Add .visible versions of the four tone marks and switch the encoding to make them the default. Then add an OT lookup to switch those to the normal versions prior to other processing. This would allow for easier editing of raw text in some apps and also accommodate any systems that look to see if a glyph has an outline before handling it properly.
Add .visible versions of the four tone marks and switch the encoding to make them the default. Then add an OT lookup to switch those to the normal versions prior to other processing. This would allow for easier editing of raw text in some apps and also accommodate any systems that look to see if a glyph has an outline before handling it properly.