widget/material: use more efficient way of scrolling lists

Signed-off-by: Dominik Honnef <[email protected]>

widget/material/list.go

@@ -292,12 +292,7 @@ func (l ListStyle) Layout(gtx layout.Context, length int, w layout.ListElement)
 	if delta := l.state.ScrollDistance(); delta != 0 {
 		// Handle any changes to the list position as a result of user interaction
 		// with the scrollbar.
-		l.state.List.Position.Offset += int(math.Round(float64(float32(l.state.Position.Length) * delta)))
-
-		// Ensure that the list pays attention to the Offset field when the scrollbar drag
-		// is started while the bar is at the end of the list. Without this, the scrollbar
-		// cannot be dragged away from the end.
-		l.state.List.Position.BeforeEnd = true
+		l.state.List.ScrollBy(delta * float32(length))
 	}
 
 	if l.AnchorStrategy == Occupy {