added wxMessageQueue class for inter-thread communications

[wxWidgets.git] / docs / latex / wx / event.tex

\section{\class{wxEvent}}\label{wxevent}

An event is a structure holding information about an event passed to a
callback or member function. {\bf wxEvent} used to be a multipurpose
event object, and is an abstract base class for other event classes (see below).

For more information about events, see the \helpref{Event handling overview}{eventhandlingoverview}.

\perlnote{In wxPerl custom event classes should be derived from
\texttt{Wx::PlEvent} and \texttt{Wx::PlCommandEvent}.}

\wxheading{Derived from}

\helpref{wxObject}{wxobject}

\wxheading{Include files}

<wx/event.h>

\wxheading{Library}

\helpref{wxBase}{librarieslist}

\wxheading{See also}

\helpref{wxCommandEvent}{wxcommandevent},\rtfsp
\helpref{wxMouseEvent}{wxmouseevent}

\latexignore{\rtfignore{\wxheading{Members}}}


\membersection{wxEvent::wxEvent}\label{wxeventctor}

\func{}{wxEvent}{\param{int }{id = 0}, \param{wxEventType }{eventType = {\tt wxEVT\_NULL}}}

Constructor. Should not need to be used directly by an application.


\membersection{wxEvent::m\_propagationLevel}\label{wxeventmpropagationlevel}


\member{int}{m\_propagationLevel}

Indicates how many levels the event can propagate. This member is protected and
should typically only be set in the constructors of the derived classes. It
may be temporarily changed by \helpref{StopPropagation}{wxeventstoppropagation} 
and \helpref{ResumePropagation}{wxeventresumepropagation} and tested with 
\helpref{ShouldPropagate}{wxeventshouldpropagate}.

The initial value is set to either {\tt wxEVENT\_PROPAGATE\_NONE} (by
default) meaning that the event shouldn't be propagated at all or to 
{\tt wxEVENT\_PROPAGATE\_MAX} (for command events) meaning that it should be
propagated as much as necessary.

Any positive number means that the event should be propagated but no more than
the given number of times. E.g. the propagation level may be set to $1$ to
propagate the event to its parent only, but not to its grandparent.


\membersection{wxEvent::Clone}\label{wxeventclone}

\constfunc{virtual wxEvent*}{Clone}{\void}

Returns a copy of the event.

Any event that is posted to the wxWidgets event system for later action (via
\helpref{wxEvtHandler::AddPendingEvent}{wxevthandleraddpendingevent} or
\helpref{wxPostEvent}{wxpostevent}) must implement this method. All wxWidgets
events fully implement this method, but any derived events implemented by the
user should also implement this method just in case they (or some event
derived from them) are ever posted.

All wxWidgets events implement a copy constructor, so the easiest way of
implementing the Clone function is to implement a copy constructor for
a new event (call it MyEvent) and then define the Clone function like this:

\begin{verbatim}
    wxEvent *Clone(void) const { return new MyEvent(*this); }
\end{verbatim}


\membersection{wxEvent::GetEventObject}\label{wxeventgeteventobject}

\func{wxObject*}{GetEventObject}{\void}

Returns the object (usually a window) associated with the
event, if any.


\membersection{wxEvent::GetEventType}\label{wxeventgeteventtype}

\func{wxEventType}{GetEventType}{\void}

Returns the identifier of the given event type,
such as \texttt{wxEVT\_COMMAND\_BUTTON\_CLICKED}.


\membersection{wxEvent::GetId}\label{wxeventgetid}

\constfunc{int}{GetId}{\void}

Returns the identifier associated with this event, such as a button command id.


\membersection{wxEvent::GetSkipped}\label{wxeventgetskipped}

\constfunc{bool}{GetSkipped}{\void}

Returns true if the event handler should be skipped, false otherwise.


\membersection{wxEvent::GetTimestamp}\label{wxeventgettimestamp}

\func{long}{GetTimestamp}{\void}

Gets the timestamp for the event. The timestamp is the time in milliseconds
since some fixed moment (\emph{not} necessarily the standard Unix Epoch, so
only differences between the timestamps and not their absolute values usually
make sense).


\membersection{wxEvent::IsCommandEvent}\label{wxeventiscommandevent}

\constfunc{bool}{IsCommandEvent}{\void}

Returns true if the event is or is derived from
\helpref{wxCommandEvent}{wxcommandevent} else it returns false.
Note: Exists only for optimization purposes.


\membersection{wxEvent::ResumePropagation}\label{wxeventresumepropagation}

\func{void}{ResumePropagation}{\param{int }{propagationLevel}}

Sets the propagation level to the given value (for example returned from an
earlier call to \helpref{StopPropagation}{wxeventstoppropagation}).


\membersection{wxEvent::SetEventObject}\label{wxeventseteventobject}

\func{void}{SetEventObject}{\param{wxObject* }{object}}

Sets the originating object.


\membersection{wxEvent::SetEventType}\label{wxeventseteventtype}

\func{void}{SetEventType}{\param{wxEventType }{type}}

Sets the event type.


\membersection{wxEvent::SetId}\label{wxeventsetid}

\func{void}{SetId}{\param{int}{ id}}

Sets the identifier associated with this event, such as a button command id.


\membersection{wxEvent::SetTimestamp}\label{wxeventsettimestamp}

\func{void}{SetTimestamp}{\param{long }{timeStamp}}

Sets the timestamp for the event.


\membersection{wxEvent::ShouldPropagate}\label{wxeventshouldpropagate}

\constfunc{bool}{ShouldPropagate}{\void}

Test if this event should be propagated or not, i.e. if the propagation level
is currently greater than $0$.


\membersection{wxEvent::Skip}\label{wxeventskip}

\func{void}{Skip}{\param{bool}{ skip = true}}

This method can be used inside an event handler to control whether further
event handlers bound to this event will be called after the current one
returns. Without Skip() (or equivalently if Skip(false) is used),
the event will not be processed any more. If Skip(true) is called, the event
processing system continues searching for a further handler function for this
event, even though it has been processed already in the current handler.

In general, it is recommended to skip all non-command events to allow the
default handling to take place. The command events are, however, normally not
skipped as usually a single command such as a button click or menu item
selection must only be processed by one handler.


\membersection{wxEvent::StopPropagation}\label{wxeventstoppropagation}

\func{int}{StopPropagation}{\void}

Stop the event from propagating to its parent window.

Returns the old propagation level value which may be later passed to 
\helpref{ResumePropagation}{wxeventresumepropagation} to allow propagating the
event again.