I’m working on a font that has Latin and Devanagari figure. The default latin figures are old style and the Devanagari is the same height as the latin caps, so the default Indian Rupee symbol does not harmonize with the Devanagari figures. I’ve designed a matching Indian Rupee symbol for the Devangari, but I can’t find an OpenType substitution that makes it work in Adobe apps. Substitution does not work in script deva; script dev2; or language hin; language mar; language nep;. John Hudson noted on twitter that this might not work:
U+20B9 is script 'Common'. So it *might* get rolled into glyph runs with adjacent Devanagaru numerals, but I've not tested.
Since that failed I tried using CALT to substitute the Devanagari Indian Rupee Symbol when it is followed by devangari figures (with the Deva figures in a class). This doesn’t work either. As soon as I enter a Devanagari figure CALT is disabled. If I turn CALT back on the substitution works, but only if I use the default composition engine. Changing to the world-ready composer breaks the substitution. Illustrator behaves the same way. Photoshop won’t sub in the alternate Rupee at all. Neither will Chrome.