Factorio Forums

The value "selected_index" of a listbox never updates when calling methods that modifies the item list, even "clear_items".

Steps to reproduce:
- Display a list with items - Select the last item
- Print the selected item index - Remove the last item I expected the index to change to the last item if you removed the last item, either by becoming nil, 0 or by selecting the new last item, but index does not change at all. This can be problematic as the index is now pointing to a non-existant item in the list.
- Clear the list The selected index is still the same as before. You have now a non-zero index in an empty list.
- Fill the list again The selected index still didn't changed, but now the item does not appear selected in the list.
This also happen when you insert an item before the selected item : the highlighted item is not the one the selected index is pointing to.

Thanks for the report.
Fixed for 0.17.66

The item that you selected will stay selected if you add or remove other items (so selected_index will be adjusted if needed). If you remove selected item, selected_index will become 0 (no item is selected)

If you change items by writing to LuaGuiElement::items, selected_index will be preserved if count of new items allows it. (I am still not sure if this is good behavior, though)