Peter Smet wrote:
My understanding of events is much more basic than the others discussing this issue, but I have a naive question.
Why are low level OS events like mouse clicks and keyboard strokes treated differently from a general events mechanism? By this I mean a mechanism for passing messages to 'subscribers' whenever an object emits an event (publish-subscribe)? It seems to me that any event still has an Object from which it originates, and one or more objects that will be told the event has occurred. Why can't low and high level events share the same abstractions, and even be placed on the same event queue? I also think exception-handling has much in common with event handling (on: exception do: aBlock). The exception looks to me very much like an 'event' that the block is told about. Is it possible to fuse these three mechanisms into a common abstraction and reuse a lot of the code, or is this just wishful thinking on my part?
I'm afraid it's wishful thinking.
Events are delivered asynchronously. The event generating process is normally not the one that receives the event.
Exceptions should be delivered synchronously, to the same process that raised the exception, with access to the context at the point where the exception was raised.
Updates (subscriptions) could be delivered asynchronously, but that's not the Smalltalk tradition. Quite a bit of Smalltalk code assumes that updates are handled immediately after they're generated, before the generator executes the next line of code.