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freetype.h: Improve Unicode Variation Sequence documentation.

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Harmony
Werner Lemberg 8 years ago
parent 464b16ba46
commit 1c19b54999
1 changed files with 51 additions and 40 deletions
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  1. 91
      include/freetype/freetype.h

91
include/freetype/freetype.h
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@ -3804,40 +3804,51 @@ FT_BEGIN_HEADER
/* glyph_variants */
/* */
/* <Title> */
/* Glyph Variants */
/* Unicode Variation Sequences */
/* */
/* <Abstract> */
/* The FreeType~2 interface to Unicode Ideographic Variation */
/* Sequences (IVS), using the SFNT cmap format~14. */
/* The FreeType~2 interface to Unicode Variation Sequences (UVS), */
/* using the SFNT cmap format~14. */
/* */
/* <Description> */
/* Many CJK characters have variant forms. They are a sort of grey */
/* area somewhere between being totally irrelevant and semantically */
/* distinct; for this reason, the Unicode consortium decided to */
/* introduce Ideographic Variation Sequences (IVS), consisting of a */
/* Unicode base character and one of 240 variant selectors */
/* (U+E0100-U+E01EF), instead of further extending the already huge */
/* code range for CJK characters. */
/* */
/* An IVS is registered and unique; for further details please refer */
/* to Unicode Technical Standard #37, the Ideographic Variation */
/* Database: */
/* */
/* http://www.unicode.org/reports/tr37/ */
/* http://www.unicode.org/ivd/ */
/* */
/* To date (January 2017), the character with the most variants is */
/* U+9089, having 32 such IVS. */
/* */
/* Adobe and MS decided to support IVS with a new cmap subtable */
/* (format~14). It is an odd subtable because it is not a mapping of */
/* input code points to glyphs, but contains lists of all variants */
/* supported by the font. */
/* */
/* A variant may be either `default' or `non-default'. A default */
/* variant is the one you will get for that code point if you look it */
/* up in the standard Unicode cmap. A non-default variant is a */
/* different glyph. */
/* Many characters, especially for CJK scripts, have variant forms. */
/* They are a sort of grey area somewhere between being totally */
/* irrelevant and semantically distinct; for this reason, the Unicode */
/* consortium decided to introduce Variation Sequences (VS), */
/* consisting of a Unicode base character and a variation selector */
/* instead of further extending the already huge number of */
/* characters. */
/* */
/* Unicode maintains two different sets, namely `Standardized */
/* Variation Sequences' and registered `Ideographic Variation */
/* Sequences' (IVS), collected in the `Ideographic Variation */
/* Database' (IVD). */
/* */
/* http://unicode.org/Public/UCD/latest/ucd/StandardizedVariants.txt */
/* http://unicode.org/reports/tr37/ */
/* http://unicode.org/ivd/ */
/* */
/* To date (January 2017), the character with the most ideographic */
/* variations is U+9089, having 32 such IVS. */
/* */
/* Three Mongolian Variation Selectors have the values U+180B-U+180D; */
/* 256 generic Variation Selectors are encoded in the ranges */
/* U+FE00-U+FE0F and U+E0100-U+E01EF. IVS currently use Variation */
/* Selectors from the range U+E0100-U+E01EF only. */
/* */
/* A VS consists of the base character value followed by a single */
/* Variation Selector. For example, to get the first variation of */
/* U+9089, you have to write the character sequence `U+9089 U+E0100'. */
/* */
/* Adobe and MS decided to support both standardized and ideographic */
/* VS with a new cmap subtable (format~14). It is an odd subtable */
/* because it is not a mapping of input code points to glyphs, but */
/* contains lists of all variations supported by the font. */
/* */
/* A variation may be either `default' or `non-default' for a given */
/* font. A default variation is the one you will get for that code */
/* point if you look it up in the standard Unicode cmap. A */
/* non-default variation is a different glyph. */
/* */
/*************************************************************************/
@ -3893,8 +3904,8 @@ FT_BEGIN_HEADER
/* FT_Face_GetCharVariantIsDefault */
/* */
/* <Description> */
/* Check whether this variant of this Unicode character is the one to */
/* be found in the `cmap'. */
/* Check whether this variation of this Unicode character is the one */
/* to be found in the `cmap'. */
/* */
/* <Input> */
/* face :: */
@ -3908,7 +3919,7 @@ FT_BEGIN_HEADER
/* */
/* <Return> */
/* 1~if found in the standard (Unicode) cmap, 0~if found in the */
/* variation selector cmap, or -1 if it is not a variant. */
/* variation selector cmap, or -1 if it is not a variation. */
/* */
/* <Note> */
/* This function is only meaningful if the font has a variation */
@ -3929,7 +3940,7 @@ FT_BEGIN_HEADER
/* FT_Face_GetVariantSelectors */
/* */
/* <Description> */
/* Return a zero-terminated list of Unicode variant selectors found */
/* Return a zero-terminated list of Unicode variation selectors found */
/* in the font. */
/* */
/* <Input> */
@ -3938,7 +3949,7 @@ FT_BEGIN_HEADER
/* */
/* <Return> */
/* A pointer to an array of selector code points, or NULL if there is */
/* no valid variant selector cmap subtable. */
/* no valid variation selector cmap subtable. */
/* */
/* <Note> */
/* The last item in the array is~0; the array is owned by the */
@ -3958,7 +3969,7 @@ FT_BEGIN_HEADER
/* FT_Face_GetVariantsOfChar */
/* */
/* <Description> */
/* Return a zero-terminated list of Unicode variant selectors found */
/* Return a zero-terminated list of Unicode variation selectors found */
/* for the specified character code. */
/* */
/* <Input> */
@ -3969,7 +3980,7 @@ FT_BEGIN_HEADER
/* The character codepoint in Unicode. */
/* */
/* <Return> */
/* A pointer to an array of variant selector code points that are */
/* A pointer to an array of variation selector code points that are */
/* active for the given character, or NULL if the corresponding list */
/* is empty. */
/* */
@ -3993,19 +4004,19 @@ FT_BEGIN_HEADER
/* */
/* <Description> */
/* Return a zero-terminated list of Unicode character codes found for */
/* the specified variant selector. */
/* the specified variation selector. */
/* */
/* <Input> */
/* face :: */
/* A handle to the source face object. */
/* */
/* variantSelector :: */
/* The variant selector code point in Unicode. */
/* The variation selector code point in Unicode. */
/* */
/* <Return> */
/* A list of all the code points that are specified by this selector */
/* (both default and non-default codes are returned) or NULL if there */
/* is no valid cmap or the variant selector is invalid. */
/* is no valid cmap or the variation selector is invalid. */
/* */
/* <Note> */
/* The last item in the array is~0; the array is owned by the */

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