aboutsummaryrefslogtreecommitdiff
path: root/freetype/include/freetype/ftincrem.h
blob: 209cd060cbaff3363ee1a39b76448793f4804b78 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
/***************************************************************************/
/*                                                                         */
/*  ftincrem.h                                                             */
/*                                                                         */
/*    FreeType incremental loading (specification).                        */
/*                                                                         */
/*  Copyright 2002, 2003, 2006, 2007, 2008, 2010 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 __FTINCREM_H__
#define __FTINCREM_H__

#include <ft2build.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:
   *    incremental
   *
   * @title:
   *    Incremental Loading
   *
   * @abstract:
   *    Custom Glyph Loading.
   *
   * @description:
   *   This section contains various functions used to perform so-called
   *   `incremental' glyph loading.  This is a mode where all glyphs loaded
   *   from a given @FT_Face are provided by the client application,
   *
   *   Apart from that, all other tables are loaded normally from the font
   *   file.  This mode is useful when FreeType is used within another
   *   engine, e.g., a PostScript Imaging Processor.
   *
   *   To enable this mode, you must use @FT_Open_Face, passing an
   *   @FT_Parameter with the @FT_PARAM_TAG_INCREMENTAL tag and an
   *   @FT_Incremental_Interface value.  See the comments for
   *   @FT_Incremental_InterfaceRec for an example.
   *
   */


  /***************************************************************************
   *
   * @type:
   *   FT_Incremental
   *
   * @description:
   *   An opaque type describing a user-provided object used to implement
   *   `incremental' glyph loading within FreeType.  This is used to support
   *   embedded fonts in certain environments (e.g., PostScript interpreters),
   *   where the glyph data isn't in the font file, or must be overridden by
   *   different values.
   *
   * @note:
   *   It is up to client applications to create and implement @FT_Incremental
   *   objects, as long as they provide implementations for the methods
   *   @FT_Incremental_GetGlyphDataFunc, @FT_Incremental_FreeGlyphDataFunc
   *   and @FT_Incremental_GetGlyphMetricsFunc.
   *
   *   See the description of @FT_Incremental_InterfaceRec to understand how
   *   to use incremental objects with FreeType.
   *
   */
  typedef struct FT_IncrementalRec_*  FT_Incremental;


  /***************************************************************************
   *
   * @struct:
   *   FT_Incremental_MetricsRec
   *
   * @description:
   *   A small structure used to contain the basic glyph metrics returned
   *   by the @FT_Incremental_GetGlyphMetricsFunc method.
   *
   * @fields:
   *   bearing_x ::
   *     Left bearing, in font units.
   *
   *   bearing_y ::
   *     Top bearing, in font units.
   *
   *   advance ::
   *     Horizontal component of glyph advance, in font units.
   *
   *   advance_v ::
   *     Vertical component of glyph advance, in font units.
   *
   * @note:
   *   These correspond to horizontal or vertical metrics depending on the
   *   value of the `vertical' argument to the function
   *   @FT_Incremental_GetGlyphMetricsFunc.
   *
   */
  typedef struct  FT_Incremental_MetricsRec_
  {
    FT_Long  bearing_x;
    FT_Long  bearing_y;
    FT_Long  advance;
    FT_Long  advance_v;     /* since 2.3.12 */

  } FT_Incremental_MetricsRec;


  /***************************************************************************
   *
   * @struct:
   *   FT_Incremental_Metrics
   *
   * @description:
   *   A handle to an @FT_Incremental_MetricsRec structure.
   *
   */
   typedef struct FT_Incremental_MetricsRec_*  FT_Incremental_Metrics;


  /***************************************************************************
   *
   * @type:
   *   FT_Incremental_GetGlyphDataFunc
   *
   * @description:
   *   A function called by FreeType to access a given glyph's data bytes
   *   during @FT_Load_Glyph or @FT_Load_Char if incremental loading is
   *   enabled.
   *
   *   Note that the format of the glyph's data bytes depends on the font
   *   file format.  For TrueType, it must correspond to the raw bytes within
   *   the `glyf' table.  For PostScript formats, it must correspond to the
   *   *unencrypted* charstring bytes, without any `lenIV' header.  It is
   *   undefined for any other format.
   *
   * @input:
   *   incremental ::
   *     Handle to an opaque @FT_Incremental handle provided by the client
   *     application.
   *
   *   glyph_index ::
   *     Index of relevant glyph.
   *
   * @output:
   *   adata ::
   *     A structure describing the returned glyph data bytes (which will be
   *     accessed as a read-only byte block).
   *
   * @return:
   *   FreeType error code.  0~means success.
   *
   * @note:
   *   If this function returns successfully the method
   *   @FT_Incremental_FreeGlyphDataFunc will be called later to release
   *   the data bytes.
   *
   *   Nested calls to @FT_Incremental_GetGlyphDataFunc can happen for
   *   compound glyphs.
   *
   */
  typedef FT_Error
  (*FT_Incremental_GetGlyphDataFunc)( FT_Incremental  incremental,
                                      FT_UInt         glyph_index,
                                      FT_Data*        adata );


