Re: [wxhaskell-users] Using modifier keys with character keys.

[Tom O. <tos...@gm...>]

Hi Henk-Jan,

Thanks for the snippet of code you submitted; it did the main part right, 
which was identifying whether or not a modifier and a key was pressed.

However, and I'm not sure what the source of this problem is, whenever I 
use the constructor (KeyChar c), where c is a character, I don't get a 
value of type Key that represents the key at character c. To make this 
problem more concrete, I have submitted the following sample application 
which can be ran and tested to demonstrate what I mean:


module Main where

import Graphics.UI.WX
import Graphics.UI.WXCore

handleKeyboard :: Frame a -> EventKey -> IO()
handleKeyboard f k =
     if controlKeyPressed
     then keyTestModifiers f (ks)
     else infoDialog f "info" "No ctrl-<key> combo activated"
         where
             controlKeyPressed = keyModifiers k == Modifiers False False 
True False
             ks                = keyKey k

keyTestModifiers :: Frame a -> Key -> IO()
keyTestModifiers f k
     | k == (KeyChar 't') = infoDialog f "info" "Test: Ctrl-t activated"
     | k == (KeyReturn)   = infoDialog f "info" "Test: Ctrl-Enter 
activated"
     | otherwise          = infoDialog f "info" "Test: Different key 
activated"

main :: IO ()
main = start gui

gui :: IO ()
gui = do
     f <- frameFixed [text := "test"]
     p <- panel f []

     set p [on keyboard := handleKeyboard f]

Notice that if you compile and  run this application and hit n, where n is 
any keyboard value, you get the expected response (A dialog saying "No 
Ctrl-key combo activated" pops up). Likewise, if you hit Ctrl-Enter, you 
get the expected response ("Test: Ctrl-Enter activated"). However, when 
you enter Ctrl-t, even though Ctrl-t should be defined, it returns 
"Test: Different Key Activated" instead of "Test: Ctrl-t activated"!

I'm not sure why does it do this, but judging by the code snippet you 
presented, this shouldn't be expected behaviour.

Regards,

Tom Ostojich