the tree view class is working, albeit with a few glitches still.

In order to get the scene graph tree working, there were a whole lot of problems with the grid class to be solved. That took its sweet time, but it’s (mostly) behaving the way it’s intended now.

What remains to be done is icon support in list views / labels, as well as the implementation of the eventhandler in the scene graph tree view.

After all, we want to be able to interact with the tree, not just look at all those pretty names.