(defmacro with-action [component & body]
`(. ~component addActionListener
(proxy [java.awt.event.ActionListener] []
(actionPerformed [~'event] ~@body))))

Yes, of course running multiple CPU intensive things at the same time will slow the machine down. What I meant was that it seemed not to be updating the display at 0.1s intervals anymore, but I suppose it could also be that the values were taking longer than 0.1s to update and if so, I wouldn’t be able to tell the difference :) I suppose part of my problem is that I have a single core machine.

One solution is to assign the flipper to a global Var, so that all the windows connect to the same flipper.

Another way is to automatically stop the flipper when the window is closed. This is easy enough. We need to add a WindowListener on the JFrame. Insert the following lines just above (.pack) in the flipper-app function:

(.addWindowListener
 (proxy [java.awt.event.WindowListener] []
   (windowActivated [e])
   (windowClosed [e])
   (windowClosing [e]
                  (send flipper stop)
                  (.stop timer))
   (windowDeactivated [e])
   (windowDeiconified [e])
   (windowIconified [e])
   (windowOpened [e])))

As to your second question, running multiple instances of any CPU-intensive process will be slow.

In fact, Clojure puts more strain on the system because it makes full use of all your CPU cores. That’s good if you want your computation to finish faster, not so good if you want to leave some CPU for other applications.

Clojure doesn’t provide a way to explicitly control how many cores it uses, but it could someday. Some operating systems also allow you to restrict the number of cores a process can use. As multi-threaded programming becomes more prevalent, CPU resource management should be more accessible.

I’ve noticed that the agent seems to carry on running if you just close the window without first clicking on Stop. So if you run it once and close the window while it’s running, then do it again, the second instance will be slower. If you keep on doing this, Java uses more and more CPU and the running instance of the app gets slower and slower.

How would one arrange for (send flipper stop) to be called when the window is closed?

Also, if you run multiple instances of the app at the same time, they get really slow too. I suppose you wouldn’t normally run two instances of something like this at the same time, but there might be two windows doing something different from each other that you want to be able to run concurrently. Any thoughts on this?

Raph