detail: improve disc header design

app/src/main/java/org/oxycblt/auxio/IntegerTable.kt

@@ -49,8 +49,10 @@ object IntegerTable {
     const val VIEW_TYPE_ARTIST_SONG = 0xA00A
     /** DiscHeaderViewHolder */
     const val VIEW_TYPE_DISC_HEADER = 0xA00B
+    /** DiscHeaderViewHolder */
+    const val VIEW_TYPE_DISC_DIVIDER = 0xA00C
     /** EditHeaderViewHolder */
-    const val VIEW_TYPE_EDIT_HEADER = 0xA00C
+    const val VIEW_TYPE_EDIT_HEADER = 0xA00D
     /** PlaylistSongViewHolder */
     const val VIEW_TYPE_PLAYLIST_SONG = 0xA00E
     /** "Music playback" notification code */

app/src/main/java/org/oxycblt/auxio/detail/DetailViewModel.kt

@@ -29,6 +29,7 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.yield
 import org.oxycblt.auxio.R
+import org.oxycblt.auxio.detail.list.DiscDivider
 import org.oxycblt.auxio.detail.list.DiscHeader
 import org.oxycblt.auxio.detail.list.EditHeader
 import org.oxycblt.auxio.detail.list.SortHeader
@@ -554,7 +555,16 @@ constructor(
                             newList.add(Divider(header))
                         }
                         newList.add(header)
-                        section.discs.flatMap { listOf(DiscHeader(it.key)) + it.value }
+                        buildList<Item> {
+                            for (entry in section.discs) {
+                                val discHeader = DiscHeader(inner = entry.key)
+                                if (isNotEmpty()) {
+                                    add(DiscDivider(discHeader))
+                                }
+                                add(discHeader)
+                                addAll(entry.value)
+                            }
+                        }
                     }
                 }
             // Currently only the final section (songs, which can be sorted) are invalidatable

app/src/main/java/org/oxycblt/auxio/detail/list/AlbumDetailListAdapter.kt

@@ -24,6 +24,7 @@ import androidx.core.view.isGone
 import androidx.core.view.isInvisible
 import androidx.core.view.isVisible
 import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.divider.MaterialDivider
 import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.ItemAlbumSongBinding
@@ -38,6 +39,7 @@ import org.oxycblt.auxio.music.info.Disc
 import org.oxycblt.auxio.music.info.resolveNumber
 import org.oxycblt.auxio.playback.formatDurationMs
 import org.oxycblt.auxio.util.context
+import org.oxycblt.auxio.util.getAttrColorCompat
 import org.oxycblt.auxio.util.inflater
 
 /**
@@ -52,6 +54,7 @@ class AlbumDetailListAdapter(private val listener: Listener<Song>) :
         when (getItem(position)) {
             // Support sub-headers for each disc, and special album songs.
             is DiscHeader -> DiscHeaderViewHolder.VIEW_TYPE
+            is DiscDivider -> DiscDividerViewHolder.VIEW_TYPE
             is Song -> AlbumSongViewHolder.VIEW_TYPE
             else -> super.getItemViewType(position)
         }
@@ -59,6 +62,7 @@ class AlbumDetailListAdapter(private val listener: Listener<Song>) :
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
         when (viewType) {
             DiscHeaderViewHolder.VIEW_TYPE -> DiscHeaderViewHolder.from(parent)
+            DiscDividerViewHolder.VIEW_TYPE -> DiscDividerViewHolder.from(parent)
             AlbumSongViewHolder.VIEW_TYPE -> AlbumSongViewHolder.from(parent)
             else -> super.onCreateViewHolder(parent, viewType)
         }
@@ -79,6 +83,8 @@ class AlbumDetailListAdapter(private val listener: Listener<Song>) :
                     when {
                         oldItem is Disc && newItem is Disc ->
                             DiscHeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
+                        oldItem is DiscDivider && newItem is DiscDivider ->
+                            DiscDividerViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is Song && newItem is Song ->
                             AlbumSongViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
 
@@ -96,6 +102,8 @@ class AlbumDetailListAdapter(private val listener: Listener<Song>) :
  */
 data class DiscHeader(val inner: Disc?) : Item
 
+data class DiscDivider(val anchor: DiscHeader?) : Item
+
 /**
  * A [RecyclerView.ViewHolder] that displays a [DiscHeader] to delimit different disc groups. Use
  * [from] to create an instance.
@@ -140,6 +148,42 @@ private class DiscHeaderViewHolder(private val binding: ItemDiscHeaderBinding) :
     }
 }
 
