diff --git a/README.md b/README.md
index 984931402..f24fdfc66 100644
--- a/README.md
+++ b/README.md
@@ -280,7 +280,7 @@ The author of the Silk icon set is Mark James.
                             Only retract before travel moves of this length in mm (default: 2)
         --retract-lift      Lift Z by the given distance in mm when retracting (default: 0)
         --retract-layer-change
-                            Enforce a retraction before each Z move (default: yes)
+                            Enforce a retraction before each Z move (default: no)
         --wipe              Wipe the nozzle while doing a retraction (default: no)
     
        Retraction options for multi-extruder setups:
diff --git a/lib/Slic3r.pm b/lib/Slic3r.pm
index 60d7ac4a5..bcb3aac03 100644
--- a/lib/Slic3r.pm
+++ b/lib/Slic3r.pm
@@ -32,8 +32,6 @@ warn "Running Slic3r under Perl 5.16 is not supported nor recommended\n"
 use FindBin;
 our $var = "$FindBin::Bin/var";
 
-use Encode;
-use Encode::Locale;
 use Moo 1.003001;
 
 use Slic3r::XS;   # import all symbols (constants etc.) before they get parsed
@@ -262,13 +260,17 @@ sub resume_all_threads {
 }
 
 sub encode_path {
-    my ($filename) = @_;
-    return encode('locale_fs', $filename);
+    my ($path) = @_;
+    
+    utf8::downgrade($path) if $^O eq 'MSWin32';
+    return $path;
 }
 
 sub decode_path {
-    my ($filename) = @_;
-    return decode('locale_fs', $filename);
+    my ($path) = @_;
+    
+    utf8::upgrade($path) if $^O eq 'MSWin32';
+    return $path;
 }
 
 sub open {
diff --git a/lib/Slic3r/Fill/Concentric.pm b/lib/Slic3r/Fill/Concentric.pm
index 1bc9b79f9..ca1837c4e 100644
--- a/lib/Slic3r/Fill/Concentric.pm
+++ b/lib/Slic3r/Fill/Concentric.pm
@@ -6,6 +6,8 @@ extends 'Slic3r::Fill::Base';
 use Slic3r::Geometry qw(scale unscale X);
 use Slic3r::Geometry::Clipper qw(offset offset2 union_pt_chained);
 
+sub no_sort { 1 }
+
 sub fill_surface {
     my $self = shift;
     my ($surface, %params) = @_;
@@ -36,7 +38,7 @@ sub fill_surface {
     @loops = map Slic3r::Polygon->new(@$_),
         reverse @{union_pt_chained(\@loops)};
     
-    # order paths using a nearest neighbor search
+    # split paths using a nearest neighbor search
     my @paths = ();
     my $last_pos = Slic3r::Point->new(0,0);
     foreach my $loop (@loops) {
diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index 27f5dbe53..5398be0a8 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -21,7 +21,7 @@ has 'avoid_crossing_perimeters' => (is => 'rw', default => sub { Slic3r::GCode::
 has 'enable_loop_clipping' => (is => 'rw', default => sub {1});
 has 'enable_cooling_markers' => (is =>'rw', default => sub {0});
 has 'layer_count'        => (is => 'ro');
-has '_layer_index'       => (is => 'rw', default => sub {-1});  # just a counter
+has 'layer_index'        => (is => 'rw', default => sub {-1});  # just a counter
 has 'layer'              => (is => 'rw');
 has '_seam_position'     => (is => 'ro', default => sub { {} });  # $object => pos
 has 'first_layer'        => (is => 'rw', default => sub {0});   # this flag triggers first layer speeds
@@ -76,7 +76,7 @@ sub change_layer {
     my ($self, $layer) = @_;
     
     $self->layer($layer);
-    $self->_layer_index($self->_layer_index + 1);
+    $self->layer_index($self->layer_index + 1);
     $self->first_layer($layer->id == 0);
     
     # avoid computing islands and overhangs if they're not needed
@@ -88,14 +88,14 @@ sub change_layer {
     
     my $gcode = "";
     if (defined $self->layer_count) {
-        $gcode .= $self->writer->update_progress($self->_layer_index, $self->layer_count);
+        $gcode .= $self->writer->update_progress($self->layer_index, $self->layer_count);
     }
     
     my $z = $layer->print_z + $self->config->z_offset;  # in unscaled coordinates
     if ($self->config->get_at('retract_layer_change', $self->writer->extruder->id) && $self->writer->will_move_z($z)) {
         $gcode .= $self->retract;
     }
-    $gcode .= $self->writer->travel_to_z($z, 'move to next layer (' . $self->layer->id . ')');
+    $gcode .= $self->writer->travel_to_z($z, 'move to next layer (' . $self->layer_index . ')');
     
     # forget last wiping path as wiping after raising Z is pointless
     $self->wipe->path(undef);
diff --git a/lib/Slic3r/GUI.pm b/lib/Slic3r/GUI.pm
index 88dafd467..a7d8fdfe6 100644
--- a/lib/Slic3r/GUI.pm
+++ b/lib/Slic3r/GUI.pm
@@ -81,7 +81,7 @@ sub OnInit {
     $self->{notifier} = Slic3r::GUI::Notifier->new;
     
     # locate or create data directory
-    $datadir ||= Wx::StandardPaths::Get->GetUserDataDir;
+    $datadir ||= Slic3r::decode_path(Wx::StandardPaths::Get->GetUserDataDir);
     my $enc_datadir = Slic3r::encode_path($datadir);
     Slic3r::debugf "Data directory: %s\n", $datadir;
     
@@ -297,7 +297,7 @@ sub open_model {
         $dialog->Destroy;
         return;
     }
-    my @input_files = $dialog->GetPaths;
+    my @input_files = map Slic3r::decode_path($_), $dialog->GetPaths;
     $dialog->Destroy;
     
     return @input_files;
diff --git a/lib/Slic3r/GUI/3DScene.pm b/lib/Slic3r/GUI/3DScene.pm
index 794de1fc1..7628a6c54 100644
--- a/lib/Slic3r/GUI/3DScene.pm
+++ b/lib/Slic3r/GUI/3DScene.pm
@@ -593,7 +593,7 @@ sub Resize {
         -$x/2, $x/2, -$y/2, $y/2,
         -$depth, 2*$depth,
     );
- 
+    
     glMatrixMode(GL_MODELVIEW);
 }
  
@@ -937,7 +937,7 @@ package Slic3r::GUI::3DScene;
 use base qw(Slic3r::GUI::3DScene::Base);
 
 use OpenGL qw(:glconstants :gluconstants :glufunctions);
-use List::Util qw(first);
+use List::Util qw(first min max);
 use Slic3r::Geometry qw(scale unscale epsilon);
 use Slic3r::Print::State ':steps';
 
@@ -1079,6 +1079,59 @@ sub load_print_object_slices {
     );
 }
 
+sub load_print_toolpaths {
+    my ($self, $print) = @_;
+    
+    return if !$print->step_done(STEP_SKIRT);
+    return if !$print->step_done(STEP_BRIM);
+    return if !$print->has_skirt && $print->config->brim_width == 0;
+    
+    my $qverts  = Slic3r::GUI::_3DScene::GLVertexArray->new;
+    my $tverts  = Slic3r::GUI::_3DScene::GLVertexArray->new;
+    my %offsets = ();  # print_z => [ qverts, tverts ]
+    
+    my $skirt_height = 0;  # number of layers
+    if ($print->has_infinite_skirt) {
+        $skirt_height = $print->total_layer_count;
+    } else {
+        $skirt_height = min($print->config->skirt_height, $print->total_layer_count);
+    }
+    $skirt_height ||= 1 if $print->config->brim_width > 0;
+    
+    # get first $skirt_height layers (maybe this should be moved to a PrintObject method?)
+    my $object0 = $print->get_object(0);
+    my @layers = ();
+    push @layers, map $object0->get_layer($_-1), 1..min($skirt_height, $object0->layer_count);
+    push @layers, map $object0->get_support_layer($_-1), 1..min($skirt_height, $object0->support_layer_count);
+    @layers = sort { $a->print_z <=> $b->print_z } @layers;
+    @layers = @layers[0..($skirt_height-1)];
+    
+    foreach my $i (0..($skirt_height-1)) {
+        my $top_z = $layers[$i]->print_z;
+        $offsets{$top_z} = [$qverts->size, $tverts->size];
+        
+        if ($i == 0) {
+            $self->_extrusionentity_to_verts($print->brim, $top_z, Slic3r::Point->new(0,0), $qverts, $tverts);
+        }
+        
+        $self->_extrusionentity_to_verts($print->skirt, $top_z, Slic3r::Point->new(0,0), $qverts, $tverts);
+    }
+    
+    my $bb = Slic3r::Geometry::BoundingBoxf3->new;
+    {
+        my $pbb = $print->bounding_box;
+        $bb->merge_point(Slic3r::Pointf3->new_unscale(@{$pbb->min_point}));
+        $bb->merge_point(Slic3r::Pointf3->new_unscale(@{$pbb->max_point}));
+    }
+    push @{$self->volumes}, Slic3r::GUI::3DScene::Volume->new(
+        bounding_box    => $bb,
+        color           => COLORS->[2],
+        qverts          => $qverts,
+        tverts          => $tverts,
+        offsets         => { %offsets },
+    );
+}
+
 sub load_print_object_toolpaths {
     my ($self, $object) = @_;
     
diff --git a/lib/Slic3r/GUI/AboutDialog.pm b/lib/Slic3r/GUI/AboutDialog.pm
index b64bbea40..815da9e15 100644
--- a/lib/Slic3r/GUI/AboutDialog.pm
+++ b/lib/Slic3r/GUI/AboutDialog.pm
@@ -3,7 +3,7 @@ use strict;
 use warnings;
 use utf8;
 
-use Wx qw(:font :html :misc :sizer :systemsettings);
+use Wx qw(:font :html :misc :dialog :sizer :systemsettings);
 use Wx::Event qw(EVT_HTML_LINK_CLICKED);
 use Wx::Print;
 use Wx::Html;
@@ -12,7 +12,7 @@ use base 'Wx::Dialog';
 sub new {
     my $class = shift;
     my ($parent) = @_;
-    my $self = $class->SUPER::new($parent, -1, 'About Slic3r', wxDefaultPosition, [600, 300]);
+    my $self = $class->SUPER::new($parent, -1, 'About Slic3r', wxDefaultPosition, [600, 300], &Wx::wxCLOSE_BOX);
 
     $self->SetBackgroundColour(Wx::wxWHITE);
     my $hsizer = Wx::BoxSizer->new(wxHORIZONTAL);
diff --git a/lib/Slic3r/GUI/BedShapeDialog.pm b/lib/Slic3r/GUI/BedShapeDialog.pm
index 7b5c3ca92..fa6429023 100644
--- a/lib/Slic3r/GUI/BedShapeDialog.pm
+++ b/lib/Slic3r/GUI/BedShapeDialog.pm
@@ -386,7 +386,7 @@ sub _load_stl {
         $dialog->Destroy;
         return;
     }
-    my $input_file = $dialog->GetPaths;
+    my $input_file = Slic3r::decode_path($dialog->GetPaths);
     $dialog->Destroy;
     
     my $model = Slic3r::Model->read_from_file($input_file);
diff --git a/lib/Slic3r/GUI/MainFrame.pm b/lib/Slic3r/GUI/MainFrame.pm
index 9882888c0..ab63510f6 100644
--- a/lib/Slic3r/GUI/MainFrame.pm
+++ b/lib/Slic3r/GUI/MainFrame.pm
@@ -141,8 +141,8 @@ sub _init_tabpanel {
     
     if ($self->{plater}) {
         $self->{plater}->on_select_preset(sub {
-            my ($group, $preset) = @_;
-	        $self->{options_tabs}{$group}->select_preset($preset);
+            my ($group, $i) = @_;
+	        $self->{options_tabs}{$group}->select_preset($i);
         });
         
         # load initial config
@@ -158,38 +158,44 @@ sub _init_menubar {
     {
         $self->_append_menu_item($fileMenu, "&Load Config…\tCtrl+L", 'Load exported configuration file', sub {
             $self->load_config_file;
-        });
+        }, undef, 'plugin_add.png');
         $self->_append_menu_item($fileMenu, "&Export Config…\tCtrl+E", 'Export current configuration to file', sub {
             $self->export_config;
-        });
+        }, undef, 'plugin_go.png');
         $self->_append_menu_item($fileMenu, "&Load Config Bundle…", 'Load presets from a bundle', sub {
             $self->load_configbundle;
-        });
+        }, undef, 'lorry_add.png');
         $self->_append_menu_item($fileMenu, "&Export Config Bundle…", 'Export all presets to file', sub {
             $self->export_configbundle;
-        });
+        }, undef, 'lorry_go.png');
         $fileMenu->AppendSeparator();
         my $repeat;
         $self->_append_menu_item($fileMenu, "Q&uick Slice…\tCtrl+U", 'Slice file', sub {
-            $self->quick_slice;
-            $repeat->Enable(defined $Slic3r::GUI::MainFrame::last_input_file);
-        });
+            wxTheApp->CallAfter(sub {
+                $self->quick_slice;
+                $repeat->Enable(defined $Slic3r::GUI::MainFrame::last_input_file);
+            });
+        }, undef, 'cog_go.png');
         $self->_append_menu_item($fileMenu, "Quick Slice and Save &As…\tCtrl+Alt+U", 'Slice file and save as', sub {
-            $self->quick_slice(save_as => 1);
-            $repeat->Enable(defined $Slic3r::GUI::MainFrame::last_input_file);
-        });
+            wxTheApp->CallAfter(sub {
+                $self->quick_slice(save_as => 1);
+                $repeat->Enable(defined $Slic3r::GUI::MainFrame::last_input_file);
+            });
+        }, undef, 'cog_go.png');
         $repeat = $self->_append_menu_item($fileMenu, "&Repeat Last Quick Slice\tCtrl+Shift+U", 'Repeat last quick slice', sub {
-            $self->quick_slice(reslice => 1);
-        });
+            wxTheApp->CallAfter(sub {
+                $self->quick_slice(reslice => 1);
+            });
+        }, undef, 'cog_go.png');
         $repeat->Enable(0);
         $fileMenu->AppendSeparator();
         $self->_append_menu_item($fileMenu, "Slice to SV&G…\tCtrl+G", 'Slice file to SVG', sub {
             $self->quick_slice(save_as => 1, export_svg => 1);
-        });
+        }, undef, 'shape_handles.png');
         $fileMenu->AppendSeparator();
         $self->_append_menu_item($fileMenu, "Repair STL file…", 'Automatically repair an STL file', sub {
             $self->repair_stl;
-        });
+        }, undef, 'wrench.png');
         $fileMenu->AppendSeparator();
         $self->_append_menu_item($fileMenu, "Preferences…", 'Application preferences', sub {
             Slic3r::GUI::Preferences->new($self)->ShowModal;
@@ -207,13 +213,13 @@ sub _init_menubar {
         $self->{plater_menu} = Wx::Menu->new;
         $self->_append_menu_item($self->{plater_menu}, "Export G-code...", 'Export current plate as G-code', sub {
             $plater->export_gcode;
-        });
+        }, undef, 'cog_go.png');
         $self->_append_menu_item($self->{plater_menu}, "Export plate as STL...", 'Export current plate as STL', sub {
             $plater->export_stl;
-        });
+        }, undef, 'brick_go.png');
         $self->_append_menu_item($self->{plater_menu}, "Export plate as AMF...", 'Export current plate as AMF', sub {
             $plater->export_amf;
-        });
+        }, undef, 'brick_go.png');
         
         $self->{object_menu} = $self->{plater}->object_menu;
         $self->on_plater_selection_changed(0);
@@ -226,22 +232,22 @@ sub _init_menubar {
         if (!$self->{no_plater}) {
             $self->_append_menu_item($windowMenu, "Select &Plater Tab\tCtrl+1", 'Show the plater', sub {
                 $self->select_tab(0);
-            });
+            }, undef, 'application_view_tile.png');
             $self->_append_menu_item($windowMenu, "Select &Controller Tab\tCtrl+T", 'Show the printer controller', sub {
                 $self->select_tab(1);
-            });
+            }, undef, 'printer_empty.png');
             $windowMenu->AppendSeparator();
             $tab_offset += 2;
         }
         $self->_append_menu_item($windowMenu, "Select P&rint Settings Tab\tCtrl+2", 'Show the print settings', sub {
             $self->select_tab($tab_offset+0);
-        });
+        }, undef, 'cog.png');
         $self->_append_menu_item($windowMenu, "Select &Filament Settings Tab\tCtrl+3", 'Show the filament settings', sub {
             $self->select_tab($tab_offset+1);
-        });
+        }, undef, 'spool.png');
         $self->_append_menu_item($windowMenu, "Select Print&er Settings Tab\tCtrl+4", 'Show the printer settings', sub {
             $self->select_tab($tab_offset+2);
-        });
+        }, undef, 'printer_empty.png');
     }
     
     # Help menu
@@ -313,7 +319,7 @@ sub quick_slice {
                 $dialog->Destroy;
                 return;
             }
-            $input_file = $dialog->GetPaths;
+            $input_file = Slic3r::decode_path($dialog->GetPaths);
             $dialog->Destroy;
             $last_input_file = $input_file unless $params{export_svg};
         } else {
@@ -373,7 +379,7 @@ sub quick_slice {
                 $dlg->Destroy;
                 return;
             }
-            $output_file = $dlg->GetPath;
+            $output_file = Slic3r::decode_path($dlg->GetPath);
             $last_output_file = $output_file unless $params{export_svg};
             $Slic3r::GUI::Settings->{_}{last_output_path} = dirname($output_file);
             wxTheApp->save_settings;
@@ -420,7 +426,7 @@ sub repair_stl {
             $dialog->Destroy;
             return;
         }
-        $input_file = $dialog->GetPaths;
+        $input_file = Slic3r::decode_path($dialog->GetPaths);
         $dialog->Destroy;
     }
     
@@ -433,7 +439,7 @@ sub repair_stl {
             $dlg->Destroy;
             return undef;
         }
-        $output_file = $dlg->GetPath;
+        $output_file = Slic3r::decode_path($dlg->GetPath);
         $dlg->Destroy;
     }
     
@@ -470,7 +476,7 @@ sub export_config {
     my $dlg = Wx::FileDialog->new($self, 'Save configuration as:', $dir, $filename, 
         &Slic3r::GUI::FILE_WILDCARDS->{ini}, wxFD_SAVE | wxFD_OVERWRITE_PROMPT);
     if ($dlg->ShowModal == wxID_OK) {
-        my $file = $dlg->GetPath;
+        my $file = Slic3r::decode_path($dlg->GetPath);
         $Slic3r::GUI::Settings->{recent}{config_directory} = dirname($file);
         wxTheApp->save_settings;
         $last_config = $file;
@@ -489,7 +495,7 @@ sub load_config_file {
         my $dlg = Wx::FileDialog->new($self, 'Select configuration to load:', $dir, "config.ini", 
                 &Slic3r::GUI::FILE_WILDCARDS->{ini}, wxFD_OPEN | wxFD_FILE_MUST_EXIST);
         return unless $dlg->ShowModal == wxID_OK;
-        ($file) = $dlg->GetPaths;
+        $file = Slic3r::decode_path($dlg->GetPaths);
         $dlg->Destroy;
     }
     $Slic3r::GUI::Settings->{recent}{config_directory} = dirname($file);
@@ -514,7 +520,7 @@ sub export_configbundle {
     my $dlg = Wx::FileDialog->new($self, 'Save presets bundle as:', $dir, $filename, 
         &Slic3r::GUI::FILE_WILDCARDS->{ini}, wxFD_SAVE | wxFD_OVERWRITE_PROMPT);
     if ($dlg->ShowModal == wxID_OK) {
-        my $file = $dlg->GetPath;
+        my $file = Slic3r::decode_path($dlg->GetPath);
         $Slic3r::GUI::Settings->{recent}{config_directory} = dirname($file);
         wxTheApp->save_settings;
         
