let x = 0; // pan X

let y = 0; // pan Y

​

let mx, my; // mouse coords;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  mx = mouseX;

  my = mouseY;

​

  background(255);

​

  translate(mx, my);

  scale(sf);

  translate(-mx, -my);

  translate();

​

  rect(100, 100, 100, 100);

​

  if (mouseIsPressed) {

    x -= pmouseX - mouseX;

    y -= pmouseY - mouseY;

  }

}

​

window.addEventListener("W", function(e) {

  if (e.deltaY > 0)

    sf *= 1.05;

  else

    sf *= 0.95;

});