Fast scroll on details now has the correct offset for the chapter its on

Also chapters with an unknown volume now show the chapter name instead of just "unknown"

app/src/main/java/eu/kanade/tachiyomi/ui/library/MaterialFastScroll.kt

@@ -3,7 +3,9 @@ package eu.kanade.tachiyomi.ui.library
 import android.content.Context
 import android.util.AttributeSet
 import android.view.MotionEvent
+import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.StaggeredGridLayoutManager
 import eu.davidea.fastscroller.FastScroller
 import eu.kanade.tachiyomi.R
 import eu.kanade.tachiyomi.util.system.dpToPxEnd
@@ -13,6 +15,7 @@ import kotlin.math.abs
 class MaterialFastScroll @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null) :
     FastScroller(context, attrs) {
 
+    var scrollOffset = 0
     init {
         setViewsToUse(
             R.layout.material_fastscroll, R.id.fast_scroller_bubble, R.id.fast_scroller_handle
@@ -35,6 +38,20 @@ class MaterialFastScroll @JvmOverloads constructor(context: Context, attrs: Attr
         }
     }
 
+    override fun setRecyclerViewPosition(y: Float) {
+        if (recyclerView != null) {
+            val targetPos = getTargetPos(y)
+            if (layoutManager is StaggeredGridLayoutManager) {
+                (layoutManager as StaggeredGridLayoutManager).scrollToPositionWithOffset(
+                    targetPos, scrollOffset
+                )
+            } else {
+                (layoutManager as LinearLayoutManager).scrollToPositionWithOffset(targetPos, scrollOffset)
+            }
+            updateBubbleText(targetPos)
+        }
+    }
+
     private fun updateScrollListener() {
         onScrollListener = object : RecyclerView.OnScrollListener() {
             override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {

app/src/main/java/eu/kanade/tachiyomi/ui/manga/MangaDetailsAdapter.kt

@@ -71,7 +71,7 @@ class MangaDetailsAdapter(
                         else R.string.volume_, volume
                     )
                 } else {
-                    recyclerView.context.getString(R.string.unknown)
+                    getChapterName(chapter)
                 }
             }
             MangaDetailsPresenter.TENS_OF_CHAPTERS -> recyclerView.context.getString(
@@ -79,13 +79,17 @@ class MangaDetailsAdapter(
                     chapter.chapter_number
                 )
             )
-            else -> if (chapter.chapter_number > 0) {
+            else -> getChapterName(chapter)
+        }
+    }
+
+    private fun getChapterName(item: ChapterItem): String {
+        return if (item.chapter_number > 0) {
             recyclerView.context.getString(
-                    R.string.chapter_, decimalFormat.format(chapter.chapter_number)
+                R.string.chapter_, decimalFormat.format(item.chapter_number)
             )
         } else {
-                chapter.name
+            item.name
-            }
         }
     }
 

app/src/main/java/eu/kanade/tachiyomi/ui/manga/MangaDetailsController.kt

@@ -199,7 +199,10 @@ class MangaDetailsController : BaseController,
 
         setRecycler(view)
         setPaletteColor()
-        adapter?.fastScroller = fast_scroller2
+        adapter?.fastScroller = fast_scroller
+        fast_scroller.addOnScrollStateChangeListener {
+            activity?.appbar?.y = 0f
+        }
 
         presenter.onCreate()
         swipe_refresh.isRefreshing = presenter.isLoading
@@ -264,10 +267,11 @@ class MangaDetailsController : BaseController,
         swipe_refresh.setProgressViewOffset(false, (-40).dpToPx, headerHeight + offset)
         // 1dp extra to line up chapter header and manga header
         getHeader()?.setTopHeight(headerHeight)
-        fast_scroller2.updateLayoutParams<ViewGroup.MarginLayoutParams> {
+        fast_scroller.updateLayoutParams<ViewGroup.MarginLayoutParams> {
             topMargin = headerHeight
             bottomMargin = insets.systemWindowInsetBottom
         }
+        fast_scroller.scrollOffset = headerHeight
     }
 
     /** Set the toolbar to fully transparent or colored and translucent */

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

@@ -29,7 +29,7 @@
     </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
 
     <eu.kanade.tachiyomi.ui.library.MaterialFastScroll
-        android:id="@+id/fast_scroller2"
+        android:id="@+id/fast_scroller"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         app:fastScrollerBubbleEnabled="true" />