@@ -547,7 +553,7 @@ sub load_configbundle {
     my $dlg = Wx::FileDialog->new($self, 'Select configuration to load:', $dir, "config.ini", 
             &Slic3r::GUI::FILE_WILDCARDS->{ini}, wxFD_OPEN | wxFD_FILE_MUST_EXIST);
     return unless $dlg->ShowModal == wxID_OK;
-    my ($file) = $dlg->GetPaths;
+    my $file = Slic3r::decode_path($dlg->GetPaths);
     $dlg->Destroy;
     
     $Slic3r::GUI::Settings->{recent}{config_directory} = dirname($file);
@@ -601,6 +607,9 @@ sub load_config {
     foreach my $tab (values %{$self->{options_tabs}}) {
         $tab->load_config($config);
     }
+    if ($self->{plater}) {
+        $self->{plater}->on_config_change($config);
+    }
 }
 
 sub config_wizard {
@@ -643,13 +652,19 @@ sub config {
     if (!$self->{plater} || $self->{plater}->filament_presets == 1 || $self->{mode} eq 'simple') {
         $filament_config = $self->{options_tabs}{filament}->config;
     } else {
-        # TODO: handle dirty presets.
-        # perhaps plater shouldn't expose dirty presets at all in multi-extruder environments.
         my $i = -1;
         foreach my $preset_idx ($self->{plater}->filament_presets) {
             $i++;
-            my $preset = $self->{options_tabs}{filament}->get_preset($preset_idx);
-            my $config = $self->{options_tabs}{filament}->get_preset_config($preset);
+            my $config;
+            if ($preset_idx == $self->{options_tabs}{filament}->current_preset) {
+                # the selected preset for this extruder is the one in the tab
+                # use the tab's config instead of the preset in case it is dirty
+                # perhaps plater shouldn't expose dirty presets at all in multi-extruder environments.
+                $config = $self->{options_tabs}{filament}->config;
+            } else {
+                my $preset = $self->{options_tabs}{filament}->get_preset($preset_idx);
+                $config = $self->{options_tabs}{filament}->get_preset_config($preset);
+            }
             if (!$filament_config) {
                 $filament_config = $config->clone;
                 next;
@@ -719,12 +734,23 @@ sub select_tab {
 }
 
 sub _append_menu_item {
-    my ($self, $menu, $string, $description, $cb, $id) = @_;
+    my ($self, $menu, $string, $description, $cb, $id, $icon) = @_;
     
     $id //= &Wx::NewId();
     my $item = $menu->Append($id, $string, $description);
+    $self->_set_menu_item_icon($item, $icon);
+    
     EVT_MENU($self, $id, $cb);
     return $item;
 }
 
+sub _set_menu_item_icon {
+    my ($self, $menuItem, $icon) = @_;
+    
+    # SetBitmap was not available on OS X before Wx 0.9927
+    if ($icon && $menuItem->can('SetBitmap')) {
+        $menuItem->SetBitmap(Wx::Bitmap->new("$Slic3r::var/$icon", wxBITMAP_TYPE_PNG));
+    }
+}
+
 1;
diff --git a/lib/Slic3r/GUI/OptionsGroup.pm b/lib/Slic3r/GUI/OptionsGroup.pm
index e8f02ba68..f73fdf697 100644
--- a/lib/Slic3r/GUI/OptionsGroup.pm
+++ b/lib/Slic3r/GUI/OptionsGroup.pm
@@ -178,6 +178,11 @@ sub _build_field {
             parent => $self->parent,
             option => $opt,
         );
+    } elsif ($type eq 'color') {
+        $field = Slic3r::GUI::OptionsGroup::Field::ColourPicker->new(
+            parent => $self->parent,
+            option => $opt,
+        );
     } elsif ($type =~ /^(f|s|s@|percent)$/) {
         $field = Slic3r::GUI::OptionsGroup::Field::TextCtrl->new(
             parent => $self->parent,
diff --git a/lib/Slic3r/GUI/OptionsGroup/Field.pm b/lib/Slic3r/GUI/OptionsGroup/Field.pm
index 8a181355d..18f5b2b56 100644
--- a/lib/Slic3r/GUI/OptionsGroup/Field.pm
+++ b/lib/Slic3r/GUI/OptionsGroup/Field.pm
@@ -7,7 +7,6 @@ has 'parent'                => (is => 'ro', required => 1);
 has 'option'                => (is => 'ro', required => 1);     # Slic3r::GUI::OptionsGroup::Option
 has 'on_change'             => (is => 'rw', default => sub { sub {} });
 has 'on_kill_focus'         => (is => 'rw', default => sub { sub {} });
-has 'wxSsizer'              => (is => 'rw');                    # alternatively, wxSizer object
 has 'disable_change_event'  => (is => 'rw', default => sub { 0 });
 
 # This method should not fire the on_change event
@@ -128,6 +127,8 @@ extends 'Slic3r::GUI::OptionsGroup::Field::wxWindow';
 use Wx qw(:misc);
 use Wx::Event qw(EVT_SPINCTRL EVT_TEXT EVT_KILL_FOCUS);
 
+has 'tmp_value' => (is => 'rw');
+
 sub BUILD {
     my ($self) = @_;
     
@@ -139,13 +140,27 @@ sub BUILD {
         $self->_on_change($self->option->opt_id);
     });
     EVT_TEXT($self->parent, $field, sub {
+        my ($s, $event) = @_;
+        
+        # On OSX/Cocoa, wxSpinCtrl::GetValue() doesn't return the new value
+        # when it was changed from the text control, so the on_change callback
+        # gets the old one, and on_kill_focus resets the control to the old value.
+        # As a workaround, we get the new value from $event->GetString and store
+        # here temporarily so that we can return it from $self->get_value
+        $self->tmp_value($event->GetString);
         $self->_on_change($self->option->opt_id);
+        $self->tmp_value(undef);
     });
     EVT_KILL_FOCUS($field, sub {
         $self->_on_kill_focus($self->option->opt_id, @_);
     });
 }
 
+sub get_value {
+    my ($self) = @_;
+    return $self->tmp_value // $self->wxWindow->GetValue;
+}
+
 
 package Slic3r::GUI::OptionsGroup::Field::TextCtrl;
 use Moo;
@@ -261,6 +276,9 @@ use List::Util qw(first);
 use Wx qw(wxTheApp :misc :combobox);
 use Wx::Event qw(EVT_COMBOBOX EVT_TEXT);
 
+# if option has no 'values', indices are values
+# if option has no 'labels', values are labels
+
 sub BUILD {
     my ($self) = @_;
     
@@ -274,15 +292,15 @@ sub BUILD {
         my $disable_change_event = $self->disable_change_event;
         $self->disable_change_event(1);
         
-        my $value = $field->GetSelection;
+        my $idx = $field->GetSelection;  # get index of selected value
         my $label;
         
-        if ($self->option->values) {
-            $label = $value = $self->option->values->[$value];
-        } elsif ($value <= $#{$self->option->labels}) {
-            $label = $self->option->labels->[$value];
+        if ($self->option->labels && $idx <= $#{$self->option->labels}) {
+            $label = $self->option->labels->[$idx];
+        } elsif ($self->option->values && $idx <= $#{$self->option->values}) {
+            $label = $self->option->values->[$idx];
         } else {
-            $label = $value;
+            $label = $idx;
         }
         
         # The MSW implementation of wxComboBox will leave the field blank if we call
@@ -322,8 +340,8 @@ sub set_value {
                 $self->disable_change_event(0);
                 return;
             }
-        }
-        if ($self->option->labels && $value <= $#{$self->option->labels}) {
+        } elsif ($self->option->labels && $value <= $#{$self->option->labels}) {
+            # if we have no values, we expect value to be an index
             $field->SetValue($self->option->labels->[$value]);
             $self->disable_change_event(0);
             return;
@@ -351,6 +369,47 @@ sub get_value {
 }
 
 
+package Slic3r::GUI::OptionsGroup::Field::ColourPicker;
+use Moo;
+extends 'Slic3r::GUI::OptionsGroup::Field::wxWindow';
+
+use Wx qw(:misc :colour);
+use Wx::Event qw(EVT_COLOURPICKER_CHANGED);
+
+sub BUILD {
+    my ($self) = @_;
+    
+    my $field = Wx::ColourPickerCtrl->new($self->parent, -1, 
+        $self->_string_to_colour($self->option->default), wxDefaultPosition, 
+        $self->_default_size);
+    $self->wxWindow($field);
+    
+    EVT_COLOURPICKER_CHANGED($self->parent, $field, sub {
+        $self->_on_change($self->option->opt_id);
+    });
+}
+
+sub set_value {
+    my ($self, $value) = @_;
+    
+    $self->disable_change_event(1);
+    $self->wxWindow->SetColour($self->_string_to_colour($value));
+    $self->disable_change_event(0);
+}
+
+sub get_value {
+    my ($self) = @_;
+    return $self->wxWindow->GetColour->GetAsString(wxC2S_HTML_SYNTAX);
+}
+
+sub _string_to_colour {
+    my ($self, $string) = @_;
+    
+    $string =~ s/^#//;
+    return Wx::Colour->new(unpack 'C*', pack 'H*', $string);
+}
+
+
 package Slic3r::GUI::OptionsGroup::Field::wxSizer;
 use Moo;
 extends 'Slic3r::GUI::OptionsGroup::Field';
diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index bb344e50e..d38c83d6f 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -4,14 +4,14 @@ use warnings;
 use utf8;
 
 use File::Basename qw(basename dirname);
-use List::Util qw(sum first);
+use List::Util qw(sum first max);
 use Slic3r::Geometry qw(X Y Z MIN MAX scale unscale deg2rad);
 use threads::shared qw(shared_clone);
 use Wx qw(:button :cursor :dialog :filedialog :keycode :icon :font :id :listctrl :misc 
-    :panel :sizer :toolbar :window wxTheApp :notebook);
+    :panel :sizer :toolbar :window wxTheApp :notebook :combobox);
 use Wx::Event qw(EVT_BUTTON EVT_COMMAND EVT_KEY_DOWN EVT_LIST_ITEM_ACTIVATED 
     EVT_LIST_ITEM_DESELECTED EVT_LIST_ITEM_SELECTED EVT_MOUSE_EVENTS EVT_PAINT EVT_TOOL 
-    EVT_CHOICE EVT_TIMER EVT_NOTEBOOK_PAGE_CHANGED);
+    EVT_CHOICE EVT_COMBOBOX EVT_TIMER EVT_NOTEBOOK_PAGE_CHANGED);
 use base 'Wx::Panel';
 
 use constant TB_ADD             => &Wx::NewId;
@@ -36,7 +36,7 @@ our $ERROR_EVENT             : shared = Wx::NewEventType;
 our $EXPORT_COMPLETED_EVENT  : shared = Wx::NewEventType;
 our $PROCESS_COMPLETED_EVENT : shared = Wx::NewEventType;
 
-use constant FILAMENT_CHOOSERS_SPACING => 3;
+use constant FILAMENT_CHOOSERS_SPACING => 0;
 use constant PROCESS_DELAY => 0.5 * 1000; # milliseconds
 
 my $PreventListEvents = 0;
@@ -335,12 +335,11 @@ sub new {
             for my $group (qw(print filament printer)) {
                 my $text = Wx::StaticText->new($self, -1, "$group_labels{$group}:", wxDefaultPosition, wxDefaultSize, wxALIGN_RIGHT);
                 $text->SetFont($Slic3r::GUI::small_font);
-                my $choice = Wx::Choice->new($self, -1, wxDefaultPosition, wxDefaultSize, []);
-                $choice->SetFont($Slic3r::GUI::small_font);
+                my $choice = Wx::BitmapComboBox->new($self, -1, "", wxDefaultPosition, wxDefaultSize, [], wxCB_READONLY);
                 $self->{preset_choosers}{$group} = [$choice];
-                EVT_CHOICE($choice, $choice, sub { $self->_on_select_preset($group, @_) });
+                EVT_COMBOBOX($choice, $choice, sub { $self->_on_select_preset($group, @_) });
                 $presets->Add($text, 0, wxALIGN_RIGHT | wxALIGN_CENTER_VERTICAL | wxRIGHT, 4);
-                $presets->Add($choice, 1, wxALIGN_CENTER_VERTICAL | wxEXPAND | wxBOTTOM, 8);
+                $presets->Add($choice, 1, wxALIGN_CENTER_VERTICAL | wxEXPAND | wxBOTTOM, 0);
             }
         }
         
@@ -446,13 +445,33 @@ sub GetFrame {
 
 sub update_presets {
     my $self = shift;
-    my ($group, $items, $selected) = @_;
+    my ($group, $presets, $selected) = @_;
     
     foreach my $choice (@{ $self->{preset_choosers}{$group} }) {
         my $sel = $choice->GetSelection;
         $choice->Clear;
-        $choice->Append($_) for @$items;
-        $choice->SetSelection($sel) if $sel <= $#$items;
+        foreach my $preset (@$presets) {
+            my $bitmap;
+            if ($group eq 'filament') {
+                my $config = $preset->config(['filament_colour']);
+                my $rgb_hex = $config->filament_colour->[0];
+                if ($preset->default) {
+                    $bitmap = Wx::Bitmap->new("$Slic3r::var/spool.png", wxBITMAP_TYPE_PNG);
+                } else {
+                    $rgb_hex =~ s/^#//;
+                    my @rgb = unpack 'C*', pack 'H*', $rgb_hex;
+                    my $image = Wx::Image->new(16,16);
+                    $image->SetRGB(Wx::Rect->new(0,0,16,16), @rgb);
+                    $bitmap = Wx::Bitmap->new($image);
+                }
+            } elsif ($group eq 'print') {
+                $bitmap = Wx::Bitmap->new("$Slic3r::var/cog.png", wxBITMAP_TYPE_PNG);
+            } elsif ($group eq 'printer') {
+                $bitmap = Wx::Bitmap->new("$Slic3r::var/printer_empty.png", wxBITMAP_TYPE_PNG);
+            }
+            $choice->AppendString($preset->name, $bitmap);
+        }
+        $choice->SetSelection($sel) if $sel <= $#$presets;
     }
     $self->{preset_choosers}{$group}[0]->SetSelection($selected);
 }
@@ -497,8 +516,11 @@ sub load_model_objects {
     my ($self, @model_objects) = @_;
     
     my $bed_centerf = $self->bed_centerf;
+    my $bed_shape = Slic3r::Polygon->new_scale(@{$self->{config}->bed_shape});
+    my $bed_size = $bed_shape->bounding_box->size;
     
     my $need_arrange = 0;
+    my $scaled_down = 0;
     my @obj_idx = ();
     foreach my $model_object (@model_objects) {
         my $o = $self->{model}->add_object($model_object);
@@ -516,6 +538,16 @@ sub load_model_objects {
             $o->center_around_origin;  # also aligns object to Z = 0
             $o->add_instance(offset => $bed_centerf);
         }
+        
+        {
+            # if the object is too large (more than 5 times the bed), scale it down
+            my $size = $o->bounding_box->size;
+            my $ratio = max(@$size[X,Y]) / unscale(max(@$bed_size[X,Y]));
+            if ($ratio > 5) {
+                $_->set_scaling_factor(1/$ratio) for @{$o->instances};
+                $scaled_down = 1;
+            }
+        }
     
         $self->{print}->auto_assign_extruders($o);
         $self->{print}->add_model_object($o);
@@ -526,14 +558,15 @@ sub load_model_objects {
         $need_arrange = 0;
     }
     
-    $self->objects_loaded(\@obj_idx, no_arrange => !$need_arrange);
-}
-
-sub objects_loaded {
-    my $self = shift;
-    my ($obj_idxs, %params) = @_;
+    if ($scaled_down) {
+        Slic3r::GUI::show_info(
+            $self,
+            'Your object appears to be too large, so it was automatically scaled down to fit your print bed.',
+            'Object too large?',
+        );
+    }
     
-    foreach my $obj_idx (@$obj_idxs) {
+    foreach my $obj_idx (@obj_idx) {
         my $object = $self->{objects}[$obj_idx];
         my $model_object = $self->{model}->objects->[$obj_idx];
         $self->{list}->InsertStringItem($obj_idx, $object->name);
@@ -545,7 +578,7 @@ sub objects_loaded {
     
         $self->make_thumbnail($obj_idx);
     }
-    $self->arrange unless $params{no_arrange};
+    $self->arrange if $need_arrange;
     $self->update;
     
     # zoom to objects
@@ -553,7 +586,7 @@ sub objects_loaded {
         if $self->{canvas3D};
     
     $self->{list}->Update;
-    $self->{list}->Select($obj_idxs->[-1], 1);
+    $self->{list}->Select($obj_idx[-1], 1);
     $self->object_list_changed;
     
     $self->schedule_background_process;
@@ -691,6 +724,7 @@ sub rotate {
     my $self = shift;
     my ($angle, $axis) = @_;
     
+    # angle is in degrees
     $axis //= Z;
     
     my ($obj_idx, $object) = $self->selected_object;
@@ -712,14 +746,14 @@ sub rotate {
     $self->stop_background_process;
     
     if ($axis == Z) {
-        my $new_angle = $model_instance->rotation + $angle;
+        my $new_angle = $model_instance->rotation + deg2rad($angle);
         $_->set_rotation($new_angle) for @{ $model_object->instances };
         $object->transform_thumbnail($self->{model}, $obj_idx);
     } else {
         # rotation around X and Y needs to be performed on mesh
         # so we first apply any Z rotation
         if ($model_instance->rotation != 0) {
-            $model_object->rotate(deg2rad($model_instance->rotation), Z);
+            $model_object->rotate($model_instance->rotation, Z);
             $_->set_rotation(0) for @{ $model_object->instances };
         }
         $model_object->rotate(deg2rad($angle), $axis);
@@ -749,7 +783,7 @@ sub flip {
     
     # apply Z rotation before flipping
     if ($model_instance->rotation != 0) {
-        $model_object->rotate(deg2rad($model_instance->rotation), Z);
+        $model_object->rotate($model_instance->rotation, Z);
         $_->set_rotation(0) for @{ $model_object->instances };
     }
     
@@ -788,7 +822,7 @@ sub changescale {
         
         # apply Z rotation before scaling
         if ($model_instance->rotation != 0) {
-            $model_object->rotate(deg2rad($model_instance->rotation), Z);
+            $model_object->rotate($model_instance->rotation, Z);
             $_->set_rotation(0) for @{ $model_object->instances };
         }
         
