Trigger color mode change following darkmode or alike in macos

[mad01]

Is your feature request related to a problem? Please describe.
In Today's operating systems like macos there is features that allows you to set darkmode at the evening and lightmode at the day, for me that means having a light and a dark theme. from what i have found i don't see a way to do this.

Describe the solution you'd like
Since the way different operating systems works i think one of the options i like is to allow for a background task or ticker. like you can have in vim with a ticker triggering every N sec. this you could then trigger colour theme change for example.

i have a smaller shell script for kitty to handle this looking like this but i use the same logic to conditional change for vim since it's the same macos defaults key

function darkModeSetKitty() {
    if $(defaults read -g AppleInterfaceStyle &>/dev/null) ; then
        # if ok it set dark since AppleInterfaceStyle is unset during the day
        kitty @ set-colors -a "~/.config/kitty/onehalf-dark.conf"
    else
        # set to light as default 
        kitty @ set-colors -a "~/.config/kitty/onehalf-light.conf"
    fi
}

function darkModeVim() {
    if $(defaults read -g AppleInterfaceStyle &>/dev/null) ; then
        # if ok it return string 
        echo "Dark"
    else
        # on err it will fail and we should return light
        echo "Light"
    fi
}

the optimal option would be to have OS specific implementations but that does not have to be the initial option to allow users to solve it

[wez]

There are some details on how to do this in this thread:
https://twitter.com/fanzeyi/status/1372054462534062084
we should get this added to the docs as a config recipe/example

[rashil2000]

Hey!

So I was trying something similar for Windows theme detection, the relevant code is relatively simple:

function compute_scheme()
  local success, stdout, stderr = wezterm.run_child_process({"reg", "query", "HKCU\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize", "/v", "AppsUseLightTheme"})
  local is_light = tonumber(wezterm.truncate_left(wezterm.split_by_newlines(stdout)[3],1))
  if is_light == 0 then
    return "BlulocoDark";
  end
  return "BlulocoLight";
end

This correctly returns the value, but for some reason the theme doesn't actually change unless wezterm is restarted. Here is my config:

local wezterm = require 'wezterm';

function compute_scheme()
  local success, stdout, stderr = wezterm.run_child_process({"reg", "query", "HKCU\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize", "/v", "AppsUseLightTheme"})
  local is_light = tonumber(wezterm.truncate_left(wezterm.split_by_newlines(stdout)[3],1))
  if is_light == 0 then
    return "BlulocoDark";
  end
  return "BlulocoLight";
end

wezterm.on("update-right-status", function(window, pane)
  local overrides = window:get_config_overrides() or {}
  local color_scheme = compute_scheme()
  if overrides.color_scheme ~= color_scheme then
    overrides.color_scheme = color_scheme
    window:set_config_overrides(overrides)
  end
end)

return {
  launch_menu = {
    { label = "PowerShell", args = {"pwsh"} },
    { label = "Cmd", args = {"cmd"} },
    { label = "Bash", args = {"bash"} },
    { label = "Neovim", args = {"nvim"} },
  },

  window_padding = {
    left = 25,
    right = 25,
    top = 25,
    bottom = 25,
  },
  initial_cols = 90,
  initial_rows = 30,
  hide_tab_bar_if_only_one_tab = true,
  add_wsl_distributions_to_launch_menu = false,
  font = wezterm.font("RecMonoSemicasual NF", {weight="Medium"}),
  color_scheme = compute_scheme(),
  default_prog = {"pwsh"},
  font_size = 11.0,

  colors = {
    tab_bar = {
      background = "#F9F9F9",
      active_tab = {
        bg_color = "#F9F9F9",
        fg_color = "#000000",
        intensity = "Bold",
        underline = "Single",
      },
      inactive_tab = {
        bg_color = "#F0F0F0",
        fg_color = "#808080",
      },
      inactive_tab_hover = {
        bg_color = "#E4E4E4",
        fg_color = "#808080",
        italic = true,
      }
    }
  }
}

What am I doing wrong here?

[wez]

This config switches the color scheme based on the appearance:

local wezterm = require 'wezterm'

function scheme_for_appearance(appearance)
  if appearance:find("Dark") then
    return "Builtin Solarized Dark"
  else
    return "Builtin Solarized Light"
  end
end

wezterm.on("window-config-reloaded", function(window, pane)
  local overrides = window:get_config_overrides() or {}
  local appearance = window:get_appearance()
  local scheme = scheme_for_appearance(appearance)
  if overrides.color_scheme ~= scheme then
    overrides.color_scheme = scheme
    window:set_config_overrides(overrides)
  end
end)

return {
}

The get_appearance method is currently only hooked up on macos and X11.
If you want to make it work on windows, then we need to add something like:

   fn get_appearance(&self) -> Appearance {
         if let Ok(1) = read_theme() {
            Appearance::Light
         } else {
            Appearance::Dark
         }
   }

in here: https://github.com/wez/wezterm/blob/main/window/src/os/windows/connection.rs#L25

I'll look at this a bit later today, but if you wanted to submit a PR for this before I get to it, go for it!

[rashil2000]

Sorry, I won't be able to as I'm caught up with some work today.

But I have a question: is the window:set_config_overrides(overrides) function also hooked up only on macOS and X11 currently?
Because there might be conditions other than current appearance (which you demonstrated through get_appearance) where someone would want to change the colorscheme (for example based on some registry key like in my config - basically I was trying to follow what you replied in the tweet above, but adapted to Windows).

[wez]

The only thing that wasn't hooked up on windows was the window:get_appearance() method, but I just pushed a commit that does that.

window:set_config_overrides is implemented and behaves the same way on all systems.

You can use other criteria than the system appearance to influence the config overrides. There are some examples in the docs, and there's an example of using the update right status hook as a timer to do something that might depend on the current time.

[wez]

Docs are up at https://wezfurlong.org/wezterm/config/lua/window/get_appearance.html
Enjoy!

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