library: keep the album grid aligned across a paging reload

A scrobble writes albums.playCount/played, which invalidates the album
list's PagingSource. Room then refreshes from anchor - initialLoadSize/2,
and with placeholders off that page is the presented list: LazyPagingItems
index zero becomes the page's first album, so the grid re-groups its rows
and every cover moves by (oldStart - newStart) % 3 columns, while the last
row's width becomes the loaded count % 3 instead of the library size % 3.

Enable placeholders for the album pager so an album's index is its
absolute position, and draw a placeholder cell for an unloaded slot. The
other lists are single column, so a reload re-anchors them by key and they
never shifted.

This only keeps the grid still; the reloads themselves are still
unnecessary and are tracked separately.

app/src/main/kotlin/com/subtracks/data/repo/LibraryRepository.kt

@@ -174,7 +174,7 @@ class LibraryRepository(
         search: String,
         downloaded: Boolean,
     ): Flow<PagingData<Album>> =
-        pager(40) {
+        pager(40, enablePlaceholders = true) {
             val dao = db.libraryDao()
             if (!downloaded) {
                 dao.albumsPaging(albumsDefaultQuery(sourceId, starred.ordinal, search, sort, descending))
@@ -507,10 +507,11 @@ class LibraryRepository(
 
     private fun <T : Any> pager(
         pageSize: Int,
+        enablePlaceholders: Boolean = false,
         source: () -> PagingSource<Int, T>,
     ): Flow<PagingData<T>> =
         Pager(
-            config = PagingConfig(pageSize = pageSize, enablePlaceholders = false),
+            config = PagingConfig(pageSize = pageSize, enablePlaceholders = enablePlaceholders),
             pagingSourceFactory = source,
         ).flow
 }

app/src/main/kotlin/com/subtracks/playback/KnownDurationPlayer.kt

@@ -0,0 +1,30 @@
+package com.subtracks.playback
+
+import androidx.annotation.OptIn
+import androidx.media3.common.ForwardingPlayer
+import androidx.media3.common.Player
+import androidx.media3.common.util.UnstableApi
+
+/**
+ * Reports a track whose duration is known from its metadata as finite rather than live.
+ *
+ * Media3 marks a progressive stream live when the data source reports no length and the extractor
+ * no duration. The app declares a length only for a transcode of a track that has one in a
+ * length-estimable format, so a chunked response stays live for an Opus/Ogg/Vorbis transcode, for
+ * a transcode of a track whose library duration is missing, and for a direct play the server does
+ * not give a Content-Length. A live item makes the media session publish no playback position, so
+ * the notification loses its progress even though the item carries a real duration. The stream is
+ * still not seekable; this only restores the position the session reports.
+ */
+@OptIn(UnstableApi::class)
+internal class KnownDurationPlayer(
+    player: Player,
+) : ForwardingPlayer(player) {
+    override fun isCurrentMediaItemLive(): Boolean = if (declaredDurationMs() != null) false else super.isCurrentMediaItemLive()
+
+    private fun declaredDurationMs(): Long? =
+        currentMediaItem
+            ?.mediaMetadata
+            ?.durationMs
+            ?.takeIf { it > 0 }
+}

app/src/main/kotlin/com/subtracks/playback/PlaybackService.kt

@@ -130,6 +130,7 @@ class PlaybackService : MediaSessionService() {
                 }
             },
         )
+        val player = KnownDurationPlayer(exoPlayer)
         val loader =
             CoverArtBitmapLoader(
                 applicationContext,
@@ -139,7 +140,7 @@ class PlaybackService : MediaSessionService() {
         artworkLoader = loader
         session =
             MediaSession
-                .Builder(this, exoPlayer)
+                .Builder(this, player)
                 .setSessionActivity(
                     PendingIntent.getActivity(
                         this,

app/src/main/kotlin/com/subtracks/ui/library/AlbumsContent.kt

@@ -1,5 +1,6 @@
 package com.subtracks.ui.library
 
+import androidx.compose.foundation.background
 import androidx.compose.foundation.combinedClickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
@@ -15,6 +16,7 @@ import androidx.compose.foundation.lazy.grid.GridItemSpan
 import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
 import androidx.compose.foundation.lazy.grid.rememberLazyGridState
 import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
@@ -43,6 +45,8 @@ import com.subtracks.ui.theme.PrefetchArtworkSeeds
 
 const val ALBUM_COVER_TAG = "album-cover"
 
