Zoom/Pan constraints

Processing Coding Questions
4

Then it would probably be best just not to make the zooming relative to the mouse, but relative to the center of the window instead.

So, instead of adding mouseX and mouseY to translateX and translateY, add width / 2 and height / 2. Also, to limit your zooming, introduce the variables ZOOM_MN and ZOOM_MAX and set them to whatever value you like:

final float ZOOM_MIN = 0.2, ZOOM_MAX = 5;

Finally, perform some tests in mouseWheel to see if the user has zoomed out to far. This is how the method should look like:

void mouseWheel(MouseEvent e) {
  float p = -e.getCount()/10.0;

  if (p < 0) {
    if (scale <= ZOOM_MIN)
      return;
  } else if (scale >= ZOOM_MAX)
    return;

  float delta = pow(2, p), w = width /2, h = height / 2;
  translateX -= w;
  translateY -= h;
  scale *= delta;
  translateX *= delta;
  translateY *= delta;
  translateX += w;
  translateY += h;
}