@@ -1054,9 +1088,10 @@ sub export_gcode {
             $dlg->Destroy;
             return;
         }
-        $Slic3r::GUI::Settings->{_}{last_output_path} = dirname($dlg->GetPath);
+        my $path = Slic3r::decode_path($dlg->GetPath);
+        $Slic3r::GUI::Settings->{_}{last_output_path} = dirname($path);
         wxTheApp->save_settings;
-        $self->{export_gcode_output_file} = $Slic3r::GUI::MainFrame::last_output_file = $dlg->GetPath;
+        $self->{export_gcode_output_file} = $Slic3r::GUI::MainFrame::last_output_file = $path;
         $dlg->Destroy;
     }
     
@@ -1066,6 +1101,11 @@ sub export_gcode {
         $self->statusbar->SetCancelCallback(sub {
             $self->stop_background_process;
             $self->statusbar->SetStatusText("Export cancelled");
+            $self->{export_gcode_output_file} = undef;
+            $self->{send_gcode_file} = undef;
+            
+            # this updates buttons status
+            $self->object_list_changed;
         });
         
         # start background process, whose completion event handler
@@ -1275,7 +1315,7 @@ sub _get_export_file {
             $dlg->Destroy;
             return undef;
         }
-        $output_file = $Slic3r::GUI::MainFrame::last_output_file = $dlg->GetPath;
+        $output_file = $Slic3r::GUI::MainFrame::last_output_file = Slic3r::decode_path($dlg->GetPath);
         $dlg->Destroy;
     }
     return $output_file;
@@ -1344,11 +1384,10 @@ sub on_extruders_change {
     my $choices = $self->{preset_choosers}{filament};
     while (@$choices < $num_extruders) {
         my @presets = $choices->[0]->GetStrings;
-        push @$choices, Wx::Choice->new($self, -1, wxDefaultPosition, [150, -1], [@presets]);
-        $choices->[-1]->SetFont($Slic3r::GUI::small_font);
+        push @$choices, Wx::BitmapComboBox->new($self, -1, "", wxDefaultPosition, wxDefaultSize, [@presets], wxCB_READONLY);
         $self->{presets_sizer}->Insert(4 + ($#$choices-1)*2, 0, 0);
         $self->{presets_sizer}->Insert(5 + ($#$choices-1)*2, $choices->[-1], 0, wxEXPAND | wxBOTTOM, FILAMENT_CHOOSERS_SPACING);
-        EVT_CHOICE($choices->[-1], $choices->[-1], sub { $self->_on_select_preset('filament', @_) });
+        EVT_COMBOBOX($choices->[-1], $choices->[-1], sub { $self->_on_select_preset('filament', @_) });
         my $i = first { $choices->[-1]->GetString($_) eq ($Slic3r::GUI::Settings->{presets}{"filament_" . $#$choices} || '') } 0 .. $#presets;
         $choices->[-1]->SetSelection($i || 0);
     }
@@ -1616,26 +1655,27 @@ sub object_menu {
     my $menu = Wx::Menu->new;
     $frame->_append_menu_item($menu, "Delete\tCtrl+Del", 'Remove the selected object', sub {
         $self->remove;
-    });
+    }, undef, 'brick_delete.png');
     $frame->_append_menu_item($menu, "Increase copies\tCtrl++", 'Place one more copy of the selected object', sub {
         $self->increase;
-    });
+    }, undef, 'add.png');
     $frame->_append_menu_item($menu, "Decrease copies\tCtrl+-", 'Remove one copy of the selected object', sub {
         $self->decrease;
-    });
+    }, undef, 'delete.png');
     $frame->_append_menu_item($menu, "Set number of copies…", 'Change the number of copies of the selected object', sub {
         $self->set_number_of_copies;
-    });
+    }, undef, 'textfield.png');
     $menu->AppendSeparator();
     $frame->_append_menu_item($menu, "Rotate 45° clockwise", 'Rotate the selected object by 45° clockwise', sub {
         $self->rotate(-45);
-    });
+    }, undef, 'arrow_rotate_clockwise.png');
     $frame->_append_menu_item($menu, "Rotate 45° counter-clockwise", 'Rotate the selected object by 45° counter-clockwise', sub {
         $self->rotate(+45);
-    });
+    }, undef, 'arrow_rotate_anticlockwise.png');
     
     my $rotateMenu = Wx::Menu->new;
-    $menu->AppendSubMenu($rotateMenu, "Rotate", 'Rotate the selected object by an arbitrary angle');
+    my $rotateMenuItem = $menu->AppendSubMenu($rotateMenu, "Rotate", 'Rotate the selected object by an arbitrary angle');
+    $frame->_set_menu_item_icon($rotateMenuItem, 'textfield.png');
     $frame->_append_menu_item($rotateMenu, "Around X axis…", 'Rotate the selected object by an arbitrary angle around X axis', sub {
         $self->rotate(undef, X);
     });
@@ -1647,7 +1687,8 @@ sub object_menu {
     });
     
     my $flipMenu = Wx::Menu->new;
-    $menu->AppendSubMenu($flipMenu, "Flip", 'Mirror the selected object');
+    my $flipMenuItem = $menu->AppendSubMenu($flipMenu, "Flip", 'Mirror the selected object');
+    $frame->_set_menu_item_icon($flipMenuItem, 'shape_flip_horizontal.png');
     $frame->_append_menu_item($flipMenu, "Along X axis…", 'Mirror the selected object along the X axis', sub {
         $self->flip(X);
     });
@@ -1659,7 +1700,8 @@ sub object_menu {
     });
     
     my $scaleMenu = Wx::Menu->new;
-    $menu->AppendSubMenu($scaleMenu, "Scale", 'Scale the selected object along a single axis');
+    my $scaleMenuItem = $menu->AppendSubMenu($scaleMenu, "Scale", 'Scale the selected object along a single axis');
+    $frame->_set_menu_item_icon($scaleMenuItem, 'arrow_out.png');
     $frame->_append_menu_item($scaleMenu, "Uniformly…", 'Scale the selected object along the XYZ axes', sub {
         $self->changescale(undef);
     });
@@ -1675,18 +1717,18 @@ sub object_menu {
     
     $frame->_append_menu_item($menu, "Split", 'Split the selected object into individual parts', sub {
         $self->split_object;
-    });
+    }, undef, 'shape_ungroup.png');
     $frame->_append_menu_item($menu, "Cut…", 'Open the 3D cutting tool', sub {
         $self->object_cut_dialog;
-    });
+    }, undef, 'package.png');
     $menu->AppendSeparator();
     $frame->_append_menu_item($menu, "Settings…", 'Open the object editor dialog', sub {
         $self->object_settings_dialog;
-    });
+    }, undef, 'cog.png');
     $menu->AppendSeparator();
     $frame->_append_menu_item($menu, "Export object as STL…", 'Export this single object as STL file', sub {
         $self->export_object_stl;
-    });
+    }, undef, 'brick_go.png');
     
     return $menu;
 }
@@ -1763,7 +1805,7 @@ sub transform_thumbnail {
     # the order of these transformations MUST be the same everywhere, including
     # in Slic3r::Print->add_model_object()
     my $t = $self->thumbnail->clone;
-    $t->rotate(deg2rad($model_instance->rotation), Slic3r::Point->new(0,0));
+    $t->rotate($model_instance->rotation, Slic3r::Point->new(0,0));
     $t->scale($model_instance->scaling_factor);
     
     $self->transformed_thumbnail($t);
diff --git a/lib/Slic3r/GUI/Plater/2DToolpaths.pm b/lib/Slic3r/GUI/Plater/2DToolpaths.pm
index 8ab289855..3daa3b94c 100644
--- a/lib/Slic3r/GUI/Plater/2DToolpaths.pm
+++ b/lib/Slic3r/GUI/Plater/2DToolpaths.pm
@@ -84,6 +84,7 @@ sub reload_print {
     }
     
     $self->{canvas}->bb($self->print->total_bounding_box);
+    $self->{canvas}->_dirty(1);
     
     my %z = ();  # z => 1
     foreach my $object (@{$self->{print}->objects}) {
@@ -115,15 +116,23 @@ sub set_z {
 
 package Slic3r::GUI::Plater::2DToolpaths::Canvas;
 
-use Wx::Event qw(EVT_PAINT EVT_SIZE EVT_ERASE_BACKGROUND EVT_MOUSEWHEEL EVT_MOUSE_EVENTS);
+use Wx::Event qw(EVT_PAINT EVT_SIZE EVT_IDLE EVT_MOUSEWHEEL EVT_MOUSE_EVENTS);
 use OpenGL qw(:glconstants :glfunctions :glufunctions :gluconstants);
 use base qw(Wx::GLCanvas Class::Accessor);
 use Wx::GLCanvas qw(:all);
-use List::Util qw(min first);
-use Slic3r::Geometry qw(scale unscale epsilon);
+use List::Util qw(min max first);
+use Slic3r::Geometry qw(scale unscale epsilon X Y);
 use Slic3r::Print::State ':steps';
 
-__PACKAGE__->mk_accessors(qw(print z layers color init bb));
+__PACKAGE__->mk_accessors(qw(
+    print z layers color init
+    bb
+    _camera_bb
+    _dirty
+    _zoom
+    _camera_target
+    _drag_start_xy
+));
 
 # make OpenGL::Array thread-safe
 {
@@ -136,20 +145,99 @@ sub new {
     
     my $self = $class->SUPER::new($parent);
     $self->print($print);
+    $self->_zoom(1);
+    
+    # 2D point in model space
+    $self->_camera_target(Slic3r::Pointf->new(0,0));
     
     EVT_PAINT($self, sub {
         my $dc = Wx::PaintDC->new($self);
         $self->Render($dc);
     });
-    EVT_SIZE($self, sub {
+    EVT_SIZE($self, sub { $self->_dirty(1) });
+    EVT_IDLE($self, sub {
+        return unless $self->_dirty;
         return if !$self->IsShownOnScreen;
-        $self->Resize( $self->GetSizeWH );
+        $self->Resize;
         $self->Refresh;
     });
+    EVT_MOUSEWHEEL($self, sub {
+        my ($self, $e) = @_;
+        
+        my $old_zoom = $self->_zoom;
+        
+        # Calculate the zoom delta and apply it to the current zoom factor
+        my $zoom = $e->GetWheelRotation() / $e->GetWheelDelta();
+        $zoom = max(min($zoom, 4), -4);
+        $zoom /= 10;
+        $self->_zoom($self->_zoom / (1-$zoom));
+        $self->_zoom(1) if $self->_zoom > 1;  # prevent from zooming out too much
+        
+        {
+            # In order to zoom around the mouse point we need to translate
+            # the camera target. This math is almost there but not perfect yet...
+            my $camera_bb_size = $self->_camera_bb->size;
+            my $size = Slic3r::Pointf->new($self->GetSizeWH);
+            my $pos = Slic3r::Pointf->new($e->GetPositionXY);
+            
+            # calculate the zooming center in pixel coordinates relative to the viewport center
+            my $vec = Slic3r::Pointf->new($pos->x - $size->x/2, $pos->y - $size->y/2);  #-
+            
+            # calculate where this point will end up after applying the new zoom
+            my $vec2 = $vec->clone;
+            $vec2->scale($old_zoom / $self->_zoom);
+            
+            # move the camera target by the difference of the two positions
+            $self->_camera_target->translate(
+                -($vec->x - $vec2->x) * $camera_bb_size->x / $size->x,
+                 ($vec->y - $vec2->y) * $camera_bb_size->y / $size->y,  #//
+            );
+        }
+        
+        $self->_dirty(1);
+        $self->Refresh;
+    });
+    EVT_MOUSE_EVENTS($self, \&mouse_event);
     
     return $self;
 }
 
+sub mouse_event {
+    my ($self, $e) = @_;
+    
+    my $pos = Slic3r::Pointf->new($e->GetPositionXY);
+    if ($e->Entering && &Wx::wxMSW) {
+        # wxMSW needs focus in order to catch mouse wheel events
+        $self->SetFocus;
+    } elsif ($e->Dragging) {
+        if ($e->LeftIsDown || $e->MiddleIsDown || $e->RightIsDown) {
+            # if dragging, translate view
+            
+            if (defined $self->_drag_start_xy) {
+                my $move = $self->_drag_start_xy->vector_to($pos);  # in pixels
+                
+                # get viewport and camera size in order to convert pixel to model units
+                my ($x, $y) = $self->GetSizeWH;
+                my $camera_bb_size = $self->_camera_bb->size;
+                
+                # compute translation in model units
+                $self->_camera_target->translate(
+                    -$move->x * $camera_bb_size->x / $x,
+                     $move->y * $camera_bb_size->y / $y,   # /**
+                );
+                
+                $self->_dirty(1);
+                $self->Refresh;
+            }
+            $self->_drag_start_xy($pos);
+        }
+    } elsif ($e->LeftUp || $e->MiddleUp || $e->RightUp) {
+        $self->_drag_start_xy(undef);
+    } else {
+        $e->Skip();
+    }
+}
+
 sub set_z {
     my ($self, $z) = @_;
     
@@ -197,22 +285,6 @@ sub Render {
         return;
     }
     
-    glMatrixMode(GL_PROJECTION);
-    glLoadIdentity();
-    my $bb = $self->bb;
-    my ($x1, $y1, $x2, $y2) = ($bb->x_min, $bb->y_min, $bb->x_max, $bb->y_max);
-    my ($x, $y) = $self->GetSizeWH;
-    if (($x2 - $x1)/($y2 - $y1) > $x/$y) {
-        # adjust Y
-        my $new_y = $y * ($x2 - $x1) / $x;
-        $y1 = ($y2 + $y1)/2 - $new_y/2;
-        $y2 = $y1 + $new_y;
-    } else {
-        my $new_x = $x * ($y2 - $y1) / $y;
-        $x1 = ($x2 + $x1)/2 - $new_x/2;
-        $x2 = $x1 + $new_x;
-    }
-    glOrtho($x1, $x2, $y1, $y2, 0, 1);
     glDisable(GL_DEPTH_TEST);
     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();
@@ -398,12 +470,71 @@ sub SetCurrent {
 }
 
 sub Resize {
-    my ($self, $x, $y) = @_;
+    my ($self) = @_;
  
     return unless $self->GetContext;
+    return unless $self->bb;
+    $self->_dirty(0);
     
     $self->SetCurrent($self->GetContext);
+    my ($x, $y) = $self->GetSizeWH;
     glViewport(0, 0, $x, $y);
+    
+    glMatrixMode(GL_PROJECTION);
+    glLoadIdentity();
+    
+    my $bb = $self->bb->clone;
+    
+    # center bounding box around origin before scaling it
+    my $bb_center = $bb->center;
+    $bb->translate(@{$bb_center->negative});
+    
+    # scale bounding box according to zoom factor
+    $bb->scale($self->_zoom);
+    
+    # reposition bounding box around original center
+    $bb->translate(@{$bb_center});
+    
+    # translate camera
+    $bb->translate(@{$self->_camera_target});
+    
+    # keep camera_bb within total bb
+    # (i.e. prevent user from panning outside the bounding box)
+    {
+        my @translate = (0,0);
+        if ($bb->x_min < $self->bb->x_min) {
+            $translate[X] += $self->bb->x_min - $bb->x_min;
+        }
+        if ($bb->y_min < $self->bb->y_min) {
+            $translate[Y] += $self->bb->y_min - $bb->y_min;
+        }
+        if ($bb->x_max > $self->bb->x_max) {
+            $translate[X] -= $bb->x_max - $self->bb->x_max;
+        }
+        if ($bb->y_max > $self->bb->y_max) {
+            $translate[Y] -= $bb->y_max - $self->bb->y_max;
+        }
+        $self->_camera_target->translate(@translate);
+        $bb->translate(@translate);
+    }
+    
+    # save camera
+    $self->_camera_bb($bb);
+    
+    my ($x1, $y1, $x2, $y2) = ($bb->x_min, $bb->y_min, $bb->x_max, $bb->y_max);
+    if (($x2 - $x1)/($y2 - $y1) > $x/$y) {
+        # adjust Y
+        my $new_y = $y * ($x2 - $x1) / $x;
+        $y1 = ($y2 + $y1)/2 - $new_y/2;
+        $y2 = $y1 + $new_y;
+    } else {
+        my $new_x = $x * ($y2 - $y1) / $y;
+        $x1 = ($x2 + $x1)/2 - $new_x/2;
+        $x2 = $x1 + $new_x;
+    }
+    glOrtho($x1, $x2, $y1, $y2, 0, 1);
+    
+    glMatrixMode(GL_MODELVIEW);
 }
 
 sub line {
diff --git a/lib/Slic3r/GUI/Plater/3DPreview.pm b/lib/Slic3r/GUI/Plater/3DPreview.pm
index be9b5f572..596b5195f 100644
--- a/lib/Slic3r/GUI/Plater/3DPreview.pm
+++ b/lib/Slic3r/GUI/Plater/3DPreview.pm
@@ -116,6 +116,9 @@ sub load_print {
     }
     
     if ($self->IsShown) {
+        # load skirt and brim
+        $self->canvas->load_print_toolpaths($self->print);
+        
         foreach my $object (@{$self->print->objects}) {
             $self->canvas->load_print_object_toolpaths($object);
             
diff --git a/lib/Slic3r/GUI/Plater/ObjectCutDialog.pm b/lib/Slic3r/GUI/Plater/ObjectCutDialog.pm
index c0f942f12..6437be4b9 100644
--- a/lib/Slic3r/GUI/Plater/ObjectCutDialog.pm
+++ b/lib/Slic3r/GUI/Plater/ObjectCutDialog.pm
@@ -161,6 +161,7 @@ sub perform_cut {
         push @{$self->{new_model_objects}}, $lower_object;
         if ($self->{cut_options}{rotate_lower}) {
             $lower_object->rotate(PI, X);
+            $lower_object->center_around_origin;  # align to Z = 0
         }
     }
     
diff --git a/lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm b/lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm
index 9956134ce..fb36bca39 100644
--- a/lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm
+++ b/lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm
@@ -99,6 +99,7 @@ sub new {
     });
     EVT_TREE_SEL_CHANGED($self, $tree, sub {
         my ($self, $event) = @_;
+        return if $self->{disable_tree_sel_changed_event};
         $self->selection_changed;
     });
     EVT_BUTTON($self, $self->{btn_load_part}, sub { $self->on_btn_load(0) });
@@ -118,7 +119,14 @@ sub reload_tree {
     my $tree    = $self->{tree};
     my $rootId  = $tree->GetRootItem;
     
+    # despite wxWidgets states that DeleteChildren "will not generate any events unlike Delete() method",
+    # the MSW implementation of DeleteChildren actually calls Delete() for each item, so
+    # EVT_TREE_SEL_CHANGED is being called, with bad effects (the event handler is called; this 
+    # subroutine is never continued; an invisible EndModal is called on the dialog causing Plater
+    # to continue its logic and rescheduling the background process etc. GH #2774)
+    $self->{disable_tree_sel_changed_event} = 1;
     $tree->DeleteChildren($rootId);
+    $self->{disable_tree_sel_changed_event} = 0;
     
     my $selectedId = $rootId;
     foreach my $volume_id (0..$#{$object->volumes}) {
@@ -136,9 +144,13 @@ sub reload_tree {
     }
     $tree->ExpandAll;
     
