3 files changed, 58 insertions, 31 deletions

diff --git a/src/gui/kernel/qapplication_s60.cpp b/src/gui/kernel/qapplication_s60.cpp
index 559bb6a..df93bc5 100644
--- a/src/gui/kernel/qapplication_s60.cpp
+++ b/src/gui/kernel/qapplication_s60.cpp
@@ -1926,27 +1926,24 @@ int QApplicationPrivate::symbianProcessWsEvent(const QSymbianEvent *symbianEvent
             QWidget *const window = w->window();
             if (!window->d_func()->maybeTopData())
                 break;
-            QRefCountedWidgetBackingStore &backingStore = window->d_func()->maybeTopData()->backingStore;
+            QWidgetBackingStoreTracker &backingStore = window->d_func()->maybeTopData()->backingStore;
             if (visChangedEvent->iFlags & TWsVisibilityChangedEvent::ENotVisible) {
 #ifdef  SYMBIAN_GRAPHICS_WSERV_QT_EFFECTS
                 S60->wsSession().SendEffectCommand(ETfxCmdDeallocateLayer);
 #endif
-                // Decrement backing store reference count
-                backingStore.deref();
+                backingStore.unregisterWidget(w);
                 // In order to ensure that any resources used by the window surface
                 // are immediately freed, we flush the WSERV command buffer.
                 S60->wsSession().Flush();
             } else if (visChangedEvent->iFlags & TWsVisibilityChangedEvent::EPartiallyVisible) {
                 if (backingStore.data()) {
-                    // Increment backing store reference count
-                    backingStore.ref();
+                    backingStore.registerWidget(w);
                 } else {
 #ifdef SYMBIAN_GRAPHICS_WSERV_QT_EFFECTS
                     S60->wsSession().SendEffectCommand(ETfxCmdRestoreLayer);
 #endif
-                    // Create backing store with an initial reference count of 1
                     backingStore.create(window);
-                    backingStore.ref();
+                    backingStore.registerWidget(w);
                     w->d_func()->invalidateBuffer(w->rect());
                     w->repaint();
                 }
diff --git a/src/gui/kernel/qwidget.cpp b/src/gui/kernel/qwidget.cpp
index aaa29a1..dad4848 100644
--- a/src/gui/kernel/qwidget.cpp
+++ b/src/gui/kernel/qwidget.cpp
@@ -162,47 +162,76 @@ static inline bool hasBackingStoreSupport()
 extern bool qt_sendSpontaneousEvent(QObject*, QEvent*); // qapplication.cpp
 extern QDesktopWidget *qt_desktopWidget; // qapplication.cpp
 
+/*!
+    \internal
+    \class QWidgetBackingStoreTracker
+    \brief Class which allows tracking of which widgets are using a given backing store
 
-QRefCountedWidgetBackingStore::QRefCountedWidgetBackingStore()
+    QWidgetBackingStoreTracker is a thin wrapper around a QWidgetBackingStore pointer,
+    which maintains a list of the QWidgets which are currently using the backing
+    store.  This list is modified via the registerWidget and unregisterWidget functions.
+ */
+
+QWidgetBackingStoreTracker::QWidgetBackingStoreTracker()
     :   m_ptr(0)
-    ,   m_count(0)
 {
 
 }
 
-QRefCountedWidgetBackingStore::~QRefCountedWidgetBackingStore()
+QWidgetBackingStoreTracker::~QWidgetBackingStoreTracker()
 {
     delete m_ptr;
 }
 
-void QRefCountedWidgetBackingStore::create(QWidget *widget)
+/*!
+    \internal
+    Destroy the contained QWidgetBackingStore, if not null, and clear the list of
+    widgets using the backing store, then create a new QWidgetBackingStore, providing
+    the QWidget.
+ */
+void QWidgetBackingStoreTracker::create(QWidget *widget)
 {
     destroy();
     m_ptr = new QWidgetBackingStore(widget);
-    m_count = 0;
 }
 
-void QRefCountedWidgetBackingStore::destroy()
+/*!
+    \internal
+    Destroy the contained QWidgetBackingStore, if not null, and clear the list of
+    widgets using the backing store.
+ */
+void QWidgetBackingStoreTracker::destroy()
 {
     delete m_ptr;
     m_ptr = 0;
-    m_count = 0;
+    m_widgets.clear();
 }
 
-void QRefCountedWidgetBackingStore::ref()
+/*!
+    \internal
+    Add the widget to the list of widgets currently using the backing store.
+    If the widget was already in the list, this function is a no-op.
+ */
+void QWidgetBackingStoreTracker::registerWidget(QWidget *w)
 {
     Q_ASSERT(m_ptr);
-    ++m_count;
+    Q_ASSERT(w->internalWinId());
+    Q_ASSERT(qt_widget_private(w)->maybeBackingStore() == m_ptr);
+    m_widgets.insert(w);
 }
 
-void QRefCountedWidgetBackingStore::deref()
+/*!
+    \internal
+    Remove the widget from the list of widgets currently using the backing store.
+    If the widget was in the list, and removing it causes the list to be empty,
+    the backing store is deleted.
+    If the widget was not in the list, this function is a no-op.
+ */
+void QWidgetBackingStoreTracker::unregisterWidget(QWidget *w)
 {
-    if (m_count) {
-        Q_ASSERT(m_ptr);
-        if (0 == --m_count) {
-            delete m_ptr;
-            m_ptr = 0;
-        }
+    if (m_widgets.remove(w) && m_widgets.isEmpty()) {
+        delete m_ptr;
+        m_ptr = 0;
     }
 }
 
diff --git a/src/gui/kernel/qwidget_p.h b/src/gui/kernel/qwidget_p.h
index 587d7fb..4a79dc7 100644
--- a/src/gui/kernel/qwidget_p.h
+++ b/src/gui/kernel/qwidget_p.h
@@ -110,17 +110,18 @@ class QWidgetItemV2;
 
 class QStyle;
 
-class Q_AUTOTEST_EXPORT QRefCountedWidgetBackingStore
+class Q_AUTOTEST_EXPORT QWidgetBackingStoreTracker
 {
+
 public:
-    QRefCountedWidgetBackingStore();
-    ~QRefCountedWidgetBackingStore();
+    QWidgetBackingStoreTracker();
+    ~QWidgetBackingStoreTracker();
 
     void create(QWidget *tlw);
     void destroy();
 
-    void ref();
-    void deref();
+    void registerWidget(QWidget *w);
+    void unregisterWidget(QWidget *w);
 
     inline QWidgetBackingStore* data()
     {
@@ -143,11 +144,11 @@ public:
     }
 
 private:
-    Q_DISABLE_COPY(QRefCountedWidgetBackingStore)
+    Q_DISABLE_COPY(QWidgetBackingStoreTracker)
 
 private:
     QWidgetBackingStore* m_ptr;
-    int m_count;
+    QSet<QWidget *> m_widgets;
 };
 
 struct QTLWExtra {
@@ -156,7 +157,7 @@ struct QTLWExtra {
     // Regular pointers (keep them together to avoid gaps on 64 bits architectures).
     QIcon *icon; // widget icon
     QPixmap *iconPixmap;
-    QRefCountedWidgetBackingStore backingStore;
+    QWidgetBackingStoreTracker backingStore;
     QWindowSurface *windowSurface;
     QPainter *sharedPainter;