this will, I think, create a new StoragePlugin object each time I iterate through the plugins. In this way I won't able to store the state in the plugin, as each invocation will return a default plugin object.
I think I've to rewrite this a bit to iterate through all factories at initialisation and create an array of plugins (by using the method shown above) and afterwards use this list, or I'll create the plugins as singletons. I'll try these possibilities tonight.
One question still stands though, why did a Button work and a TreeCtrl didn't, just coincidence?