GUI in Scala/Groovy/Clojure

DISCLAIMER: I'm a Clojure programmer. I'm obviously biased.

Of all of those languages, I think Clojure and Groovy are probably the most compact. Scala is a curly-bracket language like Java, so it tends to take up a bit more space. However, it's nowhere near as verbose as Java is, and I think Scala is pretty awesome. I know that Scala has a swing wrapper. I've never done GUI development in Scala, so I can't really say how it feels.

I've done some swing development in Clojure, and it doesn't really take much. Using swing direct from Clojure can be tedious until you write yourself some abstractions, but altogether, swing apps are smaller than the same thing in Java because Clojure code tends to be shorter and more concise than Java code.

Clojure also has some wrappers of sorts to make swing development more Clojury. One of which is clj-swing. I've seen some code written using it, and it's pretty cool, and definitely more concise than direct interop.

Now, I don't know Groovy. I really don't know much of anything about it, but I know it's more compact than Java, so I imagine GUI development would be fairly compact as well.

I think Clojure is a safe bet. With clj-swing, or even directly using the Java GUI toolkits directly is going to be really compact compared to Java, and the ability to build abstractions over non-compact stuff with macros is definitely a huge plus. Clojure has my vote.

Groovy has something called the swing builder for making GUI programming easier. Here is a piece of sample code from the groovy website, it creates a frame with a button and counts the number of times you click it:

int count = 0
new SwingBuilder().edt {
  frame(title:'Frame', size:[300,300], show: true) {
    borderLayout()
    textlabel = label(text:"Click the button!", constraints: BL.NORTH)
    button(text:'Click Me',
         actionPerformed: {count++; textlabel.text = "Clicked ${count} time(s)."; println "clicked"},
         constraints:BL.SOUTH)
  }
}

Groovy has the Griffon framework which uses convention over configuration for building GUI apps on the JVM. It's similar to grails/rails but for a rich GUI rather than a web app.

Scala comes with fairly complete sample applications for basic GUI elements, which you can run by typing scala scala.swing.test.UIDemo at the command line. You can browse the source code for them here.

You may also look at this document to get an idea of the design principles behind Scala's Swing wrappers.