FairEmail/patches/FastScroller.patch

--- ./support/recyclerview/recyclerview/src/main/java/androidx/recyclerview/widget/FastScroller.java	2020-03-23 17:03:46.092122318 +0100
+++ ./email/app/src/main/java/androidx/recyclerview/widget/FastScrollerEx.java	2020-04-24 21:08:55.544011257 +0200
@@ -37,8 +37,8 @@ import java.lang.annotation.RetentionPol
 /**
  * Class responsible to animate and provide a fast scroller.
  */
-@VisibleForTesting
-class FastScroller extends RecyclerView.ItemDecoration implements RecyclerView.OnItemTouchListener {
+//@VisibleForTesting
+public class FastScrollerEx extends RecyclerView.ItemDecoration implements RecyclerView.OnItemTouchListener {
     @IntDef({STATE_HIDDEN, STATE_VISIBLE, STATE_DRAGGING})
     @Retention(RetentionPolicy.SOURCE)
     private @interface State { }
@@ -135,7 +135,7 @@ class FastScroller extends RecyclerView.
         }
     };
 
-    FastScroller(RecyclerView recyclerView, StateListDrawable verticalThumbDrawable,
+    public FastScrollerEx(RecyclerView recyclerView, StateListDrawable verticalThumbDrawable,
             Drawable verticalTrackDrawable, StateListDrawable horizontalThumbDrawable,
             Drawable horizontalTrackDrawable, int defaultWidth, int scrollbarMinimumRange,
             int margin) {
@@ -359,6 +359,7 @@ class FastScroller extends RecyclerView.
                 (int) ((verticalVisibleLength * middleScreenPos) / verticalContentLength);
             mVerticalThumbHeight = Math.min(verticalVisibleLength,
                 (verticalVisibleLength * verticalVisibleLength) / verticalContentLength);
+            mVerticalThumbHeight = Math.max(mVerticalThumbHeight, mVerticalThumbDrawable.getIntrinsicHeight());
         }
 
         if (mNeedHorizontalScrollbar) {
@@ -448,12 +449,24 @@ class FastScroller extends RecyclerView.
         if (Math.abs(mVerticalThumbCenterY - y) < 2) {
             return;
         }
-        int scrollingBy = scrollTo(mVerticalDragY, y, scrollbarRange,
-                mRecyclerView.computeVerticalScrollRange(),
-                mRecyclerView.computeVerticalScrollOffset(), mRecyclerViewHeight);
-        if (scrollingBy != 0) {
-            mRecyclerView.scrollBy(0, scrollingBy);
+
+        androidx.recyclerview.widget.RecyclerView.Adapter adapter = mRecyclerView.getAdapter();
+        int count = (adapter == null ? 0 : adapter.getItemCount());
+        if (count == 1) {
+            int scrollingBy = scrollTo(mVerticalDragY, y, scrollbarRange,
+                    mRecyclerView.computeVerticalScrollRange(),
+                    mRecyclerView.computeVerticalScrollOffset(), mRecyclerViewHeight);
+            if (scrollingBy != 0) {
+                mRecyclerView.scrollBy(0, scrollingBy);
+            }
         }
+        else {
+            int scrollbarLength = scrollbarRange[1] - scrollbarRange[0];
+            float percentage = (scrollbarLength == 0 ? 0 : y / (float) scrollbarLength);
+            int pos = Math.round(count * percentage);
+            mRecyclerView.scrollToPosition(pos);
+        }
+
         mVerticalDragY = y;
     }
 
@@ -494,7 +507,7 @@ class FastScroller extends RecyclerView.
     @VisibleForTesting
     boolean isPointInsideVerticalThumb(float x, float y) {
         return (isLayoutRTL() ? x <= mVerticalThumbWidth
-            : x >= mRecyclerViewWidth - mVerticalThumbWidth)
+            : x >= mRecyclerViewWidth - mVerticalThumbWidth * 3)
             && y >= mVerticalThumbCenterY - mVerticalThumbHeight / 2
             && y <= mVerticalThumbCenterY + mVerticalThumbHeight / 2;
     }