The compositor assumes the entire viewport as its compositing space even
in camera view. The current design decision was to limit the compositing
space by the camera region only if the camera passepartout is opaque,
that is, areas outside of the camera are not visible.
This patch changes that behavior to always limit the compositing space
by the camera region. The downside is that areas outside of the camera
will be left uncomposited.
Omar Emara