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| 1 /***************************************************************************/ | |
| 2 /* */ | |
| 3 /* ftttdrv.h */ | |
| 4 /* */ | |
| 5 /* FreeType API for controlling the TrueType driver */ | |
| 6 /* (specification only). */ | |
| 7 /* */ | |
| 8 /* Copyright 2013 by */ | |
| 9 /* David Turner, Robert Wilhelm, and Werner Lemberg. */ | |
| 10 /* */ | |
| 11 /* This file is part of the FreeType project, and may only be used, */ | |
| 12 /* modified, and distributed under the terms of the FreeType project */ | |
| 13 /* license, LICENSE.TXT. By continuing to use, modify, or distribute */ | |
| 14 /* this file you indicate that you have read the license and */ | |
| 15 /* understand and accept it fully. */ | |
| 16 /* */ | |
| 17 /***************************************************************************/ | |
| 18 | |
| 19 | |
| 20 #ifndef __FTTTDRV_H__ | |
| 21 #define __FTTTDRV_H__ | |
| 22 | |
| 23 #include <ft2build.h> | |
| 24 #include FT_FREETYPE_H | |
| 25 | |
| 26 #ifdef FREETYPE_H | |
| 27 #error "freetype.h of FreeType 1 has been loaded!" | |
| 28 #error "Please fix the directory search order for header files" | |
| 29 #error "so that freetype.h of FreeType 2 is found first." | |
| 30 #endif | |
| 31 | |
| 32 | |
| 33 FT_BEGIN_HEADER | |
| 34 | |
| 35 | |
| 36 /************************************************************************** | |
| 37 * | |
| 38 * @section: | |
| 39 * tt_driver | |
| 40 * | |
| 41 * @title: | |
| 42 * The TrueType driver | |
| 43 * | |
| 44 * @abstract: | |
| 45 * Controlling the TrueType driver module. | |
| 46 * | |
| 47 * @description: | |
| 48 * While FreeType's TrueType driver doesn't expose API functions by | |
| 49 * itself, it is possible to control its behaviour with @FT_Property_Set | |
| 50 * and @FT_Property_Get. The following lists the available properties | |
| 51 * together with the necessary macros and structures. | |
| 52 * | |
| 53 * The TrueType driver's module name is `truetype'. | |
| 54 * | |
| 55 */ | |
| 56 | |
| 57 | |
| 58 /************************************************************************** | |
| 59 * | |
| 60 * @property: | |
| 61 * interpreter-version | |
| 62 * | |
| 63 * @description: | |
| 64 * Currently, two versions are available, representing the bytecode | |
| 65 * interpreter with and without subpixel hinting support, | |
| 66 * respectively. The default is subpixel support if | |
| 67 * TT_CONFIG_OPTION_SUBPIXEL_HINTING is defined, and no subpixel | |
| 68 * support otherwise (since it isn't available then). | |
| 69 * | |
| 70 * If subpixel hinting is on, many TrueType bytecode instructions | |
| 71 * behave differently compared to B/W or grayscale rendering. The | |
| 72 * main idea is to render at a much increased horizontal resolution, | |
| 73 * then sampling down the created output to subpixel precision. | |
| 74 * However, many older fonts are not suited to this and must be | |
| 75 * specially taken care of by applying (hardcoded) font-specific | |
| 76 * tweaks. | |
| 77 * | |
| 78 * Details on subpixel hinting and some of the necessary tweaks can be | |
| 79 * found in Greg Hitchcock's whitepaper at | |
| 80 * `http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx'. | |
| 81 * | |
| 82 * The following example code demonstrates how to activate subpixel | |
| 83 * hinting (omitting the error handling). | |
| 84 * | |
| 85 * { | |
| 86 * FT_Library library; | |
| 87 * FT_Face face; | |
| 88 * FT_UInt interpreter_version = TT_INTERPRETER_VERSION_38; | |
| 89 * | |
| 90 * | |
| 91 * FT_Init_FreeType( &library ); | |
| 92 * | |
| 93 * FT_Property_Set( library, "truetype", | |
| 94 * "interpreter-version", | |
| 95 * &interpreter_version ); | |
| 96 * } | |
| 97 * | |
| 98 * @note: | |
| 99 * This property can be used with @FT_Property_Get also. | |
| 100 * | |
| 101 */ | |
| 102 | |
| 103 | |
| 104 /************************************************************************** | |
| 105 * | |
| 106 * @enum: | |
| 107 * TT_INTERPRETER_VERSION_XXX | |
| 108 * | |
| 109 * @description: | |
| 110 * A list of constants used for the @interpreter-version property to | |
| 111 * select the hinting engine for Truetype fonts. | |
| 112 * | |
| 113 * The numeric value in the constant names represents the version | |
| 114 * number as returned by the `GETINFO' bytecode instruction. | |
| 115 * | |
| 116 * @values: | |
| 117 * TT_INTERPRETER_VERSION_35 :: | |
| 118 * Version~35 corresponds to MS rasterizer v.1.7 as used e.g. in | |
| 119 * Windows~98; only grayscale and B/W rasterizing is supported. | |
| 120 * | |
| 121 * TT_INTERPRETER_VERSION_38 :: | |
| 122 * Version~38 corresponds to MS rasterizer v.1.9; it is roughly | |
| 123 * equivalent to the hinting provided by DirectWrite ClearType (as | |
| 124 * can be found, for example, in the Internet Explorer~9 running on | |
| 125 * Windows~7). | |
| 126 * | |
| 127 * @note: | |
| 128 * This property controls the behaviour of the bytecode interpreter | |
| 129 * and thus how outlines get hinted. It does *not* control how glyph | |
| 130 * get rasterized! In particular, it does not control subpixel color | |
| 131 * filtering. | |
| 132 * | |
| 133 * If FreeType has not been compiled with configuration option | |
| 134 * FT_CONFIG_OPTION_SUBPIXEL_HINTING, selecting version~38 causes an | |
| 135 * `FT_Err_Unimplemented_Feature' error. | |
| 136 * | |
| 137 * Depending on the graphics framework, Microsoft uses different | |
| 138 * bytecode engines. As a consequence, the version numbers returned by | |
| 139 * a call to the `GETINFO[1]' bytecode instruction are more convoluted | |
| 140 * than desired. | |
| 141 * | |
| 142 * { | |
| 143 * framework Windows version result of GETINFO[1] | |
| 144 * ---------------------------------------------------- | |
| 145 * GDI before XP 35 | |
| 146 * GDI XP and later 37 | |
| 147 * GDI+ old before Vista 37 | |
| 148 * GDI+ old Vista, 7 38 | |
| 149 * GDI+ after 7 40 | |
| 150 * DWrite before 8 39 | |
| 151 * DWrite 8 and later 40 | |
| 152 * } | |
| 153 * | |
| 154 * Since FreeType doesn't provide all capabilities of DWrite ClearType, | |
| 155 * using version~38 seems justified. | |
| 156 * | |
| 157 */ | |
| 158 #define TT_INTERPRETER_VERSION_35 35 | |
| 159 #define TT_INTERPRETER_VERSION_38 38 | |
| 160 | |
| 161 /* */ | |
| 162 | |
| 163 | |
| 164 FT_END_HEADER | |
| 165 | |
| 166 | |
| 167 #endif /* __FTTTDRV_H__ */ | |
| 168 | |
| 169 | |
| 170 /* END */ | |
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Chromium Code Reviews
Issue 1413673003:
Update bundled freetype to 2.6.1 (Closed)
Base URL: https://pdfium.googlesource.com/pdfium.git@master