[omega] Question about the paper published in EuroTeX 2005

[Yannis Haralambous]

Le 30 mars 05, à 15h08, Chris Rowley a écrit :

>> you refer to re-ordering as done by Uniscribe/ATSUI/Pango. This should
>> be
>> feasible through an OTP, or maybe at a more global level so that we 
>> can
>> apply bidi
>> across buffer boundaries. These are problems we are searching upon.
>>
>
> More to the general idea that, as I understand it, one is not meant to
> access glyphs in an OpenType-style of font resource

That's a very interesting issue we are dealing with. technically 
speaking, the glyph index is not a robust way to access a glyph in a 
TrueType-like structure. For example, you can re-order the glyphs in a 
TrueType font and it still is exactly the same font (while Type 1 fonts 
have glyph names).

But we don't have the choice. If we want to interfere with OpenType 
tables we just have to dig into the font and access the glyphs. Maybe 
we will use signature calculations to find unique identifiers for 
individual glyphs in a font so that we can recognize them if for any 
reason the font is re-ordered. That would require a table saying that 
"glyph index 37 = glyph signature 1F35OA726BB89A" and then one would be 
able write code using \glyphindex{37}.

This brings us back to the old problem about how do we identify a font? 
(besides version of the whole, of each glyph, of metrics, of metadata, 
of encodings, one could use signatures, and even the DNA signature of 
the designer).

To return to OpenType fonts, the current status of our development plan 
is to implement "consulting of metrics", "consulting of GPOS" and 
"consulting of GSUB" as three actions similar to OTPs, so that one can 
place real OTPs between or after these actions.
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