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1 /***************************************************************************/ |
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2 /* */ |
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3 /* autohint.h */ |
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4 /* */ |
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5 /* High-level `autohint' module-specific interface (specification). */ |
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6 /* */ |
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7 /* Copyright 1996-2001, 2002, 2007 by */ |
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8 /* David Turner, Robert Wilhelm, and Werner Lemberg. */ |
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9 /* */ |
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10 /* This file is part of the FreeType project, and may only be used, */ |
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11 /* modified, and distributed under the terms of the FreeType project */ |
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12 /* license, LICENSE.TXT. By continuing to use, modify, or distribute */ |
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13 /* this file you indicate that you have read the license and */ |
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14 /* understand and accept it fully. */ |
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15 /* */ |
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16 /***************************************************************************/ |
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17 |
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18 |
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19 /*************************************************************************/ |
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20 /* */ |
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21 /* The auto-hinter is used to load and automatically hint glyphs if a */ |
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22 /* format-specific hinter isn't available. */ |
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23 /* */ |
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24 /*************************************************************************/ |
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25 |
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26 |
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27 #ifndef __AUTOHINT_H__ |
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28 #define __AUTOHINT_H__ |
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29 |
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30 |
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31 /*************************************************************************/ |
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32 /* */ |
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33 /* A small technical note regarding automatic hinting in order to */ |
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34 /* clarify this module interface. */ |
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35 /* */ |
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36 /* An automatic hinter might compute two kinds of data for a given face: */ |
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37 /* */ |
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38 /* - global hints: Usually some metrics that describe global properties */ |
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39 /* of the face. It is computed by scanning more or less */ |
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40 /* aggressively the glyphs in the face, and thus can be */ |
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41 /* very slow to compute (even if the size of global */ |
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42 /* hints is really small). */ |
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43 /* */ |
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44 /* - glyph hints: These describe some important features of the glyph */ |
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45 /* outline, as well as how to align them. They are */ |
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46 /* generally much faster to compute than global hints. */ |
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47 /* */ |
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48 /* The current FreeType auto-hinter does a pretty good job while */ |
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49 /* performing fast computations for both global and glyph hints. */ |
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50 /* However, we might be interested in introducing more complex and */ |
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51 /* powerful algorithms in the future, like the one described in the John */ |
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52 /* D. Hobby paper, which unfortunately requires a lot more horsepower. */ |
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53 /* */ |
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54 /* Because a sufficiently sophisticated font management system would */ |
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55 /* typically implement an LRU cache of opened face objects to reduce */ |
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56 /* memory usage, it is a good idea to be able to avoid recomputing */ |
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57 /* global hints every time the same face is re-opened. */ |
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58 /* */ |
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59 /* We thus provide the ability to cache global hints outside of the face */ |
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60 /* object, in order to speed up font re-opening time. Of course, this */ |
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61 /* feature is purely optional, so most client programs won't even notice */ |
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62 /* it. */ |
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63 /* */ |
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64 /* I initially thought that it would be a good idea to cache the glyph */ |
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65 /* hints too. However, my general idea now is that if you really need */ |
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66 /* to cache these too, you are simply in need of a new font format, */ |
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67 /* where all this information could be stored within the font file and */ |
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68 /* decoded on the fly. */ |
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69 /* */ |
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70 /*************************************************************************/ |
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71 |
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72 |
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73 #include <ft2build.h> |
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74 #include FT_FREETYPE_H |
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75 |
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76 |
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77 FT_BEGIN_HEADER |
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78 |
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79 |
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80 typedef struct FT_AutoHinterRec_ *FT_AutoHinter; |
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81 |
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82 |
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83 /*************************************************************************/ |
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84 /* */ |
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85 /* <FuncType> */ |
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86 /* FT_AutoHinter_GlobalGetFunc */ |
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87 /* */ |
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88 /* <Description> */ |
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89 /* Retrieves the global hints computed for a given face object the */ |
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90 /* resulting data is dissociated from the face and will survive a */ |
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91 /* call to FT_Done_Face(). It must be discarded through the API */ |
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92 /* FT_AutoHinter_GlobalDoneFunc(). */ |
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93 /* */ |
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94 /* <Input> */ |
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95 /* hinter :: A handle to the source auto-hinter. */ |
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96 /* */ |
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97 /* face :: A handle to the source face object. */ |
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98 /* */ |
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99 /* <Output> */ |
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100 /* global_hints :: A typeless pointer to the global hints. */ |
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101 /* */ |
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102 /* global_len :: The size in bytes of the global hints. */ |
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103 /* */ |
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104 typedef void |
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105 (*FT_AutoHinter_GlobalGetFunc)( FT_AutoHinter hinter, |
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106 FT_Face face, |
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107 void** global_hints, |
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108 long* global_len ); |
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109 |
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110 |
