From f001374c6e2a17640b70e5220c2b4fb4537892e2 Mon Sep 17 00:00:00 2001
From: Alessandro Ranellucci <aar@cpan.org>
Date: Wed, 5 Dec 2012 11:31:35 +0100
Subject: [PATCH] New implementation of the little inwards move before leaving
 a loop. #186

---
 lib/Slic3r/GCode.pm    | 24 ++++++++++++++++++++++--
 lib/Slic3r/Geometry.pm |  1 +
 lib/Slic3r/Polygon.pm  | 12 ++++++++++--
 t/angles.t             | 11 +++++++++--
 4 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index 69d2765a..8062b7d6 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -97,7 +97,7 @@ sub extrude_loop {
     
     # extrude all loops ccw
     $loop = $loop->unpack if $loop->isa('Slic3r::ExtrusionLoop::Packed');
-    $loop->polygon->make_counter_clockwise;
+    my $was_clockwise = $loop->polygon->make_counter_clockwise;
     
     # find the point of the loop that is closest to the current extruder position
     # or randomize if requested
@@ -118,7 +118,27 @@ sub extrude_loop {
     return '' if !@{$extrusion_path->polyline};
     
     # extrude along the path
-    return $self->extrude_path($extrusion_path, $description);
+    my $gcode = $self->extrude_path($extrusion_path, $description);
+    
+    # make a little move inwards before leaving loop
+    if ($loop->role == EXTR_ROLE_EXTERNAL_PERIMETER) {
+        # detect angle between last and first segment
+        # the side depends on the original winding order of the polygon (left for contours, right for holes)
+        my @points = $was_clockwise ? (-2, 1) : (1, -2);
+        my $angle = Slic3r::Geometry::angle3points(@{$extrusion_path->polyline}[0, @points]) / 3;
+        $angle *= -1 if $was_clockwise;
+        
+        # create the destination point along the first segment and rotate it
+        my $point = Slic3r::Geometry::point_along_segment(@{$extrusion_path->polyline}[0,1], scale $extrusion_path->flow_spacing);
+        bless $point, 'Slic3r::Point';
+        $point->rotate($angle, $extrusion_path->polyline->[0]);
+        
+        # generate the travel move
+        $self->speed('travel');
+        $gcode .= $self->G0($point, undef, 0, "move inwards before travel");
+    }
+    
+    return $gcode;
 }
 
 sub extrude_path {
diff --git a/lib/Slic3r/Geometry.pm b/lib/Slic3r/Geometry.pm
index 9bfb0bce..db3ecb6c 100644
--- a/lib/Slic3r/Geometry.pm
+++ b/lib/Slic3r/Geometry.pm
@@ -736,6 +736,7 @@ sub size_3D {
     return map $extents[$_][MAX] - $extents[$_][MIN], (X,Y,Z);
 }
 
+# this assumes a CCW rotation from $p2 to $p3 around $p1
 sub angle3points {
     my ($p1, $p2, $p3) = @_;
     # p1 is the center
diff --git a/lib/Slic3r/Polygon.pm b/lib/Slic3r/Polygon.pm
index 50805ab4..eaaca1d0 100644
--- a/lib/Slic3r/Polygon.pm
+++ b/lib/Slic3r/Polygon.pm
@@ -31,12 +31,20 @@ sub is_counter_clockwise {
 
 sub make_counter_clockwise {
     my $self = shift;
-    $self->reverse if !$self->is_counter_clockwise;
+    if (!$self->is_counter_clockwise) {
+        $self->reverse;
+        return 1;
+    }
+    return 0;
 }
 
 sub make_clockwise {
     my $self = shift;
-    $self->reverse if $self->is_counter_clockwise;
+    if ($self->is_counter_clockwise) {
+        $self->reverse;
+        return 1;
+    }
+    return 0;
 }
 
 sub merge_continuous_lines {
diff --git a/t/angles.t b/t/angles.t
index 0caac718..dc1a671b 100644
--- a/t/angles.t
+++ b/t/angles.t
@@ -2,7 +2,7 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 24;
+plan tests => 26;
 
 BEGIN {
     use FindBin;
@@ -10,7 +10,7 @@ BEGIN {
 }
 
 use Slic3r;
-use Slic3r::Geometry qw(line_atan line_direction rad2deg_dir PI);
+use Slic3r::Geometry qw(line_atan line_direction rad2deg_dir angle3points PI);
 
 #==========================================================
 
@@ -54,3 +54,10 @@ use Slic3r::Geometry qw(line_atan line_direction rad2deg_dir PI);
 }
 
 #==========================================================
+
+{
+    is angle3points([0,0], [10,0], [0,10]), PI/2, 'CW angle3points';
+    is angle3points([0,0], [0,10], [10,0]), PI/2*3, 'CCW angle3points';
+}
+
+#==========================================================