New option to disable retraction on layer change

README.markdown

@@ -232,6 +232,8 @@ The author of the Silk icon set is Mark James.
         --retract-before-travel
                             Only retract before travel moves of this length in mm (default: 2)
         --retract-lift      Lift Z by the given distance in mm when retracting (default: 0)
+        --retract-layer-change
+                            Enforce a retraction before each Z move (default: yes)
         
        Retraction options for multi-extruder setups:
         --retract-length-toolchange

lib/Slic3r/Config.pm

@@ -745,6 +745,15 @@ END
         deserialize => $deserialize_comma,
         default => [0],
     },
+    'retract_layer_change' => {
+        label   => 'Retract on layer change',
+        tooltip => 'This flag enforces a retraction whenever a Z move is done.',
+        cli     => 'retract-layer-change!',
+        type    => 'bool',
+        serialize   => $serialize_comma,
+        deserialize => $deserialize_comma,
+        default => [1],
+    },
     'retract_length_toolchange' => {
         label   => 'Length',
         tooltip => 'When retraction is triggered before changing tool, filament is pulled back by the specified amount (the length is measured on raw filament, before it enters the extruder).',
@@ -1012,7 +1021,7 @@ sub new_from_cli {
     }
     
     $args{$_} = $Options->{$_}{deserialize}->($args{$_})
-        for grep exists $args{$_}, qw(print_center bed_size duplicate_grid extruder_offset);
+        for grep exists $args{$_}, qw(print_center bed_size duplicate_grid extruder_offset retract_layer_change);
     
     return $class->new(%args);
 }

lib/Slic3r/Extruder.pm

@@ -7,7 +7,7 @@ use constant OPTIONS => [qw(
     extruder_offset
     nozzle_diameter filament_diameter extrusion_multiplier temperature first_layer_temperature
     retract_length retract_lift retract_speed retract_restart_extra retract_before_travel
-    retract_length_toolchange retract_restart_extra_toolchange
+    retract_layer_change retract_length_toolchange retract_restart_extra_toolchange
 )];
 
 has 'id'    => (is => 'rw', required => 1);

lib/Slic3r/GCode.pm

@@ -103,7 +103,7 @@ sub move_z {
     my $gcode = "";
     my $current_z = $self->z;
     if (!defined $current_z || $current_z != ($z + $self->lifted)) {
-        $gcode .= $self->retract(move_z => $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);

lib/Slic3r/GUI/Tab.pm

@@ -687,7 +687,7 @@ sub build {
 }
 
 sub _extruder_options { qw(nozzle_diameter extruder_offset retract_length retract_lift retract_speed retract_restart_extra retract_before_travel
-    retract_length_toolchange retract_restart_extra_toolchange) }
+    retract_layer_change retract_length_toolchange retract_restart_extra_toolchange) }
 
 sub config {
     my $self = shift;
@@ -720,7 +720,7 @@ sub _build_extruder_pages {
                 title => 'Retraction',
                 options => [
                     map "${_}#${extruder_idx}",
-                        qw(retract_length retract_lift retract_speed retract_restart_extra retract_before_travel)
+                        qw(retract_length retract_lift retract_speed retract_restart_extra retract_before_travel retract_layer_change)
                 ],
             },
             {

slic3r.pl

@@ -285,6 +285,8 @@ $j
     --retract-before-travel
                         Only retract before travel moves of this length in mm (default: $config->{retract_before_travel}[0])
     --retract-lift      Lift Z by the given distance in mm when retracting (default: $config->{retract_lift}[0])
+    --retract-layer-change
+                        Enforce a retraction before each Z move (default: yes)
     
    Retraction options for multi-extruder setups:
     --retract-length-toolchange