From d18e8bef2c627f5e5817580da6b4d271b946c6ed Mon Sep 17 00:00:00 2001
From: eidheim <eidheim@gmail.com>
Date: Wed, 1 Jun 2016 14:04:35 +0200
Subject: [PATCH] Added split window, fixes #235

---
 src/directories.cc |   6 +-
 src/files.h        |   5 +-
 src/juci.cc        |  17 +--
 src/juci.h         |   2 +-
 src/menu.cc        |   7 +
 src/notebook.cc    | 345 +++++++++++++++++++++++++++++++++------------
 src/notebook.h     |  43 ++++--
 src/project.cc     |  56 ++++----
 src/project.h      |   2 +-
 src/terminal.cc    |   3 +-
 src/window.cc      | 307 ++++++++++++++++++----------------------
 src/window.h       |   2 -
 12 files changed, 470 insertions(+), 325 deletions(-)

diff --git a/src/directories.cc b/src/directories.cc
index c4eb949..f3e08fa 100644
--- a/src/directories.cc
+++ b/src/directories.cc
@@ -85,7 +85,7 @@ bool Directories::TreeStore::drag_data_received_vfunc(const TreeModel::Path &pat
       return false;
     }
     
-    for(int c=0;c<Notebook::get().size();c++) {
+    for(size_t c=0;c<Notebook::get().size();c++) {
       auto view=Notebook::get().get_view(c);
       if(is_directory) {
         if(filesystem::file_in_path(view->file_path, source_path)) {
@@ -320,7 +320,7 @@ Directories::Directories() : Gtk::TreeView(), stop_update_thread(false) {
       update();
       select(target_path);
       
-      for(int c=0;c<Notebook::get().size();c++) {
+      for(size_t c=0;c<Notebook::get().size();c++) {
         auto view=Notebook::get().get_view(c);
         if(is_directory) {
           if(filesystem::file_in_path(view->file_path, *source_path)) {
@@ -379,7 +379,7 @@ Directories::Directories() : Gtk::TreeView(), stop_update_thread(false) {
       else {
         update();
         
-        for(int c=0;c<Notebook::get().size();c++) {
+        for(size_t c=0;c<Notebook::get().size();c++) {
           auto view=Notebook::get().get_view(c);
           
           if(is_directory) {
diff --git a/src/files.h b/src/files.h
index 028e2e5..5546294 100644
--- a/src/files.h
+++ b/src/files.h
@@ -2,7 +2,7 @@
 #define JUCI_FILES_H_
 #include <string>
 
-#define JUCI_VERSION "1.1.3-4"
+#define JUCI_VERSION "1.1.3-5"
 
