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<H3> 5.2.2 Event Handling </H3>
<!--docid::SEC173::-->
<P>
To make the testing somewhat easier we will add a way to terminate the
application by responding to the <KBD>ESC</KBD> key. Add the following private
methods to our class in `<TT>simple.h</TT>':
</P><P>
<TABLE><tr><td> </td><td class=example><pre> static bool SimpleEventHandler (iEvent& ev);
bool HandleEvent (iEvent& ev);
</pre></td></tr></table></P><P>
The static function <CODE>SimpleEventHandler()</CODE> will be registered to
the event queue. It has to be a static function because the event queue
expects to call a normal C-style function (alternatively you could also
implement this by making a subclass of <CODE>iEventHandler</CODE> but this is
more complicated and not really required).
</P><P>
<CODE>HandleEvent()</CODE> is the real event handler. <CODE>SimpleEventHandler()</CODE>
only serves as a stub function to call <CODE>HandleEvent()</CODE>.
</P><P>
Then add the following code before <CODE>Simple::Initialize()</CODE>:
</P><P>
<TABLE><tr><td> </td><td class=example><pre>bool Simple::HandleEvent (iEvent& ev)
{
if (ev.Type == csevKeyDown && ev.Key.Code == CSKEY_ESC)
{
iEventQueue* q = CS_QUERY_REGISTRY (object_reg, iEventQueue);
if (q)
{
q->GetEventOutlet()->Broadcast (cscmdQuit);
q->DecRef ();
}
return true;
}
return false;
}
bool Simple::SimpleEventHandler (iEvent& ev)
{
return simple->HandleEvent (ev);
}
</pre></td></tr></table></P><P>
<CODE>HandleEvent()</CODE> checks if the <KBD>ESC</KBD> key has been pressed. If so it
will use the object registry to find the global event queue object. Using
<CODE>Broadcast</CODE> it will then broadcast the <CODE>cscmdQuit</CODE> message
to all interested parties. This will cause the application to quit by ending
the default run loop.
</P><P>
We also need to initialize this event handler function. To do that add
the following after the call to <CODE>csInitializer::RequestPlugins()</CODE>:
</P><P>
<TABLE><tr><td> </td><td class=example><pre> if (!csInitializer::SetupEventHandler(
object_reg, SimpleEventHandler))
{
csReport (object_reg, CS_REPORTER_SEVERITY_ERROR,
"crystalspace.application.simple",
"Can't initialize event handler!");
return false;
}
</pre></td></tr></table></P><P>
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