gio:application-default ()

application -- a g:application instance to set as default, or nil

Accessor of the default application for the process. The g:application-default function returns the default application instance for this process. The (setf g:application-default) function sets or unsets the default application.

Normally there is only one application per process and it becomes the default when it is created. You can exercise more control over this by using this function.

If there is no default application then nil is returned.