DateTimePoint problem when MinLimit and MaxLimit is null

[j-stuemp]

Describe the bug
Infinite loop when there is only one DateTimePoint in the Series and MinLimit / MaxLimit is null

To Reproduce
Steps to reproduce the behavior:

Replace samples\ViewModelsSamples\Lines\AutoUpdate\ViewModel.cs with this code and then press "Add" in Lines/Autoupdate sample :

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using LiveChartsCore;
using LiveChartsCore.Defaults;
using LiveChartsCore.SkiaSharpView;

namespace ViewModelsSamples.Lines.AutoUpdate;

[ObservableObject]
public partial class ViewModel
{
    private readonly Random _random = new();
    private readonly ObservableCollection<DateTimePoint> _observableValues;

    public ViewModel()
    {
        // Use ObservableCollections to let the chart listen for changes (or any INotifyCollectionChanged). // mark
        _observableValues = new ObservableCollection<DateTimePoint>
        {

        };

        Series = new ObservableCollection<ISeries>
        {
            new LineSeries<DateTimePoint>
            {
                Values = _observableValues,
                Fill = null
            }
        };

        // in the following sample notice that the type int does not implement INotifyPropertyChanged
        // and our Series.Values property is of type List<T>
        // List<T> does not implement INotifyCollectionChanged
        // this means the following series is not listening for changes.
        // Series.Add(new ColumnSeries<int> { Values = new List<int> { 2, 4, 6, 1, 7, -2 } }); // mark
    }

    public ObservableCollection<ISeries> Series { get; set; }

    [ICommand]
    public void AddItem()
    {
        var randomValue = _random.Next(1, 10);
        _observableValues.Add(new DateTimePoint(DateTime.Now,randomValue));
    }

    [ICommand]
    public void RemoveItem()
    {
        if (_observableValues.Count == 0) return;
        _observableValues.RemoveAt(0);
    }

    [ICommand]
    public void UpdateItem()
    {
        var randomValue = _random.Next(1, 10);

        // we grab the last instance in our collection
        var lastInstance = _observableValues[_observableValues.Count - 1];

        // finally modify the value property and the chart is updated!
        lastInstance.Value = randomValue;
    }

    [ICommand]
    public void ReplaceItem()
    {
        var randomValue = _random.Next(1, 10);
        var randomIndex = _random.Next(0, _observableValues.Count - 1);
        _observableValues[randomIndex] = new DateTimePoint(DateTime.Now, randomValue);
    }

    [ICommand]
    public void AddSeries()
    {
        //  for this sample only 5 series are supported.
        if (Series.Count == 5) return;

        Series.Add(
            new LineSeries<int>
            {
                Values = new List<int>
                {
                    _random.Next(0, 10),
                    _random.Next(0, 10),
                    _random.Next(0, 10)
                }
            });
    }

    [ICommand]
    public void RemoveSeries()
    {
        if (Series.Count == 1) return;

        Series.RemoveAt(Series.Count - 1);
    }
}

Expected behavior
No infinite loop

Additional context
It seems that there is a problem with double precision in src\LiveChartsCore\Axis.cs function GetPossibleSize

for (var i = start; i <= max; i += s)

when i increments (s = 1) then it has the same value as before

Immediate window:

(long)i
637958911297489152

s
1

(long)((double)i + (double)s)
637958911297489152

(long)i + (long)s
637958911297489153

[beto-rodriguez]

thanks for the report!

The referenced commit fixes the throw, but there are a couple of issues I would like to investigate before closing this issue.

This fix will be included since version beta.360, but I will keep this open to keep investigating.

[beto-rodriguez]

At this point, it does not throw, but we can get strange labels depending on the Axis.UnitWidth and the Series.GeometrySize properties.