1 /***************************************************************************/
5 /* FreeType incremental loading (specification). */
7 /* Copyright 2002, 2003 by */
8 /* David Turner, Robert Wilhelm, and Werner Lemberg. */
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. */
16 /***************************************************************************/
19 #ifndef __FTINCREM_H__
20 #define __FTINCREM_H__
23 #include FT_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."
35 /***************************************************************************
41 * An opaque type describing a user-provided object used to implement
42 * "incremental" glyph loading within FreeType. This is used to support
43 * embedded fonts in certain environments (e.g. Postscript interpreters),
44 * where the glyph data isn't in the font file, or must be overridden by
48 * It is up to client applications to create and implement @FT_Incremental
49 * objects, as long as they provide implementations for the methods
50 * @FT_Incremental_GetGlyphDataFunc, @FT_Incremental_FreeGlyphDataFunc
51 * and @FT_Incremental_GetGlyphMetricsFunc.
53 * See the description of @FT_Incremental_InterfaceRec to understand how
54 * to use incremental objects with FreeType.
56 typedef struct FT_IncrementalRec_* FT_Incremental;
59 /***************************************************************************
62 * FT_Incremental_Metrics
65 * A small structure used to contain the basic glyph metrics returned
66 * by the @FT_Incremental_GetGlyphMetricsFunc method.
70 * Left bearing, in font units.
73 * Top bearing, in font units.
76 * Glyph advance, in font units.
79 * These correspond to horizontal or vertical metrics depending on the
80 * value of the 'vertical' argument to the function
81 * @FT_Incremental_GetGlyphMetricsFunc.
83 typedef struct FT_Incremental_MetricsRec_
89 } FT_Incremental_MetricsRec, *FT_Incremental_Metrics;
92 /***************************************************************************
95 * FT_Incremental_GetGlyphDataFunc
98 * A function called by FreeType to access a given glyph's data bytes
99 * during @FT_Load_Glyph or @FT_Load_Char if incremental loading is
102 * Note that the format of the glyph's data bytes depends on the font
103 * file format. For TrueType, it must correspond to the raw bytes within
104 * the 'glyf' table. For Postscript formats, it must correspond to the
105 * *unencrypted* charstring bytes, without any 'lenIV' header. It is
106 * undefined for any other format.
110 * Handle to an opaque @FT_Incremental handle provided by the client
114 * Index of relevant glyph.
118 * A structure describing the returned glyph data bytes (which will be
119 * accessed as a read-only byte block).
122 * FreeType error code. 0 means success.
125 * If this function returns succesfully the method
126 * @FT_Incremental_FreeGlyphDataFunc will be called later to release
129 * Nested calls to @FT_Incremental_GetGlyphDataFunc can happen for
133 (*FT_Incremental_GetGlyphDataFunc)( FT_Incremental incremental,
138 /***************************************************************************
141 * FT_Incremental_FreeGlyphDataFunc
144 * A function used to release the glyph data bytes returned by a
145 * successful call to @FT_Incremental_GetGlyphDataFunc.
149 * A handle to an opaque @FT_Incremental handle provided by the client
153 * A structure describing the glyph data bytes (which will be accessed
154 * as a read-only byte block).
157 (*FT_Incremental_FreeGlyphDataFunc)( FT_Incremental incremental,
161 /***************************************************************************
164 * FT_Incremental_GetGlyphMetricsFunc
167 * A function used to retrieve the basic metrics of a given glyph index
168 * before accessing its data. This is necessary because, in certain
169 * formats like TrueType, the metrics are stored in a different place from
170 * the glyph images proper.
174 * A handle to an opaque @FT_Incremental handle provided by the client
178 * Index of relevant glyph.
181 * If true, return vertical metrics.
184 * This parameter is used for both input and output.
185 * The original glyph metrics, if any, in font units. If metrics are
186 * not available all the values must be set to zero.
190 * The replacement glyph metrics in font units.
194 (*FT_Incremental_GetGlyphMetricsFunc)
195 ( FT_Incremental incremental,
198 FT_Incremental_MetricsRec *ametrics );
201 /**************************************************************************
204 * FT_Incremental_FuncsRec
207 * A table of functions for accessing fonts that load data
208 * incrementally. Used in @FT_Incremental_InterfaceRec.
212 * The function to get glyph data. Must not be null.
215 * The function to release glyph data. Must not be null.
217 * get_glyph_metrics ::
218 * The function to get glyph metrics. May be null if the font does
219 * not provide overriding glyph metrics.
221 typedef struct FT_Incremental_FuncsRec_
223 FT_Incremental_GetGlyphDataFunc get_glyph_data;
224 FT_Incremental_FreeGlyphDataFunc free_glyph_data;
225 FT_Incremental_GetGlyphMetricsFunc get_glyph_metrics;
227 } FT_Incremental_FuncsRec;
230 /***************************************************************************
233 * FT_Incremental_InterfaceRec
236 * A structure to be used with @FT_Open_Face to indicate that the user
237 * wants to support incremental glyph loading. You should use it with
238 * @FT_PARAM_TAG_INCREMENTAL as in the following example:
241 * FT_Incremental_InterfaceRec inc_int;
242 * FT_Parameter parameter;
243 * FT_Open_Args open_args;
246 * // set up incremental descriptor
247 * inc_int.funcs = my_funcs;
248 * inc_int.object = my_object;
250 * // set up optional parameter
251 * parameter.tag = FT_PARAM_TAG_INCREMENTAL;
252 * parameter.data = &inc_int;
254 * // set up FT_Open_Args structure
255 * open_args.flags = FT_OPEN_PATHNAME | FT_OPEN_PARAMS;
256 * open_args.pathname = my_font_pathname;
257 * open_args.num_params = 1;
258 * open_args.params = ¶meter; // we use one optional argument
261 * error = FT_Open_Face( library, &open_args, index, &face );
265 typedef struct FT_Incremental_InterfaceRec_
267 const FT_Incremental_FuncsRec* funcs;
268 FT_Incremental object;
270 } FT_Incremental_InterfaceRec;
273 /***************************************************************************
276 * FT_PARAM_TAG_INCREMENTAL
279 * A constant used as the tag of @FT_Parameter structures to indicate
280 * an incremental loading object to be used by FreeType.
283 #define FT_PARAM_TAG_INCREMENTAL FT_MAKE_TAG( 'i', 'n', 'c', 'r' )
289 #endif /* __FTINCREM_H__ */