NAME

       Thread - using wxPerl with threads

SYNOPSIS

         # the order of these use()s is important
         use threads;
         use threads::shared;
         use Wx;

         my $DONE_EVENT : shared = Wx::NewEventType;

         my $worker = threads->create( \&work );

         # create frames, etc
         my $frame = Wx::Frame->new( ... );
         EVT_COMMAND( $frame, -1, $DONE_EVENT, \&done );
         $app->MainLoop;

         sub done {
             my( $frame, $event ) = @_;

             print $event->GetData;
         }

         sub work {
             # ... do stuff, create a shared $result value

             my $threvent = new Wx::PlThreadEvent( -1, $DONE_EVENT, $result );
             Wx::PostEvent( $frame, $threvent );
         }

         # event handler
         sub OnCreateThread {
             # @_ = () is necessary to avoid "Scalars leaked"
             my( $self, $event ) = @_; @_ = ();

             threads->create( ... );
         }

DESCRIPTION

       Threaded GUI application are somewhat different from non-GUI threaded applications in that
       the main thread (which runs the GUI) must never block.  Also, in wxWidgets, no thread
       other than the main thread can manipulate GUI objects.  This leads to a hybrid model where
       worker threads must send events to the main thread in order to change the GUI state or
       signal their termination.

   Order of module loading
       It's necessary for "use Wx" to happen after <use threads::shared>.

   Sending events from worker threads
       "Wx::PlThreadEvent" can be used to communicate between worker and GUI threads.  The event
       can carry a shared value between threads.

         my $DONE_EVENT : shared = Wx::NewEventType;

         sub work {
             # ... do some stuff
             my $progress = new Wx::PlThreadEvent( -1, $DONE_EVENT, $progress );
             Wx::PostEvent( $frame, $progress );

             # ... do stuff, create a shared $result value
             my $end = new Wx::PlThreadEvent( -1, $DONE_EVENT, $result );
             Wx::PostEvent( $frame, $end );
         }

       The target of the event can be any "Wx::EvtHandler"

   Receiving events from worker threads
       "Wx::PlThreadEvent" is a command event and can be handled as such.  The "->GetData" method
       can be used to retrieve the shared data contained inside the event.

         my $DONE_EVENT : shared = Wx::NewEventType;

         EVT_COMMAND( $frame, -1, $DONE_EVENT, \&done );

         sub done {
             my( $frame, $event ) = @_;

             print $event->GetData;
         }

   Creating new threads
       Creating new threads from event handlers works without problems except from a little snag.
       In order not to trigger a bug in the Perl interpreter, all event handler that directly or
       indirectly cause a thread creation must clean @_ before starting the thread.

       For example:

         sub OnCreateThread {
             my( $self, $event ) = @_; @_ = ();

             threads->create( ... );
         }

       failure to do that will cause "scalars leaked" warnings from the Perl interpreter.