Creating a Clojure GUI Application with SWT

In my explorations of Clojure, I have been developing a desktop GUI application that uses SWT, the graphics toolkit that Eclipse uses. Once you get going, SWT is fairly intuitive to program in with Clojure, but you might need a little help to get started. Here is an example of a barebones app in SWT:

(ns swttest
(:import (org.eclipse.swt.widgets Display Shell)
        (org.eclipse.swt.layout GridLayout)
        (org.eclipse.swt.events ShellAdapter)))

(defn create-shell [display shell]
(let [layout (GridLayout.)]
 (doto shell
   (.setText "SWT Test")
   (.setLayout layout)
   (.addShellListener
    (proxy [ShellAdapter] []
      (shellClosed [evt]
        (System/exit 0)))))))

(defn swt-loop [display shell]
(loop []
 (if (.isDisposed shell)
   (.dispose display)
   (do
     (if (not (.readAndDispatch display))
       (.sleep display))
     (recur)))))

(defn begin []
 (let [display (Display.)
       shell (Shell. display)]
   (create-shell display shell)
   (.setSize shell 700 700)
   (.open shell)
   (swt-loop display shell)))

(begin)

On Mac, you will need to add the "-XstartOnFirstThread" command line option or your application will crash soon after launching.

Update:
I originally left out the line "(create-shell display shell)". The code above is now corrected.

See also:

• SWT FAQ Entry on XstartOnFirstThread
  
• Clojure forum thread with SWT example