Drag zoom loosing data points

Hi

I am working on an implementation of the zoom plugin using the drag feature. I am following the samples/zoom-time.html example. When i drag a zoom area, the resulting line chart looses data points. This happens in both my chart and the example chart.

Drag:

Result:

As you can see the first data point is gone and the resulting chart is off too. The result in mine is even more extreme with more of a flattening line. It kind of looks like the chart data is averaged instead of zoomed.

Here is the zoom config I am using:

zoom: {
  enabled: true,
  drag: true,
  mode: 'x',
  limits: {
    max: 10,
    min: 0.5
  }
}

limits was in the example but I do not see in in chart.zoom.js

I’d love some help here 😃

Thanks,

Jordan

[marco-silva0000]

any progress on this?

[chriser-]

The usage of the zoom functions when using the drag selection is pretty stupid, there is already a good function to get the value at a pixel. I refactored the mouse up handler, and it works perfectly now with a time graph. I haven’t tested it with non-time graphs, but it should work exactly the same.

     chartInstance.zoom._mouseUpHandler = function(event){
        if (chartInstance.zoom._dragZoomStart) {
          helpers.each(chartInstance.scales, function(scale, id) {
            if(scale.isHorizontal()) {
              var beginPoint = chartInstance.zoom._dragZoomStart;
              var offsetX = beginPoint.target.getBoundingClientRect().left;
              var startX = Math.min(beginPoint.clientX, event.clientX) - offsetX;
              var endX = Math.max(beginPoint.clientX, event.clientX) - offsetX;
              var limitObject = scale.options.type == 'time' ? scale.options.time : scale.options.ticks;
              limitObject.min = scale.getValueForPixel(startX);
              limitObject.max = scale.getValueForPixel(endX);
            }
          });
          chartInstance.zoom._dragZoomStart = null;
          chartInstance.zoom._dragZoomEnd = null;
        }
      };

If someone wants to submit a PR or fix it better, feel free to do so.