自绘按钮的实现

//========================================================================
//TITLE:
//    自绘按钮的实现
//AUTHOR:
//    norains
//DATE:
//    Saturday  12-January-2008
//Environment:
//    VS2005 + SDK-WINCE5.0-MIPSII  
//    EVC + SDK-WINCE5.0-MIPSII 
//========================================================================

    自绘按钮的实现并不难,只不过如果是在非MFC类库中实现,却是显得有点麻烦,或是说,更需要一点小技巧.
   
    文章打算在CMainWnd窗口类中实现一个自绘按钮,为了方便讲解以及突出重点,CMainWnd直接派生于CWndBase类.关于CWndBase类的信息,可以在此找到:http://blog.csdn.net/norains/archive/2008/01/12/2040109.aspx
   
    首先我们先要创建一个按钮,我将它命名为m_hBnExit:
 

    m_hBnExit  =  CreateWindowEx(WS_EX_TOPMOST,
                                TEXT( " BUTTON " ),
                                TEXT( "" ),
                                BS_PUSHBUTTON  |    WS_VISIBLE  |  WS_CHILD  |  BS_OWNERDRAW ,
                                POS_EXIT.left,
                                POS_EXIT.top,
                                POS_EXIT.right  -  POS_EXIT.left,
                                POS_EXIT.bottom  -  POS_EXIT.top,
                                m_hWnd,
                                (HMENU)IDC_BTN_EXIT,
                                m_hInst,
                                NULL);

  这里有点需要注意,因为我们需要重新绘制按钮,所以BS_OWNERDRAW风格一定需要设置.一旦设置该风格,CMainWnd窗口的消息处理函数就能接收到按钮的WM_DRAWITEM消息:

        LRESULT CMainWnd::WndProc(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
        {
          ...
          
             switch (wMsg)
            {
                 case  WM_DRAWITEM:
                 if (((LPDRAWITEMSTRUCT)lParam) -> CtlID  ==  IDC_BTN_EXIT)
                {
                     // TODO something;
                }
                
                ...
                
            }
        
            ...
        }

  接下来需要做的就很简单了,我们只需要在接收到WM_DRAWITEM消息时,判断是否为退出按键的ID号(在本文例子中为IDC_BTN_EXIT),如果是的话就重新绘制.为此,我们定义一个OnDrawItemBtnExit()函数,用来绘制该按钮:

         void  CMainWnd::OnDrawItemBtnExit(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
        {
            LPDRAWITEMSTRUCT lpdis  =  (LPDRAWITEMSTRUCT) lParam;    
        
           // 读取按钮的图片
            HANDLE hBmp  =  LoadImage(m_hInst,MAKEINTRESOURCE(IDB_EXIT),IMAGE_BITMAP, 0 , 0 , 0 );
             if (hBmp  ==  NULL)
            {
                 return  ;
            }    
        
             // Draw the button
            HDC hdcBmp  =  CreateCompatibleDC(lpdis -> hDC);
            HGDIOBJ hOldSel  =  SelectObject(hdcBmp,hBmp);
        
             if ((lpdis -> itemState  &  ODS_SELECTED )  &&   ! (lpdis -> itemState  &  ODS_DISABLED))
            {
              // 按下状态
                TransparentBlt(lpdis -> hDC,
                                lpdis -> rcItem.left,
                                lpdis -> rcItem.top,
                                lpdis -> rcItem.right  -  lpdis -> rcItem.left,
                                lpdis -> rcItem.bottom  -  lpdis -> rcItem.top,
                                hdcBmp,
                                IMG_EXIT_PUSH.left,
                                IMG_EXIT_PUSH.top,
                                IMG_EXIT_PUSH.right  -  IMG_EXIT_PUSH.left,
                                IMG_EXIT_PUSH.bottom  -  IMG_EXIT_PUSH.top,
                                DEFAULT_TRANSPARENT_COLOR);
            }
             else   if (lpdis -> itemState  &  ODS_DISABLED)
            {
              // 无效状态
                TransparentBlt(lpdis -> hDC,
                                    lpdis -> rcItem.left,
                                    lpdis -> rcItem.top,
                                    lpdis -> rcItem.right  -  lpdis -> rcItem.left,
                                    lpdis -> rcItem.bottom  -  lpdis -> rcItem.top,
                                    hdcBmp,
                                    IMG_EXIT_DISABLE.left,
                                    IMG_EXIT_DISABLE.top,
                                    IMG_EXIT_DISABLE.right  -  IMG_EXIT_DISABLE.left,
                                    IMG_EXIT_DISABLE.bottom  -  IMG_EXIT_DISABLE.top,
                                    DEFAULT_TRANSPARENT_COLOR);
            }
             else
            {
               // 正常状态
                TransparentBlt(lpdis -> hDC,
                                lpdis -> rcItem.left,
                                lpdis -> rcItem.top,
                                lpdis -> rcItem.right  -  lpdis -> rcItem.left,
                                lpdis -> rcItem.bottom  -  lpdis -> rcItem.top,
                                hdcBmp,
                                IMG_EXIT_ENABLE.left,
                                IMG_EXIT_ENABLE.top,
                                IMG_EXIT_ENABLE.right  -  IMG_EXIT_ENABLE.left,
                                IMG_EXIT_ENABLE.bottom  -  IMG_EXIT_ENABLE.top,
                                DEFAULT_TRANSPARENT_COLOR);
            }
        