-    # This will trigger the selection_changed() event
     Slic3r::GUI->CallAfter(sub {
         $self->{tree}->SelectItem($selectedId);
+        
+        # SelectItem() should trigger EVT_TREE_SEL_CHANGED as per wxWidgets docs,
+        # but in fact it doesn't if the given item is already selected (this happens
+        # on first load)
+        $self->selection_changed;
     });
 }
 
diff --git a/lib/Slic3r/GUI/Tab.pm b/lib/Slic3r/GUI/Tab.pm
index 7026ea9fb..8aeacc971 100644
--- a/lib/Slic3r/GUI/Tab.pm
+++ b/lib/Slic3r/GUI/Tab.pm
@@ -177,7 +177,7 @@ sub _update {}
 sub _on_presets_changed {
     my $self = shift;
     
-    $self->{on_presets_changed}->([$self->{presets_choice}->GetStrings], $self->{presets_choice}->GetSelection)
+    $self->{on_presets_changed}->($self->{presets}, $self->{presets_choice}->GetSelection)
         if $self->{on_presets_changed};
 }
 
@@ -360,10 +360,10 @@ sub load_presets {
     
     $self->current_preset(undef);
     $self->{presets_choice}->Clear;
-    $self->{presets_choice}->Append($_->{name}) for @{$self->{presets}};
+    $self->{presets_choice}->Append($_->name) for @{$self->{presets}};
     {
         # load last used preset
-        my $i = first { basename($self->{presets}[$_]{file}) eq ($Slic3r::GUI::Settings->{presets}{$self->name} || '') } 1 .. $#{$self->{presets}};
+        my $i = first { basename($self->{presets}[$_]->file) eq ($Slic3r::GUI::Settings->{presets}{$self->name} || '') } 1 .. $#{$self->{presets}};
         $self->select_preset($i || 0);
     }
     $self->_on_presets_changed;
@@ -813,7 +813,7 @@ sub build {
     my $self = shift;
     
     $self->init_config_options(qw(
-        filament_diameter extrusion_multiplier
+        filament_colour filament_diameter extrusion_multiplier
         temperature first_layer_temperature bed_temperature first_layer_bed_temperature
         fan_always_on cooling
         min_fan_speed max_fan_speed bridge_fan_speed disable_fan_first_layers
@@ -824,6 +824,7 @@ sub build {
         my $page = $self->add_options_page('Filament', 'spool.png');
         {
             my $optgroup = $page->new_optgroup('Filament');
+            $optgroup->append_single_option_line('filament_colour', 0);
             $optgroup->append_single_option_line('filament_diameter', 0);
             $optgroup->append_single_option_line('extrusion_multiplier', 0);
         }
diff --git a/lib/Slic3r/Geometry.pm b/lib/Slic3r/Geometry.pm
index 42fab2d89..1fa63f3b8 100644
--- a/lib/Slic3r/Geometry.pm
+++ b/lib/Slic3r/Geometry.pm
@@ -27,9 +27,6 @@ our @EXPORT_OK = qw(
 use constant PI => 4 * atan2(1, 1);
 use constant A => 0;
 use constant B => 1;
-use constant X => 0;
-use constant Y => 1;
-use constant Z => 2;
 use constant X1 => 0;
 use constant Y1 => 1;
 use constant X2 => 2;
@@ -605,119 +602,4 @@ sub douglas_peucker2 {
     return [ map $points->[$_], sort keys %keep ];
 }
 
-sub arrange {
-    my ($total_parts, $partx, $party, $dist, $bb) = @_;
-    
-    my $linint = sub {
-        my ($value, $oldmin, $oldmax, $newmin, $newmax) = @_;
-        return ($value - $oldmin) * ($newmax - $newmin) / ($oldmax - $oldmin) + $newmin;
-    };
-    
-    # use actual part size (the largest) plus separation distance (half on each side) in spacing algorithm
-    $partx += $dist;
-    $party += $dist;
-    
-    my ($areax, $areay);
-    if (defined $bb) {
-        my $size = $bb->size;
-        ($areax, $areay) = @$size[X,Y];
-    } else {
-        # bogus area size, large enough not to trigger the error below
-        $areax = $partx * $total_parts;
-        $areay = $party * $total_parts;
-    }
-    
-    # this is how many cells we have available into which to put parts
-    my $cellw = int(($areax + $dist) / $partx);
-    my $cellh = int(($areay + $dist) / $party);
-    
-    die "$total_parts parts won't fit in your print area!\n" if $total_parts > ($cellw * $cellh);
-    
-    # width and height of space used by cells
-    my $w = $cellw * $partx;
-    my $h = $cellh * $party;
-    
-    # left and right border positions of space used by cells
-    my $l = ($areax - $w) / 2;
-    my $r = $l + $w;
-    
-    # top and bottom border positions
-    my $t = ($areay - $h) / 2;
-    my $b = $t + $h;
-    
-    # list of cells, sorted by distance from center
-    my @cellsorder;
-    
-    # work out distance for all cells, sort into list
-    for my $i (0..$cellw-1) {
-        for my $j (0..$cellh-1) {
-            my $cx = $linint->($i + 0.5, 0, $cellw, $l, $r);
-            my $cy = $linint->($j + 0.5, 0, $cellh, $t, $b);
-            
-            my $xd = abs(($areax / 2) - $cx);
-            my $yd = abs(($areay / 2) - $cy);
-            
-            my $c = {
-                location => [$cx, $cy],
-                index => [$i, $j],
-                distance => $xd * $xd + $yd * $yd - abs(($cellw / 2) - ($i + 0.5)),
-            };
-            
-            BINARYINSERTIONSORT: {
-                my $index = $c->{distance};
-                my $low = 0;
-                my $high = @cellsorder;
-                while ($low < $high) {
-                    my $mid = ($low + (($high - $low) / 2)) | 0;
-                    my $midval = $cellsorder[$mid]->[0];
-                    
-                    if ($midval < $index) {
-                        $low = $mid + 1;
-                    } elsif ($midval > $index) {
-                        $high = $mid;
-                    } else {
-                        splice @cellsorder, $mid, 0, [$index, $c];
-                        last BINARYINSERTIONSORT;
-                    }
-                }
-                splice @cellsorder, $low, 0, [$index, $c];
-            }
-        }
-    }
-    
-    # the extents of cells actually used by objects
-    my ($lx, $ty, $rx, $by) = (0, 0, 0, 0);
-
-    # now find cells actually used by objects, map out the extents so we can position correctly
-    for my $i (1..$total_parts) {
-        my $c = $cellsorder[$i - 1];
-        my $cx = $c->[1]->{index}->[0];
-        my $cy = $c->[1]->{index}->[1];
-        if ($i == 1) {
-            $lx = $rx = $cx;
-            $ty = $by = $cy;
-        } else {
-            $rx = $cx if $cx > $rx;
-            $lx = $cx if $cx < $lx;
-            $by = $cy if $cy > $by;
-            $ty = $cy if $cy < $ty;
-        }
-    }
-    # now we actually place objects into cells, positioned such that the left and bottom borders are at 0
-    my @positions = ();
-    for (1..$total_parts) {
-        my $c = shift @cellsorder;
-        my $cx = $c->[1]->{index}->[0] - $lx;
-        my $cy = $c->[1]->{index}->[1] - $ty;
-
-        push @positions, [$cx * $partx, $cy * $party];
-    }
-    
-    if (defined $bb) {
-        $_->[X] += $bb->x_min for @positions;
-        $_->[Y] += $bb->y_min for @positions;
-    }
-    return @positions;
-}
-
 1;
diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index a3e72994e..2e65c147e 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -32,11 +32,6 @@ sub regions {
     return [ map $self->get_region($_), 0..($self->region_count-1) ];
 }
 
-sub merge_slices {
-    my ($self) = @_;
-    $_->merge_slices for @{$self->regions};
-}
-
 sub make_perimeters {
     my $self = shift;
     Slic3r::debugf "Making perimeters for layer %d\n", $self->id;
diff --git a/lib/Slic3r/Layer/PerimeterGenerator.pm b/lib/Slic3r/Layer/PerimeterGenerator.pm
index a5b737466..acb3bbba0 100644
--- a/lib/Slic3r/Layer/PerimeterGenerator.pm
+++ b/lib/Slic3r/Layer/PerimeterGenerator.pm
@@ -95,7 +95,7 @@ sub process {
         my $loop_number = $self->config->perimeters + ($surface->extra_perimeters || 0);
         $loop_number--;  # 0-indexed loops
         
-        my @gaps = ();   # ExPolygons
+        my @gaps = ();   # Polygons
         
         my @last = @{$surface->expolygon->simplify_p(&Slic3r::SCALED_RESOLUTION)};
         if ($loop_number >= 0) {  # no loops = -1
@@ -133,12 +133,12 @@ sub process {
                         
                         # the following offset2 ensures almost nothing in @thin_walls is narrower than $min_width
                         # (actually, something larger than that still may exist due to mitering or other causes)
-                        my $min_width = $pwidth / 4;
+                        my $min_width = $ext_pwidth / 4;
                         @thin_walls = @{offset2_ex($diff, -$min_width/2, +$min_width/2)};
-        
+                        
                         # the maximum thickness of our thin wall area is equal to the minimum thickness of a single loop
-                        @thin_walls = grep $_->length > $pwidth*2,
-                            map @{$_->medial_axis($pwidth + $pspacing, $min_width)}, @thin_walls;
+                        @thin_walls = grep $_->length > $ext_pwidth*2,
+                            map @{$_->medial_axis($ext_pwidth + $ext_pspacing, $min_width)}, @thin_walls;
                         Slic3r::debugf "  %d thin walls detected\n", scalar(@thin_walls) if $Slic3r::debug;
         
                         if (0) {
@@ -174,10 +174,10 @@ sub process {
                         # (but still long enough to escape the area threshold) that gap fill
                         # won't be able to fill but we'd still remove from infill area
                         my $diff = diff_ex(
-                            offset(\@last, -0.5*$pspacing),
-                            offset(\@offsets, +0.5*$pspacing + 10),  # safety offset
+                            offset(\@last, -0.5*$distance),
+                            offset(\@offsets, +0.5*$distance + 10),  # safety offset
                         );
-                        push @gaps, grep abs($_->area) >= $gap_area_threshold, @$diff;
+                        push @gaps, map $_->clone, map @$_, grep abs($_->area) >= $gap_area_threshold, @$diff;
                     }
                 }
             
@@ -278,20 +278,20 @@ sub process {
                 require "Slic3r/SVG.pm";
                 Slic3r::SVG::output(
                     "gaps.svg",
-                    expolygons => \@gaps,
+                    expolygons => union_ex(\@gaps),
                 );
             }
             
-            # where $pwidth < thickness < 2*$pspacing, infill with width = 1.5*$pwidth
-            # where 0.5*$pwidth < thickness < $pwidth, infill with width = 0.5*$pwidth
+            # where $pwidth < thickness < 2*$pspacing, infill with width = 2*$pwidth
+            # where 0.1*$pwidth < thickness < $pwidth, infill with width = 1*$pwidth
             my @gap_sizes = (
-                [ $pwidth, 2*$pspacing, unscale 1.5*$pwidth ],
-                [ 0.1*$pwidth, $pwidth, unscale 0.5*$pwidth ],
+                [ $pwidth, 2*$pspacing, unscale 2*$pwidth ],
+                [ 0.1*$pwidth, $pwidth, unscale 1*$pwidth ],
             );
             foreach my $gap_size (@gap_sizes) {
                 my @gap_fill = $self->_fill_gaps(@$gap_size, \@gaps);
                 $self->gap_fill->append($_) for @gap_fill;
-            
+                
                 # Make sure we don't infill narrow parts that are already gap-filled
                 # (we only consider this surface's gaps to reduce the diff() complexity).
                 # Growing actual extrusions ensures that gaps not filled by medial axis
@@ -304,6 +304,7 @@ sub process {
                         ->grow(scale $w/2)};
                 } @gap_fill;
                 @last = @{diff(\@last, \@filled)};
+                @gaps = @{diff(\@gaps, \@filled)};  # prevent more gap fill here
             }
         }
         
@@ -454,8 +455,8 @@ sub _fill_gaps {
     $min *= (1 - &Slic3r::INSET_OVERLAP_TOLERANCE);
     
     my $this = diff_ex(
-        offset2([ map @$_, @$gaps ], -$min/2, +$min/2),
-        offset2([ map @$_, @$gaps ], -$max/2, +$max/2),
+        offset2($gaps, -$min/2, +$min/2),
+        offset2($gaps, -$max/2, +$max/2),
         1,
     );
     
diff --git a/lib/Slic3r/Model.pm b/lib/Slic3r/Model.pm
index 1a2f62afd..162c3a3d1 100644
--- a/lib/Slic3r/Model.pm
+++ b/lib/Slic3r/Model.pm
@@ -150,15 +150,19 @@ sub duplicate {
 
 sub _arrange {
     my ($self, $sizes, $distance, $bb) = @_;
+
+    $bb //= Slic3r::Geometry::BoundingBoxf->new;
     
     # we supply unscaled data to arrange()
-    return Slic3r::Geometry::arrange(
+    return @{Slic3r::Geometry::arrange(
         scalar(@$sizes),                # number of parts
-        max(map $_->x, @$sizes),        # cell width
-        max(map $_->y, @$sizes),        # cell height ,
+        Slic3r::Pointf->new(
+            max(map $_->x, @$sizes),        # cell width
+            max(map $_->y, @$sizes),        # cell height  ,
+        ),
         $distance,                      # distance between cells
         $bb,                            # bounding box of the area to fill (can be undef)
-    );
+    )};
 }
 
 sub print_info {
@@ -262,37 +266,6 @@ sub add_instance {
     }
 }
 
-sub rotate {
-    my ($self, $angle, $axis) = @_;
-    
-    # we accept angle in radians but mesh currently uses degrees
-    $angle = rad2deg($angle);
-    
-    if ($axis == X) {
-        $_->mesh->rotate_x($angle) for @{$self->volumes};
-    } elsif ($axis == Y) {
-        $_->mesh->rotate_y($angle) for @{$self->volumes};
-    } elsif ($axis == Z) {
-        $_->mesh->rotate_z($angle) for @{$self->volumes};
-    }
-    $self->set_origin_translation(Slic3r::Pointf3->new(0,0,0));
-    $self->invalidate_bounding_box;
-}
-
-sub flip {
-    my ($self, $axis) = @_;
-    
-    if ($axis == X) {
-        $_->mesh->flip_x for @{$self->volumes};
-    } elsif ($axis == Y) {
-        $_->mesh->flip_y for @{$self->volumes};
-    } elsif ($axis == Z) {
-        $_->mesh->flip_z for @{$self->volumes};
-    }
-    $self->set_origin_translation(Slic3r::Pointf3->new(0,0,0));
-    $self->invalidate_bounding_box;
-}
-
 sub mesh_stats {
     my $self = shift;
     
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index 2837e0db7..77488e559 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -225,8 +225,8 @@ sub make_skirt {
     my $skirt_height_z = -1;
     foreach my $object (@{$self->objects}) {
         my $skirt_height = $self->has_infinite_skirt
-            ? scalar(@{$object->layers})
-            : min($self->config->skirt_height, scalar(@{$object->layers}));
+            ? $object->layer_count
+            : min($self->config->skirt_height, $object->layer_count);
         my $highest_layer = $object->get_layer($skirt_height - 1);
         $skirt_height_z = max($skirt_height_z, $highest_layer->print_z);
     }
@@ -432,6 +432,11 @@ sub expanded_output_filepath {
     $self->placeholder_parser->set(input_filename => $filename);
     $self->placeholder_parser->set(input_filename_base => $filename_base);
     
+    # set other variables from model object
+    $self->placeholder_parser->set_multiple(
+        scale => [ map $_->model_object->instances->[0]->scaling_factor * 100 . "%", @{$self->objects} ],
+    );
+    
     if ($path && -d $path) {
         # if output path is an existing directory, we take that and append
         # the specified filename format
diff --git a/lib/Slic3r/Print/GCode.pm b/lib/Slic3r/Print/GCode.pm
index d9246ebb4..d9534101f 100644
--- a/lib/Slic3r/Print/GCode.pm
+++ b/lib/Slic3r/Print/GCode.pm
@@ -196,6 +196,7 @@ sub export {
                 if ($finished_objects > 0) {
                     $gcodegen->set_origin(Slic3r::Pointf->new(map unscale $copy->[$_], X,Y));
                     $gcodegen->enable_cooling_markers(0);  # we're not filtering these moves through CoolingBuffer
+                    $gcodegen->avoid_crossing_perimeters->use_external_mp_once(1);
                     print $fh $gcodegen->retract;
                     print $fh $gcodegen->travel_to(
                         Slic3r::Point->new(0,0),
@@ -203,6 +204,9 @@ sub export {
                         'move to origin position for next object',
                     );
                     $gcodegen->enable_cooling_markers(1);
+                    
+                    # disable motion planner when traveling to first object point
+                    $gcodegen->avoid_crossing_perimeters->disable_once(1);
                 }
                 
                 my @layers = sort { $a->print_z <=> $b->print_z } @{$object->layers}, @{$object->support_layers};
@@ -305,8 +309,8 @@ sub process_layer {
             ($layer->id > 0 || $self->print->config->brim_width == 0)
                 && ($layer->id >= $self->print->config->skirt_height && !$self->print->has_infinite_skirt)
                 && !defined(first { $_->config->bottom_solid_layers > $layer->id } @{$layer->regions})
-                && !defined(first { @{$_->perimeters} > 1 } @{$layer->regions})
-                && !defined(first { @{$_->fills} > 0 } @{$layer->regions})
+                && !defined(first { $_->perimeters->items_count > 1 } @{$layer->regions})
+                && !defined(first { $_->fills->items_count > 0 } @{$layer->regions})
         );
     }
     
@@ -326,19 +330,20 @@ sub process_layer {
     
     # set new layer - this will change Z and force a retraction if retract_layer_change is enabled
     $gcode .= $self->_gcodegen->placeholder_parser->process($self->print->config->before_layer_gcode, {
-        layer_num => $layer->id,
+        layer_num => $self->_gcodegen->layer_index + 1,
         layer_z   => $layer->print_z,
     }) . "\n" if $self->print->config->before_layer_gcode;
-    $gcode .= $self->_gcodegen->change_layer($layer);
+    $gcode .= $self->_gcodegen->change_layer($layer);  # this will increase $self->_gcodegen->layer_index
     $gcode .= $self->_gcodegen->placeholder_parser->process($self->print->config->layer_gcode, {
-        layer_num => $layer->id,
+        layer_num => $self->_gcodegen->layer_index,
         layer_z   => $layer->print_z,
     }) . "\n" if $self->print->config->layer_gcode;
     
