idleSourceNew
Creates a new idle source.
The source will not initially be associated with any struct@GLib.MainContext and must be added to one with method@GLib.Source.attach before it will be executed. Note that the default priority for idle sources is const@GLib.PRIORITY_DEFAULT_IDLE, as compared to other sources which have a default priority of const@GLib.PRIORITY_DEFAULT.
Return
the newly-created idle source