There is no label provider to update for table viewers
Register some fonts in fontRegistry to be used for objects
Deal with fonts for objects
Manage the tree state when refreshing after a preference change. To do
that, must store the expandedTreePath before refresh, and, very
important, to implement hashcode and equals on the TNode !
Actually it is useless to call getExpandedTreePath if the TNode has its
own equals and hascode method.