noctalia-cosmic-theme

Keeps the COSMIC desktop theme in sync with your active Noctalia palette — so COSMIC's native apps (Files, Settings, Terminal, Store, the panel and applets) match everything else Noctalia themes (GTK, Qt, KDE, kitty, …).

Noctalia ships templates for GTK/Qt/KDE but not COSMIC. This bridges the gap using COSMIC's own cosmic-settings appearance import, which compiles and hot-applies a theme RON.

How it works

Noctalia palette change  (builtin / community / custom / wallpaper)
        │  Noctalia rewrites ~/.config/gtk-{3,4}.0/noctalia.css last, once the
        ▼  palette is fully resolved — that's the trigger.
cosmic-noctalia-sync.path  →  cosmic-noctalia-sync.service
        │  waits for the GTK CSS mtime to go quiet, then:
        ▼
resolve-palette.sh   active palette → normalized Material-3 tokens
        ▼               (custom/community palette JSON, else the live GTK4 render)
build-ron.py         → a COSMIC theme RON
        ▼
cosmic-settings appearance import   → COSMIC recompiles + applies live

Works for every Noctalia palette source. Custom and community palettes are read straight from their M3 JSON; builtin and wallpaper-generated schemes are read back from the GTK4 file Noctalia renders for them (it exposes primary, error, surface, on_surface, surface_container, plus success / warning used as secondary / tertiary). The watcher keys on that GTK file precisely because it is written after the switch settles — keying on settings.toml raced ahead of the colours and left non-custom schemes a switch behind.

Palette mapping

COSMIC	← Noctalia M3
bg_color, neutral_0/1	surface
primary_container_bg	surface_container (derived if absent)
secondary_container_bg	surface_container_high
neutral ramp 2..9	interpolated surface → surface_variant → outline → on_surface
neutral_10, text_tint	on_surface
accent, success	primary
neutral_tint	outline
destructive	error
warning	tertiary

Layout (spacing, corner_radii, alpha_map, frosting) stays at COSMIC defaults.

Install

git clone <this repo> ~/Projects/noctalia-cosmic-theme
cd ~/Projects/noctalia-cosmic-theme

# one-off apply
./noctalia-cosmic-sync

# auto-sync on every palette change
cp systemd/cosmic-noctalia-sync.{service,path} ~/.config/systemd/user/
systemctl --user daemon-reload
systemctl --user enable --now cosmic-noctalia-sync.path

For the auto-sync to catch builtin / wallpaper schemes, keep Noctalia's GTK 3 and GTK 4 templates enabled (Settings → Theme → Templates, or builtin_ids = [ …, "gtk3", "gtk4" ] in config.toml).

Adjust the %h/Projects/noctalia-cosmic-theme path in the .service if you cloned elsewhere.

Requires

cosmic-settings (COSMIC 1.7+), python3, noctalia.

Native Noctalia template (experimental)

template.toml + cosmic.env + apply.sh are a Noctalia community-template package for the day Noctalia's user/community template engine reliably fires on palette change (it didn't in 5.0.0-beta.9 — hence the watcher above). Drop the dir into Noctalia's template path and add "cosmic" to your enabled templates.