specified as <parameter>callback</parameter> will be invoked
immediately before the event loop goes to sleep to wait for
incoming events. It is invoked with the user data pointer passed
- when the event source was created. The callback function may be
- used to reconfigure the precise events to wait for. If the
- <parameter>callback</parameter> parameter is passed as NULL the
- callback function is reset. </para>
+ when the event source was created. The event source will be disabled
+ if the callback function returns a negative error code. The callback
+ function may be used to reconfigure the precise events to wait for.
+ If the <parameter>callback</parameter> parameter is passed as NULL
+ the callback function is reset. </para>
<para>Event source objects have no preparation callback associated
when they are first created with calls such as