Prevent one Processing window from closing others

Processing Coding Questions
5

I’ve done some digging – inspired by @GoToLoop and @quark – and have found a solution.

Closing sketches in P2D and JAVA2D renderer modes calls the PApplet instance’s exitActual() method, which contains the line System.exit(0) – a static method – which terminates the currently running Java virtual machine.

Overriding exitActual() with nothing (i.e. preventing the call to System.exit(0)) prevents sketches from closing others, fixing the issue, but introduces another problem in the case of P2D sketches: the window is not disposed properly when the cross is clicked.

Solution:

Override exitActual() to prevent the JVM (and all sketches) closing when one sketch is closed.

@Override
public void exitActual() {
}

Introduce the following code (suitable in setup()) such that P2D sketches are disposed properly:

if (getGraphics().isGL()) {
		final com.jogamp.newt.Window w = (com.jogamp.newt.Window) getSurface().getNative();
		w.setDefaultCloseOperation(WindowClosingMode.DISPOSE_ON_CLOSE);
}

However, in overriding (preventing) the call to System.exit(0), another issue is introduced: even after all sketches (windows) are closed, the JVM will continue to run in memory. Ideally System.exit(0) should be called but only when the last remaining window is disposed.

I propose a rudimentary fix below – a simple counter – but I wonder whether it is possible to inspect the JVM to see the number of live instances of JavaFX/NEWT/AWT windows, using those values instead?

@Override
public void exitActual() {
	if (Benchmark.n == 1) {
			System.exit(0);
	}
	Benchmark.n--;
}

public class Benchmark {

	public static int n = 3;

	public static void main(String[] args) {

		Sketch sketch1 = new Sketch(PApplet.FX2D);
		Sketch sketch2 = new Sketch(PApplet.P2D);
		Sketch sketch3 = new Sketch(PApplet.JAVA2D);
		PApplet.runSketch(new String[] { "--location=760,0", "" }, sketch1);
		PApplet.runSketch(new String[] { "--location=760,80", "" }, sketch2);
		PApplet.runSketch(new String[] { "--location=760,160", "" }, sketch3);
	}
}
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