Read the terminal colour scheme on REPL startup

[tecosaur]

Wouldn't it be nice if Julia/the REPL knew what your terminal colours were, and displayed content appropriately?

This introduces light/dark theme detection, as well as your ANSI 8-colour theme. With this capability, we can avoid accidental low-contrast highlights and related issues that will only become worse as we try to extend the graphical capabilities of the REPL.

Sneak peek:

Query durations

• initial query on a local machine: ~0.1s (which I suspect is due to other work that gets scheduled before the response is read)
• subsequent queries on a local machine: <0.01s
• initial query over SSH (100ms latency): ~0.3s

Important

This is asynchronous, and does not impact startup latency

Tested terminals

Test script

using StyledStrings
let (; FACES, SimpleColor, rgbcolor) = StyledStrings  # Grab some private API
    colors = Iterators.flatten((c, Symbol("bright_" * String(c))) for c in
        [:black, :green, :cyan, :blue, :magenta, :red, :yellow, :white])
    println(styled"{bold:    Swatch test  Read  Actual}\n ", '━'^30)
    termfg, termbg = @. SimpleColor(rgbcolor((:foreground, :background)))
    println(styled"     foreground  {(bg=$termfg):  }    {inverse:  }")
    println(styled"     background {light,grey:▕{(bg=$termbg):  }▏  ▕{:  }▏}")
    for color in colors
        termc = SimpleColor(FACES.basecolors[color])
        println(styled" $(lpad(color, 14))  {(bg=$termc):  }    {(bg=$color):  }")
    end
    print(styled"\n {bold:Platform:} {emphasis:$(Sys.KERNEL){grey:/}$(ENV[\"TERM\"])} {grey:(truecolor }")
    println(if Base.ttyhastruecolor() styled"{green,bold:✓}" else styled"{red,bold:✕}" end, styled"{grey:)}")
    println(styled" Do the swatches match?")
end

Everything works

• Linux
  • Kitty
  • Wezterm
  • Foot
  • Ghostty
  • Xterm
  • Alacritty
  • St (Suckless)
  • Ubuntu terminal (Gnome terminal?)
  • Tilix
• Mac
  • Terminal.app
  • iTerm2
  • WezTerm
  • Alacritty
  • Ghostty
  • Kitty
• Windows
  • Windows terminal (it messes up inverse video though)
  • Windows terminal: WSL

Misbehaving (terminal's fault)

• Linux
  • Konsole (lies about values)
• Emacs
  • Eat (doesn't supply colours)
  • Vterm (doesn't report anything)
• Mac
  • iTerm2 + Tmux (doesn't report anything)
• Windows
  • Wezterm via Ubuntu WSL (doesn't report anything)

Misbehaving (our fault)

• Nothing yet 🙂

[topolarity]

iTerm2 + Tmux (doesn't report anything)

Any issue that we can file upstream? This is a fairly common configuration, esp. since iTerm2 has tmux integration

[tecosaur]

Any issue that we can file upstream? This is a fairly common configuration, esp. since iTerm2 has tmux integration

Potentially, there seem to be a few closed OSC-related issues on tmux's repo. I'm also not 100% on the performance: it might be passing through fg/bg info, in which case as of some recent (unpushed) improvements we will still be able to set pick light/dark appropriately and set fg/bg colours.

Testing tmux locally myself, I see that it does pass through OSC 10 and OSC 11 codes (these are the fg/bg codes):

~$ printf '\e]10;?\e\\'
10;rgb:bbbb/c2c2/cfcf

~$ printf '\e]11;?\e\\'
11;rgb:2424/2727/3030

~$ printf '\e]4;1;?\e\\'

~$

[tecosaur]

I'm not sure what's a good idea to do here in terms of unit testing, since this should be tested against a collection of different terminal emulators.

[jakobjpeters]

Wouldn't it be nice if Julia/the REPL knew what your terminal colours were, and displayed content appropriately?

Yes please!

[tecosaur]

I now plan on getting this merged after #60527, and have adjusted the PR accordingly.

[tecosaur]

Given #61151 and and (my) interest in supporting KKP eventually, it would probably be good to support non-OSC queries too, specifically primary device attributes (DA1: CSI c) and current progressive enhancement status (CSI ? u).

As it is, OSC support lets us query more than just colour: such as clipboard contents (when possible), and OSC 99 support.

[tecosaur]

I think this should be good to go now

[vtjnash]

BTW, there's also a more modern way to do this query now with CSI ? 996 n (which enables live reporting of theme changes and is also better supported in new releases of tmux – though also is implemented in fewer terminal emulators right now)

[tecosaur]

Thanks for raising that, I'll look into it.

[tecosaur]

Looks like it's actually decently supported, according to https://github.com/contour-terminal/contour/blob/master/docs/vt-extensions/color-palette-update-notifications.md