MFC如何实现具有预览功能的字体对话框

MFC CFontDialog类封装了字体公共对话框，用于选择字体。
我们可以从CFontDialog派生一个对话框CMyFontDialog，用于预览选择的字体的显示效果。
下面是对应两文件代码，可以复制后生成两个文件。
具体使用时只要创建CFontDialog实例，将CFontDialog更改为CMyFontDialog便可。

// FontDialog.h
// (c) 1997 Roger Onslow

#ifndef _CMyFontDialog_
#define _CMyFontDialog_

class CMyFontDialog : public CFontDialog {
     DECLARE_DYNCREATE(CMyFontDialog);
public:
     CMyFontDialog(LPLOGFONT lplogfont=NULL, LPCTSTR sampletext="Sample Text", CWnd* pParentWnd=NULL);
protected:
     LPCTSTR m_sampletext;
public:
     CString SampleText() const { return m_sampletext; }
     void SetSampleText(LPCTSTR sampletext) { m_sampletext = sampletext; }
public:
     COLORREF TextColor() const { return m_cf.rgbColors; }
     void SetTextColor(COLORREF rgbColors) { m_cf.rgbColors = rgbColors; }
protected:
     // Dialog Data
protected:
     //{{AFX_DATA(CMyFontDialog)
     //}}AFX_DATA
     // Overrides
protected:
     // ClassWizard generate virtual function overrides
     //{{AFX_VIRTUAL(CMyFontDialog)
     virtual BOOL OnInitDialog();
     //}}AFX_VIRTUAL
     // Implementation
protected:
     // Generated message map functions
     //{{AFX_MSG(CMyFontDialog)
     //}}AFX_MSG
     DECLARE_MESSAGE_MAP()
};

#endif




////////////////////////////////////////////////////////////////////
// FontDialog.cpp
// (c) 1997 Roger Onslow

#include "stdafx.h"
#include "FontDialog.h"

#ifdef _DEBUG
#undef THIS_FILE
static char BASED_CODE THIS_FILE[] = __FILE__;
#endif

IMPLEMENT_DYNCREATE(CMyFontDialog, CFontDialog)

BEGIN_MESSAGE_MAP(CMyFontDialog, CFontDialog)
//{{AFX_MSG_MAP(CMyFontDialog)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

CMyFontDialog::CMyFontDialog(LPLOGFONT lpLogfont, LPCTSTR sampletext, CWnd* pParentWnd)
: CFontDialog(lpLogfont,CF_EFFECTS | CF_SCREENFONTS, NULL, pParentWnd)
, m_sampletext(sampletext)
{
}

BOOL CMyFontDialog::OnInitDialog() {
     BOOL r = CFontDialog::OnInitDialog();
     if (m_sampletext) {
          SetDlgItemText(stc5, m_sampletext);
     }
     return r;
}