 const std::string default_config_file = R"RAW({
     "version": ")RAW"+std::string(JUCI_VERSION)+R"RAW(",
@@ -132,7 +132,8 @@ R"RAW(
         "previous_tab": "<primary><alt>Left",)RAW"
 #endif
 R"RAW(
-        "close_tab": "<primary>w"
+        "close_tab": "<primary>w",
+        "window_toggle_split": ""
     },
     "project": {
         "default_build_path_comment": "Use <project_directory_name> to insert the project top level directory name",
diff --git a/src/juci.cc b/src/juci.cc
index 2b04470..4deab78 100644
--- a/src/juci.cc
+++ b/src/juci.cc
@@ -19,7 +19,7 @@ int Application::on_command_line(const Glib::RefPtr<Gio::ApplicationCommandLine>
       if(boost::filesystem::exists(p)) {
         p=boost::filesystem::canonical(p);
         if(boost::filesystem::is_regular_file(p))
-          files.emplace_back(p);
+          files.emplace_back(p, 0);
         else if(boost::filesystem::is_directory(p))
           directories.emplace_back(p);
       }
@@ -29,7 +29,7 @@ int Application::on_command_line(const Glib::RefPtr<Gio::ApplicationCommandLine>
         auto new_p=boost::filesystem::canonical(parent_p, ec);
         if(!ec && boost::filesystem::is_directory(new_p)) {
           new_p/=p.filename();
-          files.emplace_back(new_p);
+          files.emplace_back(new_p, 0);
         }
         else
           errors.emplace_back("Error: folder path "+parent_p.string()+" does not exist.\n");
@@ -53,10 +53,11 @@ void Application::on_activate() {
       auto folder=pt.get<std::string>("folder");
       if(!folder.empty() && boost::filesystem::exists(folder) && boost::filesystem::is_directory(folder))
         directories.emplace_back(folder);
-      for(auto &v: pt.get_child("files")) {
-        std::string file=v.second.data();
+      for(auto &pt_file: pt.get_child("files")) {
+        auto notebook=pt_file.second.get<size_t>("notebook", -1);
+        auto file=pt_file.second.get<std::string>("file", "");
         if(!file.empty() && boost::filesystem::exists(file) && !boost::filesystem::is_directory(file))
-          files.emplace_back(file);
+          files.emplace_back(file, notebook);
       }
       last_current_file=pt.get<std::string>("current_file");
       if(!boost::filesystem::exists(last_current_file) || boost::filesystem::is_directory(last_current_file))
@@ -74,8 +75,8 @@ void Application::on_activate() {
     else {
       std::string files_in_directory;
       for(auto it=files.begin();it!=files.end();) {
-        if(it->generic_string().substr(0, directory.generic_string().size()+1)==directory.generic_string()+'/') {
-          files_in_directory+=" "+it->string();
+        if(it->first.generic_string().substr(0, directory.generic_string().size()+1)==directory.generic_string()+'/') {
+          files_in_directory+=" "+it->first.string();
           it=files.erase(it);
         }
         else
@@ -90,7 +91,7 @@ void Application::on_activate() {
   }
   
   for(auto &file: files)
-    Notebook::get().open(file);
+    Notebook::get().open(file.first, file.second);
   
   for(auto &error: errors)
     Terminal::get().print(error, true);
diff --git a/src/juci.h b/src/juci.h
index 872b5ad..b56033f 100644
--- a/src/juci.h
+++ b/src/juci.h
@@ -39,7 +39,7 @@ public:
   void on_startup() override;
 private:
   std::vector<boost::filesystem::path> directories;
-  std::vector<boost::filesystem::path> files;
+  std::vector<std::pair<boost::filesystem::path, size_t> > files;
   std::vector<std::string> errors;
 };
 
diff --git a/src/menu.cc b/src/menu.cc
index f0665b9..6bddad0 100644
--- a/src/menu.cc
+++ b/src/menu.cc
@@ -382,6 +382,13 @@ Menu::Menu() {
              +accels["close_tab"]+ //For Ubuntu...
   "        </item>"
   "      </section>"
+  "      <section>"
+  "        <item>"
+  "          <attribute name='label' translatable='yes'>_Toggle _Split</attribute>"
+  "          <attribute name='action'>app.window_toggle_split</attribute>"
+             +accels["window_toggle_split"]+ //For Ubuntu...
+  "        </item>"
+  "      </section>"
   "    </submenu>"
   "  </menu>"
   "</interface>";
diff --git a/src/notebook.cc b/src/notebook.cc
index d2cfe0a..03ce883 100644
--- a/src/notebook.cc
+++ b/src/notebook.cc
@@ -50,50 +50,88 @@ Notebook::TabLabel::TabLabel(const boost::filesystem::path &path, std::function<
   show_all();
 }
 
-Notebook::Notebook() : Gtk::Notebook(), last_index(-1) {
+Notebook::Notebook() : Gtk::HPaned(), notebooks(2) {
   Gsv::init();
   
