From Xojo Documentation
The number of off-curve control points that are used.
It is one of the following values:
|0||A straight line from x,y to x2,y2 is used.|
|1||A quadratic Bezier curve is drawn using one control point.|
|2||A cubic Bezier curve is drawn using two control points.|
The following method is in the MouseDown event of a Window. It draws a simple curve when the user presses the mouse button. The negative value of ControlY(0) places the control point above the imaginary straight line from x,y to x2,y2.