Editing: ftdriver.h
/***************************************************************************/ /* */ /* ftdriver.h */ /* */ /* FreeType API for controlling driver modules (specification only). */ /* */ /* Copyright 2017-2018 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 FTDRIVER_H_ #define FTDRIVER_H_ #include <ft2build.h> #include FT_FREETYPE_H #include FT_PARAMETER_TAGS_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: * auto_hinter * * @title: * The auto-hinter * * @abstract: * Controlling the auto-hinting module. * * @description: * While FreeType's auto-hinter 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. * * Note that the auto-hinter's module name is `autofitter' for * historical reasons. * * Available properties are @increase-x-height, @no-stem-darkening * (experimental), @darkening-parameters (experimental), @warping * (experimental), @glyph-to-script-map (experimental), @fallback-script * (experimental), and @default-script (experimental), as documented in * the @properties section. * */ /************************************************************************** * * @section: * cff_driver * * @title: * The CFF driver * * @abstract: * Controlling the CFF driver module. * * @description: * While FreeType's CFF driver doesn't expose API functions by itself, * it is possible to control its behaviour with @FT_Property_Set and * @FT_Property_Get. * * The CFF driver's module name is `cff'. * * Available properties are @hinting-engine, @no-stem-darkening, * @darkening-parameters, and @random-seed, as documented in the * @properties section. * * * *Hinting* *and* *antialiasing* *principles* *of* *the* *new* *engine* * * The rasterizer is positioning horizontal features (e.g., ascender * height & x-height, or crossbars) on the pixel grid and minimizing the * amount of antialiasing applied to them, while placing vertical * features (vertical stems) on the pixel grid without hinting, thus * representing the stem position and weight accurately. Sometimes the * vertical stems may be only partially black. In this context, * `antialiasing' means that stems are not positioned exactly on pixel * borders, causing a fuzzy appearance. * * There are two principles behind this approach. * * 1) No hinting in the horizontal direction: Unlike `superhinted' * TrueType, which changes glyph widths to accommodate regular * inter-glyph spacing, Adobe's approach is `faithful to the design' in * representing both the glyph width and the inter-glyph spacing * designed for the font. This makes the screen display as close as it * can be to the result one would get with infinite resolution, while * preserving what is considered the key characteristics of each glyph. * Note that the distances between unhinted and grid-fitted positions at * small sizes are comparable to kerning values and thus would be * noticeable (and distracting) while reading if hinting were applied. * * One of the reasons to not hint horizontally is antialiasing for LCD * screens: The pixel geometry of modern displays supplies three * vertical subpixels as the eye moves horizontally across each visible * pixel. On devices where we can be certain this characteristic is * present a rasterizer can take advantage of the subpixels to add * increments of weight. In Western writing systems this turns out to * be the more critical direction anyway; the weights and spacing of * vertical stems (see above) are central to Armenian, Cyrillic, Greek, * and Latin type designs. Even when the rasterizer uses greyscale * antialiasing instead of color (a necessary compromise when one * doesn't know the screen characteristics), the unhinted vertical * features preserve the design's weight and spacing much better than * aliased type would. * * 2) Alignment in the vertical direction: Weights and spacing along the * y~axis are less critical; what is much more important is the visual * alignment of related features (like cap-height and x-height). The * sense of alignment for these is enhanced by the sharpness of grid-fit * edges, while the cruder vertical resolution (full pixels instead of * 1/3 pixels) is less of a problem. * * On the technical side, horizontal alignment zones for ascender, * x-height, and other important height values (traditionally called * `blue zones') as defined in the font are positioned independently, * each being rounded to the nearest pixel edge, taking care of * overshoot suppression at small sizes, stem darkening, and scaling. * * Hstems (this is, hint values defined in the font to help align * horizontal features) that fall within a blue zone are said to be * `captured' and are aligned to that zone. Uncaptured stems are moved * in one of four ways, top edge up or down, bottom edge up or down. * Unless there are conflicting