diff --git a/xs/src/slic3r/GUI/Field.cpp b/xs/src/slic3r/GUI/Field.cpp
index a7fd8d29eb..c68b2304c0 100644
--- a/xs/src/slic3r/GUI/Field.cpp
+++ b/xs/src/slic3r/GUI/Field.cpp
@@ -75,13 +75,13 @@ namespace Slic3r { namespace GUI {
 		return tooltip_text;
 	}
 
-	bool Field::is_matched(std::string string, std::string pattern)
+	bool Field::is_matched(const std::string& string, const std::string& pattern)
 	{
 		std::regex regex_pattern(pattern, std::regex_constants::icase); // use ::icase to make the matching case insensitive like /i in perl
 		return std::regex_match(string, regex_pattern);
 	}
 
-	boost::any Field::get_value_by_opt_type(wxString str)
+	boost::any Field::get_value_by_opt_type(wxString& str)
 	{
 		boost::any ret_val;
 		switch (m_opt.type){
@@ -377,7 +377,7 @@ void Choice::set_selection()
 	}
 }
 
-void Choice::set_value(const std::string value, bool change_event)  //! Redundant?
+void Choice::set_value(const std::string& value, bool change_event)  //! Redundant?
 {
 	m_disable_change_event = !change_event;
 
@@ -396,7 +396,7 @@ void Choice::set_value(const std::string value, bool change_event)  //! Redundan
 	m_disable_change_event = false;
 }
 
-void Choice::set_value(boost::any value, bool change_event)
+void Choice::set_value(const boost::any& value, bool change_event)
 {
 	m_disable_change_event = !change_event;
 
@@ -435,7 +435,7 @@ void Choice::set_value(boost::any value, bool change_event)
 }
 
 //! it's needed for _update_serial_ports()
-void Choice::set_values(const std::vector<std::string> values)
+void Choice::set_values(const std::vector<std::string>& values)
 {
 	if (values.empty())
 		return;
@@ -554,7 +554,7 @@ void PointCtrl::BUILD()
 	y_textctrl->SetToolTip(get_tooltip_text(X+", "+Y));
 }
 
-void PointCtrl::set_value(const Pointf value, bool change_event)
+void PointCtrl::set_value(const Pointf& value, bool change_event)
 {
 	m_disable_change_event = !change_event;
 
@@ -566,10 +566,10 @@ void PointCtrl::set_value(const Pointf value, bool change_event)
 	m_disable_change_event = false;
 }
 
-void PointCtrl::set_value(boost::any value, bool change_event)
+void PointCtrl::set_value(const boost::any& value, bool change_event)
 {
 	Pointf pt;
-	Pointf *ptf = boost::any_cast<Pointf>(&value);
+	const Pointf *ptf = boost::any_cast<Pointf>(&value);
 	if (!ptf)
 	{
 		ConfigOptionPoints* pts = boost::any_cast<ConfigOptionPoints*>(value);
@@ -577,21 +577,6 @@ void PointCtrl::set_value(boost::any value, bool change_event)
 	}
 	else
 		pt = *ptf;
-// 	try
-// 	{
-// 		pt = boost::any_cast<ConfigOptionPoints*>(value)->values.at(0);
-// 	}
-// 	catch (const std::exception &e)
-// 	{
-// 		try{
-// 			pt = boost::any_cast<Pointf>(value);
-// 		}
-// 		catch (const std::exception &e)
-// 		{
-// 			std::cerr << "Error! Can't cast PointCtrl value" << m_opt_id << "\n";
-// 			return;
-// 		}		
-// 	}	
 	set_value(pt, change_event);
 }
 
diff --git a/xs/src/slic3r/GUI/Field.hpp b/xs/src/slic3r/GUI/Field.hpp
index da3e23ccd8..cdc7c0d812 100644
--- a/xs/src/slic3r/GUI/Field.hpp
+++ b/xs/src/slic3r/GUI/Field.hpp
@@ -31,8 +31,8 @@ namespace Slic3r { namespace GUI {
 class Field;
 using t_field = std::unique_ptr<Field>;
 using t_kill_focus = std::function<void()>;
-using t_change = std::function<void(t_config_option_key, boost::any)>;
-using t_back_to_init = std::function<void(std::string)>;
+using t_change = std::function<void(t_config_option_key, const boost::any&)>;
+using t_back_to_init = std::function<void(const std::string&)>;
 
 wxString double_to_string(double const value);
 
@@ -81,7 +81,7 @@ public:
     /// Sets a value for this control.
     /// subclasses should overload with a specific version
     /// Postcondition: Method does not fire the on_change event.
-    virtual void		set_value(boost::any value, bool change_event) = 0;
+    virtual void		set_value(const boost::any& value, bool change_event) = 0;
     
     /// Gets a boost::any representing this control.
     /// subclasses should overload with a specific version
@@ -100,7 +100,7 @@ public:
 	virtual wxString	get_tooltip_text(const wxString& default_string);
 
     // set icon to "UndoToSystemValue" button according to an inheritance of preset
-	void set_nonsys_btn_icon(const std::string& icon);
+	void				set_nonsys_btn_icon(const std::string& icon);
 
