Fixed defect in handling of expose events for Symbian

Commit bc82db did not correctly handle native child widgets.

Consider the case when we have a top-level widget A with a native
child widget B.  When QSymbianControl::Draw() is called on the
control corresponding to B, the following occurs:
    1. The inExpose flag is set in B's QWExtra structure.
    2. The call to syncBackingStore() results in a call to
       QWidgetBackingStore::flush(), passing default parameters.
    3. Because no target widget was passed to flush(), this
       function selects the top-level widget (A) as the target for
       the flush operation, passing A as the first argument of
       QS60WindowSurface::flush().
    4. QS60WindowSurface::flush() checks the inExpose flag from A's
       QWExtra structure, finds it to be false, and proceeds to
       call DrawNow() on A's control.

Because QSymbianControl::Draw() uses the default graphics context,
this context is shared between controls.  This means that the DrawNow()
call in step 4 causes a WSERV-10 panic (Activate() called on an
already-active) graphics context.

This patch moves the inExpose flag from B's QWExtra into A's QTLWExtra,
with the result that the call to DrawNow() in step 4 is suppressed.

Task-number: QTBUG-7960
Reviewed-by: axis

3 files changed, 10 insertions, 6 deletions

diff --git a/src/gui/kernel/qapplication_s60.cpp b/src/gui/kernel/qapplication_s60.cpp
index 4a137ee..bf3ad71 100644
--- a/src/gui/kernel/qapplication_s60.cpp
+++ b/src/gui/kernel/qapplication_s60.cpp
@@ -809,12 +809,15 @@ TCoeInputCapabilities QSymbianControl::InputCapabilities() const
 void QSymbianControl::Draw(const TRect& controlRect) const
 {
     // Set flag to avoid calling DrawNow in window surface
-    QWExtra *extra = qwidget->d_func()->extraData();
-    if (extra && !extra->inExpose) {
-        extra->inExpose = true;
+    QWidget *window = qwidget->window();
+    Q_ASSERT(window);
+    QTLWExtra *topExtra = window->d_func()->maybeTopData();
+    Q_ASSERT(topExtra);
+    if (!topExtra->inExpose) {
+        topExtra->inExpose = true;
         QRect exposeRect = qt_TRect2QRect(controlRect);
         qwidget->d_func()->syncBackingStore(exposeRect);
-        extra->inExpose = false;
+        topExtra->inExpose = false;
     }
 
     QWindowSurface *surface = qwidget->windowSurface();
diff --git a/src/gui/kernel/qwidget_p.h b/src/gui/kernel/qwidget_p.h
index b1eb3c3..4b62074 100644
--- a/src/gui/kernel/qwidget_p.h
+++ b/src/gui/kernel/qwidget_p.h
@@ -173,6 +173,8 @@ struct QTLWExtra {
 #ifndef QT_NO_QWS_MANAGER
     QWSManager *qwsManager;
 #endif
+#elif defined(Q_OS_SYMBIAN)
+    uint inExpose : 1; // Prevents drawing recursion
 #endif
 };
 
@@ -229,7 +231,6 @@ struct QWExtra {
 #endif
 #elif defined(Q_OS_SYMBIAN) // <----------------------------------------------------- Symbian
     uint activated : 1; // RWindowBase::Activated has been called
-    uint inExpose : 1; // Prevents drawing recursion
 
     /**
      * Defines the behaviour of QSymbianControl::Draw.
diff --git a/src/gui/kernel/qwidget_s60.cpp b/src/gui/kernel/qwidget_s60.cpp
index a844430..ebd289c 100644
--- a/src/gui/kernel/qwidget_s60.cpp
+++ b/src/gui/kernel/qwidget_s60.cpp
@@ -878,6 +878,7 @@ void QWidgetPrivate::registerDropSite(bool /* on */)
 void QWidgetPrivate::createTLSysExtra()
 {
     extra->topextra->backingStore = 0;
+    extra->topextra->inExpose = 0;
 }
 
 void QWidgetPrivate::deleteTLSysExtra()
@@ -891,7 +892,6 @@ void QWidgetPrivate::createSysExtra()
     extra->activated = 0;
     extra->nativePaintMode = QWExtra::Default;
     extra->receiveNativePaintEvents = 0;
-    extra->inExpose = 0;
 }
 
 void QWidgetPrivate::deleteSysExtra()