resolve #4751.

I inherited class of Text Plot and added the graphic rendering part of Tooltip.

Since RenderTooltipShape() is designed to be protected virtual, users can implement custom subclasses if they have different ideas about the current design. 😉

The current design requires the tail target coordinates to be specified and will automatically rotate in the target direction.

Customizable tooltip tail width percentage.
The actual width of the tail is the lesser of the length or width of the tooltip body.

The image below shows the actual shape of the tail profile.

demo image

demo code

Coordinates origin = new(0, 0);
for (int i = 360; i > 0; i -= 30)
{
    PolarCoordinates polar = new(i + 1, Angle.FromDegrees(i));
    var tooltip = formsPlot1.Plot.Add.Tooltip($"{i}", polar.ToCartesian(), origin);
    tooltip.Alignment = Alignment.MiddleCenter;
    tooltip.FillColor = Colors.Red.WithAlpha(0.5);
    tooltip.LineColor = Colors.Black.WithAlpha(0.5);
    tooltip.LineWidth = 5;
}