I'd use ct for discretionary, and ſf for historic.
_____________________________________________
Personal Art and Design Portal of Ivan Gulkov
www.ivangdesign.com

Hi Si,
here’s a little survey I did:

Adobe: ffi for ‘Ligatures’
Dalton Maag: ffi for ‘OpenType Ligatures’
FontFont (in PDFs): fi for ‘Standard Ligatures’, ct for ‘Discretionary Ligatures’
German Type Foundry: fi for ‘Standard Ligatures’, ffj for ‘Discretionary Ligatures’, ſſk for ‘Historical Ligatures
Linotype: ffi for ‘Ligatures’
MyFonts: ff for ‘Ligatures’, st for ‘Extra Ligatures’
Storm: fi fl for ‘Standard Ligatures’, st ct for ‘Discretionary Ligatures’

Related thread: Standardized font feature icons
F

Thanks for the leads!

Cheers, Si

I like Th for discretionary. Some people really like it as a ligature and some don't.

That’s a good point – in principle. The problem is that the difference of a ligated ‘Th’ and a plain ‘Th’ is not very obvious, at icon size.

Another complication is that Adobe includes T_h ligature in their standard {liga} feature, not {dlig}.

I personally wish it was discretionary, but that's not the case currently in Adobe Pro fonts. Which, like it or not, tend to set the expectations.

Even across Adobe fonts, the classification of ligatures is not consistent. It’s a design decision. ‘ct’ and ‘st’ are a {dlig} in Arno and Garamond Premier – and a {hlig} in Hypatia Sans. ‘ſt' is a {liga} in Arno, GPP, Hypatia – and a {dlig} in Jenson. It often depends on the style and genre of the font in question (I guess you have no problem with ‘Th’ being a standard lig in Caflisch Script, do you?). I can imagine decisions have also been made with regard to feature support in the common applications.

> (I guess you have no problem with ‘Th’ being a standard lig in Caflisch Script, do you?)

Good point, Florian. I don't mind the T_h in Caflisch.

But neither do I feel it is required in order to compensate for a collision or impossible spacing in the way the f ligatures generally are. Plain ol' Th in Caflisch works just fine. So, I'd still argue that it's better placed in the {dlig} feature.

But, back to the main point: T_h is not a good candidate as a representative icon for discretionary ligatures.

-- K.