Re: [wxhaskell-users] event objects

[Robert D. <rob...@fa...>]

On Feb 23, 2006, at 1:03 PM, Anatoly Zaretsky wrote:

> On 2/23/06, Robert Dockins <rob...@fa...> wrote:
>>
>> How would one go about adding them?  I'm not familiar with the how
>> WxEiffel and the WxHaskell build system works.  Is there a particular
>> reason they aren't exposed already?
>
> WxHaskell uses wxc part of wxEiffel -- basically, C wrappers around
> C++ classes methods. And as far as I know wxEiffel doesn't evolve
> anymore, so there's noone to add wrappers for missing classes.


OK.  So its not likely to happen soon unless I decide to do it...


>> I'm not sure I fully understand, so let me paraphrase and see if I've
>> got this right:
>>
>> 'makeEvent' takes an object which can handle events and returns a
>> pair where
>>    -- the first element triggers an event by via the menu event
>> handler on the passed in object
>>    -- the second element lets you set the event handler
>
> Exactly. I am sorry for omitting the description. Just to note: every
> makeEvent generates distinct event object.
>
>> If you want to pass additional data beyond the simple occurance of
>> the event, you need external concurrency primitives.
>
> Yes, but I personaly think that passing haskell data between haskell
> threads through C-land is less natural (and heavier) than using native
> primitives.

Yeah, it just brings up thorny questions about synchronizing what are  
essentially two parallel message queues.  I know that a Chan will  
guarantee inorder delivery without dropped messages, but I don't know  
what the properties of the wx event queues are.  Is it possible that  
they could become out of sync?  I don't want to deadlock because wx  
dropped an event, and I'll have to be pretty careful if events can be  
delivered out-of-order.

Thanks again.


Rob Dockins

Speak softly and drive a Sherman tank.
Laugh hard; it's a long way to the bank.
           -- TMBG