  Point-form relativistic quantum mechanics is used to derive an expression for
the electromagnetic form factor of a pseudoscalar meson for space-like momentum
transfers. The elastic scattering of an electron by a confined quark-antiquark
pair is treated as a relativistic two-channel problem for the $q\bar{q}e$ and
$q\bar{q}e\gamma$ states. With the approximation that the total velocity of the
$q\bar{q}e$ system is conserved at (electromagnetic) interaction vertices this
simplifies to an eigenvalue problem for a Bakamjian-Thomas type mass operator.
After elimination of the $q\bar{q}e\gamma$ channel the electromagnetic meson
current and form factor can be directly read off from the one-photon-exchange
optical potential. By choosing the invariant mass of the electron-meson system
large enough, cluster separability violations become negligible. An equivalence
with the usual front-form expression, resulting from a spectator current in the
$q^+=0$ reference frame, is established. The generalization of this
multichannel approach to electroweak form factors for an arbitrary bound
few-body system is quite obvious. By an appropriate extension of the Hilbert
space this approach is also able to accommodate exchange-current effects.
