According to UTN #11, p. 33, the sequence U+1063, U+103A is used as a tone mark in Sgaw Karen, but HarfBuzz displays it as a dotted circle. For example, try the sequence 1014,1062,1063,103A (NA + SGAW KAREN EU-MATRA + TONE MARK SGAW KAREN HATHI + ASAT) which according to UTN #11, p. 34, is valid Myanmar text.
commit d2da5e0b4b4ffc1722403ffb90b8777cfa1cd174 Author: Behdad Esfahbod <behdad@behdad.org> Date: Mon Nov 25 17:50:07 2013 -0500 [myanmar] Relax pwo-tone group a bit This is broken sequence according to OpenType spec, Uniscribe, and current HarfBuzz implementation. But Roozbeh says this is a valid sequence, so allow it. There are multiple "(DB As?)?" constructs in the grammar, but Roozbeh thinks only this one needs changing. Test case: 1014,1063,103A Fixes https://bugs.freedesktop.org/show_bug.cgi?id=71949
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