+const val ALBUM_PLACEHOLDER_TAG = "album-placeholder"
+
 @Composable
 fun AlbumsContent(
     items: LazyPagingItems<Album>,
@@ -117,6 +121,16 @@ fun AlbumsContent(
                                 scrim = true,
                             )
                         }
+                    } else {
+                        Box(
+                            modifier =
+                                Modifier
+                                    .fillMaxWidth()
+                                    .aspectRatio(1f)
+                                    .clip(RoundedCornerShape(2.dp))
+                                    .background(MaterialTheme.colorScheme.surfaceVariant)
+                                    .testTag(ALBUM_PLACEHOLDER_TAG),
+                        )
                     }
                 }
                 item(span = { GridItemSpan(maxLineSpan) }) {

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

@@ -58,7 +58,6 @@ import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.draw.clipToBounds
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.layout.onSizeChanged
@@ -111,6 +110,10 @@ private const val SWIPE_SETTLE_MS = 180
 private const val SWIPE_EDGE_RESISTANCE = 0.3f
 private const val HAND_BACK_TIMEOUT_MS = 750L
 
+// The strip is unclipped, so this spacing is what keeps the neighbours off-screen, and it has to
+// clear the content inset plus a tile's shadow. It doubles as the gap between tiles while dragging.
+private val TILE_GAP = 40.dp
+
 data class NowPlayingArt(
     val id: String?,
     val ref: CoverArtRef?,
@@ -329,6 +332,7 @@ fun NowPlayingScreen(
     val strip = frozenStrip ?: liveStrip
     val canGoNext = strip.getOrNull(2) != null
     val canGoPrevious = strip.getOrNull(0) != null
+    val stridePx = coverWidthPx + with(LocalDensity.current) { TILE_GAP.toPx() }
 
     fun animateSwipe(target: Float) {
         settleJob?.cancel()
@@ -340,7 +344,7 @@ fun NowPlayingScreen(
 
     fun commitSwipe(direction: Int) {
         frozenStrip = rotateStrip(strip, direction)
-        swipeOffsetX += direction * coverWidthPx
+        swipeOffsetX += direction * stridePx
         if (direction > 0) onNext() else onSkipPrevious()
         animateSwipe(0f)
     }
@@ -410,13 +414,14 @@ fun NowPlayingScreen(
                                 .padding(horizontal = 24.dp),
                         horizontalAlignment = Alignment.CenterHorizontally,
                     ) {
+                        // Deliberately unclipped: a tile that fills the width would lose its drop
+                        // shadow. TILE_GAP keeps the neighbours off-screen instead.
                         Box(
                             modifier =
                                 Modifier
                                     .weight(1f)
                                     .fillMaxWidth()
                                     .padding(top = 2.dp)
-                                    .clipToBounds()
                                     .onSizeChanged { coverWidthPx = it.width.toFloat() }
                                     .draggable(
                                         orientation = Orientation.Horizontal,
@@ -428,7 +433,7 @@ fun NowPlayingScreen(
                                                         delta < 0 && !canGoNext -> delta * SWIPE_EDGE_RESISTANCE
                                                         else -> delta
                                                     }
-                                                swipeOffsetX = (swipeOffsetX + resisted).coerceIn(-coverWidthPx, coverWidthPx)
+                                                swipeOffsetX = (swipeOffsetX + resisted).coerceIn(-stridePx, stridePx)
                                             },
                                         onDragStarted = {
                                             dragging = true
@@ -484,7 +489,7 @@ fun NowPlayingScreen(
                                             Modifier
                                                 .fillMaxSize()
                                                 .graphicsLayer {
-                                                    translationX = (index - 1) * coverWidthPx + swipeOffsetX
+                                                    translationX = (index - 1) * stridePx + swipeOffsetX
                                                 }.then(
                                                     when (index) {
                                                         0 -> Modifier.testTag(NOW_PLAYING_PREVIOUS_TAG)

