An application sends an EM_CANUNDO message to determine whether an edit-control operation can be undone; that is, whether the control can respond to the EM_UNDO message.
EM_CANUNDO
wParam = 0; // not used; must be zero
lParam = 0; // not used; must be zero
This message has no parameters.
If the edit control can correctly process the EM_UNDO message, the return value is TRUE; otherwise, it is FALSE.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Edit Controls Overview, Edit Control Messages, EM_UNDO