WM_CONTROL (in Entry Fields) - Parameters

id (USHORT)

Control window identity.

usnotifycode (USHORT)

Notify code.

EN_CHANGE

The content of the entry field control has changed, and the change has been displayed on the screen.
EN_KILLFOCUS
The entry field control is losing the focus.
EN_MEMERROR
The entry field control cannot allocate the storage necessary to accommodate window text of the length implied by the EM_SETTEXTLIMIT message.
EN_OVERFLOW
The entry field control cannot insert more text than the current text limit. The text limit may be changed with the EM_SETTEXTLIMIT message.

If the recipient of this message returns TRUE, then the entry field control retries the operation, otherwise it terminates the operation.

EN_SCROLL
The entry field control is about to scroll horizontally. This can happen in these circumstances:

• The application has issued a WinScrollWindow call 
  The content of the entry field control has changed
  
  The caret has moved
  
  The entry field control must scroll to show the caret position.
  EN_SETFOCUS
  The entry field control is receiving the focus.

  hwndcontrolspec (HWND)

  Entry field control window handle.

  ulReserved (ULONG)

  Reserved value, should be 0.

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