Encoding italic

James Kass via Unicode unicode at unicode.org
Sun Feb 10 09:31:57 CST 2019

Philippe Verdy wrote,

 >> ...[one font file having both italic and roman]...
 > The only case where it happens in real fonts is for the mapping of
 > Mathematical Symbols which have a distinct encoding for some
 > variants ...

William Overington made a proof-of-concept font using the VS14 character 
to access the italic glyphs which were, of course, in the same real 
font.  Which means that the developer of a font such as Deja Vu Math TeX 
Gyre could set up an OpenType table mapping the Basic Latin in the font 
to the italic math letter glyphs in the same font using the VS14 
characters.  Such a font would work interoperably on modern systems.  
Such a font would display italic letters both if encoded as math 
alphanumerics or if encoded as ASCII plus VS14.  Significantly, the 
display would be identical.

 > ...[math alphanumerics]...
 > These were allowed in Unicode because of their specific contextual
 > use as distinctive symbols from known standards, and not for general
 > use in human languages

They were encoded for interoperability and round-tripping because they 
existed in character sets such as STIX.  They remain Latin letter form 
variants.  If they had been encoded as the variant forms which 
constitute their essential identity it would have broken the character 
vs. glyph encoding model of that era.  Arguing that they must not be 
used other than for scientific purposes is just so much semantic 
quibbling in order to justify their encoding.

Suppose we started using the double struck ASCII variants on this list 
in order to note Unicode character numbers such as ��+�������� or 
��+��������?  Hexadecimal notation is certainly math and Unicode can be 
considered a science.  Would that be “math abuse” if we did it?  (Is 
linguistics not a science?)

 > (because these encodings are defective and don't have the necessary
 > coverage, notably for the many diacritics,

The combining diacritics would be used.

 > case mappings,

Adjust them as needed.

 > and other linguisitic, segmentation and layout properties).
 > The same can be said about superscript/subscript variants,
 > ... : they have specific use and not made for general purpose texts ...

So people who used ISO-8859-1 were not allowed to use the superscript 
digits therein for marking footnotes?  Those superscript digits were 
reserved by ISO-8859-1 only for use by math and science?

Decomposition mapping:  U+0041
Binary properties:  Math, Alphabetic, Uppercase, Grapheme Base, ...

Decomposition mapping:  U+0032
Binary properties:  Grapheme Base

Decomposition mapping:  U+0063
Binary properties:  Alphabetic, Lowercase, Grapheme Base, ...

More information about the Unicode mailing list