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.IX Title "Wx::Thread 3pm"
.TH Wx::Thread 3pm "2017-05-20" "perl v5.24.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
Thread \- using wxPerl with threads
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 4
\&  # 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( \e&work );
\&
\&  # create frames, etc
\&  my $frame = Wx::Frame\->new( ... );
\&  EVT_COMMAND( $frame, \-1, $DONE_EVENT, \e&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( ... );
\&  }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Threaded \s-1GUI\s0 application are somewhat different from non-GUI threaded
applications in that the main thread (which runs the \s-1GUI\s0) must never
block.  Also, in wxWidgets, no thread other than the main thread can
manipulate \s-1GUI\s0 objects.  This leads to a hybrid model where worker
threads must send events to the main thread in order to change the \s-1GUI\s0
state or signal their termination.
.SS "Order of module loading"
.IX Subsection "Order of module loading"
It's necessary for \f(CW\*(C`use Wx\*(C'\fR to happen after <use threads::shared>.
.SS "Sending events from worker threads"
.IX Subsection "Sending events from worker threads"
\&\f(CW\*(C`Wx::PlThreadEvent\*(C'\fR can be used to communicate between worker and
\&\s-1GUI\s0 threads.  The event can carry a \fIshared\fR value between threads.
.PP
.Vb 1
\&  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 );
\&  }
.Ve
.PP
The target of the event can be any \f(CW\*(C`Wx::EvtHandler\*(C'\fR
.SS "Receiving events from worker threads"
.IX Subsection "Receiving events from worker threads"
\&\f(CW\*(C`Wx::PlThreadEvent\*(C'\fR is a command event and can be handled as such.
The \f(CW\*(C`\->GetData\*(C'\fR method can be used to retrieve the \fIshared\fR data
contained inside the event.
.PP
.Vb 1
\&  my $DONE_EVENT : shared = Wx::NewEventType;
\&
\&  EVT_COMMAND( $frame, \-1, $DONE_EVENT, \e&done );
\&
\&  sub done {
\&      my( $frame, $event ) = @_;
\&
\&      print $event\->GetData;
\&  }
.Ve
.SS "Creating new threads"
.IX Subsection "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 \f(CW@_\fR before starting the thread.
.PP
For example:
.PP
.Vb 2
\&  sub OnCreateThread {
\&      my( $self, $event ) = @_; @_ = ();
\&
\&      threads\->create( ... );
\&  }
.Ve
.PP
failure to do that will cause \*(L"scalars leaked\*(R" warnings from the Perl
interpreter.