freetype2/include/freetype/ftgasp.h

/****************************************************************************
 *
 * ftgasp.h
 *
 *   Access of TrueType's 'gasp' table (specification).
 *
 * Copyright (C) 2007-2021 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.
 *
 */


#ifndef FTGASP_H_
#define FTGASP_H_

#include <freetype/freetype.h>

#ifdef FREETYPE_H
#error "freetype.h of FreeType 1 has been loaded!"
#error "Please fix the directory search order for header files"
#error "so that freetype.h of FreeType 2 is found first."
#endif


FT_BEGIN_HEADER


  /**************************************************************************
   *
   * @section:
   *   gasp_table
   *
   * @title:
   *   Gasp Table
   *
   * @abstract:
   *   Retrieving TrueType 'gasp' table entries.
   *
   * @description:
   *   The function @FT_Get_Gasp can be used to query a TrueType or OpenType
   *   font for specific entries in its 'gasp' table, if any.  This is mainly
   *   useful when implementing native TrueType hinting with the bytecode
   *   interpreter to duplicate the Windows text rendering results.
   */

  /**************************************************************************
   *
   * @enum:
   *   FT_GASP_XXX
   *
   * @description:
   *   A list of values and/or bit-flags returned by the @FT_Get_Gasp
   *   function.
   *
   * @values:
   *   FT_GASP_NO_TABLE ::
   *     This special value means that there is no GASP table in this face.
   *     It is up to the client to decide what to do.
   *
   *   FT_GASP_DO_GRIDFIT ::
   *     Grid-fitting and hinting should be performed at the specified ppem.
   *     This **really** means TrueType bytecode interpretation.  If this bit
   *     is not set, no hinting gets applied.
   *
   *   FT_GASP_DO_GRAY ::
   *     Anti-aliased rendering should be performed at the specified ppem.
   *     If not set, do monochrome rendering.
   *
   *   FT_GASP_SYMMETRIC_SMOOTHING ::
   *     If set, smoothing along multiple axes must be used with ClearType.
   *
   *   FT_GASP_SYMMETRIC_GRIDFIT ::
   *     Grid-fitting must be used with ClearType's symmetric smoothing.
   *
   * @note:
   *   The bit-flags `FT_GASP_DO_GRIDFIT` and `FT_GASP_DO_GRAY` are to be
   *   used for standard font rasterization only.  Independently of that,
   *   `FT_GASP_SYMMETRIC_SMOOTHING` and `FT_GASP_SYMMETRIC_GRIDFIT` are to
   *   be used if ClearType is enabled (and `FT_GASP_DO_GRIDFIT` and
   *   `FT_GASP_DO_GRAY` are consequently ignored).
   *
   *   'ClearType' is Microsoft's implementation of LCD rendering, partly
   *   protected by patents.
   *
   * @since:
   *   2.3.0
   */
#define FT_GASP_NO_TABLE               -1
#define FT_GASP_DO_GRIDFIT           0x01
#define FT_GASP_DO_GRAY              0x02
#define FT_GASP_SYMMETRIC_GRIDFIT    0x04
#define FT_GASP_SYMMETRIC_SMOOTHING  0x08


  /**************************************************************************
   *
   * @function:
   *   FT_Get_Gasp
   *
   * @description:
   *   For a TrueType or OpenType font file, return the rasterizer behaviour
   *   flags from the font's 'gasp' table corresponding to a given character
   *   pixel size.
   *
   * @input:
   *   face ::
   *     The source face handle.
   *
   *   ppem ::
   *     The vertical character pixel size.
   *
   * @return:
   *   Bit flags (see @FT_GASP_XXX), or @FT_GASP_NO_TABLE if there is no
   *   'gasp' table in the face.
   *
   * @note:
   *   If you want to use the MM functionality of OpenType variation fonts
   *   (i.e., using @FT_Set_Var_Design_Coordinates and friends), call this
   *   function **after** setting an instance since the return values can
   *   change.
   *
   * @since:
   *   2.3.0
   */
  FT_EXPORT( FT_Int )
  FT_Get_Gasp( FT_Face  face,
               FT_UInt  ppem );

  /* */


FT_END_HEADER

#endif /* FTGASP_H_ */


/* END */