logic AND with event structure

[superfunk]

hi everyone,

The event structure can handle multiple events at a time to do the same thing : looks like a logical OR. But I haven't found a way to sequence events to approach a logic AND. Example: first click on a Draw button and then enter the image would make the mouse cursor change. With an event structure, I can handle these 2 events separetely or together (either one would change the cursor), but i cannot make a sequence of events.

Is this possible to do that with an event structure?

I hope I am clear (sorry for the english btw). And thanks in advance.

Christophe

[MikeS81]

Hi Christophe,

you can use shiftregisters to store "old" values. Use events like "enter"/"leave" Control to coordinate the content of them.

Mike

[Mark_Yedinak · Accepted solution]

I don't think this is possible directly. You will need to add state information to your event loop which would enforce the order of events and the logic rules you desire. In the event processing you would have to check if the required event occurred before this event. If it did, do your processing. If not ignore the event. Your first event would need to set this state information. You may also want to include some type of timeout so that the second event would have to occur within a specific amount of time.

This type of logic may be better handled using a producer/consumer architecture and a state machine in the consumer task.

[superfunk]

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Mark Yedinak wrote:

 In the event processing you would have to check if the required event occurred before this event. If it did, do your processing. If not ignore the event.

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That's exactly what I am trying to do! I am already working with a producer/consumer architecture and with a state machine in the consumer loop. I tried to add state info as you suggested in the event loop. But i do not know if i am doing this well. I attach a very small example where I try to demonstrate what I am trying to do with 2 booleans to be pressed in order.

Tell me what you think of the state info in the event loop.

@Mike : same solution as Mark if I use a shift register and a case structure inside the event loop?

Message Edited by superfunk on 03-03-2010 10:24 AM

[Mark_Yedinak]

I haven't looked at the code and can't at the moment but if you are implementing the producer/consumer architecture I would place the state information in the state machine and not the event structute. It will be easier to do the timing control should you decide to implement it in the state machine. In addition, all of your state data will be contained there and not spread across your architecture.

[superfunk]

Ok! I will work on that and get back to you in case of trouble!