[Chart 3.0 BUG] xAxis labels disappear after a deep zoom in

[liuxuan30]

xAxis labels disappear after a deep zoom in
Step to reproduce:

1. Open ChartsDemo Time Line Chart
2. zoom in a lot, until the xAxis label disappears

After triage, I found there are two issues:
1: centerAxisLabelsEnabled will be false after entryCount = 1.
Change to below, xAxis.entries will have only 1 entry after zoom in.

    open var centerAxisLabelsEnabled: Bool
    {
        get { return _centerAxisLabelsEnabled && entryCount > 0 }
    }

2: I found in

open func computeAxisValues(min: Double, max: Double)
    ...
    let last = interval == 0.0 ? 0.0 : ChartUtils.nextUp(floor(yMax / interval) * interval
    if interval != 0.0 && last != first // condition is false due to last equals first now
    {
        for _ in stride(from: first, through: last, by: interval)
        {
            n += 1
        }
    }
    ...

After zoom in a lot first and last are the same value, causing n to be default value, which is 1 (centerAxisLabelsEnabled is 1 now instead of 0 because above code change in # 1)

[danielgindi]

That is fixed. However, you should limit the maximum zoom in to a reasonable number.
If the zoom is in to a position where the difference between two axis labels is "0.000000000000001", it's not a zoom that is useful to the user.

[danielgindi]

I guess that by "deep zoom in" you are referring to a zoom so deep the the distance between two labels is zero or close to zero. That's not a usable zoom anyway. Please limit the max zoom in available to the user.

EDIT: Yeah, I meant "Infinite", and for some reason said "zero"

[liuxuan30]

'deep zoom in' means zoom in until you can't see any data entry in a line chart, or in bar chart, zoom in that the view can't hold a single bar.
It's not a usable zoom yes, but guessing if we could do that :)

[castus]

I have the same problem, I have three bars with points (x: 0, y: 1), (x: 1, y: 2), (x: 2, y: 3) and when I'm zooming the whole bar disappears. The same with labels, they disappears even earlier than bars. How to prevent this?