After registering its window classes, an MDI application can create its windows. First, it creates its frame window by using the CreateWindow or CreateWindowEx function. After creating its frame window, the application creates its client window, again by using CreateWindow or CreateWindowEx. The application should specify MDICLIENT as the client window's class name; MDICLIENT is a preregistered window class defined by the system. The lpvParam parameter of CreateWindow or CreateWindowEx should point to a CLIENTCREATESTRUCT structure. This structure contains the members described in the following table:
| Member | Description |
|---|---|
| hWindowMenu | Handle to the Window menu used for controlling MDI child windows. As child windows are created, the application adds their titles to the Window menu as menu items. The user can then activate a child window by clicking its title on the Window menu. |
| idFirstChild | Specifies the identifier of the first MDI child window. The first MDI child window created is assigned this identifier. Additional windows are created with incremented window identifiers. When a child window is destroyed, the system immediately reassigns the window identifiers to keep their range contiguous. |
When a child window's title is added to the Window menu, the system assigns an identifier to the child window. When the user clicks a child window's title, the frame window receives a WM_COMMAND message with the identifier in the wParam parameter. You should specify a value for the idFirstChild member that does not conflict with menu-item identifiers in the frame window's menu.
Multipad's frame window procedure creates the MDI client window while processing the WM_CREATE message. The following example shows how the client window is created.
case WM_CREATE:
{
CLIENTCREATESTRUCT ccs;
// Retrieve the handle to the Window menu and assign the
// first child window identifier.
ccs.hWindowMenu = GetSubMenu(GetMenu(hwnd), WINDOWMENU);
ccs.idFirstChild = IDM_WINDOWCHILD;
// Create the MDI client window.
hwndMDIClient = CreateWindow( "MDICLIENT", (LPCTSTR) NULL,
WS_CHILD | WS_CLIPCHILDREN | WS_VSCROLL | WS_HSCROLL,
0, 0, 0, 0, hwnd, (HMENU) 0xCAC, hInst, (LPSTR) &ccs);
ShowWindow(hwndMDIClient, SW_SHOW);
}
break;
Titles of child windows are added to the bottom of the Window menu. If the application adds strings to the Window menu by using the AppendMenu function, these strings can be overwritten by the titles of the child windows when the Window menu is repainted (whenever a child window is created or destroyed). An MDI application that adds strings to its Window menu should use the InsertMenu function and verify that the titles of child windows have not overwritten these new strings.
Use the WS_CLIPCHILDREN style to create the MDI client window to prevent the window from painting over its child windows.