How to Ignore WM_MOUSEACTIVATE Message for an MDI Window

• Microsoft Windows Software Development Kit (SDK) versions 3.0 and 3.1
• Microsoft Win32 Application Programming Interface (API) included with:

      - Microsoft Windows NT versions 3.5 and 3.51
      - Microsoft Windows 95 version 4.0
  

In order 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 we're activating this child, remember it */
     if (wParam){
       hwndActive     = hwnd;
       hwndActiveEdit = (HWND)GetWindowWord (hwnd, GWW_HWNDEDIT);
       bEatMessage = TRUE;      // added
     }
     else{
           hwndActive     = NULL;
           hwndActiveEdit = NULL;
     }
     break;