Wx::Thread(3pm)

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.

perl v5.10.1 2007-04-28 Wx::Thread(3pm)