[ scummvm-Patches-2817533 ] EVENTS: EventManager and related cleanup

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Patches item #2817533, was opened at 2009-07-06 18:49
Message generated for change (Tracker Item Submitted) made by lordhoto
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Johannes Schickel (lordhoto)
Assigned to: Max Horn (fingolfin)
Summary: EVENTS: EventManager and related cleanup

Initial Comment:
Hi,

this patch fixes the fact the our DefaultEventManager is much too bloated. It includes the event recorder code, the keymapper use code etc. If a backend would want to create its own specific EventManager but still using some of those features it would either result in code duplication or skipping features, because implementing them would be too much work.

To overcome this fact I added a new "event dispatching API". This API includes the following classes:

- EventSource, a source of events (similar to the (now removed) EventProvider of DefaultEventManager)
- EventObserver, a observer of new events, if an observer finds an event wants to process alone, he is allowed to "eat" it
- EventMapper, a mapper, which allows mapping certain events to other events (the Keymapper implements this interface for example).
- EventDispatcher, a priority based dispatcher, which is catching events from sources, passing them to an registered mapper, and then passes it to the observers. So this is basically the point there events are caught from different subsystems and supplied to different sub systems.

BaseBackend is now an EventSource (instead of EventProvider) and automatically registered with the EventDispatcher of the DefaultEventManager on initialization. Another event source is the "ArtificialEventSource", which is used to process the old "EventManager::pushEvent" API. That all is hidden from the user in DefaultEventManager initialization.

Keymapper being a EventMapper now, makes it easy to assign it to an EventDispatcher. Thus if there's another EventManager subclass other than DefaultEventManager, it only needs to call EventDispatcher::registerMapper and it works just fine.

Another (I think) advantage is that one can now change our virtual keyboard being both an EventSource and an EventObserver. Due to that fact we can even allow our DefaultEventManager and the VKBD to coexist. That means: if the VKBD notices a click inside the VKBD area it will eat that event and thus prevent the running engine from getting the click event. Now the only thing left for a simultaneous engine + vkbd run is the overlay API not being able to display game and overlay at once. That is of course now a different matter. This new code base at least allows the event part to be adapted easily for this use case.

I have another patch lying around which refactors the event recoder into its own class "EventRecoder" and registers it with the global event dispatcher (of EventManager). I'll post that too, but you first need to apply the "events.patch". (NOTE: Actually I have it in even finer grained patches in my git repo, but I think for here those two will do, if we plan to accept the patches, I'll just commit from my git repo).

The "recorder.patch", which moves the event recorder into its own class (EventRecoder), also removes the rather confusing methods "registerRandomSource" and "processMillis" from EventManager. Of course those now are placed inside the EventRecoder class, which is much cleaner IMHO. All engines and the SDL backend are adapted for this change.

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