On 04/07/11 06:02, Jason Dagit wrote:
Hello,
I'm trying to get some GUI code working on OSX and numerous forums
around the internet keep reiterating that on OSX to correctly handle
GUI events you need to use the original thread allocated to your
process to check for events and to call the Cocoa framework
functionality. Specifically, using a secondary thread (even a bound
thread) is not sufficient with the Cocoa framework.
I looked at the threading documentation in Control.Concurrent for GHC
and it's not clear to me if this is even possible with GHC without
restricting to the non-threaded RTS. This means that using the GUI
library from GHCI is not an option and using multiple OS threads in
the final application is also not possible. This means that some FFI
libraries will be unusable.
In a compiled program, the main thread is a bound thread, bound to the
main OS thread of the process (i.e. the GUI thread in your case). So
you can safely make Cocoa calls using the main thread of your compiled
Haskell program, and from other threads if you add some way to forward
operations to the main thread, like gtk2hs's postGUI.
In GHCi it's a different matter, because the main thread is running GHCi
itself, and all the expressions/statements typed at the prompt are run
in forkIO'd threads (a new one for each statement, in fact). If you
want a way to run command-line operations in the main thread, please
submit a feature request. I'm not sure it can be done, but I'll look
into it.
Cheers,
Simon
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