  In recent years, two important techniques for geometric numerical
discretization have been developed. In computational electromagnetics, spatial
discretization has been improved by the use of mixed finite elements and
discrete differential forms. Simultaneously, the dynamical systems and
mechanics communities have developed structure-preserving time integrators,
notably variational integrators that are constructed from a Lagrangian action
principle. Here, we discuss how to combine these two frameworks to develop
variational spacetime integrators for Maxwell's equations. Extending our
previous work, which first introduced this variational perspective for
Maxwell's equations without sources, we also show here how to incorporate free
sources of charge and current.