app/src/test/kotlin/com/subtracks/data/repo/LibraryRepositoryTest.kt

@@ -2,6 +2,8 @@ package com.subtracks.data.repo
 
 import android.content.Context
 import android.content.res.Resources
+import androidx.paging.PagingDataEvent
+import androidx.paging.PagingDataPresenter
 import androidx.room3.Room
 import androidx.sqlite.driver.bundled.BundledSQLiteDriver
 import androidx.test.core.app.ApplicationProvider
@@ -9,16 +11,23 @@ import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.subtracks.cancelAndJoinBlocking
 import com.subtracks.data.db.SubtracksDatabase
 import com.subtracks.data.download.ArtworkStore
+import com.subtracks.data.model.Album
 import com.subtracks.data.model.Song
+import com.subtracks.data.prefs.AlbumSort
+import com.subtracks.data.prefs.StarredFilter
 import com.subtracks.data.prefs.fakeUserPreferences
 import com.subtracks.data.source.StarType
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.asCoroutineDispatcher
+import kotlinx.coroutines.cancelAndJoin
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.withContext
 import kotlinx.coroutines.withTimeout
 import okhttp3.OkHttpClient
 import okhttp3.mockwebserver.MockResponse
@@ -32,7 +41,10 @@ import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
 import java.io.File
+import java.util.concurrent.Executors
 import java.util.concurrent.TimeUnit
+import java.util.concurrent.atomic.AtomicInteger
+import kotlin.coroutines.CoroutineContext
 
 @RunWith(AndroidJUnit4::class)
 class LibraryRepositoryTest {
@@ -163,6 +175,75 @@ class LibraryRepositoryTest {
             assertEquals(2L, repository.albumSongOrdinal(sourceId, "al1", "s3"))
         }
 
+    @Test
+    fun theAlbumGridPresentsTheWholeLibraryAndSurvivesAReload() =
+        runBlocking {
+            val sourceId = sourceRepository.addSource("nav", "http://localhost/", "u", "p", false)
+            db.libraryDao().upsertAlbums((0 until 250).map { seedAlbum(sourceId, it) })
+
+            val presenterDispatcher = Executors.newSingleThreadExecutor().asCoroutineDispatcher()
+            val presenter = RecordingPresenter(presenterDispatcher)
+            val job =
+                launch {
+                    repository
+                        .albums(sourceId, AlbumSort.Name, false, StarredFilter.Any, "", false)
+                        .collect { presenter.collectFrom(it) }
+                }
+            try {
+                awaitRefreshes(presenter, 1)
+                assertEquals(250, presented(presenter, presenterDispatcher))
+
+                db.libraryDao().upsertAlbums(listOf(seedAlbum(sourceId, 0).copy(playCount = 1)))
+                awaitRefreshes(presenter, 2)
+
+                assertEquals("a reload must not collapse the grid to one page", 250, presented(presenter, presenterDispatcher))
+            } finally {
+                job.cancelAndJoin()
+                presenterDispatcher.close()
+            }
+        }
+
+    private suspend fun awaitRefreshes(
+        presenter: RecordingPresenter,
+        target: Int,
+    ) {
+        withTimeout(30_000) {
+            while (presenter.refreshes.get() < target) delay(10)
+        }
+    }
+
+    private suspend fun presented(
+        presenter: RecordingPresenter,
+        dispatcher: CoroutineDispatcher,
+    ): Int = withContext(dispatcher) { presenter.size }
+
+    private fun seedAlbum(
+        sourceId: Long,
+        index: Int,
+    ) = Album(
+        sourceId = sourceId,
+        id = "al-" + index.toString().padStart(4, '0'),
+        artistId = "ar1",
+        name = "Album " + index.toString().padStart(4, '0'),
+        albumArtist = "Artist",
+        created = 0,
+        coverArt = null,
+        genre = null,
+        year = null,
+        starred = null,
+        songCount = 1,
+    )
+
+    private class RecordingPresenter(
+        context: CoroutineContext,
+    ) : PagingDataPresenter<Album>(context) {
+        val refreshes = AtomicInteger()
+
+        override suspend fun presentPagingDataEvent(event: PagingDataEvent<Album>) {
+            if (event is PagingDataEvent.Refresh) refreshes.incrementAndGet()
+        }
+    }
+
     private suspend fun withSource(block: suspend (MockWebServer) -> Unit) {
         val server = MockWebServer()
         server.start()

