[XeTeX] List of ligatures in a font

[d fulano]

>\defaultfontfeatures{Mapping=tex-text}

>

>informs the XeTeX engine to use the standard ligatures, as TeX would do by default.

 
Many thanks for the prompt reply!
 

But this is exactly my question:: how do I determine what are the "standard ligatures" in a font?

It is not obvious (especially for non-English languages), and they can also vary in each font.

Basically what I want to do is this:

I can very quicky loop from 1-65535 and use \iffontchar to test if a character exists in the font, 

and thus print all the glyphs in the font as a table, for my information.
 
I would like to add to this a list of all the ligatures of the font.

In the absence of any other ideas, I can test every combination of pairs of glyphs, 

and then if the pair forms a ligature, I want to print this. 

 

But I don't know how to test if 2 characters will combine into a ligature. 


Thanks
 

(I know I can use a font editor etc to study the inside ligatures of the font, but 

this is difficult to print nicely and I am trying to do this in Xe(la)TeX..

After all, XeTeX should know this information, No? . )