Subclasses NSOutlineView to PBQLOutlineView that takes a controller which
should respond to toggleQuickLook:. This is used for our tree walker to
actually show QuickLook when space is pressed.
This adds a QuickLook button that will allow you to directly view any file in
the tree view in QuickLook. This is really nice for PDF's and images. You can
select multiple files and even play a slideshow if you want.
Currently it does not remove temporary files it created. This means that they
will probably stay around until you reboot.
This controller makes sure that only the current view
receives its notifications. Therefore we won't do any work that we don't
see, like parsing diffs or asking for trees. This makes everything quicker.
Pieter de Bie