app/src/test/kotlin/com/subtracks/playback/KnownDurationPlayerTest.kt

@@ -0,0 +1,83 @@
+package com.subtracks.playback
+
+import android.os.Looper
+import androidx.annotation.OptIn
+import androidx.media3.common.MediaItem
+import androidx.media3.common.MediaMetadata
+import androidx.media3.common.Player
+import androidx.media3.common.SimpleBasePlayer
+import androidx.media3.common.util.UnstableApi
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@OptIn(UnstableApi::class)
+@RunWith(AndroidJUnit4::class)
+class KnownDurationPlayerTest {
+    private fun player(
+        declaredDurationMs: Long?,
+        live: Boolean = true,
+    ): Player =
+        object : SimpleBasePlayer(Looper.getMainLooper()) {
+            override fun getState(): State {
+                val metadata =
+                    MediaMetadata
+                        .Builder()
+                        .setTitle("Track")
+                        .setDurationMs(declaredDurationMs)
+                        .build()
+                val item =
+                    MediaItemData
+                        .Builder("track")
+                        .setMediaItem(
+                            MediaItem
+                                .Builder()
+                                .setMediaId("s1")
+                                .setMediaMetadata(metadata)
+                                .build(),
+                        ).setDurationUs(PLAYER_DURATION_US)
+                        .setLiveConfiguration(if (live) MediaItem.LiveConfiguration.UNSET else null)
+                        .build()
+                return State
+                    .Builder()
+                    .setPlaylist(listOf(item))
+                    .build()
+            }
+        }
+
+    @Test
+    fun aLiveTrackWithADeclaredDurationIsReportedFinite() {
+        val player = player(declaredDurationMs = 100_000L)
+
+        assertFalse(KnownDurationPlayer(player).isCurrentMediaItemLive())
+    }
+
+    @Test
+    fun aLiveTrackWithoutADeclaredDurationStaysLive() {
+        val player = player(declaredDurationMs = null)
+
+        assertTrue(KnownDurationPlayer(player).isCurrentMediaItemLive())
+    }
+
+    @Test
+    fun aFiniteTrackWithADeclaredDurationStaysFinite() {
+        val player = player(declaredDurationMs = 100_000L, live = false)
+
+        assertFalse(KnownDurationPlayer(player).isCurrentMediaItemLive())
+    }
+
+    @Test
+    fun theWrappedDurationIsThePlayersNotTheMetadata() {
+        val player = player(declaredDurationMs = 100_000L)
+
+        assertEquals(PLAYER_DURATION_MS, KnownDurationPlayer(player).getDuration())
+    }
+
+    private companion object {
+        const val PLAYER_DURATION_MS = 200_000L
+        const val PLAYER_DURATION_US = PLAYER_DURATION_MS * 1000
+    }
+}

