Method getLineIntersectionPoint

packages/shapes/src/Rectangle.ts:358–380

* 返回一个线段和这个矩形的交点，如果没有交点，就返回这个矩形的中心点 * 请确保线段和矩形只有一个交点，出现两个交点的情况还未测试

(line: Line)

   * 请确保线段和矩形只有一个交点，出现两个交点的情况还未测试
   */
  public getLineIntersectionPoint(line: Line) {
    const topLine = new Line(this.location, this.location.add(new Vector(this.size.x, 0)));
    const topIntersection = topLine.getIntersection(line);
    if (topIntersection) {
      return topIntersection;
    }
    const bottomLine = new Line(this.location.add(new Vector(0, this.size.y)), this.location.add(this.size));
    const bottomIntersection = bottomLine.getIntersection(line);
    if (bottomIntersection) {
      return bottomIntersection;
    }
    const leftLine = new Line(this.location, this.location.add(new Vector(0, this.size.y)));
    const leftIntersection = leftLine.getIntersection(line);
    if (leftIntersection) {
      return leftIntersection;
    }
    const rightLine = new Line(this.location.add(new Vector(this.size.x, 0)), this.location.add(this.size));
    const rightIntersection = rightLine.getIntersection(line);
    if (rightIntersection) {
      return rightIntersection;
    }
    return this.getCenter();
  }

  /**
   * 获取在this矩形边上的point的单位法向量,若point不在this矩形边上，则该函数可能返回任意向量。