I'm using kitty myself (currently
pkg-lock(8)ed version kitty-0.48.2_3, because of linux dependencies). As far as I can tell,
graphics/linux-slang (which pulls in
emulators/linux-rl9, is only necessary when using custom shaders:
https://sw.kovidgoyal.net/kitty/build/ .
Build from source
...
Dependencies
These dependencies are needed when building against system libraries only.
Run-time dependencies:
...
shader-slang (needed only if you use custom shaders)
Why TF does a terminal emulator need a package to make shader language easier?
It seems for visual effects :
https://sw.kovidgoyal.net/kitty/custom-shaders/
Quote:
Cursor trails:
Motion Blur - Make the cursor trail glide smoothly, like a fast moving object caught on camera.
Blaze - Set your cursor on fire as it moves around
Lightning - Make your cursor shoot lightning as it moves around (Seriously?)
Wait, it gets better:
Water - Pretend you are cool enough to code underwater.
Animated backgrounds: Inside The Matrix, Northern Lights, Fireworks, etc. /Quote
Those are truly very necessary features for sure in a terminal emulator.
Someone should open a PR or contact the kitty maintainer and ask for a port configure option. Maybe I do it. The option should be disabled by default.