     Field(const ConfigOptionDef& opt, const t_config_option_key& id) : m_opt(opt), m_opt_id(id) {};
     Field(wxWindow* parent, const ConfigOptionDef& opt, const t_config_option_key& id) : m_parent(parent), m_opt(opt), m_opt_id(id) {};
@@ -109,8 +109,8 @@ public:
     virtual wxSizer*	getSizer()  { return nullptr; }
     virtual wxWindow*	getWindow() { return nullptr; }
 
-	bool		is_matched(std::string string, std::string pattern);
-	boost::any	get_value_by_opt_type(wxString str);
+	bool				is_matched(const std::string& string, const std::string& pattern);
+	boost::any			get_value_by_opt_type(wxString& str);
 
     /// Factory method for generating new derived classes.
     template<class T>
@@ -137,16 +137,17 @@ class TextCtrl : public Field {
 public:
 	TextCtrl(const ConfigOptionDef& opt, const t_config_option_key& id) : Field(opt,  id) {}
 	TextCtrl(wxWindow* parent, const ConfigOptionDef& opt, const t_config_option_key& id) : Field(parent, opt, id) {}
+	~TextCtrl() {}
 
     void BUILD();
     wxWindow* window {nullptr};
 
-    virtual void	set_value(std::string value, bool change_event = false) {
+    virtual void	set_value(const std::string& value, bool change_event = false) {
 		m_disable_change_event = !change_event;
         dynamic_cast<wxTextCtrl*>(window)->SetValue(wxString(value));
 		m_disable_change_event = false;
     }
-    virtual void	set_value(boost::any value, bool change_event = false) {
+	virtual void	set_value(const boost::any& value, bool change_event = false) {
 		m_disable_change_event = !change_event;
 		dynamic_cast<wxTextCtrl*>(window)->SetValue(boost::any_cast<wxString>(value));
 		m_disable_change_event = false;
@@ -164,6 +165,7 @@ class CheckBox : public Field {
 public:
 	CheckBox(const ConfigOptionDef& opt, const t_config_option_key& id) : Field(opt, id) {}
 	CheckBox(wxWindow* parent, const ConfigOptionDef& opt, const t_config_option_key& id) : Field(parent, opt, id) {}
+	~CheckBox() {}
 
 	wxWindow*		window{ nullptr };
 	void			BUILD() override;
@@ -173,7 +175,7 @@ public:
 		dynamic_cast<wxCheckBox*>(window)->SetValue(value);
 		m_disable_change_event = false;
 	}
-	void			set_value(boost::any value, bool change_event = false) {
+	void			set_value(const boost::any& value, bool change_event = false) {
 		m_disable_change_event = !change_event;
 		dynamic_cast<wxCheckBox*>(window)->SetValue(boost::any_cast<bool>(value));
 		m_disable_change_event = false;
@@ -190,21 +192,22 @@ class SpinCtrl : public Field {
 public:
 	SpinCtrl(const ConfigOptionDef& opt, const t_config_option_key& id) : Field(opt, id), tmp_value(-9999) {}
 	SpinCtrl(wxWindow* parent, const ConfigOptionDef& opt, const t_config_option_key& id) : Field(parent, opt, id), tmp_value(-9999) {}
+	~SpinCtrl() {}
 
 	int				tmp_value;
 
 	wxWindow*		window{ nullptr };
 	void			BUILD() override;
 
-	void			set_value(const std::string value, bool change_event = false) {
+	void			set_value(const std::string& value, bool change_event = false) {
 		m_disable_change_event = !change_event;
 		dynamic_cast<wxSpinCtrl*>(window)->SetValue(value);
 		m_disable_change_event = false;
 	}
-	void			set_value(boost::any value, bool change_event = false) {
+	void			set_value(const boost::any& value, bool change_event = false) {
 		m_disable_change_event = !change_event;
 		tmp_value = boost::any_cast<int>(value);
-		dynamic_cast<wxSpinCtrl*>(window)->SetValue(tmp_value/*boost::any_cast<int>(value)*/);
+		dynamic_cast<wxSpinCtrl*>(window)->SetValue(tmp_value);
 		m_disable_change_event = false;
 	}
 	boost::any		get_value() override {
@@ -221,14 +224,15 @@ class Choice : public Field {
 public:
 	Choice(const ConfigOptionDef& opt, const t_config_option_key& id) : Field(opt, id) {}
 	Choice(wxWindow* parent, const ConfigOptionDef& opt, const t_config_option_key& id) : Field(parent, opt, id) {}
+	~Choice() {}
 
 	wxWindow*		window{ nullptr };
 	void			BUILD() override;
 
 	void			set_selection();
-	void			set_value(const std::string value, bool change_event = false);
-	void			set_value(boost::any value, bool change_event = false);
-	void			set_values(const std::vector<std::string> values);
+	void			set_value(const std::string& value, bool change_event = false);
+	void			set_value(const boost::any& value, bool change_event = false);
+	void			set_values(const std::vector<std::string> &values);
 	boost::any		get_value() override;
 
 	void			enable() override { dynamic_cast<wxComboBox*>(window)->Enable(); };
@@ -241,16 +245,17 @@ class ColourPicker : public Field {
 public:
 	ColourPicker(const ConfigOptionDef& opt, const t_config_option_key& id) : Field(opt, id) {}
 	ColourPicker(wxWindow* parent, const ConfigOptionDef& opt, const t_config_option_key& id) : Field(parent, opt, id) {}
+	~ColourPicker() {}
 
 	wxWindow*		window{ nullptr };
 	void			BUILD()  override;
 
