native-theme-qt

Resolve the user's effective Qt 6 widget theme into a versioned JSON snapshot.

The probe constructs a QApplication, allowing Qt to load the configured QPA platform theme and QStyle plugins. It then exports the effective application palette, fonts, icon theme, pixel metrics, style hints, polished defaults for representative controls, and a toolkit-neutral semantic palette.

$ native-theme-qt > qt-theme.json

This is more reliable than parsing only qt6ct.conf: the effective result can also depend on the desktop platform-theme plugin, QT_STYLE_OVERRIDE, a style plugin such as Breeze or Kvantum, QSS, and toolkit defaults.

Process model

probe() creates a QApplication and must run on the main thread. A GPUI, iced, or other non-Qt application should normally execute the CLI in a subprocess and deserialize its output. This keeps toolkit-global state and event loops isolated.

GPUI integration

Enable the optional bridge to the existing native-theme-gpui crate:

native-theme-qt = { version = "0.1", features = ["gpui"] }

Keep the probe in a subprocess, deserialize its snapshot, and build a complete gpui-component theme:

let snapshot: native_theme_qt::ThemeSnapshot =
    serde_json::from_slice(&probe_output.stdout)?;
let theme: gpui_component::theme::Theme = snapshot.to_gpui_theme()?;

// During GPUI application setup, after gpui_component::init(cx):
cx.set_global(theme);

resolve_native_theme() exposes the intermediate native_theme::ResolvedTheme when an application needs it. The Qt values are merged over native-theme's Breeze preset, which supplies fields Qt does not expose through its public theme API. Call snapshot.validate() after deserializing snapshots received from any source other than this crate's probe.

The first snapshot version exports palette brushes and metrics. Arbitrary Qt brushes and SVG-driven style plugins may require a later render-atlas extension for pixel-perfect reproduction.

Development

nix develop
cargo test
cargo run

The integration suite uses Qt's offscreen QPA backend, so it does not require a running display server:

cargo test

The Nix shell also includes qt6ct. Its real platform-theme plugin and an isolated custom-palette fixture are covered with:

NATIVE_THEME_RUN_QT6CT_TESTS=1 cargo test --test cli

./scripts/check is the same format, test, strict Clippy, and rustdoc gate used by CI.