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diff --git a/src/3rdparty/freetype/include/freetype/ftdriver.h b/src/3rdparty/freetype/include/freetype/ftdriver.h new file mode 100644 index 0000000000..e90475b2af --- /dev/null +++ b/src/3rdparty/freetype/include/freetype/ftdriver.h @@ -0,0 +1,1225 @@ +/***************************************************************************/ +/* */ +/* 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 */ |