An entry field is always owned by another window. A WM_CONTROL notification message is sent to the owner whenever an event occurs in the entry field. This message contains a notification code that specifies the exact nature of the event. An entry field can send the notification codes described in the following table to its owner.
旼컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿙otification Code 쿏escription � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿐N_CHANGE 쿔ndicates that the contents of an entry � � 쿯ield have changed. � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿐N_INSERTMODETOGGLE 쿔ndicates that the insert mode has been � � 퀃oggled. � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿐N_KILLFOCUS 쿔ndicates that an entry field has lost � � 퀃he keyboard focus. � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿐N_MEMERROR 쿔ndicates that an entry field cannot � � 쿪llocate enough memory to perform the � � 퀁equested operation, such as extending � � 퀃he text limit. � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿐N_OVERFLOW 쿔ndicates that either the user or the � � 쿪pplication attempted to exceed the text� � 쿹imit. � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿐N_SCROLL 쿔ndicates that the text in an entry � � 쿯ield is about to scroll. � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿐N_SETFOCUS 쿔ndicates that an entry field received � � 퀃he keyboard focus. � 읕컴컴컴컴컴컴컴컴컴컨컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�
An application typically ignores notification messages from an entry field, thereby allowing default text editing to occur. For more specialized uses, an application can use notification messages to filter input. For example, if an entry field is intended for numbers only, an application can use the EN_CHANGE notification code to check the contents of the entry field each time the user enters a non-numeric character.
As an alternative, an application can prevent inappropriate characters from reaching an entry field by using EN_SETFOCUS and EN_KILLFOCUS, in filter code, placed in the main message loop. Whenever the entry field has the keyboard focus, the filter code can intercept and filter WM_CHAR messages before the WinDispatchMsg function passes them to the entry field. An application also can respond to certain keystrokes, such as the Enter key, as long as the entry-field control has the keyboard focus.