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1 /***************************************************************************/
2 /*                                                                         */
3 /*  autohint.h                                                             */
4 /*                                                                         */
5 /*    High-level `autohint' module-specific interface (specification).     */
6 /*                                                                         */
7 /*  Copyright 1996-2001, 2002, 2007 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   /*************************************************************************/
20   /*                                                                       */
21   /* The auto-hinter is used to load and automatically hint glyphs if a    */
22   /* format-specific hinter isn't available.                               */
23   /*                                                                       */
24   /*************************************************************************/
25 
26 
27 #ifndef __AUTOHINT_H__
28 #define __AUTOHINT_H__
29 
30 
31   /*************************************************************************/
32   /*                                                                       */
33   /* A small technical note regarding automatic hinting in order to        */
34   /* clarify this module interface.                                        */
35   /*                                                                       */
36   /* An automatic hinter might compute two kinds of data for a given face: */
37   /*                                                                       */
38   /* - global hints: Usually some metrics that describe global properties  */
39   /*                 of the face.  It is computed by scanning more or less */
40   /*                 aggressively 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).                               */
43   /*                                                                       */
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.   */
47   /*                                                                       */
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.   */
53   /*                                                                       */
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.                   */
58   /*                                                                       */
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 */
62   /* it.                                                                   */
63   /*                                                                       */
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.                                                   */
69   /*                                                                       */
70   /*************************************************************************/
71 
72 
73 #include <ft2build.h>
74 #include FT_FREETYPE_H
75 
76 
77 FT_BEGIN_HEADER
78 
79 
80   typedef struct FT_AutoHinterRec_  *FT_AutoHinter;
81 
82 
83   /*************************************************************************/
84   /*                                                                       */
85   /* <FuncType>                                                            */
86   /*    FT_AutoHinter_GlobalGetFunc                                        */
87   /*                                                                       */
88   /* <Description>                                                         */
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_GlobalDoneFunc().                                    */
93   /*                                                                       */
94   /* <Input>                                                               */
95   /*    hinter        :: A handle to the source auto-hinter.               */
96   /*                                                                       */
97   /*    face          :: A handle to the source face object.               */
98   /*                                                                       */
99   /* <Output>                                                              */
100   /*    global_hints  :: A typeless pointer to the global hints.           */
101   /*                                                                       */
102   /*    global_len    :: The size in bytes of the global hints.            */
103   /*                                                                       */
104   typedef void
105   (*FT_AutoHinter_GlobalGetFunc)( FT_AutoHinter  hinter,
106                                   FT_Face        face,
107                                   void**         global_hints,
108                                   long*          global_len );
109 
110 
111   /*************************************************************************/
112   /*                                                                       */
113   /* <FuncType>                                                            */
114   /*    FT_AutoHinter_GlobalDoneFunc                                       */
115   /*                                                                       */
116   /* <Description>                                                         */
117   /*    Discards the global hints retrieved through                        */
118   /*    FT_AutoHinter_GlobalGetFunc().  This is the only way these hints   */
119   /*    are freed from memory.                                             */
120   /*                                                                       */
121   /* <Input>                                                               */
122   /*    hinter :: A handle to the auto-hinter module.                      */
123   /*                                                                       */
124   /*    global :: A pointer to retrieved global hints to discard.          */
125   /*                                                                       */
126   typedef void
127   (*FT_AutoHinter_GlobalDoneFunc)( FT_AutoHinter  hinter,
128                                    void*          global );
129 
130 
131   /*************************************************************************/
132   /*                                                                       */
133   /* <FuncType>                                                            */
134   /*    FT_AutoHinter_GlobalResetFunc                                      */
135   /*                                                                       */
136   /* <Description>                                                         */
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).                     */
140   /*                                                                       */
141   /* <Input>                                                               */
142   /*    hinter :: A handle to the source auto-hinter.                      */
143   /*                                                                       */
144   /*    face   :: A handle to the face.                                    */
145   /*                                                                       */
146   typedef void
147   (*FT_AutoHinter_GlobalResetFunc)( FT_AutoHinter  hinter,
148                                     FT_Face        face );
149 
150 
151   /*************************************************************************/
152   /*                                                                       */
153   /* <FuncType>                                                            */
154   /*    FT_AutoHinter_GlyphLoadFunc                                        */
155   /*                                                                       */
156   /* <Description>                                                         */
157   /*    This function is used to load, scale, and automatically hint a     */
158   /*    glyph from a given face.                                           */
159   /*                                                                       */
160   /* <Input>                                                               */
161   /*    face        :: A handle to the face.                               */
162   /*                                                                       */
163   /*    glyph_index :: The glyph index.                                    */
164   /*                                                                       */
165   /*    load_flags  :: The load flags.                                     */
166   /*                                                                       */
167   /* <Note>                                                                */
168   /*    This function is capable of loading composite glyphs by hinting    */
169   /*    each sub-glyph independently (which improves quality).             */
170   /*                                                                       */
171   /*    It will call the font driver with FT_Load_Glyph(), with            */
172   /*    FT_LOAD_NO_SCALE set.                                              */
173   /*                                                                       */
174   typedef FT_Error
175   (*FT_AutoHinter_GlyphLoadFunc)( FT_AutoHinter  hinter,
176                                   FT_GlyphSlot   slot,
177                                   FT_Size        size,
178                                   FT_UInt        glyph_index,
179                                   FT_Int32       load_flags );
180 
181 
182   /*************************************************************************/
183   /*                                                                       */
184   /* <Struct>                                                              */
185   /*    FT_AutoHinter_ServiceRec                                           */
186   /*                                                                       */
187   /* <Description>                                                         */
188   /*    The auto-hinter module's interface.                                */
189   /*                                                                       */
190   typedef struct  FT_AutoHinter_ServiceRec_
191   {
192     FT_AutoHinter_GlobalResetFunc  reset_face;
193     FT_AutoHinter_GlobalGetFunc    get_global_hints;
194     FT_AutoHinter_GlobalDoneFunc   done_global_hints;
195     FT_AutoHinter_GlyphLoadFunc    load_glyph;
196 
197   } FT_AutoHinter_ServiceRec, *FT_AutoHinter_Service;
198 
199 #ifndef FT_CONFIG_OPTION_PIC
200 
201 #define FT_DEFINE_AUTOHINTER_SERVICE(class_, reset_face_, get_global_hints_, \
202                                      done_global_hints_, load_glyph_)        \
203   FT_CALLBACK_TABLE_DEF                                                      \
204   const FT_AutoHinter_ServiceRec class_ =                                    \
205   {                                                                          \
206     reset_face_, get_global_hints_, done_global_hints_, load_glyph_          \
207   };
208 
209 #else /* FT_CONFIG_OPTION_PIC */
210 
211 #define FT_DEFINE_AUTOHINTER_SERVICE(class_, reset_face_, get_global_hints_, \
212                                      done_global_hints_, load_glyph_)        \
213   void                                                                       \
214   FT_Init_Class_##class_( FT_Library library,                                \
215                           FT_AutoHinter_ServiceRec* clazz)                   \
216   {                                                                          \
217     FT_UNUSED(library);                                                      \
218     clazz->reset_face = reset_face_;                                         \
219     clazz->get_global_hints = get_global_hints_;                             \
220     clazz->done_global_hints = done_global_hints_;                           \
221     clazz->load_glyph = load_glyph_;                                         \
222   }
223 
224 #endif /* FT_CONFIG_OPTION_PIC */
225 
226 FT_END_HEADER
227 
228 #endif /* __AUTOHINT_H__ */
229 
230 
231 /* END */
232