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| author | John Tsiombikas <nuclear@member.fsf.org> |
|---|---|
| date | Sun, 02 Feb 2014 00:35:22 +0200 |
| parents | |
| children |
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1 /***************************************************************************/
2 /* */
3 /* ftincrem.h */
4 /* */
5 /* FreeType incremental loading (specification). */
6 /* */
7 /* Copyright 2002, 2003, 2006, 2007, 2008, 2010 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 /***************************************************************************/
19 #ifndef __FTINCREM_H__
20 #define __FTINCREM_H__
22 #include <ft2build.h>
23 #include FT_FREETYPE_H
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
32 FT_BEGIN_HEADER
34 /***************************************************************************
35 *
36 * @section:
37 * incremental
38 *
39 * @title:
40 * Incremental Loading
41 *
42 * @abstract:
43 * Custom Glyph Loading.
44 *
45 * @description:
46 * This section contains various functions used to perform so-called
47 * `incremental' glyph loading. This is a mode where all glyphs loaded
48 * from a given @FT_Face are provided by the client application,
49 *
50 * Apart from that, all other tables are loaded normally from the font
51 * file. This mode is useful when FreeType is used within another
52 * engine, e.g., a PostScript Imaging Processor.
53 *
54 * To enable this mode, you must use @FT_Open_Face, passing an
55 * @FT_Parameter with the @FT_PARAM_TAG_INCREMENTAL tag and an
56 * @FT_Incremental_Interface value. See the comments for
57 * @FT_Incremental_InterfaceRec for an example.
58 *
59 */
62 /***************************************************************************
63 *
64 * @type:
65 * FT_Incremental
66 *
67 * @description:
68 * An opaque type describing a user-provided object used to implement
69 * `incremental' glyph loading within FreeType. This is used to support
70 * embedded fonts in certain environments (e.g., PostScript interpreters),
71 * where the glyph data isn't in the font file, or must be overridden by
72 * different values.
73 *
74 * @note:
75 * It is up to client applications to create and implement @FT_Incremental
76 * objects, as long as they provide implementations for the methods
77 * @FT_Incremental_GetGlyphDataFunc, @FT_Incremental_FreeGlyphDataFunc
78 * and @FT_Incremental_GetGlyphMetricsFunc.
79 *
80 * See the description of @FT_Incremental_InterfaceRec to understand how
81 * to use incremental objects with FreeType.
82 *
83 */
84 typedef struct FT_IncrementalRec_* FT_Incremental;
87 /***************************************************************************
88 *
89 * @struct:
90 * FT_Incremental_MetricsRec
91 *
92 * @description:
93 * A small structure used to contain the basic glyph metrics returned
94 * by the @FT_Incremental_GetGlyphMetricsFunc method.
95 *
96 * @fields:
97 * bearing_x ::
98 * Left bearing, in font units.
99 *
100 * bearing_y ::
101 * Top bearing, in font units.
102 *
103 * advance ::
104 * Horizontal component of glyph advance, in font units.
105 *
106 * advance_v ::
107 * Vertical component of glyph advance, in font units.
108 *
109 * @note:
110 * These correspond to horizontal or vertical metrics depending on the
111 * value of the `vertical' argument to the function
112 * @FT_Incremental_GetGlyphMetricsFunc.
113 *
114 */
115 typedef struct FT_Incremental_MetricsRec_
116 {
117 FT_Long bearing_x;
118 FT_Long bearing_y;
119 FT_Long advance;
120 FT_Long advance_v; /* since 2.3.12 */
122 } FT_Incremental_MetricsRec;
125 /***************************************************************************
126 *
127 * @struct:
128 * FT_Incremental_Metrics
129 *
130 * @description:
131 * A handle to an @FT_Incremental_MetricsRec structure.
132 *
133 */
134 typedef struct FT_Incremental_MetricsRec_* FT_Incremental_Metrics;
137 /***************************************************************************
138 *
139 * @type:
140 * FT_Incremental_GetGlyphDataFunc
141 *
142 * @description:
143 * A function called by FreeType to access a given glyph's data bytes
144 * during @FT_Load_Glyph or @FT_Load_Char if incremental loading is
145 * enabled.
146 *
147 * Note that the format of the glyph's data bytes depends on the font
148 * file format. For TrueType, it must correspond to the raw bytes within
149 * the `glyf' table. For PostScript formats, it must correspond to the
150 * *unencrypted* charstring bytes, without any `lenIV' header. It is
151 * undefined for any other format.
152 *
153 * @input:
154 * incremental ::
155 * Handle to an opaque @FT_Incremental handle provided by the client
156 * application.
157 *
158 * glyph_index ::
159 * Index of relevant glyph.
160 *
161 * @output:
162 * adata ::
163 * A structure describing the returned glyph data bytes (which will be
164 * accessed as a read-only byte block).
165 *
166 * @return:
167 * FreeType error code. 0~means success.
168 *
169 * @note:
170 * If this function returns successfully the method
171 * @FT_Incremental_FreeGlyphDataFunc will be called later to release
172 * the data bytes.
173 *
174 * Nested calls to @FT_Incremental_GetGlyphDataFunc can happen for
175 * compound glyphs.
