Gtk2::ImageView::Nav is a popup window that shows a downscaled preview of the pixbuf that Gtk2::ImageView is showing. The user can drag around a rectangle which indicates the current view of the image.
This class is used by Gtk2::ImageView::ScrollWin itself. It is probably not very useful for clients of this library.
Gtk2::ImageView::Nav has the same keybindings that Gtk2::ImageView has. All keypresses that it receives are passed along to the view.
The pixbuf is by default undef.