diff --git a/src/libslic3r/Config.hpp b/src/libslic3r/Config.hpp
index 9c9b5d348..80d34e821 100644
--- a/src/libslic3r/Config.hpp
+++ b/src/libslic3r/Config.hpp
@@ -1441,6 +1441,24 @@ private:
 class ConfigOptionDef
 {
 public:
+    enum class GUIType {
+        undefined,
+        // Open enums, integer value could be one of the enumerated values or something else.
+        i_enum_open,
+        // Open enums, float value could be one of the enumerated values or something else.
+        f_enum_open,
+        // Color picker, string value.
+        color,
+        // ???
+        select_open,
+        // Currently unused.
+        slider,
+        // Static text
+        legend,
+        // Vector value, but edited as a single string.
+        one_string,
+    };
+
 	// Identifier of this option. It is stored here so that it is accessible through the by_serialization_key_ordinal map.
 	t_config_option_key 				opt_key;
     // What type? bool, int, string etc.
@@ -1524,7 +1542,7 @@ public:
     // Usually empty. 
     // Special values - "i_enum_open", "f_enum_open" to provide combo box for int or float selection,
     // "select_open" - to open a selection dialog (currently only a serial port selection).
-    std::string                         gui_type;
+    GUIType                             gui_type { GUIType::undefined };
     // Usually empty. Otherwise "serialized" or "show_value"
     // The flags may be combined.
     // "serialized" - vector valued option is entered in a single edit field. Values are separated by a semicolon.
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 3aad02f91..f772f354f 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -66,7 +66,7 @@ void PrintConfigDef::init_common_params()
     def->label = L("G-code thumbnails");
     def->tooltip = L("Picture sizes to be stored into a .gcode and .sl1 files, in the following format: \"XxY, XxY, ...\"");
     def->mode = comExpert;
-    def->gui_type = "one_string";
+    def->gui_type = ConfigOptionDef::GUIType::one_string;
     def->set_default_value(new ConfigOptionPoints());
 
     def = this->add("layer_height", coFloat);
@@ -116,7 +116,7 @@ void PrintConfigDef::init_common_params()
     def = this->add("printhost_port", coString);
     def->label = L("Printer");
     def->tooltip = L("Name of the printer");
-    def->gui_type = "select_open";
+    def->gui_type = ConfigOptionDef::GUIType::select_open;
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionString(""));
     
@@ -568,7 +568,7 @@ void PrintConfigDef::init_fff_params()
     def->set_default_value(new ConfigOptionBool(true));
 
     def = this->add("extruder", coInt);
-    def->gui_type = "i_enum_open";
+    def->gui_type = ConfigOptionDef::GUIType::i_enum_open;
     def->label = L("Extruder");
     def->category = L("Extruders");
     def->tooltip = L("The extruder to use (unless more specific extruder settings are specified). "
@@ -606,7 +606,7 @@ void PrintConfigDef::init_fff_params()
     def = this->add("extruder_colour", coStrings);
     def->label = L("Extruder Color");
     def->tooltip = L("This is only used in the Slic3r interface as a visual help.");
-    def->gui_type = "color";
+    def->gui_type = ConfigOptionDef::GUIType::color;
     // Empty string means no color assigned yet.
     def->set_default_value(new ConfigOptionStrings { "" });
 
@@ -668,7 +668,7 @@ void PrintConfigDef::init_fff_params()
     def = this->add("filament_colour", coStrings);
     def->label = L("Color");
     def->tooltip = L("This is only used in the Slic3r interface as a visual help.");
-    def->gui_type = "color";
+    def->gui_type = ConfigOptionDef::GUIType::color;
     def->set_default_value(new ConfigOptionStrings { "#29B2B2" });
 
