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- /***************************************************************************/
- /* */
- /* ftttdrv.h */
- /* */
- /* FreeType API for controlling the TrueType driver */
- /* (specification only). */
- /* */
- /* Copyright 2013 by */
- /* David Turner, Robert Wilhelm, and Werner Lemberg. */
- /* */
- /* This file is part of the FreeType project, and may only be used, */
- /* modified, and distributed under the terms of the FreeType project */
- /* license, LICENSE.TXT. By continuing to use, modify, or distribute */
- /* this file you indicate that you have read the license and */
- /* understand and accept it fully. */
- /* */
- /***************************************************************************/
- #ifndef __FTTTDRV_H__
- #define __FTTTDRV_H__
- #include <ft2build.h>
- #include FT_FREETYPE_H
- #ifdef FREETYPE_H
- #error "freetype.h of FreeType 1 has been loaded!"
- #error "Please fix the directory search order for header files"
- #error "so that freetype.h of FreeType 2 is found first."
- #endif
- FT_BEGIN_HEADER
- /**************************************************************************
- *
- * @section:
- * tt_driver
- *
- * @title:
- * The TrueType driver
- *
- * @abstract:
- * Controlling the TrueType driver module.
- *
- * @description:
- * While FreeType's TrueType driver doesn't expose API functions by
- * itself, it is possible to control its behaviour with @FT_Property_Set
- * and @FT_Property_Get. The following lists the available properties
- * together with the necessary macros and structures.
- *
- * The TrueType driver's module name is `truetype'.
- *
- */
- /**************************************************************************
- *
- * @property:
- * interpreter-version
- *
- * @description:
- * Currently, two versions are available, representing the bytecode
- * interpreter with and without subpixel hinting support,
- * respectively. The default is subpixel support if
- * TT_CONFIG_OPTION_SUBPIXEL_HINTING is defined, and no subpixel
- * support otherwise (since it isn't available then).
- *
- * If subpixel hinting is on, many TrueType bytecode instructions
- * behave differently compared to B/W or grayscale rendering. The
- * main idea is to render at a much increased horizontal resolution,
- * then sampling down the created output to subpixel precision.
- * However, many older fonts are not suited to this and must be
- * specially taken care of by applying (hardcoded) font-specific
- * tweaks.
- *
- * Details on subpixel hinting and some of the necessary tweaks can be
- * found in Greg Hitchcock's whitepaper at
- * `http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx'.
- *
- * The following example code demonstrates how to activate subpixel
- * hinting (omitting the error handling).
- *
- * {
- * FT_Library library;
- * FT_Face face;
- * FT_UInt interpreter_version = TT_INTERPRETER_VERSION_38;
- *
- *
- * FT_Init_FreeType( &library );
- *
- * FT_Property_Set( library, "truetype",
- * "interpreter-version",
- * &interpreter_version );
- * }
- *
- * @note:
- * This property can be used with @FT_Property_Get also.
- *
- */
- /**************************************************************************
- *
- * @enum:
- * TT_INTERPRETER_VERSION_XXX
- *
- * @description:
- * A list of constants used for the @interpreter-version property to
- * select the hinting engine for Truetype fonts.
- *
- * The numeric value in the constant names represents the version
- * number as returned by the `GETINFO' bytecode instruction.
- *
- * @values:
- * TT_INTERPRETER_VERSION_35 ::
- * Version~35 corresponds to MS rasterizer v.1.7 as used e.g. in
- * Windows~98; only grayscale and B/W rasterizing is supported.
- *
- * TT_INTERPRETER_VERSION_38 ::
- * Version~38 corresponds to MS rasterizer v.1.9; it is roughly
- * equivalent to the hinting provided by DirectWrite ClearType (as
- * can be found, for example, in the Internet Explorer~9 running on
- * Windows~7).
- *
- * @note:
- * This property controls the behaviour of the bytecode interpreter
- * and thus how outlines get hinted. It does *not* control how glyph
- * get rasterized! In particular, it does not control subpixel color
- * filtering.
- *
- * If FreeType has not been compiled with configuration option
- * FT_CONFIG_OPTION_SUBPIXEL_HINTING, selecting version~38 causes an
- * `FT_Err_Unimplemented_Feature' error.
- *
- * Depending on the graphics framework, Microsoft uses different
- * bytecode engines. As a consequence, the version numbers returned by
- * a call to the `GETINFO[1]' bytecode instruction are more convoluted
- * than desired.
- *
- * {
- * framework Windows version result of GETINFO[1]
- * ----------------------------------------------------
- * GDI before XP 35
- * GDI XP and later 37
- * GDI+ old before Vista 37
- * GDI+ old Vista, 7 38
- * GDI+ after 7 40
- * DWrite before 8 39
- * DWrite 8 and later 40
- * }
- *
- * Since FreeType doesn't provide all capabilities of DWrite ClearType,
- * using version~38 seems justified.
- *
- */
- #define TT_INTERPRETER_VERSION_35 35
- #define TT_INTERPRETER_VERSION_38 38
- /* */
- FT_END_HEADER
- #endif /* __FTTTDRV_H__ */
- /* END */
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