Re: [wxhaskell-users] event objects

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

On Feb 23, 2006, at 6:33 AM, Anatoly Zaretsky wrote:

> On 2/20/06, Robert Dockins <rob...@fa...> wrote:
>>
>>> There don't appear to be constructors for these object types.
>>>
>>> For example, KeyEvent
>>> (http://wxhaskell.sourceforge.net/doc/
>>> Graphics.UI.WXCore.WxcClassesAL.html#99)
>>> doesn't have the expected 'keyEventCreate' funciton and PaintEvent,
>>> which
>>> only has a constructor, doesn't appear in the function listings at
>>> all.
>>
>
> Hi!
>
> It's not very difficult to add them though the entire Haskell part of
> wxHaskell should be rebuilt then.

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?

> But if you need some custom events
> you can use the following hack (trick, technique...):

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

If you want to pass additional data beyond the simple occurance of  
the event, you need external concurrency primitives.


> import Control.Concurrent.Chan
> import Graphics.UI.WX
> import Graphics.UI.WXCore
>
> makeEvent :: EvtHandler a -> IO (IO (), IO () -> IO ())
> makeEvent target =
>   do
>     id <- idCreate
>     evt <- commandEventCreate wxEVT_COMMAND_MENU_SELECTED id
>     let sender = evtHandlerAddPendingEvent target evt
>         binder = evtHandlerOnMenuCommand target id
>     return (sender, binder)
>
> gui = do
>   f <- frame [text := "Some frame"]
>
>   let newFrameEvent = makeEvent f
>   (oneThreadReport, reactToOneThread) <- newFrameEvent
>   (anotherOneReport, reactToAnotherThread) <- newFrameEvent
>
>   reactToOneThread (putStrLn "OneThread sent event")
>
>   dataChan <- newChan
>   reactToAnotherThread $ do
>     d <- readChan dataChan
>     putStrLn ("Data from AnotherThread: " ++ show d)
>
>   createOneThread oneThreadReport
>   createAnotherOne anotherOneReport dataChan
>
> Performing those report actions threads can send events.
>
> My program worked properly only with threaded rts, possibly because
> addPendingEvent performs mutex locking. I am not sure about the exact
> reason, 'cause there was also some network I/O.

Ahh.  That's unfortunate.  I'll have to think on this.


Thank you for your reply!


Rob Dockins

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