From: James Kass (thunder-bird@earthlink.net)
Date: Tue Aug 28 2007 - 07:34:24 CDT
Philippe Verdy wrote,
>Asmus Freytag wrote:
>> Variation selectors have no business being visible - unless you are in a
>> special mode. The whole idea behind them is that they can (and should)
>> be ignored when the resources to act on them (variant glyphs) are not
>> present.
>
>That's exactly the same conclusion I made when I suggested that renderers
>strip the variation selectors not supported in the selected font...
>
>There's never any good reason to show the .notdef glyph of that font,
>because according to Unicode reference, the sequence <char+VS> should be
>treated like <char> without the VS, (except in special algorithms described
>in the standard or its annexes) if the VS makes no sense with the available
>local data.
>
>If renderers were updated to do that, variation selectors could be used more
>easily and widely, and a reasonable default rendering would still be
>available if there's no font defining glyphs for the specific variations...
>and this would not create "bogous text" that readers are seeing, full of
>boxes.
A font which does not support VS sequences and has no glyph data
mapped with VS characters will display the base character glyph
plus the font's missing glyph in default rendering mode. (In plain
text.) Just like any other combining mark character unsupported
by a font.
The developer can anticipate this and map the VS characters with
zero-width no-contour glyphs in order to avoid having the missing
glyph displayed.
This would be a good recommendation, along the lines of Mark Davis'
original suggestion. However, choices of glyph design and font
coverage should remain with the font developer.
Font developers are in the best position to know the intended uses
of their fonts, and design accordingly.
So I would suggest that the rendering engines be left alone in this
case. Any reader seeing unwanted boxes in any situation should
simply select an appropriate font. The presence of the boxes in
any text means that the selected font does not support some of
the characters it is being called to display.
Best regards,
James Kass
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