             if (hdcBmp  !=  NULL  &&  hOldSel  !=  NULL)
            {
                SelectObject(hdcBmp,hOldSel);    
                DeleteDC(hdcBmp);
        
                hdcBmp  =  NULL;
                hOldSel  =  NULL;
            }
        
             if (hBmp  !=  NULL)
            {
                DeleteObject(hBmp);
                hBmp  =  NULL;
            }    
        
        }

    不过这么一来会有个很明显的问题,如图1:
        

    我们发现在按钮周围有一圈非常不雅的灰色地带,而这灰色区域是窗口创建的时候自绘的.有经验的朋友都知道,如果是自己创建的窗口,要让这灰色区域消失是非常简单的事情,只需要在调用RegisterClass函数时选择一个无颜色的画刷即可.但由于所有的Windows Control的注册函数都是封装的,我们无法对其参数进行变更,所以唯一的方法只能是另寻窍门.
   
    所谓的去掉灰色地带,无非就是把主窗口那处被掩盖的区域重新绘制出来.有这个思路一切就好办了,我们只需要在主窗口的WM_PAINT响应函数中存储主窗口的DC数据,然后在按钮重绘的时候再把它显示出来即可:

         void  CMainWnd::OnPaint(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
        {
            ...
            
             // 存储主窗口的所有DC数据到m_hdcBufBk中
                 // Create the memory DC for storing the background.
                m_hBmpBufBk  =  CreateCompatibleBitmap(hdc,rcWnd.right  -  rcWnd.left,rcWnd.bottom  -  rcWnd.top);
                m_hdcBufBk  =  CreateCompatibleDC(hdc);        
                m_hOldSelBufBk  =  SelectObject(m_hdcBufBk,m_hBmpBufBk);
        
        
                 // Draw the background
                HPEN hPen = CreatePen(PS_SOLID, 1 ,RGB( 0 , 255 , 0 ));
                HPEN hOldPen = NULL;
                hOldPen = (HPEN)SelectObject(m_hdcBufBk,hPen);
                 // the rect color
                HBRUSH hBrush  =  CreateSolidBrush(RGB( 0 , 255 , 0 ));
                HGDIOBJ hOldBrush  =  SelectObject(m_hdcBufBk,hBrush);
                 // Draw
                Rectangle(m_hdcBufBk, 0 , 0 ,rcWnd.right  -  rcWnd.left  +   1 , rcWnd.bottom  -  rcWnd.top  +   1 );
                 // Realse the resource
                SelectObject(m_hdcBufBk,hOldBrush);
                DeleteObject(hBrush);
                SelectObject(m_hdcBufBk,hOldPen);
                DeleteObject(hPen);
                
                ...    
        
        }

    然后在按钮的自绘函数中将其绘制出来:

     void  CMainWnd::OnDrawItemBtnExit(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
        {
            ...
            
