Fix regression causing wrong number of solid shells when using fill_density = 0 (includes regression test)

MANIFEST

@@ -62,6 +62,7 @@ t/geometry.t
 t/polyclip.t
 t/retraction.t
 t/serialize.t
+t/shells.t
 t/stl.t
 t/vibrationlimit.t
 utils/amf-to-stl.pl

lib/Slic3r/Layer/Region.pm

@@ -397,11 +397,6 @@ sub prepare_fill_surfaces {
         $_->surface_type(S_TYPE_INTERNAL) for grep $_->surface_type == S_TYPE_BOTTOM, @{$self->fill_surfaces};
     }
         
-    # if hollow object is requested, remove internal surfaces
-    if ($Slic3r::Config->fill_density == 0) {
-        @{$self->fill_surfaces} = grep $_->surface_type != S_TYPE_INTERNAL, @{$self->fill_surfaces};
-    }
-        
     # turn too small internal regions into solid regions
     {
         my $min_area = scale scale $Slic3r::Config->solid_infill_below_area; # scaling an area requires two calls!

lib/Slic3r/Print/Object.pm

@@ -410,6 +410,15 @@ sub discover_horizontal_shells {
             
             @{$layerm->fill_surfaces} = grep $_->expolygon->area > $area_threshold, @{$layerm->fill_surfaces};
         }
+        
+        for (my $i = 0; $i < $self->layer_count; $i++) {
+            my $layerm = $self->layers->[$i]->regions->[$region_id];
+            
+            # if hollow object is requested, remove internal surfaces
+            if ($Slic3r::Config->fill_density == 0) {
+                @{$layerm->fill_surfaces} = grep $_->surface_type != S_TYPE_INTERNAL, @{$layerm->fill_surfaces};
+            }
+        }
     }
 }
 

t/shells.t

@@ -0,0 +1,48 @@
+use Test::More tests => 2;
+use strict;
+use warnings;
+
+BEGIN {
+    use FindBin;
+    use lib "$FindBin::Bin/../lib";
+}
+
+use List::Util qw(first);
+use Slic3r;
+use Slic3r::Test;
+
+{
+    my $config = Slic3r::Config->new_from_defaults;
+    $config->set('skirts', 0);
+    $config->set('perimeters', 0);
+    
+    my $test = sub {
+        my ($conf) = @_;
+        $conf ||= $config;
+        
+        my $print = Slic3r::Test::init_print('20mm_cube', config => $config);
+        
+        my %layers_with_shells = ();  # Z => $count
+        Slic3r::Test::GCodeReader->new(gcode => Slic3r::Test::gcode($print))->parse(sub {
+            my ($self, $cmd, $args, $info) = @_;
+            
+            if ($self->Z > 0) {
+                $layers_with_shells{$self->Z} //= 0;
+                $layers_with_shells{$self->Z} = 1 if $info->{extruding} && $info->{dist_XY} > 0;
+            }
+        });
+        my @shells = @layers_with_shells{sort { $a <=> $b } keys %layers_with_shells};
+        fail "wrong number of bottom solid layers"
+            unless !defined(first { !$_ } @shells[0..$config->bottom_solid_layers-1]);
+        fail "wrong number of top solid layers"
+            unless !defined(first { !$_ } @shells[-$config->top_solid_layers..-1]);
+        1;
+    };
+    
+    ok $test->(), "proper number of shells is applied";
+    
+    $config->set('fill_density', 0);
+    ok $test->(), "proper number of shells is applied even when fill density is none";
+}
+
+__END__