feat: add daemon mode for faster startup …

[rualss]

feat: add daemon mode for faster startup

  Add daemon mode that keeps GTK4 initialized between screenshot
  annotation calls, reducing window creation time from ~250ms to ~25ms.

  Features:
  - `--daemon` flag to start background daemon
  - `--show` flag to send images to running daemon
  - Per-window configuration to avoid race conditions
  - Signal handling (SIGTERM/SIGINT) for graceful shutdown
  - Unix socket IPC with length-prefixed JSON protocol
  - Security: socket permissions 0600, path validation

  Usage:
    satty --daemon &
    satty --show -f /tmp/screenshot.png --fullscreen

[RobertMueller2]

Thank you for picking this up. We'll review the PR when we get a chance, might be in the new year though.

[rualss]

No problem at all. I did it because i was irritated with latency on my pc, now satty shows up instantly after taking screenshots of small areas, and i have a latency around 0.3s when i screenshot my both monitors, and i have a 4k monitor with 1.5 scaling and full hd monitor.

[RobertMueller2]

Thank you for your patience. This is a comprehensive PR so it'll definitely take us a bit longer to review this. Sorry :)

If anyone else (who isn't a maintainer) feels like helping out with a review and test, by all means, please go ahead :)

Just a small thing I thought about at this stage: should we perhaps try something like SATTY_SOCK first before defaulting to the one in this PR? That way, users could decide how to deal with the daemon in e.g. a nested wayland session.

[RobertMueller2]

I've looked through most of it and I'm ok with what I've seen so far. I still need to figure out and test daemon wide vs instance specific configs, that might require a bit more time.

I'm sticking with my remark regarding SATTY_SOCK above. The only thing I'd like to add right now is to use newer version of nix before we merge, but that seems entirely unproblematic.

And finally, just as a heads-up, #376 may clash regarding config use, but maybe I haven't fully understood this yet 😉

[rualss]

Yea, i think it's better to have some way to control the way daemon works with sockets. Also i think it's a good idea to add some random hash to the name of the default socket file to avoid collisions.