C / C++ / MFC

2-Nov-02 4:55

Normally messages are cought into a so called Message Loop and are parsed using the TranslateMessage and DispatchMessage. The DispatchMessage does two things:

1 - it calls the right Window procedure
2 - it posts the return value back to the os

Well I want to redesign option 1, but I don't want to redesign option 2, so does anyone know what DispatchMessage really does? Maybe WTL/ATL have also there implementations, so if anyone knows where these are, I would be pleased if anyone tells me where.

Sjoerd van Leent

LPCTSTR Dutch = TEXT("Double Dutch Smile | :)

");

ian mariano2-Nov-02 6:38

2-Nov-02 6:38

If you poke around in the headers you'll see some interesting things.

MFC, ATL, and WTL use #defines to set up message handling for their window classes. I think you're really wanting to implement your own message handling for your window classes. DispatchMessage() is a Win32 API that [MSDN] "dispatches a message to a window procedure. It is typically used to dispatch a message retrieved by the GetMessage function." You can't really roll your own version of DispatchMessage.

Take a look at this interesting snippet from <atlwin.h> line 1524:

#define BEGIN_MSG_MAP(theClass) \
public: \
	BOOL ProcessWindowMessage(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT& lResult, DWORD dwMsgMapID = 0) \
	{ \
		BOOL bHandled = TRUE; \
		hWnd; \
		uMsg; \
		wParam; \
		lParam; \
		lResult; \
		bHandled; \
		switch(dwMsgMapID) \
		{ \
		case 0:

You should probably research it a bit before you implement your own, because you'll have to be tight on processing windows messages using Win32 wrapped by C++.

-- ian

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano

http://www.ian-space.com/

S van Leent2-Nov-02 10:12

2-Nov-02 10:12

imariano wrote:
...you'll have to be tight on processing windows messages using Win32 wrapped by C++.

I know about thunking or joining, or storing the this pointer, but I'm just curious, it should be possible...

LPCTSTR Dutch = TEXT("Double Dutch Smile | :)

");

Paul M Watt2-Nov-02 10:14

Paul M Watt

2-Nov-02 10:14

Here is the implementation for DispatchMessage from WINE.

LONG WINAPI DispatchMessageW( const MSG* msg )
{
    WND * wndPtr;
    LONG retval;
    int painting;
    WNDPROC winproc;

      /* Process timer messages */
    if ((msg->message == WM_TIMER) || (msg->message == WM_SYSTIMER))
    {
	if (msg->lParam)
        {
/*            HOOK_CallHooks32W( WH_CALLWNDPROC, HC_ACTION, 0, FIXME ); */

            /* before calling window proc, verify whether timer is still valid;
               there's a slim chance that the application kills the timer
	       between GetMessage and DispatchMessage API calls */
            if (!TIMER_IsTimerValid(msg->hwnd, (UINT) msg->wParam, (HWINDOWPROC) msg->lParam))
                return 0; /* invalid winproc */

	    return CallWindowProcW( (WNDPROC)msg->lParam, msg->hwnd,
                                   msg->message, msg->wParam, GetTickCount() );
        }
    }

    if (!(wndPtr = WIN_GetPtr( msg->hwnd )))
    {
        if (msg->hwnd) SetLastError( ERROR_INVALID_WINDOW_HANDLE );
        return 0;
    }
    if (wndPtr == WND_OTHER_PROCESS)
    {
        if (IsWindow( msg->hwnd ))
            ERR( "cannot dispatch msg to other process window %x\n", msg->hwnd );
        SetLastError( ERROR_INVALID_WINDOW_HANDLE );
        return 0;
    }
    if (!(winproc = wndPtr->winproc))
    {
        WIN_ReleasePtr( wndPtr );
        return 0;
    }
    painting = (msg->message == WM_PAINT);
    if (painting) wndPtr->flags |= WIN_NEEDS_BEGINPAINT;
    WIN_ReleasePtr( wndPtr );
/*    HOOK_CallHooks32W( WH_CALLWNDPROC, HC_ACTION, 0, FIXME ); */

    SPY_EnterMessage( SPY_DISPATCHMESSAGE, msg->hwnd, msg->message,
                      msg->wParam, msg->lParam );
    retval = CallWindowProcW( winproc, msg->hwnd, msg->message,
                              msg->wParam, msg->lParam );
    SPY_ExitMessage( SPY_RESULT_OK, msg->hwnd, msg->message, retval,
                     msg->wParam, msg->lParam );

    if (painting && (wndPtr = WIN_GetPtr( msg->hwnd )) && (wndPtr != WND_OTHER_PROCESS))
    {
        BOOL validate = ((wndPtr->flags & WIN_NEEDS_BEGINPAINT) && wndPtr->hrgnUpdate);
        wndPtr->flags &= ~WIN_NEEDS_BEGINPAINT;
        WIN_ReleasePtr( wndPtr );
        if (validate)
        {
            ERR( "BeginPaint not called on WM_PAINT for hwnd %04x!\n", msg->hwnd );
            /* Validate the update region to avoid infinite WM_PAINT loop */
            RedrawWindow( msg->hwnd, NULL, 0,
                          RDW_NOFRAME | RDW_VALIDATE | RDW_NOCHILDREN | RDW_NOINTERNALPAINT );
        }
    }
    return retval;
}

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

S van Leent2-Nov-02 10:21

2-Nov-02 10:21

I also looked into atlapp.h of WTL70 there is also another type of function which does this.

But do you've also the TranslateMessage function, and other functions which apply to a message loop. I guess that what I really want to do is fading the CALLBACK out of sight.

