Mark-to-mark attachment is not working for Myanmar font builds

The Myanmar font builds were okay at 3.2-3231. But from 3.2-3232, the mkmk feature is not working as expected.

Test: ငှ့ ငု့

Problem: the dotbelow does not attach to all of the below marks.

mkmk produced in 3231:

mkmk produced in 3234, a difference here is the use of UseMarkFilteringSet:

CC: @Bendy

Thanks Sovichet! I was Zooming with Georg about this in October. The problem is the lookupflag. It needs to restrict the context using UseMarkFilteringSet @belowmarks. Without the lookupflag, as in the first example, any abovemark in between the two belowmarks will break the mkmk attachment. The second example looks like the lookup is restricted to just the dotbelow glyph, so the rules trying to attach it to other belowmarks won’t have any effect.

Related: Skip unhandled marks in ‘mkmk’

i wonder if anyone can respond. We haven’t been able to export any Burmese fonts correctly for a month and need this to be fixed please

Can you call me to show what is not working?

Yep, I can Skype tomorrow. Currently none of the mkmk is working at all, as far as I can tell. The lookupflag UseMarkFilteringSet is incorrect

This is fixed in version 3241.