-    # extrude skirt
+    # extrude skirt along raft layers and normal object layers
+    # (not along interlaced support material layers)
     if (((values %{$self->_skirt_done}) < $self->print->config->skirt_height || $self->print->has_infinite_skirt)
         && !$self->_skirt_done->{$layer->print_z}
-        && !$layer->isa('Slic3r::Layer::Support')) {
+        && (!$layer->isa('Slic3r::Layer::Support') || $layer->id < $object->config->raft_layers)) {
         $self->_gcodegen->set_origin(Slic3r::Pointf->new(0,0));
         $self->_gcodegen->avoid_crossing_perimeters->use_external_mp(1);
         my @extruder_ids = map { $_->id } @{$self->_gcodegen->writer->extruders};
diff --git a/lib/Slic3r/Print/Object.pm b/lib/Slic3r/Print/Object.pm
index aa24eedf3..cbee4359b 100644
--- a/lib/Slic3r/Print/Object.pm
+++ b/lib/Slic3r/Print/Object.pm
@@ -57,16 +57,36 @@ sub slice {
             # plus the extra distance required by the support material logic
             my $first_layer_height = $self->config->get_value('first_layer_height');
             $print_z += $first_layer_height;
-            $print_z += $self->config->layer_height * ($self->config->raft_layers - 1);
+            
+            # use a large height
+            my $support_material_layer_height;
+            {
+                my @nozzle_diameters = (
+                    map $self->print->config->get_at('nozzle_diameter', $_),
+                        $self->config->support_material_extruder,
+                        $self->config->support_material_interface_extruder,
+                );
+                $support_material_layer_height = 0.75 * min(@nozzle_diameters);
+            }
+            $print_z += $support_material_layer_height * ($self->config->raft_layers - 1);
         
-            # at this stage we don't know which nozzles are actually used for the first layer
-            # so we compute the average of all of them
-            my $nozzle_diameter = sum(@{$self->print->config->nozzle_diameter})/@{$self->print->config->nozzle_diameter};
-            my $distance = $self->_support_material->contact_distance($first_layer_height, $nozzle_diameter);
+            # compute the average of all nozzles used for printing the object
+            my $nozzle_diameter;
+            {
+                my @nozzle_diameters = (
+                    map $self->print->config->get_at('nozzle_diameter', $_), @{$self->print->object_extruders}
+                );
+                $nozzle_diameter = sum(@nozzle_diameters)/@nozzle_diameters;
+            }
+            my $distance = $self->_support_material->contact_distance($self->config->layer_height, $nozzle_diameter);
         
             # force first layer print_z according to the contact distance
             # (the loop below will raise print_z by such height)
-            $first_object_layer_height = $nozzle_diameter;
+            if ($self->config->support_material_contact_distance == 0) {
+                $first_object_layer_height = $distance;
+            } else {
+                $first_object_layer_height = $nozzle_diameter;
+            }
             $first_object_layer_distance = $distance;
         }
     
diff --git a/slic3r.pl b/slic3r.pl
index ede37dbc0..a5957a98f 100755
--- a/slic3r.pl
+++ b/slic3r.pl
@@ -15,6 +15,7 @@ use POSIX qw(setlocale LC_NUMERIC);
 use Slic3r;
 use Time::HiRes qw(gettimeofday tv_interval);
 $|++;
+binmode STDOUT, ':utf8';
 
 our %opt = ();
 my %cli_options = ();
@@ -93,7 +94,7 @@ my $gui;
 if ((!@ARGV || $opt{gui}) && !$opt{save} && eval "require Slic3r::GUI; 1") {
     {
         no warnings 'once';
-        $Slic3r::GUI::datadir   = Slic3r::decode_path($opt{datadir});
+        $Slic3r::GUI::datadir   = Slic3r::decode_path($opt{datadir} // '');
         $Slic3r::GUI::no_plater = $opt{no_plater};
         $Slic3r::GUI::mode      = $opt{gui_mode};
         $Slic3r::GUI::autosave  = $opt{autosave};
@@ -103,6 +104,7 @@ if ((!@ARGV || $opt{gui}) && !$opt{save} && eval "require Slic3r::GUI; 1") {
     $gui->{mainframe}->load_config_file($_) for @{$opt{load}};
     $gui->{mainframe}->load_config($cli_config);
     foreach my $input_file (@ARGV) {
+        $input_file = Slic3r::decode_path($input_file);
         $gui->{mainframe}{plater}->load_file($input_file) unless $opt{no_plater};
     }
     $gui->MainLoop;
@@ -434,7 +436,7 @@ $j
                         Only retract before travel moves of this length in mm (default: $config->{retract_before_travel}[0])
     --retract-lift      Lift Z by the given distance in mm when retracting (default: $config->{retract_lift}[0])
     --retract-layer-change
-                        Enforce a retraction before each Z move (default: yes)
+                        Enforce a retraction before each Z move (default: no)
     --wipe              Wipe the nozzle while doing a retraction (default: no)
     
    Retraction options for multi-extruder setups:
diff --git a/t/custom_gcode.t b/t/custom_gcode.t
index 6423c394d..cbd5741f4 100644
--- a/t/custom_gcode.t
+++ b/t/custom_gcode.t
@@ -1,4 +1,4 @@
-use Test::More tests => 13;
+use Test::More tests => 15;
 use strict;
 use warnings;
 
@@ -7,6 +7,7 @@ BEGIN {
     use lib "$FindBin::Bin/../lib";
 }
 
+use List::Util qw(first);
 use Slic3r;
 use Slic3r::Test;
 
@@ -104,4 +105,29 @@ use Slic3r::Test;
     }
 }
 
+{
+    my $config = Slic3r::Config->new_from_defaults;
+    $config->set('before_layer_gcode', ';BEFORE [layer_num]');
+    $config->set('layer_gcode', ';CHANGE [layer_num]');
+    $config->set('support_material', 1);
+    $config->set('layer_height', 0.2);
+    my $print = Slic3r::Test::init_print('overhang', config => $config);
+    my $gcode = Slic3r::Test::gcode($print);
+    
+    my @before = ();
+    my @change = ();
+    foreach my $line (split /\R+/, $gcode) {
+        if ($line =~ /;BEFORE (\d+)/) {
+            push @before, $1;
+        } elsif ($line =~ /;CHANGE (\d+)/) {
+            push @change, $1;
+            fail 'inconsistent layer_num before and after layer change'
+                if $1 != $before[-1];
+        }
+    }
+    is_deeply \@before, \@change, 'layer_num is consistent before and after layer changes';
+    ok !defined(first { $change[$_] != $change[$_-1]+1 } 1..$#change),
+        'layer_num grows continously';  # i.e. no duplicates or regressions
+}
+
 __END__
diff --git a/t/gcode.t b/t/gcode.t
index 79ab1a7de..fb85ee5e4 100644
--- a/t/gcode.t
+++ b/t/gcode.t
@@ -1,4 +1,4 @@
-use Test::More tests => 22;
+use Test::More tests => 23;
 use strict;
 use warnings;
 
@@ -200,4 +200,21 @@ use Slic3r::Test;
     like $gcode, qr/START:20mm_cube/, '[input_filename] is also available in custom G-code';
 }
 
+{
+    my $config = Slic3r::Config->new_from_defaults;
+    $config->set('spiral_vase', 1);
+    my $print = Slic3r::Test::init_print('cube_with_hole', config => $config);
+    
+    my $spiral = 0;
+    Slic3r::GCode::Reader->new->parse(Slic3r::Test::gcode($print), sub {
+        my ($self, $cmd, $args, $info) = @_;
+        
+        if ($cmd eq 'G1' && exists $args->{E} && exists $args->{Z}) {
+            $spiral = 1;
+        }
+    });
+    
+    ok !$spiral, 'spiral vase is correctly disabled on layers with multiple loops';
+}
+
 __END__
diff --git a/t/support.t b/t/support.t
index 2091b4432..3eba6e64b 100644
--- a/t/support.t
+++ b/t/support.t
@@ -1,4 +1,4 @@
-use Test::More tests => 25;
+use Test::More tests => 27;
 use strict;
 use warnings;
 
@@ -221,12 +221,41 @@ use Slic3r::Test;
 
 {
     my $config = Slic3r::Config->new_from_defaults;
-    $config->set('raft_layers', 3);
+    $config->set('skirts', 0);
+    $config->set('start_gcode', '');
+    $config->set('raft_layers', 8);
     $config->set('nozzle_diameter', [0.4, 1]);
+    $config->set('layer_height', 0.1);
     $config->set('first_layer_height', 0.8);
     $config->set('support_material_extruder', 2);
+    $config->set('support_material_interface_extruder', 2);
+    $config->set('support_material_contact_distance', 0);
     my $print = Slic3r::Test::init_print('20mm_cube', config => $config);
-    ok Slic3r::Test::gcode($print), 'first_layer_height is validated with support material extruder nozzle diameter when using raft layers';
+    ok my $gcode = Slic3r::Test::gcode($print), 'first_layer_height is validated with support material extruder nozzle diameter when using raft layers';
+    
+    my $tool = undef;
+    my @z = (0);
+    my %layer_heights_by_tool = ();  # tool => [ lh, lh... ]
+    Slic3r::GCode::Reader->new->parse($gcode, sub {
+        my ($self, $cmd, $args, $info) = @_;
+    
+        if ($cmd =~ /^T(\d+)/) {
+            $tool = $1;
+        } elsif ($cmd eq 'G1' && exists $args->{Z} && $args->{Z} != $self->Z) {
+            push @z, $args->{Z};
+        } elsif ($info->{extruding} && $info->{dist_XY} > 0) {
+            $layer_heights_by_tool{$tool} ||= [];
+            push @{ $layer_heights_by_tool{$tool} }, $z[-1] - $z[-2];
+        }
+    });
+    
+    ok !defined(first { $_ > $config->nozzle_diameter->[0] + epsilon }
+        @{ $layer_heights_by_tool{$config->perimeter_extruder-1} }),
+        'no object layer is thicker than nozzle diameter';
+    
+    ok !defined(first { abs($_ - $config->layer_height) < epsilon }
+        @{ $layer_heights_by_tool{$config->support_material_extruder-1} }),
+        'no support material layer is as thin as object layers';
 }
 
 __END__
diff --git a/t/thin.t b/t/thin.t
index 49a6ef427..0b3843a10 100644
--- a/t/thin.t
+++ b/t/thin.t
@@ -1,4 +1,4 @@
-use Test::More tests => 14;
+use Test::More tests => 21;
 use strict;
 use warnings;
 
@@ -133,4 +133,40 @@ if (0) {
     ok sum(map $_->length, @$polylines) > $perimeter/2/4*3, 'medial axis has a reasonable length';
 }
 
+{
+    my $expolygon = Slic3r::ExPolygon->new(Slic3r::Polygon->new_scale(
+        [50, 100],
+        [300, 102],
+        [50, 104],
+    ));
+    my $res = $expolygon->medial_axis(scale 4, scale 0.5);
+    is scalar(@$res), 1, 'medial axis of a narrow triangle is a single line';
+    ok unscale($res->[0]->length) >= (200-100 - (120-100)) - epsilon, 'medial axis has reasonable length';
+}
+
+{
+    # GH #2474
+    my $expolygon = Slic3r::ExPolygon->new(Slic3r::Polygon->new(
+        [91294454,31032190],[11294481,31032190],[11294481,29967810],[44969182,29967810],[89909960,29967808],[91294454,29967808]
+    ));
+    my $polylines = $expolygon->medial_axis(1871238, 500000);
+    
+    is scalar(@$polylines), 1, 'medial axis is a single polyline';
+    my $polyline = $polylines->[0];
+    
+    my $expected_y = $expolygon->bounding_box->center->y; #;;
+    ok abs(sum(map $_->y, @$polyline) / @$polyline - $expected_y) < scaled_epsilon, #,,
+        'medial axis is horizontal and is centered';
+    
+    # order polyline from left to right
+    $polyline->reverse if $polyline->first_point->x > $polyline->last_point->x;
+    
+    my $polyline_bb = $polyline->bounding_box;
+    is $polyline->first_point->x, $polyline_bb->x_min, 'expected x_min';
+    is $polyline->last_point->x,  $polyline_bb->x_max, 'expected x_max';
+    
+    is_deeply [ map $_->x, @$polyline ], [ sort map $_->x, @$polyline ],
+        'medial axis is not self-overlapping';
+}
+
 __END__
diff --git a/utils/view-toolpaths.pl b/utils/view-toolpaths.pl
index 7e1d305bc..4bbbaab4c 100755
--- a/utils/view-toolpaths.pl
+++ b/utils/view-toolpaths.pl
@@ -33,7 +33,6 @@ my %opt = ();
     
     # load config
     my $config = Slic3r::Config->new_from_defaults;
-    $config->set('skirts', 0);
     if ($opt{load}) {
         $config->apply(Slic3r::Config->load($opt{load}));
     }
@@ -84,6 +83,7 @@ sub OnInit {
     if ($d3) {
         $canvas = Slic3r::GUI::3DScene->new($panel);
         $canvas->set_bed_shape($print->config->bed_shape);
+        $canvas->load_print_toolpaths($print);
         
         foreach my $object (@{$print->objects}) {
             #$canvas->load_print_object_slices($object);
diff --git a/var/application_view_tile.png b/var/application_view_tile.png
new file mode 100755
index 000000000..3bc0bd32f
Binary files /dev/null and b/var/application_view_tile.png differ
diff --git a/var/lorry_add.png b/var/lorry_add.png
new file mode 100755
index 000000000..a2c512499
Binary files /dev/null and b/var/lorry_add.png differ
diff --git a/var/lorry_go.png b/var/lorry_go.png
new file mode 100755
index 000000000..1c296a6aa
Binary files /dev/null and b/var/lorry_go.png differ
diff --git a/var/plugin_add.png b/var/plugin_add.png
new file mode 100755
index 000000000..ae43690ec
Binary files /dev/null and b/var/plugin_add.png differ
diff --git a/var/plugin_go.png b/var/plugin_go.png
new file mode 100755
index 000000000..41da9913d
Binary files /dev/null and b/var/plugin_go.png differ
diff --git a/var/shape_flip_horizontal.png b/var/shape_flip_horizontal.png
new file mode 100755
index 000000000..8667c81f8
Binary files /dev/null and b/var/shape_flip_horizontal.png differ
diff --git a/var/shape_handles.png b/var/shape_handles.png
new file mode 100755
index 000000000..ce27fe3a0
Binary files /dev/null and b/var/shape_handles.png differ
diff --git a/var/textfield.png b/var/textfield.png
new file mode 100755
index 000000000..d37e7304e
Binary files /dev/null and b/var/textfield.png differ
diff --git a/xs/src/libslic3r/Config.hpp b/xs/src/libslic3r/Config.hpp
index 313b524fa..49e999bc0 100644
--- a/xs/src/libslic3r/Config.hpp
+++ b/xs/src/libslic3r/Config.hpp
@@ -26,8 +26,14 @@ class ConfigOption {
     virtual void setInt(int val) {};
 };
 
+class ConfigOptionVectorBase : public ConfigOption {
+    public:
+    virtual ~ConfigOptionVectorBase() {};
+    virtual std::vector<std::string> vserialize() const = 0;
+};
+
 template <class T>
-class ConfigOptionVector
+class ConfigOptionVector : public ConfigOptionVectorBase
 {
     public:
     virtual ~ConfigOptionVector() {};
@@ -63,7 +69,7 @@ class ConfigOptionFloat : public ConfigOption
     };
 };
 
-class ConfigOptionFloats : public ConfigOption, public ConfigOptionVector<double>
+class ConfigOptionFloats : public ConfigOptionVector<double>
 {
     public:
     
@@ -76,6 +82,16 @@ class ConfigOptionFloats : public ConfigOption, public ConfigOptionVector<double
         return ss.str();
     };
     
+    std::vector<std::string> vserialize() const {
+        std::vector<std::string> vv;
+        for (std::vector<double>::const_iterator it = this->values.begin(); it != this->values.end(); ++it) {
+            std::ostringstream ss;
+            ss << *it;
+            vv.push_back(ss.str());
+        }
+        return vv;
+    };
+    
     bool deserialize(std::string str) {
         this->values.clear();
         std::istringstream is(str);
@@ -112,7 +128,7 @@ class ConfigOptionInt : public ConfigOption
     };
 };
 
-class ConfigOptionInts : public ConfigOption, public ConfigOptionVector<int>
+class ConfigOptionInts : public ConfigOptionVector<int>
 {
     public:
     
@@ -125,6 +141,16 @@ class ConfigOptionInts : public ConfigOption, public ConfigOptionVector<int>
         return ss.str();
     };
     
+    std::vector<std::string> vserialize() const {
+        std::vector<std::string> vv;
+        for (std::vector<int>::const_iterator it = this->values.begin(); it != this->values.end(); ++it) {
+            std::ostringstream ss;
+            ss << *it;
+            vv.push_back(ss.str());
+        }
+        return vv;
+    };
+    
     bool deserialize(std::string str) {
         this->values.clear();
         std::istringstream is(str);
@@ -174,7 +200,7 @@ class ConfigOptionString : public ConfigOption
 };
 
 // semicolon-separated strings
-class ConfigOptionStrings : public ConfigOption, public ConfigOptionVector<std::string>
+class ConfigOptionStrings : public ConfigOptionVector<std::string>
 {
     public:
     
@@ -187,6 +213,10 @@ class ConfigOptionStrings : public ConfigOption, public ConfigOptionVector<std::
         return ss.str();
     };
     
+    std::vector<std::string> vserialize() const {
+        return this->values;
+    };
+    
     bool deserialize(std::string str) {
         this->values.clear();
         std::istringstream is(str);
@@ -279,7 +309,7 @@ class ConfigOptionPoint : public ConfigOption
     };
 };
 
-class ConfigOptionPoints : public ConfigOption, public ConfigOptionVector<Pointf>
+class ConfigOptionPoints : public ConfigOptionVector<Pointf>
 {
     public:
     
@@ -294,6 +324,16 @@ class ConfigOptionPoints : public ConfigOption, public ConfigOptionVector<Pointf
         return ss.str();
     };
     
+    std::vector<std::string> vserialize() const {
+        std::vector<std::string> vv;
+        for (Pointfs::const_iterator it = this->values.begin(); it != this->values.end(); ++it) {
+            std::ostringstream ss;
+            ss << *it;
+            vv.push_back(ss.str());
+        }
+        return vv;
+    };
+    
     bool deserialize(std::string str) {
         this->values.clear();
         std::istringstream is(str);
@@ -332,7 +372,7 @@ class ConfigOptionBool : public ConfigOption
     };
 };
 
-class ConfigOptionBools : public ConfigOption, public ConfigOptionVector<bool>
+class ConfigOptionBools : public ConfigOptionVector<bool>
 {
     public:
     
@@ -345,6 +385,16 @@ class ConfigOptionBools : public ConfigOption, public ConfigOptionVector<bool>
         return ss.str();
     };
     
+    std::vector<std::string> vserialize() const {
+        std::vector<std::string> vv;
+        for (std::vector<bool>::const_iterator it = this->values.begin(); it != this->values.end(); ++it) {
+            std::ostringstream ss;
+            ss << (*it ? "1" : "0");
+            vv.push_back(ss.str());
+        }
+        return vv;
+    };
+    
     bool deserialize(std::string str) {
         this->values.clear();
         std::istringstream is(str);
diff --git a/xs/src/libslic3r/ExPolygon.cpp b/xs/src/libslic3r/ExPolygon.cpp
index a03447bba..53a1e9333 100644
--- a/xs/src/libslic3r/ExPolygon.cpp
+++ b/xs/src/libslic3r/ExPolygon.cpp
@@ -191,12 +191,25 @@ ExPolygon::medial_axis(double max_width, double min_width, Polylines* polylines)
     // unless they represent closed loops
     for (Polylines::iterator polyline = polylines->begin(); polyline != polylines->end(); ++polyline) {
         if (polyline->points.front().distance_to(polyline->points.back()) < min_width) continue;
+        // TODO: we should *not* extend endpoints where other polylines start/end
+        // (such as T joints, which are returned as three polylines by MedialAxis)
         polyline->extend_start(max_width);
         polyline->extend_end(max_width);
     }
     