hstems, the smallest movement is taken * to minimize distortion. * */ /************************************************************************** * * @section: * pcf_driver * * @title: * The PCF driver * * @abstract: * Controlling the PCF driver module. * * @description: * While FreeType's PCF driver doesn't expose API functions by itself, * it is possible to control its behaviour with @FT_Property_Set and * @FT_Property_Get. Right now, there is a single property * @no-long-family-names available if FreeType is compiled with * PCF_CONFIG_OPTION_LONG_FAMILY_NAMES. * * The PCF driver's module name is `pcf'. * */ /************************************************************************** * * @section: * t1_cid_driver * * @title: * The Type 1 and CID drivers * * @abstract: * Controlling the Type~1 and CID driver modules. * * @description: * It is possible to control the behaviour of FreeType's Type~1 and * Type~1 CID drivers with @FT_Property_Set and @FT_Property_Get. * * Behind the scenes, both drivers use the Adobe CFF engine for hinting; * however, the used properties must be specified separately. * * The Type~1 driver's module name is `type1'; the CID driver's module * name is `t1cid'. * * Available properties are @hinting-engine, @no-stem-darkening, * @darkening-parameters, and @random-seed, as documented in the * @properties section. * * Please see the @cff_driver section for more details on the new * hinting engine. * */ /************************************************************************** * * @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'. * * A single property @interpreter-version is available, as documented in * the @properties section. * * We start with a list of definitions, kindly provided by Greg * Hitchcock. * * _Bi-Level_ _Rendering_ * * Monochromatic rendering, exclusively used in the early days of * TrueType by both Apple and Microsoft. Microsoft's GDI interface * supported hinting of the right-side bearing point, such that the * advance width could be non-linear. Most often this was done to * achieve some level of glyph symmetry. To enable reasonable * performance (e.g., not having to run hinting on all glyphs just to * get the widths) there was a bit in the head table indicating if the * side bearing was hinted, and additional tables, `hdmx' and `LTSH', to * cache hinting widths across multiple sizes and device aspect ratios. * * _Font_ _Smoothing_ * * Microsoft's GDI implementation of anti-aliasing. Not traditional * anti-aliasing as the outlines were hinted before the sampling. The * widths matched the bi-level rendering. * * _ClearType_ _Rendering_ * * Technique that uses physical subpixels to improve rendering on LCD * (and other) displays. Because of the higher resolution, many methods * of improving symmetry in glyphs through hinting the right-side * bearing were no longer necessary. This lead to what GDI calls * `natural widths' ClearType, see * http://www.beatstamm.com/typography/RTRCh4.htm#Sec21. Since hinting * has extra resolution, most non-linearity went away, but it is still * possible for hints to change the advance widths in this mode. * * _ClearType_ _Compatible_ _Widths_ * * One of the earliest challenges with ClearType was allowing the * implementation in GDI to be selected without requiring all UI and * documents to reflow. To address this, a compatible method of * rendering ClearType was added where the font hints are executed once * to determine the width in bi-level rendering, and then re-run in * ClearType, with the difference in widths being absorbed in the font * hints for ClearType (mostly in the white space of hints); see * http://www.beatstamm.com/typography/RTRCh4.htm#Sec20. Somewhat by * definition, compatible width ClearType allows for non-linear widths, * but only when the bi-level version has non-linear widths. * * _ClearType_ _Subpixel_ _Positioning_ * * One of the nice benefits of ClearType is the ability to more crisply * display fractional widths; unfortunately, the GDI model of integer * bitmaps did not support this. However, the WPF and Direct Write * frameworks do support fractional widths. DWrite calls this `natural * mode', not to be confused with GDI's `natural widths'. Subpixel * positioning, in the current implementation of Direct Write, * unfortunately does not support hinted advance widths, see * http://www.beatstamm.com/typography/RTRCh4.htm#Sec22. Note that the * TrueType interpreter fully allows the advance width to be adjusted in * this mode, just the DWrite client will ignore those changes. * * _ClearType_ _Backward_ _Compatibility_ * * This is a set of exceptions made in the TrueType interpreter to * minimize hinting techniques that were problematic with the extra * resolution of ClearType; see * http://www.beatstamm.com/typography/RTRCh4.htm#Sec1 and * https://www.microsoft.com/typography/cleartype/truetypecleartype.aspx. * This technique is not to be confused with ClearType compatible * widths. ClearType backward compatibility has no direct impact on * changing advance widths, but there might be an indirect impact on * disabling some deltas. This could be worked around in backward * compatibility mode. * * _Native_ _ClearType_ _Mode_ * * (Not to be confused with `natural widths'.) This mode removes all * the exceptions in the TrueType interpreter when running with * ClearType. Any issues on widths would still apply, though. * */ /************************************************************************** * * @section: * properties * * @title: * Driver properties * * @abstract: * Controlling driver modules. * * @description: * Driver modules can be controlled by setting and unsetting properties, * using the functions @FT_Property_Set and @FT_Property_Get. This * section documents the available properties, together with auxiliary * macros and structures. * */ /************************************************************************** * * @enum: * FT_HINTING_XXX * * @description: * A list of constants used for the @hinting-engine property to * select the hinting engine for CFF, Type~1, and CID fonts. * * @values: * FT_HINTING_FREETYPE :: * Use the old FreeType hinting engine. * * FT_HINTING_ADOBE :: * Use the hinting engine contributed by Adobe. * * @since: * 2.9 * */ #define FT_HINTING_FREETYPE 0 #define FT_HINTING_ADOBE 1 /* these constants (introduced in 2.4.12) are deprecated */ #define FT_CFF_HINTING_FREETYPE FT_HINTING_FREETYPE #define FT_CFF_HINTING_ADOBE FT_HINTING_ADOBE /************************************************************************** * * @property: * hinting-engine * * @description: * Thanks to Adobe, which contributed a new hinting (and parsing) * engine, an application can select between `freetype' and `adobe' if * compiled with CFF_CONFIG_OPTION_OLD_ENGINE. If this configuration * macro isn't defined, `hinting-engine' does nothing. * * The same holds for the Type~1 and CID modules if compiled with * T1_CONFIG_OPTION_OLD_ENGINE. * * For the `cff' module, the default engine is `freetype' if * CFF_CONFIG_OPTION_OLD_ENGINE is defined, and `adobe' otherwise. * * For both the `type1' and `t1cid' modules, the default engine is * `freetype' if T1_CONFIG_OPTION_OLD_ENGINE is defined, and `adobe' * otherwise. * * The following example code demonstrates how to select Adobe's hinting * engine for the `cff' module (omitting the error handling). * * { * FT_Library library; * FT_UInt hinting_engine = FT_CFF_HINTING_ADOBE; * * * FT_Init_FreeType( &library ); * * FT_Property_Set( library, "cff", * "hinting-engine", &hinting_engine ); * } * * @note: * This property can be used with @FT_Property_Get also. * * This property can be set via the `FREETYPE_PROPERTIES' environment * variable (using values `adobe' or `freetype'). * * @since: * 2.4.12 (for `cff' module) * * 2.9 (for `type1' and `t1cid' modules) * */ /************************************************************************** * * @property: * no-stem-darkening * * @description: * All glyphs that pass through the auto-hinter will be emboldened * unless this property is set to TRUE. The same is true for the CFF, * Type~1, and CID font modules if the `Adobe' engine is selected (which * is the default). * * Stem darkening emboldens glyphs at smaller sizes to make them more * readable on common low-DPI screens when using linear alpha blending * and gamma correction, see @FT_Render_Glyph. When not using linear * alpha blending and gamma correction, glyphs will appear heavy and * fuzzy! * * Gamma correction essentially lightens fonts since shades of grey are * shifted to higher pixel values (=~higher brightness) to match the * original intention to the reality of our screens. The side-effect is * that glyphs `thin out'. Mac OS~X and Adobe's proprietary font * rendering library implement a counter-measure: stem darkening at * smaller sizes where shades of gray dominate. By emboldening a glyph * slightly in relation to its pixel size, individual pixels get higher * coverage of filled-in outlines and are therefore `blacker'. This * counteracts the `thinning out' of glyphs, making text remain readable * at smaller sizes. * * By default, the Adobe engines for CFF, Type~1, and CID fonts darken * stems at smaller sizes, regardless of hinting, to enhance contrast. * Setting this property, stem darkening gets switched off. * * For the auto-hinter, stem-darkening is experimental currently and * thus switched off by default (this is, `no-stem-darkening' is set to * TRUE by default). Total consistency with the CFF driver is not * achieved right now because the