1 /***************************************************************************/
5 /* High-level `autohint' module-specific interface (specification). */
7 /* Copyright 1996-2001 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 /*************************************************************************/
21 /* The auto-hinter is used to load and automatically hint glyphs if a */
22 /* format-specific hinter isn't available. */
24 /*************************************************************************/
27 #ifndef __AUTOHINT_H__
28 #define __AUTOHINT_H__
31 /*************************************************************************/
33 /* A small technical note regarding automatic hinting in order to */
34 /* clarify this module interface. */
36 /* An automatic hinter might compute two kinds of data for a given face: */
38 /* - global hints: Usually some metrics that describe global properties */
39 /* of the face. It is computed by scanning more or less */
40 /* agressively the glyphs in the face, and thus can be */
41 /* very slow to compute (even if the size of global */
42 /* hints is really small). */
44 /* - glyph hints: These describe some important features of the glyph */
45 /* outline, as well as how to align them. They are */
46 /* generally much faster to compute than global hints. */
48 /* The current FreeType auto-hinter does a pretty good job while */
49 /* performing fast computations for both global and glyph hints. */
50 /* However, we might be interested in introducing more complex and */
51 /* powerful algorithms in the future, like the one described in the John */
52 /* D. Hobby paper, which unfortunately requires a lot more horsepower. */
54 /* Because a sufficiently sophisticated font management system would */
55 /* typically implement an LRU cache of opened face objects to reduce */
56 /* memory usage, it is a good idea to be able to avoid recomputing */
57 /* global hints every time the same face is re-opened. */
59 /* We thus provide the ability to cache global hints outside of the face */
60 /* object, in order to speed up font re-opening time. Of course, this */
61 /* feature is purely optional, so most client programs won't even notice */
64 /* I initially thought that it would be a good idea to cache the glyph */
65 /* hints too. However, my general idea now is that if you really need */
66 /* to cache these too, you are simply in need of a new font format, */
67 /* where all this information could be stored within the font file and */
68 /* decoded on the fly. */
70 /*************************************************************************/
74 #include FT_FREETYPE_H
80 typedef struct FT_AutoHinterRec_ *FT_AutoHinter;
83 /*************************************************************************/
86 /* FT_AutoHinter_Get_Global_Func */
89 /* Retrieves the global hints computed for a given face object the */
90 /* resulting data is dissociated from the face and will survive a */
91 /* call to FT_Done_Face(). It must be discarded through the API */
92 /* FT_AutoHinter_Done_Global_Func(). */
95 /* hinter :: A handle to the source auto-hinter. */
97 /* face :: A handle to the source face object. */
100 /* global_hints :: A typeless pointer to the global hints. */
102 /* global_len :: The size in bytes of the global hints. */
105 (*FT_AutoHinter_Get_Global_Func)( FT_AutoHinter hinter,
111 /*************************************************************************/
114 /* FT_AutoHinter_Done_Global_Func */
117 /* Discards the global hints retrieved through */
118 /* FT_AutoHinter_Get_Global_Func(). This is the only way these hints */
119 /* are freed from memory. */
122 /* hinter :: A handle to the auto-hinter module. */
124 /* global :: A pointer to retrieved global hints to discard. */
127 (*FT_AutoHinter_Done_Global_Func)( FT_AutoHinter hinter,
131 /*************************************************************************/
134 /* FT_AutoHinter_Reset_Func */
137 /* This function is used to recompute the global metrics in a given */
138 /* font. This is useful when global font data changes (e.g. Multiple */
139 /* Masters fonts where blend coordinates change). */
142 /* hinter :: A handle to the source auto-hinter. */
144 /* face :: A handle to the face. */
147 (*FT_AutoHinter_Reset_Func)( FT_AutoHinter hinter,
151 /*************************************************************************/
154 /* FT_AutoHinter_Load_Func */
157 /* This function is used to load, scale, and automatically hint a */
158 /* glyph from a given face. */
161 /* face :: A handle to the face. */
162 /* glyph_index :: The glyph index. */
163 /* load_flags :: The load flags. */
166 /* This function is capable of loading composite glyphs by hinting */
167 /* each sub-glyph independently (which improves quality). */
169 /* It will call the font driver with FT_Load_Glyph(), with */
170 /* FT_LOAD_NO_SCALE set. */
173 (*FT_AutoHinter_Load_Func)( FT_AutoHinter hinter,
177 FT_ULong load_flags );
180 /*************************************************************************/
183 /* FT_AutoHinter_Interface */
186 /* The auto-hinter module's interface. */
188 typedef struct FT_AutoHinter_Interface
190 FT_AutoHinter_Reset_Func reset_face;
191 FT_AutoHinter_Load_Func load_glyph;
193 FT_AutoHinter_Get_Global_Func get_global_hints;
194 FT_AutoHinter_Done_Global_Func done_global_hints;
196 } FT_AutoHinter_Interface;
201 #endif /* __AUTOHINT_H__ */