how can I make mouseevent only when I cross shape(made by lineTo(),not whole canvas)?

var canvas_attic = document.getElementById('attic');
            var context_attic = canvas_attic.getContext('2d');
            canvas_attic.addEventListener('mousemove', function(evt) {
                context_attic.fillStyle = "rgb(500,0,0)";
                context_attic.fill();
            }, false);
 
            context_attic.beginPath();
            context_attic.moveTo(17,100);
 
            context_attic.lineTo(262,2);
            context_attic.lineTo(322,53);
            context_attic.lineTo(400,53);
            context_attic.lineTo(570,138);
            context_attic.lineTo(570,170);
            context_attic.lineTo(407,198);
            context_attic.lineTo(17,178);
 
 
            context_attic.closePath();
            context_attic.lineWidth = 1;
            context_attic.strokeStyle = 'blue';
            context_attic.stroke();
            context_attic.fillStyle = "rgb(200,0,0)";
            context_attic.fill();