Fix app showing a blank screen after switching to it using task switcher

On S60, the widget backing store is dropped when app window is hidden
in order to save memory. This has a side effect that the widgets are not
redrawn when the backing store is recreated if they have static content.

Fix is to invalidate the backing buffer after recreating it, and repaint
the widget.

Reviewed-by: Jason Barron

1 files changed, 10 insertions, 9 deletions

diff --git a/src/gui/kernel/qapplication_s60.cpp b/src/gui/kernel/qapplication_s60.cpp
index 27e8602..8daac42 100644
--- a/src/gui/kernel/qapplication_s60.cpp
+++ b/src/gui/kernel/qapplication_s60.cpp
@@ -480,7 +480,7 @@ void QSymbianControl::HandlePointerEvent(const TPointerEvent& pEvent)
             alienWidget = qwidget;
         S60->mousePressTarget = alienWidget;
     }
-    
+
     alienWidget = S60->mousePressTarget;
 
     if (alienWidget != S60->lastPointerEventTarget)
@@ -600,7 +600,7 @@ TKeyResponse QSymbianControl::OfferKeyEvent(const TKeyEvent& keyEvent, TEventCod
             if (keyCode >= Qt::Key_Left && keyCode <= Qt::Key_Down || keyCode == Qt::Key_Select) {
                 /*Explanation about virtualMouseAccel:
                  Tapping an arrow key allows precise pixel positioning
-                 Holding an arrow key down, acceleration is applied to allow cursor 
+                 Holding an arrow key down, acceleration is applied to allow cursor
                  to be quickly moved to another part of the screen by key repeats.
                  */
                 if (S60->virtualMouseLastKey == keyCode) {
@@ -668,7 +668,7 @@ TKeyResponse QSymbianControl::OfferKeyEvent(const TKeyEvent& keyEvent, TEventCod
             }
         }
 #endif
-        
+
         Qt::KeyboardModifiers mods = mapToQtModifiers(keyEvent.iModifiers);
         QKeyEventEx qKeyEvent(type == EEventKeyUp ? QEvent::KeyRelease : QEvent::KeyPress, keyCode,
                 mods, qt_keymapper_private()->translateKeyEvent(keyCode, mods),
@@ -993,13 +993,13 @@ void qt_init(QApplicationPrivate * /* priv */, int)
         S60->hasTouchscreen = true;
         S60->virtualMouseRequired = false;
     }
-    
+
     if (touch) {
         QApplicationPrivate::navigationMode = Qt::NavigationModeNone;
     } else {
         QApplicationPrivate::navigationMode = Qt::NavigationModeKeypadDirectional;
     }
-    
+
 #ifndef QT_NO_CURSOR
     //Check if window server pointer cursors are supported or not
 #ifndef Q_SYMBIAN_FIXED_POINTER_CURSORS
@@ -1063,7 +1063,7 @@ void qt_cleanup()
     // it dies.
     delete QApplicationPrivate::inputContext;
     QApplicationPrivate::inputContext = 0;
-    
+
     //Change mouse pointer back
     S60->wsSession().SetPointerCursorMode(EPointerCursorNone);
 
@@ -1383,7 +1383,8 @@ int QApplication::s60ProcessEvent(TWsEvent *event)
             } else if ((visChangedEvent->iFlags & TWsVisibilityChangedEvent::EPartiallyVisible)
                        && !w->d_func()->maybeBackingStore()) {
                 w->d_func()->topData()->backingStore = new QWidgetBackingStore(w);
-                w->update();
+                w->d_func()->invalidateBuffer(w->rect());
+                w->repaint();
             }
             return 1;
         }
@@ -1599,7 +1600,7 @@ void QApplicationPrivate::setNavigationMode(Qt::NavigationMode mode)
     const bool isCursorOn = (mode == Qt::NavigationModeCursorAuto
         && !S60->hasTouchscreen)
         || mode == Qt::NavigationModeCursorForceVisible;
-    
+
     if (!wasCursorOn && isCursorOn) {
         //Show the cursor, when changing from another mode to cursor mode
         qt_symbian_set_cursor_visible(true);
@@ -1629,7 +1630,7 @@ void QApplication::restoreOverrideCursor()
     if (qApp->d_func()->cursor_list.isEmpty())
         return;
     qApp->d_func()->cursor_list.removeFirst();
-    
+
     if (!qApp->d_func()->cursor_list.isEmpty()) {
         qt_symbian_setGlobalCursor(qApp->d_func()->cursor_list.first());
     }