Fix to crash in QWindow::event when delete this called on closeEvent

Starting from Qt 5.11 QWindow::event is called after QDialog::closeEvent
which would cause a crash if "delete this" was called on closeEvent.  The commit
that changed this was e0b5ff4ad583befbecbcbe462998e3ed80899531. Added
a check before QWindow::event call utilizing QPointer to prevent the
function call in case object is destroyed by a user in close event handler.

Change-Id: I64a4a0f3271714e55bf7e806177f0d8b39b67fa3
Fixes: QTBUG-84222
Pick-to: 5.12.9
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 036c3c19e7da5f1a280750d3c68a0cff38678029)

1 files changed, 20 insertions, 0 deletions

diff --git a/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp b/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
index 788e005939..9d2ed2e14e 100644
--- a/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
+++ b/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
@@ -399,6 +399,8 @@ private slots:
     void closeEvent();
     void closeWithChildWindow();
 
+    void deleteWindowInCloseEvent();
+
 private:
     bool ensureScreenSize(int width, int height);
 
@@ -11144,5 +11146,23 @@ void tst_QWidget::closeWithChildWindow()
     QVERIFY(!childWidget->isVisible());
 }
 
+class DeleteOnCloseEventWidget : public QWidget
+{
+protected:
+    virtual void closeEvent(QCloseEvent *e) override
+    {
+        e->accept();
+        delete this;
+    }
+};
+
+void tst_QWidget::deleteWindowInCloseEvent()
+{
+    // Just checking if closing this widget causes a crash
+    auto widget = new DeleteOnCloseEventWidget;
+    widget->close();
+    QVERIFY(true);
+}
+
 QTEST_MAIN(tst_QWidget)
 #include "tst_qwidget.moc"