Qt 编写的qml程序全屏时，挡住系统虚拟键盘的解决办法

官方有提到该问题。尤其是使用qml时，一定会出现这个遮挡问题。
https://doc.qt.io/qt-5/windows-issues.html

 默认的qml工程的解决代码如下：

 1 ...
 2 #include <QWindow>
 3 #include <QtPlatformHeaders/QWindowsWindowFunctions>
 4 ...
 5 
 6 int main(int argc, char *argv[])
 7 {
 8 ...
 9     QQmlApplicationEngine engine;
10     const QUrl url(QStringLiteral("qrc:/qml/main.qml"));
11     QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
12                      &app, [url](QObject *obj, const QUrl &objUrl) {
13         if (!obj && url == objUrl)
14             QCoreApplication::exit(-1);
15     }, Qt::QueuedConnection);
16     engine.load(url);
17     
18     auto tlwWindow = (QWindow*)engine.rootObjects().first();
19     QWindowsWindowFunctions::setHasBorderInFullScreen(tlwWindow, true);
20 ...
21 }