     def = this->add("filament_notes", coStrings);
@@ -812,7 +812,7 @@ void PrintConfigDef::init_fff_params()
     def = this->add("filament_type", coStrings);
     def->label = L("Filament type");
     def->tooltip = L("The filament material type for use in custom G-codes.");
-    def->gui_type = "f_enum_open";
+    def->gui_type = ConfigOptionDef::GUIType::f_enum_open;
     def->gui_flags = "show_value";
     def->enum_values.push_back("PLA");
     def->enum_values.push_back("PET");
@@ -881,7 +881,7 @@ void PrintConfigDef::init_fff_params()
     def->set_default_value(new ConfigOptionFloat(45));
 
     def = this->add("fill_density", coPercent);
-    def->gui_type = "f_enum_open";
+    def->gui_type = ConfigOptionDef::GUIType::f_enum_open;
     def->gui_flags = "show_value";
     def->label = L("Fill density");
     def->category = L("Infill");
@@ -1168,7 +1168,7 @@ void PrintConfigDef::init_fff_params()
                      "Set this parameter to zero to disable anchoring perimeters connected to a single infill line.");
     def->sidetext = L("mm or %");
     def->ratio_over = "infill_extrusion_width";
-    def->gui_type = "f_enum_open";
+    def->gui_type = ConfigOptionDef::GUIType::f_enum_open;
     def->enum_values.push_back("0");
     def->enum_values.push_back("1");
     def->enum_values.push_back("2");
@@ -1950,7 +1950,7 @@ void PrintConfigDef::init_fff_params()
 
 #if 0
     def = this->add("seam_preferred_direction", coFloat);
-//    def->gui_type = "slider";
+//    def->gui_type = ConfigOptionDef::GUIType::slider;
     def->label = L("Direction");
     def->sidetext = L("°");
     def->full_label = L("Preferred direction of the seam");
@@ -1960,7 +1960,7 @@ void PrintConfigDef::init_fff_params()
     def->set_default_value(new ConfigOptionFloat(0));
 
     def = this->add("seam_preferred_direction_jitter", coFloat);
-//    def->gui_type = "slider";
+//    def->gui_type = ConfigOptionDef::GUIType::slider;
     def->label = L("Jitter");
     def->sidetext = L("°");
     def->full_label = L("Seam preferred direction jitter");
@@ -2234,7 +2234,7 @@ void PrintConfigDef::init_fff_params()
     def->set_default_value(new ConfigOptionBool(false));
 
     def = this->add("support_material_contact_distance", coFloat);
-    def->gui_type = "f_enum_open";
+    def->gui_type = ConfigOptionDef::GUIType::f_enum_open;
     def->label = L("Top contact Z distance");
     def->category = L("Support material");
     def->tooltip = L("The vertical distance between object and support material interface. "
@@ -2252,7 +2252,7 @@ void PrintConfigDef::init_fff_params()
     def->set_default_value(new ConfigOptionFloat(0.2));
 
     def = this->add("support_material_bottom_contact_distance", coFloat);
-    def->gui_type = "f_enum_open";
+    def->gui_type = ConfigOptionDef::GUIType::f_enum_open;
     def->label = L("Bottom contact Z distance");
     def->category = L("Support material");
     def->tooltip = L("The vertical distance between the object top surface and the support material interface. "
@@ -2318,7 +2318,7 @@ void PrintConfigDef::init_fff_params()
     def->set_default_value(new ConfigOptionInt(1));
 
     auto support_material_interface_layers = def = this->add("support_material_interface_layers", coInt);
-    def->gui_type = "i_enum_open";
+    def->gui_type = ConfigOptionDef::GUIType::i_enum_open;
     def->label = L("Top interface layers");
     def->category = L("Support material");
     def->tooltip = L("Number of interface layers to insert between the object(s) and support material.");
@@ -2336,7 +2336,7 @@ void PrintConfigDef::init_fff_params()
     def->set_default_value(new ConfigOptionInt(3));
 
