From: James Kass (thunder-bird@earthlink.net)
Date: Tue Aug 28 2007 - 10:22:09 CDT
Mark Davis wrote,
> And the CJK VS characters should never be visible
> in a font that has CJK characters.
"...in a font that has CJK characters." This is an important point.
The developer would be well advised to include some kind of glyph
for VS characters, but only if the font being designed supports
base characters which can combine with VS characters in valid
sequences.
In other words, a font not designed to support math characters
and which does not support VS characters would be expected to
display two little boxes for a valid string consisting of a math
base character plus a VS character.
If the font supports VS characters for any other sequences, but
does not support math characters, and the font uses control
picture glyphs for VS characters, then the above string would
display as a little box plus the control picture for the VS. If
this font instead maps zero-width no-contour glyphs with VS
characters, then the display will just be one free standing little
box.
Please note that the above rendering descriptions represent the
way things actually work right now, rather than being an opinion
concerning optimal performance. I do think, though, that things
are working just fine.
Because of the various possible factor combinations, the font
developer should retain control of font character coverage.
And, I just can't seem to leave this alone...
> And the CJK VS characters should never be visible
> in a font that has CJK characters.
...except during input/editing, if the font designer so desires
and designs accordingly. In this case, though, the display of
an invalid or unsupported (by the font) sequence would result
in a display of a control picture rather than being transparent
to the reader. Font designers can be well aware of this, yet
choose to use control pictures anyway.
Best regards,
James Kass
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