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.
itemsItem labels in display order; items_count must not exceed the array length.
items_countNumber of items to process; it must match the available item data.
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 drop-down selector populated from an array of item labels.