emboldening method differs and glyphs * must be scaled down on the Y-axis to keep outline points inside their * precomputed blue zones. The smaller the size (especially 9ppem and * down), the higher the loss of emboldening versus the CFF driver. * * Note that stem darkening is never applied if @FT_LOAD_NO_SCALE is * set. * * { * FT_Library library; * FT_Bool no_stem_darkening = TRUE; * * * FT_Init_FreeType( &library ); * * FT_Property_Set( library, "cff", * "no-stem-darkening", &no_stem_darkening ); * } * * @note: * This property can be used with @FT_Property_Get also. * * This property can be set via the `FREETYPE_PROPERTIES' environment * variable (using values 1 and 0 for `on' and `off', respectively). * It can also be set per face using @FT_Face_Properties with * @FT_PARAM_TAG_STEM_DARKENING. * * @since: * 2.4.12 (for `cff' module) * * 2.6.2 (for `autofitter' module) * * 2.9 (for `type1' and `t1cid' modules) * */ /************************************************************************** * * @property: * darkening-parameters * * @description: * By default, the Adobe hinting engine, as used by the CFF, Type~1, and * CID font drivers, darkens stems as follows (if the * `no-stem-darkening' property isn't set): * * { * stem width <= 0.5px: darkening amount = 0.4px * stem width = 1px: darkening amount = 0.275px * stem width = 1.667px: darkening amount = 0.275px * stem width >= 2.333px: darkening amount = 0px * } * * and piecewise linear in-between. At configuration time, these four * control points can be set with the macro * `CFF_CONFIG_OPTION_DARKENING_PARAMETERS'; the CFF, Type~1, and CID * drivers share these values. At runtime, the control points can be * changed using the `darkening-parameters' property, as the following * example demonstrates for the Type~1 driver. * * { * FT_Library library; * FT_Int darken_params[8] = { 500, 300, // x1, y1 * 1000, 200, // x2, y2 * 1500, 100, // x3, y3 * 2000, 0 }; // x4, y4 * * * FT_Init_FreeType( &library ); * * FT_Property_Set( library, "type1", * "darkening-parameters", darken_params ); * } * * The x~values give the stem width, and the y~values the darkening * amount. The unit is 1000th of pixels. All coordinate values must be * positive; the x~values must be monotonically increasing; the * y~values must be monotonically decreasing and smaller than or * equal to 500 (corresponding to half a pixel); the slope of each * linear piece must be shallower than -1 (e.g., -.4). * * The auto-hinter provides this property, too, as an experimental * feature. See @no-stem-darkening for more. * * @note: * This property can be used with @FT_Property_Get also. * * This property can be set via the `FREETYPE_PROPERTIES' environment * variable, using eight comma-separated integers without spaces. Here * the above example, using `\' to break the line for readability. * * { * FREETYPE_PROPERTIES=\ * type1:darkening-parameters=500,300,1000,200,1500,100,2000,0 * } * * @since: * 2.5.1 (for `cff' module) * * 2.6.2 (for `autofitter' module) * * 2.9 (for `type1' and `t1cid' modules) * */ /************************************************************************** * * @property: * random-seed * * @description: * By default, the seed value for the CFF `random' operator and the * similar `0 28 callothersubr pop' command for the Type~1 and CID * drivers is set to a random value. However, mainly for debugging * purposes, it is often necessary to use a known value as a seed so * that the pseudo-random number sequences generated by `random' are * repeatable. * * The `random-seed' property does that. Its argument is a signed 32bit * integer; if the value is zero or negative, the seed given by the * `intitialRandomSeed' private DICT operator in a CFF file gets used * (or a default value if there is no such operator). If the value is * positive, use it instead of `initialRandomSeed', which is * consequently ignored. * * @note: * This property can be set via the `FREETYPE_PROPERTIES' environment * variable. It can also be set per face using @FT_Face_Properties with * @FT_PARAM_TAG_RANDOM_SEED. * * @since: * 2.8 (for `cff' module) * * 2.9 (for `type1' and `t1cid' modules) * */ /************************************************************************** * * @property: * no-long-family-names * * @description: * If PCF_CONFIG_OPTION_LONG_FAMILY_NAMES is active while compiling * FreeType, the PCF driver constructs long family names. * * There are many PCF fonts just called `Fixed' which look completely * different, and which have nothing to do with each other. When * selecting `Fixed' in KDE or Gnome one gets results that appear rather * random, the style changes often if one changes the size and one * cannot select some fonts at all. The improve this situation, the PCF * module prepends the