-	void			set_value(const std::string value, bool change_event = false) {
+	void			set_value(const std::string& value, bool change_event = false) {
 		m_disable_change_event = !change_event;
 		dynamic_cast<wxColourPickerCtrl*>(window)->SetColour(value);
 		m_disable_change_event = false;
 	 	}
-	void			set_value(boost::any value, bool change_event = false) {
+	void			set_value(const boost::any& value, bool change_event = false) {
 		m_disable_change_event = !change_event;
 		dynamic_cast<wxColourPickerCtrl*>(window)->SetColour(boost::any_cast<wxString>(value));
 		m_disable_change_event = false;
@@ -268,23 +273,24 @@ class PointCtrl : public Field {
 public:
 	PointCtrl(const ConfigOptionDef& opt, const t_config_option_key& id) : Field(opt, id) {}
 	PointCtrl(wxWindow* parent, const ConfigOptionDef& opt, const t_config_option_key& id) : Field(parent, opt, id) {}
+	~PointCtrl() {}
 
 	wxSizer*		sizer{ nullptr };
-	wxTextCtrl*		x_textctrl;
-	wxTextCtrl*		y_textctrl;
+	wxTextCtrl*		x_textctrl{ nullptr };
+	wxTextCtrl*		y_textctrl{ nullptr };
 
 	void			BUILD()  override;
 
-	void			set_value(const Pointf value, bool change_event = false);
-	void			set_value(boost::any value, bool change_event = false);
+	void			set_value(const Pointf& value, bool change_event = false);
+	void			set_value(const boost::any& value, bool change_event = false);
 	boost::any		get_value() override;
 
 	void			enable() override {
 		x_textctrl->Enable();
-		y_textctrl->Enable(); };
+		y_textctrl->Enable(); }
 	void			disable() override{
 		x_textctrl->Disable();
-		y_textctrl->Disable(); };
+		y_textctrl->Disable(); }
 	wxSizer*		getSizer() override { return sizer; }
 };
 
diff --git a/xs/src/slic3r/GUI/GUI.cpp b/xs/src/slic3r/GUI/GUI.cpp
index 9450f44ae1..794e873d55 100644
--- a/xs/src/slic3r/GUI/GUI.cpp
+++ b/xs/src/slic3r/GUI/GUI.cpp
@@ -403,7 +403,7 @@ TabIface* get_preset_tab_iface(char *name)
 }
 
 // opt_index = 0, by the reason of zero-index in ConfigOptionVector by default (in case only one element)
-void change_opt_value(DynamicPrintConfig& config, t_config_option_key opt_key, boost::any value, int opt_index /*= 0*/)
+void change_opt_value(DynamicPrintConfig& config, const t_config_option_key& opt_key, const boost::any& value, int opt_index /*= 0*/)
 {
 	try{
 		switch (config.def()->get(opt_key)->type){
@@ -439,11 +439,18 @@ void change_opt_value(DynamicPrintConfig& config, t_config_option_key opt_key, b
 			config.set_key_value(opt_key, new ConfigOptionString(boost::any_cast<std::string>(value)));
 			break;
 		case coStrings:{
-			if (opt_key.compare("compatible_printers") == 0 ||
-				config.def()->get(opt_key)->gui_flags.compare("serialized") == 0){
-				config.option<ConfigOptionStrings>(opt_key)->values.resize(0);
-				std::vector<std::string> values = boost::any_cast<std::vector<std::string>>(value);
-				if (values.size() == 1 && values[0] == "")
+			if (opt_key.compare("compatible_printers") == 0) {
+				config.option<ConfigOptionStrings>(opt_key)->values = 
+					boost::any_cast<std::vector<std::string>>(value);
+			}
+			else if (config.def()->get(opt_key)->gui_flags.compare("serialized") == 0){
+				std::string str = boost::any_cast<std::string>(value);
+				if (str.back() == ';') str.pop_back();
+				// Split a string to multiple strings by a semi - colon.This is the old way of storing multi - string values.
+				// Currently used for the post_process config value only.
+				std::vector<std::string> values;
+				boost::split(values, str, boost::is_any_of(";"));
+				if (values.size() == 1 && values[0] == "") 
 					break;
 				config.option<ConfigOptionStrings>(opt_key)->values = values;
 			}
@@ -510,17 +517,17 @@ void add_created_tab(Tab* panel)
 	g_wxTabPanel->AddPage(panel, panel->title());
 }
 
-void show_error(wxWindow* parent, wxString message){
+void show_error(wxWindow* parent, const wxString& message){
 	auto msg_wingow = new wxMessageDialog(parent, message, _(L("Error")), wxOK | wxICON_ERROR);
 	msg_wingow->ShowModal();
 }
 
-void show_info(wxWindow* parent, wxString message, wxString title){
+void show_info(wxWindow* parent, const wxString& message, const wxString& title){
 	auto msg_wingow = new wxMessageDialog(parent, message, title.empty() ? _(L("Notice")) : title, wxOK | wxICON_INFORMATION);
 	msg_wingow->ShowModal();
 }
 
