As per the wx-dev discussion in early Jan, replaced

wxWindow::m_parentSizer with m_containingSizer which is used to track
which sizer this window is a member of.  Windows will now remove
themselves from a sizer when destroyed.  Also added accessors so
window classes can find out if they are in a sizer and do things like
reset their min size, etc.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@14221 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/wincmn.cpp

@@ -152,6 +152,7 @@ void wxWindowBase::InitBase()
     m_constraints = (wxLayoutConstraints *) NULL;
     m_constraintsInvolvedIn = (wxWindowList *) NULL;
     m_windowSizer = (wxSizer *) NULL;
+    m_containingSizer = (wxSizer *) NULL;
     m_autoLayout = FALSE;
 #endif // wxUSE_CONSTRAINTS
 
@@ -257,6 +258,9 @@ wxWindowBase::~wxWindowBase()
         m_constraints = NULL;
     }
 
+    if ( m_containingSizer )
+        m_containingSizer->Remove((wxWindow*)this);
+
     if ( m_windowSizer )
         delete m_windowSizer;