PlayerController only ran the UI-state copy on Media3 Player.Events
callbacks (track change, pause/play, buffer state) - none of which
fire on normal position advancement during playback. The seek bar
appeared to update every 20-30 seconds, whenever a buffer event
happened to fire, instead of ticking smoothly.
Adds a startPositionPolling() coroutine launched on
Dispatchers.Main.immediate after the controller is connected.
Samples controller.currentPosition + bufferedPosition every 500ms
while isPlaying; skips state updates while paused (positionMs stays
at the last value, which is the correct paused-state behavior).
The poll patches only the position fields via .copy() so stale
event-driven snapshots can't clobber the latest state.
Cadence reference: Flutter via just_audio positionStream runs at
~200ms (audio_handler.dart:75); Spotify / Apple Music sit around
250-500ms in-app. 500ms is the battery-friendly middle ground that
still reads as smooth on a slider. Lock-screen / notification
surfaces are driven by Media3's MediaSession separately and don't
need this poll.
bvandeusen
7b619152ab