Since this is unsolved and maybe the answer to @Par0l or someone else, here is what I would do.
I see that you are calling “self” as reference then you are getting the position from the canvas slot and setting Position A on Draw Line. The problem is that “draw line” is not using viewport as reference for coordinates, but the widget that are being painted.
In other words, if you want to draw a line that starts at this widget position and go to a target widget, then draw a line with position A coordinates as “0,0”, and position B should be “Target widget>slot as canvas slot>get position” minus “Self>slot as canvas slot>get position”.