-  set_scrollable();
-  
-  auto provider = Gtk::CssProvider::create();
-  //GtkNotebook-tab-overlap got removed in gtk 3.20, but margin works in 3.20
+  for(auto &notebook: notebooks) {
+    notebook.set_scrollable();
+    notebook.set_group_name("source_notebooks");
+    notebook.signal_switch_page().connect([this](Gtk::Widget *widget, guint) {
+      //Sometimes focus is lost when tabs are reordered
+      auto hbox=dynamic_cast<Gtk::HBox*>(widget);
+      for(size_t c=0;c<hboxes.size();++c) {
+        if(hboxes[c].get()==hbox) {
+          focus_view(source_views[c]);
+          break;
+        }
+      }
+      last_index=-1;
+      if(on_switch_page)
+        on_switch_page();
+    });
+    notebook.signal_page_removed().connect([this](Gtk::Widget*, guint) {
+      if(on_page_removed)
+        on_page_removed();
+    });
+    notebook.signal_page_added().connect([this](Gtk::Widget* widget, guint) {
+      auto hbox=dynamic_cast<Gtk::HBox*>(widget);
+      for(size_t c=0;c<hboxes.size();++c) {
+        if(hboxes[c].get()==hbox) {
+          focus_view(source_views[c]);
+          break;
+        }
+      }
+    });
+    
+    auto provider = Gtk::CssProvider::create();
+      //GtkNotebook-tab-overlap got removed in gtk 3.20, but margin works in 3.20
 #if GTK_VERSION_GE(3, 20)
-    provider->load_from_data("tab {border-radius: 5px 5px 0 0; padding: 0 4px; margin: 0;}");
+        provider->load_from_data("tab {border-radius: 5px 5px 0 0; padding: 0 4px; margin: 0;}");
 #else
-    provider->load_from_data(".notebook {-GtkNotebook-tab-overlap: 0px;} tab {border-radius: 5px 5px 0 0; padding: 4px 4px;}");
+        provider->load_from_data(".notebook {-GtkNotebook-tab-overlap: 0px;} tab {border-radius: 5px 5px 0 0; padding: 4px 4px;}");
 #endif
-  get_style_context()->add_provider(provider, GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
-  
-  signal_switch_page().connect([this](Gtk::Widget* page, guint page_num) {
-    last_index=-1;
-  });
+      notebook.get_style_context()->add_provider(provider, GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
+  }
+  pack1(notebooks[0], true, true);
 }
 
-int Notebook::size() {
-  return get_n_pages();
+size_t Notebook::size() {
+  return static_cast<int>(source_views.size());
 }
 
-Source::View* Notebook::get_view(int page) {
-  return source_views.at(get_index(page));
+Source::View* Notebook::get_view(size_t index) {
+  if(index>=size())
+    return nullptr;
+  return source_views[index];
 }
 
-size_t Notebook::get_index(int page) {
-  for(size_t c=0;c<hboxes.size();c++) {
-    if(page_num(*hboxes.at(c))==page)
-      return c;
+Source::View* Notebook::get_current_view() {
+  for(auto &view: source_views) {
+    if(view->has_focus())
+      return view;
   }
-  return -1;
+  for(auto &view: source_views) {
+    if(view==last_focused_view)
+      return view;
+  }
+  if(!source_views.empty())
+    return source_views.back();
+  return nullptr;
 }
 
-Source::View* Notebook::get_current_view() {
-  return get_view(get_current_page());
+std::vector<Source::View*> &Notebook::get_views() {
+  return source_views;
 }
 
-void Notebook::open(const boost::filesystem::path &file_path) {
-  for(int c=0;c<size();c++) {
-    if(file_path==get_view(c)->file_path) {
-      set_current_page(c);
-      get_current_view()->grab_focus();
+void Notebook::open(const boost::filesystem::path &file_path, size_t notebook_index) {
+  if(notebook_index==1 && !split)
+    toggle_split();
+  
+  for(size_t c=0;c<size();c++) {
+    if(file_path==source_views[c]->file_path) {
+      auto notebook_page=get_notebook_page(c);
+      notebooks[notebook_page.first].set_current_page(notebook_page.second);
+      focus_view(source_views[c]);
       return;
     }
   }
@@ -107,6 +145,8 @@ void Notebook::open(const boost::filesystem::path &file_path) {
     can_read.close();
   }
   
