Is it possible to draw a line between points on a TChart "point" chart

Question

An instance of TChart in Delphi does a nice job of making a graph showing points. This is the "Point" series in the TeeChart gallery.

I would like to draw lines between some, but not all, of the points.

For example, image a scatter diagram of points, which is easy to make with Delphi/TChart. My objective is to draw straight lines between some of the points.

Is this possible?

This code works:

With Chart2.ChartRect do
  begin
    Canvas.MoveTo(0,0);
    Canvas.LineTo(500,500);
  end;

The line crosses over the graph, except the line is not visible over the graph. It seems as if the graph much have its own canvas but I can't find any documentation about finding and using it.

So, I need to find the coordinates of some points, as created by TChart, then draw a line between them.

Answer 1

Some options:

1. As David Heffernan said, the best option may be to use a series that supports both line segments and pointers. TLineSeries seems to be the perfect series to do this.

   The problem here is that this series draws a line segment between each two consecutive points. You can make a point to be null with setNull(index) method and this will make the pointer at that index to disappear, but the predecessor and successor line segments will disappear with it.

   The easiest solution could be creating a TMyLineSeries inheriting from TLineSeries to override DrawValue method as explained here.

2. Add a null point after each point you want to be visible. In this option, the only points not followed by a null point would be those where you want a line segment to be drawn.

3. Add a TLineSeries per line segment to be drawn.

4. You always have the possibility to use custom drawing techniques as LU RD said.