Zawgyi Tonemarks in Latin Script

[Richard Wordingham]

On Wed, 17 Feb 2021 05:40:54 +0000
James Kass via Unicode <unicode at unicode.org> wrote:

> Unable to repro this here.  The string "kး" does not display with the 
> dotted circle.  Tried this on Windows 7 with both BabelPad and 
> LibreOffice.  (And now in the compose panel of Mozilla Thunderbird.)

That is curious.  Which font were you using?

In Word on Windows 10, using the font Myanmar text for the whole
string, in LibreOffice and Firefox on Ubuntu 16.04 (so at least one of
them falls back to HarfBuzz Version 1.2.7), and with the Padauk font
using HarfBuzz Version 2.7.2, I get a dotted circle even for an ASCII
letter plus U+1038 MYANMAR SIGN VISARGA.

Of course, there's no problem with HarfBuzz if one uses the Zawgyi-One
font, which is one of the few to support the sequence <U+1E45,
U+1038>.

> Maybe file a bug with the renderer developer?

They could argue that it's not the sort of sequence that they will
support.  (Am I right in thinking that a Unicode-compliant renderer may
deliberately misrender unsupported sequences?) Unfortunately, the
Unicode technical annexes support the principle of separating a base
character from its marks when the extended script property doesn't
support their combination. (I've already complained to Mark Davis about
this.)  After all, if you want a candrabindu on the Latin letter 'l',
or 'v', or 'y', you use U+0310 COMBINING CANDRABINDU.

Richard.