The method Region.getUserAgentStylesheet() gets called many times in the context of a (tree) table view. I noticed that my app calls it 1800 times before the UI is initially shown. If the method is overriden by a custom control and performs a resource lookup then the performance will degrade significantly.

To test simply override getUserAgentStylesheet() of a tree table view like this:

                        int counter = 0;
public String getUserAgentStylesheet() {
System.out.println("method called " + (counter++));
return super.getUserAgentStylesheet();
}

I would expect that this method gets called exactly once per custom control.