TTextChangedEvent is the type of the OnChange event.
TTextChangedEvent = procedure (Sender: TObject; Pos, Count, LineChange: integer) of object;
TTextChangedEvent is the type of the OnChange event handler, which is called whenever text is modified.
Pos indicates position of changes.
Count indicates number of characters inserted (Count > 0) or deleted (Count < 0) at position Pos.
LineChange indicates changing of lines count.