        we compute the baseline-to-baseline distance */
        /*        here with:                                   */
        /*             ascender - descender + linegap          */
        /*                                                     */
        if ( face->os2.version != 0xFFFFU )
        {
          top_bearing    = (FT_Short)( face->os2.sTypoLineGap / 2 );
          advance_height = (FT_UShort)( face->os2.sTypoAscender -
                                        face->os2.sTypoDescender +
                                        face->os2.sTypoLineGap );
        }
        else
        {
          top_bearing    = (FT_Short)( face->horizontal.Line_Gap / 2 );
          advance_height = (FT_UShort)( face->horizontal.Ascender  +
                                        face->horizontal.Descender +
                                        face->horizontal.Line_Gap );
        }
      }

#ifdef FT_CONFIG_OPTION_INCREMENTAL

      /* If this is an incrementally loaded font see if there are */
      /* overriding metrics for this glyph.                       */
      if ( face->root.internal->incremental_interface &&
           face->root.internal->incremental_interface->funcs->get_glyph_metrics )
      {
        FT_Incremental_MetricsRec  metrics;
        FT_Error                   error = 0;


        metrics.bearing_x = 0;
        metrics.bearing_y = top_bearing;
        metrics.advance = advance_height;
        error =
          face->root.internal->incremental_interface->funcs->get_glyph_metrics(
            face->root.internal->incremental_interface->object,
            glyph_index, TRUE, &metrics );

        if ( error )
          return error;

        top_bearing    = (FT_Short)metrics.bearing_y;
        advance_height = (FT_UShort)metrics.advance;
      }

#endif /* FT_CONFIG_OPTION_INCREMENTAL */

      /* We must adjust the top_bearing value from the bounding box given */
      /* in the glyph header to the bounding box calculated with          */
      /* FT_Get_Outline_CBox().                                           */

      /* scale the metrics */
      if ( !( loader->load_flags & FT_LOAD_NO_SCALE ) )
      {
        top     = FT_MulFix( top_bearing + loader->bbox.yMax, y_scale )
                    - bbox.yMax;
        advance = FT_MulFix( advance_height, y_scale );
      }
      else
      {
        top     = top_bearing + loader->bbox.yMax - bbox.yMax;
        advance = advance_height;
      }

      /* set the advance height in design units.  It is scaled later by */
      /* the base layer.                                                */
      glyph->linearVertAdvance = advance_height;

      /* XXX: for now, we have no better algorithm for the lsb, but it */
      /*      should work fine.                                        */
      /*                                                               */
      left = ( bbox.xMin - bbox.xMax ) / 2;

      /* grid-fit them if necessary */
      if ( IS_HINTED( loader->load_flags ) )
      {
        left   &= -64;
        top     = ( top + 63     ) & -64;
        advance = ( advance + 32 ) & -64;
      }

      glyph->metrics.vertBearingX = left;
      glyph->metrics.vertBearingY = top;
      glyph->metrics.vertAdvance  = advance;
    }

    /* adjust advance width to the value contained in the hdmx table */
    if ( !face->postscript.isFixedPitch && size &&
         IS_HINTED( loader->load_flags )        )
    {
      FT_Byte*  widths = Get_Advance_Widths( face,
                                             size->root.metrics.x_ppem );


      if ( widths )
        glyph->metrics.horiAdvance = widths[glyph_index] << 6;
    }

    /* set glyph dimensions */
    glyph->metrics.width  = bbox.xMax - bbox.xMin;
    glyph->metrics.height = bbox.yMax - bbox.yMin;

    return 0;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    TT_Load_Glyph                                                      */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A function used to load a single glyph within a given glyph slot,  */
  /*    for a given size.                                                  */
  /*                                                                       */
  /* <Input>                                                               */
  /*    glyph       :: A handle to a target slot object where the glyph    */
  /*                   will be loaded.                                     */
  /*                                                                       */
  /*    size        :: A handle to the source face size at which the glyph */
  /*                   must be scaled/loaded.                              */
  /*                                                                       */
  /*    glyph_index :: The index of the glyph in the font file.            */
  /*                                                                       */
  /*    load_flags  :: A flag indicating what to load for this glyph.  The */
  /*                   FT_LOAD_XXX constants can be used to control the    */
  /*                   glyph loading process (e.g., whether the outline    */
  /*                   should be scaled, whether to load bitmaps or not,   */
  /*                   whether to hint the outline, etc).                  */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  FT_LOCAL_DEF( FT_Error )
  TT_Load_Glyph( TT_Size       size,
                 TT_GlyphSlot  glyph,
                 FT_UShort     glyph_index,
                 FT_Int32      load_flags )
  {
    SFNT_Service  sfnt;
    TT_Face       face;
    FT_Stream     stream;
    FT_Error      error;
    TT_LoaderRec  loader;


    face   = (TT_Face)glyph->face;
    sfnt   = (SFNT_Service)face->sfnt;
    stream = face->root.stream;
    error  = 0;

    if ( !size || ( load_flags & FT_LOAD_NO_SCALE )   ||
                  ( load_flags & FT_LOAD_NO_RECURSE ) )
    {
      size        = NULL;
      load_flags |= FT_LOAD_NO_SCALE   |
                    FT_LOAD_NO_HINTING |
                    FT_LOAD_NO_BITMAP;
    }

    glyph->num_subglyphs = 0;

#ifdef TT_CONFIG_OPTION_EMBEDDED_BITMAPS

    /* try to load embedded bitmap if any              */
    /*                                                 */
    /* XXX: The convention should be emphasized in     */
    /*      the documents because it can be confusing. */
    if ( size                                    &&
         size->strike_index != 0xFFFFU           &&
         sfnt->load_sbits                        &&
         ( load_flags & FT_LOAD_NO_BITMAP ) == 0 )