-void warning_catcher(wxWindow* parent, wxString message){
+void warning_catcher(wxWindow* parent, const wxString& message){
 	if (message == _(L("GLUquadricObjPtr | Attempt to free unreferenced scalar")) )
 		return;
 	auto msg = new wxMessageDialog(parent, message, _(L("Warning")), wxOK | wxICON_WARNING);
diff --git a/xs/src/slic3r/GUI/GUI.hpp b/xs/src/slic3r/GUI/GUI.hpp
index 24c3ec3f40..d92246c500 100644
--- a/xs/src/slic3r/GUI/GUI.hpp
+++ b/xs/src/slic3r/GUI/GUI.hpp
@@ -96,11 +96,11 @@ TabIface* get_preset_tab_iface(char *name);
 // add it at the end of the tab panel.
 void add_created_tab(Tab* panel);
 // Change option value in config
-void change_opt_value(DynamicPrintConfig& config, t_config_option_key opt_key, boost::any value, int opt_index = 0);
+void change_opt_value(DynamicPrintConfig& config, const t_config_option_key& opt_key, const boost::any& value, int opt_index = 0);
 
-void show_error(wxWindow* parent, wxString message);
-void show_info(wxWindow* parent, wxString message, wxString title);
-void warning_catcher(wxWindow* parent, wxString message);
+void show_error(wxWindow* parent, const wxString& message);
+void show_info(wxWindow* parent, const wxString& message, const wxString& title);
+void warning_catcher(wxWindow* parent, const wxString& message);
 
 // load language saved at application config 
 bool load_language();
diff --git a/xs/src/slic3r/GUI/OptionsGroup.cpp b/xs/src/slic3r/GUI/OptionsGroup.cpp
index 24e1ddf2eb..8e22689652 100644
--- a/xs/src/slic3r/GUI/OptionsGroup.cpp
+++ b/xs/src/slic3r/GUI/OptionsGroup.cpp
@@ -227,12 +227,12 @@ Line OptionsGroup::create_single_option_line(const Option& option) const {
     return retval;
 }
 
-void OptionsGroup::on_change_OG(t_config_option_key id, /*config_value*/boost::any value) {
+void OptionsGroup::on_change_OG(const t_config_option_key& opt_id, const boost::any& value) {
 	if (m_on_change != nullptr)
-		m_on_change(id, value);
+		m_on_change(opt_id, value);
 }
 
-Option ConfigOptionsGroup::get_option(const std::string opt_key, int opt_index /*= -1*/)
+Option ConfigOptionsGroup::get_option(const std::string& opt_key, int opt_index /*= -1*/)
 {
 	if (!m_config->has(opt_key)) {
 		std::cerr << "No " << opt_key << " in ConfigOptionsGroup config.";
@@ -245,7 +245,7 @@ Option ConfigOptionsGroup::get_option(const std::string opt_key, int opt_index /
 	return Option(*m_config->def()->get(opt_key), opt_id);
 }
 
-void ConfigOptionsGroup::on_change_OG(t_config_option_key opt_id, boost::any value)
+void ConfigOptionsGroup::on_change_OG(const t_config_option_key& opt_id, const boost::any& value)
 {
 	if (!m_opt_map.empty())
 	{
@@ -268,16 +268,7 @@ void ConfigOptionsGroup::on_change_OG(t_config_option_key opt_id, boost::any val
 			if (opt_index != -1){
 				// 		die "Can't set serialized option indexed value" ;
 			}
-			// 		# Split a string to multiple strings by a semi - colon.This is the old way of storing multi - string values.
-			// 		# Currently used for the post_process config value only.
-			// 		my @values = split / ; / , $field_value;
-			// 		$self->config->set($opt_key, \@values);
-			std::string str = boost::any_cast<std::string>(value);
-			if (str.back() == ';')
-				str.pop_back();
-			std::vector<std::string> values;
-			boost::split(values, str, boost::is_any_of(";"));
-			change_opt_value(*m_config, opt_key, values);
+			change_opt_value(*m_config, opt_key, value);
 		}
 		else {
 			if (opt_index == -1) {
@@ -297,14 +288,14 @@ void ConfigOptionsGroup::on_change_OG(t_config_option_key opt_id, boost::any val
 	OptionsGroup::on_change_OG(opt_id, value); //!? Why doing this
 }
 
-void ConfigOptionsGroup::back_to_initial_value(const std::string opt_key)
+void ConfigOptionsGroup::back_to_initial_value(const std::string& opt_key)
 {
 	if (m_get_initial_config == nullptr)
 		return;
 	back_to_config_value(m_get_initial_config(), opt_key);
 }
 
-void ConfigOptionsGroup::back_to_sys_value(const std::string opt_key)
+void ConfigOptionsGroup::back_to_sys_value(const std::string& opt_key)
 {
 	if (m_get_sys_config == nullptr)
 		return;
@@ -313,7 +304,7 @@ void ConfigOptionsGroup::back_to_sys_value(const std::string opt_key)
 	back_to_config_value(m_get_sys_config(), opt_key);
 }
 
-void ConfigOptionsGroup::back_to_config_value(const DynamicPrintConfig& config, const std::string opt_key)
+void ConfigOptionsGroup::back_to_config_value(const DynamicPrintConfig& config, const std::string& opt_key)
 {
 	boost::any value;
 	if (opt_key == "extruders_count"){
@@ -348,7 +339,7 @@ void ConfigOptionsGroup::reload_config(){
 
