How to get wndproc to handle messages to multiple windows

Question

I've been trying to get a wndproc to successfully receive messages from the message queue and process them according to my code but it isn't working the way I want it to, what I'd like it to do is determine which window received WM_DESTROY or WM_CLOSE and call code specific to which window was closed, but for some reason at the moment it's doing nothing. After alot of experimentation I've gotten it to function partially in different ways but it seems like each implementation doesn't function just the right way. Here's my lastest unsuccessful code:

    while (GetMessage (&messages, NULL, 0, 0))
{
    /* Translate virtual-key messages into character messages */
    TranslateMessage(&messages);
    /* Send message to WindowProcedure */
    DispatchMessage(&messages);
}

/* The program return-value is 0 - The value that PostQuitMessage() gave */
return messages.wParam;
}


/*  This function is called by the Windows function DispatchMessage()  */


LRESULT CALLBACK Proc2(HWND mainwin, UINT message, WPARAM wParam, LPARAM lParam )
{
switch (message)                  /* handle the messages */
{
                       case WM_DESTROY:
                       const HWND active_window = GetActiveWindow();
                       if (active_window == mainwin)
                                {
                                   PostQuitMessage(0);
                                }
                                   if (active_window == hwnd2)
                                   {
                                                 PostQuitMessage(0);
                                                EnableWindow (mainwin, true);
                                   }
                                   break;
} 
 switch (wParam)                  /* handle the messages */
{
              case ID_2 :
            PostQuitMessage(0);
            break;
              case ID_1 :
               ShowWindow (hwnd2, SW_SHOW);     
               break;
                            default:                      /* for messages that we don't deal with */
        return DefWindowProc (mainwin, message, wParam, lParam); 
                    break;
}  

    return 0;
}

Here is the code I tried with multiple window procedures

while (GetMessage (&messages, NULL, 0, 0))
{
    /* Translate virtual-key messages into character messages */
    TranslateMessage(&messages);
    /* Send message to WindowProcedure */
    DispatchMessage(&messages);
}

/* The program return-value is 0 - The value that PostQuitMessage() gave */
return messages.wParam;
}


/*  This function is called by the Windows function DispatchMessage()  */


LRESULT CALLBACK Proc2(HWND mainwin, UINT message, WPARAM wParam, LPARAM lParam )
{
switch (message)                  /* handle the messages */
{
                       case WM_DESTROY:
                                   PostQuitMessage(0);
                                   break;
} 
 switch (wParam)                  /* handle the messages */
{
              case ID_2 :
            PostQuitMessage(0);
            break;
              case ID_1 :
               ShowWindow (hwnd2, SW_SHOW);     
               break;
                            default:                      /* for messages that we don't deal with */
        return DefWindowProc (mainwin, message, wParam, lParam); 
                    break;
}  

    return 0;
}    
LRESULT CALLBACK Proc3(HWND hwnd2, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
           case WM_DESTROY:
EnableWindow (mainwin, false);
                break;
case WM_CLOSE:
EnableWindow (mainwin, false);
break;
}
switch (wParam)
{
   default:
           return DefWindowProc (hwnd2, message, wParam, lParam);
           break;
           }
           return 0;
           }

score 1 · Answer 1 · answered Dec 06 '12 at 13:20

1

You say,

"what I'd like it to do is determine which window received WM_DESTROY or WM_CLOSE"

The simple answer is that the window that's receiving UINT message is HWND mainwin.

If you want to know "yes, but which of my windows is HWND mainwin?" then one way to do that is, when you create a window, you remember what its window handle is, and store it somewhere (e.g. as a global variable).

Apart from that, it isn't clear why you're calling GetActiveWindow(), nor what functionality you want to implement.

answered Dec 06 '12 at 13:20

ChrisW

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CW because this isn't much of an answer, but I thought it too long to post as a comment, requesting clarifications to the question. – ChrisW Dec 06 '12 at 13:22
are you saying because the wndproc is to hwnd mainwin that only messages generated by the mainwin (like hitting the x in the topright of the window) will go to that wndproc? then do I have to create a secodn wndproc? I've tried that and it seemed like my messages from the second window hwnd2 still went to the first wndproc, the reason getactivewindow is there is because I assumed WM_DESTROY would be sent to that wndproc regardless of which window generated the message, so I should use that to figure out which window generated the message. I will edit my q to include the double wndproc failcode – user1882226 Dec 06 '12 at 13:32
@user1882226 You specify the wndproc when you create the window. If you create two windows using the same wndproc, then the same wndproc will be used for both windows. When wndproc is invoked, the HWND parameter will then tell you which of these two windows is receiving the message. Alternatively you can use a different wndproc for different windows. A wndproc is like a C++ class, and a HWND is like a C++ instance of that class. If you have two slightly different window behaviours, you could define two slightly different wndprocs, which both delegate to a common subroutine to handle ... – ChrisW Dec 06 '12 at 13:41
... whatever messages they have common/shared behaviour for. – ChrisW Dec 06 '12 at 13:41
Normally the wndproc parameter would be called hWnd, not "mainwin" ... calling it 'mainwin' implies you know that it's your main window. If it were called hWnd then I'd expect to see code like `if (hWnd == mainwin) { ... } else if (hWnd = secondwin) { ... }` where `mainwin` and `secondwin` are global variables in which you stored the handles of the two windows you created. – ChrisW Dec 06 '12 at 13:45
How do I specify the wndproc when creating the window? can you give me some example code? This is what I'm using: mainwin = CreateWindowEx (0, szClassName, "Mafia", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 375, NULL, hmenu, hThisInstance, NULL ); Sorry for asking stupid questions also, this is my first win32 ap >_ – user1882226 Dec 06 '12 at 13:47
@user1882226 What is your `szClassName`? It's the result of calling `RegisterClass`, which registers a `WNDCLASS`, one of whose elements specifies the `WNDPROC`. – ChrisW Dec 06 '12 at 13:55
I can't give you sample code. How are writing this, your first win32 app? You should probably be using the online help e.g. [WNDCLASS](http://msdn.microsoft.com/en-us/library/windows/desktop/ms633576(v=vs.85).aspx), **and** starting with a tutorial (online, included in the SDK, and/or in book form) which includes already-working sample codes. – ChrisW Dec 06 '12 at 13:57
1

After looking through my code to try and find where it specifies the wndproc I just noticed that szclassname thing, I created a second one and adjusted it to szclassname2 and it broke my code but I can figure it out from here, thanks for all your help! :) – user1882226 Dec 06 '12 at 13:58

How to get wndproc to handle messages to multiple windows

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