Thread: About encapsulating a window class

I find the first parameter of the function WndProc is equal to the member variable of class MyWindow,
I want to omit the parameter in the function WndProc,how to do?
Look:

Code:

#include <windows.h>

class MyWindow
{
public:
 HWND m_hWnd;
public:
 MyWindow();
 BOOL CreateWin(LPCTSTR lpClassName,LPCTSTR lpWindowName,DWORD dwStyle,int x,int y,int nWidth,int nHeight,      
                   HWND hWndParent,HMENU hMenu,HINSTANCE hInstance,LPVOID lpParam );     
                
    BOOL ShowWindow(int iCmdShow) ;
    BOOL UpdateWindow();
    static LRESULT CALLBACK WndProc (HWND hWnd,UINT message, WPARAM wParam, LPARAM lParam);
        
};

MyWindow::MyWindow()
{
   m_hWnd=0;
}

BOOL MyWindow::CreateWin(LPCTSTR lpClassName, LPCTSTR lpWindowName,DWORD dwStyle,int x,int y,int nWidth,int nHeight,     
                         HWND hWndParent, HMENU hMenu,HINSTANCE hInstance, LPVOID lpParam)
{
   m_hWnd = ::CreateWindow (lpClassName,lpWindowName,dwStyle,x,y,nWidth,nHeight,hWndParent,hMenu,hInstance,lpParam); 
   if(NULL==m_hWand)
    return FALSE;
   else
    return TRUE;
}

BOOL MyWindow::ShowWindow(int iCmdShow)
{
    return ::ShowWindow(m_hWnd,iCmdShow);
}

BOOL MyWindow::UpdateWindow()
{
 return ::UpdateWindow (m_hWnd);
}

LRESULT MyWindow::WndProc (HWND hWnd,UINT message, WPARAM wParam, LPARAM lParam)
{
     HDC         hdc ;
     PAINTSTRUCT ps ;
     RECT        rect ;
    
     switch (message)
     {
     case WM_LBUTTONDOWN:
     MessageBox (hWnd,"WM_LBUTTONDOWN","Title",MB_OK);
          return 0 ;
    
    case WM_RBUTTONDOWN:
    MessageBox (hWnd,"WM_RBUTTONDOWN","Title",MB_OK);
          return 0 ;
   
     case WM_PAINT:
          hdc = BeginPaint (hWnd, &ps) ;
         
          GetClientRect (hWnd, &rect) ;
         
          DrawText (hdc, TEXT ("Hello, Windows 98!"), -1, &rect,
                    DT_SINGLELINE | DT_CENTER | DT_VCENTER) ;
         
          EndPaint (hWnd, &ps) ;
          return 0 ;
         
     case WM_DESTROY:
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hWnd, message, wParam, lParam) ;
}

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT ("HelloWin") ;
    MSG  msg ;
    class MyWindow MyObj;
    WNDCLASS wndclass;
    wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
    wndclass.lpfnWndProc   =  MyWindow::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 ("This program requires Windows NT!"),
                     TEXT ("HelloWin"), MB_ICONERROR) ;
         return 0 ;
    }
   MyObj.CreateWin(szAppName,TEXT("The Hello Program"),
                    WS_OVERLAPPEDWINDOW, CW_USEDEFAULT,CW_USEDEFAULT,
                    CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL, hInstance,NULL);
 
    MyObj.ShowWindow(SW_SHOWNORMAL); 
    MyObj.UpdateWindow();
   
    while (GetMessage (&msg, NULL, 0, 0))
    {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
    }
    return msg.wParam ;
}

You might want to post questions specifically about Windows programming in the Windows programming section of the forum (Windows Programming), but I'll try to help.

You can't pass a WndProc without the correct signature to the WNDCLASS struct, but you can do something like this:

Create a regular WndProc class and give this one to the WNDCLASS(EX) struct, like so:

Code:

LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
     static MyWindow* wnd = NULL;

     switch(msg)
     {
     case WM_CREATE:
          wnd = (MyWindow*)((LPCREATESTRUCT)lParam)->lpCreateParams;
          return 0;
     default:
          if(wnd)
               return wnd->WndProc(msg, wParam, lParam);
          else
               return DefWindowProc(hWnd, msg, wParam, lParam);
     }
}

// ...
WNDCLASSEX wcex;
// ...
wcex.WndProc = WndProc;
// ...

Then you can pass this as the last argument in the CreateWindow function within your class, like so:

Code:

hWnd = ::CreateWindow(lpClassName, lpWindowName, dwStyle, x, y, nWidth,
                             nHeight, hWndParent, hMenu, hInstance, this);

And change the window procedure within your class accordingly:

Code:

LRESULT WndProc(UINT msg, WPARAM wParam, LPARAM lParam)
{
     // ...
     return DefWindowProc(hWnd, // The HWND member of your class
          msg, wParam, lParam);
}

You may also want to use the class to store/encapsulate more information about the window, like the class name, window title, x/y position, and width/height for example.