Bugfix: lift was not working correctly with multiple extruders and multiple skirt layers. Also, we now ignore all lift settings except the one of the first extruder. Includes regression tests. #1332 #1338

lib/Slic3r/Config.pm

@@ -814,7 +814,7 @@ END
     },
     'retract_lift' => {
         label   => 'Lift Z',
-        tooltip => 'If you set this to a positive value, Z is quickly raised every time a retraction is triggered.',
+        tooltip => 'If you set this to a positive value, Z is quickly raised every time a retraction is triggered. When using multiple extruders, only the setting for the first extruder will be considered.',
         sidetext => 'mm',
         cli     => 'retract-lift=f@',
         type    => 'f',

lib/Slic3r/GCode.pm

@@ -3,7 +3,7 @@ use Moo;
 
 use List::Util qw(min max first);
 use Slic3r::ExtrusionPath ':roles';
-use Slic3r::Geometry qw(scale unscale scaled_epsilon points_coincide PI X Y B);
+use Slic3r::Geometry qw(epsilon scale unscale scaled_epsilon points_coincide PI X Y B);
 use Slic3r::Geometry::Clipper qw(union_ex);
 use Slic3r::Surface ':types';
 
@@ -128,12 +128,23 @@ sub move_z {
     
     my $gcode = "";
     my $current_z = $self->z;
-    if (!defined $current_z || $current_z != ($z + $self->lifted)) {
+    if (!defined $self->z || $z > $self->z) {
+        # if we're going over the current Z we won't be lifted anymore
+        $self->lifted(0);
+        
+        # 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 (' . $self->layer->id . ')'))
-            unless ($current_z // -1) != ($self->z // -1);
+            unless !defined $current_z || $self->z != $current_z;
         $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
+        # (nominal = actual - lifted) and less than the actual one.  we're basically
+        # advancing to next layer, whose nominal Z is still lower than the previous
+        # layer Z with lift.
+        $self->lifted($self->z - $z);
     }
     
     return $gcode;

lib/Slic3r/Print.pm

@@ -73,6 +73,9 @@ sub _trigger_config {
         $self->config->set('support_material_enforce_layers', 0);
         $self->config->set('retract_layer_change', [0]);  # TODO: only apply this to the spiral layers
     }
+    
+    # force all retraction lift values to be the same
+    $self->config->set('retract_lift', [ map $self->config->retract_lift->[0], @{$self->config->retract_lift} ]);
 }
 
 sub _build_has_support_material {

t/retraction.t

@@ -48,8 +48,9 @@ my $test = sub {
             }
             if ($info->{dist_Z} < 0) {
                 fail 'going down only after lifting' if !$lifted;
-                fail 'going down by the same amount of the lift'
+                fail 'going down by the same amount of the lift or by the amount needed to get to next layer'
-                    if !_eq($info->{dist_Z}, -$print->extruders->[$tool]->retract_lift);
+                    if !_eq($info->{dist_Z}, -$print->extruders->[$tool]->retract_lift)
+                        && !_eq($info->{dist_Z}, -$print->extruders->[$tool]->retract_lift + $conf->layer_height);
                 $lifted = 0;
             }
             fail 'move Z at travel speed' if ($args->{F} // $self->F) != $conf->travel_speed * 60;
@@ -123,6 +124,8 @@ $retract_tests->(' (G0 and duplicate)');
 $config->set('duplicate', 1);
 $config->set('g0', 0);
 $config->set('infill_extruder', 2);
-$retract_tests->(' (dual extruder)');
+$config->set('skirts', 4);
+$config->set('skirt_height', 3);
+$retract_tests->(' (dual extruder with multiple skirt layers)');
 
 __END__