load the queue around the current track and scroll to it

app/src/main/kotlin/com/subtracks/ui/playback/QueueScreen.kt

@@ -66,6 +66,7 @@ import sh.calvin.reorderable.ReorderableItem
 import sh.calvin.reorderable.rememberReorderableLazyListState
 
 private const val LOAD_THRESHOLD = 5
+private const val OLDER_LOAD = 30
 private const val POSITION_TIMEOUT_MS = 1_000L
 
 data class QueueRow(
@@ -83,6 +84,9 @@ class QueueViewModel(
     var ready by mutableStateOf(false)
         private set
 
+    var initialIndex by mutableStateOf(0)
+        private set
+
     private var nextId = 0L
     private val mutex = Mutex()
     private var size = 0L
@@ -104,11 +108,12 @@ class QueueViewModel(
                         withTimeoutOrNull(POSITION_TIMEOUT_MS) {
                             playbackController.state.first { it.position != null }.position
                         }?.coerceIn(0, size - 1) ?: 0L
-                    val start = cursor
+                    val start = (cursor - OLDER_LOAD).coerceAtLeast(0)
                     val end = (start + QUEUE_CHUNK - 1).coerceAtMost(size - 1)
                     rows.addAll(queueRepository.range(snapshot, start, end).map(::newRow))
                     first = rows.firstOrNull()?.position ?: 0
                     last = rows.lastOrNull()?.position ?: -1
+                    initialIndex = (cursor - first).toInt().coerceAtLeast(0)
                 }
                 ready = true
             }
@@ -254,6 +259,7 @@ fun QueueRoute(
     QueueScreen(
         rows = viewModel.rows,
         ready = viewModel.ready,
+        initialIndex = viewModel.initialIndex,
         currentSongId = playback.item?.id,
         coverArt = sourceRepository::coverArt,
         onBack = onBack,
@@ -284,6 +290,7 @@ fun QueueScreen(
     onLoadNewer: () -> Unit,
     onUndo: () -> Unit,
     modifier: Modifier = Modifier,
+    initialIndex: Int = 0,
 ) {
     val listState = rememberLazyListState()
     val fill = rememberViewportFill(listState)
@@ -299,6 +306,7 @@ fun QueueScreen(
 
     LaunchedEffect(listState, ready) {
         if (!ready) return@LaunchedEffect
+        if (initialIndex > 0) listState.scrollToItem(initialIndex)
         snapshotFlow {
             val info = listState.layoutInfo
             val firstVisible = info.visibleItemsInfo.firstOrNull()?.index ?: -1

app/src/test/kotlin/com/subtracks/ui/playback/QueueViewModelTest.kt

@@ -72,19 +72,20 @@ class QueueViewModelTest {
         viewModel.open()
         await { viewModel.ready }
 
-        assertEquals((100L..159L).toList(), viewModel.rows.map { it.position })
+        assertEquals((70L..129L).toList(), viewModel.rows.map { it.position })
+        assertEquals(30, viewModel.initialIndex)
 
         viewModel.loadNewer()
-        await { viewModel.rows.lastOrNull()?.position == 199L }
+        await { viewModel.rows.lastOrNull()?.position == 189L }
-        assertEquals((100L..199L).toList(), viewModel.rows.map { it.position })
+        assertEquals((70L..189L).toList(), viewModel.rows.map { it.position })
 
         viewModel.loadOlder()
-        await { viewModel.rows.firstOrNull()?.position == 40L }
+        await { viewModel.rows.firstOrNull()?.position == 10L }
-        assertEquals((40L..199L).toList(), viewModel.rows.map { it.position })
+        assertEquals((10L..189L).toList(), viewModel.rows.map { it.position })
     }
 
     @Test
-    fun openingAtTheEndLoadsASingleRowAndExtendsOlder() {
+    fun openingAtTheEndLoadsAWindowAndExtendsOlder() {
         runBlocking { seedSongs(200) }
         controller.playSongs(1, 199)
         await { controller.state.value.position == 199L }
@@ -92,11 +93,12 @@ class QueueViewModelTest {
         viewModel.open()
         await { viewModel.ready }
 
-        assertEquals(listOf(199L), viewModel.rows.map { it.position })
+        assertEquals((169L..199L).toList(), viewModel.rows.map { it.position })
+        assertEquals(30, viewModel.initialIndex)
 
         viewModel.loadOlder()
-        await { viewModel.rows.firstOrNull()?.position == 139L }
+        await { viewModel.rows.firstOrNull()?.position == 109L }
-        assertEquals((139L..199L).toList(), viewModel.rows.map { it.position })
+        assertEquals((109L..199L).toList(), viewModel.rows.map { it.position })
     }
 
     @Test
@@ -118,7 +120,7 @@ class QueueViewModelTest {
         viewModel.reorder(fromIndex = 0, toIndex = 2)
 
         val positions = viewModel.rows.map { it.position }
-        assertEquals(listOf(101L, 102L, 100L), positions.take(3))
+        assertEquals(listOf(71L, 72L, 70L), positions.take(3))
     }
 
     private fun row(position: Int) =