HOWTO: Use One IsDialogMessage() Call for Many Modeless Dialogs

• Microsoft Win32 Software Development Kit (SDK)
• Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1
• Microsoft Windows 2000

SUMMARY

In the Windows environment, an application can implement more than one modeless dialog box with a single call to the IsDialogMessage() function. This can be done by using the following three-step method:

1. Maintain the window handle to the currently active modeless dialog box in a global variable.



2. Pass the global variable as the hDlg parameter to the IsDialogMessage() function, which is normally called from the application's main message loop.



3. Update the global variable whenever a modeless dialog box's window procedure receives a WM_ACTIVATE message, as follows:
   
   
   • If the dialog is losing activation (wParam is 0), set the global variable to NULL.
   
   
   
   • If the dialog is becoming active (wParam is 1 or 2), set the global variable to the dialog's window handle.
   
   
   

MORE INFORMATION

The information below demonstrates how to implement this technique.

1. Declare a global variable for the modeless dialog box's window handle as follows:

   
         HWND hDlgCurrent = NULL;
    




2. In the application's main message loop, add a call to the IsDialogMessage() function as follows:

   
         while (GetMessage(&msg, NULL, 0, 0))
            {
            if (NULL == hDlgCurrent || !IsDialogMessage(hDlgCurrent, &msg))
               {
               TranslateMessage(&msg);
               DispatchMessage(&msg);
               }
            }
    




3. In the modeless dialog box's window procedure, process the WM_ACTIVATE message as follows:
   

   
         switch (message)
            {
            case WM_ACTIVATE:
               if (0 == wParam)             // becoming inactive
                  hDlgCurrent = NULL;
               else                         // becoming active
                  hDlgCurrent = hDlg;
   
               return FALSE;
            }
    

Additional query words:

Keywords : kbDlg kbNTOS kbGrpUser kbWinOS
Version : WINDOWS:3.0,3.1
Platform : WINDOWS
Issue type : kbhowto