     // clip again after extending endpoints to prevent them from exceeding the expolygon boundaries
     intersection(*polylines, *this, polylines);
+    
+    // remove too short polylines
+    // (we can't do this check before endpoints extension and clipping because we don't
+    // know how long will the endpoints be extended since it depends on polygon thickness
+    // which is variable - extension will be <= max_width/2 on each side)
+    for (size_t i = 0; i < polylines->size(); ++i) {
+        if ((*polylines)[i].length() < max_width) {
+            polylines->erase(polylines->begin() + i);
+            --i;
+        }
+    }
 }
 
 void
diff --git a/xs/src/libslic3r/ExtrusionEntity.hpp b/xs/src/libslic3r/ExtrusionEntity.hpp
index 323d935a1..b5262eae0 100644
--- a/xs/src/libslic3r/ExtrusionEntity.hpp
+++ b/xs/src/libslic3r/ExtrusionEntity.hpp
@@ -35,9 +35,15 @@ enum ExtrusionLoopRole {
 class ExtrusionEntity
 {
     public:
+    virtual bool is_collection() const {
+        return false;
+    };
     virtual bool is_loop() const {
         return false;
     };
+    virtual bool can_reverse() const {
+        return true;
+    };
     virtual ExtrusionEntity* clone() const = 0;
     virtual ~ExtrusionEntity() {};
     virtual void reverse() = 0;
@@ -92,6 +98,9 @@ class ExtrusionLoop : public ExtrusionEntity
     bool is_loop() const {
         return true;
     };
+    bool can_reverse() const {
+        return false;
+    };
     ExtrusionLoop* clone() const;
     bool make_clockwise();
     bool make_counter_clockwise();
diff --git a/xs/src/libslic3r/ExtrusionEntityCollection.cpp b/xs/src/libslic3r/ExtrusionEntityCollection.cpp
index 4ceef0387..075429d9d 100644
--- a/xs/src/libslic3r/ExtrusionEntityCollection.cpp
+++ b/xs/src/libslic3r/ExtrusionEntityCollection.cpp
@@ -86,7 +86,7 @@ ExtrusionEntityCollection::chained_path_from(Point start_near, ExtrusionEntityCo
     Points endpoints;
     for (ExtrusionEntitiesPtr::iterator it = my_paths.begin(); it != my_paths.end(); ++it) {
         endpoints.push_back((*it)->first_point());
-        if (no_reverse) {
+        if (no_reverse || !(*it)->can_reverse()) {
             endpoints.push_back((*it)->first_point());
         } else {
             endpoints.push_back((*it)->last_point());
@@ -99,7 +99,7 @@ ExtrusionEntityCollection::chained_path_from(Point start_near, ExtrusionEntityCo
         int path_index = start_index/2;
         ExtrusionEntity* entity = my_paths.at(path_index);
         // never reverse loops, since it's pointless for chained path and callers might depend on orientation
-        if (start_index % 2 && !no_reverse && !entity->is_loop()) {
+        if (start_index % 2 && !no_reverse && entity->can_reverse()) {
             entity->reverse();
         }
         retval->entities.push_back(my_paths.at(path_index));
@@ -121,6 +121,22 @@ ExtrusionEntityCollection::grow() const
     return pp;
 }
 
+/* Recursively count paths and loops contained in this collection */
+size_t
+ExtrusionEntityCollection::items_count() const
+{
+    size_t count = 0;
+    for (ExtrusionEntitiesPtr::const_iterator it = this->entities.begin(); it != this->entities.end(); ++it) {
+        if ((*it)->is_collection()) {
+            ExtrusionEntityCollection* collection = dynamic_cast<ExtrusionEntityCollection*>(*it);
+            count += collection->items_count();
+        } else {
+            ++count;
+        }
+    }
+    return count;
+}
+
 #ifdef SLIC3RXS
 // there is no ExtrusionLoop::Collection or ExtrusionEntity::Collection
 REGISTER_CLASS(ExtrusionEntityCollection, "ExtrusionPath::Collection");
diff --git a/xs/src/libslic3r/ExtrusionEntityCollection.hpp b/xs/src/libslic3r/ExtrusionEntityCollection.hpp
index be557bb5f..18e15e318 100644
--- a/xs/src/libslic3r/ExtrusionEntityCollection.hpp
+++ b/xs/src/libslic3r/ExtrusionEntityCollection.hpp
@@ -16,6 +16,12 @@ class ExtrusionEntityCollection : public ExtrusionEntity
     ExtrusionEntityCollection(): no_sort(false) {};
     ExtrusionEntityCollection(const ExtrusionEntityCollection &collection);
     ExtrusionEntityCollection& operator= (const ExtrusionEntityCollection &other);
+    bool is_collection() const {
+        return true;
+    };
+    bool can_reverse() const {
+        return !this->no_sort;
+    };
     void swap (ExtrusionEntityCollection &c);
     void chained_path(ExtrusionEntityCollection* retval, bool no_reverse = false, std::vector<size_t>* orig_indices = NULL) const;
     void chained_path_from(Point start_near, ExtrusionEntityCollection* retval, bool no_reverse = false, std::vector<size_t>* orig_indices = NULL) const;
@@ -23,6 +29,7 @@ class ExtrusionEntityCollection : public ExtrusionEntity
     Point first_point() const;
     Point last_point() const;
     Polygons grow() const;
+    size_t items_count() const;
 };
 
 }
diff --git a/xs/src/libslic3r/Geometry.cpp b/xs/src/libslic3r/Geometry.cpp
index 3dc11c0cb..5a7b2e3dc 100644
--- a/xs/src/libslic3r/Geometry.cpp
+++ b/xs/src/libslic3r/Geometry.cpp
@@ -161,6 +161,133 @@ simplify_polygons(const Polygons &polygons, double tolerance, Polygons* retval)
     Slic3r::simplify_polygons(pp, retval);
 }
 
+double
+linint(double value, double oldmin, double oldmax, double newmin, double newmax)
+{
+    return (value - oldmin) * (newmax - newmin) / (oldmax - oldmin) + newmin;
+}
+
+Pointfs
+arrange(size_t total_parts, Pointf part, coordf_t dist, const BoundingBoxf &bb)
+{
+    // use actual part size (the largest) plus separation distance (half on each side) in spacing algorithm
+    part.x += dist;
+    part.y += dist;
+    
+    Pointf area;
+    if (bb.defined) {
+        area = bb.size();
+    } else {
+        // bogus area size, large enough not to trigger the error below
+        area.x = part.x * total_parts;
+        area.y = part.y * total_parts;
+    }
+    
+    // this is how many cells we have available into which to put parts
+    size_t cellw = floor((area.x + dist) / part.x);
+    size_t cellh = floor((area.x + dist) / part.x);
+    
+    if (total_parts > (cellw * cellh))
+        CONFESS("%zu parts won't fit in your print area!\n", total_parts);
+    
+    // total space used by cells
+    Pointf cells(cellw * part.x, cellh * part.y);
+    
+    // bounding box of total space used by cells
+    BoundingBoxf cells_bb;
+    cells_bb.merge(Pointf(0,0)); // min
+    cells_bb.merge(cells);  // max
+    
+    // center bounding box to area
+    cells_bb.translate(
+        -(area.x - cells.x) / 2,
+        -(area.y - cells.y) / 2
+    );
+    
+    // list of cells, sorted by distance from center
+    std::vector<ArrangeItemIndex> cellsorder;
+    
+    // work out distance for all cells, sort into list
+    for (size_t i = 0; i <= cellw-1; ++i) {
+        for (size_t j = 0; j <= cellh-1; ++j) {
+            coordf_t cx = linint(i + 0.5, 0, cellw, cells_bb.min.x, cells_bb.max.x);
+            coordf_t cy = linint(j + 0.5, 0, cellh, cells_bb.max.y, cells_bb.min.y);
+            
+            coordf_t xd = fabs((area.x / 2) - cx);
+            coordf_t yd = fabs((area.y / 2) - cy);
+            
+            ArrangeItem c;
+            c.pos.x = cx;
+            c.pos.y = cy;
+            c.index_x = i;
+            c.index_y = j;
+            c.dist = xd * xd + yd * yd - fabs((cellw / 2) - (i + 0.5));
+            
+            // binary insertion sort
+            {
+                coordf_t index = c.dist;
+                size_t low = 0;
+                size_t high = cellsorder.size();
+                while (low < high) {
+                    size_t mid = (low + ((high - low) / 2)) | 0;
+                    coordf_t midval = cellsorder[mid].index;
+                    
+                    if (midval < index) {
+                        low = mid + 1;
+                    } else if (midval > index) {
+                        high = mid;
+                    } else {
+                        cellsorder.insert(cellsorder.begin() + mid, ArrangeItemIndex(index, c));
+                        goto ENDSORT;
+                    }
+                }
+                cellsorder.insert(cellsorder.begin() + low, ArrangeItemIndex(index, c));
+            }
+            ENDSORT: true;
+        }
+    }
+    
+    // the extents of cells actually used by objects
+    coordf_t lx = 0;
+    coordf_t ty = 0;
+    coordf_t rx = 0;
+    coordf_t by = 0;
+
+    // now find cells actually used by objects, map out the extents so we can position correctly
+    for (size_t i = 1; i <= total_parts; ++i) {
+        ArrangeItemIndex c = cellsorder[i - 1];
+        coordf_t cx = c.item.index_x;
+        coordf_t cy = c.item.index_y;
+        if (i == 1) {
+            lx = rx = cx;
+            ty = by = cy;
+        } else {
+            if (cx > rx) rx = cx;
+            if (cx < lx) lx = cx;
+            if (cy > by) by = cy;
+            if (cy < ty) ty = cy;
+        }
+    }
+    // now we actually place objects into cells, positioned such that the left and bottom borders are at 0
+    Pointfs positions;
+    for (size_t i = 1; i <= total_parts; ++i) {
+        ArrangeItemIndex c = cellsorder.front();
+        cellsorder.erase(cellsorder.begin());
+        coordf_t cx = c.item.index_x - lx;
+        coordf_t cy = c.item.index_y - ty;
+        
+        positions.push_back(Pointf(cx * part.x, cy * part.y));
+    }
+    
+    if (bb.defined) {
+        for (Pointfs::iterator p = positions.begin(); p != positions.end(); ++p) {
+            p->x += bb.min.x;
+            p->y += bb.min.y;
+        }
+    }
+    return positions;
+}
+
 Line
 MedialAxis::edge_to_line(const VD::edge_type &edge) const
 {
@@ -198,8 +325,11 @@ MedialAxis::build(Polylines* polylines)
     }
     */
     
+    typedef const VD::vertex_type vert_t;
+    typedef const VD::edge_type   edge_t;
+    
     // collect valid edges (i.e. prune those not belonging to MAT)
-    // note: this keeps twins, so it contains twice the number of the valid edges
+    // note: this keeps twins, so it inserts twice the number of the valid edges
     this->edges.clear();
     for (VD::const_edge_iterator edge = this->vd.edges().begin(); edge != this->vd.edges().end(); ++edge) {
         // if we only process segments representing closed loops, none if the
@@ -209,61 +339,64 @@ MedialAxis::build(Polylines* polylines)
     }
     
     // count valid segments for each vertex
-    std::map< const VD::vertex_type*,std::set<const VD::edge_type*> > vertex_edges;
-    std::set<const VD::vertex_type*> entry_nodes;
-    for (VD::const_vertex_iterator vertex = this->vd.vertices().begin(); vertex != this->vd.vertices().end(); ++vertex) {
-        // get a reference to the list of valid edges originating from this vertex
-        std::set<const VD::edge_type*>& edges = vertex_edges[&*vertex];
+    std::map< vert_t*,std::set<edge_t*> > vertex_edges;  // collects edges connected for each vertex
+    std::set<vert_t*> startpoints;                       // collects all vertices having a single starting edge
+    for (VD::const_vertex_iterator it = this->vd.vertices().begin(); it != this->vd.vertices().end(); ++it) {
+        vert_t* vertex = &*it;
         
-        // get one random edge originating from this vertex
-        const VD::edge_type* edge = vertex->incident_edge();
+        // loop through all edges originating from this vertex
+        // starting from a random one
+        edge_t* edge = vertex->incident_edge();
         do {
-            if (this->edges.count(edge) > 0)    // only count valid edges
-                edges.insert(edge);
-            edge = edge->rot_next();            // next edge originating from this vertex
+            // if this edge was not pruned by our filter above,
+            // add it to vertex_edges
+            if (this->edges.count(edge) > 0)
+                vertex_edges[vertex].insert(edge);
+            
+            // continue looping next edge originating from this vertex
+            edge = edge->rot_next();
         } while (edge != vertex->incident_edge());
         
-        // if there's only one edge starting at this vertex then it's a leaf
-        size_t edge_count = edges.size();
-        if (edge_count == 1) {
-            entry_nodes.insert(&*vertex);
+        // if there's only one edge starting at this vertex then it's an endpoint
+        if (vertex_edges[vertex].size() == 1) {
+            startpoints.insert(vertex);
         }
     }
     
-    // prune recursively
-    while (!entry_nodes.empty()) {
+    // prune startpoints recursively if extreme segments are not valid
+    while (!startpoints.empty()) {
         // get a random entry node
-        const VD::vertex_type* v = *entry_nodes.begin();
+        vert_t* v = *startpoints.begin();
     
         // get edge starting from v
-        assert(!vertex_edges[v].empty());
-        const VD::edge_type* edge = *vertex_edges[v].begin();
+        assert(vertex_edges[v].size() == 1);
+        edge_t* edge = *vertex_edges[v].begin();
         
         if (!this->is_valid_edge(*edge)) {
-            // if edge is not valid, erase it from edge list
+            // if edge is not valid, erase it and its twin from edge list
             (void)this->edges.erase(edge);
             (void)this->edges.erase(edge->twin());
             
             // decrement edge counters for the affected nodes
-            const VD::vertex_type* v1 = edge->vertex1();
+            vert_t* v1 = edge->vertex1();
             (void)vertex_edges[v].erase(edge);
             (void)vertex_edges[v1].erase(edge->twin());
             
             // also, check whether the end vertex is a new leaf
             if (vertex_edges[v1].size() == 1) {
-                entry_nodes.insert(v1);
+                startpoints.insert(v1);
             } else if (vertex_edges[v1].empty()) {
-                entry_nodes.erase(v1);
+                startpoints.erase(v1);
             }
         }
         
         // remove node from the set to prevent it from being visited again
-        entry_nodes.erase(v);
+        startpoints.erase(v);
     }
     
     // iterate through the valid edges to build polylines
     while (!this->edges.empty()) {
-        const VD::edge_type& edge = **this->edges.begin();
+        edge_t &edge = **this->edges.begin();
         
         // start a polyline
         Polyline polyline;
@@ -278,13 +411,14 @@ MedialAxis::build(Polylines* polylines)
         this->process_edge_neighbors(edge, &polyline.points);
         
         // get previous points
-        Points pp;
-        this->process_edge_neighbors(*edge.twin(), &pp);
-        polyline.points.insert(polyline.points.begin(), pp.rbegin(), pp.rend());
+        {
+            Points pp;
+            this->process_edge_neighbors(*edge.twin(), &pp);
+            polyline.points.insert(polyline.points.begin(), pp.rbegin(), pp.rend());
+        }
         
-        // append polyline to result if it's not too small
-        if (polyline.length() > this->max_width)
-            polylines->push_back(polyline);
+        // append polyline to result
+        polylines->push_back(polyline);
     }
 }
 
@@ -322,69 +456,59 @@ MedialAxis::is_valid_edge(const VD::edge_type& edge) const
        "thin" nature of our input, these edges will be very short and not part of
        our wanted output. */
     
+    // retrieve the original line segments which generated the edge we're checking
     const VD::cell_type &cell1 = *edge.cell();
     const VD::cell_type &cell2 = *edge.twin()->cell();
-    if (cell1.contains_segment() && cell2.contains_segment()) {
-        Line segment1 = this->retrieve_segment(cell1);
-        Line segment2 = this->retrieve_segment(cell2);
-        if (segment1.a == segment2.b || segment1.b == segment2.a) return false;
-        
-        // calculate relative angle between the two boundary segments
-        double angle = fabs(segment2.orientation() - segment1.orientation());
-        
-        // fabs(angle) ranges from 0 (collinear, same direction) to PI (collinear, opposite direction)
-        // we're interested only in segments close to the second case (facing segments)
-        // so we allow some tolerance (say, 30°)
-        if (angle < PI*2/3 ) {
-            return false;
-        }
-        
-        // each vertex is equidistant to both cell segments
-        // but such distance might differ between the two vertices;
-        // in this case it means the shape is getting narrow (like a corner)
-        // and we might need to skip the edge since it's not really part of
-        // our skeleton
-        Point v0( edge.vertex0()->x(), edge.vertex0()->y() );
-        Point v1( edge.vertex1()->x(), edge.vertex1()->y() );
-        double dist0 = v0.perp_distance_to(segment1);
-        double dist1 = v1.perp_distance_to(segment1);
-        
-        /*
-        double diff = fabs(dist1 - dist0);
-        double dist_between_segments1 = segment1.a.distance_to(segment2);
-        double dist_between_segments2 = segment1.b.distance_to(segment2);
-        printf("w = %f/%f, dist0 = %f, dist1 = %f, diff = %f, seg1len = %f, seg2len = %f, edgelen = %f, s2s = %f / %f\n",
-            unscale(this->max_width), unscale(this->min_width),
-            unscale(dist0), unscale(dist1), unscale(diff),
-            unscale(segment1.length()), unscale(segment2.length()),
-            unscale(this->edge_to_line(edge).length()),
-            unscale(dist_between_segments1), unscale(dist_between_segments2)
-            );
-        */
-        
-        // if this segment is the centerline for a very thin area, we might want to skip it
-        // in case the area is too thin
-        if (dist0 < this->min_width/2 || dist1 < this->min_width/2) {
-            //printf(" => too thin, skipping\n");
-            return false;
-        }
-        
-        /*
-        // if distance between this edge and the thin area boundary is greater
-        // than half the max width, then it's not a true medial axis segment
-        if (dist1 > this->width*2) {
-            printf(" => too fat, skipping\n");
-            //return false;
-        }
-        */
-        
-        return true;
+    if (!cell1.contains_segment() || !cell2.contains_segment()) return false;
+    const Line &segment1 = this->retrieve_segment(cell1);
+    const Line &segment2 = this->retrieve_segment(cell2);
+    
+    // calculate the relative angle between the two boundary segments
+    double angle = fabs(segment2.orientation() - segment1.orientation());
+    
+    // fabs(angle) ranges from 0 (collinear, same direction) to PI (collinear, opposite direction)
+    // we're interested only in segments close to the second case (facing segments)
+    // so we allow some tolerance.
+    // this filter ensures that we're dealing with a narrow/oriented area (longer than thick)
+    if (fabs(angle - PI) > PI/5) {
+        return false;
     }
     