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111 /*************************************************************************/ |
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112 /* */ |
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113 /* <FuncType> */ |
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114 /* FT_AutoHinter_GlobalDoneFunc */ |
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115 /* */ |
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116 /* <Description> */ |
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117 /* Discards the global hints retrieved through */ |
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118 /* FT_AutoHinter_GlobalGetFunc(). This is the only way these hints */ |
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119 /* are freed from memory. */ |
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120 /* */ |
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121 /* <Input> */ |
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122 /* hinter :: A handle to the auto-hinter module. */ |
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123 /* */ |
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124 /* global :: A pointer to retrieved global hints to discard. */ |
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125 /* */ |
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126 typedef void |
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127 (*FT_AutoHinter_GlobalDoneFunc)( FT_AutoHinter hinter, |
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128 void* global ); |
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129 |
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130 |
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131 /*************************************************************************/ |
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132 /* */ |
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133 /* <FuncType> */ |
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134 /* FT_AutoHinter_GlobalResetFunc */ |
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135 /* */ |
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136 /* <Description> */ |
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137 /* This function is used to recompute the global metrics in a given */ |
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138 /* font. This is useful when global font data changes (e.g. Multiple */ |
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139 /* Masters fonts where blend coordinates change). */ |
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140 /* */ |
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141 /* <Input> */ |
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142 /* hinter :: A handle to the source auto-hinter. */ |
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143 /* */ |
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144 /* face :: A handle to the face. */ |
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145 /* */ |
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146 typedef void |
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147 (*FT_AutoHinter_GlobalResetFunc)( FT_AutoHinter hinter, |
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148 FT_Face face ); |
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149 |
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150 |
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151 /*************************************************************************/ |
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152 /* */ |
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153 /* <FuncType> */ |
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154 /* FT_AutoHinter_GlyphLoadFunc */ |
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155 /* */ |
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156 /* <Description> */ |
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157 /* This function is used to load, scale, and automatically hint a */ |
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158 /* glyph from a given face. */ |
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159 /* */ |
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160 /* <Input> */ |
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161 /* face :: A handle to the face. */ |
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162 /* */ |
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163 /* glyph_index :: The glyph index. */ |
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164 /* */ |
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165 /* load_flags :: The load flags. */ |
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166 /* */ |
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167 /* <Note> */ |
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168 /* This function is capable of loading composite glyphs by hinting */ |
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169 /* each sub-glyph independently (which improves quality). */ |
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170 /* */ |
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171 /* It will call the font driver with FT_Load_Glyph(), with */ |
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172 /* FT_LOAD_NO_SCALE set. */ |
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173 /* */ |
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174 typedef FT_Error |
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175 (*FT_AutoHinter_GlyphLoadFunc)( FT_AutoHinter hinter, |
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176 FT_GlyphSlot slot, |
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177 FT_Size size, |
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178 FT_UInt glyph_index, |
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179 FT_Int32 load_flags ); |
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180 |
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181 |
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182 /*************************************************************************/ |
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183 /* */ |
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184 /* <Struct> */ |
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185 /* FT_AutoHinter_ServiceRec */ |
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186 /* */ |
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187 /* <Description> */ |
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188 /* The auto-hinter module's interface. */ |
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189 /* */ |
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190 typedef struct FT_AutoHinter_ServiceRec_ |
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191 { |
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192 FT_AutoHinter_GlobalResetFunc reset_face; |
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193 FT_AutoHinter_GlobalGetFunc get_global_hints; |
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194 FT_AutoHinter_GlobalDoneFunc done_global_hints; |
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195 FT_AutoHinter_GlyphLoadFunc load_glyph; |
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196 |
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197 } FT_AutoHinter_ServiceRec, *FT_AutoHinter_Service; |
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198 |
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199 #ifndef FT_CONFIG_OPTION_PIC |
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200 |
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201 #define FT_DEFINE_AUTOHINTER_SERVICE(class_, reset_face_, get_global_hints_, \ |
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202 done_global_hints_, load_glyph_) \ |
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203 FT_CALLBACK_TABLE_DEF \ |
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204 const FT_AutoHinter_ServiceRec class_ = \ |
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205 { \ |
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206 reset_face_, get_global_hints_, done_global_hints_, load_glyph_ \ |
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207 }; |
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208 |
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209 #else /* FT_CONFIG_OPTION_PIC */ |
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210 |
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211 #define FT_DEFINE_AUTOHINTER_SERVICE(class_, reset_face_, get_global_hints_, \ |
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212 done_global_hints_, load_glyph_) \ |
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213 void \ |
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214 FT_Init_Class_##class_( FT_Library library, \ |
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215 FT_AutoHinter_ServiceRec* clazz) \ |
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216 { \ |
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217 FT_UNUSED(library); \ |
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218 clazz->reset_face = reset_face_; \ |
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219 clazz->get_global_hints = get_global_hints_; \ |
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220 clazz->done_global_hints = done_global_hints_; \ |
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221 clazz->load_glyph = load_glyph_; \ |
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222 } |
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223 |
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224 #endif /* FT_CONFIG_OPTION_PIC */ |
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225 |
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226 FT_END_HEADER |
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227 |
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228 #endif /* __AUTOHINT_H__ */ |
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229 |
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230 |
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231 /* END */ |