sclass Canvas extends ImageSurface {

  O makeImg;

  bool updating;

  *() { zoomable = false; }

  *(O makeImg) { this(); this.makeImg = makeImg; }

  void update() { updateCanvas(this, makeImg); }

}

static Canvas jcanvas() { ret jcanvas(null, 0); }

// f: (int w, int h) -> BufferedImage

static Canvas jcanvas(O f) {

  ret jcanvas(f, 0); // 100

}

static Canvas jcanvas(fO f, final int updateDelay) {

  ret (Canvas) swing(func {

    final Canvas is = new Canvas(f);

    is.specialPurposed = true;

    final Runnable update = new Runnable {

      bool first = true;

      public void run {

        BufferedImage img = is.getImage();

        int w = is.getWidth(), h = is.getHeight();

        if (first || img.getWidth() != w || img.getHeight() != h) {

          updateCanvas(is, f);

          first = false;

        }

      }

    };

    onResize(is, r { awtLater(is, updateDelay, update) });

    bindToComponent(is, update); // first update

    ret is;

  });

}