qml: Implement QWidgetAdapter::close() and window()

Clicking the title bar's close button now works

src/private/quick/QWidgetAdapter_quick.cpp

@@ -23,7 +23,7 @@
 
 #include <QResizeEvent>
 #include <QMouseEvent>
-#include <QWindow>
+#include <QQuickWindow>
 #include <QQmlComponent>
 #include <QQuickItem>
 #include <QQmlEngine>
@@ -156,7 +156,21 @@ void QWidgetAdapter::showNormal()
     qWarning() << Q_FUNC_INFO << "Implement me";
 }
 
-QWindow *QWidgetAdapter::windowHandle() const { return nullptr; }
+QWindow *QWidgetAdapter::windowHandle() const
+{
+    return QQuickItem::window();
+}
+
+QWidgetAdapter *QWidgetAdapter::window() const
+{
+    // We return the top-most QWidgetAdapter
+
+    if (QWidgetAdapter *w = parentWidget()) {
+        return w->window();
+    }
+
+    return const_cast<QWidgetAdapter *>(this);
+}
 
 QWidgetAdapter *QWidgetAdapter::parentWidget() const
 {
@@ -171,6 +185,12 @@ QWidgetAdapter *QWidgetAdapter::parentWidget() const
     return nullptr;
 }
 
+void QWidgetAdapter::close()
+{
+    if (QWindow *w = windowHandle())
+        w->close();
+}
+
 void QWidgetAdapter::move(int x, int y)
 {
     qDebug() << Q_FUNC_INFO << x << y << this;