Add support for using arbitrary windows as wxStaticBox labels

This commit implements the new feature in wxGTK and updates the sample
and the documentation.

include/wx/gtk/statbox.h

@@ -18,6 +18,7 @@ class WXDLLIMPEXP_CORE wxStaticBox : public wxStaticBoxBase
 public:
     wxStaticBox()
     {
+        Init();
     }
 
     wxStaticBox( wxWindow *parent,
@@ -28,6 +29,21 @@ public:
                  long style = 0,
                  const wxString &name = wxStaticBoxNameStr )
     {
+        Init();
+
+        Create( parent, id, label, pos, size, style, name );
+    }
+
+    wxStaticBox( wxWindow *parent,
+                 wxWindowID id,
+                 wxWindow* label,
+                 const wxPoint &pos = wxDefaultPosition,
+                 const wxSize &size = wxDefaultSize,
+                 long style = 0,
+                 const wxString &name = wxStaticBoxNameStr )
+    {
+        Init();
+
         Create( parent, id, label, pos, size, style, name );
     }
 
@@ -37,7 +53,21 @@ public:
                  const wxPoint &pos = wxDefaultPosition,
                  const wxSize &size = wxDefaultSize,
                  long style = 0,
-                 const wxString &name = wxStaticBoxNameStr );
+                 const wxString &name = wxStaticBoxNameStr )
+    {
+        return DoCreate( parent, id, &label, NULL, pos, size, style, name );
+    }
+
+    bool Create( wxWindow *parent,
+                 wxWindowID id,
+                 wxWindow* label,
+                 const wxPoint &pos = wxDefaultPosition,
+                 const wxSize &size = wxDefaultSize,
+                 long style = 0,
+                 const wxString &name = wxStaticBoxNameStr )
+    {
+        return DoCreate( parent, id, NULL, label, pos, size, style, name );
+    }
 
     virtual void SetLabel( const wxString &label ) wxOVERRIDE;
 
@@ -52,13 +82,39 @@ public:
 
     virtual void AddChild( wxWindowBase *child ) wxOVERRIDE;
 
+    virtual void WXDestroyWithoutChildren() wxOVERRIDE;
+
 protected:
+    // Common part of all ctors.
+    void Init()
+    {
+        m_labelWin = NULL;
+    }
+
+    // Common implementation of both Create() overloads: exactly one of
+    // labelStr and labelWin parameters must be non-null.
+    bool DoCreate(wxWindow *parent,
+                  wxWindowID id,
+                  const wxString* labelStr,
+                  wxWindow* labelWin,
+                  const wxPoint& pos,
+                  const wxSize& size,
+                  long style,
+                  const wxString& name);
+
     virtual bool GTKWidgetNeedsMnemonic() const wxOVERRIDE;
     virtual void GTKWidgetDoSetMnemonic(GtkWidget* w) wxOVERRIDE;
 
     void DoApplyWidgetStyle(GtkRcStyle *style) wxOVERRIDE;
 
+    // If non-null, the window used as our label. This window is owned by the
+    // static box and will be deleted when it is.
+    wxWindow* m_labelWin;
+
     wxDECLARE_DYNAMIC_CLASS(wxStaticBox);
 };
 
+// Indicate that we have the ctor overload taking wxWindow as label.
+#define wxHAS_WINDOW_LABEL_IN_STATIC_BOX
+
 #endif // _WX_GTKSTATICBOX_H_