I have made a structure view example stripped down to the absolute minimum
Everything works fine (I already implemented sorters, groupers) but I'm just not able to make the CollapseAll button work if I have a one-level tree, meaning only the file as root in the structure view and all other elements in the next level. The thing looks like this
I can click the small triangle and the tree collapses but the collapseAll button just doesn't work. I have now looked at the implementation of the structure view of "properties", "lua", "dart", and some more and I cannot find what I'm doing wrong.