From 81bae56e928a075642d598059d9ab326804ef9b8 Mon Sep 17 00:00:00 2001
From: Alessandro Ranellucci <aar@cpan.org>
Date: Mon, 3 Jun 2013 12:25:32 +0200
Subject: [PATCH] Limit only_retract_when_crossing_perimeters to travel moves
 that are completely enclosed in the upper layer's slices so that we avoid
 visible traces on top layers. #1091

---
 lib/Slic3r/GCode.pm | 4 ++--
 lib/Slic3r/Layer.pm | 6 ++++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index 4519d933a..da6855210 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -283,7 +283,7 @@ sub travel_to {
     $travel->translate(-$self->shift_x, -$self->shift_y);
     
     if ($travel->length < scale $self->extruder->retract_before_travel
-        || ($self->config->only_retract_when_crossing_perimeters && first { $_->encloses_line($travel, scaled_epsilon) } @{$self->layer->slices})
+        || ($self->config->only_retract_when_crossing_perimeters && first { $_->encloses_line($travel, scaled_epsilon) } @{$self->layer->upper_layer_slices})
         || ($role == EXTR_ROLE_SUPPORTMATERIAL && $self->layer->support_islands_enclose_line($travel))
         ) {
         $self->straight_once(0);
@@ -326,7 +326,7 @@ sub _plan {
     my $need_retract = !$self->config->only_retract_when_crossing_perimeters;
     if (!$need_retract) {
         $need_retract = 1;
-        foreach my $slice (@{$self->layer->slices}) {
+        foreach my $slice (@{$self->layer->upper_layer_slices}) {
             # discard the island if at any line is not enclosed in it
             next if first { !$slice->encloses_line($_, scaled_epsilon) } @travel;
             # okay, this island encloses the full travel path
diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 074baef55..ac6d8d290 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -54,6 +54,12 @@ sub support_material_contact_z {
     return $self->print_z - ($self->height - $self->support_material_contact_height) / &Slic3r::SCALING_FACTOR;
 }
 
+sub upper_layer_slices {
+    my $self = shift;
+    
+    my $upper_layer = $self->object->layers->[ $self->id + 1 ] or return [];
+    return $upper_layer->slices;
+
 sub region {
     my $self = shift;
     my ($region_id) = @_;