Improve fixed width/height/size hit testing

Zhao Yuhang

2024-05-23 6002cd46a2c5a1c2c4afdbf8e491e76f68b9bfd8

 examples/mainwindow/mainwindow.cpp

@@ -60,8 +60,7 @@
    setWindowTitle(tr("Example MainWindow"));
    resize(800, 600);

    setFixedHeight(600);

    // setFixedHeight(600);
    // windowAgent->centralize();
}