                 // Draw the background
                BitBlt(lpdis -> hDC,
                        lpdis -> rcItem.left,
                        lpdis -> rcItem.top,
                        lpdis -> rcItem.right  -  lpdis -> rcItem.left,
                        lpdis -> rcItem.bottom  -  lpdis -> rcItem.top,
                        m_hdcBufBk,
                        POS_EXIT.left,
                        POS_EXIT.top,
                        SRCCOPY);
                    
                    ...
        }

  添加背景绘制代码之后显示的效果如图2所示:
  
  
  如果你的目的仅仅是用图片替代原来那种死板的按钮样式的话,那么到这步已经是大功告成,可以举杯欢庆了.但如果你还需要更多的需求,比如显示出通过SetWindowText设置的字符串,那么你还必须要做更多的工作.
  
  因为我们无法直接通过GetWindowText获取设置文本的真正长度,所以我们必须在按钮接收WM_SETTEXT消息时获取窗口文本.也许有人说,我设置一个很大的缓冲区不就行了么?可是,你需要设置多大?最好不要抱这种想法,因为我们永远不知道用户的真正意思!
  
  除了文档中明白指出的按钮消息,其它的消息我们都无法在MainProc函数中截获,比如按钮的WM_PAINT,WM_ERASEBKGND等.所以,这里我们需要在创建按钮控件的时候用SetWindowLong函数来转移按钮消息(关于SetWindowLong与消息转移可以参加我这篇文章:http://blog.csdn.net/norains/archive/2008/01/03/2023986.aspx).

         // Store the pointer in the window
        SetWindowLong(m_hBnExit, GWL_USERDATA, (DWORD) this );
         // Set the new window procedure
        m_PreProcBnExit  =  (WNDPROC)SetWindowLong(m_hBnExit,GWL_WNDPROC,(DWORD)CtrlProc);

    我们需要在转移的消息处理函数中截获WM_SETTEXT消息,并分配合适的内存空间存储设置的字符串:

        LRESULT CMainWnd::CtrlProc(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
        {
            CMainWnd  * pObject  =  (CMainWnd  * )GetWindowLong(hWnd,GWL_USERDATA);
             if (pObject  !=  NULL)
            {
                 if (hWnd  ==  pObject -> m_hBnExit)
                {
                     switch (wMsg)
                    {
                         case  WM_SETTEXT:
                        {
                             if (pObject -> m_pszBnExit  !=  NULL)
                            {
                                delete []pObject -> m_pszBnExit;
                                pObject -> m_pszBnExit  =  NULL;
                            }
                            pObject -> m_pszBnExit  =   new  TCHAR [_tcslen( reinterpret_cast < LPCTSTR > (lParam))  +   1 ];
                            _tcscpy(pObject -> m_pszBnExit,reinterpret_cast < LPCTSTR > (lParam));
                             break ;
                        }
                    }
                     return  CallWindowProc(pObject -> m_PreProcBnExit,hWnd,wMsg,wParam,lParam);
                }
            }
            
             return  DefWindowProc(hWnd,wMsg,wParam,lParam);
            
        }

  既然我们已经获得了字符串,要绘制出来就是轻而易举的事情了:

         void  CMainWnd::OnDrawItemBtnExit(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
        {
            ...
            
             // Draw the text
           SetBkMode(lpdis -> hDC,TRANSPARENT);
           DrawText(lpdis -> hDC,m_pszBnExit, - 1 , & lpdis -> rcItem,DT_CENTER  |  DT_VCENTER);
            
            ...
        }

  该工程可以在此下载:http://download.csdn.net/source/333479
  
  CMainWnd完整的代码如下:

#pragma  once

#include  " Wndbase.h "

class  CMainWnd :
     public  CWndBase
{
public :

     virtual  BOOL Create(HINSTANCE hInst, HWND hWndParent,  const  TCHAR  * pcszWndClass,  const  TCHAR  * pcszWndName);
    CMainWnd( void );
     ~ CMainWnd( void );

protected :
     virtual  LRESULT WndProc(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam);
     static  LRESULT CtrlProc(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam);
     void  OnClickedBtnExit(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam);
     void  OnDrawItemBtnExit(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam);
     void  OnPaint(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam);
    
    

private :
    HDC m_hdcBufBk;  // The dc buffer is just for storing the background data.
    HBITMAP m_hBmpBufBk;
    HGDIOBJ m_hOldSelBufBk;
    HWND m_hBnExit;
    TCHAR  * m_pszBnExit;
    WNDPROC m_PreProcBnExit;
};

