Lemmih wrote: > On 12/4/06, Thorsten Seitz <[EMAIL PROTECTED]> wrote: >> Hello, >> >> I'm very intrigued by the concepts of STM but I'm having difficulties >> to see >> how a TVar based model can be used by a GUI application (e.g. Gtk2hs): >> >> For example, I'd like to update the GUI (e.g. changing widget >> sensitivity) >> upon changes in the model. >> But changing the sensitivity of a widget is an IO operation which >> cannot be >> initiated atomically by a model change which is an STM operation. >> Therefore >> the GUI change cannot be executed atomically together with the model >> change. >> This means for example that I can still press a button although the >> model has >> changed such that the button action is not allowed anymore. All I can >> do is >> check the condition of the model when the button is pressed and then >> ignore >> the button press which is not very satisfying for the user. >> >> Is it simply not appropriate to use TVar based models in a GUI >> application? >> Maybe STM should be more used like a service for MVar based GUI models? > > How about making a list of IO actions to be executed when the > transaction commits? >
That onCommit list and its execution can be done by using the slightly modified/enhanced/wrapped AdvSTM monad. A complex example that also can queue actions on retry is at http://haskell.org/haskellwiki/?title=New_monads/MonadAdvSTM#Helper_Thread_Code But for just onCommit the simpler code at http://haskell.org/haskellwiki/New_monads/MonadAdvSTM#Just_onCommit should work. Cheers, Chris _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