 }
 
-boost::any ConfigOptionsGroup::config_value(std::string opt_key, int opt_index, bool deserialize){
+boost::any ConfigOptionsGroup::config_value(const std::string& opt_key, int opt_index, bool deserialize){
 
 	if (deserialize) {
 		// Want to edit a vector value(currently only multi - strings) in a single edit box.
@@ -365,7 +356,7 @@ boost::any ConfigOptionsGroup::config_value(std::string opt_key, int opt_index,
 	}
 }
 
-boost::any ConfigOptionsGroup::get_config_value(const DynamicPrintConfig& config, std::string opt_key, int opt_index /*= -1*/)
+boost::any ConfigOptionsGroup::get_config_value(const DynamicPrintConfig& config, const std::string& opt_key, int opt_index /*= -1*/)
 {
 	size_t idx = opt_index == -1 ? 0 : opt_index;
 	
@@ -457,7 +448,7 @@ boost::any ConfigOptionsGroup::get_config_value(const DynamicPrintConfig& config
 	return ret;
 }
 
-Field* ConfigOptionsGroup::get_fieldc(t_config_option_key opt_key, int opt_index){
+Field* ConfigOptionsGroup::get_fieldc(const t_config_option_key& opt_key, int opt_index){
 	Field* field = get_field(opt_key);
 	if (field != nullptr)
 		return field;
@@ -471,7 +462,7 @@ Field* ConfigOptionsGroup::get_fieldc(t_config_option_key opt_key, int opt_index
 	return opt_id.empty() ? nullptr : get_field(opt_id);
 }
 
-void ogStaticText::SetText(wxString value)
+void ogStaticText::SetText(const wxString& value)
 {
 	SetLabel(value);
 	Wrap(400);
diff --git a/xs/src/slic3r/GUI/OptionsGroup.hpp b/xs/src/slic3r/GUI/OptionsGroup.hpp
index e58d9c9a99..b5846f24d7 100644
--- a/xs/src/slic3r/GUI/OptionsGroup.hpp
+++ b/xs/src/slic3r/GUI/OptionsGroup.hpp
@@ -98,16 +98,16 @@ public:
     void		append_single_option_line(const Option& option) { append_line(create_single_option_line(option)); }
 
     // return a non-owning pointer reference 
-    inline Field*	get_field(t_config_option_key id) const{
+    inline Field*	get_field(const t_config_option_key& id) const{
 							if (m_fields.find(id) == m_fields.end()) return nullptr;
 							return m_fields.at(id).get();
     }
-	bool			set_value(t_config_option_key id, boost::any value, bool change_event = false) {
+	bool			set_value(const t_config_option_key& id, const boost::any& value, bool change_event = false) {
 							if (m_fields.find(id) == m_fields.end()) return false;
 							m_fields.at(id)->set_value(value, change_event);
 							return true;
     }
-	boost::any		get_value(t_config_option_key id) {
+	boost::any		get_value(const t_config_option_key& id) {
 							boost::any out; 
     						if (m_fields.find(id) == m_fields.end()) ;
 							else 
@@ -118,7 +118,7 @@ public:
 	inline void		enable() { for (auto& field : m_fields) field.second->enable(); }
     inline void		disable() { for (auto& field : m_fields) field.second->disable(); }
 
-    OptionsGroup(wxWindow* _parent, wxString title, bool is_tab_opt=false) : 
+    OptionsGroup(wxWindow* _parent, const wxString& title, bool is_tab_opt=false) : 
 		m_parent(_parent), title(title), m_is_tab_opt(is_tab_opt), staticbox(title!="") {
         sizer = (staticbox ? new wxStaticBoxSizer(new wxStaticBox(_parent, wxID_ANY, title), wxVERTICAL) : new wxBoxSizer(wxVERTICAL));
         auto num_columns = 1U;
@@ -152,14 +152,14 @@ protected:
 	const t_field&		build_field(const Option& opt, wxStaticText* label = nullptr);
 
     virtual void		on_kill_focus (){};
-	virtual void		on_change_OG(t_config_option_key opt_id, boost::any value);
-	virtual void		back_to_initial_value(const std::string opt_key){};
-	virtual void		back_to_sys_value(const std::string opt_key){};
+	virtual void		on_change_OG(const t_config_option_key& opt_id, const boost::any& value);
+	virtual void		back_to_initial_value(const std::string& opt_key){}
+	virtual void		back_to_sys_value(const std::string& opt_key){}
 };
 
 class ConfigOptionsGroup: public OptionsGroup {
 public:
-	ConfigOptionsGroup(wxWindow* parent, wxString title, DynamicPrintConfig* _config = nullptr, bool is_tab_opt = false) :
+	ConfigOptionsGroup(wxWindow* parent, const wxString& title, DynamicPrintConfig* _config = nullptr, bool is_tab_opt = false) :
 		OptionsGroup(parent, title, is_tab_opt), m_config(_config) {}
 
     /// reference to libslic3r config, non-owning pointer (?).
@@ -167,8 +167,8 @@ public:
     bool					m_full_labels {0};
 	t_opt_map				m_opt_map;
 
-	Option		get_option(const std::string opt_key, int opt_index = -1);
-	Line		create_single_option_line(const std::string title, int idx = -1) /*const*/{
+	Option		get_option(const std::string& opt_key, int opt_index = -1);
+	Line		create_single_option_line(const std::string& title, int idx = -1) /*const*/{
 		Option option = get_option(title, idx);
 		return OptionsGroup::create_single_option_line(option);
 	}
@@ -181,16 +181,16 @@ public:
 		append_single_option_line(option);		
 	}
 
