1/***************************************************************************/
2/* */
3/* ftgasp.h */
4/* */
5/* Access of TrueType's `gasp' table (specification). */
6/* */
7/* Copyright 2007-2018 by */
8/* David Turner, Robert Wilhelm, and Werner Lemberg. */
9/* */
10/* This file is part of the FreeType project, and may only be used, */
11/* modified, and distributed under the terms of the FreeType project */
12/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
13/* this file you indicate that you have read the license and */
14/* understand and accept it fully. */
15/* */
16/***************************************************************************/
17
18
19#ifndef FTGASP_H_
20#define FTGASP_H_
21
22#include <ft2build.h>
23#include FT_FREETYPE_H
24
25#ifdef FREETYPE_H
26#error "freetype.h of FreeType 1 has been loaded!"
27#error "Please fix the directory search order for header files"
28#error "so that freetype.h of FreeType 2 is found first."
29#endif
30
31
32FT_BEGIN_HEADER
33
34
35 /***************************************************************************
36 *
37 * @section:
38 * gasp_table
39 *
40 * @title:
41 * Gasp Table
42 *
43 * @abstract:
44 * Retrieving TrueType `gasp' table entries.
45 *
46 * @description:
47 * The function @FT_Get_Gasp can be used to query a TrueType or OpenType
48 * font for specific entries in its `gasp' table, if any. This is
49 * mainly useful when implementing native TrueType hinting with the
50 * bytecode interpreter to duplicate the Windows text rendering results.
51 */
52
53 /*************************************************************************
54 *
55 * @enum:
56 * FT_GASP_XXX
57 *
58 * @description:
59 * A list of values and/or bit-flags returned by the @FT_Get_Gasp
60 * function.
61 *
62 * @values:
63 * FT_GASP_NO_TABLE ::
64 * This special value means that there is no GASP table in this face.
65 * It is up to the client to decide what to do.
66 *
67 * FT_GASP_DO_GRIDFIT ::
68 * Grid-fitting and hinting should be performed at the specified ppem.
69 * This *really* means TrueType bytecode interpretation. If this bit
70 * is not set, no hinting gets applied.
71 *
72 * FT_GASP_DO_GRAY ::
73 * Anti-aliased rendering should be performed at the specified ppem.
74 * If not set, do monochrome rendering.
75 *
76 * FT_GASP_SYMMETRIC_SMOOTHING ::
77 * If set, smoothing along multiple axes must be used with ClearType.
78 *
79 * FT_GASP_SYMMETRIC_GRIDFIT ::
80 * Grid-fitting must be used with ClearType's symmetric smoothing.
81 *
82 * @note:
83 * The bit-flags `FT_GASP_DO_GRIDFIT' and `FT_GASP_DO_GRAY' are to be
84 * used for standard font rasterization only. Independently of that,
85 * `FT_GASP_SYMMETRIC_SMOOTHING' and `FT_GASP_SYMMETRIC_GRIDFIT' are to
86 * be used if ClearType is enabled (and `FT_GASP_DO_GRIDFIT' and
87 * `FT_GASP_DO_GRAY' are consequently ignored).
88 *
89 * `ClearType' is Microsoft's implementation of LCD rendering, partly
90 * protected by patents.
91 *
92 * @since:
93 * 2.3.0
94 */
95#define FT_GASP_NO_TABLE -1
96#define FT_GASP_DO_GRIDFIT 0x01
97#define FT_GASP_DO_GRAY 0x02
98#define FT_GASP_SYMMETRIC_GRIDFIT 0x04
99#define FT_GASP_SYMMETRIC_SMOOTHING 0x08
100
101
102 /*************************************************************************
103 *
104 * @func:
105 * FT_Get_Gasp
106 *
107 * @description:
108 * For a TrueType or OpenType font file, return the rasterizer behaviour
109 * flags from the font's `gasp' table corresponding to a given
110 * character pixel size.
111 *
112 * @input:
113 * face :: The source face handle.
114 *
115 * ppem :: The vertical character pixel size.
116 *
117 * @return:
118 * Bit flags (see @FT_GASP_XXX), or @FT_GASP_NO_TABLE if there is no
119 * `gasp' table in the face.
120 *
121 * @note:
122 * If you want to use the MM functionality of OpenType variation fonts
123 * (i.e., using @FT_Set_Var_Design_Coordinates and friends), call this
124 * function *after* setting an instance since the return values can
125 * change.
126 *
127 * @since:
128 * 2.3.0
129 */
130 FT_EXPORT( FT_Int )
131 FT_Get_Gasp( FT_Face face,
132 FT_UInt ppem );
133
134 /* */
135
136
137FT_END_HEADER
138
139#endif /* FTGASP_H_ */
140
141
142/* END */
143