labelWidget label; interactive widgets also use it for ID generation. A ## suffix can distinguish IDs without displaying the suffix.
current_itemZero-based selected item index in Int32Array[0], updated when the selection changes. Pass Int32Array storage, not a JS scalar; native access uses the supplied backing memory.
items_separated_by_zerosNUL-separated UTF-8 item labels terminated by an additional NUL (two NUL bytes after the final item).
popup_max_height_in_itemsVisible list height measured in items; -1 selects the default height.
True if the widget changed the supplied value; false if it remained unchanged.
Display a combo box with null-separated items.