When pointing at a canvas, a little arrow appears. It would be nice if we could get the 2D coordinates of that arrow within the canvas, without having to worry about determining what input/raycast method generated it. In theory Unity has plenty of ways of doing this, but I don't know of any of them that are exposed to UdonBehaviour. (The closest that I've gotten is to cover the canvas in a giant slider, which at least gives you the X coordinate of any clicks on the canvas, but trying to add a second rotated slider to get the Y coordinate just covers up the X one...)