queue: scroll to top of list on song changes

Always scroll to the top of the queue list when the current song
changes.

This way, the user can see future items rather than past items.

In an ideal world, I would try to go to the center of the queue, but
it seems like the "average" scroll tends to settle at the top no
matter what I do, so whatever. There's also a slight in-accuracy
in what the app considers the "Top" of the queue, but that's considered
minimally detrimental given how much a QoL improvement this is.

Resolves #210.

CHANGELOG.md

@@ -8,6 +8,7 @@
 #### What's Improved
 - Formalized whitespace handling
 - Value lists are now properly localized
+- Queue no longer primarily shows previous songs when opened
 
 ## 3.0.0
 

app/src/main/java/org/oxycblt/auxio/music/Music.kt

@@ -520,7 +520,6 @@ class Song constructor(raw: Raw, settings: Settings) : Music() {
         for (i in _artists.indices) {
             // Non-destructively reorder the linked artists so that they align with
             // the artist ordering within the song metadata.
-            // TODO: Make sure this works for artists only derived from album artists.
             val newIdx = _artists[i]._getOriginalPositionIn(_rawArtists)
             val other = _artists[newIdx]
             _artists[newIdx] = _artists[i]

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueAdapter.kt

@@ -199,7 +199,8 @@ class QueueSongViewHolder private constructor(private val binding: ItemQueueSong
         binding.songAlbumCover.bind(song)
         binding.songName.text = song.resolveName(binding.context)
         binding.songInfo.text = song.resolveArtistContents(binding.context)
-        // TODO: Why is this here?
+        // Not swiping this ViewHolder if it's being re-bound, ensure that the background is
+        // not visible. See QueueDragCallback for why this is done.
         binding.background.isInvisible = true
 
         // Set up the drag handle to start a drag whenever it is touched.

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueFragment.kt

@@ -24,6 +24,7 @@ import androidx.fragment.app.activityViewModels
 import androidx.recyclerview.widget.ItemTouchHelper
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import kotlin.math.min
 import org.oxycblt.auxio.databinding.FragmentQueueBinding
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.playback.PlaybackViewModel
@@ -108,17 +109,24 @@ class QueueFragment : ViewBindingFragment<FragmentQueueBinding>(), QueueAdapter.
         queueModel.finishReplace()
 
         // If requested, scroll to a new item (occurs when the index moves)
-        // TODO: Scroll to center/top instead of bottom
         val scrollTo = queueModel.scrollTo
         if (scrollTo != null) {
-            // Do not scroll to indices that are in the currently visible range. As that would
-            // lead to the queue jumping around every time goto is called.
             val lmm = binding.queueRecycler.layoutManager as LinearLayoutManager
             val start = lmm.findFirstCompletelyVisibleItemPosition()
             val end = lmm.findLastCompletelyVisibleItemPosition()
-            if (scrollTo !in start..end) {
-                logD("Scrolling to new position")
+            val notInitialized = start == RecyclerView.NO_POSITION || end == RecyclerView.NO_POSITION
+            // When we scroll, we want to scroll to the almost-top so the user can see
+            // future songs instead of past songs. The way we have to do this however is
+            // dependent on where we have to scroll to get to the currently playing song.
+            if (notInitialized || scrollTo < start) {
+                // We need to scroll upwards, or initialize the scroll, no need to offset
                 binding.queueRecycler.scrollToPosition(scrollTo)
+            } else if (scrollTo > end) {
+                // We need to scroll downwards, we need to offset by a screen of songs.
+                // This does have some error due to what the layout manager returns being
+                // somewhat mutable. This is considered okay.
+                binding.queueRecycler.scrollToPosition(
+                    min(queue.lastIndex, scrollTo + (end - start)))
             }
         }
         queueModel.finishScrollTo()