app/src/test/kotlin/com/subtracks/ui/AppScreenshotTest.kt

@@ -444,38 +444,31 @@ class AppScreenshotTest {
     }
 
     @Test
-    fun nowPlaying() {
-        composeRule.setContent {
-            SubtracksTheme {
-                NowPlayingScreen(
-                    state = Fixtures.playbackState(),
-                    positionMs = 62_000,
-                    title = "Kid A",
-                    coverArt = CoverArtRef("art-al-kid-a", "test:art-al-kid-a"),
-                    artwork = artworkColorsFromSeed(Color.rgb(120, 80, 200)),
-                    onBack = {},
-                    onQueue = {},
-                    onPlayPause = {},
-                    onNext = {},
-                    onPrevious = {},
-                    onSeek = {},
-                    modifier = Modifier.fillMaxSize(),
-                )
-            }
-        }
-        awaitText("Everything In Its Right Place")
-        composeRule.onRoot().captureRoboImage("src/test/screenshots/now_playing.png")
-    }
+    fun nowPlaying() = nowPlayingShot(Fixtures.playbackState(), "art-al-kid-a", "now_playing.png")
 
     @Test
-    fun nowPlayingModes() {
+    fun nowPlayingModes() =
+        nowPlayingShot(
+            Fixtures.playbackState().copy(shuffle = true, repeat = RepeatMode.One),
+            "art-al-kid-a",
+            "now_playing_modes.png",
+        )
+
+    @Test
+    fun nowPlayingNonSquare() = nowPlayingShot(Fixtures.playbackState(), "art-nonsquare", "now_playing_nonsquare.png")
+
+    private fun nowPlayingShot(
+        state: PlaybackState,
+        coverArtId: String,
+        file: String,
+    ) {
         composeRule.setContent {
             SubtracksTheme {
                 NowPlayingScreen(
-                    state = Fixtures.playbackState().copy(shuffle = true, repeat = RepeatMode.One),
+                    state = state,
                     positionMs = 62_000,
                     title = "Kid A",
-                    coverArt = CoverArtRef("art-al-kid-a", "test:art-al-kid-a"),
+                    coverArt = CoverArtRef(coverArtId, "test:$coverArtId"),
                     artwork = artworkColorsFromSeed(Color.rgb(120, 80, 200)),
                     onBack = {},
                     onQueue = {},
@@ -488,7 +481,7 @@ class AppScreenshotTest {
             }
         }
         awaitText("Everything In Its Right Place")
-        composeRule.onRoot().captureRoboImage("src/test/screenshots/now_playing_modes.png")
+        composeRule.onRoot().captureRoboImage("src/test/screenshots/$file")
     }
 
     @Test
@@ -725,6 +718,7 @@ private object Fixtures {
 
     fun artEngine(): FakeImageLoaderEngine {
         val builder = FakeImageLoaderEngine.Builder()
+        builder.intercept("art-nonsquare", art("art-nonsquare", ArtKind.Album, width = 640, height = 256))
         albums.mapNotNull { it.coverArt }.forEach { builder.intercept(it, art(it, ArtKind.Album)) }
         playlists.mapNotNull { it.coverArt }.forEach { builder.intercept(it, art(it, ArtKind.Playlist)) }
         artists.mapNotNull { it.coverArt }.forEach { builder.intercept(it, art(it, ArtKind.Artist)) }
@@ -734,9 +728,14 @@ private object Fixtures {
     private fun art(
         key: String,
         kind: ArtKind,
+        width: Int = 256,
+        height: Int = 256,
     ): Image {
-        val size = 256
-        val f = size.toFloat()
+        val w = width.toFloat()
+        val h = height.toFloat()
+        val cx = w / 2f
+        val cy = h / 2f
+        val span = maxOf(w, h)
         val random = Random(key.hashCode())
         val base = random.nextFloat() * 360f
 
@@ -752,21 +751,21 @@ private object Fixtures {
                 listOf(color(0f), color(170f + random.nextFloat() * 30f))
             }
 