-	void		on_change_OG(t_config_option_key opt_id, boost::any value) override;
-	void		back_to_initial_value(const std::string opt_key) override;
-	void		back_to_sys_value(const std::string opt_key) override;
-	void back_to_config_value(const DynamicPrintConfig& config, const std::string opt_key);
+	void		on_change_OG(const t_config_option_key& opt_id, const boost::any& value) override;
+	void		back_to_initial_value(const std::string& opt_key) override;
+	void		back_to_sys_value(const std::string& opt_key) override;
+	void		back_to_config_value(const DynamicPrintConfig& config, const std::string& opt_key);
 	void		on_kill_focus() override{ reload_config();}
 	void		reload_config();
-	boost::any	config_value(std::string opt_key, int opt_index, bool deserialize);
+	boost::any	config_value(const std::string& opt_key, int opt_index, bool deserialize);
 	// return option value from config 
-	boost::any get_config_value(const DynamicPrintConfig& config, std::string opt_key, int opt_index = -1);
-	Field*		get_fieldc(t_config_option_key opt_key, int opt_index);
+	boost::any	get_config_value(const DynamicPrintConfig& config, const std::string& opt_key, int opt_index = -1);
+	Field*		get_fieldc(const t_config_option_key& opt_key, int opt_index);
 };
 
 //  Static text shown among the options.
@@ -200,7 +200,7 @@ public:
 	ogStaticText(wxWindow* parent, const char *text) : wxStaticText(parent, wxID_ANY, text, wxDefaultPosition, wxDefaultSize){}
 	~ogStaticText(){}
 
-	void SetText(wxString value);
+	void		SetText(const wxString& value);
 };
 
 }}
diff --git a/xs/src/slic3r/GUI/Tab.cpp b/xs/src/slic3r/GUI/Tab.cpp
index ebcd4af882..a9faf4c591 100644
--- a/xs/src/slic3r/GUI/Tab.cpp
+++ b/xs/src/slic3r/GUI/Tab.cpp
@@ -203,11 +203,10 @@ void Tab::load_initial_data()
 {
 	m_config = &m_presets->get_edited_preset().config;
 	m_nonsys_btn_icon = m_presets->get_selected_preset_parent() == nullptr ?
-		"bullet_white.png" : "sys_unlock.png";
-// 		wxMSW ? "sys_unlock.png" : "lock_open.png";
+						"bullet_white.png" : "sys_unlock.png";
 }
 
-PageShp Tab::add_options_page(wxString title, std::string icon, bool is_extruder_pages/* = false*/)
+PageShp Tab::add_options_page(const wxString& title, const std::string& icon, bool is_extruder_pages/* = false*/)
 {
 	// Index of icon in an icon list $self->{icons}.
 	auto icon_idx = 0;
@@ -332,8 +331,8 @@ void Tab::update_changed_ui()
 	{
 		bool is_nonsys_value = false;
 		bool is_modified_value = true;
-		std::string sys_icon = /*wxMSW ? */"sys_lock.png"/* : "lock.png"*/;
-		std::string icon = /*wxMSW ? */"action_undo.png"/* : "arrow_undo.png"*/;
+		std::string sys_icon = "sys_lock.png";
+		std::string icon = "action_undo.png";
 		wxColour color = get_sys_label_clr();
 		if (find(m_sys_options.begin(), m_sys_options.end(), opt_key) == m_sys_options.end()) {
 			is_nonsys_value = true;
@@ -478,10 +477,8 @@ void Tab::update_changed_tree_ui()
 
 void Tab::update_undo_buttons()
 {
-	const std::string& undo_icon = !m_is_modified_values ? "bullet_white.png" :
-									/*wxMSW ? */"action_undo.png"/* : "arrow_undo.png"*/;
-	const std::string& undo_to_sys_icon = m_is_nonsys_values ? m_nonsys_btn_icon :
-									/*wxMSW ? */"sys_lock.png"/* : "lock.png"*/;
+	const std::string& undo_icon = !m_is_modified_values ? "bullet_white.png" : "action_undo.png";
+	const std::string& undo_to_sys_icon = m_is_nonsys_values ? m_nonsys_btn_icon : "sys_lock.png";
 
 	m_undo_btn->SetBitmap(wxBitmap(from_u8(var(undo_icon)), wxBITMAP_TYPE_PNG));
 	m_undo_to_sys_btn->SetBitmap(wxBitmap(from_u8(var(undo_to_sys_icon)), wxBITMAP_TYPE_PNG));
@@ -559,7 +556,7 @@ void Tab::update_tab_ui()
 
 // Load a provied DynamicConfig into the tab, modifying the active preset.
 // This could be used for example by setting a Wipe Tower position by interactive manipulation in the 3D view.
-void Tab::load_config(DynamicPrintConfig config)
+void Tab::load_config(const DynamicPrintConfig& config)
 {
 	bool modified = 0;
 	for(auto opt_key : m_config->diff(config)) {
@@ -582,7 +579,7 @@ void Tab::reload_config(){
  	Thaw();
 }
 