  /***************************************************************************
   *
   * @type:
   *   FT_Incremental_FreeGlyphDataFunc
   *
   * @description:
   *   A function used to release the glyph data bytes returned by a
   *   successful call to @FT_Incremental_GetGlyphDataFunc.
   *
   * @input:
   *   incremental ::
   *     A handle to an opaque @FT_Incremental handle provided by the client
   *     application.
   *
   *   data ::
   *     A structure describing the glyph data bytes (which will be accessed
   *     as a read-only byte block).
   *
   */
  typedef void
  (*FT_Incremental_FreeGlyphDataFunc)( FT_Incremental  incremental,
                                       FT_Data*        data );


  /***************************************************************************
   *
   * @type:
   *   FT_Incremental_GetGlyphMetricsFunc
   *
   * @description:
   *   A function used to retrieve the basic metrics of a given glyph index
   *   before accessing its data.  This is necessary because, in certain
   *   formats like TrueType, the metrics are stored in a different place from
   *   the glyph images proper.
   *
   * @input:
   *   incremental ::
   *     A handle to an opaque @FT_Incremental handle provided by the client
   *     application.
   *
   *   glyph_index ::
   *     Index of relevant glyph.
   *
   *   vertical ::
   *     If true, return vertical metrics.
   *
   *   ametrics ::
   *     This parameter is used for both input and output.
   *     The original glyph metrics, if any, in font units.  If metrics are
   *     not available all the values must be set to zero.
   *
   * @output:
   *   ametrics ::
   *     The replacement glyph metrics in font units.
   *
   */
  typedef FT_Error
  (*FT_Incremental_GetGlyphMetricsFunc)
                      ( FT_Incremental              incremental,
                        FT_UInt                     glyph_index,
                        FT_Bool                     vertical,
                        FT_Incremental_MetricsRec  *ametrics );


  /**************************************************************************
   *
   * @struct:
   *   FT_Incremental_FuncsRec
   *
   * @description:
   *   A table of functions for accessing fonts that load data
   *   incrementally.  Used in @FT_Incremental_InterfaceRec.
   *
   * @fields:
   *   get_glyph_data ::
   *     The function to get glyph data.  Must not be null.
   *
   *   free_glyph_data ::
   *     The function to release glyph data.  Must not be null.
   *
   *   get_glyph_metrics ::
   *     The function to get glyph metrics.  May be null if the font does
   *     not provide overriding glyph metrics.
   *
   */
  typedef struct  FT_Incremental_FuncsRec_
  {
    FT_Incremental_GetGlyphDataFunc     get_glyph_data;
    FT_Incremental_FreeGlyphDataFunc    free_glyph_data;
    FT_Incremental_GetGlyphMetricsFunc  get_glyph_metrics;

  } FT_Incremental_FuncsRec;


  /***************************************************************************
   *
   * @struct:
   *   FT_Incremental_InterfaceRec
   *
   * @description:
   *   A structure to be used with @FT_Open_Face to indicate that the user
   *   wants to support incremental glyph loading.  You should use it with
   *   @FT_PARAM_TAG_INCREMENTAL as in the following example:
   *
   *     {
   *       FT_Incremental_InterfaceRec  inc_int;
   *       FT_Parameter                 parameter;
   *       FT_Open_Args                 open_args;
   *
   *
   *       // set up incremental descriptor
   *       inc_int.funcs  = my_funcs;
   *       inc_int.object = my_object;
   *
   *       // set up optional parameter
   *       parameter.tag  = FT_PARAM_TAG_INCREMENTAL;
   *       parameter.data = &inc_int;
   *
   *       // set up FT_Open_Args structure
   *       open_args.flags      = FT_OPEN_PATHNAME | FT_OPEN_PARAMS;
   *       open_args.pathname   = my_font_pathname;
   *       open_args.num_params = 1;
   *       open_args.params     = &parameter; // we use one optional argument
   *
   *       // open the font
   *       error = FT_Open_Face( library, &open_args, index, &face );
   *       ...
   *     }
   *
   */
  typedef struct  FT_Incremental_InterfaceRec_
  {
    const FT_Incremental_FuncsRec*  funcs;
    FT_Incremental                  object;

  } FT_Incremental_InterfaceRec;


  /***************************************************************************
   *
   * @type:
   *   FT_Incremental_Interface
   *
   * @description:
   *   A pointer to an @FT_Incremental_InterfaceRec structure.
   *
   */
  typedef FT_Incremental_InterfaceRec*   FT_Incremental_Interface;


  /***************************************************************************
   *
   * @constant:
   *   FT_PARAM_TAG_INCREMENTAL
   *
   * @description:
   *   A constant used as the tag of @FT_Parameter structures to indicate
   *   an incremental loading object to be used by FreeType.
   *
   */
#define FT_PARAM_TAG_INCREMENTAL  FT_MAKE_TAG( 'i', 'n', 'c', 'r' )

  /* */

FT_END_HEADER

#endif /* __FTINCREM_H__ */


/* END */