-        val bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888)
+        val bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
         val canvas = Canvas(bitmap)
         val paint = Paint(Paint.ANTI_ALIAS_FLAG)
         canvas.drawColor(palette[0])
 
         when (kind) {
             ArtKind.Album -> {
-                val stripe = f / 9f
+                val stripe = w / 9f
                 canvas.save()
-                canvas.rotate(-30f, f / 2f, f / 2f)
-                var x = -f
+                canvas.rotate(-30f, cx, cy)
+                var x = -span
                 var index = 1
-                while (x < f * 2f) {
+                while (x < span * 2f) {
                     paint.color = palette[index % palette.size]
-                    canvas.drawRect(x, -f, x + stripe * 0.6f, f * 2f, paint)
+                    canvas.drawRect(x, -span, x + stripe * 0.6f, span * 2f, paint)
                     x += stripe
                     index++
                 }
@@ -774,12 +773,12 @@ private object Fixtures {
             }
 
             ArtKind.Playlist -> {
-                val step = f / 4f
+                val step = w / 4f
                 var row = 1
                 var y = step / 2f
-                while (y < f) {
+                while (y < h) {
                     var x = step / 2f
-                    while (x < f) {
+                    while (x < w) {
                         paint.color = palette[row % palette.size]
                         canvas.drawCircle(x, y, step * 0.3f, paint)
                         x += step
@@ -791,12 +790,12 @@ private object Fixtures {
 
             ArtKind.Artist -> {
                 paint.style = Paint.Style.STROKE
-                paint.strokeWidth = f / 13f
-                var radius = f * 0.5f
+                paint.strokeWidth = span / 13f
+                var radius = span * 0.5f
                 var index = 1
                 while (radius > 0f) {
                     paint.color = palette[index % palette.size]
-                    canvas.drawCircle(f / 2f, f / 2f, radius, paint)
+                    canvas.drawCircle(cx, cy, radius, paint)
                     radius -= paint.strokeWidth
                     index++
                 }

app/src/test/kotlin/com/subtracks/ui/library/AlbumsPlaceholderTest.kt

@@ -0,0 +1,61 @@
+package com.subtracks.ui.library
+
+import androidx.activity.ComponentActivity
+import androidx.compose.runtime.remember
+import androidx.compose.ui.test.junit4.v2.createAndroidComposeRule
+import androidx.compose.ui.test.onAllNodesWithTag
+import androidx.compose.ui.unit.dp
+import androidx.paging.PagingData
+import androidx.paging.compose.collectAsLazyPagingItems
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.github.takahirom.roborazzi.RobolectricDeviceQualifiers
+import com.subtracks.data.model.Album
+import com.subtracks.ui.theme.SubtracksTheme
+import kotlinx.coroutines.flow.flowOf
+import org.junit.Assert.assertEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.annotation.Config
+import org.robolectric.annotation.GraphicsMode
+
+@RunWith(AndroidJUnit4::class)
+@GraphicsMode(GraphicsMode.Mode.NATIVE)
+@Config(qualifiers = RobolectricDeviceQualifiers.PixelXL)
+class AlbumsPlaceholderTest {
+    @get:Rule
+    val composeRule = createAndroidComposeRule<ComponentActivity>()
+
+    @Test
+    fun anUnloadedCellIsDrawnAsAPlaceholder() {
+        composeRule.setContent {
+            SubtracksTheme {
+                val items =
+                    remember { flowOf(PagingData.from(listOf(album(0)), placeholdersAfter = 2)) }
+                        .collectAsLazyPagingItems()
+                AlbumsContent(items, { _, _ -> null }, 0.dp, {})
+            }
+        }
+        composeRule.waitUntil(timeoutMillis = 5_000) {
+            composeRule.onAllNodesWithTag(ALBUM_PLACEHOLDER_TAG).fetchSemanticsNodes().isNotEmpty()
+        }
+
+        assertEquals(2, composeRule.onAllNodesWithTag(ALBUM_PLACEHOLDER_TAG).fetchSemanticsNodes().size)
+        assertEquals(1, composeRule.onAllNodesWithTag(ALBUM_COVER_TAG).fetchSemanticsNodes().size)
+    }
+
+    private fun album(index: Int) =
+        Album(
+            sourceId = 1,
+            id = "al-" + index.toString().padStart(4, '0'),
+            artistId = "ar",
+            name = "Album " + index.toString().padStart(4, '0'),
+            albumArtist = "Artist",
+            created = 0,
+            coverArt = null,
+            genre = null,
+            year = null,
+            starred = null,
+            songCount = 1,
+        )
+}

