Implement mainwindow example

Sine Striker

2023-12-05 f8975a7d449bac21a2fdbc1a8ca85d1f5b99b362

 src/widgets/widgetwindowagent.cpp

@@ -53,12 +53,12 @@
        Q_EMIT titleBarWidgetChanged(w);
    }

    QWidget *WidgetWindowAgent::systemButton(CoreWindowAgent::SystemButton button) const {
    QWidget *WidgetWindowAgent::systemButton(SystemButton button) const {
        Q_D(const WidgetWindowAgent);
        return static_cast<QWidget *>(d->context->systemButton(button));
    }

    void WidgetWindowAgent::setSystemButton(CoreWindowAgent::SystemButton button, QWidget *w) {
    void WidgetWindowAgent::setSystemButton(SystemButton button, QWidget *w) {
        Q_D(WidgetWindowAgent);
        if (!d->context->setSystemButton(button, w)) {
            return;