thanks Malcolm!
I am new to Haskell and wxhaskell.
I want to get a string from one text box,process it  on button click and show the result  in another test box on the same window.
stxt    <- textEntry p [enabled := True]
 textlog <- textCtrl p [enabled := False, wrap := WrapNone]
    -- use text control as logger
       textCtrlMakeLogActiveTarget textlog
       mytext  <- textCtrlGetValue stxt
       eval   <- button p [text := "Process", on command := logMessage mytext]

Do you mean I need to define an event handler explicitly indicating the end of input.which event??

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