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

Author: mohawk2

lib/PDL/Graphics/TriD.pm

@@ -864,9 +864,7 @@ keeptwiddling3d();
 
 *close3d = *close3d = \&PDL::close3d;
 sub PDL::close3d {
-  return if !ref $PDL::Graphics::TriD::current_window;
-  return if !$PDL::Graphics::TriD::current_window->can('close');
-  $PDL::Graphics::TriD::current_window->close;
+  $PDL::Graphics::TriD::current_window = undef;
 }
 
 sub graph_object {

lib/PDL/Graphics/TriD/GL/GLFW.pm

@@ -4,6 +4,7 @@ use strict;
 use warnings;
 use OpenGL::GLFW qw( :all );
 use OpenGL::Modern::Helpers qw(glGetVersion_p);
+use Scalar::Util qw(weaken);
 
 our @ISA = qw(PDL::Graphics::TriD::GL);
 my ($window_seq, @fakeXEvents, %winObjects) = 0;
@@ -39,7 +40,7 @@ sub new {
   if ($PDL::Graphics::TriD::verbose) {
     print "GLFW driver: Got TriD::GL object(GLFW window ID#$self->{window_seq} " . $self->{glfwwindow} . ")\n";
   }
-  $self->{winobjects}{$self->{glfwwindow}} = $window_obj;      # circular ref
+  weaken($self->{winobjects}{$self->{glfwwindow}} = $window_obj);
   $self;
 }
 

lib/PDL/Graphics/TriD/GL/GLUT.pm

@@ -5,6 +5,7 @@ use warnings;
 use OpenGL::GLUT qw( :all );
 use OpenGL::Config;
 use OpenGL::Modern::Helpers qw(glGetVersion_p);
+use Scalar::Util qw(weaken);
 
 our @ISA = qw(PDL::Graphics::TriD::GL);
 my (@fakeXEvents, @winObjects);
@@ -56,7 +57,7 @@ sub _init_glut_window {
   if ($PDL::Graphics::TriD::verbose) {
     print "GLUT driver: Got TriD::GL object(GLUT window ID# " . $self->{glutwindow} . ")\n";
   }
-  $self->{winobjects}->[$self->{glutwindow}] = $window_obj;      # circular ref
+  weaken($self->{winobjects}->[$self->{glutwindow}] = $window_obj);
 }
 
 sub DESTROY {