-    return false;
+    // each edge vertex is equidistant to both cell segments
+    // but such distance might differ between the two vertices;
+    // in this case it means the shape is getting narrow (like a corner)
+    // and we might need to skip the edge since it's not really part of
+    // our skeleton
+    
+    // get perpendicular distance of each edge vertex to the segment(s)
+    double dist0 = segment1.a.distance_to(segment2.b);
+    double dist1 = segment1.b.distance_to(segment2.a);
+    
+    /*
+    Line line = this->edge_to_line(edge);
+    double diff = fabs(dist1 - dist0);
+    double dist_between_segments1 = segment1.a.distance_to(segment2);
+    double dist_between_segments2 = segment1.b.distance_to(segment2);
+    printf("w = %f/%f, dist0 = %f, dist1 = %f, diff = %f, seg1len = %f, seg2len = %f, edgelen = %f, s2s = %f / %f\n",
+        unscale(this->max_width), unscale(this->min_width),
+        unscale(dist0), unscale(dist1), unscale(diff),
+        unscale(segment1.length()), unscale(segment2.length()),
+        unscale(line.length()),
+        unscale(dist_between_segments1), unscale(dist_between_segments2)
+        );
+    */
+
+    // if this edge is the centerline for a very thin area, we might want to skip it
+    // in case the area is too thin
+    if (dist0 < this->min_width && dist1 < this->min_width) {
+        //printf(" => too thin, skipping\n");
+        return false;
+    }
+
+    return true;
 }
 
-Line
+const Line&
 MedialAxis::retrieve_segment(const VD::cell_type& cell) const
 {
     VD::cell_type::source_index_type index = cell.source_index() - this->points.size();
diff --git a/xs/src/libslic3r/Geometry.hpp b/xs/src/libslic3r/Geometry.hpp
index c2cacfa33..cbc3811e2 100644
--- a/xs/src/libslic3r/Geometry.hpp
+++ b/xs/src/libslic3r/Geometry.hpp
@@ -23,6 +23,21 @@ double rad2deg_dir(double angle);
 double deg2rad(double angle);
 void simplify_polygons(const Polygons &polygons, double tolerance, Polygons* retval);
 
+class ArrangeItem {
+    public:
+    Pointf pos;
+    size_t index_x, index_y;
+    coordf_t dist;
+};
+class ArrangeItemIndex {
+    public:
+    coordf_t index;
+    ArrangeItem item;
+    ArrangeItemIndex(coordf_t _index, ArrangeItem _item) : index(_index), item(_item) {};
+};
+double linint(double value, double oldmin, double oldmax, double newmin, double newmax);
+Pointfs arrange(size_t total_parts, Pointf part, coordf_t dist, const BoundingBoxf &bb = BoundingBoxf());
+
 class MedialAxis {
     public:
     Points points;
@@ -39,7 +54,7 @@ class MedialAxis {
     Line edge_to_line(const VD::edge_type &edge) const;
     void process_edge_neighbors(const voronoi_diagram<double>::edge_type& edge, Points* points);
     bool is_valid_edge(const voronoi_diagram<double>::edge_type& edge) const;
-    Line retrieve_segment(const voronoi_diagram<double>::cell_type& cell) const;
+    const Line& retrieve_segment(const voronoi_diagram<double>::cell_type& cell) const;
 };
 
 } }
diff --git a/xs/src/libslic3r/Layer.cpp b/xs/src/libslic3r/Layer.cpp
index 2e1a8c50e..250572fb7 100644
--- a/xs/src/libslic3r/Layer.cpp
+++ b/xs/src/libslic3r/Layer.cpp
@@ -126,6 +126,14 @@ Layer::make_slices()
     }
 }
 
+void
+Layer::merge_slices()
+{
+    FOREACH_LAYERREGION(this, layerm) {
+        (*layerm)->merge_slices();
+    }
+}
+
 template <class T>
 bool
 Layer::any_internal_region_slice_contains(const T &item) const
diff --git a/xs/src/libslic3r/Layer.hpp b/xs/src/libslic3r/Layer.hpp
index 6dd6e81a5..d34abec36 100644
--- a/xs/src/libslic3r/Layer.hpp
+++ b/xs/src/libslic3r/Layer.hpp
@@ -47,7 +47,7 @@ class LayerRegion
     PolylineCollection unsupported_bridge_edges;
 
     // ordered collection of extrusion paths/loops to build all perimeters
-    // (this collection contains both ExtrusionPath and ExtrusionLoop objects)
+    // (this collection contains only ExtrusionEntityCollection objects)
     ExtrusionEntityCollection perimeters;
 
     // ordered collection of extrusion paths to fill surfaces
@@ -95,6 +95,7 @@ class Layer {
     LayerRegion* add_region(PrintRegion* print_region);
     
     void make_slices();
+    void merge_slices();
     template <class T> bool any_internal_region_slice_contains(const T &item) const;
     template <class T> bool any_bottom_region_slice_contains(const T &item) const;
     
diff --git a/xs/src/libslic3r/Model.cpp b/xs/src/libslic3r/Model.cpp
index d03a2916c..8d98b4d6b 100644
--- a/xs/src/libslic3r/Model.cpp
+++ b/xs/src/libslic3r/Model.cpp
@@ -1,4 +1,5 @@
 #include "Model.hpp"
+#include "Geometry.hpp"
 
 namespace Slic3r {
 
@@ -481,7 +482,12 @@ ModelObject::center_around_origin()
     
     if (!this->instances.empty()) {
         for (ModelInstancePtrs::const_iterator i = this->instances.begin(); i != this->instances.end(); ++i) {
-            (*i)->offset.translate(-vector.x, -vector.y);
+            // apply rotation and scaling to vector as well before translating instance,
+            // in order to leave final position unaltered
+            Vectorf3 v = vector.negative();
+            v.rotate((*i)->rotation, (*i)->offset);
+            v.scale((*i)->scaling_factor);
+            (*i)->offset.translate(v.x, v.y);
         }
         this->update_bounding_box();
     }
@@ -514,6 +520,26 @@ ModelObject::scale(const Pointf3 &versor)
     this->invalidate_bounding_box();
 }
 
+void
+ModelObject::rotate(float angle, const Axis &axis)
+{
+    for (ModelVolumePtrs::const_iterator v = this->volumes.begin(); v != this->volumes.end(); ++v) {
+        (*v)->mesh.rotate(angle, axis);
+    }
+    this->origin_translation = Pointf3(0,0,0);
+    this->invalidate_bounding_box();
+}
+
+void
+ModelObject::flip(const Axis &axis)
+{
+    for (ModelVolumePtrs::const_iterator v = this->volumes.begin(); v != this->volumes.end(); ++v) {
+        (*v)->mesh.flip(axis);
+    }
+    this->origin_translation = Pointf3(0,0,0);
+    this->invalidate_bounding_box();
+}
+
 size_t
 ModelObject::materials_count() const
 {
diff --git a/xs/src/libslic3r/Model.hpp b/xs/src/libslic3r/Model.hpp
index 2ec7c5b08..e5683cb57 100644
--- a/xs/src/libslic3r/Model.hpp
+++ b/xs/src/libslic3r/Model.hpp
@@ -129,6 +129,8 @@ class ModelObject
     void translate(const Vectorf3 &vector);
     void translate(coordf_t x, coordf_t y, coordf_t z);
     void scale(const Pointf3 &versor);
+    void rotate(float angle, const Axis &axis);
+    void flip(const Axis &axis);
     size_t materials_count() const;
     size_t facets_count() const;
     bool needed_repair() const;
@@ -175,7 +177,7 @@ class ModelInstance
 {
     friend class ModelObject;
     public:
-    double rotation;            // around mesh center point
+    double rotation;            // in radians around mesh center point
     double scaling_factor;
     Pointf offset;              // in unscaled coordinates
     
diff --git a/xs/src/libslic3r/PlaceholderParser.cpp b/xs/src/libslic3r/PlaceholderParser.cpp
index 31056dd2c..583cf51e6 100644
--- a/xs/src/libslic3r/PlaceholderParser.cpp
+++ b/xs/src/libslic3r/PlaceholderParser.cpp
@@ -29,22 +29,14 @@ PlaceholderParser::update_timestamp()
         ss << std::setw(2) << std::setfill('0') << timeinfo->tm_hour;
         ss << std::setw(2) << std::setfill('0') << timeinfo->tm_min;
         ss << std::setw(2) << std::setfill('0') << timeinfo->tm_sec;
-        this->_single["timestamp"] = ss.str();
+        this->set("timestamp", ss.str());
     }
-    this->_single["year"]   = this->_int_to_string(1900 + timeinfo->tm_year);
-    this->_single["month"]  = this->_int_to_string(1 + timeinfo->tm_mon);
-    this->_single["day"]    = this->_int_to_string(timeinfo->tm_mday);
-    this->_single["hour"]   = this->_int_to_string(timeinfo->tm_hour);
-    this->_single["minute"] = this->_int_to_string(timeinfo->tm_min);
-    this->_single["second"] = this->_int_to_string(timeinfo->tm_sec);
-}
-
-std::string
-PlaceholderParser::_int_to_string(int value) const
-{
-    std::ostringstream ss;
-    ss << value;
-    return ss.str();
+    this->set("year",   1900 + timeinfo->tm_year);
+    this->set("month",  1 + timeinfo->tm_mon);
+    this->set("day",    timeinfo->tm_mday);
+    this->set("hour",   timeinfo->tm_hour);
+    this->set("minute", timeinfo->tm_min);
+    this->set("second", timeinfo->tm_sec);
 }
 
 void PlaceholderParser::apply_config(DynamicPrintConfig &config)
@@ -66,53 +58,20 @@ void PlaceholderParser::apply_config(DynamicPrintConfig &config)
         i != opt_keys.end(); ++i)
     {
         const t_config_option_key &key = *i;
-
-        // set placeholders for options with multiple values
-        const ConfigOptionDef &def = (*config.def)[key];
-        switch (def.type) {
-        case coFloats:
-            this->set_multiple_from_vector(key,
-                        *(ConfigOptionFloats*)config.option(key));
-            break;
-
-        case coInts:
-            this->set_multiple_from_vector(key,
-                        *(ConfigOptionInts*)config.option(key));
-            break;
-
-        case coStrings:
-            this->set_multiple_from_vector(key,
-                        *(ConfigOptionStrings*)config.option(key));
-            break;
-
-        case coPoints:
-            this->set_multiple_from_vector(key,
-                        *(ConfigOptionPoints*)config.option(key));
-            break;
-
-        case coBools:
-            this->set_multiple_from_vector(key,
-                        *(ConfigOptionBools*)config.option(key));
-            break;
-
-        case coPoint:
-            {
-                const ConfigOptionPoint &opt =
-                    *(ConfigOptionPoint*)config.option(key);
-
-                this->_single[key] = opt.serialize();
-
-                Pointf val = opt;
-                this->_multiple[key + "_X"] = val.x;
-                this->_multiple[key + "_Y"] = val.y;
-            }
-
-            break;
-
-        default:
+        const ConfigOption* opt = config.option(key);
+        
+        if (const ConfigOptionVectorBase* optv = dynamic_cast<const ConfigOptionVectorBase*>(opt)) {
+            // set placeholders for options with multiple values
+            this->set(key, optv->vserialize());
+        } else if (const ConfigOptionPoint* optp = dynamic_cast<const ConfigOptionPoint*>(opt)) {
+            this->_single[key] = optp->serialize();
+            
+            Pointf val = *optp;
+            this->_multiple[key + "_X"] = val.x;
+            this->_multiple[key + "_Y"] = val.y;
+        } else {
             // set single-value placeholders
-            this->_single[key] = config.serialize(key);
-            break;
+            this->_single[key] = opt->serialize();
         }
     }
 }
@@ -121,34 +80,30 @@ void
 PlaceholderParser::set(const std::string &key, const std::string &value)
 {
     this->_single[key] = value;
+    this->_multiple.erase(key);
 }
 
-std::ostream& operator<<(std::ostream &stm, const Pointf &pointf)
+void
+PlaceholderParser::set(const std::string &key, int value)
 {
-    return stm << pointf.x << "," << pointf.y;
+    std::ostringstream ss;
+    ss << value;
+    this->set(key, ss.str());
 }
 
-template<class T>
-void PlaceholderParser::set_multiple_from_vector(const std::string &key,
-    ConfigOptionVector<T> &opt)
+void
+PlaceholderParser::set(const std::string &key, const std::vector<std::string> &values)
 {
-    const std::vector<T> &vals = opt.values;
-
-    for (size_t i = 0; i < vals.size(); ++i) {
-        std::stringstream multikey_stm;
-        multikey_stm << key << "_" << i;
-
-        std::stringstream val_stm;
-        val_stm << vals[i];
-
-        this->_multiple[multikey_stm.str()] = val_stm.str();
-    }
-
-    if (vals.size() > 0) {
-        std::stringstream val_stm;
-        val_stm << vals[0];
-        this->_multiple[key] = val_stm.str();
+    for (std::vector<std::string>::const_iterator v = values.begin(); v != values.end(); ++v) {
+        std::stringstream ss;
+        ss << key << "_" << (v - values.begin());
+        
+        this->_multiple[ ss.str() ] = *v;
+        if (v == values.begin()) {
+            this->_multiple[key] = *v;
+        }
     }
+    this->_single.erase(key);
 }
 
 #ifdef SLIC3RXS
diff --git a/xs/src/libslic3r/PlaceholderParser.hpp b/xs/src/libslic3r/PlaceholderParser.hpp
index eb061fab2..25d1bcdc3 100644
--- a/xs/src/libslic3r/PlaceholderParser.hpp
+++ b/xs/src/libslic3r/PlaceholderParser.hpp
@@ -5,6 +5,7 @@
 #include <myinit.h>
 #include <map>
 #include <string>
+#include <vector>
 #include "PrintConfig.hpp"
 
 
@@ -20,12 +21,8 @@ class PlaceholderParser
     void update_timestamp();
     void apply_config(DynamicPrintConfig &config);
     void set(const std::string &key, const std::string &value);
-
-    private:
-    template<class T>
-    void set_multiple_from_vector(
-        const std::string &key, ConfigOptionVector<T> &opt);
-    std::string _int_to_string(int value) const;
+    void set(const std::string &key, int value);
+    void set(const std::string &key, const std::vector<std::string> &values);
 };
 
 }
diff --git a/xs/src/libslic3r/Point.cpp b/xs/src/libslic3r/Point.cpp
index 9a564f879..9707cd931 100644
--- a/xs/src/libslic3r/Point.cpp
+++ b/xs/src/libslic3r/Point.cpp
@@ -3,7 +3,6 @@
 #include "MultiPoint.hpp"
 #include <algorithm>
 #include <cmath>
-#include <sstream>
 
 namespace Slic3r {
 
@@ -340,6 +339,12 @@ REGISTER_CLASS(Point3, "Point3");
 
 #endif
 
+std::ostream&
+operator<<(std::ostream &stm, const Pointf &pointf)
+{
+    return stm << pointf.x << "," << pointf.y;
+}
+
 void
 Pointf::scale(double factor)
 {
diff --git a/xs/src/libslic3r/Point.hpp b/xs/src/libslic3r/Point.hpp
index 327199690..f9850c774 100644
--- a/xs/src/libslic3r/Point.hpp
+++ b/xs/src/libslic3r/Point.hpp
@@ -5,6 +5,7 @@
 #include <vector>
 #include <math.h>
 #include <string>
+#include <sstream>
 
 namespace Slic3r {
 
@@ -77,6 +78,8 @@ class Point3 : public Point
     explicit Point3(coord_t _x = 0, coord_t _y = 0, coord_t _z = 0): Point(_x, _y), z(_z) {};
 };
 
+std::ostream& operator<<(std::ostream &stm, const Pointf &pointf);
+
 class Pointf
 {
     public:
diff --git a/xs/src/libslic3r/Polyline.cpp b/xs/src/libslic3r/Polyline.cpp
index 710ca9bd1..22f190dbd 100644
--- a/xs/src/libslic3r/Polyline.cpp
+++ b/xs/src/libslic3r/Polyline.cpp
@@ -139,11 +139,31 @@ Polyline::simplify_by_visibility(const T &area)
     Points &pp = this->points;
     
     // find first point in area
-    size_t start = 0;
-    while (start < pp.size() && !area.contains(pp[start])) {
-        start++;
+    size_t s = 0;
+    while (s < pp.size() && !area.contains(pp[s])) {
+        ++s;
     }
     
+    // find last point in area
+    size_t e = pp.size()-1;
+    while (e > 0 && !area.contains(pp[e])) {
+        --e;
+    }
+    
+    // this ugly algorithm resembles a binary search
+    while (e > s + 1) {
+        size_t mid = (s + e) / 2;
+        if (area.contains(Line(pp[s], pp[mid]))) {
+            pp.erase(pp.begin() + s + 1, pp.begin() + mid);
+            // repeat recursively until no further simplification is possible
+            ++s;
+            e = pp.size()-1;
+        } else {
+            e = mid;
+        }
+    }
+    /*
+    // The following implementation is complete but it's not efficient at all:
     for (size_t s = start; s < pp.size() && !pp.empty(); ++s) {
         // find the farthest point to which we can build
         // a line that is contained in the supplied area
@@ -158,6 +178,7 @@ Polyline::simplify_by_visibility(const T &area)
             }
         }
     }
+    */
 }
 template void Polyline::simplify_by_visibility<ExPolygon>(const ExPolygon &area);
 template void Polyline::simplify_by_visibility<ExPolygonCollection>(const ExPolygonCollection &area);
diff --git a/xs/src/libslic3r/Print.cpp b/xs/src/libslic3r/Print.cpp
index d3bb43b3c..3ee2d0c1f 100644
--- a/xs/src/libslic3r/Print.cpp
+++ b/xs/src/libslic3r/Print.cpp
@@ -172,7 +172,8 @@ Print::invalidate_state_by_config_options(const std::vector<t_config_option_key>
         } else if (*opt_key == "brim_width") {
             steps.insert(psBrim);
             steps.insert(psSkirt);
-        } else if (*opt_key == "nozzle_diameter") {
+        } else if (*opt_key == "nozzle_diameter"
+            || *opt_key == "resolution") {
             osteps.insert(posSlice);
         } else if (*opt_key == "avoid_crossing_perimeters"
             || *opt_key == "bed_shape"
@@ -300,7 +301,7 @@ Print::step_done(PrintObjectStep step) const
 
 // returns 0-based indices of used extruders
 std::set<size_t>
-Print::extruders() const
+Print::object_extruders() const
 {
     std::set<size_t> extruders;
     
@@ -316,6 +317,16 @@ Print::extruders() const
         if ((*region)->config.top_solid_layers.value > 0 || (*region)->config.bottom_solid_layers.value > 0)
             extruders.insert((*region)->config.solid_infill_extruder - 1);
     }
+    
+    return extruders;
+}
+
+// returns 0-based indices of used extruders
+std::set<size_t>
+Print::support_material_extruders() const
+{
+    std::set<size_t> extruders;
+    
     FOREACH_OBJECT(this, object) {
         if ((*object)->has_support_material()) {
             extruders.insert((*object)->config.support_material_extruder - 1);
@@ -326,6 +337,18 @@ Print::extruders() const
     return extruders;
 }
 
