plain mouse events

sketch.js

    var down = false;
    canvas.addEventListener('mousedown', function (e) {
        down = true;
        ctx.beginPath();
        ctx.moveTo(e.clientX, e.clientY);
    }, false);
    window.addEventListener('mousemove', function (e) {
        if (!down) return;
        console.log(e.clientX, e.clientY);
        ctx.lineTo(e.clientX, e.clientY);
        ctx.stroke();
    }, false);
    window.addEventListener('mouseup', function (e) {
        if (!down) return;
        ctx.lineTo(e.clientX, e.clientY);
        ctx.stroke();
        ctx.closePath();
        down = false;
    }, false);