Media controls (MPRIS, Windows SMTC); stop old tracks when switching

README.md

@@ -14,6 +14,22 @@ A music player with two modes, switched in the header:
 Each mode has its own player, so switching modes doesn't lose your place; starting one pauses
 the other.
 
+## Media controls
+
+SaraTune counts as a media player to the system, so the desktop's media widget, the lock screen
+and media keys (keyboard or Bluetooth headphones) show and control whatever played last, in
+either mode: play/pause, next/previous, seeking, volume, and shuffle/repeat (in Audio mode, repeat
+is the loop button; there's no shuffle).
+
+- Linux: MPRIS on the session bus as `org.mpris.MediaPlayer2.SaraTune` (`Mpris.py`, with
+  `dbus-fast`). Try it with `playerctl -p SaraTune status`.
+- Windows: the System Media Transport Controls (`Smtc.py`, with the `winrt` packages), through a
+  WinRT MediaPlayer whose own command handling is off, since the window belongs to the Flet
+  client's process. Not tested on real Windows yet.
+
+`MediaControls.py` is the shared part. Settings > General can turn it off; if it can't start
+(no session bus, no WinRT), SaraTune plays without it.
+
 ## Where things live
 
 | Path | What |