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Author SHA1 Message Date
William Wilgus
3e2b50ed3b lua events from rockbox
This library allows events to be subscribed / recieved within a lua script
most events in rb are synchronous so flags are set and later checked by a
secondary thread to make them (semi?) asynchronous.

There are a few caveats to be aware of:

FIRST, The main lua state is halted till the lua callback(s) are finished
 Yielding will not return control to your script from within a callback
 Also, subsequent callbacks may be delayed by the code in your lua callback
SECOND, You must store the value returned from the event_register function
 you might get away with it for a bit but gc will destroy your callback
 eventually if you do not store the event
THIRD, You only get one cb per event type
 ["action", "button", "custom", "playback", "timer"]
 (Re-registration of an event overwrites the previous one)

Usage:
 possible events =["action", "button", "custom", "playback", "timer"]

 local evX = rockev.register("event", cb_function, [timeout / flags])
  cb_function([id] [, data]) ... end

 rockev.suspend(["event"/nil][true/false]) passing nil affects all events
  stops event from executing, any but the last event before
  re-enabling will be lost, passing false, unregistering or re-registering
  an event will clear the suspend

 rockev.trigger("event", [true/false], [id])
  sets an event to triggered,
  NOTE!, CUSTOM_EVENT must be unset manually
  id is only passed to callback by custom and playback events

 rockev.unregister(evX)
  Use unregister(evX) to remove an event
  Unregistering is not necessary before script end, it will be
  cleaned up on script exit

Change-Id: Iea12a5cc0c0295b955dcc1cdf2eec835ca7e354d
2019-07-19 20:48:34 -05:00