  We recall the fat-graph description of Riemann surfaces $\Sigma_{g,s,n}$ and
the corresponding Teichm\"uller spaces $\mathfrak T_{g,s,n}$ with $s>0$ holes
and $n>0$ bordered cusps in the hyperbolic geometry setting. If $n>0$, we have
a bijection between the set of Thurston shear coordinates and Penner's
$\lambda$-lengths and we can induce, on the one hand, the Poisson bracket on
$\lambda$-lengths from the Poisson bracket on shear coordinates introduced by
V.V.Fock in 1997 and, on the other hand, a symplectic structure
$\Omega_{\text{WP}}$ on the set of extended shear coordinates from Penner's
symplectic structure on $\lambda$-lengths. We derive $\Omega_{\text{WP}}$,
which turns out to be similar to the Kontsevich symplectic structure for
$\psi$-classes in complex-analytic geometry, and demonstrate that it is indeed
inverse to the Fock Poisson structure.