-Field* Tab::get_field(t_config_option_key opt_key, int opt_index/* = -1*/) const
+Field* Tab::get_field(const t_config_option_key& opt_key, int opt_index/* = -1*/) const
 {
 	Field* field = nullptr;
 	for (auto page : m_pages){
@@ -596,7 +593,7 @@ Field* Tab::get_field(t_config_option_key opt_key, int opt_index/* = -1*/) const
 // Set a key/value pair on this page. Return true if the value has been modified.
 // Currently used for distributing extruders_count over preset pages of Slic3r::GUI::Tab::Printer
 // after a preset is loaded.
-bool Tab::set_value(t_config_option_key opt_key, boost::any value){
+bool Tab::set_value(const t_config_option_key& opt_key, const boost::any& value){
 	bool changed = false;
 	for(auto page: m_pages) {
 		if (page->set_value(opt_key, value))
@@ -607,7 +604,7 @@ bool Tab::set_value(t_config_option_key opt_key, boost::any value){
 
 // To be called by custom widgets, load a value into a config,
 // update the preset selection boxes (the dirty flags)
-void Tab::load_key_value(std::string opt_key, boost::any value)
+void Tab::load_key_value(const std::string& opt_key, const boost::any& value)
 {
 	change_opt_value(*m_config, opt_key, value);
 	// Mark the print & filament enabled if they are compatible with the currently selected preset.
@@ -621,7 +618,7 @@ void Tab::load_key_value(std::string opt_key, boost::any value)
 
 extern wxFrame *g_wxMainFrame;
 
-void Tab::on_value_change(std::string opt_key, boost::any value)
+void Tab::on_value_change(const std::string& opt_key, const boost::any& value)
 {
 	if (m_event_value_change > 0) {
 		wxCommandEvent event(m_event_value_change);
@@ -636,8 +633,8 @@ void Tab::on_value_change(std::string opt_key, boost::any value)
 	}
 	if (opt_key == "fill_density")
 	{
-		value = get_optgroup()->get_config_value(*m_config, opt_key);
-		get_optgroup()->set_value(opt_key, value);
+		boost::any val = get_optgroup()->get_config_value(*m_config, opt_key);
+		get_optgroup()->set_value(opt_key, val);
 	}
 	if (opt_key == "support_material" || opt_key == "support_material_buildplate_only")
 	{
@@ -1785,9 +1782,7 @@ void Tab::load_current_preset()
 	// Reload preset pages with the new configuration values.
 	reload_config();
 	const Preset* parent = m_presets->get_selected_preset_parent();
-	m_nonsys_btn_icon = parent == nullptr ?
-		"bullet_white.png" :
-		/*wxMSW ? */"sys_unlock.png"/* : "lock_open.png"*/;
+	m_nonsys_btn_icon = parent == nullptr ? "bullet_white.png" : "sys_unlock.png";
 
 	// use CallAfter because some field triggers schedule on_change calls using CallAfter,
 	// and we don't want them to be called after this update_dirty() as they would mark the 
@@ -1844,7 +1839,7 @@ void Tab::rebuild_page_tree()
 // Called by the UI combo box when the user switches profiles.
 // Select a preset by a name.If !defined(name), then the default preset is selected.
 // If the current profile is modified, user is asked to save the changes.
-void Tab::select_preset(std::string preset_name /*= ""*/)
+void Tab::select_preset(const std::string& preset_name /*= ""*/)
 {
 	std::string name = preset_name;
 	auto force = false;
@@ -1911,7 +1906,7 @@ void Tab::select_preset(std::string preset_name /*= ""*/)
 
 // If the current preset is dirty, the user is asked whether the changes may be discarded.
 // if the current preset was not dirty, or the user agreed to discard the changes, 1 is returned.
-bool Tab::may_discard_current_dirty_preset(PresetCollection* presets /*= nullptr*/, std::string new_printer_name /*= ""*/)
+bool Tab::may_discard_current_dirty_preset(PresetCollection* presets /*= nullptr*/, const std::string& new_printer_name /*= ""*/)
 {
 	if (presets == nullptr) presets = m_presets;
 	// Display a dialog showing the dirty options in a human readable form.
@@ -2339,7 +2334,7 @@ void Page::reload_config()
 		group->reload_config();
 }
 
-Field* Page::get_field(t_config_option_key opt_key, int opt_index/* = -1*/) const
+Field* Page::get_field(const t_config_option_key& opt_key, int opt_index /*= -1*/) const
 {
 	Field* field = nullptr;
 	for (auto opt : m_optgroups){
@@ -2350,7 +2345,7 @@ Field* Page::get_field(t_config_option_key opt_key, int opt_index/* = -1*/) cons
 	return field;
 }
 
-bool Page::set_value(t_config_option_key opt_key, boost::any value){
+bool Page::set_value(const t_config_option_key& opt_key, const boost::any& value){
 	bool changed = false;
 	for(auto optgroup: m_optgroups) {
 		if (optgroup->set_value(opt_key, value))
@@ -2360,7 +2355,7 @@ bool Page::set_value(t_config_option_key opt_key, boost::any value){
 }
 
