From: "Don" 
Subject: WIN32 CALLBACK problems    -   PLEASE HELP
Date: 1997/11/17
Message-ID: 
Organization: Dummy connection record
Newsgroups: comp.lang.c++,comp.os.ms-windows.programmer.win32,fido.win32,microsoft.public.win32,microsoft.public.win32.programmer,microsoft.public.win32.programmer.kernel


Please e-mail responses to:     puppy@dog.astra.co.uk
your help would be greatly appreciated
If you need help- just ask!!


Here's the problem:

I want to encapsulate my WIN32 application in a class "DbApp"
However when I try to assign my "WndProc" function to the
WindowsClass.lpfnWndProc variable for WindowsClass registration I get the
ERROR:

"Cannot convert 'long (__stdcall DbApp::*)(void *,unsigned int,unsigned
int,long)' to 'long (__stdcall *)(void *,unsigned int,unsigned int,long)'"

Notice the (__stdcall DbApp::*) to (__stdcall *) difference!
I don't understand what I need to do to allow the Windows-API to access my
"class member functions" without it being a global function,
I tried many different combinations of pointer declarations with no avail
PLEAS HELP!




here's my source code:
////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////
"testapp.cpp"

#include "DbApp.cpp"
#include 
#include 

int WINAPI WinMain(HINSTANCE hThisInst, HINSTANCE hPrevInst, LPSTR lpszArgs,
int nWinMode)
   {
      DbApp DataBase(hThisInst, nWinMode);

      // insert and run setup program here if database isn't valid for any
reason

      return DataBase.Run_Msg_Loop();
   }



////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////
                                                                "DbApp.cpp"


#include 
#include 
class DbApp
   {
      // StatusWindow status(hWnd);                         // status.hwnd
      // ScheduleWindow schedule(hWnd);                     // schedule.hwnd
      // DailyLogWindow log(hWnd);                          // log.hwnd
      LPCTSTR lpszName;                                     // MainWindow
class name
      LPCTSTR lpszTitle;                                    // MainWindow
titlebar

   public:
      MSG msg;
      HINSTANCE hInst;                                      // the handle
for this instance
      HWND hWnd;                                            // the handle
for the window
      WPARAM Run_Msg_Loop();                                // the message
loop for the main window
                                                            // returning
from this function will exit the program!
      DbApp::DbApp(HINSTANCE hThisInst, int nCmdShow);      // class
constructor
                                                            // window
definition and registration
      LRESULT CALLBACK WndProc(HWND hwndReceiver, UINT uMsg, WPARAM wParam,
LPARAM lParam);
   };

////////////////////////////////////////////////////////////////////////////
////////////////////////

DbApp::DbApp(HINSTANCE hThisInst, int nCmdShow)
   {
      lpszName = "DbApp";         // MainWindow class name
      lpszTitle = "Main";          // MainWindow titlebar
      // DEFINE & REGISTER WINDOWS CLASS
      WNDCLASSEX wc;
      wc.style            = CS_HREDRAW | CS_VREDRAW;


//  **  **  **  **  **  **  **  **  **  **  **  **    HERE'S MY PROBLEM
**  **  **  **  **  **  **  **  **  **  **  **  **

      wc.lpfnWndProc      = &DbApp::WndProc;       // tried (WNDPROC),
WndProc, &WndProc and others

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


      wc.cbClsExtra         = 0;
      wc.cbWndExtra       = 0;
      wc.hInstance            = hThisInst;
      wc.hIcon                   = LoadIcon(NULL, IDI_WINLOGO); // change
this later
      wc.hCursor              = LoadCursor(NULL, IDC_ARROW);
      wc.hbrBackground   = (HBRUSH)(COLOR_WINDOW+1);
      wc.lpszMenuName     = NULL;
      wc.lpszClassName    = lpszName;
      wc.cbSize           = sizeof(WNDCLASSEX);
      wc.hIconSm          = LoadIcon(NULL, IDI_WINLOGO); // change this
later
      RegisterClassEx(&wc);
      hInst = hThisInst;                                 // save the current
instance handle
      hWnd = CreateWindowEx(WS_EX_TOPMOST,
                            lpszName,
                            lpszTitle,
                            WS_CAPTION | WS_MAXIMIZEBOX | WS_MINIMIZEBOX
                            | WS_VISIBLE, // WS_EX_TOOLWINDOW
                            CW_USEDEFAULT, CW_USEDEFAULT, // X,Y location
                             60, 20,                      // width, height
                            NULL,
                            NULL,
                            hInst,
                            NULL);

      if(hWnd)
         {
            ShowWindow(hWnd, nCmdShow);
            UpdateWindow(hWnd);
         }
   }

////////////////////////////////////////////////////////////////////////////
////////////////////////

WPARAM DbApp::Run_Msg_Loop()
   {
      while(GetMessage(&msg, NULL, 0, 0))
         {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
         }
      return(msg.wParam);
   }

////////////////////////////////////////////////////////////////////////////
////////////////////////

LRESULT CALLBACK DbApp::WndProc(HWND hwndReceiver, UINT uNewMsg, WPARAM
wParam, LPARAM lParam)
   {
      switch(uNewMsg)
         {
            case WM_COMMAND:
               switch(LOWORD(wParam))
                  {    /*
                     case IDM_EXIT:
                        DestroyWindow(hWnd);
                        break;   */
                  }
            case WM_DESTROY:
               PostQuitMessage(0);
               break;
            default:
               return(DefWindowProc(hWnd, uNewMsg, wParam, lParam));
         }
      return(0L);
   }

////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////


PLEASE HELP
Don E. Stewart II
puppy@dog.astra.co.uk