Fixed regression causing retraction to be skipped when Retract Length was 0 but Use Firmware Retraction was enabled. Includes regression test. #2359

lib/Slic3r/GCode.pm

@@ -393,7 +393,7 @@ sub retract {
     
     $gcode .= $self->writer->reset_e;
     $gcode .= $self->writer->lift
-        if $self->writer->extruder->retract_length > 0;
+        if $self->writer->extruder->retract_length > 0 || $self->config->use_firmware_retraction;
     
     return $gcode;
 }

t/retraction.t

@@ -1,4 +1,4 @@
-use Test::More tests => 18;
+use Test::More tests => 19;
 use strict;
 use warnings;
 
@@ -182,6 +182,24 @@ use Slic3r::Test qw(_eq);
     is $double_unretractions, 0, 'no double unretractions';
 }
 
+{
+    my $config = Slic3r::Config->new_from_defaults;
+    $config->set('use_firmware_retraction', 1);
+    $config->set('retract_length', [0]);
+    
+    my $print = Slic3r::Test::init_print('20mm_cube', config => $config);
+    my $retracted = 0;
+    Slic3r::GCode::Reader->new->parse(Slic3r::Test::gcode($print), sub {
+        my ($self, $cmd, $args, $info) = @_;
+        
+        if ($cmd eq 'G10') {
+            $retracted = 1;
+        }
+    });
+    
+    ok $retracted, 'retracting also when --retract-length is 0 but --use-firmware-retraction is enabled';
+}
+
 {
     my $config = Slic3r::Config->new_from_defaults;
     $config->set('only_retract_when_crossing_perimeters', 1);

xs/src/libslic3r/GCodeWriter.cpp

@@ -417,6 +417,12 @@ std::string
 GCodeWriter::_retract(double length, double restart_extra, const std::string &comment)
 {
     std::ostringstream gcode;
+    
+    /*  If firmware retraction is enabled, we use a fake value of 1
+        since we ignore the actual configured retract_length which 
+        might be 0, in which case the retraction logic gets skipped. */
+    if (this->config.use_firmware_retraction) length = 1;
+    
     double dE = this->_extruder->retract(length, restart_extra);
     if (dE != 0) {
         if (this->config.use_firmware_retraction) {