foundry name (plus a space) to the family name. * It also checks whether there are `wide' characters; all put together, * family names like `Sony Fixed' or `Misc Fixed Wide' are constructed. * * If `no-long-family-names' is set, this feature gets switched off. * * { * FT_Library library; * FT_Bool no_long_family_names = TRUE; * * * FT_Init_FreeType( &library ); * * FT_Property_Set( library, "pcf", * "no-long-family-names", * &no_long_family_names ); * } * * @note: * This property can be used with @FT_Property_Get also. * * This property can be set via the `FREETYPE_PROPERTIES' environment * variable (using values 1 and 0 for `on' and `off', respectively). * * @since: * 2.8 */ /************************************************************************** * * @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). It is used in FreeType to select the `Infinality' * subpixel hinting code. The code may be removed in a future * version. * * TT_INTERPRETER_VERSION_40 :: * Version~40 corresponds to MS rasterizer v.2.1; it is roughly * equivalent to the hinting provided by DirectWrite ClearType (as can * be found, for example, in Microsoft's Edge Browser on Windows~10). * It is used in FreeType to select the `minimal' subpixel hinting * code, a stripped-down and higher performance version of the * `Infinality' code. * * @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 the configuration option * TT_CONFIG_OPTION_SUBPIXEL_HINTING, selecting version~38 or~40 causes * an `FT_Err_Unimplemented_Feature' error. * * Depending on the graphics framework, Microsoft uses different * bytecode and rendering engines. As a consequence, the version * numbers returned by a call to the `GETINFO' bytecode instruction are * more convoluted than desired. * * Here are two tables that try to shed some light on the possible * values for the MS rasterizer engine, together with the additional * features introduced by it. * * { * GETINFO framework version feature * ------------------------------------------------------------------- * 3 GDI (Win 3.1), v1.0 16-bit, first version * TrueImage * 33 GDI (Win NT 3.1), v1.5 32-bit * HP Laserjet * 34 GDI (Win 95) v1.6 font smoothing, * new SCANTYPE opcode * 35 GDI (Win 98/2000) v1.7 (UN)SCALED_COMPONENT_OFFSET * bits in composite glyphs * 36 MGDI (Win CE 2) v1.6+ classic ClearType * 37 GDI (XP and later), v1.8 ClearType * GDI+ old (before Vista) * 38 GDI+ old (Vista, Win 7), v1.9 subpixel ClearType, * WPF Y-direction ClearType, * additional error checking * 39 DWrite (before Win 8) v2.0 subpixel ClearType flags * in GETINFO opcode, * bug fixes * 40 GDI+ (after Win 7), v2.1 Y-direction ClearType flag * DWrite (Win 8) in GETINFO opcode, * Gray ClearType * } * * The `version' field gives a rough orientation only, since some * applications provided certain features much earlier (as an example, * Microsoft Reader used subpixel and Y-direction ClearType already in * Windows 2000). Similarly, updates to a given framework might include * improved hinting support. * * { * version sampling rendering comment * x y x y * -------------------------------------------------------------- * v1.0 normal normal B/W B/W bi-level * v1.6 high high gray gray grayscale * v1.8 high normal color-filter B/W (GDI) ClearType * v1.9 high high color-filter gray Color ClearType * v2.1 high normal gray B/W Gray ClearType * v2.1 high high gray gray Gray ClearType * } * * Color and Gray ClearType are the two available variants of * `Y-direction ClearType', meaning grayscale rasterization along the * Y-direction; the name used in the TrueType specification for this * feature is `symmetric smoothing'. `Classic ClearType' is the * original algorithm used before introducing a modified version in * Win~XP. Another name for v1.6's grayscale rendering is `font * smoothing', and `Color ClearType' is sometimes also called `DWrite * ClearType'. To differentiate between today's Color ClearType and the * earlier ClearType variant with B/W rendering along the vertical axis, * the latter is sometimes called `GDI ClearType'. * * `Normal' and `high' sampling describe the (virtual) resolution to * access the rasterized outline after the hinting process. `Normal' * means 1 sample per grid line (i.e., B/W). In the current Microsoft * implementation, `high' means an extra virtual resolution of 16x16 (or * 16x1) grid lines per pixel for bytecode instructions like `MIRP'. * After hinting, these 16 grid lines are mapped to 6x5 (or 6x1) grid * lines for color filtering if Color ClearType is activated. * * Note that `Gray ClearType' is essentially the same as v1.6's * grayscale rendering. However, the GETINFO instruction handles it * differently: v1.6 returns bit~12 (hinting for grayscale), while v2.1 * returns bits~13 (hinting for ClearType), 18 (symmetrical smoothing), * and~19 (Gray ClearType). Also, this mode respects bits 2 and~3 for * the version~1 gasp table exclusively (like Color ClearType), while * v1.6 only respects the values of version~0 (bits 0 and~1). * * Keep in mind that the features of the above interpreter versions * might not map exactly to FreeType features or behavior because it is * a fundamentally different library with different internals. * */ #define TT_INTERPRETER_VERSION_35 35 #define TT_INTERPRETER_VERSION_38 38 #define TT_INTERPRETER_VERSION_40 40 /************************************************************************** * * @property: * interpreter-version * * @description: * Currently, three versions are available, two representing the * bytecode interpreter with subpixel hinting support (old `Infinality' * code and new stripped-down and higher performance `minimal' code) and * one without, 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 (except if `native * ClearType' is selected by the font). Microsoft's 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) tweaks in Microsoft's interpreter. * * Details on subpixel hinting and some of the necessary tweaks can be * found in Greg Hitchcock's whitepaper at * `https://www.microsoft.com/typography/cleartype/truetypecleartype.aspx'. * Note that FreeType currently doesn't really `subpixel hint' (6x1, 6x2, * or 6x5 supersampling) like discussed in the paper. Depending on the * chosen interpreter, it simply ignores instructions on vertical stems * to arrive at very similar results. * * The following example code demonstrates how to deactivate subpixel * hinting (omitting the error handling). * * { * FT_Library library; * FT_Face face; * FT_UInt interpreter_version = TT_INTERPRETER_VERSION_35; * * * FT_Init_FreeType( &library ); * * FT_Property_Set( library, "truetype", * "interpreter-version", * &interpreter_version ); * } * * @note: * This property can be used with @FT_Property_Get also. * * This property can be set via the `FREETYPE_PROPERTIES' environment * variable (using values `35', `38', or `40'). * * @since: * 2.5 */ /************************************************************************** * * @property: * glyph-to-script-map * * @description: * *Experimental* *only* * * The auto-hinter provides various script modules to hint glyphs. * Examples of supported scripts are Latin or CJK. Before a glyph is * auto-hinted, the Unicode character map of the font gets examined, and * the script is then determined based on Unicode character ranges, see * below. * * OpenType fonts, however, often provide much more glyphs than * character codes (small caps, superscripts, ligatures, swashes, etc.), * to be controlled by so-called `features'. Handling OpenType features * can be quite complicated and thus needs a separate library on top of * FreeType. * * The mapping between glyph indices and scripts (in the auto-hinter * sense, see the @FT_AUTOHINTER_SCRIPT_XXX values) is stored as an * array with `num_glyphs' elements, as found in the font's @FT_Face * structure. The `glyph-to-script-map' property returns a pointer to * this array, which can be modified as needed. Note that the * modification should happen before the first glyph gets processed by * the auto-hinter so that the global analysis of the font shapes * actually uses the modified mapping. * * The following example code demonstrates how to access it (omitting * the error handling). * * { * FT_Library library; * FT_Face face; * FT_Prop_GlyphToScriptMap prop; * * * FT_Init_FreeType( &library ); * FT_New_Face( library, "foo.ttf", 0, &face ); * * prop.face = face; * * FT_Property_Get( library, "autofitter", * "glyph-to-script-map", &prop ); * * // adjust `prop.map' as needed right here * * FT_Load_Glyph( face, ..., FT_LOAD_FORCE_AUTOHINT ); * } * * @since: * 2.4.11 * */ /************************************************************************** * * @enum: * FT_AUTOHINTER_SCRIPT_XXX * * @description: * *Experimental* *only* * * A list of constants used for the @glyph-to-script-map property to * specify the script submodule the auto-hinter should use for hinting a * particular glyph. * * @values: * FT_AUTOHINTER_SCRIPT_NONE :: * Don't auto-hint this glyph. * * FT_AUTOHINTER_SCRIPT_LATIN :: * Apply the latin auto-hinter. For the auto-hinter, `latin' is a * very broad term, including Cyrillic and Greek also since characters * from those scripts share the same design constraints. * * By default, characters from the following Unicode ranges are * assigned to this submodule. * * { * U+0020 - U+007F // Basic Latin (no control characters) * U+00A0 - U+00FF // Latin-1 Supplement (no control characters) * U+0100 - U+017F // Latin Extended-A * U+0180 - U+024F // Latin Extended-B * U+0250 - U+02AF // IPA Extensions * U+02B0 - U+02FF // Spacing Modifier Letters * U+0300 - U+036F // Combining Diacritical Marks * U+0370 - U+03FF // Greek and Coptic * U+0400 - U+04FF // Cyrillic * U+0500 - U+052F // Cyrillic Supplement * U+1D00 - U+1D7F // Phonetic Extensions * U+1D80 - U+1DBF // Phonetic Extensions Supplement * U+1DC0 - U+1DFF // Combining Diacritical Marks Supplement * U+1E00 - U+1EFF // Latin Extended Additional * U+1F00 - U+1FFF // Greek Extended * U+2000 - U+206F // General Punctuation * U+2070 - U+209F // Superscripts and Subscripts * U+20A0 - U+20CF // Currency Symbols * U+2150 - U+218F // Number Forms * U+2460 - U+24FF // Enclosed Alphanumerics * U+2C60 - U+2C7F // Latin Extended-C * U+2DE0 - U+2DFF // Cyrillic Extended-A * U+2E00 - U+2E7F // Supplemental Punctuation * U+A640 - U+A69F // Cyrillic Extended-B * U+A720 - U+A7FF // Latin Extended-D * U+FB00 - U+FB06 // Alphab. Present. Forms (Latin Ligatures) * U+1D400 - U+1D7FF // Mathematical Alphanumeric Symbols * U+1F100 - U+1F1FF // Enclosed Alphanumeric Supplement * } * * FT_AUTOHINTER_SCRIPT_CJK :: * Apply the CJK auto-hinter, covering Chinese, Japanese, Korean, old * Vietnamese, and some other scripts. * * By default, characters from the following Unicode ranges are * assigned to this submodule. * * { * U+1100 - U+11FF // Hangul Jamo * U+2E80 - U+2EFF // CJK Radicals Supplement * U+2F00 - U+2FDF // Kangxi Radicals * U+2FF0 - U+2FFF // Ideographic Description Characters * U+3000 - U+303F // CJK Symbols and Punctuation * U+3040 - U+309F // Hiragana * U+30A0 - U+30FF // Katakana * U+3100 - U+312F // Bopomofo * U+3130 - U+318F // Hangul Compatibility Jamo * U+3190 - U+319F // Kanbun * U+31A0 - U+31BF // Bopomofo Extended * U+31C0 - U+31EF // CJK Strokes * U+31F0 - U+31FF // Katakana Phonetic Extensions * U+3200 - U+32FF // Enclosed CJK Letters and Months * U+3300 - U+33FF // CJK Compatibility * U+3400 - U+4DBF // CJK Unified Ideographs Extension A * U+4DC0 - U+4DFF // Yijing Hexagram Symbols * U+4E00 - U+9FFF // CJK Unified Ideographs * U+A960 - U+A97F // Hangul Jamo Extended-A * U+AC00 - U+D7AF // Hangul Syllables * U+D7B0 - U+D7FF // Hangul Jamo Extended-B * U+F900 - U+FAFF // CJK Compatibility Ideographs * U+FE10 - U+FE1F // Vertical forms * U+FE30 - U+FE4F // CJK Compatibility Forms * U+FF00 - U+FFEF // Halfwidth and Fullwidth Forms * U+1B000 - U+1B0FF // Kana Supplement * U+1D300 - U+1D35F // Tai Xuan Hing Symbols * U+1F200 - U+1F2FF // Enclosed Ideographic Supplement * U+20000 - U+2A6DF // CJK Unified Ideographs Extension B * U+2A700 - U+2B73F // CJK Unified Ideographs Extension C * U+2B740 - U+2B81F // CJK Unified Ideographs Extension D * U+2F800 - U+2FA1F // CJK Compatibility Ideographs Supplement * } * * FT_AUTOHINTER_SCRIPT_INDIC :: * Apply the indic auto-hinter, covering all major scripts from the * Indian sub-continent and some other related scripts like Thai, Lao, * or Tibetan. * * By default, characters from the following Unicode ranges are * assigned to this submodule. * * { * U+0900 - U+0DFF // Indic Range * U+0F00 - U+0FFF // Tibetan * U+1900 - U+194F // Limbu * U+1B80 - U+1BBF // Sundanese * U+A800 - U+A82F // Syloti Nagri * U+ABC0 - U+ABFF // Meetei Mayek * U+11800 - U+118DF // Sharada * } * * Note that currently Indic support is rudimentary only, missing blue * zone support. * * @since: * 2.4.11 * */ #define FT_AUTOHINTER_SCRIPT_NONE 0 #define FT_AUTOHINTER_SCRIPT_LATIN 1 #define FT_AUTOHINTER_SCRIPT_CJK 2 #define FT_AUTOHINTER_SCRIPT_INDIC 3 /************************************************************************** * * @struct: * FT_Prop_GlyphToScriptMap * * @description: * *Experimental* *only* * * The data exchange structure for the @glyph-to-script-map property. * * @since: * 2.4.11 * */ typedef struct FT_Prop_GlyphToScriptMap_ { FT_Face face; FT_UShort* map; } FT_Prop_GlyphToScriptMap; /************************************************************************** * * @property: * fallback-script * * @description: * *Experimental* *only* * * If no auto-hinter script module can be assigned to a glyph, a * fallback script gets assigned to it (see also the * @glyph-to-script-map property). By default, this is * @FT_AUTOHINTER_SCRIPT_CJK. Using the `fallback-script' property, * this fallback value can be changed. * * { * FT_Library library; * FT_UInt fallback_script = FT_AUTOHINTER_SCRIPT_NONE; * * * FT_Init_FreeType( &library ); * * FT_Property_Set( library, "autofitter", * "fallback-script", &fallback_script ); * } * * @note: * This property can be used with @FT_Property_Get also. * * It's important to use the right timing for changing this value: The * creation of the glyph-to-script map that eventually uses the * fallback script value gets triggered either by setting or reading a * face-specific property like @glyph-to-script-map, or