Signal Info
SignalInfo is a member of the signal information structure available in the callback function or returned by the signal information retrieving function.
Its value only makes sense when the relevant signal is the Surface Processing or Surface Filled signal.
In that case, SignalInfo contains the handle of the surface that experienced the designated state transition, i.e. the surface presently in the state PROCESSING or FILLED (see SurfaceState).
This handle enable the user to retrieve the reference of the surface where the acquisition phase just stored the acquire image. The application can advantageously use the surface parameter SurfaceContext accessed using this surface handle.