I'm building a Haskell desktop app over winter break (DMX and light show controls), but after a fair bit of research, I came to the conclusion that its best to do the GUI in JavaScript and speak with a Haskell server over a WebSocket.
The package is on hackage[3] and has a website[4], but the github seemed more approachable/clear to me. There's also an awesome tutorial on making tic tac toe[5] by ocharles of the 24 days of hackage fame.
0: https://github.com/benl23x5/gloss
1: https://github.com/benl23x5/gloss/blob/master/gloss-examples...
2: https://github.com/benl23x5/gloss/blob/master/gloss-examples
3: http://hackage.haskell.org/package/gloss
4: http://gloss.ouroborus.net/
5: https://ocharles.org.uk/blog/posts/2013-12-10-24-days-of-hac...