by auto-hinting * any glyph from that face. In particular, if you have already created * an @FT_Face structure but not loaded any glyph (using the * auto-hinter), a change of the fallback script will affect this face. * * @since: * 2.4.11 * */ /************************************************************************** * * @property: * default-script * * @description: * *Experimental* *only* * * If FreeType gets compiled with FT_CONFIG_OPTION_USE_HARFBUZZ to make * the HarfBuzz library access OpenType features for getting better * glyph coverages, this property sets the (auto-fitter) script to be * used for the default (OpenType) script data of a font's GSUB table. * Features for the default script are intended for all scripts not * explicitly handled in GSUB; an example is a `dlig' feature, * containing the combination of the characters `T', `E', and `L' to * form a `TEL' ligature. * * By default, this is @FT_AUTOHINTER_SCRIPT_LATIN. Using the * `default-script' property, this default value can be changed. * * { * FT_Library library; * FT_UInt default_script = FT_AUTOHINTER_SCRIPT_NONE; * * * FT_Init_FreeType( &library ); * * FT_Property_Set( library, "autofitter", * "default-script", &default_script ); * } * * @note: * This property can be used with @FT_Property_Get also. * * It's important to use the right timing for changing this value: The * creation of the glyph-to-script map that eventually uses the * default script value gets triggered either by setting or reading a * face-specific property like @glyph-to-script-map, or by auto-hinting * any glyph from that face. In particular, if you have already created * an @FT_Face structure but not loaded any glyph (using the * auto-hinter), a change of the default script will affect this face. * * @since: * 2.5.3 * */ /************************************************************************** * * @property: * increase-x-height * * @description: * For ppem values in the range 6~<= ppem <= `increase-x-height', round * up the font's x~height much more often than normally. If the value * is set to~0, which is the default, this feature is switched off. Use * this property to improve the legibility of small font sizes if * necessary. * * { * FT_Library library; * FT_Face face; * FT_Prop_IncreaseXHeight prop; * * * FT_Init_FreeType( &library ); * FT_New_Face( library, "foo.ttf", 0, &face ); * FT_Set_Char_Size( face, 10 * 64, 0, 72, 0 ); * * prop.face = face; * prop.limit = 14; * * FT_Property_Set( library, "autofitter", * "increase-x-height", &prop ); * } * * @note: * This property can be used with @FT_Property_Get also. * * Set this value right after calling @FT_Set_Char_Size, but before * loading any glyph (using the auto-hinter). * * @since: * 2.4.11 * */ /************************************************************************** * * @struct: * FT_Prop_IncreaseXHeight * * @description: * The data exchange structure for the @increase-x-height property. * */ typedef struct FT_Prop_IncreaseXHeight_ { FT_Face face; FT_UInt limit; } FT_Prop_IncreaseXHeight; /************************************************************************** * * @property: * warping * * @description: * *Experimental* *only* * * If FreeType gets compiled with option AF_CONFIG_OPTION_USE_WARPER to * activate the warp hinting code in the auto-hinter, this property * switches warping on and off. * * Warping only works in `normal' auto-hinting mode replacing it. * The idea of the code is to slightly scale and shift a glyph along * the non-hinted dimension (which is usually the horizontal axis) so * that as much of its segments are aligned (more or less) to the grid. * To find out a glyph's optimal scaling and shifting value, various * parameter combinations are tried and scored. * * By default, warping is off. The example below shows how to switch on * warping (omitting the error handling). * * { * FT_Library library; * FT_Bool warping = 1; * * * FT_Init_FreeType( &library ); * * FT_Property_Set( library, "autofitter", * "warping", &warping ); * } * * @note: * This property can be used with @FT_Property_Get also. * * This property can be set via the `FREETYPE_PROPERTIES' environment * variable (using values 1 and 0 for `on' and `off', respectively). * * The warping code can also change advance widths. Have a look at the * `lsb_delta' and `rsb_delta' fields in the @FT_GlyphSlotRec structure * for details on improving inter-glyph distances while rendering. * * Since warping is a global property of the auto-hinter it is best to * change its value before rendering any face. Otherwise, you should * reload all faces that get auto-hinted in `normal' hinting mode. * * @since: * 2.6 * */ /* */ FT_END_HEADER #endif /* FTDRIVER_H_ */ /* END */
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