XFA: merge patch from CL 817753002
[pdfium.git] / core / src / fxge / fx_freetype / fxft2.5.01 / include / freetype / internal / autohint.h
1 /***************************************************************************/
2 /*                                                                         */
3 /*  autohint.h                                                             */
4 /*                                                                         */
5 /*    High-level `autohint' module-specific interface (specification).     */
6 /*                                                                         */
7 /*  Copyright 1996-2002, 2007, 2009, 2012 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 "../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   /*    Retrieve 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   /*    Discard 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_InterfaceRec                                         */
186   /*                                                                       */
187   /* <Description>                                                         */
188   /*    The auto-hinter module's interface.                                */
189   /*                                                                       */
190   typedef struct  FT_AutoHinter_InterfaceRec_
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_InterfaceRec, *FT_AutoHinter_Interface;
198
199
200 #ifndef FT_CONFIG_OPTION_PIC
201
202 #define FT_DEFINE_AUTOHINTER_INTERFACE(       \
203           class_,                             \
204           reset_face_,                        \
205           get_global_hints_,                  \
206           done_global_hints_,                 \
207           load_glyph_ )                       \
208   FT_CALLBACK_TABLE_DEF                       \
209   const FT_AutoHinter_InterfaceRec  class_ =  \
210   {                                           \
211     reset_face_,                              \
212     get_global_hints_,                        \
213     done_global_hints_,                       \
214     load_glyph_                               \
215   };
216
217 #else /* FT_CONFIG_OPTION_PIC */
218
219 #define FT_DEFINE_AUTOHINTER_INTERFACE(                            \
220           class_,                                                  \
221           reset_face_,                                             \
222           get_global_hints_,                                       \
223           done_global_hints_,                                      \
224           load_glyph_ )                                            \
225   void                                                             \
226   FT_Init_Class_ ## class_( FT_Library                   library,  \
227                             FT_AutoHinter_InterfaceRec*  clazz )   \
228   {                                                                \
229     FT_UNUSED( library );                                          \
230                                                                    \
231     clazz->reset_face        = reset_face_;                        \
232     clazz->get_global_hints  = get_global_hints_;                  \
233     clazz->done_global_hints = done_global_hints_;                 \
234     clazz->load_glyph        = load_glyph_;                        \
235   }
236
237 #endif /* FT_CONFIG_OPTION_PIC */
238
239 FT_END_HEADER
240
241 #endif /* __AUTOHINT_H__ */
242
243
244 /* END */