  We investigate the leading twist quark generalized transverse momentum
distributions (GTMDs) at nonzero skewness in a light-front quark-diquark model
for the nucleon motivated by soft-wall AdS/QCD. The boost-invariant
longitudinal coordinate, $\sigma=\frac{1}{2} b^- P^+$, is identified as the
Fourier conjugate of the skewness. The Fourier transform of the GTMDs with
respect to the skewness variable $\xi$ can be employed to provide the Wigner
distributions in the boost-invariant longitudinal position space $\sigma$, the
coordinate conjugate to light-front time, $\tau=t+z/c$. The Wigner
distributions in the longitudinal position space exhibit diffraction patterns,
which are analogous to the diffractive scattering of a wave in optics.
