On 14 Mar 2012, at 20:17, Peter Dyballa wrote:

> 
> Am 14.3.2012 um 17:32 schrieb d fulano:
> 
>> But this is exactly my question:: how do I determine what are the "standard 
>> ligatures" in a font?

I presume you mean "what ligatures will be used by default when typesetting 
with this font" -- i.e., they don't require explicitly activating optional 
features, they're implemented as part of the 'liga' feature (or other 
on-by-default features).

The flexibility of OpenType lookups makes this a hard question to answer. Even 
if you exhaustively try every pair of characters, you might miss ligatures that 
only occur when a given pair is found _in a particular context_. And what about 
a ligature of more than two characters? The old OS X (AAT) version of Zapfino, 
for example, had a special 7-character ligature for the word "Zapfino". No 
amount of checking character *pairs* would detect that.

> 
> Then see which ligatures are defined by the Unicode consortium in the recent 
> release, version 6.

Completely irrelevant. The (few) "ligature" characters encoded in Unicode - 
mostly for legacy-compatibility reasons - have no bearing on what ligatures may 
be present in any particular OpenType font.

> You can also determine the names of the glyphs in a font outside of XeTeX and 
> check for example for the three characters "lig" or "LIG" or "Lig", or in 
> even more variations, in their names. Likely you'll find a few more. And some 
> can have names like "ufb03" or "afii57718".

You can determine the glyph names within xetex, even. But as there are a number 
of conventions for glyph names - as well as the freedom for the designer to 
ignore all the glyph-naming conventions! - this won't really help. Glyph names 
are not a reliable indicator of which glyphs are ligatures (nor of which 
character pairs or sequences will be mapped to those ligatures, nor whether 
they'd be enabled by default - which I think was a key part of the original 
question).

JK




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