Identifies the item selected. If the selected item is a menu item, nItemID contains the menu-item ID. If the selected item contains a pop-up menu, nItemID contains the pop-up menu index, and hSysMenu contains the handle of the main (clicked-on) menu.
Contains a combination of the following menu flags:
MF_BITMAP Item is a bitmap.
MF_CHECKED Item is checked.
MF_DISABLED Item is disabled.
MF_GRAYED Item is dimmed.
MF_MOUSESELECT Item was selected with a mouse.
MF_OWNERDRAW Item is an owner-draw item.
MF_POPUP Item contains a pop-up menu.
MF_SEPARATOR Item is a menu-item separator.
MF_SYSMENU Item is contained in the Control menu.
If nFlags contains MF_SYSMENU, identifies the menu associated with the message. If nFlags contains MF_POPUP, identifies the handle of the main menu. If nFlags contains neither MF_SYSMENU nor MF_POPUP, it is unused.
If nFlags contains 0xFFFF and hSysMenu contains 0, Windows has closed the menu because the user pressed the ESC key or clicked outside the menu.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.