Method windingArc

src/common/overlay/levelRenderer/Area.js:790–847

* @function LevelRenderer.Tool.Areal.prototype.windingArc * // TODO Arc 旋转

(cx, cy, r, startAngle, endAngle, anticlockwise, x, y)

     * // TODO   Arc 旋转
     */
    windingArc(cx, cy, r, startAngle, endAngle, anticlockwise, x, y) {
        var roots = this.roots;
        var PI2 = this.PI2;

        y -= cy;
        if (y > r || y < -r) {
            return 0;
        }
        let tmp = Math.sqrt(r * r - y * y);
        roots[0] = -tmp;
        roots[1] = tmp;

        if (Math.abs(startAngle - endAngle) >= PI2) {
            // Is a circle
            startAngle = 0;
            endAngle = PI2;
            var dir = anticlockwise ? 1 : -1;
            if (x >= roots[0] + cx && x <= roots[1] + cx) {
                return dir;
            } else {
                return 0;
            }
        }

        if (anticlockwise) {
            let tmp = startAngle;
            startAngle = this.normalizeRadian(endAngle);
            endAngle = this.normalizeRadian(tmp);
        } else {
            startAngle = this.normalizeRadian(startAngle);
            endAngle = this.normalizeRadian(endAngle);
        }
        if (startAngle > endAngle) {
            endAngle += PI2;
        }

        var w = 0;
        for (let i = 0; i < 2; i++) {
            var x_ = roots[i];
            if (x_ + cx > x) {
                let angle = Math.atan2(y, x_);
                let dir = anticlockwise ? 1 : -1;
                if (angle < 0) {
                    angle = PI2 + angle;
                }
                if (
                    (angle >= startAngle && angle <= endAngle)
                    || (angle + PI2 >= startAngle && angle + PI2 <= endAngle)
                ) {
                    if (angle > Math.PI / 2 && angle < Math.PI * 1.5) {
                        dir = -dir;
                    }
                    w += dir;
                }
            }
        }
        return w;
    }