An application sends an EM_EMPTYUNDOBUFFER message to reset (clear) the undo flag of an edit control. The undo flag is set whenever an operation within the edit control can be undone.
wParam
This parameter is not used.
lParam
This parameter is not used.
The undo flag is automatically cleared whenever the edit control receives a WM_SETTEXT or EM_SETHANDLE message.
EM_CANUNDO, EM_SETHANDLE, EM_UNDO, WM_SETTEXT