This demonstrates that:
- the ☺ character in Ubuntu Mono is the correct width
- the ▷ character is not present in Ubuntu Mono at all.
The lists of fonts that "have the problem, and ... do not" seem to be lists of fonts that contain those two characters or not.
So the bug here probably is not with any individual font; it is that monospace fonts fall back to proportional fonts for missing characters, instead of falling back to another monospace font with the desired glyph.
In a terminal, enter:
pango-view --font="Ubuntu Mono 48" --markup --text='<span fallback= "false" >ABC A☺C A▷C</span> '
This demonstrates that:
- the ☺ character in Ubuntu Mono is the correct width
- the ▷ character is not present in Ubuntu Mono at all.
The lists of fonts that "have the problem, and ... do not" seem to be lists of fonts that contain those two characters or not.
So the bug here probably is not with any individual font; it is that monospace fonts fall back to proportional fonts for missing characters, instead of falling back to another monospace font with the desired glyph.