A toplevel window to be embedded into other processes.
This class provides the ability to embed widgets from one process into another in a way that is transparent to the user. One process creates a GtkSocket widget and passes the ID of that widget's window to the other process, which then creates a GtkPlug with that window ID. Any widgets contained in the GtkPlug will appear inside the first application's window.
get_id() Retrieves the window ID for the plug.
"embedded" Emitted when plug window is reparented to socket window.