     def = this->add("support_material_bottom_interface_layers", coInt);
-    def->gui_type = "i_enum_open";
+    def->gui_type = ConfigOptionDef::GUIType::i_enum_open;
     def->label = L("Bottom interface layers");
     def->category = L("Support material");
     def->tooltip = L("Number of interface layers to insert between the object(s) and support material. "
@@ -2873,7 +2873,7 @@ void PrintConfigDef::init_sla_params()
     def = this->add("material_type", coString);
     def->label = L("SLA material type");
     def->tooltip = L("SLA material type");
-    def->gui_type = "f_enum_open";   // TODO: ???
+    def->gui_type = ConfigOptionDef::GUIType::f_enum_open;   // TODO: ???
     def->gui_flags = "show_value";
     def->enum_values.push_back("Tough");
     def->enum_values.push_back("Flexible");
diff --git a/src/libslic3r/SupportMaterial.cpp b/src/libslic3r/SupportMaterial.cpp
index 8dc939aed..9caac5769 100644
--- a/src/libslic3r/SupportMaterial.cpp
+++ b/src/libslic3r/SupportMaterial.cpp
@@ -2760,7 +2760,7 @@ std::pair<PrintObjectSupportMaterial::MyLayersPtr, PrintObjectSupportMaterial::M
                     Polygons polygons_top_contact_projected_base;
                     Polygons polygons_bottom_contact_projected_interface;
                     Polygons polygons_bottom_contact_projected_base;
-                    if (num_interface_layers_top > -1) {
+                    if (num_interface_layers_top > 0) {
                         // Top Z coordinate of a slab, over which we are collecting the top / bottom contact surfaces
                         coordf_t top_z              = intermediate_layers[std::min(num_intermediate - 1, idx_intermediate_layer + num_interface_layers_top - 1)]->print_z;
                         coordf_t top_inteface_z     = std::numeric_limits<coordf_t>::max();
@@ -2781,7 +2781,7 @@ std::pair<PrintObjectSupportMaterial::MyLayersPtr, PrintObjectSupportMaterial::M
                             polygons_append(top_contact_layer.bottom_z - EPSILON > top_inteface_z ? polygons_top_contact_projected_base : polygons_top_contact_projected_interface, top_contact_layer.polygons);
                         }
                     }
-                    if (num_interface_layers_bottom > -1) {
+                    if (num_interface_layers_bottom > 0) {
                         // Bottom Z coordinate of a slab, over which we are collecting the top / bottom contact surfaces
                         coordf_t bottom_z           = intermediate_layers[std::max(0, idx_intermediate_layer - num_interface_layers_bottom + 1)]->bottom_z;
                         coordf_t bottom_interface_z = - std::numeric_limits<coordf_t>::max();
diff --git a/src/slic3r/GUI/Field.cpp b/src/slic3r/GUI/Field.cpp
index 02ef87775..5af658a21 100644
--- a/src/slic3r/GUI/Field.cpp
+++ b/src/slic3r/GUI/Field.cpp
@@ -902,7 +902,7 @@ void Choice::BUILD() {
     if (m_opt.width >= 0) size.SetWidth(m_opt.width*m_em_unit);
 