    {
      TT_SBit_MetricsRec  metrics;


      error = sfnt->load_sbit_image( face,
                                     (FT_ULong)size->strike_index,
                                     (FT_UInt)glyph_index,
                                     (FT_Int)load_flags,
                                     stream,
                                     &glyph->bitmap,
                                     &metrics );
      if ( !error )
      {
        glyph->outline.n_points   = 0;
        glyph->outline.n_contours = 0;

        glyph->metrics.width  = (FT_Pos)metrics.width  << 6;
        glyph->metrics.height = (FT_Pos)metrics.height << 6;

        glyph->metrics.horiBearingX = (FT_Pos)metrics.horiBearingX << 6;
        glyph->metrics.horiBearingY = (FT_Pos)metrics.horiBearingY << 6;
        glyph->metrics.horiAdvance  = (FT_Pos)metrics.horiAdvance  << 6;

        glyph->metrics.vertBearingX = (FT_Pos)metrics.vertBearingX << 6;
        glyph->metrics.vertBearingY = (FT_Pos)metrics.vertBearingY << 6;
        glyph->metrics.vertAdvance  = (FT_Pos)metrics.vertAdvance  << 6;

        glyph->format = FT_GLYPH_FORMAT_BITMAP;
        if ( load_flags & FT_LOAD_VERTICAL_LAYOUT )
        {
          glyph->bitmap_left = metrics.vertBearingX;
          glyph->bitmap_top  = metrics.vertBearingY;
        }
        else
        {
          glyph->bitmap_left = metrics.horiBearingX;
          glyph->bitmap_top  = metrics.horiBearingY;
        }
        return error;
      }
    }

#endif /* TT_CONFIG_OPTION_EMBEDDED_BITMAPS */

    /* return immediately if we only want the embedded bitmaps */
    if ( load_flags & FT_LOAD_SBITS_ONLY )
      return TT_Err_Invalid_Argument;

    /* seek to the beginning of the glyph table.  For Type 42 fonts      */
    /* the table might be accessed from a Postscript stream or something */
    /* else...                                                           */

#ifdef FT_CONFIG_OPTION_INCREMENTAL

    /* Don't look for the glyph table if this is an incremental font. */
    if ( !face->root.internal->incremental_interface )

#endif

    {
      error = face->goto_table( face, TTAG_glyf, stream, 0 );
      if ( error )
      {
        FT_ERROR(( "TT_Load_Glyph: could not access glyph table\n" ));
        goto Exit;
      }
    }

    FT_MEM_ZERO( &loader, sizeof ( loader ) );

    /* update the glyph zone bounds */
    {
      FT_GlyphLoader  gloader = FT_FACE_DRIVER(face)->glyph_loader;


      loader.gloader = gloader;

      FT_GlyphLoader_Rewind( gloader );

      tt_prepare_zone( &loader.zone, &gloader->base, 0, 0 );
      tt_prepare_zone( &loader.base, &gloader->base, 0, 0 );
    }

#ifdef TT_CONFIG_OPTION_BYTECODE_INTERPRETER

    if ( size )
    {
      /* query new execution context */
      loader.exec = size->debug ? size->context : TT_New_Context( face );
      if ( !loader.exec )
        return TT_Err_Could_Not_Find_Context;

      TT_Load_Context( loader.exec, face, size );
      loader.instructions = loader.exec->glyphIns;

      /* load default graphics state - if needed */
      if ( size->GS.instruct_control & 2 )
        loader.exec->GS = tt_default_graphics_state;
    }

#endif /* TT_CONFIG_OPTION_BYTECODE_INTERPRETER */

    /* clear all outline flags, except the `owner' one */
    glyph->outline.flags = 0;

    /* let's initialize the rest of our loader now */

    loader.load_flags    = load_flags;

    loader.face   = (FT_Face)face;
    loader.size   = (FT_Size)size;
    loader.glyph  = (FT_GlyphSlot)glyph;
    loader.stream = stream;

#ifdef FT_CONFIG_OPTION_INCREMENTAL

    if ( face->root.internal->incremental_interface )
      loader.glyf_offset = 0;
    else

#endif

      loader.glyf_offset = FT_STREAM_POS();

#ifdef TT_CONFIG_OPTION_BYTECODE_INTERPRETER

    /* if the cvt program has disabled hinting, the argument */
    /* is ignored.                                           */
    if ( size && ( size->GS.instruct_control & 1 ) )
      loader.load_flags |= FT_LOAD_NO_HINTING;

#endif /* TT_CONFIG_OPTION_BYTECODE_INTERPRETER */

    /* Main loading loop */
    glyph->format        = FT_GLYPH_FORMAT_OUTLINE;
    glyph->num_subglyphs = 0;

    error = load_truetype_glyph( &loader, glyph_index, 0 );
    if ( !error )
      compute_glyph_metrics( &loader, glyph_index );

#ifdef TT_CONFIG_OPTION_BYTECODE_INTERPRETER

    if ( !size || !size->debug )
      TT_Done_Context( loader.exec );

#endif /* TT_CONFIG_OPTION_BYTECODE_INTERPRETER */

    /* Set the `high precision' bit flag.                           */
    /* This is _critical_ to get correct output for monochrome      */
    /* TrueType glyphs at all sizes using the bytecode interpreter. */
    /*                                                              */
    if ( size && size->root.metrics.y_ppem < 24 )
      glyph->outline.flags |= FT_OUTLINE_HIGH_PRECISION;

  Exit:
    return error;
  }


/* END */