Various wxCollapsiblePane enhancements (re-patch 1577412):

1. wxUSE_COLLPANE added
2. XRC handler added
3. flicker fixes for the generic version
4. sizing fixes for GTK+ version
5. RTL fixes for the generic version (via wxBoxSizer)
6. better appearance under Mac for the generic version


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42759 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/collpaneg.h

@@ -48,10 +48,13 @@ public:
     void Init()
     {
         m_pButton = NULL;
-        m_pStatLine = NULL;
         m_pPane = NULL;
+        m_pStaticLine = NULL;
+        m_sz = NULL;
     }
 
+    ~wxGenericCollapsiblePane();
+
     bool Create(wxWindow *parent,
                 wxWindowID winid,
                 const wxString& label,
@@ -80,17 +83,16 @@ public:
 protected:
     // overridden methods
     virtual wxSize DoGetBestSize() const;
-
-    // internal helpers
-    void LayoutChildren();
+    bool Layout();
 
     wxString GetBtnLabel() const;
-
+    int GetBorder() const;
 
     // child controls
     wxButton *m_pButton;
-    wxStaticLine *m_pStatLine;
+    wxStaticLine *m_pStaticLine;
     wxWindow *m_pPane;
+    wxSizer *m_sz;
 
     // the button label without ">>" or "<<"
     wxString m_strLabel;