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

@@ -4,6 +4,7 @@ import androidx.activity.ComponentActivity
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.test.assertHeightIsAtLeast
 import androidx.compose.ui.test.assertHeightIsEqualTo
+import androidx.compose.ui.test.assertIsNotDisplayed
 import androidx.compose.ui.test.assertIsNotEnabled
 import androidx.compose.ui.test.assertWidthIsAtLeast
 import androidx.compose.ui.test.junit4.v2.createAndroidComposeRule
@@ -285,6 +286,29 @@ class NowPlayingTapsTest {
         composeRule.onNodeWithTag(NOW_PLAYING_NEXT_TAG, useUnmergedTree = true).assertDoesNotExist()
     }
 
+    @Test
+    fun theSwipeTargetStaysInsideTheContentMargins() {
+        render()
+
+        val target = composeRule.onNodeWithTag(NOW_PLAYING_COVER_TAG).fetchSemanticsNode().boundsInRoot
+        val screen = composeRule.onRoot().fetchSemanticsNode().boundsInRoot
+
+        assertEquals(
+            "the swipe target must not reach into the screen margins",
+            screen.width - with(composeRule.density) { 48.dp.toPx() },
+            target.width,
+        )
+    }
+
+    @Test
+    fun theNeighboursStayHiddenAtRest() {
+        render(previousArt = adjacentArt("s-previous"), nextArt = adjacentArt("s-next"))
+
+        // TILE_GAP is what keeps them off-screen now that the strip is unclipped.
+        composeRule.onNodeWithTag(NOW_PLAYING_PREVIOUS_TAG, useUnmergedTree = true).assertIsNotDisplayed()
+        composeRule.onNodeWithTag(NOW_PLAYING_NEXT_TAG, useUnmergedTree = true).assertIsNotDisplayed()
+    }
+
     @Test
     fun aShortSlowDragOnTheCoverDoesNotSkip() {
         var next = false

docs/architecture.md

@@ -88,7 +88,7 @@ Playback is a *context* plus a manual *up next* list. `queue_entries` is the con
 
 Because the resolver reports *which entry* a position falls in, `PlaybackState` also carries the current queue context (`kind` and `refId`). That is what scopes the playing-track indicator in the album and playlist lists: a song that appears in both only lights up in the list the queue was actually started from.
 