+/**
+ * A [RecyclerView.ViewHolder] that displays a [DiscHeader]. Use [from] to create an instance.
+ *
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class DiscDividerViewHolder private constructor(divider: MaterialDivider) :
+    RecyclerView.ViewHolder(divider) {
+
+    init {
+        divider.dividerColor =
+            divider.context
+                .getAttrColorCompat(com.google.android.material.R.attr.colorOutlineVariant)
+                .defaultColor
+    }
+
+    companion object {
+        /** Unique ID for this ViewHolder type. */
+        const val VIEW_TYPE = IntegerTable.VIEW_TYPE_DISC_DIVIDER
+
+        /**
+         * Create a new instance.
+         *
+         * @param parent The parent to inflate this instance from.
+         * @return A new instance.
+         */
+        fun from(parent: View) = DiscDividerViewHolder(MaterialDivider(parent.context))
+
+        /** A comparator that can be used with DiffUtil. */
+        val DIFF_CALLBACK =
+            object : SimpleDiffCallback<DiscDivider>() {
+                override fun areContentsTheSame(oldItem: DiscDivider, newItem: DiscDivider) =
+                    oldItem.anchor == newItem.anchor
+            }
+    }
+}
+
 /**
  * A [RecyclerView.ViewHolder] that displays a [Song] in the context of an [Album]. Use [from] to
  * create an instance.

app/src/main/res/layout/item_disc_header.xml

@@ -6,57 +6,49 @@
     android:layout_height="wrap_content"
     android:orientation="horizontal"
     android:paddingStart="@dimen/spacing_medium"
-    android:paddingTop="@dimen/spacing_mid_medium"
+    android:paddingTop="@dimen/spacing_small"
     android:paddingEnd="@dimen/spacing_medium"
-    android:paddingBottom="@dimen/spacing_mid_medium">
+    android:paddingBottom="@dimen/spacing_small">
 
-    <org.oxycblt.auxio.image.CoverView
-        android:id="@+id/disc_cover"
-        style="@style/Widget.Auxio.Image.Small"
-        android:scaleType="matrix"
-        app:enablePlaybackIndicator="false"
-        app:enableSelectionBadge="false"
-        app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        tools:ignore="ContentDescription">
 
     <ImageView
         android:id="@+id/disc_icon"
-            android:layout_width="match_parent"
+        android:layout_width="48dp"
-            android:layout_height="match_parent"
+        android:layout_height="0dp"
         android:scaleType="center"
         android:src="@drawable/ic_album_24"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
         app:tint="@color/sel_on_cover_bg"
         tools:ignore="ContentDescription" />
 
-    </org.oxycblt.auxio.image.CoverView>
-
     <TextView
         android:id="@+id/disc_number"
-        style="@style/Widget.Auxio.TextView.Item.Primary"
+        style="@style/Widget.Auxio.TextView.Primary.Compact"
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_marginEnd="@dimen/spacing_mid_medium"
+        android:layout_marginStart="@dimen/spacing_medium"
         android:textColor="@color/sel_selectable_text_primary"
         app:layout_constraintBottom_toTopOf="@+id/disc_name"
         app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintStart_toEndOf="@+id/disc_cover"
+        app:layout_constraintStart_toEndOf="@+id/disc_icon"
-        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintTop_toTopOf="@+id/disc_icon"
         app:layout_constraintVertical_chainStyle="packed"
         tools:text="Disc 1" />
 
     <TextView
         android:id="@+id/disc_name"
-        style="@style/Widget.Auxio.TextView.Item.Secondary"
+        style="@style/Widget.Auxio.TextView.Secondary.Compact"
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_marginEnd="@dimen/spacing_mid_medium"
-        app:layout_constraintBottom_toBottomOf="parent"
+        android:layout_marginStart="@dimen/spacing_medium"
+        app:layout_constraintBottom_toBottomOf="@+id/disc_icon"
         app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintStart_toEndOf="@+id/disc_cover"
+        app:layout_constraintStart_toEndOf="@+id/disc_icon"
         app:layout_constraintTop_toBottomOf="@+id/disc_number"
-        tools:text="Part 1"
+        tools:text="Part 1" />
-        tools:visibility="gone" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>