HOWTO: Ignore WM_MOUSEACTIVATE Message for an MDI Window

• Microsoft Windows Software Development Kit (SDK)
• Microsoft Win32 Software Development Kit (SDK)

SUMMARY

To make an MDI window to become active and have the caret be in the same position as when the window was last active you need to process the WM_MOUSEACTIVATE message and return MA_ACTIVATEANDEAT for the first time. Therefore, you need to set a Boolean flag in the WM_MDIACTIVATE message so that the return is set only once. The sample code below can be used to modify the MULTIPAD sample application. Also, the following is documentation on MA_ACTIVATE* messages, taken from the Windows 3.0 final SDK README.WRI file:

   WM_MOUSEACTIVATE

   Return Value    The return value specifies whether the window
                   should be activated and whether the mouse event
                   should be discarded. It must be one of the
                   following values:

                   Value                   Meaning
                   -----                   -------
                   MA_ACTIVATE             Activate the window.
                   MA_NOACTIVATE           Do not activate the window.
                   MA_ACTIVATEANDEAT       Activate the window and
                                           discard the mouse event. 

Sample Code

   /* --- multipad.c  MPMDIWndProc section --- */ 

    case WM_MOUSEACTIVATE:   // Added.
        if (bEatMessage) {
           bEatMessage = FALSE;
           return (LONG)MA_ACTIVATEANDEAT ;
        }
        /* Else, break. */ 
        break;

    case WM_MDIACTIVATE:
        /* If you are activating this child, remember it. */ 
        if (wParam){
          hwndActive     = hwnd;
          hwndActiveEdit = (HWND)GetWindowWord (hwnd, GWW_HWNDEDIT);
          bEatMessage = TRUE;      // added
        }
        else{
              hwndActive     = NULL;
              hwndActiveEdit = NULL;
        }
        break; 

Keywords          : kbMDI kbNTOS kbGrpUser kbWinOS kbWndw kbWndwMsg 
Version           : 
Platform          : 
Issue type        : kbhowto 

Last Reviewed: March 5, 1999