Fallback fonts

[toonn]

Is your feature request related to a problem? Please describe.
Sometimes the font you prefer doesn't quite cover all the characters you commonly encounter.

Describe the solution you'd like
Other applications seem to fall back to whichever is the next font to contain a missing glyph. It seems like kitty may not (yet?), hence the feature request.

Is this inherent to kitty's handling of fonts or is there an issue like both fonts would need to be the exact same width or something? Any ways I can troubleshoot why it's not working in my particular case? (It involves emoji so I don't 100% expect it to work but kitty doesn't seem to have a problem with emoji, just the ones missing from my default emoji font.)

[kovidgoyal]

kitty implements font fallback. If a glyph is missing in a
font, kitty will query the system to find an alternate font for it. In
addition, if you dont like the default font kitty finds, you can specify
you own via symbol_map in kitty.conf.

https://sw.kovidgoyal.net/kitty/conf.html#opt-kitty.symbol_map

Finally, you can check what fallbacks kitty is using with
--debug-font-fallback

[toonn]

Thanks. My system seems to select the wrong font. Kitty reports the font doesn't actually contain the glyph. So you're saying it's not kitty's but the system's responsibility to suggest the proper font?

[kovidgoyal]

Yeah, every application is not supposed to scan every font file on its
own to determine which one has which glyphs. They system is supposed to
maintain a cache of that information, which all applications are
supposed to use.

[toonn]

But why does the system propose the correct font to other applications. Just not kitty?

[kovidgoyal]

No clue, it would help if you gave some more details about what the
problem is you are having exactly.

[toonn]

🥵 isn't in my "Apple Color Emoji" font. (I'm stuck on OSX 10.13.6.) I've installed Joypixels to use as a fallback and other applications render its glyph just fine. Kitty's the only one I've noticed that renders it as a wide dash "—". I expect this would happen with at least some other fonts as well.

[kovidgoyal]

Aah, you are on macOS. On macOS kitty hardcodes AppleColorEmoji for
emoji since that is the standard font. I suppose I can add a check to
see if it has the emoji and use a fallback if not.

[vpeopleonatank]

kitty implements font fallback. If a glyph is missing in a
font, kitty will query the system to find an alternate font for it. In
addition, if you dont like the default font kitty finds, you can specify
you own via symbol_map in kitty.conf.

https://sw.kovidgoyal.net/kitty/conf.html#opt-kitty.symbol_map

Finally, you can check what fallbacks kitty is using with
--debug-font-fallback

Can I specify what font fallback kitty use? Because my main font in config is JetBrainMono, It doesn't have some glyps (from patched nerd fonts), sometimes system correctly "choose" my installed Dejavu Nerd font, then it show icon correctly but now system doesn't choose right font (currently check --debug-font-fallback It show JetBrainMono)

[pinpox]

Can I specify what font fallback kitty use?

Same issue here. I use an unpatched font and would like to specify the fallback font which will be used for things like emoji or symbols.

[Luflosi]

See https://sw.kovidgoyal.net/kitty/conf/#opt-kitty.symbol_map.

[jakwings]

Same issues here. But symbol_map is not ideal until I find or make a program to batch generate the maps based on my fallback list. symbol_map will fallback to the placeholder ⯑ instead of a system provided one. I need thousands of glyphs spanning various fonts, especially CJK fonts, Symbola and B&W emojis. A big headache.

Ideally the symbol maps should be calculated and cached by kitty (maybe asynchronously in a background process) every time the listed fonts are updated (infrequently).