How can I make a graphical command line in haskell/gtk2hs? - haskell

Question

I'm trying to create my first "real program" in haskell (something that solves integrals if polynomials) but I'm completely stumped with this part of it:
I want to make something very simple a bit like GHCi:
> user input
program output
> user input
program output
> user input
program output
>
except that my program output is images (using LaTeX to turn mathematical expressions into PNGs) - so I can't do this using System.IO. I think it will be possible with gtk2hs which I've managed to install but I can't figure out how to make this input/output dialogue.
Please show me how it's done if you have the time. Thanks a lot!

Answer 1

We managed to come up with the following solution, thanks to ClaudiusMaximus.
module Main where
import Graphics.UI.Gtk
main = do
initGUI
----------------
win <- windowNew
onDestroy win mainQuit
vb <- vBoxNew False 3
log <- vBoxNew False 2
sc <- scrolledWindowNew Nothing Nothing
scrolledWindowSetPolicy sc PolicyNever PolicyAutomatic
sw <- layoutNew Nothing Nothing
en <- entryNew
----------------
scrolledWindowAddWithViewport sc log
boxPackStart vb sc PackGrow 0
boxPackStart vb en PackNatural 0
set win [ containerChild := vb ]
en `onEntryActivate` do
txt <- entryGetText en
entrySetText en ""
l <- labelNew (Just txt)
boxPackStart log l PackNatural 0
widgetShowAll log
Just ran <- scrolledWindowGetVScrollbar sc
adj <- rangeGetAdjustment ran
max <- adjustmentGetUpper adj
adjustmentSetValue adj max
----------------
widgetShowAll win
mainGUI

Answer 2

I think you should first implement the backend, i.e. the code for parsing a command and creating the output image. If that works, you could then implement the GUI. Basically, you need something light a text entry for input and an text and drawing widget for output. As GUI programming is (IMHO) not trivial, you should first look at some GTK/gtk2hs tutorials / introductions.