move a line

[nok]

hello,
How can I move a line? Do I have to draw a line and delete it and then draw a new line with decrement y coordinate. Is there any method for this? I couldn't find any.
thank you for your help

[Tokage]

You should be completely erasing the window and redrawing the line every frame anyway, so you're supposed to just draw the line somewhere else in the next frame. OpenGL doesn't remember that the pixels you drew to the screen were a line when you drew them, so you can't exactly "move" them after they've been drawn.