+  auto last_view=get_current_view();
+  
   auto language=Source::guess_language(file_path);
   if(language && (language->get_id()=="chdr" || language->get_id()=="cpphdr" || language->get_id()=="c" || language->get_id()=="cpp" || language->get_id()=="objc"))
     source_views.emplace_back(new Source::ClangView(file_path, language));
@@ -116,7 +156,7 @@ void Notebook::open(const boost::filesystem::path &file_path) {
   source_views.back()->scroll_to_cursor_delayed=[this](Source::View* view, bool center, bool show_tooltips) {
     while(g_main_context_pending(NULL))
       g_main_context_iteration(NULL, false);
-    if(get_current_page()!=-1 && get_current_view()==view) {
+    if(get_current_view()==view) {
       if(center)
         view->scroll_to(view->get_buffer()->get_insert(), 0.0, 1.0, 0.5);
       else
@@ -126,11 +166,11 @@ void Notebook::open(const boost::filesystem::path &file_path) {
     }
   };
   source_views.back()->on_update_status=[this](Source::View* view, const std::string &status_text) {
-    if(get_current_page()!=-1 && get_current_view()==view)
+    if(get_current_view()==view)
       status.set_text(status_text+" ");
   };
   source_views.back()->on_update_info=[this](Source::View* view, const std::string &info_text) {
-    if(get_current_page()!=-1 && get_current_view()==view)
+    if(get_current_view()==view)
       info.set_text(" "+info_text);
   };
   
@@ -147,100 +187,148 @@ void Notebook::open(const boost::filesystem::path &file_path) {
   
   //Set up tab label
   auto source_view=source_views.back();
-  tab_labels.emplace_back(new TabLabel(file_path, [this, source_view](){
-    for(int c=0;c<size();c++) {
-      if(get_view(c)==source_view) {
-        close(c);
-        break;
-      }
-    }
+  tab_labels.emplace_back(new TabLabel(file_path, [this, source_view]() {
+    auto index=get_index(source_view);
+    if(index!=static_cast<size_t>(-1))
+      close(index);
   }));
-  append_page(*hboxes.back(), *tab_labels.back());
   
-  set_tab_reorderable(*hboxes.back(), true);
-  show_all_children();
-  
-  size_t last_index_tmp=-1;
-  if(get_current_page()!=-1)
-    last_index_tmp=get_index(get_current_page());
-  set_current_page(size()-1);
-  last_index=last_index_tmp;
-  
-  set_focus_child(*source_views.back());
-  get_current_view()->get_buffer()->set_modified(false);
-  get_current_view()->grab_focus();
   //Add star on tab label when the page is not saved:
-  get_current_view()->get_buffer()->signal_modified_changed().connect([this, source_view]() {
+  source_view->get_buffer()->signal_modified_changed().connect([this, source_view]() {
     std::string title=source_view->file_path.filename().string();
     if(source_view->get_buffer()->get_modified())
       title+='*';
     else
       title+=' ';
-    int page=-1;
-    for(int c=0;c<size();c++) {
-      if(get_view(c)==source_view) {
-        page=c;
-        break;
+    
+    for(size_t c=0;c<size();c++) {
+      if(source_views[c]==source_view) {
+        auto &tab_label=tab_labels.at(c);
+        tab_label->label.set_text(title);
+        tab_label->set_tooltip_text(source_view->file_path.string());
+        return;
       }
     }
-    if(page!=-1) {
-      auto &tab_label=tab_labels.at(get_index(page));
-      tab_label->label.set_text(title);
-      tab_label->set_tooltip_text(source_view->file_path.string());
+  });
+  
+  source_view->signal_focus_in_event().connect([this, source_view](GdkEventFocus *) {
+    if(source_view!=last_focused_view) {
+      last_focused_view=source_view;
+      if(on_switch_page)
+        on_switch_page();
     }
+    else
+      last_focused_view=source_view;
+    return false;
   });
+  
+  if(notebook_index==static_cast<size_t>(-1)) {
+    if(!split)
+      notebook_index=0;
+    else if(notebooks[0].get_n_pages()==0)
+      notebook_index=0;
+    else if(notebooks[1].get_n_pages()==0)
+      notebook_index=1;
+    else if(last_view)
+      notebook_index=get_notebook_page(get_index(last_view)).first;
+  }
+  auto &notebook=notebooks[notebook_index];
+  
+  notebook.append_page(*hboxes.back(), *tab_labels.back());
+  
+  notebook.set_tab_reorderable(*hboxes.back(), true);
+  notebook.set_tab_detachable(*hboxes.back(), true);
+  show_all_children();
+  
+  notebook.set_current_page(notebook.get_n_pages()-1);
+  last_index=-1;
+  if(last_view)
+    last_index=get_index(last_view);
+  
+  set_focus_child(*source_views.back());
+  source_view->get_buffer()->set_modified(false);
+  focus_view(source_view);
 }
 