-Stream URLs come from `SourceRepository.streamUri`, which asks the active `SubsonicSource` for a freshly salted `stream` URL; because the URL changes every request, artwork is attached to the media item by identity (the `CoverArtRef` cache key) rather than by URL. The active source carries the stream quality (a max bitrate plus an optional transcode format) for the current network: `NetworkMonitor` reports Wi-Fi vs mobile (metered) and `UserPreferences` stores a separate `StreamQuality` per mode, so `SourceRepository` rebuilds the source when either the mode or a quality changes. `PlaybackController` observes that effective quality and reloads the window around the current position, preserving play/pause and the playback position, so a Wi-Fi↔mobile transition re-issues the stream URLs with the new settings (a no-op when the two modes share a quality). Transcoded responses are chunked with no length and (because ffmpeg cannot seek back in a stream) no MP3 duration header, so Media3 would treat them as live and ignore seeks; the server's `estimateContentLength` is no better, since its estimate under-counts and cuts the track short. So a transcoded URL carries a declared upper-bound length in its fragment (never sent to the server), `KnownLengthDataSource` hands that length to Media3 to keep the stream seekable without truncation, and each transcoded item is clipped to the library duration so the timeline ends where the audio does and the next track still advances. Streamed bytes also pass through a bounded `SimpleCache` (`CacheDataSource` sits under `DefaultDataSource`, so downloads bypass it): a headerless MP3's duration is only estimated, and when the extractor rewrites it at end of stream Media3 drops and re-opens the prefetched next period. The cache serves the bytes that prefetch already buffered from disk, so the re-open does not re-fetch them (only bytes the cancelled prefetch never committed are fetched again). Keys are the salted stream URLs, so nothing is reused across a service restart; it is a bounded scratch buffer, not a persistent download.
+Stream URLs come from `SourceRepository.streamUri`, which asks the active `SubsonicSource` for a freshly salted `stream` URL; because the URL changes every request, artwork is attached to the media item by identity (the `CoverArtRef` cache key) rather than by URL. The active source carries the stream quality (a max bitrate plus an optional transcode format) for the current network: `NetworkMonitor` reports Wi-Fi vs mobile (metered) and `UserPreferences` stores a separate `StreamQuality` per mode, so `SourceRepository` rebuilds the source when either the mode or a quality changes. `PlaybackController` observes that effective quality and reloads the window around the current position, preserving play/pause and the playback position, so a Wi-Fi↔mobile transition re-issues the stream URLs with the new settings (a no-op when the two modes share a quality). Transcoded responses are chunked with no length and (because ffmpeg cannot seek back in a stream) no MP3 duration header, so Media3 would treat them as live and ignore seeks; the server's `estimateContentLength` is no better, since its estimate under-counts and cuts the track short. So a transcoded URL carries a declared upper-bound length in its fragment (never sent to the server), `KnownLengthDataSource` hands that length to Media3 to keep the stream seekable without truncation, and each transcoded item is clipped to the library duration so the timeline ends where the audio does and the next track still advances. Some streams stay length-unknown anyway: an Opus/Ogg/Vorbis transcode (a length estimate breaks the end-seek they rely on), a transcode of a track with no library duration, and a direct play the server does not give a `Content-Length`. Media3 marks an unknown-length, unknown-duration progressive stream live, and a live item makes the media session publish no playback position, so the notification would show no progress even though the item carries a real duration; `KnownDurationPlayer` wraps the `ExoPlayer` and reports an item with a library duration as finite, restoring the position and progress the session publishes without making the stream seekable. Streamed bytes also pass through a bounded `SimpleCache` (`CacheDataSource` sits under `DefaultDataSource`, so downloads bypass it): a headerless MP3's duration is only estimated, and when the extractor rewrites it at end of stream Media3 drops and re-opens the prefetched next period. The cache serves the bytes that prefetch already buffered from disk, so the re-open does not re-fetch them (only bytes the cancelled prefetch never committed are fetched again). Keys are the salted stream URLs, so nothing is reused across a service restart; it is a bounded scratch buffer, not a persistent download.
 
 The window is also the queue the media notification browses — a deliberate trade-off, since the alternative is holding an entire large library in memory. The queue view resolves positions lazily too: it loads the queue around the cursor in chunks and extends by a chunk when you scroll near either end, so it never materializes the whole queue. Dragging uses `sh.calvin.reorderable`, which floats the lifted row and reorders the loaded list live (animating with `animateItem`), so editing is what a drag needs: the view reorders its loaded list while dragging and commits one move on drop. `queue_entries` is rewritten to edit: removing a position splits its entry into up to two ranges, and moving one turns the moved track into an explicit song entry inserted at the target index, so an edit costs a couple of rows rather than a copy of the queue. When the edit falls inside the player's window the controller mirrors it with `removeMediaItem`/`moveMediaItem` so playback is not interrupted; removing the playing track, or a move that crosses the window boundary, reloads the window around the cursor. The controller keeps the pre-edit entries and cursor, so the queue view can offer a one-step undo. The up-next block is fully editable in the same view (drag reorder and delete), while the context is read-only while shuffled. Timed lyrics are not wired yet.