function getCanvasPosition(e, canvas) {
    const touches = e.touches;
    const source = touches && touches.length ? touches[0] : e;
    const { offsetX , offsetY  } = source;
    let box = false;
    let x, y;
    if (useOffsetPos(offsetX, offsetY, e.target)) {
        x = offsetX;
        y = offsetY;
    } else {
        const rect = canvas.getBoundingClientRect();
        x = source.clientX - rect.left;
        y = source.clientY - rect.top;
        box = true;
    }
    return {
        x,
        y,
        box
    };
}
@param e
@param canvas
@returns Canvas position