< prev index next >
src/java.desktop/share/native/libfreetype/include/freetype/ftdriver.h
Print this page
*** 1,21 ****
! /***************************************************************************/
! /* */
! /* 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_
--- 1,21 ----
! /****************************************************************************
! *
! * ftdriver.h
! *
! * FreeType API for controlling driver modules (specification only).
! *
! * Copyright (C) 2017-2019 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_
*** 48,59 ****
* 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
--- 48,59 ----
* 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
*** 72,149 ****
*
* @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.
*
*/
/**************************************************************************
--- 72,148 ----
*
* @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.
*
*/
/**************************************************************************
*** 156,172 ****
*
* @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'.
*
*/
/**************************************************************************
--- 155,171 ----
*
* @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'.
*
*/
/**************************************************************************
*** 185,203 ****
* 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.
*
*/
/**************************************************************************
--- 184,202 ----
* 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.
*
*/
/**************************************************************************
*** 215,305 ****
* 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.
*
*/
/**************************************************************************
--- 214,304 ----
* 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://rastertragedy.com/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://rastertragedy.com/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://rastertragedy.com/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://rastertragedy.com/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.
*
*/
/**************************************************************************
*** 326,337 ****
*
* @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.
*
--- 325,336 ----
*
* @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.
*
*** 354,474 ****
*
* @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)
*
*/
/**************************************************************************
--- 353,474 ----
*
* @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.
*
+ * @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').
+ *
+ * @example:
* 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_HINTING_ADOBE;
*
*
* FT_Init_FreeType( &library );
*
* FT_Property_Set( library, "cff",
* "hinting-engine", &hinting_engine );
! * ```
*
* @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.
*
! * @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.
! *
! * @example:
! * ```
* FT_Library library;
* FT_Bool no_stem_darkening = TRUE;
*
*
* FT_Init_FreeType( &library );
*
* FT_Property_Set( library, "cff",
* "no-stem-darkening", &no_stem_darkening );
! * ```
*
* @since:
! * 2.4.12 (for 'cff' module)
*
! * 2.6.2 (for 'autofitter' module)
*
! * 2.9 (for 'type1' and 't1cid' modules)
*
*/
/**************************************************************************
*** 476,618 ****
* @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
*/
--- 476,620 ----
* @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 (see the example
! * below that demonstrates this for the Type~1 driver).
*
* 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
! * ```
! *
! * @example:
! * ```
! * 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 );
! * ```
*
* @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.
*
! * @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).
! *
! * @example:
! * ```
* 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 );
! * ```
*
* @since:
* 2.8
*/
*** 624,677 ****
*
* @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
--- 626,678 ----
*
* @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
*** 690,749 ****
* 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
--- 691,750 ----
* 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
*** 753,806 ****
*
* @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
*/
--- 754,808 ----
*
* @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.
*
+ * @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').
+ *
+ * @example:
* 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 );
! * ```
*
* @since:
* 2.5
*/
*** 809,845 ****
*
* @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;
*
*
--- 811,848 ----
*
* @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.
! *
! * @example:
! * The following example code demonstrates how to access it (omitting the
! * error handling).
*
! * ```
* FT_Library library;
* FT_Face face;
* FT_Prop_GlyphToScriptMap prop;
*
*
*** 852,862 ****
* "glyph-to-script-map", &prop );
*
* // adjust `prop.map' as needed right here
*
* FT_Load_Glyph( face, ..., FT_LOAD_FORCE_AUTOHINT );
! * }
*
* @since:
* 2.4.11
*
*/
--- 855,865 ----
* "glyph-to-script-map", &prop );
*
* // adjust `prop.map' as needed right here
*
* FT_Load_Glyph( face, ..., FT_LOAD_FORCE_AUTOHINT );
! * ```
*
* @since:
* 2.4.11
*
*/
*** 866,894 ****
*
* @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
--- 869,897 ----
*
* @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
*** 913,932 ****
* 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
--- 916,935 ----
* 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
*** 955,983 ****
* 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:
--- 958,986 ----
* 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:
*** 994,1004 ****
*
* @struct:
* FT_Prop_GlyphToScriptMap
*
* @description:
! * *Experimental* *only*
*
* The data exchange structure for the @glyph-to-script-map property.
*
* @since:
* 2.4.11
--- 997,1007 ----
*
* @struct:
* FT_Prop_GlyphToScriptMap
*
* @description:
! * **Experimental only**
*
* The data exchange structure for the @glyph-to-script-map property.
*
* @since:
* 2.4.11
*** 1016,1055 ****
*
* @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
*
*/
--- 1019,1058 ----
*
* @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.
*
* @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.
*
+ * @example:
+ * ```
+ * FT_Library library;
+ * FT_UInt fallback_script = FT_AUTOHINTER_SCRIPT_NONE;
+ *
+ *
+ * FT_Init_FreeType( &library );
+ *
+ * FT_Property_Set( library, "autofitter",
+ * "fallback-script", &fallback_script );
+ * ```
+ *
* @since:
* 2.4.11
*
*/
*** 1058,1103 ****
*
* @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
*
*/
--- 1061,1107 ----
*
* @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.
*
* @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.
*
+ * @example:
+ * ```
+ * FT_Library library;
+ * FT_UInt default_script = FT_AUTOHINTER_SCRIPT_NONE;
+ *
+ *
+ * FT_Init_FreeType( &library );
+ *
+ * FT_Property_Set( library, "autofitter",
+ * "default-script", &default_script );
+ * ```
+ *
* @since:
* 2.5.3
*
*/
*** 1106,1122 ****
*
* @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;
*
*
--- 1110,1133 ----
*
* @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.
*
! * @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).
! *
! * @example:
! * ```
* FT_Library library;
* FT_Face face;
* FT_Prop_IncreaseXHeight prop;
*
*
*** 1127,1143 ****
* 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
*
*/
--- 1138,1148 ----
* prop.face = face;
* prop.limit = 14;
*
* FT_Property_Set( library, "autofitter",
* "increase-x-height", &prop );
! * ```
*
* @since:
* 2.4.11
*
*/
*** 1164,1213 ****
*
* @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
*
*/
--- 1169,1220 ----
*
* @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.
*
* @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.
! *
! * @example:
! * This example 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 );
! * ```
*
* @since:
* 2.6
*
*/
< prev index next >