weaken extra refs to ::Viewport objects so undefining causes destroy

Author: mohawk2

lib/PDL/Graphics/TriD/ButtonControl.pm

@@ -37,6 +37,7 @@ the Event loop.
 package PDL::Graphics::TriD::ButtonControl;
 use strict;
 use warnings;
+use Scalar::Util qw(weaken);
 use fields qw/Win W H SC/;
 
 $PDL::Graphics::TriD::verbose //= 0;
@@ -45,7 +46,7 @@ sub new {
   my ($class,$win) = @_;
 
   my $self = fields::new($class);
-  $self->{Win} = $win;
+  weaken($self->{Win} = $win);
 
   $self;
 }

lib/PDL/Graphics/TriD/Window.pm

@@ -181,14 +181,16 @@ sub set_material {
 package # hide from PAUSE
   PDL::Graphics::TriD::EventHandler;
 use fields qw/X Y Buttons VP/;
+use Scalar::Util qw(weaken);
+
 sub new {
   my $class = shift;
   my $vp = shift;
   my $self = fields::new($class);
   $self->{X} = -1;
   $self->{Y} = -1;
   $self->{Buttons} = [];
-  $self->{VP} = $vp;
+  weaken($self->{VP} = $vp);
   $self;
 }
 sub event {