ScrollView onValueChanged description doesn't match real behavior

[socantre]

docs/ui/layoutgrouping.md

The description of VerticalScrollView's onValueChanged attribute reads:

When a selection is made, its name is sent to a function with this name.

This makes it sound like a VerticalScrollView has some 'selection' which changes, and callback function is called whenever that selection changes (when a user selects something?). However instead I observe that the callback is called constantly when the VerticalScrollView is visible, the arguments given to the callback are a player, a string containing a couple of numbers which seem related to the ScrollView's scroll position and position, and the id of the ScrollView itself.

I'd like to create a UI that shows a list of items that the user can select from, sort of like a <Dropdown> but with a scrollable view. VerticalScrollView's docs make it sound like it could do the job but I haven't found how to make it work.

-- lua script

count = 0
function onValueChanged_listSelection(arg1, arg2, arg3, arg4)
  count = count + 1
  print(count, type(arg1), arg1, type(arg2), arg2, type(arg3), arg3, type(arg4), arg4)
end

-- UI xml snippet

<VerticalScrollView
  id="item_selection"
  onValueChanged="onValueChanged_listSelection"
  color="rgb(0,0,0)" minHeight="100" preferredHeight="200" flexibleHeight="100">
    <VerticalLayout id='layout'>
        <Panel id='panel1' minHeight="30"><Text id='line1'>1</Text></Panel>
        <Panel id='panel2' minHeight="30"><Text id='line2'>2</Text></Panel>
        <Panel id='panel3'><Text id='line3'>3</Text></Panel>
        <Panel id='panel4'><Text id='line4'>4</Text></Panel>
        <Panel id='panel5'><Text id='line5'>5</Text></Panel>