我怎么这段代码封装成一类.放在头文件中调用.


#include <windows.h>
 
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
        
{
 static TCHAR szAppName[] = TEXT ("BlokOut1") ;
 HWND  hwnd ;
 MSG   msg ;
WNDCLASS    wndclass ;
wndclass.style= CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc= WndProc ;
wndclass.cbClsExtra= 0 ;
wndclass.cbWndExtra= 0 ;
wndclass.hInstance= hInstance ;
wndclass.hIcon= LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor= LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground= (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuName= NULL ;
wndclass.lpszClassName= szAppName ;
if (!RegisterClass (&wndclass))
 {
 MessageBox (  NULL, TEXT ("Program requires Windows NT!"),
        
              szAppName, MB_ICONERROR) ;
return 0 ;
         }
hwnd = CreateWindow (szAppName, TEXT ("Mouse Button Demo"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL) ;
ShowWindow (hwnd, iCmdShow) ;
UpdateWindow (hwnd) ;
while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}
 return msg.wParam ;
}

void DrawBoxOutline (HWND hwnd, POINT ptBeg, POINT ptEnd)
{
HDC hdc ;
 hdc = GetDC (hwnd) ;
SetROP2 (hdc, R2_NOT) ;
SelectObject (hdc, GetStockObject (NULL_BRUSH)) ;
Rectangle (hdc, ptBeg.x, ptBeg.y, ptEnd.x, ptEnd.y) ;
ReleaseDC (hwnd, hdc) ;
}
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam,LPARAM lParam)
{
static BOOL   fBlocking, fValidBox ;
static POINT  ptBeg, ptEnd, ptBoxBeg, ptBoxEnd ;
HDC     hdc ;
PAINTSTRUCT  ps ;
switch (message)
{
 case   WM_LBUTTONDOWN :
 ptBeg.x = ptEnd.x = LOWORD (lParam) ;
ptBeg.y = ptEnd.y = HIWORD (lParam) ;
DrawBoxOutline (hwnd, ptBeg, ptEnd) ;
SetCursor (LoadCursor (NULL, IDC_CROSS)) ;
fBlocking = TRUE ;
return 0 ;
case   WM_MOUSEMOVE :
if (fBlocking)
{
SetCursor (LoadCursor (NULL, IDC_CROSS)) ;
DrawBoxOutline (hwnd, ptBeg, ptEnd) ;
ptEnd.x = LOWORD (lParam) ;
ptEnd.y = HIWORD (lParam) ;
DrawBoxOutline (hwnd, ptBeg, ptEnd) ;
 }
 return 0 ;
case   WM_LBUTTONUP :
 if (fBlocking)
{
DrawBoxOutline (hwnd, ptBeg, ptEnd) ;
ptBoxBeg= ptBeg ;
ptBoxEnd.x= LOWORD (lParam) ;
ptBoxEnd.y= HIWORD (lParam) ;
SetCursor (LoadCursor (NULL, IDC_ARROW)) ;
fBlocking= FALSE ;
fValidBox= TRUE ;
InvalidateRect (hwnd, NULL, TRUE) ;
}
return 0 ;
case   WM_CHAR :
if (fBlocking & wParam == '\x1B')       // i.e., Escape
{
DrawBoxOutline (hwnd, ptBeg, ptEnd) ;
SetCursor (LoadCursor (NULL, IDC_ARROW)) ;
fBlocking = FALSE ;
}
 return 0 ;
case   WM_PAINT :
hdc = BeginPaint (hwnd, &ps) ;
if (fValidBox)
{
SelectObject (hdc, GetStockObject (BLACK_BRUSH)) ;
Rectangle     (      hdc, ptBoxBeg.x, ptBoxBeg.y,
 ptBoxEnd.x, ptBoxEnd.y) ;
}
if (fBlocking)
{
SetROP2 (hdc, R2_NOT) ;
 SelectObject (hdc, GetStockObject (NULL_BRUSH)) ;
Rectangle (hdc, ptBeg.x, ptBeg.y, ptEnd.x, ptEnd.y) ;
 }
        
EndPaint (hwnd, &ps) ;
 return 0 ;
 case   WM_DESTROY :
PostQuitMessage (0) ;
 return 0 ;
 }
 return DefWindowProc (hwnd, message, wParam, lParam) ;
        
}