coming from any control, regardless of its identifier
\end{itemize}
+Another standard special identifier value is {\tt wxID\_NONE}: this is a value
+which is not matched by any other id.
+
wxWidgets also defines a few standard command identifiers which may be used by
the user code and also are sometimes used by wxWidgets itself. These reserved
identifiers are all in the range between {\tt wxID\_LOWEST} and
wxID_PREVIEW,
wxID_ABOUT,
wxID_HELP_CONTENTS,
+ wxID_HELP_INDEX,
+ wxID_HELP_SEARCH,
wxID_HELP_COMMANDS,
wxID_HELP_PROCEDURES,
wxID_HELP_CONTEXT,