WM_INITMENU
hmenuInit = (HMENU) wParam; /* handle of menu to initialize */The WM_INITMENU message is sent when a menu is about to become active. It occurs when the user clicks an item on the menu bar or presses a menu key. This allows an application to modify the menu before it is displayed.
hmenuInit
Value of wParam. Identifies the menu to be initialized.
An application should return zero if it processes this message.
This message is sent only when a menu is first accessed; only one WM_INITMENU message is generated for each access. This means, for example, that moving the mouse across several menu items while holding down the button does not generate new messages. WM_INITMENU does not provide information about menu items.