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autohint.h
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00001 /***************************************************************************/ 00002 /* */ 00003 /* autohint.h */ 00004 /* */ 00005 /* High-level `autohint' module-specific interface (specification). */ 00006 /* */ 00007 /* Copyright 1996-2001, 2002, 2007 by */ 00008 /* David Turner, Robert Wilhelm, and Werner Lemberg. */ 00009 /* */ 00010 /* This file is part of the FreeType project, and may only be used, */ 00011 /* modified, and distributed under the terms of the FreeType project */ 00012 /* license, LICENSE.TXT. By continuing to use, modify, or distribute */ 00013 /* this file you indicate that you have read the license and */ 00014 /* understand and accept it fully. */ 00015 /* */ 00016 /***************************************************************************/ 00017 00018 00019 /*************************************************************************/ 00020 /* */ 00021 /* The auto-hinter is used to load and automatically hint glyphs if a */ 00022 /* format-specific hinter isn't available. */ 00023 /* */ 00024 /*************************************************************************/ 00025 00026 00027 #ifndef __AUTOHINT_H__ 00028 #define __AUTOHINT_H__ 00029 00030 00031 /*************************************************************************/ 00032 /* */ 00033 /* A small technical note regarding automatic hinting in order to */ 00034 /* clarify this module interface. */ 00035 /* */ 00036 /* An automatic hinter might compute two kinds of data for a given face: */ 00037 /* */ 00038 /* - global hints: Usually some metrics that describe global properties */ 00039 /* of the face. It is computed by scanning more or less */ 00040 /* aggressively the glyphs in the face, and thus can be */ 00041 /* very slow to compute (even if the size of global */ 00042 /* hints is really small). */ 00043 /* */ 00044 /* - glyph hints: These describe some important features of the glyph */ 00045 /* outline, as well as how to align them. They are */ 00046 /* generally much faster to compute than global hints. */ 00047 /* */ 00048 /* The current FreeType auto-hinter does a pretty good job while */ 00049 /* performing fast computations for both global and glyph hints. */ 00050 /* However, we might be interested in introducing more complex and */ 00051 /* powerful algorithms in the future, like the one described in the John */ 00052 /* D. Hobby paper, which unfortunately requires a lot more horsepower. */ 00053 /* */ 00054 /* Because a sufficiently sophisticated font management system would */ 00055 /* typically implement an LRU cache of opened face objects to reduce */ 00056 /* memory usage, it is a good idea to be able to avoid recomputing */ 00057 /* global hints every time the same face is re-opened. */ 00058 /* */ 00059 /* We thus provide the ability to cache global hints outside of the face */ 00060 /* object, in order to speed up font re-opening time. Of course, this */ 00061 /* feature is purely optional, so most client programs won't even notice */ 00062 /* it. */ 00063 /* */ 00064 /* I initially thought that it would be a good idea to cache the glyph */ 00065 /* hints too. However, my general idea now is that if you really need */ 00066 /* to cache these too, you are simply in need of a new font format, */ 00067 /* where all this information could be stored within the font file and */ 00068 /* decoded on the fly. */ 00069 /* */ 00070 /*************************************************************************/ 00071 00072 00073 #include <ft2build.h> 00074 #include FT_FREETYPE_H 00075 00076 00077 FT_BEGIN_HEADER 00078 00079 00080 typedef struct FT_AutoHinterRec_ *FT_AutoHinter; 00081 00082 00083 /*************************************************************************/ 00084 /* */ 00085 /* <FuncType> */ 00086 /* FT_AutoHinter_GlobalGetFunc */ 00087 /* */ 00088 /* <Description> */ 00089 /* Retrieves the global hints computed for a given face object the */ 00090 /* resulting data is dissociated from the face and will survive a */ 00091 /* call to FT_Done_Face(). It must be discarded through the API */ 00092 /* FT_AutoHinter_GlobalDoneFunc(). */ 00093 /* */ 00094 /* <Input> */ 00095 /* hinter :: A handle to the source auto-hinter. */ 00096 /* */ 00097 /* face :: A handle to the source face object. */ 00098 /* */ 00099 /* <Output> */ 00100 /* global_hints :: A typeless pointer to the global hints. */ 00101 /* */ 00102 /* global_len :: The size in bytes of the global hints. */ 00103 /* */ 00104 typedef void 00105 (*FT_AutoHinter_GlobalGetFunc)( FT_AutoHinter hinter, 00106 FT_Face face, 00107 void** global_hints, 00108 long* global_len ); 00109 00110 00111 /*************************************************************************/ 00112 /* */ 00113 /* <FuncType> */ 00114 /* FT_AutoHinter_GlobalDoneFunc */ 00115 /* */ 00116 /* <Description> */ 00117 /* Discards the global hints retrieved through */ 00118 /* FT_AutoHinter_GlobalGetFunc(). This is the only way these hints */ 00119 /* are freed from memory. */ 00120 /* */ 00121 /* <Input> */ 00122 /* hinter :: A handle to the auto-hinter module. */ 00123 /* */ 00124 /* global :: A pointer to retrieved global hints to discard. */ 00125 /* */ 00126 typedef void 00127 (*FT_AutoHinter_GlobalDoneFunc)( FT_AutoHinter hinter, 00128 void* global ); 00129 00130 00131 /*************************************************************************/ 00132 /* */ 00133 /* <FuncType> */ 00134 /* FT_AutoHinter_GlobalResetFunc */ 00135 /* */ 00136 /* <Description> */ 00137 /* This function is used to recompute the global metrics in a given */ 00138 /* font. This is useful when global font data changes (e.g. Multiple */ 00139 /* Masters fonts where blend coordinates change). */ 00140 /* */ 00141 /* <Input> */ 00142 /* hinter :: A handle to the source auto-hinter. */ 00143 /* */ 00144 /* face :: A handle to the face. */ 00145 /* */ 00146 typedef void 00147 (*FT_AutoHinter_GlobalResetFunc)( FT_AutoHinter hinter, 00148 FT_Face face ); 00149 00150 00151 /*************************************************************************/ 00152 /* */ 00153 /* <FuncType> */ 00154 /* FT_AutoHinter_GlyphLoadFunc */ 00155 /* */ 00156 /* <Description> */ 00157 /* This function is used to load, scale, and automatically hint a */ 00158 /* glyph from a given face. */ 00159 /* */ 00160 /* <Input> */ 00161 /* face :: A handle to the face. */ 00162 /* */ 00163 /* glyph_index :: The glyph index. */ 00164 /* */ 00165 /* load_flags :: The load flags. */ 00166 /* */ 00167 /* <Note> */ 00168 /* This function is capable of loading composite glyphs by hinting */ 00169 /* each sub-glyph independently (which improves quality). */ 00170 /* */ 00171 /* It will call the font driver with FT_Load_Glyph(), with */ 00172 /* FT_LOAD_NO_SCALE set. */ 00173 /* */ 00174 typedef FT_Error 00175 (*FT_AutoHinter_GlyphLoadFunc)( FT_AutoHinter hinter, 00176 FT_GlyphSlot slot, 00177 FT_Size size, 00178 FT_UInt glyph_index, 00179 FT_Int32 load_flags ); 00180 00181 00182 /*************************************************************************/ 00183 /* */ 00184 /* <Struct> */ 00185 /* FT_AutoHinter_ServiceRec */ 00186 /* */ 00187 /* <Description> */ 00188 /* The auto-hinter module's interface. */ 00189 /* */ 00190 typedef struct FT_AutoHinter_ServiceRec_ 00191 { 00192 FT_AutoHinter_GlobalResetFunc reset_face; 00193 FT_AutoHinter_GlobalGetFunc get_global_hints; 00194 FT_AutoHinter_GlobalDoneFunc done_global_hints; 00195 FT_AutoHinter_GlyphLoadFunc load_glyph; 00196 00197 } FT_AutoHinter_ServiceRec, *FT_AutoHinter_Service; 00198 00199 #ifndef FT_CONFIG_OPTION_PIC 00200 00201 #define FT_DEFINE_AUTOHINTER_SERVICE(class_, reset_face_, get_global_hints_, \ 00202 done_global_hints_, load_glyph_) \ 00203 FT_CALLBACK_TABLE_DEF \ 00204 const FT_AutoHinter_ServiceRec class_ = \ 00205 { \ 00206 reset_face_, get_global_hints_, done_global_hints_, load_glyph_ \ 00207 }; 00208 00209 #else /* FT_CONFIG_OPTION_PIC */ 00210 00211 #define FT_DEFINE_AUTOHINTER_SERVICE(class_, reset_face_, get_global_hints_, \ 00212 done_global_hints_, load_glyph_) \ 00213 void \ 00214 FT_Init_Class_##class_( FT_Library library, \ 00215 FT_AutoHinter_ServiceRec* clazz) \ 00216 { \ 00217 FT_UNUSED(library); \ 00218 clazz->reset_face = reset_face_; \ 00219 clazz->get_global_hints = get_global_hints_; \ 00220 clazz->done_global_hints = done_global_hints_; \ 00221 clazz->load_glyph = load_glyph_; \ 00222 } 00223 00224 #endif /* FT_CONFIG_OPTION_PIC */ 00225 00226 FT_END_HEADER 00227 00228 #endif /* __AUTOHINT_H__ */ 00229 00230 00231 /* END */
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