Enable dynamic [de|con]struction of window surfaces based on visibility

When a window becomes completely obscured either because it has been
hidden or another window is completely covering it, the backing store
should be deallocated to save memory and then re-allocated when the
window is later made visible again.

Reviewed-by: Iain <qt-info@nokia.com>

2 files changed, 29 insertions, 13 deletions

diff --git a/src/gui/kernel/qapplication_s60.cpp b/src/gui/kernel/qapplication_s60.cpp
index b021b1c..c7bbcdb 100644
--- a/src/gui/kernel/qapplication_s60.cpp
+++ b/src/gui/kernel/qapplication_s60.cpp
@@ -531,6 +531,9 @@ TCoeInputCapabilities QSymbianControl::InputCapabilities() const
 void QSymbianControl::Draw(const TRect& r) const
 {
     QWindowSurface *surface = qwidget->windowSurface();
+    if (!surface)
+        return;
+
     QPaintEngine *engine = surface->paintDevice()->paintEngine();
     if (!engine)
         return;
@@ -948,6 +951,7 @@ int QApplication::s60ProcessEvent(TWsEvent *event)
     // Qt event handling. Handle some events regardless of if the handle is in our
     // widget map or not.
     CCoeControl* control = reinterpret_cast<CCoeControl*>(event->Handle());
+    const bool controlInMap = QWidgetPrivate::mapper && QWidgetPrivate::mapper->contains(control);
     switch (event->Type()) {
 #ifndef QT_NO_IM
     case EEventKey:
@@ -970,17 +974,12 @@ int QApplication::s60ProcessEvent(TWsEvent *event)
     }
 #endif
     case EEventPointerEnter:
-        if (QWidgetPrivate::mapper && QWidgetPrivate::mapper->contains(control))
-        {
-            // Qt::Enter will be generated in HandlePointerL
-            return 1;
-        }
+        if (controlInMap)
+            return 1; // Qt::Enter will be generated in HandlePointerL
         break;
     case EEventPointerExit:
-        if (QWidgetPrivate::mapper && QWidgetPrivate::mapper->contains(control))
-        {
-            if (S60)
-            {
+        if (controlInMap) {
+            if (S60) {
                 // mouseEvent outside our window, send leave event to last focused widget
                 QMouseEvent mEvent(QEvent::Leave, S60->lastPointerEventPos, S60->lastCursorPos,
                     Qt::NoButton, QApplicationPrivate::mouse_buttons, Qt::NoModifier);
@@ -995,11 +994,27 @@ int QApplication::s60ProcessEvent(TWsEvent *event)
         if (S60)
             S60->updateScreenSize();
         return 0; // Propagate to CONE
+    case EEventWindowVisibilityChanged:
+        if (controlInMap) {
+            const TWsVisibilityChangedEvent *visChangedEvent = event->VisibilityChanged();
+            QWidget *w = QWidgetPrivate::mapper->value(control);
+            if (!w->d_func()->maybeTopData())
+                break;
+            if (visChangedEvent->iFlags & TWsVisibilityChangedEvent::ENotVisible) {
+                delete w->d_func()->topData()->backingStore;
+                w->d_func()->topData()->backingStore = 0;
+            } else if ((visChangedEvent->iFlags & TWsVisibilityChangedEvent::EPartiallyVisible)
+                       && !w->d_func()->maybeBackingStore()) {
+                w->d_func()->topData()->backingStore = new QWidgetBackingStore(w);
+            }
+            return 1;
+        }
+        break;
     default:
         break;
     }
 
-    if (!QWidgetPrivate::mapper || !QWidgetPrivate::mapper->contains(control))
+    if (!controlInMap)
         return -1;
 
     return 0;
diff --git a/src/gui/kernel/qwidget_s60.cpp b/src/gui/kernel/qwidget_s60.cpp
index 116dc35..ec80a18 100644
--- a/src/gui/kernel/qwidget_s60.cpp
+++ b/src/gui/kernel/qwidget_s60.cpp
@@ -195,12 +195,13 @@ void QWidgetPrivate::create_sys(WId window, bool initializeWindow, bool destroyO
             data.crect.moveTopLeft(QPoint(clientRect.iTl.iX, clientRect.iTl.iY));
         QSymbianControl *control= new QSymbianControl(q);
         control->ConstructL(true,desktop);
-        if (!desktop)
-        {
+        if (!desktop) {
             QTLWExtra *topExtra = topData();
             topExtra->rwindow = control->DrawableWindow();
             // Request mouse move events.
-            topExtra->rwindow->PointerFilter(EPointerFilterEnterExit | EPointerFilterMove | EPointerFilterDrag, 0);
+            topExtra->rwindow->PointerFilter(EPointerFilterEnterExit
+                | EPointerFilterMove | EPointerFilterDrag, 0);
+            topExtra->rwindow->EnableVisibilityChangeEvents();
         }
 
         id = (WId)control;