svoid testDirectlyPaintingOnJComponent(int w default 256) {

  int h = w;

  var c = //jcenteredlabel("Bla");

    new JComponent {};

  setOpaqueBackground(Color.white, c);

  jMinSize(c, w, h);

  var it = WeightlessShuffledIteratorWithSeed<Pt>(virtualList(w*h, i -> pt(i%w, i/w)));

  new Var<Graphics2D> g;

  new Flag done;

  double timeToFinish = 2; // seconds

  int pixelsPerMS = iceilRatio(w*h/100, timeToFinish);

  awtEvery(c, 10, -> {

    if (!g.has()) {

      g.set((Graphics2D) c.getGraphics());

      if (!g.has()) ret;

    }

    repeat pixelsPerMS {

      if (!it.hasNext()) {

        if (done.raise())

          print("Done painting " + nPixels(w*h));

        break;

      }

      var p = it.next();

      //print(+p);

      setPixel(g!, p, Color.black);

    }

  });

  showFrame(c);

}