| Wx::Thread(3pm) | User Contributed Perl Documentation | Wx::Thread(3pm) |
Thread - using wxPerl with threads
# 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( ... );
}
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.
It's necessary for "use Wx" to happen after <use threads::shared>.
"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"
"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 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.
| 2023-02-14 | perl v5.36.0 |