You could make a callback that only pushes to a buffer for later processing - to achieve the same behaviour that I suggested. So in a way, callbacks are more ge

You could make a callback that only pushes to a buffer for later processing - to achieve the same behaviour that I suggested. So in a way, callbacks are more general (for an event that was pushed to a buffer, you can't have it be immediately processed by the other party, unless you add major threading and scheduling hackery). Nevertheless I recommend to never make a callback based API unless there is a clear need for callbacks. If there isn't a need, plain buffers (Maybe I should better say "queues") and decoupled processing are the right thing. Callbacks encourage synchronous processing and where they are used to only push to a buffer they are only overhead.