#include  " stdafx.h "
#include  " resource.h "
#include  " MainWnd.h "


// *****************************************************************************************************
// The default transparent color for the image
#define  DEFAULT_TRANSPARENT_COLOR    RGB(255,0,255)


// *****************************************************************************************************
// The struct data

// The image displayed information
#ifndef _DISPIMAGEINFO
#define  _DISPIMAGEINFO
    typedef  struct
    {
        LONG imgID;
        LONG left;
        LONG top;
        LONG right;
        LONG bottom;
    }DISPIMAGEINFO, * PDISPIMAGEINFO;
#endif   // _DISPIMAGEINFO


// ------------------------------------------------------------------------------
// The resource information

const  DISPIMAGEINFO IMG_EXIT_ENABLE  =  {IDB_EXIT,  1 , 1 , 46 , 46 };
const  DISPIMAGEINFO IMG_EXIT_DISABLE  =  {IDB_EXIT,  93 , 1 , 138 , 46 };
const  DISPIMAGEINFO IMG_EXIT_PUSH  =  {IDB_EXIT,  47 , 1 , 92 , 46 };

// *****************************************************************************************************

// -------------------------------------------------------------------
// Macro 
#define  IDC_BTN_EXIT        103
// -------------------------------------------------------------------
// const value
const  RECT POS_EXIT  =  { 0 , 0 , 45 , 45 };
// -------------------------------------------------------------------

CMainWnd::CMainWnd( void ):
m_hBnExit(NULL),
m_hdcBufBk(NULL),
m_hBmpBufBk(NULL),
m_hOldSelBufBk(NULL),
m_PreProcBnExit(NULL),
m_pszBnExit(NULL)
{
}

CMainWnd:: ~ CMainWnd( void )
{
     if (m_hdcBufBk  !=  NULL  &&  m_hOldSelBufBk  !=  NULL)
    {
        SelectObject(m_hdcBufBk,m_hOldSelBufBk);
    }

     if (m_hBmpBufBk  !=  NULL)
    {    
        DeleteObject(m_hBmpBufBk);    
        
        m_hBmpBufBk  =  NULL;
    }

     if (m_hdcBufBk  !=  NULL)
    {        
        DeleteDC(m_hdcBufBk);
        
        m_hdcBufBk  =  NULL;
    }

     if (m_pszBnExit  !=  NULL)
    {
        delete []m_pszBnExit;

        m_pszBnExit  =  NULL;
    }

}


// ----------------------------------------------------------------------
// Description:
//     Create the window. It's override function
//
// ----------------------------------------------------------------------
BOOL CMainWnd::Create(HINSTANCE hInst, HWND hWndParent,  const  TCHAR  * pcszWndClass,  const  TCHAR  * pcszWndName)
{

    CWndBase::Create(hInst,hWndParent,pcszWndClass,pcszWndName);


     // The button for exiting
    m_hBnExit  =  CreateWindowEx(WS_EX_TOPMOST,
                                TEXT( " BUTTON " ),
                                TEXT( "" ),
                                BS_PUSHBUTTON  |  BS_CENTER  |  WS_TABSTOP  |  WS_VISIBLE  |  WS_CHILD  |  BS_OWNERDRAW ,
                                POS_EXIT.left,
                                POS_EXIT.top,
                                POS_EXIT.right  -  POS_EXIT.left,
                                POS_EXIT.bottom  -  POS_EXIT.top,
                                m_hWnd,
                                (HMENU)IDC_BTN_EXIT,
                                m_hInst,
                                NULL);


     // Store the pointer in the window
    SetWindowLong(m_hBnExit, GWL_USERDATA, (DWORD) this );
     // Set the new window procedure
    m_PreProcBnExit  =  (WNDPROC)SetWindowLong(m_hBnExit,GWL_WNDPROC,(DWORD)CtrlProc);
    
