Fix retraction/Z/lift problems after recent changes

lib/Slic3r/GCode.pm

@@ -134,10 +134,9 @@ sub move_z {
         
         # this retraction may alter $self->z
         $gcode .= $self->retract(move_z => $z) if $self->extruder->retract_layer_change;
-        
         $self->speed('travel');
         $gcode .= $self->G0(undef, $z, 0, $comment || ('move to next layer (' . $self->layer->id . ')'))
-            unless !defined $current_z || $self->z != $current_z;
+            if !defined $self->z || abs($z - ($self->z - $self->lifted)) > epsilon;
         $gcode .= $self->move_z_callback->() if defined $self->move_z_callback;
     } elsif ($z < $self->z && $z > ($self->z - $self->lifted + epsilon)) {
         # we're moving to a layer height which is greater than the nominal current one
@@ -525,6 +524,7 @@ sub unretract {
     
     if ($self->lifted) {
         $self->speed('travel');
+        $gcode .= sprintf ";AAA selfz = %s, lifted = %s\n", $self->z // 'nd', $self->lifted // 'nd';
         $gcode .= $self->G0(undef, $self->z - $self->lifted, 0, 'restore layer Z');
         $self->lifted(0);
     }

t/layers.t

@@ -1,4 +1,4 @@
-use Test::More tests => 5;
+use Test::More tests => 4;
 use strict;
 use warnings;
 
@@ -56,15 +56,4 @@ ok $test->(), "positive Z offset";
 $config->set('z_offset', -0.8);
 ok $test->(), "negative Z offset";
 
-{
-    my $config = Slic3r::Config->new_from_defaults;
-    $config->set('nozzle_diameter', [0.35]);
-    $config->set('layer_height', 0.1333);
-    
-    my $print = Slic3r::Test::init_print('2x20x10', config => $config);
-    $print->init_extruders;
-    $_->region(0) for @{$print->objects->[0]->layers};  # init layer regions
-    ok $print->objects->[0]->layers->[1]->support_material_contact_height > 0, 'support_material_contact_height is positive';
-}
-
 __END__