If a QWidget is ignored for auto-quit, ignore its corresponding QWindow.

Unit test by Friedemann Kleint <Friedemann.Kleint@digia.com>

Task-number: QTBUG-31569
Change-Id: I526d33d4f88a41f6ac349098476bc45af6c841b0
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/gui/kernel/qguiapplication.cpp

@@ -2478,11 +2478,19 @@ void QGuiApplicationPrivate::emitLastWindowClosed()
 }
 
 bool QGuiApplicationPrivate::shouldQuit()
+{
+    const QWindowList processedWindows;
+    return shouldQuitInternal(processedWindows);
+}
+
+bool QGuiApplicationPrivate::shouldQuitInternal(const QWindowList &processedWindows)
 {
     /* if there is no visible top-level window left, we allow the quit */
     QWindowList list = QGuiApplication::topLevelWindows();
     for (int i = 0; i < list.size(); ++i) {
         QWindow *w = list.at(i);
+        if (processedWindows.contains(w))
+            continue;
         if (w->isVisible() && !w->transientParent())
             return false;
     }

src/gui/kernel/qguiapplication_p.h

@@ -91,6 +91,8 @@ public:
 
     virtual bool shouldQuit();
 
+    bool shouldQuitInternal(const QWindowList &processedWindows);
+
     static Qt::KeyboardModifiers modifier_buttons;
     static Qt::MouseButtons mouse_buttons;
 

src/widgets/kernel/qapplication.cpp

@@ -2695,12 +2695,14 @@ bool QApplicationPrivate::shouldQuit()
         the ones without QuitOnClose), we emit the lastWindowClosed
         signal */
     QWidgetList list = QApplication::topLevelWidgets();
+    QWindowList processedWindows;
     for (int i = 0; i < list.size(); ++i) {
         QWidget *w = list.at(i);
+        processedWindows.push_back(w->windowHandle());
         if (w->isVisible() && !w->parentWidget() && w->testAttribute(Qt::WA_QuitOnClose))
             return false;
     }
-    return QGuiApplicationPrivate::shouldQuit();
+    return QGuiApplicationPrivate::shouldQuitInternal(processedWindows);
 }
 
 static inline void closeAllPopups()

tests/auto/widgets/kernel/qapplication/tst_qapplication.cpp

@@ -783,6 +783,31 @@ void tst_QApplication::quitOnLastWindowClosed()
 
         QVERIFY(timerSpy.count() > 15);      // Should be around 20 if closing did not caused the quit
     }
+    {   // QTBUG-31569: If the last widget with Qt::WA_QuitOnClose set is closed, other
+        // widgets that don't have the attribute set should be closed automatically.
+        int argc = 0;
+        QApplication app(argc, 0);
+        QVERIFY(app.quitOnLastWindowClosed());
+
+        QWidget w1;
+        w1.show();
+
+        QWidget w2;
+        w2.setAttribute(Qt::WA_QuitOnClose, false);
+        w2.show();
+
+        QVERIFY(QTest::qWaitForWindowExposed(&w2));
+
+        QTimer timer;
+        timer.setInterval(100);
+        timer.start();
+        QSignalSpy timerSpy(&timer, SIGNAL(timeout()));
+
+        QTimer::singleShot(100, &w1, SLOT(close()));
+        app.exec();
+
+        QVERIFY(timerSpy.count() < 10);
+    }
 }
 
 class PromptOnCloseWidget : public QWidget