176 *
177 */
178 typedef FT_Error
179 (*FT_Incremental_GetGlyphDataFunc)( FT_Incremental incremental,
180 FT_UInt glyph_index,
181 FT_Data* adata );
184 /***************************************************************************
185 *
186 * @type:
187 * FT_Incremental_FreeGlyphDataFunc
188 *
189 * @description:
190 * A function used to release the glyph data bytes returned by a
191 * successful call to @FT_Incremental_GetGlyphDataFunc.
192 *
193 * @input:
194 * incremental ::
195 * A handle to an opaque @FT_Incremental handle provided by the client
196 * application.
197 *
198 * data ::
199 * A structure describing the glyph data bytes (which will be accessed
200 * as a read-only byte block).
201 *
202 */
203 typedef void
204 (*FT_Incremental_FreeGlyphDataFunc)( FT_Incremental incremental,
205 FT_Data* data );
208 /***************************************************************************
209 *
210 * @type:
211 * FT_Incremental_GetGlyphMetricsFunc
212 *
213 * @description:
214 * A function used to retrieve the basic metrics of a given glyph index
215 * before accessing its data. This is necessary because, in certain
216 * formats like TrueType, the metrics are stored in a different place from
217 * the glyph images proper.
218 *
219 * @input:
220 * incremental ::
221 * A handle to an opaque @FT_Incremental handle provided by the client
222 * application.
223 *
224 * glyph_index ::
225 * Index of relevant glyph.
226 *
227 * vertical ::
228 * If true, return vertical metrics.
229 *
230 * ametrics ::
231 * This parameter is used for both input and output.
232 * The original glyph metrics, if any, in font units. If metrics are
233 * not available all the values must be set to zero.
234 *
235 * @output:
236 * ametrics ::
237 * The replacement glyph metrics in font units.
238 *
239 */
240 typedef FT_Error
241 (*FT_Incremental_GetGlyphMetricsFunc)
242 ( FT_Incremental incremental,
243 FT_UInt glyph_index,
244 FT_Bool vertical,
245 FT_Incremental_MetricsRec *ametrics );
248 /**************************************************************************
249 *
250 * @struct:
251 * FT_Incremental_FuncsRec
252 *
253 * @description:
254 * A table of functions for accessing fonts that load data
255 * incrementally. Used in @FT_Incremental_InterfaceRec.
256 *
257 * @fields:
258 * get_glyph_data ::
259 * The function to get glyph data. Must not be null.
260 *
261 * free_glyph_data ::
262 * The function to release glyph data. Must not be null.
263 *
264 * get_glyph_metrics ::
265 * The function to get glyph metrics. May be null if the font does
266 * not provide overriding glyph metrics.
267 *
268 */
269 typedef struct FT_Incremental_FuncsRec_
270 {
271 FT_Incremental_GetGlyphDataFunc get_glyph_data;
272 FT_Incremental_FreeGlyphDataFunc free_glyph_data;
273 FT_Incremental_GetGlyphMetricsFunc get_glyph_metrics;
275 } FT_Incremental_FuncsRec;
278 /***************************************************************************
279 *
280 * @struct:
281 * FT_Incremental_InterfaceRec
282 *
283 * @description:
284 * A structure to be used with @FT_Open_Face to indicate that the user
285 * wants to support incremental glyph loading. You should use it with
286 * @FT_PARAM_TAG_INCREMENTAL as in the following example:
287 *
288 * {
289 * FT_Incremental_InterfaceRec inc_int;
290 * FT_Parameter parameter;
291 * FT_Open_Args open_args;
292 *
293 *
294 * // set up incremental descriptor
295 * inc_int.funcs = my_funcs;
296 * inc_int.object = my_object;
297 *
298 * // set up optional parameter
299 * parameter.tag = FT_PARAM_TAG_INCREMENTAL;
300 * parameter.data = &inc_int;
301 *
302 * // set up FT_Open_Args structure
303 * open_args.flags = FT_OPEN_PATHNAME | FT_OPEN_PARAMS;
304 * open_args.pathname = my_font_pathname;
305 * open_args.num_params = 1;
306 * open_args.params = ¶meter; // we use one optional argument
307 *
308 * // open the font
309 * error = FT_Open_Face( library, &open_args, index, &face );
310 * ...
311 * }
312 *
313 */
314 typedef struct FT_Incremental_InterfaceRec_
315 {
316 const FT_Incremental_FuncsRec* funcs;
317 FT_Incremental object;
319 } FT_Incremental_InterfaceRec;
322 /***************************************************************************
323 *
324 * @type:
325 * FT_Incremental_Interface
326 *
327 * @description:
328 * A pointer to an @FT_Incremental_InterfaceRec structure.
329 *
330 */
331 typedef FT_Incremental_InterfaceRec* FT_Incremental_Interface;
334 /***************************************************************************
335 *
336 * @constant:
337 * FT_PARAM_TAG_INCREMENTAL
338 *
339 * @description:
340 * A constant used as the tag of @FT_Parameter structures to indicate
341 * an incremental loading object to be used by FreeType.
342 *
343 */
344 #define FT_PARAM_TAG_INCREMENTAL FT_MAKE_TAG( 'i', 'n', 'c', 'r' )
346 /* */
348 FT_END_HEADER
350 #endif /* __FTINCREM_H__ */
353 /* END */