prototyping tweakable XY supports;

option should be present now in advanced support menu.
Can't figure out what's going on atm; support should be moving but isn't

lib/Slic3r/GUI/Tab.pm

@@ -523,6 +523,7 @@ sub build {
         max_volumetric_extrusion_rate_slope_positive max_volumetric_extrusion_rate_slope_negative
         perimeter_speed small_perimeter_speed external_perimeter_speed infill_speed 
         solid_infill_speed top_solid_infill_speed support_material_speed 
+        support_material_xy_spacing
         support_material_interface_speed bridge_speed gap_fill_speed
         travel_speed
         first_layer_speed
@@ -648,6 +649,7 @@ sub build {
             $optgroup->append_single_option_line('support_material_interface_spacing');
             $optgroup->append_single_option_line('support_material_interface_contact_loops');
             $optgroup->append_single_option_line('support_material_buildplate_only');
+            $optgroup->append_single_option_line('support_material_xy_spacing');
             $optgroup->append_single_option_line('dont_support_bridges');
             $optgroup->append_single_option_line('support_material_synchronize_layers');
         }

lib/Slic3r/Print/SupportMaterial.pm

@@ -372,7 +372,7 @@ sub object_top {
                 # grow top surfaces so that interface and support generation are generated
                 # with some spacing from object - it looks we don't need the actual
                 # top shapes so this can be done here
-                $top{ $layer->print_z } = offset($touching, $self->flow->scaled_width + ($self->object_config->support_material_xy_spacing / 0.000001) );
+                $top{ $layer->print_z } = offset($touching, $self->flow->scaled_width + $self->object_config->support_material_xy_spacing);
             }
             
             # remove the areas that touched from the projection that will continue on 
@@ -624,10 +624,11 @@ sub clip_with_object {
         # $layer->slices contains the full shape of layer, thus including
         # perimeter's width. $support contains the full shape of support
         # material, thus including the width of its foremost extrusion.
-        # We leave a gap equal to a full extrusion width.
+        # We leave a gap equal to a full extrusion width + an offset
+        # if the user wants to play around with this setting.
         $support->{$i} = diff(
             $support->{$i},
-            offset([ map @$_, map @{$_->slices}, @layers ], +($self->flow->scaled_width +($self->object_config->support_material_xy_spacing / 0.000001))),
+            offset([ map @$_, map @{$_->slices}, @layers ], +$self->object_config->support_material_xy_spacing),
         );
     }
 }

slic3r.pl

@@ -426,6 +426,9 @@ $j
                         Support material angle in degrees (range: 0-90, default: $config->{support_material_angle})
     --support-material-contact-distance
                         Vertical distance between object and support material (0+, default: $config->{support_material_contact_distance})
+
+    --support-material-xy-spacing
+                        horizontal distance between object and support material (0+, default: $config->{support_material_xy_spacing})
     --support-material-interface-layers
                         Number of perpendicular layers between support material and object (0+, default: $config->{support_material_interface_layers})
     --support-material-interface-spacing

xs/src/libslic3r/PrintConfig.cpp

@@ -1121,6 +1121,13 @@ PrintConfigDef::PrintConfigDef()
     def->cli = "support-material!";
     def->default_value = new ConfigOptionBool(false);
 
+    def = this->add("support_material_xy_spacing", coFloat);
+    def->label = "Extra separation between part and support (mm)";
+    def->category = "Support material";
+    def->tooltip = "Add offset to support material separation (0 is 1 extrusion width).";
+    def->cli = "support-material-xy-spacing=f";
+    def->default_value = new ConfigOptionFloat(0.0);
+
     def = this->add("support_material_angle", coInt);
     def->label = "Pattern angle";
     def->category = "Support material";

xs/src/libslic3r/PrintConfig.hpp

@@ -164,6 +164,7 @@ class PrintObjectConfig : public virtual StaticPrintConfig
     ConfigOptionBool                support_material_synchronize_layers;
     ConfigOptionInt                 support_material_threshold;
     ConfigOptionBool                support_material_with_sheath;
+    ConfigOptionFloat               support_material_xy_spacing;
     ConfigOptionFloat               xy_size_compensation;
     
     PrintObjectConfig(bool initialize = true) : StaticPrintConfig() {
@@ -198,6 +199,7 @@ class PrintObjectConfig : public virtual StaticPrintConfig
         OPT_PTR(support_material_spacing);
         OPT_PTR(support_material_speed);
         OPT_PTR(support_material_synchronize_layers);
+        OPT_PTR(support_material_xy_spacing);
         OPT_PTR(support_material_threshold);
         OPT_PTR(support_material_with_sheath);
         OPT_PTR(xy_size_compensation);

xs/src/libslic3r/PrintObject.cpp

@@ -221,6 +221,7 @@ PrintObject::invalidate_state_by_config_options(const std::vector<t_config_optio
             || *opt_key == "support_material_interface_speed"
             || *opt_key == "support_material_buildplate_only"
             || *opt_key == "support_material_pattern"
+            || *opt_key == "support_material_xy_spacing"
             || *opt_key == "support_material_spacing"
             || *opt_key == "support_material_synchronize_layers"
             || *opt_key == "support_material_threshold"