ttdriver.c

下载来的一个看图软件的源代码

/***************************************************************************/
/*                                                                         */
/*  ttdriver.c                                                             */
/*                                                                         */
/*    TrueType font driver implementation (body).                          */
/*                                                                         */
/*  Copyright 1996-2001, 2002, 2003 by                                     */
/*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
/*                                                                         */
/*  This file is part of the FreeType project, and may only be used,       */
/*  modified, and distributed under the terms of the FreeType project      */
/*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
/*  this file you indicate that you have read the license and              */
/*  understand and accept it fully.                                        */
/*                                                                         */
/***************************************************************************/


#include <ft2build.h>
#include FT_INTERNAL_DEBUG_H
#include FT_INTERNAL_STREAM_H
#include FT_INTERNAL_SFNT_H
#include FT_TRUETYPE_IDS_H

#include "ttdriver.h"
#include "ttgload.h"

#include "tterrors.h"


  /*************************************************************************/
  /*                                                                       */
  /* The macro FT_COMPONENT is used in trace mode.  It is an implicit      */
  /* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log  */
  /* messages during execution.                                            */
  /*                                                                       */
#undef  FT_COMPONENT
#define FT_COMPONENT  trace_ttdriver


  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/
  /****                                                                 ****/
  /****                                                                 ****/
  /****                          F A C E S                              ****/
  /****                                                                 ****/
  /****                                                                 ****/
  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/


#undef  PAIR_TAG
#define PAIR_TAG( left, right )  ( ( (FT_ULong)left << 16 ) | \
                                     (FT_ULong)right        )


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Get_Kerning                                                        */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A driver method used to return the kerning vector between two      */
  /*    glyphs of the same face.                                           */
  /*                                                                       */
  /* <Input>                                                               */
  /*    face        :: A handle to the source face object.                 */
  /*                                                                       */
  /*    left_glyph  :: The index of the left glyph in the kern pair.       */
  /*                                                                       */
  /*    right_glyph :: The index of the right glyph in the kern pair.      */
  /*                                                                       */
  /* <Output>                                                              */
  /*    kerning     :: The kerning vector.  This is in font units for      */
  /*                   scalable formats, and in pixels for fixed-sizes     */
  /*                   formats.                                            */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  /* <Note>                                                                */
  /*    Only horizontal layouts (left-to-right & right-to-left) are        */
  /*    supported by this function.  Other layouts, or more sophisticated  */
  /*    kernings, are out of scope of this method (the basic driver        */
  /*    interface is meant to be simple).                                  */
  /*                                                                       */
  /*    They can be implemented by format-specific interfaces.             */
  /*                                                                       */
  static FT_Error
  Get_Kerning( TT_Face     face,
               FT_UInt     left_glyph,
               FT_UInt     right_glyph,
               FT_Vector*  kerning )
  {
    TT_Kern0_Pair  pair;


    if ( !face )
      return TT_Err_Invalid_Face_Handle;

    kerning->x = 0;
    kerning->y = 0;

    if ( face->kern_pairs )
    {
      /* there are some kerning pairs in this font file! */
      FT_ULong  search_tag = PAIR_TAG( left_glyph, right_glyph );
      FT_Long   left, right;


      left  = 0;
      right = face->num_kern_pairs - 1;

      while ( left <= right )
      {
        FT_Long   middle = left + ( ( right - left ) >> 1 );
        FT_ULong  cur_pair;


        pair     = face->kern_pairs + middle;
        cur_pair = PAIR_TAG( pair->left, pair->right );

        if ( cur_pair == search_tag )
          goto Found;

        if ( cur_pair < search_tag )
          left = middle + 1;
        else
          right = middle - 1;
      }
    }

  Exit:
    return TT_Err_Ok;

  Found:
    kerning->x = pair->value;
    goto Exit;
  }


#undef PAIR_TAG


  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/
  /****                                                                 ****/
  /****                                                                 ****/
  /****                           S I Z E S                             ****/
  /****                                                                 ****/
  /****                                                                 ****/
  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Set_Char_Sizes                                                     */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A driver method used to reset a size's character sizes (horizontal */
  /*    and vertical) expressed in fractional points.                      */
  /*                                                                       */
  /* <Input>                                                               */
  /*    char_width      :: The character width expressed in 26.6           */
  /*                       fractional points.                              */
  /*                                                                       */
  /*    char_height     :: The character height expressed in 26.6          */
  /*                       fractional points.                              */
  /*                                                                       */
  /*    horz_resolution :: The horizontal resolution of the output device. */
  /*                                                                       */
  /*    vert_resolution :: The vertical resolution of the output device.   */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    size            :: A handle to the target size object.             */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  static FT_Error
  Set_Char_Sizes( TT_Size     size,
                  FT_F26Dot6  char_width,
                  FT_F26Dot6  char_height,
                  FT_UInt     horz_resolution,
                  FT_UInt     vert_resolution )
  {
    FT_Size_Metrics*  metrics  = &size->root.metrics;
    FT_Size_Metrics*  metrics2 = &size->metrics;
    TT_Face           face     = (TT_Face)size->root.face;
    FT_Long           dim_x, dim_y;


    *metrics2 = *metrics;

    /* This bit flag, when set, indicates that the pixel size must be */
    /* truncated to an integer.  Nearly all TrueType fonts have this  */
    /* bit set, as hinting won't work really well otherwise.          */
    /*                                                                */
    if ( ( face->header.Flags & 8 ) != 0 )
    {
     /* we need to use rounding in the following computations. Otherwise,
      * the resulting hinted outlines will be very slightly distorted
      */
      dim_x = ( ( char_width  * horz_resolution + (36+32*72) ) / 72 ) & -64;