fix resuming video playback after background audio only mode.

src-tauri/android/src/main/java/com/dtourolle/jellytau/player/JellyTauPlaybackService.kt

@@ -187,6 +187,9 @@ class JellyTauPlaybackService : MediaSessionService() {
 
                 override fun onSeekTo(position: Long) {
                     android.util.Log.d("JellyTauPlaybackService", "Lock screen: Seek to $position")
+                    // The scrubber is absolute; Rust owns the seek in absolute terms
+                    // (in a background-audio handoff it rebuilds the stream at this
+                    // StartTimeTicks). Send the absolute position as-is.
                     val positionSeconds = position / 1000.0
                     nativeOnMediaCommand("seek:$positionSeconds")
                 }
@@ -259,6 +262,25 @@ class JellyTauPlaybackService : MediaSessionService() {
     private var lastArtist: String = ""
     private var lastIsPlaying: Boolean = false
 
+    // Base offset (ms) added to every position reported to the lockscreen
+    // MediaSession. During a background-audio handoff the audio stream is
+    // requested with StartTimeTicks = the handoff point, so ExoPlayer reports
+    // position RELATIVE to that point (starting at 0). The metadata duration,
+    // however, is the full absolute length — so without this base the scrubber
+    // thumb sits near 0:00 on a full-length bar. Set from the known handoff
+    // position via setPositionOffset(); 0 for normal playback.
+    private var positionOffsetMs: Long = 0L
+
+    /**
+     * Set the base position offset (seconds) applied to lockscreen positions.
+     * Called by the native layer when entering/exiting a background-audio handoff.
+     * Pass 0 to clear (normal playback, where ExoPlayer's position is absolute).
+     */
+    fun setPositionOffset(offsetSeconds: Double) {
+        positionOffsetMs = (offsetSeconds * 1000.0).toLong().coerceAtLeast(0L)
+        android.util.Log.d("JellyTauPlaybackService", "Position offset set to ${positionOffsetMs}ms")
+    }
+
     /**
      * Update the MediaSession metadata and playback state, plus the notification.
      *
@@ -292,8 +314,8 @@ class JellyTauPlaybackService : MediaSessionService() {
 
         session.setMetadata(metadataBuilder.build())
 
-        // Update MediaSession playback state
-        session.setPlaybackState(buildPlaybackState(isPlaying, position))
+        // Update MediaSession playback state (position made absolute via the base offset).
+        session.setPlaybackState(buildPlaybackState(isPlaying, position + positionOffsetMs))
 
         // While casting, re-assert the remote volume provider. Metadata pushes
         // arrive on the session poller thread and can race with (or arrive
@@ -322,7 +344,8 @@ class JellyTauPlaybackService : MediaSessionService() {
         val session = mediaSessionCompat ?: return
         val notificationStateChanged = isPlaying != lastIsPlaying
         lastIsPlaying = isPlaying
-        session.setPlaybackState(buildPlaybackState(isPlaying, position))
+        // Absolute position for the scrubber = relative ExoPlayer position + base offset.
+        session.setPlaybackState(buildPlaybackState(isPlaying, position + positionOffsetMs))
         // Only rebuild the notification when the play/pause icon actually flips.
         if (notificationStateChanged) {
             updateNotification(lastTitle, lastArtist, isPlaying)