diff --git a/lib/Slic3r/GUI/2DBed.pm b/lib/Slic3r/GUI/2DBed.pm
index dd2cbdb1e..6a3e26a9f 100644
--- a/lib/Slic3r/GUI/2DBed.pm
+++ b/lib/Slic3r/GUI/2DBed.pm
@@ -5,8 +5,8 @@ use warnings;
 use List::Util qw(min max);
 use Slic3r::Geometry qw(PI X Y unscale deg2rad);
 use Slic3r::Geometry::Clipper qw(intersection_pl);
-use Wx qw(:misc :pen :brush :font wxTAB_TRAVERSAL);
-use Wx::Event qw(EVT_PAINT EVT_MOUSE_EVENTS);
+use Wx qw(:misc :pen :brush :font :systemsettings wxTAB_TRAVERSAL wxSOLID);
+use Wx::Event qw(EVT_PAINT EVT_ERASE_BACKGROUND EVT_MOUSE_EVENTS EVT_SIZE);
 use base qw(Wx::Panel Class::Accessor);
 
 __PACKAGE__->mk_accessors(qw(bed_shape interactive pos _scale_factor _shift on_move));
@@ -15,19 +15,33 @@ sub new {
     my ($class, $parent, $bed_shape) = @_;
     
     my $self = $class->SUPER::new($parent, -1, wxDefaultPosition, [250,-1], wxTAB_TRAVERSAL);
+    $self->{user_drawn_background} = $^O ne 'darwin';
     $self->bed_shape($bed_shape // []);
     EVT_PAINT($self, \&_repaint);
+    EVT_ERASE_BACKGROUND($self, sub {}) if $self->{user_drawn_background};
     EVT_MOUSE_EVENTS($self, \&_mouse_event);
-    
+    EVT_SIZE($self, sub { $self->Refresh; });
     return $self;
 }
 
 sub _repaint {
-    my ($self) = @_;
+    my ($self, $event) = @_;
     
     my $dc = Wx::AutoBufferedPaintDC->new($self);
     my ($cw, $ch) = $self->GetSizeWH;
     return if $cw == 0;  # when canvas is not rendered yet, size is 0,0
+
+    if ($self->{user_drawn_background}) {
+        # On all systems the AutoBufferedPaintDC() achieves double buffering.
+        # On MacOS the background is erased, on Windows the background is not erased 
+        # and on Linux/GTK the background is erased to gray color.
+        # Fill DC with the background on Windows & Linux/GTK.
+        my $color = Wx::SystemSettings::GetSystemColour(wxSYS_COLOUR_3DLIGHT);
+        $dc->SetPen(Wx::Pen->new($color, 1, wxSOLID));
+        $dc->SetBrush(Wx::Brush->new($color, wxSOLID));
+        my $rect = $self->GetUpdateRegion()->GetBox();
+        $dc->DrawRectangle($rect->GetLeft(), $rect->GetTop(), $rect->GetWidth(), $rect->GetHeight());
+    }
     
     # turn $cw and $ch from sizes to max coordinates
     $cw--;
@@ -39,11 +53,12 @@ sub _repaint {
     ]);
     
     # leave space for origin point
-    $cbb->set_x_min($cbb->x_min + 2);
-    $cbb->set_y_max($cbb->y_max - 2);
+    $cbb->set_x_min($cbb->x_min + 4);
+    $cbb->set_x_max($cbb->x_max - 4);
+    $cbb->set_y_max($cbb->y_max - 4);
     
     # leave space for origin label
-    $cbb->set_y_max($cbb->y_max - 10);
+    $cbb->set_y_max($cbb->y_max - 13);
     
     # read new size
     ($cw, $ch) = @{$cbb->size};
diff --git a/lib/Slic3r/GUI/BedShapeDialog.pm b/lib/Slic3r/GUI/BedShapeDialog.pm
index ee794a261..49c8b9e07 100644
--- a/lib/Slic3r/GUI/BedShapeDialog.pm
+++ b/lib/Slic3r/GUI/BedShapeDialog.pm
@@ -133,11 +133,14 @@ sub on_change {
     $self->{on_change} = $cb // sub {};
 }
 
+# Called from the constructor.
+# Set the initial bed shape from a list of points.
+# Deduce the bed shape type (rect, circle, custom)
+# This routine shall be smart enough if the user messes up
+# with the list of points in the ini file directly.
 sub _set_shape {
     my ($self, $points) = @_;
     
-    $self->{bed_shape} = $points;
-    
     # is this a rectangle?
     if (@$points == 4) {
         my $polygon = Slic3r::Polygon->new_scale(@$points);
@@ -164,6 +167,7 @@ sub _set_shape {
     
     # is this a circle?
     {
+        # Analyze the array of points. Do they reside on a circle?
         my $polygon = Slic3r::Polygon->new_scale(@$points);
         my $center = $polygon->bounding_box->center;
         my @vertex_distances = map $center->distance_to($_), @$polygon;
@@ -178,10 +182,24 @@ sub _set_shape {
         }
     }
     
+    if (@$points < 3) {
+        # Invalid polygon. Revert to default bed dimensions.
+        $self->{shape_options_book}->SetSelection(SHAPE_RECTANGULAR);
+        my $optgroup = $self->{optgroups}[SHAPE_RECTANGULAR];
+        $optgroup->set_value('rect_size', [200, 200]);
+        $optgroup->set_value('rect_origin', [0, 0]);
+        $self->_update_shape;
+        return;
+    }
+
+    # This is a custom bed shape, use the polygon provided.
     $self->{shape_options_book}->SetSelection(SHAPE_CUSTOM);
+    # Copy the polygon to the canvas, make a copy of the array.
+    $self->{canvas}->bed_shape([@$points]);
     $self->_update_shape;
 }
 
+# Update the bed shape from the dialog fields.
 sub _update_shape {
     my ($self) = @_;
     
@@ -229,8 +247,11 @@ sub _update_shape {
 sub _update_preview {
     my ($self) = @_;
     $self->{canvas}->Refresh if $self->{canvas};
+    $self->Refresh;
 }
 
+# Called from the constructor.
+# Create a panel for a rectangular / circular / custom bed shape. 
 sub _init_shape_options_page {
     my ($self, $title) = @_;
     
@@ -252,6 +273,7 @@ sub _init_shape_options_page {
     return $optgroup;
 }
 
+# Loads an stl file, projects it to the XY plane and calculates a polygon.
 sub _load_stl {
     my ($self) = @_;
     
@@ -266,7 +288,7 @@ sub _load_stl {
     my $model = Slic3r::Model->read_from_file($input_file);
     my $mesh = $model->raw_mesh;
     my $expolygons = $mesh->horizontal_projection;
-    
+
     if (@$expolygons == 0) {
         Slic3r::GUI::show_error($self, "The selected file contains no geometry.");
         return;
@@ -277,9 +299,11 @@ sub _load_stl {
     }
     
     my $polygon = $expolygons->[0]->contour;
-    $self->{canvas}->bed_shape([ map [ unscale($_->x), unscale($_->y) ], @$polygon ]);  #))
+    $self->{canvas}->bed_shape([ map [ unscale($_->x), unscale($_->y) ], @$polygon ]);
+    $self->_update_preview();
 }
 
+# Returns the resulting bed shape polygon. This value will be stored to the ini file.
 sub GetValue {
     my ($self) = @_;
     return $self->{canvas}->bed_shape;