    
    SetWindowText(m_hBnExit,TEXT( " X " ));

     return  TRUE;
}

// ----------------------------------------------------------------------
// Description:
//     Window process. It's override function
//
// ----------------------------------------------------------------------
LRESULT CMainWnd::WndProc(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
{
     switch (wMsg)
    {
         case  WM_DRAWITEM:
         if (((LPDRAWITEMSTRUCT)lParam) -> CtlID  ==  IDC_BTN_EXIT)
        {
            OnDrawItemBtnExit(hWnd,wMsg,wParam,lParam);
             return   0 ;
        }
         case  WM_COMMAND:
        {
             if (HIWORD(wParam)  ==   BN_CLICKED   &&  LOWORD(wParam)  ==  IDC_BTN_EXIT)
            {
                OnClickedBtnExit(hWnd,wMsg,wParam,lParam);
            }
        }
         case  WM_PAINT:
        {
            OnPaint(hWnd,wMsg,wParam,lParam);
             return   0 ;
        }
    }

     return  DefWindowProc(hWnd,wMsg,wParam,lParam);
}

// ----------------------------------------------------------------------
// Description:
//     Windows control process
//
// ----------------------------------------------------------------------
LRESULT CMainWnd::CtrlProc(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
{
    CMainWnd  * pObject  =  (CMainWnd  * )GetWindowLong(hWnd,GWL_USERDATA);
     if (pObject  !=  NULL)
    {
         if (hWnd  ==  pObject -> m_hBnExit)
        {
             switch (wMsg)
            {
                 case  WM_SETTEXT:
                {
                     if (pObject -> m_pszBnExit  !=  NULL)
                    {
                        delete []pObject -> m_pszBnExit;
                        pObject -> m_pszBnExit  =  NULL;
                    }
                    pObject -> m_pszBnExit  =   new  TCHAR [_tcslen( reinterpret_cast < LPCTSTR > (lParam))  +   1 ];
                    _tcscpy(pObject -> m_pszBnExit,reinterpret_cast < LPCTSTR > (lParam));
                     break ;
                }
            }
             return  CallWindowProc(pObject -> m_PreProcBnExit,hWnd,wMsg,wParam,lParam);
        }
    }
    
     return  DefWindowProc(hWnd,wMsg,wParam,lParam);
    
}
// -----------------------------------------------------------------------------------------
// Description:
//     On the message WM_DRAWITEM and it is for the button exit
//
// ----------------------------------------------------------------------------------------------
void  CMainWnd::OnDrawItemBtnExit(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
{
    LPDRAWITEMSTRUCT lpdis  =  (LPDRAWITEMSTRUCT) lParam;    

    HANDLE hBmp  =  LoadImage(m_hInst,MAKEINTRESOURCE(IDB_EXIT),IMAGE_BITMAP, 0 , 0 , 0 );
     if (hBmp  ==  NULL)
    {
         return  ;
    }
    

     // Draw the background
    BitBlt(lpdis -> hDC,
            lpdis -> rcItem.left,
            lpdis -> rcItem.top,
            lpdis -> rcItem.right  -  lpdis -> rcItem.left,
            lpdis -> rcItem.bottom  -  lpdis -> rcItem.top,
            m_hdcBufBk,
            POS_EXIT.left,
            POS_EXIT.top,
            SRCCOPY);


     // Draw the button
    HDC hdcBmp  =  CreateCompatibleDC(lpdis -> hDC);
    HGDIOBJ hOldSel  =  SelectObject(hdcBmp,hBmp);

     if ((lpdis -> itemState  &  ODS_SELECTED )  &&   ! (lpdis -> itemState  &  ODS_DISABLED))
    {
        TransparentBlt(lpdis -> hDC,
                        lpdis -> rcItem.left,
                        lpdis -> rcItem.top,
                        lpdis -> rcItem.right  -  lpdis -> rcItem.left,
                        lpdis -> rcItem.bottom  -  lpdis -> rcItem.top,
                        hdcBmp,
                        IMG_EXIT_PUSH.left,
                        IMG_EXIT_PUSH.top,
                        IMG_EXIT_PUSH.right  -  IMG_EXIT_PUSH.left,
                        IMG_EXIT_PUSH.bottom  -  IMG_EXIT_PUSH.top,
                        DEFAULT_TRANSPARENT_COLOR);
    }
     else   if (lpdis -> itemState  &  ODS_DISABLED)
    {
        TransparentBlt(lpdis -> hDC,
                            lpdis -> rcItem.left,
                            lpdis -> rcItem.top,
                            lpdis -> rcItem.right  -  lpdis -> rcItem.left,
                            lpdis -> rcItem.bottom  -  lpdis -> rcItem.top,
                            hdcBmp,
                            IMG_EXIT_DISABLE.left,
                            IMG_EXIT_DISABLE.top,
                            IMG_EXIT_DISABLE.right  -  IMG_EXIT_DISABLE.left,
                            IMG_EXIT_DISABLE.bottom  -  IMG_EXIT_DISABLE.top,
                            DEFAULT_TRANSPARENT_COLOR);
    }
     else
    {
        TransparentBlt(lpdis -> hDC,
                        lpdis -> rcItem.left,
                        lpdis -> rcItem.top,
                        lpdis -> rcItem.right  -  lpdis -> rcItem.left,
                        lpdis -> rcItem.bottom  -  lpdis -> rcItem.top,
                        hdcBmp,
                        IMG_EXIT_ENABLE.left,
                        IMG_EXIT_ENABLE.top,
                        IMG_EXIT_ENABLE.right  -  IMG_EXIT_ENABLE.left,
                        IMG_EXIT_ENABLE.bottom  -  IMG_EXIT_ENABLE.top,
                        DEFAULT_TRANSPARENT_COLOR);
    }

