Function hitTest

packages/fairygui/src/display/DisplayObject.ts:564–585

* Hit test * 碰撞检测

(globalX: number, globalY: number)

     * 碰撞检测
     */
    public hitTest(globalX: number, globalY: number): DisplayObject | null {
        if (!this._visible || !this._touchable) {
            return null;
        }

        const localPoint = this.globalToLocal(new Point(globalX, globalY));

        if (
            localPoint.x >= 0 &&
            localPoint.x < this._width &&
            localPoint.y >= 0 &&
            localPoint.y < this._height
        ) {
            for (let i = this._children.length - 1; i >= 0; i--) {
                const hit = this._children[i].hitTest(globalX, globalY);
                if (hit) return hit;
            }
            return this;
        }

        return null;
    }

    // Dirty flags | 脏标记