Appearance

Reading the colour scheme

from uda import Uda

with Uda() as uda:
    print(uda.theme)          # 'dark' | 'light' | 'unknown'

const { Uda } = require('./uda');
console.log(new Uda().theme);

let mode = uda_platform_linux::LinuxAppearanceManager::new().detect_theme()?;

'unknown' is a legitimate answer: a compositor with no colour-scheme concept (a bare window manager, some Wayland tilers) genuinely cannot tell, and guessing would be worse. Treat it as “cannot tell” and let the user choose.

Reading the accent colour

color = uda.accent_color      # (r, g, b, a) or None

The four channels are written into a caller-supplied buffer, and a platform with no system-wide accent concept (KDE, XFCE, most Wayland tilers) leaves the slot untouched and still returns success. A zeroed slot therefore means “no accent”, which is not an error — check the returned status only for hard failures.

Following the system

UDA does not provide a change listener; the read is a snapshot. To follow the user’s choice, poll detect_theme at a sensible interval:

import time
from uda import Uda

with Uda() as uda:
    last = None
    while True:
        theme = uda.theme
        if theme != last:
            apply_theme(theme)
            last = theme
        time.sleep(1.0)

If your toolkit already handles theme changes, prefer its own signal — a UI framework that emits a theme-changed event is both cheaper and more accurate than polling.

Per-desktop behaviour

Desktop	Source	Notes
GNOME 42+	`org.freedesktop.portal.Settings`	the modern standard answer
KDE Plasma 5 / 6	`org.freedesktop.portal.Settings` → `kreadconfig6` / `kreadconfig5` reading `Colors:Scheme`	full support
XFCE	`xfconf-query -c xsettings -p /Net/ThemeName`	no system-wide scheme; often answers `unknown`
Hyprland / Sway	GSettings	tiling composers rarely publish a scheme
Windows 10 / 11	Registry `AppsUseLightTheme`	full support, including live changes

Note that the accent colour is a separate query from the colour scheme, with its own support profile:

Platform	Accent colour
Windows	✅ registry `HKCU\...\DWM\AccentColor`, unpacked to RGBA
GNOME	✅ `gsettings get org.gnome.desktop.interface accent-color`
KDE / XFCE	best-effort; returns `None` when absent
Wayland tilers	❌ no system-wide accent concept

The capability bit Capability::DETECT_THEME says whether any source answered. Capability::FOLLOW_SYSTEM_THEME is defined in the flag set but is not currently set by any backend, because no backend publishes change events yet; do not gate a “follow system” toggle on it.

Design note

Reading the colour scheme is a read-only, side-effect-free query with no D-Bus write, so a UI can call it freely — on startup, on every window shown, or on every signal. It never modifies the desktop’s own theme; it only observes.