在context中关于clip()影响到lineWidth的问题

Question

使用javascript对canvas画图的时候遇到的问题

 var canvas = document.getElementById("canvas");
        var context = canvas.getContext("2d");

        context.beginPath();
        context.arc(canvas.width/2, canvas.height/2, 50, 0, Math.PI*2, false);
        context.clip();
        context.lineWidth = 10;
        context.closePath();    //为什么去掉这两行之后才能够显示出lineWidth为10的边界
        context.beginPath();    //还有这一行
        context.fillStyle = "red";
        context.fillRect(0, 0, canvas.width, canvas.height);
        context.stroke();
        context.closePath();

Answer 1

http://www.tuicool.com/articles/6zYZRb