Connecting points

You can only connect the existing points; the end of a line can't be placed outside the point. Therefore you don't have to worry about the correct "connecting point", the program doesn’t allow other lines placing. After connecting to a point, the program starts to draw a line from the point to the current cursor position. The line automatically changes with the moving of the cursor. If you place it by connecting to the end point, you can terminate drawing by pressing the right mouse button.