 // package Slic3r::GUI::Tab::Page;
-ConfigOptionsGroupShp Page::new_optgroup(wxString title, int noncommon_label_width /*= -1*/)
+ConfigOptionsGroupShp Page::new_optgroup(const wxString& title, int noncommon_label_width /*= -1*/)
 {
 	//! config_ have to be "right"
 	ConfigOptionsGroupShp optgroup = std::make_shared<ConfigOptionsGroup>(this, title, m_config, true);
@@ -2401,7 +2396,7 @@ ConfigOptionsGroupShp Page::new_optgroup(wxString title, int noncommon_label_wid
 	return optgroup;
 }
 
-void SavePresetWindow::build(wxString title, std::string default_name, std::vector<std::string> &values)
+void SavePresetWindow::build(const wxString& title, const std::string& default_name, std::vector<std::string> &values)
 {
 	auto text = new wxStaticText(this, wxID_ANY, _(L("Save ")) + title + _(L(" as:")), 
 									wxDefaultPosition, wxDefaultSize);
diff --git a/xs/src/slic3r/GUI/Tab.hpp b/xs/src/slic3r/GUI/Tab.hpp
index 8a2c38e052..9465f86b47 100644
--- a/xs/src/slic3r/GUI/Tab.hpp
+++ b/xs/src/slic3r/GUI/Tab.hpp
@@ -68,9 +68,9 @@ public:
 	size_t		iconID() const { return m_iconID; }
 	void		set_config(DynamicPrintConfig* config_in) { m_config = config_in; }
 	void		reload_config();
-	Field*		get_field(t_config_option_key opt_key, int opt_index = -1) const;
-	bool		set_value(t_config_option_key opt_key, boost::any value);
-	ConfigOptionsGroupShp	new_optgroup(wxString title, int noncommon_label_width = -1);
+	Field*		get_field(const t_config_option_key& opt_key, int opt_index = -1) const;
+	bool		set_value(const t_config_option_key& opt_key, const boost::any& value);
+	ConfigOptionsGroupShp	new_optgroup(const wxString& title, int noncommon_label_width = -1);
 };
 
 // Slic3r::GUI::Tab;
@@ -129,7 +129,7 @@ public:
 
 public:
 	Tab() {}
-	Tab(wxNotebook* parent, wxString title, const char* name, bool no_controller) : 
+	Tab(wxNotebook* parent, const wxString& title, const char* name, bool no_controller) : 
 		m_parent(parent), m_title(title), m_name(name), m_no_controller(no_controller) {
 		Create(parent, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxBK_LEFT | wxTAB_TRAVERSAL);
 		get_tabs_list().push_back(this);
@@ -147,12 +147,12 @@ public:
 	void		create_preset_tab(PresetBundle *preset_bundle);
 	void		load_current_preset();
 	void		rebuild_page_tree();
-	void		select_preset(std::string preset_name = "");
-	bool		may_discard_current_dirty_preset(PresetCollection* presets = nullptr, std::string new_printer_name = "");
+	void		select_preset(const std::string& preset_name = "");
+	bool		may_discard_current_dirty_preset(PresetCollection* presets = nullptr, const std::string& new_printer_name = "");
 	wxSizer*	compatible_printers_widget(wxWindow* parent, wxCheckBox** checkbox, wxButton** btn);
 
 	void		update_presetsctrl(wxDataViewTreeCtrl* ui, bool show_incompatible);
-	void		load_key_value(std::string opt_key, boost::any value);
+	void		load_key_value(const std::string& opt_key, const boost::any& value);
 	void		reload_compatible_printers_widget();
 
 	void		OnTreeSelChange(wxTreeEvent& event);
@@ -172,7 +172,7 @@ public:
 	void		on_back_to_initial_value();
 	void		on_back_to_sys_value();
 
-	PageShp		add_options_page(wxString title, std::string icon, bool is_extruder_pages = false);
+	PageShp		add_options_page(const wxString& title, const std::string& icon, bool is_extruder_pages = false);
 
 	virtual void	OnActivate(){}
 	virtual void	on_preset_loaded(){}
@@ -181,10 +181,10 @@ public:
 	void			load_initial_data();
 	void			update_dirty();
 	void			update_tab_ui();
-	void			load_config(DynamicPrintConfig config);
+	void			load_config(const DynamicPrintConfig& config);
 	virtual void	reload_config();
-	Field*			get_field(t_config_option_key opt_key, int opt_index = -1) const;
-	bool			set_value(t_config_option_key opt_key, boost::any value);
+	Field*			get_field(const t_config_option_key& opt_key, int opt_index = -1) const;
+	bool			set_value(const t_config_option_key& opt_key, const boost::any& value);
 	wxSizer*		description_line_widget(wxWindow* parent, ogStaticText** StaticText);
 	bool			current_preset_is_dirty();
 	DynamicPrintConfig*	get_config() { return m_config; }
@@ -194,7 +194,7 @@ public:
 	}
 	std::vector<std::string>	get_dependent_tabs() { return m_reload_dependent_tabs; }
 
-	void			on_value_change(std::string opt_key, boost::any value);
+	void			on_value_change(const std::string& opt_key, const boost::any& value);
 
 protected:
 	void			on_presets_changed();
@@ -270,7 +270,7 @@ public:
 	std::string		m_chosen_name;
 	wxComboBox*		m_combo;
 
-	void			build(wxString title, std::string default_name, std::vector<std::string> &values);
+	void			build(const wxString& title, const std::string& default_name, std::vector<std::string> &values);
 	void			accept();
 	std::string		get_name() { return m_chosen_name; }
 };