function draw() {
    var draw = false;
    var context = document.getElementById('desc');
    canvas = context.getContext('2d');

    context.addEventListener('mousedown', function() {
        draw=true;
        canvas.beginPath();
    },false);

    context.addEventListener('mouseup', function() {
        draw=false;
    },false);

    context.addEventListener('mousemove', function(e) {
        if (draw==true) {
            canvas.lineWidth=5;
            canvas.lineCap='round';

            var x,y;
            x=e.pageX;
            y=e.pageY;

            setTimeout(function(){
                canvas.lineTo(x - context.offsetLeft, y - context.offsetTop);
                canvas.moveTo(x - context.offsetLeft, y - context.offsetTop);
                canvas.stroke();
            },1);
        }
    });
}