parallel channel in Highstock does not work in logarithmic mode

[anoosurf]

Expected behaviour

when drawing a parallel channel the chart should take into accoun the logarithmic scale and appear parallel to end user even in that case.. that is how stock trader would use

Actual behaviour

when in logarithmic mode, it gets skewed which is incorrect

Live demo with steps to reproduce

https://jsfiddle.net/anoosurf/uzwvrhjt/3/

Product version

highcharts /highstock 9.3.2

Affected browser(s)

[raf18seb]

Hi @anoosurf, thank you for reporting a bug!

Internal note:

• When fixing for a parallel channel, check other annotations too.

[pawelfus]

Workaround:
Demo: https://jsfiddle.net/BlackLabel/o93v7quz/
Plugin:

(function(H) {
  H.wrap(
    H.Annotation.types.tunnel.prototype,
    'getPointsOptions',
    patch16769
  );

  function patch16769(proceed, ...args) {
    const points = proceed.apply(this, args),
      yAxisIndex = points[0].yAxis,
      yAxis = this.chart.yAxis[yAxisIndex];

    // In case of log axis, translate the bottom left point again
    if (yAxis && yAxis.logarithmic) {
      // Get the height in pixels
      const h = yAxis.toPixels(points[2].y) - yAxis.toPixels(points[1].y),
      // Get the pixel position of the last point
        y3 = yAxis.toPixels(points[0].y) + h;

      // Set the new value
      points[3].y = yAxis.toValue(y3);
    }

    return points;
  }

})(Highcharts);

Internal note:
It's caused by using height to control all bottom points. We simply add height value to the first two points' values in heightPointOptions(). Even though it's mathematically correct, visually we can observe the skew. For example this demo: (tunnel has height=20)