Use virtual function to retrieve interface pointer

xfa/fwl/lightwidget/cfwl_widget.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef XFA_FWL_LIGHTWIDGET_CFWL_WIDGET_H_
 #define XFA_FWL_LIGHTWIDGET_CFWL_WIDGET_H_
 
+#include <memory>
+
 #include "xfa/fwl/core/cfwl_event.h"
 #include "xfa/fwl/lightwidget/cfwl_widgetproperties.h"
 #include "xfa/fwl/core/ifwl_widget.h"
 
 class CFWL_Event;
 class CFWL_Message;
 class CFWL_Widget;
 class CFWL_WidgetDelegate;
 class CFWL_WidgetMgr;
 
 class CFWL_Widget {
  public:
   virtual ~CFWL_Widget();
 
-  IFWL_Widget* GetWidget();
+  virtual IFWL_Widget* GetWidget();
+  virtual const IFWL_Widget* GetWidget() const;
+
   FWL_Error GetClassName(CFX_WideString& wsClass) const;
   FWL_Type GetClassID() const;
   virtual FX_BOOL IsInstance(const CFX_WideStringC& wsClass) const;
 
   FWL_Error GetWidgetRect(CFX_RectF& rect, FX_BOOL bAutoSize = FALSE);
   FWL_Error GetGlobalRect(CFX_RectF& rect);
   FWL_Error SetWidgetRect(const CFX_RectF& rect);
   FWL_Error GetClientRect(CFX_RectF& rtClient);
   CFWL_Widget* GetParent();
   FWL_Error SetParent(CFWL_Widget* pParent);
@@ skipping 28 matching lines @@
   FWL_Error SetFocus(FX_BOOL bFocus);
   FWL_Error SetGrab(FX_BOOL bSet);
   CFWL_Widget();
 
   void RegisterEventTarget(CFWL_Widget* pEventSource = nullptr,
                            uint32_t dwFilter = FWL_EVENT_ALL_MASK);
   void DispatchEvent(CFWL_Event* pEvent);
   CFX_SizeF CalcTextSize(const CFX_WideString& wsText,
                          FX_BOOL bMultiLine = FALSE,
                          int32_t iLineWidth = -1);
-  IFWL_Widget* m_pIface;
-  IFWL_WidgetDelegate* m_pDelegate;
-  CFWL_WidgetMgr* m_pWidgetMgr;
-  CFWL_WidgetProperties* m_pProperties;
 
  protected:
   FWL_Error Initialize(const CFWL_WidgetProperties* pProperties = nullptr);
+
+  std::unique_ptr<IFWL_Widget> m_pIface;
+  IFWL_WidgetDelegate* m_pDelegate;
+  CFWL_WidgetMgr* const m_pWidgetMgr;
+  std::unique_ptr<CFWL_WidgetProperties> m_pProperties;
 };
 
 #endif  // XFA_FWL_LIGHTWIDGET_CFWL_WIDGET_H_