Ligatures: Disable in some circumstances?


I am creating a font for a constructed language which uses ligatures when no intervening vowel is present, i.e. ‘pr’ would be an obligatory ligature.

However, there are instances when vowels are not written, so ‘par’ would be typed/written ‘pr’, but without the ligature.

Is there any way for me to easily disable the ligature in such circumstances? Perhaps with a ‘dead’ key of some sort between the two letters to prevent the ligature?

Many thanks.

The correct way would be to insert a “ZERO WIDTH NON-JOINER” (0x200C).

Or, you actually input the a and remove it with an openType feature.