  Non-wetting substrates allow impacting liquid drops to spread, recoil, and
takeoff, provided they are not too heavy (Biance et al. 2006) or too viscous
(Jha et al. 2020). In this article, using direct numerical simulations with the
volume of fluid method, we investigate how viscous stresses and gravity
conspire against capillarity to inhibit drop rebound. Close to the bouncing to
non-bouncing transition, we evidence that the initial spreading stage can be
decoupled from the later retraction and takeoff, allowing to understand the
rebound as a process converting the surface energy of the spread liquid into
kinetic energy. Drawing an analogy with coalescence induced jumping, we propose
a criterion for the transition from the bouncing to the non-bouncing regime,
namely by the condition $Oh_c + Bo_c \sim 1$, where $Oh_c$ and $Bo_c$ are the
Ohnesorge number and Bond number at the transition, respectively. This
criterion is in excellent agreement with the numerical results. We also
elucidate the mechanisms of bouncing inhibition in the heavy and viscous drops
limiting regimes by calculating the energy budgets and relating them to the
drop's shape and internal flow.
