I'm running a very simple "hello world" GUI program. (Saved as gui.hs) My code is:
import Graphics.UI.Gtk
main = do
initGUI
window <- windowNew
widgetShowAll window
onDestroy window mainQuit
mainGUI
I compile with: ghc -L/usr/lib gui
It compiles fine, but when I run it I see:
objc[51245]: Class GNotificationCenterDelegate is implemented in both /usr/local/opt/glib/lib/libgio-2.0.0.dylib and /opt/local/lib/libgio-2.0.0.dylib. One of the two will be used. Which one is undefined.
(process:51245): GLib-GObject-WARNING **: gsignal.c:2423: signal 'destroy' is invalid for instance '0x7fe9dc81a0e0' of type '(null)'
The window appears, but it won't quit when I click to close the window. (Window disappears, but the process doesn't terminate.)
This is a very simple example- I've tried making buttons that trigger signals, but I (almost) always get this "signal is invalid" warning.
I'm using Mac OS X El Capitan with GHC 8.4.3 (Haskell platform), and I installed everything following instructions here: (section 2) [https://wiki.haskell.org/Gtk2Hs/Mac]
I am starting to feel like my installation is messed up somehow? Maybe do I need to have installed GHC also with brew? Is there any way I can test the installation (other than trying what I'm already doing)? Are the two runtime warnings related to each other? Thanks for any help!
Self answer: I fixed this by removing the Haskell Platform and reinstalling GHC with brew. Then all worked fine.