To OP:
The fix is setting canvas width to window.innerWidth * window.devicePixelRatio, and height to window.innerHeight * window.devicePixelRatio. Then use CSS to maximize the canvas on the screen.
The fix is setting canvas width to window.innerWidth * window.devicePixelRatio, and height to window.innerHeight * window.devicePixelRatio. Then use CSS to maximize the canvas on the screen.
Had to take into account the mouse coordinates too since they were not scaled.