On Sat, 10 Aug 2019 at 08:29, Richard Wordingham via Unicode <unicode@unicode.org> wrote: > > There are similar issues with Tibetan; some fonts do not work properly > if a vowel below (ccc=132) is separated from the base of the > consonant stack by a vowel above (ccc=130).
It's not that the fonts don't work, it's that some the rendering engines do not apply the OpenType features in the font that support both sequences of vowels (vowel-above followed by vowel-below, and vowel-below followed by vowel-above). Just retested on Windows 10 with a Tibetan font that supports both sequences of vowels, and both sequences display correctly under Harfbuzz (as expected), but only vowel-below followed by vowel-above displays correctly when using built-in Windows rendering. It is very frustrating that Windows cannot correctly support the display of Tibetan in normalized form, yet Harfbuzz does not have any problems. Personally, I think USE is a failed experiment, and I wish Microsoft would simply adopt Harfbuzz as the default rendering engine. Andrew