I added a contextual ligature feature to some of my fonts, which uses the
Velthuis encoding system.
Some Buddhist scholars use this method for writing Pali as it requires no special fonts to be installed that supports the diacritics. If the contextual alternates feature is applied to Velthuis encoded text in my fonts, it switches to text with the correct diacritics. So, for example:
Eva.m me sutta.m — eka.m samaya.m Bhagavaa karuusu viharati kammaasadhamma.m naama karuuna.m nigamo
would become:-
Evaṃ me sutaṃ — ekaṃ samayaṃ Bhagavā kurūsu viharati kammāsadhammaṃ nāma kurūnaṃ nigamo
This is all well and good in PagePlus, where Contextual Ligatures can be disabled or enabled as required.
However, someone recently submitted a "bug report" presumably because they typed an abbreviation like A.D. and were surprised to see it change to AḌ. I think some applications apply calt by default with no option to disable it!?
Is there some other feature I could use instead of calt?
My fonts already have Standard Ligatures (liga), discretionary ligatures (dlig), historical ligatures (hlig), Stylistic Alternates (salt) to replace the now obsolete Initial Forms for Decorative Drop Capitals, and Character Variants (cv01) for quick access to symbols.
Comments
How would the application know that the language in use was Pāḷi?
I tried, but PagePlus doesn't know anything about the locl tag, not even for Romanian, and there's no Pali language to select.
I tried adding a second dlig feature, but that is just treated like a single feature with both substitution tables. I don't really want discretionary ligatures like cky to be enabled just to type Velthuis encoded Paa.li text.
I understand what you are trying to do, but it's never going to be a reliable mechanism to handle this at the glyph display level. I would be trying to encourage such scholars to work with character substitution macros, so they can type text using this kind of simplified input, and then have it converted to standard Unicode for the diacritics.
Over the years, I have worked with scholars of ancient Greek, Sanskrit, and other languages who have relied on non-Unicode input methods and fonts for many years. It's always been best to help them transition to Unicode, rather than trying to accommodate their non-standard encodings.
I could simply remove it, of course, but then one has to run macros (limited by app) to convert Velthuis encoded text to Unicode and vice versa for those using apps that don't support Unicode.
I like 'dlig', but if you are using that for other things in the same font, it might be a bad choice.
It's not clear to me that "contextual" is really relevant either: you're not substituting (say) the default "m" with a different glyph when it's preceded or followed by certain glyph sequences; you're substituting ".m" in all contexts by a different glyph. These are ligature substitutions, but they're not ligatures in the most familiar sense.
What about ss01?
It has the additional benefit of showing on the Context Toolbar OpenType features drop down in PagePlus, so it can be enabled/disabled very easily.
Thank you for the suggestion.