Signal: GetPointNearestX()

[swharden]

Current behavior described by @dhgigisoave in #1987 sounds like a "floor" effect

ScottPlot/src/ScottPlot4/ScottPlot/Plottable/SignalPlotBase.cs

Lines 826 to 835 in 9ff29e2

	/// <summary>
	/// Return the index for the data point corresponding to the given X coordinate
	/// </summary>
	private int GetIndexForX(double x)
	{
	int index = (int)((x - OffsetX) / SampleRate);
	index = Math.Max(index, MinRenderIndex);
	index = Math.Min(index, MaxRenderIndex);
	return index;
	}

I think the solution here is to add one half of the sample period to the given x before finding its index...

[swharden]

I think the solution here is to add one half of the sample period to the given x before finding its index...

Yep, that did the trick! 🚀

Before	After

public partial class Form1 : Form
{
    ScottPlot.Plottable.SignalPlot Signal;
    ScottPlot.Plottable.MarkerPlot Marker;

    public Form1()
    {
        InitializeComponent();
        Signal = formsPlot1.Plot.AddSignal(DataGen.Sin(51));
        Marker = formsPlot1.Plot.AddMarker(0, 0, MarkerShape.openCircle, 10, Color.Red);
        formsPlot1.MouseMove += FormsPlot1_MouseMove;
        formsPlot1.Render();
    }

    private void FormsPlot1_MouseMove(object sender, MouseEventArgs e)
    {
        (double x, double y) = formsPlot1.GetMouseCoordinates();
        (double ptX, double ptY, int index) = Signal.GetPointNearestX(x);

        Marker.X = ptX;
        Marker.Y = ptY;
        formsPlot1.Render();
    }
}