From a86bc260e7eb2cac6ee160fd8cbae3b411c34a69 Mon Sep 17 00:00:00 2001
From: Alessandro Ranellucci <aar@cpan.org>
Date: Sat, 24 Dec 2011 11:01:28 +0100
Subject: [PATCH] Bugfix: some islands having ho holes and contained in holes
 themselves were ignored

---
 MANIFEST                       |  1 +
 lib/Slic3r/ExPolygon.pm        |  7 +++++++
 lib/Slic3r/Geometry/Clipper.pm | 14 ++++++++++++-
 lib/Slic3r/Layer.pm            | 37 ++++++++++++++++++++++++----------
 4 files changed, 47 insertions(+), 12 deletions(-)

diff --git a/MANIFEST b/MANIFEST
index b80c4a829..40cfc3f6c 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -49,3 +49,4 @@ t/collinear.t
 t/geometry.t
 t/polyclip.t
 t/stl.t
+utils/post-processing/z-every-line.pl
diff --git a/lib/Slic3r/ExPolygon.pm b/lib/Slic3r/ExPolygon.pm
index 6fc391a41..eddeac8e3 100644
--- a/lib/Slic3r/ExPolygon.pm
+++ b/lib/Slic3r/ExPolygon.pm
@@ -140,4 +140,11 @@ sub rotate {
     $_->rotate(@_) for @$self;
 }
 
+sub area {
+    my $self = shift;
+    my $area = $self->contour->area;
+    $area -= $_->area for $self->holes;
+    return $area;
+}
+
 1;
diff --git a/lib/Slic3r/Geometry/Clipper.pm b/lib/Slic3r/Geometry/Clipper.pm
index 05e7b6c10..f22466b65 100644
--- a/lib/Slic3r/Geometry/Clipper.pm
+++ b/lib/Slic3r/Geometry/Clipper.pm
@@ -5,7 +5,7 @@ use warnings;
 require Exporter;
 our @ISA = qw(Exporter);
 our @EXPORT_OK = qw(explode_expolygon explode_expolygons safety_offset offset
-    diff_ex diff union_ex intersection_ex PFT_EVENODD JT_MITER JT_ROUND
+    diff_ex diff union_ex intersection_ex xor_ex PFT_EVENODD JT_MITER JT_ROUND
     is_counter_clockwise);
 
 use Math::Clipper 1.02 ':all';
@@ -66,4 +66,16 @@ sub intersection_ex {
     ];
 }
 
+sub xor_ex {
+    my ($subject, $clip, $jointype) = @_;
+    $jointype = PFT_NONZERO unless defined $jointype;
+    $clipper->clear;
+    $clipper->add_subject_polygons($subject);
+    $clipper->add_clip_polygons($clip);
+    return [
+        map Slic3r::ExPolygon->new($_),
+            @{ $clipper->ex_execute(CT_XOR, $jointype, $jointype) },
+    ];
+}
+
 1;
diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 8941261af..eab34e029 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -3,7 +3,7 @@ use Moo;
 
 use Math::Clipper ':all';
 use Slic3r::Geometry qw(scale collinear X Y A B PI rad2deg_dir bounding_box_center);
-use Slic3r::Geometry::Clipper qw(union_ex diff_ex intersection_ex is_counter_clockwise);
+use Slic3r::Geometry::Clipper qw(union_ex diff_ex intersection_ex xor_ex is_counter_clockwise);
 use XXX;
 
 # a sequential number of layer, starting at 0
@@ -112,20 +112,35 @@ sub make_surfaces {
         # we need to ignore such holes, but Clipper will convert them to contours.
         # so we identify them and remove them manually.
         
+        my $area_sum = sub {
+            my $area = 0;
+            $area += $_->area for @_;
+            return $area;
+        };
+        
         # get expolygons without holes (candidate for reverse holes detection)
         my @expolygons_without_holes = grep { @$_ == 1 } @$expolygons;
         
-        # remove all holes from such expolygons
-        my $diff = diff_ex(
-            [ map @$_, @expolygons_without_holes ],
-            [ map [ reverse @$_ ], grep !is_counter_clockwise($_), @$loops ],
-        );
+        # prepare holes as contours to allow for safe xor'ing
+        my @reversed_holes = map [ reverse @$_ ], grep !is_counter_clockwise($_), @$loops;
         
-        # merge resulting holes (true holes) and other expolygons
-        $expolygons = [
-            (grep { @$_ > 1 } @$expolygons),
-            @$diff,
-        ];
+        # compare each expolygon without holes with each original hole; if their XOR
+        # is empty then they're the same and we can remove the hole from our layer
+        my %bogus_holes = ();
+        foreach my $contour (map $_->contour, @expolygons_without_holes) {
+            foreach my $hole (grep !exists $bogus_holes{$_}, @reversed_holes) {
+                my $xor = xor_ex([$contour], [$hole]);
+                if (!@$xor || $area_sum->(@$xor) < scale 1) {  # TODO: define this threshold better
+                    $bogus_holes{$hole} = $hole;
+                }
+            }
+        }
+        
+        # remove identified holes
+        $expolygons = diff_ex(
+            [ map @$_, @$expolygons ],
+            [ values %bogus_holes ],
+        ) if %bogus_holes;
         
         Slic3r::debugf "  %d surface(s) having %d holes detected from %d polylines\n",
             scalar(@$expolygons), scalar(map $_->holes, @$expolygons), scalar(@$loops);