diff --git a/src/GUI/Controller.hpp b/src/GUI/Controller.hpp
new file mode 100644
index 000000000..ef3650886
--- /dev/null
+++ b/src/GUI/Controller.hpp
@@ -0,0 +1,15 @@
+#ifndef CONTROLLER_UI_HPP
+#define CONTROLLER_UI_HPP
+
+namespace Slic3r { namespace GUI {
+
+class Controller : public wxPanel { 
+public:
+    Controller(wxWindow* parent, const wxString& title) : 
+        wxPanel(parent, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxTAB_TRAVERSAL, title)
+    { }
+};
+
+}} // Namespace Slic3r::GUI
+
+#endif // CONTROLLER_UI_HPP
diff --git a/src/GUI/GUI.cpp b/src/GUI/GUI.cpp
index 3c669754f..7c249b3b0 100644
--- a/src/GUI/GUI.cpp
+++ b/src/GUI/GUI.cpp
@@ -5,18 +5,19 @@
 
 #include "MainFrame.hpp"
 #include "GUI.hpp"
-//using namespace Slic3r;
 
+namespace Slic3r { namespace GUI {
 
 enum
 {
     ID_Hello = 1
 };
-bool Slic3rGUI::OnInit()
+bool App::OnInit()
 {
-    MainFrame *frame = new MainFrame( "Slic3r", wxDefaultPosition, wxDefaultSize);
+    MainFrame *frame = new MainFrame( "Slic3r", wxDefaultPosition, wxDefaultSize, this->gui_config);
   
     frame->Show( true );
     return true;
 }
 
+}} // namespace Slic3r::GUI
diff --git a/src/GUI/GUI.hpp b/src/GUI/GUI.hpp
index d287c9a9b..1339d1d34 100644
--- a/src/GUI/GUI.hpp
+++ b/src/GUI/GUI.hpp
@@ -1,10 +1,15 @@
 #ifndef GUI_HPP
 #define GUI_HPP
 #include "MainFrame.hpp"
-class Slic3rGUI: public wxApp
+
+namespace Slic3r { namespace GUI {
+class App: public wxApp
 {
+    std::shared_ptr<Settings> gui_config; // GUI-specific configuration options
 public:
     virtual bool OnInit();
+    App(std::shared_ptr<Settings> config) : wxApp(), gui_config(config) {}
 };
 
+}} // namespace Slic3r::GUI
 #endif // GUI_HPP
diff --git a/src/GUI/MainFrame.cpp b/src/GUI/MainFrame.cpp
index d21d2767e..c3684c27b 100644
--- a/src/GUI/MainFrame.cpp
+++ b/src/GUI/MainFrame.cpp
@@ -1,11 +1,17 @@
 #include "MainFrame.hpp"
+#include "Plater.hpp"
+#include "Controller.hpp"
+
+namespace Slic3r { namespace GUI {
 
 wxBEGIN_EVENT_TABLE(MainFrame, wxFrame)
 wxEND_EVENT_TABLE()
 
 MainFrame::MainFrame(const wxString& title, const wxPoint& pos, const wxSize& size)
+        : MainFrame(title, pos, size, nullptr) {}
+MainFrame::MainFrame(const wxString& title, const wxPoint& pos, const wxSize& size, std::shared_ptr<Settings> config)
         : wxFrame(NULL, wxID_ANY, title, pos, size), loaded(false),
-        tabpanel(NULL)
+        tabpanel(nullptr), controller(nullptr), plater(nullptr), gui_config(config)
 {
     // Set icon to either the .ico if windows or png for everything else.
 
@@ -46,11 +52,19 @@ void MainFrame::init_tabpanel()
     panel->Bind(wxEVT_AUINOTEBOOK_PAGE_CHANGED, ([=](wxAuiNotebookEvent& e) 
     { 
         auto panel = this->tabpanel->GetPage(this->tabpanel->GetSelection());
-        if panel->can('OnActivate') panel->OnActivate();
+        auto tabpanel = this->tabpanel;
+        // todo: trigger processing for activation(?)
+        if (tabpanel->GetSelection() > 1) {
+            tabpanel->SetWindowStyle(tabpanel->GetWindowStyleFlag() | wxAUI_NB_CLOSE_ON_ACTIVE_TAB);
+        } else if (this->gui_config->show_host == false && tabpanel->GetSelection() == 1) {
+            tabpanel->SetWindowStyle(tabpanel->GetWindowStyleFlag() | wxAUI_NB_CLOSE_ON_ACTIVE_TAB);
+        } else {
+            tabpanel->SetWindowStyle(tabpanel->GetWindowStyleFlag() | ~wxAUI_NB_CLOSE_ON_ACTIVE_TAB);
+        }
     }), panel->GetId());
 