     if (hdcBmp  !=  NULL  &&  hOldSel  !=  NULL)
    {
        SelectObject(hdcBmp,hOldSel);    
        DeleteDC(hdcBmp);

        hdcBmp  =  NULL;
        hOldSel  =  NULL;
    }

     if (hBmp  !=  NULL)
    {
        DeleteObject(hBmp);
        hBmp  =  NULL;
    }
    
     // Draw the text
    SetBkMode(lpdis -> hDC,TRANSPARENT);
    DrawText(lpdis -> hDC,m_pszBnExit, - 1 , & lpdis -> rcItem,DT_CENTER  |  DT_VCENTER);

}

// -----------------------------------------------------------------------------------------
// Description:
//     On the message WM_COMMAND and the HIWORD(wParam) is BN_CLICKED for the button exit
//
// ----------------------------------------------------------------------------------------------
void  CMainWnd::OnClickedBtnExit(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
{
    DestroyWindow(m_hWnd);
    PostQuitMessage( 0x00 );
}



// -----------------------------------------------------------------------------------------
// Description:
//     On the message WM_PAINT. 
//
// ----------------------------------------------------------------------------------------------
void  CMainWnd::OnPaint(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
{
    RECT rcWnd  =  { 0 };
    GetWindowRect(hWnd, & rcWnd);

    PAINTSTRUCT ps;
    HDC hdc  =  BeginPaint(hWnd, & ps);
     if (m_hdcBufBk  ==  NULL)
    {        

         // Create the memory DC for storing the background.
        m_hBmpBufBk  =  CreateCompatibleBitmap(hdc,rcWnd.right  -  rcWnd.left,rcWnd.bottom  -  rcWnd.top);
        m_hdcBufBk  =  CreateCompatibleDC(hdc);        
        m_hOldSelBufBk  =  SelectObject(m_hdcBufBk,m_hBmpBufBk);


         // Draw the background
        HPEN hPen = CreatePen(PS_SOLID, 1 ,RGB( 0 , 255 , 0 ));
        HPEN hOldPen = NULL;
        hOldPen = (HPEN)SelectObject(m_hdcBufBk,hPen);
         // the rect color
        HBRUSH hBrush  =  CreateSolidBrush(RGB( 0 , 255 , 0 ));
        HGDIOBJ hOldBrush  =  SelectObject(m_hdcBufBk,hBrush);
         // Draw
        Rectangle(m_hdcBufBk, 0 , 0 ,rcWnd.right  -  rcWnd.left  +   1 , rcWnd.bottom  -  rcWnd.top  +   1 );
         // Realse the resource
        SelectObject(m_hdcBufBk,hOldBrush);
        DeleteObject(hBrush);
        SelectObject(m_hdcBufBk,hOldPen);
        DeleteObject(hPen);
    }


    BitBlt(hdc,
            rcWnd.left,
            rcWnd.top,
            rcWnd.right  -  rcWnd.left,
            rcWnd.bottom  -  rcWnd.top,
            m_hdcBufBk,
            rcWnd.left,
            rcWnd.top,
            SRCCOPY);

    EndPaint(hWnd, & ps);

    UpdateWindow(m_hBnExit);


    

}