Send SIGWINCH on theme change

[zoriya]

This feature was initially created by iterm to allow apps to update their theme when the terminal's theme changes.

This feature was then adopted by tmux to clear their OSC11 cache. Without this to invalidate their OSC11 cache, they will report the initial theme of the terminal and not the updated one.

[mitchellh]

cc @gpanders @rockorager

This seems reasonable. I converted to a discussion to gather more information because I’m not totally sure yet.

one thing I’m curious about: is this sent on any palette or color change? Terminals don’t really have a notion of a theme.

or are you talking about system them? In that case I don’t see it hurting but we already support more 2031 (I think that’s what it is) for system theme change notification. It doesn’t hurt to also send a signal.

[gpanders]

So if I'm an application author that wants to support color change detection, I can just set up an event handler for any time I receive CSI ? 997 ; 1 n or CSI ? 997 ; 2 n. If all I care about is "light or dark" then I'm done, but if I want to know the RGB colors I can then use OSC 10/11.

[mitchellh]

Doesn't Mode 2031 support this? From the spec:

We may not have implemented this part of the spec!

[rockorager]

My only concern with Ghostty supporting this is that it sends a signal to app developers that SIGWINCH is the "right" way to handle this ("iTerm2, tmux, and now Ghostty all do it, so why not?").

I have this same concern. This risks becoming a defacto "standard" way of reporting theme/color changes.

[mitchellh]

We may not have implemented this part of the spec!

See #2771

[will]

I have this same concern. This risks becoming a defacto "standard" way of reporting theme/color changes.

As the person who asked iterm to add that feature: sorry! I didn't know any better at the time