From 3c0057380582700ddf975079b682932ae2db6b03 Mon Sep 17 00:00:00 2001
From: Alessandro Ranellucci <aar@cpan.org>
Date: Fri, 6 Jul 2012 19:57:58 +0200
Subject: [PATCH] Reset E and compensate retraction after changing extruder

---
 lib/Slic3r/GCode.pm | 18 +++++++++++++-----
 lib/Slic3r/Print.pm |  3 +--
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index f3afcd985..58d0eed51 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -247,10 +247,7 @@ sub retract {
     
     # reset extrusion distance during retracts
     # this makes sure we leave sufficient precision in the firmware
-    if (!$Slic3r::use_relative_e_distances && $Slic3r::gcode_flavor !~ /^(?:mach3|makerbot)$/) {
-        $gcode .= "G92 " . $Slic3r::extrusion_axis . "0\n" if $Slic3r::extrusion_axis;
-        $self->extrusion_distance(0);
-    }
+    $gcode .= $self->reset_e if $Slic3r::gcode_flavor !~ /^(?:mach3|makerbot)$/;
     
     return $gcode;
 }
@@ -272,6 +269,14 @@ sub unretract {
     return $gcode;
 }
 
+sub reset_e {
+    my $self = shift;
+    
+    $self->extrusion_distance(0);
+    return "G92 %s0%s\n", $Slic3r::extrusion_axis, ($Slic3r::gcode_comments ? ' ; reset extrusion distance' : '')
+        if $Slic3r::extrusion_axis && !$Slic3r::use_relative_e_distances;
+}
+
 sub set_acceleration {
     my $self = shift;
     my ($acceleration) = @_;
@@ -382,7 +387,10 @@ sub set_tool {
     return "" if $self->extruder_idx == $tool;
     
     $self->extruder_idx($tool);
-    return $self->retract . sprintf "T%d%s\n", $tool, ($Slic3r::gcode_comments ? ' ; change tool' : '');
+    return $self->retract
+        . sprintf "T%d%s\n", $tool, ($Slic3r::gcode_comments ? ' ; change tool' : '')
+        . $self->reset_e
+        . $self->unretract;
 }
 
 sub set_fan {
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index a1904cd10..6e9cc558a 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -530,8 +530,7 @@ sub write_gcode {
     print  $fh "G90 ; use absolute coordinates\n";
     print  $fh "G21 ; set units to millimeters\n";
     if ($Slic3r::gcode_flavor =~ /^(?:reprap|teacup)$/) {
-        printf $fh "G92 %s0 ; reset extrusion distance\n", $Slic3r::extrusion_axis
-            if $Slic3r::extrusion_axis && !$Slic3r::use_relative_e_distances;
+        printf $fh $gcodegen->reset_e;
         if ($Slic3r::gcode_flavor =~ /^(?:reprap|makerbot)$/) {
             if ($Slic3r::use_relative_e_distances) {
                 print $fh "M83 ; use relative distances for extrusion\n";