 	choice_ctrl* temp;
-    if (!m_opt.gui_type.empty() && m_opt.gui_type.compare("select_open") != 0) {
+    if (m_opt.gui_type != undefined && m_opt.gui_type != ConfigOptionDef::GUIType::select_open) {
         m_is_editable = true;
         temp = new choice_ctrl(m_parent, wxID_ANY, wxString(""), wxDefaultPosition, size);
     }
@@ -1237,7 +1237,7 @@ boost::any& Choice::get_value()
         else if (m_opt_id == "brim_type")
             m_value = static_cast<BrimType>(ret_enum);
 	}
-    else if (m_opt.gui_type == "f_enum_open") {
+    else if (m_opt.gui_type == ConfigOptionDef::GUIType::f_enum_open || m_opt.gui_type == ConfigOptionDef::GUIType::i_enum_open) {
         const int ret_enum = field->GetSelection();
         if (ret_enum < 0 || m_opt.enum_values.empty() || m_opt.type == coStrings ||
             (ret_str != m_opt.enum_values[ret_enum] && ret_str != _(m_opt.enum_labels[ret_enum])))
@@ -1245,6 +1245,8 @@ boost::any& Choice::get_value()
             get_value_by_opt_type(ret_str);
         else if (m_opt.type == coFloatOrPercent)
             m_value = m_opt.enum_values[ret_enum];
+        else if (m_opt.type == coInt)
+            m_value = atoi(m_opt.enum_values[ret_enum].c_str());
         else
             m_value = atof(m_opt.enum_values[ret_enum].c_str());
     }
diff --git a/src/slic3r/GUI/OG_CustomCtrl.cpp b/src/slic3r/GUI/OG_CustomCtrl.cpp
index 6433bf2d1..aba3404e7 100644
--- a/src/slic3r/GUI/OG_CustomCtrl.cpp
+++ b/src/slic3r/GUI/OG_CustomCtrl.cpp
@@ -91,7 +91,7 @@ void OG_CustomCtrl::init_ctrl_lines()
             height = m_bmp_blinking_sz.GetHeight() + m_v_gap;
             ctrl_lines.emplace_back(CtrlLine(height, this, line, true));
         }
-        else if (opt_group->label_width != 0 && (!line.label.IsEmpty() || option_set.front().opt.gui_type == "legend") )
+        else if (opt_group->label_width != 0 && (!line.label.IsEmpty() || option_set.front().opt.gui_type == ConfigOptionDef::GUIType::legend) )
         {
             wxSize label_sz = GetTextExtent(line.label);
             height = label_sz.y * (label_sz.GetWidth() > int(opt_group->label_width * m_em_unit) ? 2 : 1) + m_v_gap;
@@ -186,11 +186,11 @@ wxPoint OG_CustomCtrl::get_pos(const Line& line, Field* field_in/* = nullptr*/)
 #endif //__WXMSW__
                     h_pos += label_w + 1 + m_h_gap;
                 }                
-                h_pos += (opt.opt.gui_type == "legend" ? 1 : 3) * blinking_button_width;
+                h_pos += (opt.opt.gui_type == ConfigOptionDef::GUIType::legend ? 1 : 3) * blinking_button_width;
                 
                 if (field == field_in)
                     break;
-                if (opt.opt.gui_type == "legend")
+                if (opt.opt.gui_type == ConfigOptionDef::GUIType::legend)
                     h_pos += 2 * blinking_button_width;
 
                 h_pos += field->getWindow()->GetSize().x;
@@ -580,7 +580,7 @@ wxCoord OG_CustomCtrl::CtrlLine::draw_mode_bmp(wxDC& dc, wxCoord v_pos)
     wxBitmap bmp = create_scaled_bitmap(bmp_name, ctrl, wxOSX ? 10 : 12);
     wxCoord y_draw = v_pos + lround((height - get_bitmap_size(bmp).GetHeight()) / 2);
 
-    if (og_line.get_options().front().opt.gui_type != "legend")
+    if (og_line.get_options().front().opt.gui_type != ConfigOptionDef::GUIType::legend)
         dc.DrawBitmap(bmp, 0, y_draw);
 
