gistfile1.txt

let get_mouse_pos (canvas:Html.canvasElement) event =
    let rect = canvas##getBoundingClientRect() in
    let top = rect##.top
    and bottom = rect##.bottom
    and right = rect##.right
    and left = rect##.left
    and clientX = event##.clientX
    and clientY = event##.clientY
    and width = canvas##.width
    and height = canvas##.height in
    let x = (clientX - left)/(right - left)*width
    and y = (clientY - top)/(bottom - top)*height
    in x, y
;;