typedef struct tagCLIENTCREATESTRUCT { /* ccs */
HANDLE hWindowMenu;
UINT idFirstChild;
} CLIENTCREATESTRUCT;
The CLIENTCREATESTRUCT data structure contains information about the menu and first multiple document interface (MDI) child window of an MDI client window. An application passes a long pointer to this structure as the lpParam parameter of the CreateWindow function when creating an MDI client window.
hWindowMenu
Is the menu handle of the application's Window menu. An application can retrieve this handle from the MDI frame window's menu using the GetSubMenu function.
idFirstChild
Is the child window ID of the first MDI child window created. Windows increments the ID for each additional MDI child window that the application creates, and reassigns identifiers when the application destroys a window to keep the range of identifiers continuous. These identifiers are used in WM_COMMAND messages to the application's MDI frame window when a child window is selected from the Window menu, and should not conflict with any other command identifiers.
CreateWindow, GetSubMenu