ChartJS Zoom Granularity

Question

The data I'm working with has a 'floor' granularity of 'Days'. Anything more fine-grain (e.g. hours) does not make sense. However the ChartJS plugin allows the user to keep zooming to finer scales.

How can I detect that the zoom level has now hit 'Days' and prevent any further zoom-in? I would like to allow zooming from year -> day level but nothing past this.

Answer 1

I solved this with what I consider a hack:

1. Hook into the onZoomStart callback. (docs)
2. Read the values (dates in millis) of the x-axis Ticks (docs)
3. Check if the duration between any two consecutive dates is less than 1day.

Notes:

• If (3) is true then the chart is already at the finest desired granularity
• If event.deltaY > 0 the event is a zoom-out, else zoom-in
  • I only wanted to limit zoom-in, so if the event is a zoom-out I immediately return true