Until now the Tree.NodeExpanded and Tree.NodeCollapsed messages were only
sent out when changes were made to the tree by user interaction. This meant
that if any changes were made with the TreeNode expand, expand_all,
collapse, collapse_all, toggle or toggle_all API calls no messages would be
sent.
This PR corrects this.
The work here is, in part, required for #2456 (DirectoryTree lazy-loads
directory information on node expansion so if someone is expanding nodes
under code control the DirectoryTree never gets to know that it should load
a directory's content) and will build on #1644, essentially adding a missing
aspect to the latter PR.
Currently, in the various TreeNode messages, and the handlers you'd write to
handle them, there's no way to easily know *which* tree sent the message and
so which tree the node belongs to.
This commit adds public access to the tree reference to the nodes, so that
in an event handler the developer can check the tree involved in the event.
See #2413.
This is sort of different from selected. Selected is when someone mashes the
enter button or clicks on a node. Highlighted is when the cursor moves into
a new node.
See #1400.