+// returns 0-based indices of used extruders
+std::set<size_t>
+Print::extruders() const
+{
+    std::set<size_t> extruders = this->object_extruders();
+    
+    std::set<size_t> s_extruders = this->support_material_extruders();
+    extruders.insert(s_extruders.begin(), s_extruders.end());
+    
+    return extruders;
+}
+
 void
 Print::_simplify_slices(double distance)
 {
diff --git a/xs/src/libslic3r/Print.hpp b/xs/src/libslic3r/Print.hpp
index 47defe770..05a60001b 100644
--- a/xs/src/libslic3r/Print.hpp
+++ b/xs/src/libslic3r/Print.hpp
@@ -199,6 +199,8 @@ class Print
     Flow brim_flow() const;
     Flow skirt_flow() const;
     
+    std::set<size_t> object_extruders() const;
+    std::set<size_t> support_material_extruders() const;
     std::set<size_t> extruders() const;
     void _simplify_slices(double distance);
     double max_allowed_layer_height() const;
diff --git a/xs/src/libslic3r/PrintConfig.cpp b/xs/src/libslic3r/PrintConfig.cpp
index 4bf981473..d356fcc89 100644
--- a/xs/src/libslic3r/PrintConfig.cpp
+++ b/xs/src/libslic3r/PrintConfig.cpp
@@ -232,6 +232,12 @@ PrintConfigDef::build_def() {
     Options["fan_below_layer_time"].min = 0;
     Options["fan_below_layer_time"].max = 1000;
 
+    Options["filament_colour"].type = coStrings;
+    Options["filament_colour"].label = "Color";
+    Options["filament_colour"].tooltip = "This is only used in the Slic3r interface as a visual help.";
+    Options["filament_colour"].cli = "filament-color=s@";
+    Options["filament_colour"].gui_type = "color";
+
     Options["filament_diameter"].type = coFloats;
     Options["filament_diameter"].label = "Diameter";
     Options["filament_diameter"].tooltip = "Enter your filament diameter here. Good precision is required, so use a caliper and do multiple measurements along the filament, then compute the average.";
diff --git a/xs/src/libslic3r/PrintConfig.hpp b/xs/src/libslic3r/PrintConfig.hpp
index 8952afa8d..3599c2219 100644
--- a/xs/src/libslic3r/PrintConfig.hpp
+++ b/xs/src/libslic3r/PrintConfig.hpp
@@ -409,6 +409,7 @@ class PrintConfig : public GCodeConfig
     ConfigOptionPoints              extruder_offset;
     ConfigOptionBool                fan_always_on;
     ConfigOptionInt                 fan_below_layer_time;
+    ConfigOptionStrings             filament_colour;
     ConfigOptionFloat               first_layer_acceleration;
     ConfigOptionInt                 first_layer_bed_temperature;
     ConfigOptionFloatOrPercent      first_layer_extrusion_width;
@@ -464,6 +465,8 @@ class PrintConfig : public GCodeConfig
         this->extruder_offset.values[0]                          = Pointf(0,0);
         this->fan_always_on.value                                = false;
         this->fan_below_layer_time.value                         = 60;
+        this->filament_colour.values.resize(1);
+        this->filament_colour.values[0]                          = "#FFFFFF";
         this->first_layer_acceleration.value                     = 0;
         this->first_layer_bed_temperature.value                  = 0;
         this->first_layer_extrusion_width.value                  = 200;
@@ -523,6 +526,7 @@ class PrintConfig : public GCodeConfig
         if (opt_key == "extruder_offset")                            return &this->extruder_offset;
         if (opt_key == "fan_always_on")                              return &this->fan_always_on;
         if (opt_key == "fan_below_layer_time")                       return &this->fan_below_layer_time;
+        if (opt_key == "filament_colour")                             return &this->filament_colour;
         if (opt_key == "first_layer_acceleration")                   return &this->first_layer_acceleration;
         if (opt_key == "first_layer_bed_temperature")                return &this->first_layer_bed_temperature;
         if (opt_key == "first_layer_extrusion_width")                return &this->first_layer_extrusion_width;
diff --git a/xs/src/libslic3r/PrintObject.cpp b/xs/src/libslic3r/PrintObject.cpp
index cf1ee20e4..46d08e06f 100644
--- a/xs/src/libslic3r/PrintObject.cpp
+++ b/xs/src/libslic3r/PrintObject.cpp
@@ -222,8 +222,7 @@ PrintObject::invalidate_state_by_config_options(const std::vector<t_config_optio
             || *opt_key == "thin_walls"
             || *opt_key == "external_perimeters_first") {
             steps.insert(posPerimeters);
-        } else if (*opt_key == "resolution"
-            || *opt_key == "layer_height"
+        } else if (*opt_key == "layer_height"
             || *opt_key == "first_layer_height"
             || *opt_key == "xy_size_compensation"
             || *opt_key == "raft_layers") {
diff --git a/xs/src/libslic3r/TriangleMesh.cpp b/xs/src/libslic3r/TriangleMesh.cpp
index b25df7e0e..822d6ffb3 100644
--- a/xs/src/libslic3r/TriangleMesh.cpp
+++ b/xs/src/libslic3r/TriangleMesh.cpp
@@ -200,40 +200,61 @@ void TriangleMesh::translate(float x, float y, float z)
     stl_invalidate_shared_vertices(&this->stl);
 }
 
+void TriangleMesh::rotate(float angle, const Axis &axis)
+{
+    // admesh uses degrees
+    angle = Slic3r::Geometry::rad2deg(angle);
+    
+    if (axis == X) {
+        stl_rotate_x(&(this->stl), angle);
+    } else if (axis == Y) {
+        stl_rotate_y(&(this->stl), angle);
+    } else if (axis == Z) {
+        stl_rotate_z(&(this->stl), angle);
+    }
+    stl_invalidate_shared_vertices(&this->stl);
+}
+
 void TriangleMesh::rotate_x(float angle)
 {
-    stl_rotate_x(&(this->stl), angle);
-    stl_invalidate_shared_vertices(&this->stl);
+    this->rotate(angle, X);
 }
 
 void TriangleMesh::rotate_y(float angle)
 {
-    stl_rotate_y(&(this->stl), angle);
-    stl_invalidate_shared_vertices(&this->stl);
+    this->rotate(angle, Y);
 }
 
 void TriangleMesh::rotate_z(float angle)
 {
-    stl_rotate_z(&(this->stl), angle);
+    this->rotate(angle, Z);
+}
+
+void TriangleMesh::flip(const Axis &axis)
+{
+    if (axis == X) {
+        stl_mirror_yz(&this->stl);
+    } else if (axis == Y) {
+        stl_mirror_xz(&this->stl);
+    } else if (axis == Z) {
+        stl_mirror_xy(&this->stl);
+    }
     stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::flip_x()
 {
-    stl_mirror_yz(&this->stl);
-    stl_invalidate_shared_vertices(&this->stl);
+    this->flip(X);
 }
 
 void TriangleMesh::flip_y()
 {
-    stl_mirror_xz(&this->stl);
-    stl_invalidate_shared_vertices(&this->stl);
+    this->flip(Y);
 }
 
 void TriangleMesh::flip_z()
 {
-    stl_mirror_xy(&this->stl);
-    stl_invalidate_shared_vertices(&this->stl);
+    this->flip(Z);
 }
 
 void TriangleMesh::align_to_origin()
diff --git a/xs/src/libslic3r/TriangleMesh.hpp b/xs/src/libslic3r/TriangleMesh.hpp
index 43ac68419..ff12e8427 100644
--- a/xs/src/libslic3r/TriangleMesh.hpp
+++ b/xs/src/libslic3r/TriangleMesh.hpp
@@ -32,9 +32,11 @@ class TriangleMesh
     void scale(float factor);
     void scale(const Pointf3 &versor);
     void translate(float x, float y, float z);
+    void rotate(float angle, const Axis &axis);
     void rotate_x(float angle);
     void rotate_y(float angle);
     void rotate_z(float angle);
+    void flip(const Axis &axis);
     void flip_x();
     void flip_y();
     void flip_z();
diff --git a/xs/src/libslic3r/libslic3r.h b/xs/src/libslic3r/libslic3r.h
index 25d3c7f48..fc3bd1793 100644
--- a/xs/src/libslic3r/libslic3r.h
+++ b/xs/src/libslic3r/libslic3r.h
@@ -6,7 +6,7 @@
 #include <iostream>
 #include <sstream>
 
-#define SLIC3R_VERSION "1.2.7-dev"
+#define SLIC3R_VERSION "1.2.8-dev"
 
 #define EPSILON 1e-4
 #define SCALING_FACTOR 0.000001
@@ -17,7 +17,12 @@
 typedef long coord_t;
 typedef double coordf_t;
 
-namespace Slic3r {}
+namespace Slic3r {
+
+// TODO: make sure X = 0
+enum Axis { X, Y, Z };
+
+}
 using namespace Slic3r;
 
 /* Implementation of CONFESS("foo"): */
diff --git a/xs/t/03_point.t b/xs/t/03_point.t
index d983fafc9..cb71f68f5 100644
--- a/xs/t/03_point.t
+++ b/xs/t/03_point.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 22;
+use Test::More tests => 24;
 
 my $point = Slic3r::Point->new(10, 15);
 is_deeply [ @$point ], [10, 15], 'point roundtrip';
@@ -32,12 +32,14 @@ ok !$point->coincides_with($point2), 'coincides_with';
 
 {
     my $line = Slic3r::Line->new([0,0], [100,0]);
-    is +Slic3r::Point->new(0,0)->distance_to_line($line),    0, 'distance_to_line()';
+    is +Slic3r::Point->new(0,0)  ->distance_to_line($line),  0, 'distance_to_line()';
     is +Slic3r::Point->new(100,0)->distance_to_line($line),  0, 'distance_to_line()';
-    is +Slic3r::Point->new(50,0)->distance_to_line($line),   0, 'distance_to_line()';
+    is +Slic3r::Point->new(50,0) ->distance_to_line($line),  0, 'distance_to_line()';
     is +Slic3r::Point->new(150,0)->distance_to_line($line), 50, 'distance_to_line()';
-    is +Slic3r::Point->new(0,50)->distance_to_line($line),  50, 'distance_to_line()';
+    is +Slic3r::Point->new(0,50) ->distance_to_line($line), 50, 'distance_to_line()';
     is +Slic3r::Point->new(50,50)->distance_to_line($line), 50, 'distance_to_line()';
+    is +Slic3r::Point->new(50,50) ->perp_distance_to_line($line), 50, 'perp_distance_to_line()';
+    is +Slic3r::Point->new(150,50)->perp_distance_to_line($line), 50, 'perp_distance_to_line()';
 }
 
 {
diff --git a/xs/t/09_polyline.t b/xs/t/09_polyline.t
index fa5a3c48b..0a7b8dcb0 100644
--- a/xs/t/09_polyline.t
+++ b/xs/t/09_polyline.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 21;
+use Test::More tests => 18;
 
 my $points = [
     [100, 100],
@@ -88,7 +88,8 @@ is_deeply $polyline->pp, [ @$points, @$points ], 'append_polyline';
     is scalar(@$p2), 4, 'split_at';
 }
 
-{
+# disabled because we now use a more efficient but incomplete algorithm
+if (0) {
     my $polyline = Slic3r::Polyline->new(
         map [$_,10], (0,10,20,30,40,50,60)
     );
diff --git a/xs/t/12_extrusionpathcollection.t b/xs/t/12_extrusionpathcollection.t
index 73608cba7..e7e0b1316 100644
--- a/xs/t/12_extrusionpathcollection.t
+++ b/xs/t/12_extrusionpathcollection.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 16;
+use Test::More tests => 18;
 
 my $points = [
     [100, 100],
@@ -87,4 +87,11 @@ is scalar(@{$collection->[1]}), 1, 'appended collection was duplicated';
     pass 'chained_path with no_sort';
 }
 
+{
+    my $coll2 = $collection->clone;
+    ok !$coll2->no_sort, 'expected no_sort value';
+    $coll2->no_sort(1);
+    ok $coll2->clone->no_sort, 'no_sort is kept after clone';
+}
+
 __END__
diff --git a/xs/t/14_geometry.t b/xs/t/14_geometry.t
index 8dfdecb78..70b623029 100644
--- a/xs/t/14_geometry.t
+++ b/xs/t/14_geometry.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 8;
+use Test::More tests => 9;
 
 use constant PI => 4 * atan2(1, 1);
 
@@ -31,4 +31,11 @@ use constant PI => 4 * atan2(1, 1);
     ok !Slic3r::Geometry::directions_parallel_within(PI/2, PI, 0), 'directions_parallel_within';
     ok !Slic3r::Geometry::directions_parallel_within(PI/2, PI, PI/180), 'directions_parallel_within';
 }
+
+{
+    my $positions = Slic3r::Geometry::arrange(4, Slic3r::Pointf->new(20, 20),
+        5, Slic3r::Geometry::BoundingBoxf->new);
+    is scalar(@$positions), 4, 'arrange() returns expected number of positions';
+}
+
 __END__
diff --git a/xs/xsp/ExtrusionEntityCollection.xsp b/xs/xsp/ExtrusionEntityCollection.xsp
index a7c5a8be0..08577c892 100644
--- a/xs/xsp/ExtrusionEntityCollection.xsp
+++ b/xs/xsp/ExtrusionEntityCollection.xsp
@@ -7,6 +7,8 @@
 
 %name{Slic3r::ExtrusionPath::Collection} class ExtrusionEntityCollection {
     %name{_new} ExtrusionEntityCollection();
+    Clone<ExtrusionEntityCollection> clone()
+        %code{% RETVAL = THIS->clone(); %};
     void reverse();
     void clear()
         %code{% THIS->entities.clear(); %};
@@ -24,6 +26,8 @@
     Clone<Point> last_point();
     int count()
         %code{% RETVAL = THIS->entities.size(); %};
+    int items_count()
+        %code{% RETVAL = THIS->items_count(); %};
     bool empty()
         %code{% RETVAL = THIS->entities.empty(); %};
     std::vector<size_t> orig_indices()
diff --git a/xs/xsp/Geometry.xsp b/xs/xsp/Geometry.xsp
index 0df74a4bd..c5442a0b6 100644
--- a/xs/xsp/Geometry.xsp
+++ b/xs/xsp/Geometry.xsp
@@ -8,6 +8,9 @@
 
 %package{Slic3r::Geometry};
 
+Pointfs arrange(size_t total_parts, Pointf* part, coordf_t dist, BoundingBoxf* bb)
+    %code{% RETVAL = Slic3r::Geometry::arrange(total_parts, *part, dist, *bb); %};
+
 %{
 
 bool
@@ -87,4 +90,17 @@ simplify_polygons(polygons, tolerance)
     OUTPUT:
         RETVAL
 
+
+IV
+_constant()
+  ALIAS:
+    X           = X
+    Y           = Y
+    Z           = Z
+  PROTOTYPE:
+  CODE:
+    RETVAL = ix;
+  OUTPUT: RETVAL
+
 %}
+
diff --git a/xs/xsp/Layer.xsp b/xs/xsp/Layer.xsp
index 611e2cae9..e8372206c 100644
--- a/xs/xsp/Layer.xsp
+++ b/xs/xsp/Layer.xsp
@@ -71,6 +71,7 @@
         %code%{ RETVAL = (int)(intptr_t)THIS; %};
     
     void make_slices();
+    void merge_slices();
     bool any_internal_region_slice_contains_polyline(Polyline* polyline)
         %code%{ RETVAL = THIS->any_internal_region_slice_contains(*polyline); %};
     bool any_bottom_region_slice_contains_polyline(Polyline* polyline)
diff --git a/xs/xsp/Model.xsp b/xs/xsp/Model.xsp
index 9870d7dd5..cf9b974f4 100644
--- a/xs/xsp/Model.xsp
+++ b/xs/xsp/Model.xsp
@@ -182,6 +182,8 @@ ModelMaterial::attributes()
     void translate(double x, double y, double z);
     void scale_xyz(Pointf3* versor)
         %code{% THIS->scale(*versor); %};
+    void rotate(float angle, Axis axis);
+    void flip(Axis axis);
     
     Model* cut(double z)
         %code%{
diff --git a/xs/xsp/PlaceholderParser.xsp b/xs/xsp/PlaceholderParser.xsp
index 760f3b71f..b36a47189 100644
--- a/xs/xsp/PlaceholderParser.xsp
+++ b/xs/xsp/PlaceholderParser.xsp
@@ -14,6 +14,8 @@
     void apply_config(DynamicPrintConfig *config)
         %code%{ THIS->apply_config(*config); %};
     void set(std::string key, std::string value);
+    void set_multiple(std::string key, std::vector<std::string> values)
+        %code%{ THIS->set(key, values); %};
 
     void _single_set(std::string k, std::string v)
         %code%{ THIS->_single[k] = v; %};
diff --git a/xs/xsp/Print.xsp b/xs/xsp/Print.xsp
index c9b93bba3..afcd6f839 100644
--- a/xs/xsp/Print.xsp
+++ b/xs/xsp/Print.xsp
@@ -161,6 +161,22 @@ _constant()
     void set_step_started(PrintStep step)
         %code%{ THIS->state.set_started(step); %};
     
+    std::vector<int> object_extruders()
+        %code%{
+            std::set<size_t> extruders = THIS->object_extruders();
+            RETVAL.reserve(extruders.size());
+            for (std::set<size_t>::const_iterator e = extruders.begin(); e != extruders.end(); ++e) {
+                RETVAL.push_back(*e);
+            }
+        %};
+    std::vector<int> support_material_extruders()
+        %code%{
+            std::set<size_t> extruders = THIS->support_material_extruders();
+            RETVAL.reserve(extruders.size());
+            for (std::set<size_t>::const_iterator e = extruders.begin(); e != extruders.end(); ++e) {
+                RETVAL.push_back(*e);
+            }
+        %};
     std::vector<int> extruders()
         %code%{
             std::set<size_t> extruders = THIS->extruders();
diff --git a/xs/xsp/my.map b/xs/xsp/my.map
index bf5828004..395b630e1 100644
--- a/xs/xsp/my.map
+++ b/xs/xsp/my.map
@@ -188,6 +188,7 @@ Clone<BridgeDetector>      O_OBJECT_SLIC3R_T
 
 GLVertexArray*             O_OBJECT_SLIC3R
 
+Axis                  T_UV
 ExtrusionLoopRole     T_UV
 ExtrusionRole     T_UV
 FlowRole     T_UV
diff --git a/xs/xsp/typemap.xspt b/xs/xsp/typemap.xspt
index 845b98707..050e61b99 100644
--- a/xs/xsp/typemap.xspt
+++ b/xs/xsp/typemap.xspt
@@ -176,6 +176,12 @@
 %typemap{SupportLayerPtrs*};
 
 
+%typemap{Axis}{parsed}{
+  %cpp_type{Axis};
+  %precall_code{%
+    $CVar = (Axis)SvUV($PerlVar);
+  %};
+};
 %typemap{SurfaceType}{parsed}{
   %cpp_type{SurfaceType};
   %precall_code{%