add isFixedSize implementation

Yuhang Zhao

2023-12-05 d02f3b0bc32f711bf33a7fd288185963e9e96189

 src/quick/quickwindowagent_p.h

@@ -10,12 +10,12 @@
        Q_DECLARE_PUBLIC(QuickWindowAgent)
    public:
        QuickWindowAgentPrivate();
        ~QuickWindowAgentPrivate();
        ~QuickWindowAgentPrivate() override;

        void init();

        // Host
        QQuickWindow *host{};
        QQuickWindow *hostWindow{};
    };

}