keyboard navigation didn't support activation since we moved
the keynav to the child row widgets. We fix this by adding a
activate signal handler for the row and setting
widget_class->activate_signal to it.
https://bugzilla.gnome.org/show_bug.cgi?id=707778
... to make it possible to insert rows in the middle of the list without having
to fiddle with the sort functions. One of the first users is going to be Glade.
https://bugzilla.gnome.org/show_bug.cgi?id=705558
This was added from https://bugzilla.gnome.org/show_bug.cgi?id=691979
where it was wanted in order to get a "all children filtered" kind
of row. However, the solution is not really generic enough, because
filtering can happen for other reasons than a full refilter (i.e. due
to a row change), and the partial fix you can get by counting children
after refilter can be achieved by manually doing it whenever you manually
called refilter anyway.
Its possible we should have some better solution for the "empty state"
though.
Now that we automatically set up the focus_vadjustment we only
need the adjustment to handle the page-up/down scroll length correctly.
We use parent_set to automatically pick up the adjustment from a
scrollable (i.e. viewport) parent which makes add_to_scrolled useless, so
it can be removed.
