Feature Request: Auto-Detect Terminal Background for Theme Variant Selection

[claudio4]

Many Neovim themes (like Catppuccin and TokyoNight) already auto-switch between light and dark variants based on whether vim.o.background reports a light or dark terminal background.

This is an incredibly convenient feature for users who:

• Match their system's light/dark mode to time of day.
• SSH into different machines with varied terminal settings.

It would be nice also have this ability in onedarkpro. As I understand it #305 and #306 posibilítate this but it will still be nice to have it out of the box.

BTW, #305 makes usage of AutoCmd but it looks like Catppuccin and TokyoNight just use vim.o.background. To my knowledge this can be done because plugins load after VimEnter event, and that's where Neovim populates vim.o.background.

[olimorris]

I think it's a great idea and I'm not aware that those themes had that functionality. I achieve this in my own dotfiles through a somewhat clunky method so would be very keen if you could share how those theme's are facilitating this.

[claudio4]

As far as I know, Catppuccin just do a simple look-up in a table to determine the theme variant to use given the vim.o.background. Relevant code here. Extracts taken from that same file.

--- The if ensures that the automatic behavior only changes the flavor if it does not match the curren background.
if default and default == M.flavour and vim.o.background ~= (M.flavour == "latte" and "light" or "dark") then
	flavour = M.options.background[vim.o.background]
else
	flavour = default
end

-- Where M.options.background is by default
background = {
	light = "latte",
	dark = "mocha",
}

The TokyoNight implementation also looks quite straight forward given their init.lua

function M.load(opts)
  opts = require("tokyonight.config").extend(opts)
  local bg = vim.o.background
  local style_bg = opts.style == "day" and "light" or "dark"

  if bg ~= style_bg then
    if vim.g.colors_name == "tokyonight-" .. opts.style then
      opts.style = bg == "light" and (M.styles.light or "day") or (M.styles.dark or "moon")
    else
      vim.o.background = style_bg
    end
  end
  M.styles[vim.o.background] = opts.style
  return require("tokyonight.theme").setup(opts)
end

[olimorris]

Still not clear how they listen for changes in the background...or maybe they don't. In which case, the example I provide in the docs is valid:

function ToggleTheme()
  if vim.o.background == "dark" then
    vim.cmd("colorscheme onelight")
  else
    vim.cmd("colorscheme onedark")
  end
end

[claudio4]

Sorry for the delayed answer, I was on vacation and didn't have a PC.

Indeed, they do not listen for changes. I now realize that my wording make it look like that was the case. For that I apologize. What I was proposing was way simpler. What I am asking for is to have a colorscheme option that automatically decides at startup if it should use the dark or light variant of the theme.