sync policy that updates constantly and reuses messages
In include/message_filters/sync_policies I find ExactTime and ApproximateTime sync policies. Has anyone built one that will output something on the output topic every time a new message is received, combining whatever the most recent inputs are, reusing input messages as necessary?
There's probably an argument to be made that this wouldn't sync anything so it shouldn't be done with a sync policy, but I think you could still get some decent code-reuse by wrapping this logic up in a sync policy.
I see this as a message filter subscriber with n topics where the callback only gets called when the first topic arrives. It's easy to have n subscribers store the messages for use in the primary callback, but there is a deserialization penalty that a message filter ought to avoid. Seems useful.