Line Plot: Show position label on axis

Feature description:

It would be very nice to have the posibility of tooltip for Draggable axis similar to crosshair tooltip #1093

VLine vLine = new VLine();
vLine = formsPlot.Plot.AddVerticalLine(0);
vLine.DragEnabled = true;
vLine.LabelEnabled = true;   // new

HLine hLine = new HLine();
hLine = formsPlot.Plot.AddHorizontalLine(0);
hLine.DragEnabled = true;
hLine.LabelEnabled = true;   // new

[swharden]

Very quick question Scott before I start coding, is there a performance impact due to drawing the PositionLabel?

Technically yes, but it’s extremely minor. The difference is effectively negligible 👍

[swharden]

Thanks for the suggestion @EmanuelFeru! This one took me a while to get to, but I’m finally making progress. I’m combining this with crosshair refactoring #1173, and it looks like we’ll have something pretty similar to this shortly:

var plt = new ScottPlot.Plot(400, 300);
plt.AddSignal(DataGen.Sin(51));
plt.AddSignal(DataGen.Cos(51));

var hline = plt.AddHorizontalLine(.85);
hline.LineWidth = 2;
hline.PositionLabel = true;
hline.PositionLabelBackground = hline.Color;
hline.DragEnabled = true;

var vline = plt.AddVerticalLine(23);
vline.LineWidth = 2;
vline.PositionLabel = true;
vline.PositionLabelBackground = vline.Color;
vline.DragEnabled = true;

Func<double, string> xFormatter = x => $"X={x:F2}";
vline.PositionFormatter = xFormatter;