diff -rupN 2/orig/qapplication.cpp 2/new/qapplication.cpp
--- 2/orig/qapplication.cpp	Thu Dec  8 07:06:02 2011
+++ 2/new/qapplication.cpp	Wed Jan 18 17:22:27 2012
@@ -974,6 +974,7 @@ void QApplicationPrivate::initialize()
 {
     QWidgetPrivate::mapper = new QWidgetMapper;
     QWidgetPrivate::allWidgets = new QWidgetSet;
+    QWidgetPrivate::topLevelWidgets = new QWidgetSet;
 
 #if !defined(Q_WS_X11) && !defined(Q_WS_QWS) && !defined(Q_WS_QPA)
     // initialize the graphics system - on X11 this is initialized inside
@@ -2138,15 +2139,10 @@ void QApplication::setWindowIcon(const Q
 */
 QWidgetList QApplication::topLevelWidgets()
 {
-    QWidgetList list;
-    QWidgetList all = allWidgets();
-
-    for (QWidgetList::ConstIterator it = all.constBegin(); it != all.constEnd(); ++it) {
-        QWidget *w = *it;
-        if (w->isWindow() && w->windowType() != Qt::Desktop)
-            list.append(w);
+    if (QWidgetPrivate::topLevelWidgets){
+        return QWidgetList(QWidgetPrivate::topLevelWidgets->toList());
     }
-    return list;
+    return QWidgetList();
 }
 
 /*!
diff -rupN 2/orig/qwidget.cpp 2/new/qwidget.cpp
--- 2/orig/qwidget.cpp	Thu Dec  8 07:06:02 2011
+++ 2/new/qwidget.cpp	Thu Jan 19 12:54:32 2012
@@ -1081,7 +1081,7 @@ void QWidget::setAutoFillBackground(bool
 
 QWidgetMapper *QWidgetPrivate::mapper = 0;          // widget with wid
 QWidgetSet *QWidgetPrivate::allWidgets = 0;         // widgets with no wid
-
+QWidgetSet *QWidgetPrivate::topLevelWidgets = 0;    
 
 /*****************************************************************************
   QWidget utility functions
@@ -1130,6 +1130,7 @@ struct QWidgetExceptionCleaner
         Q_UNUSED(d);
 #else
         QWidgetPrivate::allWidgets->remove(that);
+        QWidgetPrivate::topLevelWidgets->remove(that);
         if (d->focus_next != that) {
             if (d->focus_next)
                 d->focus_next->d_func()->focus_prev = d->focus_prev;
@@ -1388,6 +1389,9 @@ void QWidgetPrivate::init(QWidget *paren
         || QApplicationPrivate::testAttribute(Qt::AA_ImmediateWidgetCreation))
         q->create();
 
+    if (QWidgetPrivate::topLevelWidgets && q->isWindow() && q->windowType() != Qt::Desktop)    {
+        QWidgetPrivate::topLevelWidgets->insert(q);    
+    }
 
     QEvent e(QEvent::Create);
     QApplication::sendEvent(q, &e);
@@ -1689,6 +1693,8 @@ QWidget::~QWidget()
 
     if (QWidgetPrivate::allWidgets) // might have been deleted by ~QApplication
         QWidgetPrivate::allWidgets->remove(this);
+    if (QWidgetPrivate::topLevelWidgets) // might have been deleted by ~QApplication
+        QWidgetPrivate::topLevelWidgets->remove(this);
 
     QT_TRY {
         QEvent e(QEvent::Destroy);
@@ -10071,6 +10077,12 @@ void QWidget::setWindowFlags(Qt::WindowF
         d->adjustQuitOnCloseAttribute();
     } else {
         data->window_flags = flags;
+    }
+
+    if (QWidgetPrivate::topLevelWidgets && isWindow() && windowType() != Qt::Desktop) {
+        QWidgetPrivate::topLevelWidgets->insert(this);
+    }else {
+        QWidgetPrivate::topLevelWidgets->remove(this);
     }
 }
 
diff -rupN 2/orig/qwidget_p.h 2/new/qwidget_p.h
--- 2/orig/qwidget_p.h	Thu Dec  8 07:06:02 2011
+++ 2/new/qwidget_p.h	Wed Jan 18 17:21:40 2012
@@ -708,6 +708,7 @@ public:
     // This should just ensure that all widgets are deleted by QApplication
     static QWidgetMapper *mapper;
     static QWidgetSet *allWidgets;
+    static QWidgetSet *topLevelWidgets;
 #if !defined(QT_NO_IM)
     QPointer<QInputContext> ic;
     Qt::InputMethodHints imHints;