How does ghostty get the system light/dark setting on Linux?

[hankertrix]

I run Ghostty in a tiling window manager and don't use a desktop environment, so I'm trying to find the option to set the system light/dark setting.

I tried

gsettings set org.gnome.desktop.interface color-scheme 'prefers-dark'

But it doesn't seem to make a difference, as Ghostty will always default to the light colour scheme regardless of what that value is.

[jcollie]

You'll need to double-check as I'm on mobile now but you need to set window-theme=system in your config.

[hankertrix]

I have done that, but nothing changed. Previously it was set to ghostty, so it should have been the same as having it set to system.

[jcollie]

Ghostty uses a DBus protocol to get the system theme so if your desktop environment does not implement that you may be out of luck (and yes, a tiling WM counts as a desktop environment even if its not a traditional one).

[hankertrix]

Ah I see. Do you know the protocol name, or the dbus command to get the value from the protocol?

I'm using i3wm, not sure if it implements such a protocol.

[jcollie]

Ghostty uses the Freedesktop Settings Portal to listen for theme changes.

ghostty/src/apprt/gtk/App.zig

Lines 1116 to 1134 in 6a1df9f

	fn initDbus(self: *App) void {
	const dbus = c.g_application_get_dbus_connection(@ptrCast(self.app)) orelse {
	log.warn("unable to get dbus connection, not setting up events", .{});
	return;
	};
	_ = c.g_dbus_connection_signal_subscribe(
	dbus,
	null,
	"org.freedesktop.portal.Settings",
	"SettingChanged",
	"/org/freedesktop/portal/desktop",
	"org.freedesktop.appearance",
	c.G_DBUS_SIGNAL_FLAGS_MATCH_ARG0_NAMESPACE,
	&gtkNotifyColorScheme,
	self,
	null,
	);
	}

[hankertrix]

Ohhhh I see. Yeap then I'm out of luck. That's a Wayland-specific protocol that i3 will never provide since it's using X Org, but thanks for the reply!

For anyone looking to read the colour scheme setting manually using this protocol, use the command below, taken from pbek/QOwnNotes#2525:

dbus-send --session --print-reply=literal --reply-timeout=1000 --dest=org.freedesktop.portal.Desktop /org/freedesktop/portal/desktop org.freedesktop.portal.Settings.Read string:'org.freedesktop.appearance' string:'color-scheme'

[jcollie]

It's definitely not Wayland-specific, it works just fine on Gnome/X11 and KDE/X11. You're right though that i3 may not provide support for that protocol.

[hankertrix]

Ahhh I see. Looks like I confused portals with Wayland protocols when it’s for Flatpaks.

Looks like I just need to install an implementation of xdg-desktop-portal and start the daemon to get the themes working.

[hankertrix]

For anyone trying to figure out how to get xdg-desktop-portal set up to have light and dark themes working, especially if you are using a tiling window manager or the like that doesn't have a default portal implementation, here's how to do so:

1. Install xdg-desktop-portal and a xdg-desktop-portal-impl. As a generic fallback implementation for most tiling window managers, you should use xdg-desktop-portal-gtk. If you use a desktop environment, like GNOME or KDE, then install the portal for your desktop environment, like xdg-desktop-portal-gnome for GNOME and xdg-desktop-portal-kde for KDE.
2. By default, the portal that you install will only be applied if you have the same XDG_CURRENT_DESKTOP value as the portal implementation that you install. For xdg-desktop-portal-gtk, the value is gtk, so if you are on i3, or qtile, or awesomewm, or any other tiling window manager for that matter, the portal implementation will not be used by default.
3. If you would like to have automatic switching between light and dark themes, install darkman and configure it by creating ~/.config/darkman/config.yaml and entering the values below:

lat: ${your_latitude_as_float}
lng: ${your_longitude_as_float}
usegeoclue: false
dbusserver: true
portal: true

Where ${your_latitude_as_float} and ${your_longitude_as_float} are your location's latitude and longitude as floating point numbers respectively. Note that portal must be set to true to have Ghostty and most other terminals recognise the system theme through darkman's settings portal.

4. Create the ~/.config/xdg-desktop-portal/portals.conf file, or ~/.config/xdg-desktop-portal/${XDG_CURRENT_DESKTOP}-portals.conf, where ${XDG_CURRENT_DESKTOP} is the value when you run echo $XDG_CURRENT_DESKTOP in your shell. The first file will take effect no matter what the value of XDG_CURRENT_DESKTOP is, so you should create the second file if you would like to configure xdg-desktop-portal for only your current window manager or desktop environment and not any other.
5. Enter the values below into the file:

[preferred]
default=gtk
org.freedesktop.impl.portal.Settings=darkman

Change gtk to whichever xdg-desktop-portal-impl you choose to use, like gnome for GNOME and kde for KDE. You can delete the last line if you don't want to use darkman to toggle between the light and dark themes automatically.

6. Enjoy switching between your light and dark themes!