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 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 | /* agressively 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 |
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200 | FT_END_HEADER
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201 |
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202 | #endif /* __AUTOHINT_H__ */
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203 |
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204 |
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205 | /* END */
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