I have been looking for a flash card program that I could use with Khmer. I ran across one whose developer advised me that Unicode support was being extended and allowed me to test a beta version.

The application -- I won't mention the name knowing how out-of-date "facts" persist long after things have changed -- displayed Unicode characters, but as individual, separate letters.

For instance, typing k j k did not show a normal KA character with a second, subscripted KA, but instead a KAុំ, a plus mark below it, then a second KA. Eg, ក​្​ក

It took my seeing how literally this application interpreted the keystrokes I had entered to get an inkling of why the subscripted consonants don't show up in the Unicode charts.

Am I understanding correctly that it is up to the application to interpret various letter combinations and then to display a different character in the font. So that j followed by a consonant displays a subscripted letter, and so on?

If that's the case, are there open-source rules/algorithms for this substitution?

While I can see how any Unicode font indicates which glyph represents which Unicode character, it's not at all clear to me how the font indicates where the subscripted characters are located nor why fonts from different foundries wouldn't locate these characters differently.

Any information on these matters would be most welcome.

Thanks,

Roger Sperberg