Zoom xy proportionally in Highcharts scatter plot

Question

Having a scatterplot:

https://jsfiddle.net/hdq4rc35/

I want to be able to zoom only proportionally xy, so the distance between y ticks is the same as x ticks at any time, resulting in a square zoom field instead of a free rectangle.

I tried chart.setExtremes() but it didn't affect the zoom functionally.

Answer 1

That functionality is not supported in Highcarts by default, but you can add it by wrapping drag method from Pointer prototype, for example:

(function(H) {
  H.wrap(H.Pointer.prototype, 'drag', function(proceed, e) {
    var chartX = e.chartX,
      chartY = e.chartY,
      mouseDownX = this.mouseDownX,
      mouseDownY = this.mouseDownY,
      rectX = Math.abs(chartX - mouseDownX),
      rectY = Math.abs(chartY - mouseDownY);

    if (rectX > rectY) {
      e.chartY = chartY + (
        mouseDownY > chartY ?
        -(rectX - rectY) :
        (rectX - rectY)
      );
    } else {
      e.chartX = chartX + (
        mouseDownX > chartX ?
        -(rectY - rectX) :
        (rectY - rectX)
      );
    }

    proceed.apply(this, Array.prototype.slice.call(arguments, 1));
  });
}(Highcharts));

---

Live demo: https://jsfiddle.net/BlackLabel/aubkLt5o/

API Reference: https://www.highcharts.com/docs/extending-highcharts/extending-highcharts