As above, I want a custom function. When I slide the mouse wheel, the vertical box can show what I want. I don’t want to use the scrollbox, for I don’t know which item is in the middle in the scrollbox.
You can place any other widgets inside the scrollbox. Just the same as you can do it using vertical or horisontal or size or scale boxes or overlay or other widgets suppoorting childs inside them. Nothing special about scrollbox here.