fastframe-now-playing

The desktop’s media controls for an egui app. The app says what is playing, artwork included, and the desktop shows it where people look for it:

• Linux: MPRIS, which the panel’s player widget, the lock screen, playerctl and KDE Connect read.
• Windows: the media overlay (the System Media Transport Controls), with the cover, which outlives the app’s window closing to the tray.
• macOS: the Now Playing panel and Control Centre.

The keyboard’s media keys, a headset’s buttons and those panels send commands back: play, pause, play/pause, stop, next, previous, seek by or to a position, volume, shuffle, repeat, open a URI, raise the window, quit.

It came out of Spotifast, which had all three platforms, with the extra track details and per-moment controls Solco publishes.

Usage

use fastframe_now_playing::{App, Command, NowPlaying, Playback, State, Track};

// On the main thread: macOS delivers the controls' events there.
let mut app = App::new("example", "Example");
app.uri_schemes = vec!["example".into()];
let mut controls = NowPlaying::start(app, move || waker.wake());

// Every frame, or whenever something changes:
for command in controls.commands() {
    match command {
        Command::PlayPause => player.toggle(),
        Command::SeekBy(ms) => player.seek_by(ms),
        Command::Raise => show_window(),
        _ => {}
    }
}
controls.update(State {
    playback: Playback::Playing,
    position: player.position(),
    track: Some(Track {
        id: track.id.clone(),
        title: track.title.clone(),
        artists: track.artists.clone(),
        album: track.album.clone(),
        duration: Some(track.duration),
        art_file: art_cache.file_for(&track), // the cover, on disk
        ..Track::default()
    }),
    volume: Some(player.volume()),
    ..State::default()
});
// After a seek, so clients jump rather than glide:
controls.seeked(player.position());

update is cheap to call every frame: a change goes out at once, and the position alone at most once a second while playing, since every client interpolates between updates. The controls run on a thread of their own, so a slow or missing session bus never holds up audio or the window.

Artwork

Give the cover as art_file, an image on disk. Every platform shows it. Windows and macOS show only a file: they load the image themselves, and macOS aborts the process when a remote image it was handed fails to load. art_url is the cover’s web address, which MPRIS shows while the file is not there yet; set art_file when it lands and the controls update.

What each platform shows

State::volume, shuffle and repeat are Options: leave them None for an app without them. Controls says what is available at the moment (no next track, nothing to seek in).

Platform notes

• Linux: the player appears as org.mpris.MediaPlayer2.<bus_name>. Inside a Flatpak, the desktop entry is the sandbox’s app id; desktop_entry(own) gives the same name for the window’s app id, so the two always match. The track id a SetPosition names is the app’s own Track::id, whatever its shape.
• Windows: the controls belong to a hidden window on their own thread, with a message loop.
• macOS: start the controls on the main thread. macOS sends the media keys only to the app that played last; claim makes a track remembered from the last run take them before anything plays.