QWidgetWindow: Immediately forward close events to QWindow

This way the platform window is destroyed in a timely manner, preventing
redundant close events from the window system.

Task-number: QTBUG-43344
Change-Id: Ifdfca59ceacef54405f1c227c493dc514a1b27ea
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/widgets/kernel/qwidgetwindow.cpp

@@ -237,6 +237,7 @@ bool QWidgetWindow::event(QEvent *event)
     switch (event->type()) {
     case QEvent::Close:
         handleCloseEvent(static_cast<QCloseEvent *>(event));
+        QWindow::event(event);
         return true;
 
     case QEvent::Enter:

tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp

@@ -401,6 +401,8 @@ private slots:
 
     void tabletTracking();
 
+    void closeEvent();
+
 private:
     bool ensureScreenSize(int width, int height);
 
@@ -10798,5 +10800,31 @@ void tst_QWidget::tabletTracking()
     QTRY_COMPARE(widget.moveEventCount, 3);
 }
 
+class CloseCountingWidget : public QWidget
+{
+public:
+    int closeCount = 0;
+    void closeEvent(QCloseEvent *ev) override;
+};
+
+void CloseCountingWidget::closeEvent(QCloseEvent *ev)
+{
+    ++closeCount;
+    ev->accept();
+}
+
+void tst_QWidget::closeEvent()
+{
+    CloseCountingWidget widget;
+    widget.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&widget));
+    // Yes we call the close() function twice. This mimics the behavior of QTBUG-43344 where
+    // QApplication first closes all windows and then QCocoaApplication flushes window system
+    // events, triggering more close events.
+    widget.windowHandle()->close();
+    widget.windowHandle()->close();
+    QCOMPARE(widget.closeCount, 1);
+}
+
 QTEST_MAIN(tst_QWidget)
 #include "tst_qwidget.moc"