Resolves: rhbz#1146169 a11y frames label dies before frame

Change-Id: Ie5650c3a5593dcf68196802169c47270a0c3b0e6

include/vcl/layout.hxx

@@ -459,6 +459,7 @@ private:
 private:
     friend class VclBuilder;
     void designate_label(vcl::Window *pWindow);
+    DECL_LINK(WindowEventListener, VclSimpleEvent*);
 public:
     VclFrame(vcl::Window *pParent)
         : VclBin(pParent)

vcl/source/window/layout.cxx

@@ -1340,10 +1340,21 @@ void VclFrame::setAllocation(const Size &rAllocation)
         setLayoutAllocation(*pChild, aChildPos, aAllocation);
 }
 
+IMPL_LINK(VclFrame, WindowEventListener, VclSimpleEvent*, pEvent)
+{
+    if (pEvent && pEvent->GetId() == VCLEVENT_OBJECT_DYING)
+        designate_label(NULL);
+    return 0;
+}
+
 void VclFrame::designate_label(vcl::Window *pWindow)
 {
-    assert(pWindow->GetParent() == this);
+    assert(!pWindow || pWindow->GetParent() == this);
+    if (m_pLabel)
+        m_pLabel->RemoveEventListener(LINK(this, VclFrame, WindowEventListener));
     m_pLabel = pWindow;
+    if (m_pLabel)
+        m_pLabel->AddEventListener(LINK(this, VclFrame, WindowEventListener));
 }
 
 const vcl::Window *VclFrame::get_label_widget() const