LPCTSTR Dutch = TEXT("Double Dutch Smile | :)

");

ian mariano2-Nov-02 15:19

2-Nov-02 15:19

Never thought to look @ Wine Wink | ;)

Heheh. Still, quite informative that code snippet, and the psuedocode one below from MSJ...which looks like it still allows for 16-bit (!) thingamadoodles.

TranslateMessage allows for "preprocessing" of Virtual key messages into character messages, which are then posted to the calling thread's message queue.

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano - http://www.ian-space.com/

S van Leent2-Nov-02 10:54

Re: Strange List Box Problem

2-Nov-02 10:54

Got this code out of a MSJ from 1997

MS Systems journal example:

 //=================================================
 // Matt Pietrek
 // Microsoft Systems Journal, March 1997
 // Pseudocode for ring 3 portion of DispatchMessage
 //=================================================
 
 LONG DispatchMessageA( CONST MSG *lpmsg )
 {
     return DispatchMessageWorker( lpmsg, 1 ); // 0 == UNICODE, 1 = ANSI
 }
 
 LONG DispatchMessageWorker( CONST MSG *lpmsg, BOOL fAnsi )
 {
     if ( lpmsg->message == 0xFFFE0000 )
     {
         _UserSetLastError( ERROR_INVALID_PARAMETER );
         return 0;       
     }
 
     // If we have a non-null HWND, convert it to a pointer to the user mode
     // WND structure.  We'll use this ptr extensively.
     if ( lpmsg->hwnd )
     {
         pWnd = @ValidateHwnd( lpmsg->hwnd );
         if ( !pWnd )
             return 0;
     }
     else
         pWnd = 0;
 
     if ( (lpmsg->message != WM_TIMER) && (lpmsg->message != WM_SYSTIMER) )
     {
 
 begin_normal_message:
 
         if ( pWnd == 0 )    // Sanity check.  We'd better have a valid window!
             return 0;
 
         DWORD save_wParam = lpmsg->wParam;
 
         if ( (lpmsg->message != WM_PAINT) && !(pWnd->someFlags9E & 4) )
         {
             if ( IsWindowUnicode( lpmsg->hwnd ) )
             {
                 if ( fAnsi )
                     RtlMBMessageWParamCharToWCS( lpmsg->message, save_wParam );
                 else
                     RtlWCSMessageWParamCharToMB( lpmsg->message, save_wParam );
             }
 
             // Is the high bit in the wndproc address set?  If so, this is a
             // 16 bit window, and pfnWndProc is a 16:16 far address.  To get
             // the real address, turn off the high bit (0x80000000)
             if ( 0 == (pWnd->pfnWndProc & 0x80000000) )
             {
                 pWnd->pfnWndProc(   lpmsg->hwnd, lpmsg->message,
                                     lpmsg->wParam, lpmsg->lParam );
             }
             else
             {
                 pfnWowWndProcEx( lpmsg->hwnd, lpmsg->message, save_wParam,
                                  lpmsg->lParam, lpmsg->message, pWnd->0x90 );
             }
         }
         else    // WM_PAINT, or something else...
         {
             if ( fAnsi )
                 _RtlMBMessageWParamCharToWCS( lpmsg->message, save_wParam );        
 
             _NtUserDispatchMessage( lpmsg );        
         }
 
         lpmsg->wParam = save_wParam;
     }
     else    // WM_TIMER && WM_SYSTIMER
     {
         TIMERPROC pfnTimerCallback = lpmsg->lParam;
 
         if ( pfnTimerCallback == 0 )
             goto begin_normal_message;
 
         if ( lpmsg->message == WM_SYSTIMER )
             return _NtUserDispatchMessage( lpmsg );
 
         return pfnTimerCallback(    lpmsg->hwnd,
                                     lpmsg->message,
                                     lpmsg->wParam,      // wTimerId
                                     GetTickCount() );   // actually, an inline
                                                         // version of the code
                                                         // in KERNEL32.DLL
     }
 }

LPCTSTR Dutch = TEXT("Double Dutch Smile | :)

");

Strange List Box Problem

Ayush2-Nov-02 4:36

Ayush

2-Nov-02 4:36

Im designing a simple interface using MFC. When i add a list box to the main dialog, build it and then run it, the exe pops-up and works as expected. If i then go to the classwizard and add a Control-Clistbox variable to this list box and rebuild it and run it, nothing happens. The exe doesn turn up at all, the mouse pointer just changes to hour-glass and then back to the pointer. Anybody know why?

Ayush

ian mariano2-Nov-02 10:40

Re: Strange List Box Problem

2-Nov-02 10:40

If you just add the CListBox to the class and not the dialog, you're only getting a class member which is not tied to anything in the dialog, and it's never going to show up if you don't do some extra work.

If you want to wire up the list box into your dialog class, do what you did to add the dialog to the form, then use the ClassWizard to associate the list box to a class member.

Using ClassWizard[^], and the CListBox reference[^]

-- Ian

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano - http://www.ian-space.com/

Ayush2-Nov-02 14:35

Ayush

2-Nov-02 14:35

Dear Ian,
I dont seem to understand what you mean. After adding the list box to the dialog, i give it a control id using the properties menu on right-click. Then i run class-wizard and assign a Control variable of Clistbox type to this control ID. On Building it, i get no errors, but when i run it, it doesnt do anything, as expalined in my earlier post. Removing this variable makes it work though.

Re: Strange List Box Problem

ian mariano2-Nov-02 15:11