1 /***************************************************************************/ 2 /* */ 3 /* autohint.h */ 4 /* */ 5 /* High-level `autohint' module-specific interface (specification). */ 6 /* */ 7 /* Copyright 1996-2018 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 /* 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 */ 245
