Monge-Amp`{e}re measures on contact sets

Let $(X, omega)$ be a compact Kahler manifold of complex dimension n and $theta$ be a smooth closed real $(1,1)$-form on $X$ such that its cohomology class ${ theta }in H^{1,1}(X, mathbb{R})$ is pseudoeffective. Let $varphi$ be a $theta$-psh function, and let $f$ be a continuous function on $X$ with bounded distributional laplacian with respect to $omega$ such that $varphi leq f. $ Then the non-pluripolar measure $theta_varphi^n:= (theta + dd^c varphi)^n$ satisfies the equality: $$ {bf{1}}_{{ varphi = f }} theta_varphi^n = {bf{1}}_{{ varphi = f }} theta_f^n,$$ where, for a subset $Tsubseteq X$, ${bf{1}}_T$ is the characteristic function. In particular we prove that [ theta_{P_{theta}(f)}^n= { bf {1}}_{{P_{theta}(f) = f}} theta_f^nqquad {rm and }qquad theta_{P_theta[varphi](f)}^n = { bf {1}}_{{P_theta[varphi](f) = f }} theta_f^n. ]