ID Number: Q77930
3.00
WINDOWS
Summary:
The system menu of an MDI child can be modified only after the
WM_CREATE message for the MDI child is processed. If an application
tries to modify the system menu of an MDI child during the processing
of the child's WM_CREATE message, the system menu will not be changed.
More Information:
It is common to try to alter a window's system menu during the
processing of its WM_CREATE message. This method has no effect on the
system menu of an MDI child, however, because of the way a MDI child
window is created:
1. The MDI client window calls the CreateWindowEx function to create
the window.
2. Then, the MDI client window replaces the default system menu with
the special MDI child system menu.
The WM_CREATE message is sent to the child window by CreateWindowEx.
Changes to the MDI child's system menu on WM_CREATE have no effect
because the MDI client assigns a special MDI system menu to the child
after CreateWindowEx returns.
To work around this design decision, the child window procedure can
post a custom message to itself during the processing of its WM_CREATE
message. This custom message is processed after the MDI client has
finished creating the MDI child. The code for this workaround might
resemble the following:
#define WM_ADDMENUITEM (WM_USER+1)
LONG FAR PASCAL MDIChildWndProc(HWND hWnd,
WORD wMsg,
WORD wParam,
LONG lParam)
{
switch (wMsg)
{
case WM_CREATE:
PostMessage(hWnd, WM_ADDMENUITEM, 0, 0L);
break;
case WM_ADDMENUITEM:
{
HMENU hMenu;
hMenu = GetSystemMenu(hWnd, FALSE);
InsertMenu(hMenu, -1, MF_BYPOSITION, IDM_NEW,
(LPSTR)"New Item\0");
DrawMenuBar(hWnd);
}
break;
default:
return DefMDIChildProc(hWnd, wMsg, wParam, lParam);
}
return 0;
}
Additional reference words: 3.00