-//    this->plater = Slic3r::GUI::Plater(panel, _("Plater"));
-//    this->controller = Slic3r::GUI::Controller(panel, _("Controller"));
+    this->plater = new Slic3r::GUI::Plater(panel, _("Plater"));
+    this->controller = new Slic3r::GUI::Controller(panel, _("Controller"));
     
 /* 
 sub _init_tabpanel {
@@ -88,3 +102,5 @@ sub _init_tabpanel {
 void MainFrame::init_menubar()
 {
 }
+
+}} // Namespace Slic3r::GUI
diff --git a/src/GUI/MainFrame.hpp b/src/GUI/MainFrame.hpp
index a1b32feb8..8631ac78a 100644
--- a/src/GUI/MainFrame.hpp
+++ b/src/GUI/MainFrame.hpp
@@ -8,12 +8,21 @@
 #include <wx/aui/auibook.h>
 #include <wx/tooltip.h>
 
+#include <memory>
+
+#include "Controller.hpp"
+#include "Plater.hpp"
+#include "Settings.hpp"
+
+namespace Slic3r { namespace GUI {
+
 constexpr unsigned int TOOLTIP_TIMER = 32767;
 
 class MainFrame: public wxFrame
 {
 public:
     MainFrame(const wxString& title, const wxPoint& pos, const wxSize& size);
+    MainFrame(const wxString& title, const wxPoint& pos, const wxSize& size, std::shared_ptr<Settings> gui_config);
 private:
     wxDECLARE_EVENT_TABLE();
 
@@ -25,7 +34,13 @@ private:
     // STUB: Statusbar reference
 
     wxAuiNotebook* tabpanel;
+    Controller* controller;
+    Plater* plater;
+
+
+    std::shared_ptr<Settings> gui_config;
 
 };
 
+}} // Namespace Slic3r::GUI
 #endif // MAINFRAME_HPP
diff --git a/src/GUI/Plater.hpp b/src/GUI/Plater.hpp
new file mode 100644
index 000000000..bf7aa917a
--- /dev/null
+++ b/src/GUI/Plater.hpp
@@ -0,0 +1,17 @@
+#ifndef PLATER_HPP
+#define PLATER_HPP
+
+namespace Slic3r { namespace GUI {
+
+class Plater : public wxPanel 
+{
+public:
+    Plater(wxWindow* parent, const wxString& title) : 
+        wxPanel(parent, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxTAB_TRAVERSAL, title)
+    { }
+
+};
+
+} } // Namespace Slic3r::GUI
+
+#endif  // PLATER_HPP
diff --git a/src/GUI/Settings.hpp b/src/GUI/Settings.hpp
new file mode 100644
index 000000000..07e219406
--- /dev/null
+++ b/src/GUI/Settings.hpp
@@ -0,0 +1,15 @@
+#ifndef SETTINGS_HPP
+#define SETTINGS_HPP
+namespace Slic3r { namespace GUI {
+
+/// Stub class to hold onto GUI-specific settings options. 
+/// TODO: Incorporate a copy of Slic3r::Config 
+class Settings { 
+    public:
+        bool show_host;
+        Settings(): show_host(false) {} //< Show host/controller tab
+};
+
+}} //namespace Slic3r::GUI
+
+#endif // SETTINGS_HPP
diff --git a/src/slic3r.cpp b/src/slic3r.cpp
index 558d3f810..9dc862400 100644
--- a/src/slic3r.cpp
+++ b/src/slic3r.cpp
@@ -41,9 +41,11 @@ main(int argc, char **argv)
     
     DynamicPrintConfig print_config;
 
-    Slic3rGUI *gui = new Slic3rGUI;
+    std::shared_ptr<GUI::Settings> gui_config = std::make_shared<GUI::Settings>();
 
-    Slic3rGUI::SetInstance(gui);
+    GUI::App *gui = new GUI::App(gui_config);
+
+    GUI::App::SetInstance(gui);
     wxEntry(argc, argv);
     
     // load config files supplied via --load