function launchFullscreen(element) {
            var enabled =
              document.fullscreenEnabled ||
              document.webkitFullscreenEnabled ||
              document.mozFullScreenEnabled ||
              document.msFullscreenEnabled;
            if (!enabled) {
              throw new Error('Fullscreen not enabled in this browser.');
            }
            if (element.requestFullscreen) {
              element.requestFullscreen();
            } else if (element.mozRequestFullScreen) {
              element.mozRequestFullScreen();
            } else if (element.webkitRequestFullscreen) {
              element.webkitRequestFullscreen();
            } else if (element.msRequestFullscreen) {
              element.msRequestFullscreen();
            }
          }
Returns the pixel density of the current display the sketch is running on.

@method displayDensity
@returns {Number} current pixel density of the display
@example
<div>
<code>
function setup() {
  let density = displayDensity();
  pixelDensity(density);
  createCanvas(100, 100);
  background(200);
  ellipse(width / 2, height / 2, 50, 50);
}
</code>
</div>

@alt
50x50 white ellipse with black outline in center of canvas.