GtkPolicyType
Determines when a scroll bar will be visible.
Value | Symbolic name | Description |
  0 | Gtk::POLICY_ALWAYS | The scrollbar is always visible. |
  1 | Gtk::POLICY_AUTOMATIC | The scrollbar will appear and disappear as necessary. For example, when all of a GtkCList can not be seen. |
  2 | Gtk::POLICY_NEVER | The scrollbar will never appear. |