     return get_bitmap_size(bmp).GetWidth() + ctrl->m_h_gap;
diff --git a/src/slic3r/GUI/OptionsGroup.cpp b/src/slic3r/GUI/OptionsGroup.cpp
index b87e2047d..c81f4c644 100644
--- a/src/slic3r/GUI/OptionsGroup.cpp
+++ b/src/slic3r/GUI/OptionsGroup.cpp
@@ -25,23 +25,27 @@ const t_field& OptionsGroup::build_field(const t_config_option_key& id) {
 const t_field& OptionsGroup::build_field(const t_config_option_key& id, const ConfigOptionDef& opt) {
     // Check the gui_type field first, fall through
     // is the normal type.
-    if (opt.gui_type == "select") {
-    } else if (opt.gui_type == "select_open") {
+    switch (opt.gui_type) {
+    case ConfigOptionDef::GUIType::select_open:
         m_fields.emplace(id, Choice::Create<Choice>(this->ctrl_parent(), opt, id));
-    } else if (opt.gui_type == "color") {
+        break;
+    case ConfigOptionDef::GUIType::color:
         m_fields.emplace(id, ColourPicker::Create<ColourPicker>(this->ctrl_parent(), opt, id));
-    } else if (opt.gui_type == "f_enum_open" ||
-                opt.gui_type == "i_enum_open" ||
-                opt.gui_type == "i_enum_closed") {
+        break;
+    case ConfigOptionDef::GUIType::f_enum_open:
+    case ConfigOptionDef::GUIType::i_enum_open:
         m_fields.emplace(id, Choice::Create<Choice>(this->ctrl_parent(), opt, id));
-    } else if (opt.gui_type == "slider") {
+        break;
+    case ConfigOptionDef::GUIType::slider:
         m_fields.emplace(id, SliderCtrl::Create<SliderCtrl>(this->ctrl_parent(), opt, id));
-    } else if (opt.gui_type == "i_spin") { // Spinctrl
-    } else if (opt.gui_type == "legend") { // StaticText
+        break;
+    case ConfigOptionDef::GUIType::legend: // StaticText
         m_fields.emplace(id, StaticText::Create<StaticText>(this->ctrl_parent(), opt, id));
-    } else if (opt.gui_type == "one_string") {
+        break;
+    case ConfigOptionDef::GUIType::one_string:
         m_fields.emplace(id, TextCtrl::Create<TextCtrl>(this->ctrl_parent(), opt, id));
-    } else {
+        break;
+    default:
         switch (opt.type) {
             case coFloatOrPercent:
             case coFloat:
@@ -122,7 +126,7 @@ bool OptionsGroup::is_legend_line()
 {
 	if (m_lines.size() == 1) {
 		const std::vector<Option>& option_set = m_lines.front().get_options();
-		return !option_set.empty() && option_set.front().opt.gui_type == "legend";
+		return !option_set.empty() && option_set.front().opt.gui_type == ConfigOptionDef::GUIType::legend;
 	}
 	return false;
 }
@@ -213,7 +217,7 @@ void OptionsGroup::activate_line(Line& line)
     }
 
 	auto option_set = line.get_options();
-	bool is_legend_line = option_set.front().opt.gui_type == "legend";
+	bool is_legend_line = option_set.front().opt.gui_type == ConfigOptionDef::GUIType::legend;
 
