= class Gtk::Bin
The Gtk::Bin widget is a container with just one child. It is not very useful itself, but it is useful for deriving subclasses, since it provides common code needed for handling a single child widget. 

Many Ruby/GTK widgets are subclasses of Gtk::Bin, including Gtk::Window, Gtk::Button, Gtk::Frame, Gtk::HandleBox, and Gtk::ScrolledWindow. 

== Object Hierarchy
* Object
  * GLib::Instantiatable
    * GLib::Object
      * Gtk::Object
        * Gtk::Widget
          * Gtk::Container
            * Gtk::Bin

== Instance Methods
--- child
    Gets the child of the Gtk::Bin, or nil if the bin contains no child widget. The returned widget does not have a reference added, so you do not need to unref it.

- ((<Masao>))