     if (!custom_ctrl && m_use_custom_ctrl) {
         custom_ctrl = new OG_CustomCtrl(is_legend_line || !staticbox ? this->parent() : static_cast<wxWindow*>(this->stb), this);
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index f131c244f..493958589 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -357,7 +357,7 @@ FreqChangedParams::FreqChangedParams(wxWindow* parent) :
     ConfigOptionDef support_def;
     support_def.label = L("Supports");
     support_def.type = coStrings;
-    support_def.gui_type = "select_open";
+    support_def.gui_type = ConfigOptionDef::GUIType::select_open;
     support_def.tooltip = L("Select what kind of support do you need");
     support_def.enum_labels.push_back(L("None"));
     support_def.enum_labels.push_back(L("Support on build plate only"));
@@ -397,7 +397,7 @@ FreqChangedParams::FreqChangedParams(wxWindow* parent) :
     def.label = L("Brim");
     def.type = coBool;
     def.tooltip = L("This flag enables the brim that will be printed around each object on the first layer.");
-    def.gui_type = "";
+    def.gui_type = ConfigOptionDef::GUIType::undefined;
     def.set_default_value(new ConfigOptionBool{ m_brim_width > 0.0 ? true : false });
     option = Option(def, "brim");
     option.opt.sidetext = "";
@@ -500,7 +500,7 @@ FreqChangedParams::FreqChangedParams(wxWindow* parent) :
     ConfigOptionDef pad_def;
     pad_def.label = L("Pad");
     pad_def.type = coStrings;
-    pad_def.gui_type = "select_open";
+    pad_def.gui_type = ConfigOptionDef::GUIType::select_open;
     pad_def.tooltip = L("Select what kind of pad do you need");
     pad_def.enum_labels.push_back(L("None"));
     pad_def.enum_labels.push_back(L("Below object"));
diff --git a/src/slic3r/GUI/Tab.cpp b/src/slic3r/GUI/Tab.cpp
index 7b3f23eb4..6f7a21fcc 100644
--- a/src/slic3r/GUI/Tab.cpp
+++ b/src/slic3r/GUI/Tab.cpp
@@ -2531,7 +2531,7 @@ PageShp TabPrinter::build_kinematics_page()
         ConfigOptionDef def;
         def.type = coString;
         def.width = Field::def_width();
-        def.gui_type = "legend";
+        def.gui_type = ConfigOptionDef::GUIType::legend;
         def.mode = comAdvanced;
         def.tooltip = L("Values in this column are for Normal mode");
         def.set_default_value(new ConfigOptionString{ _(L("Normal")).ToUTF8().data() });
diff --git a/src/slic3r/Utils/Platform.cpp b/src/slic3r/Utils/Platform.cpp
index d30f30fc8..cf9131ef5 100644
--- a/src/slic3r/Utils/Platform.cpp
+++ b/src/slic3r/Utils/Platform.cpp
@@ -30,7 +30,7 @@ void detect_platform()
 			char buf[4096];
 			// Read the 1st line.
 			if (::fgets(buf, 4096, f) && strstr(buf, "Chromium OS") != nullptr)
-				s_platform_flavor = LinuxOnChromium;
+				s_platform_flavor = PlatformFlavor::LinuxOnChromium;
 			::fclose(f);
 		}
 	}
diff --git a/xs/xsp/Config.xsp b/xs/xsp/Config.xsp
index b8f996797..d8b60bc84 100644
--- a/xs/xsp/Config.xsp
+++ b/xs/xsp/Config.xsp
@@ -170,19 +170,6 @@ print_config_def()
                 throw "Unknown option type";
             }
             (void)hv_stores( hv, "type",        newSVpv(opt_type, 0) );
-            (void)hv_stores( hv, "gui_type",    newSVpvn(optdef->gui_type.c_str(), optdef->gui_type.length()) );
-            (void)hv_stores( hv, "gui_flags",   newSVpvn(optdef->gui_flags.c_str(), optdef->gui_flags.length()) );
-            (void)hv_stores( hv, "label",       newSVpvn_utf8(optdef->label.c_str(), optdef->label.length(), true) );
-            if (!optdef->full_label.empty())
-                (void)hv_stores( hv, "full_label",  newSVpvn_utf8(optdef->full_label.c_str(), optdef->full_label.length(), true) );
-            (void)hv_stores( hv, "category",    newSVpvn_utf8(optdef->category.c_str(), optdef->category.length(), true) );
-            (void)hv_stores( hv, "tooltip",     newSVpvn_utf8(optdef->tooltip.c_str(), optdef->tooltip.length(), true) );
-            (void)hv_stores( hv, "sidetext",    newSVpvn_utf8(optdef->sidetext.c_str(), optdef->sidetext.length(), true) );
-            (void)hv_stores( hv, "cli",         newSVpvn(optdef->cli.c_str(), optdef->cli.length()) );
-            (void)hv_stores( hv, "ratio_over",  newSVpvn(optdef->ratio_over.c_str(), optdef->ratio_over.length()) );
-            (void)hv_stores( hv, "multiline",   newSViv(optdef->multiline ? 1 : 0) );
-            (void)hv_stores( hv, "full_width",  newSViv(optdef->full_width ? 1 : 0) );
-            (void)hv_stores( hv, "readonly",    newSViv(optdef->readonly ? 1 : 0) );
             (void)hv_stores( hv, "height",      newSViv(optdef->height) );
             (void)hv_stores( hv, "width",       newSViv(optdef->width) );
             (void)hv_stores( hv, "min",         newSViv(optdef->min) );