-void Notebook::configure(int view_nr) {
+void Notebook::configure(size_t index) {
 #if GTKSOURCEVIEWMM_MAJOR_VERSION > 2 & GTKSOURCEVIEWMM_MINOR_VERSION > 17
   auto source_font_description=Pango::FontDescription(Config::get().source.font);
   auto source_map_font_desc=Pango::FontDescription(static_cast<std::string>(source_font_description.get_family())+" "+Config::get().source.map_font_size); 
-  source_maps.at(view_nr)->override_font(source_map_font_desc);
+  source_maps.at(index)->override_font(source_map_font_desc);
   if(Config::get().source.show_map) {
-    if(hboxes.at(view_nr)->get_children().size()==1)
-      hboxes.at(view_nr)->pack_end(*source_maps.at(view_nr), Gtk::PACK_SHRINK);
+    if(hboxes.at(index)->get_children().size()==1)
+      hboxes.at(index)->pack_end(*source_maps.at(index), Gtk::PACK_SHRINK);
   }
-  else if(hboxes.at(view_nr)->get_children().size()==2)
-    hboxes.at(view_nr)->remove(*source_maps.at(view_nr));
+  else if(hboxes.at(index)->get_children().size()==2)
+    hboxes.at(index)->remove(*source_maps.at(index));
 #endif
 }
 
-bool Notebook::save(int page) {
-  if(page>=size())
-    return false;
-  auto view=get_view(page);
-  if(!view->save(source_views))
+bool Notebook::save(size_t index) {
+  if(!source_views[index]->save(source_views))
     return false;
-  Project::on_save(page);
+  Project::on_save(index);
   return true;
 }
 
 bool Notebook::save_current() {
-  if(get_current_page()==-1)
-    return false;
-  return save(get_current_page());
+  if(auto view=get_current_view())
+    return save(get_index(view));
+  return false;
 }
 
-bool Notebook::close(int page) {
-  if (page!=-1) {
-    auto view=get_view(page);
+void Notebook::save_session() {
+  try {
+    boost::property_tree::ptree pt_root, pt_files;
+    pt_root.put("folder", Directories::get().path.string());
+    for(size_t notebook_index=0;notebook_index<notebooks.size();++notebook_index) {
+      for(int page=0;page<notebooks[notebook_index].get_n_pages();++page) {
+        auto view=get_view(notebook_index, page);
+        boost::property_tree::ptree pt_child;
+        pt_child.put("notebook", notebook_index);
+        pt_child.put("file", view->file_path.string());
+        pt_files.push_back(std::make_pair("", pt_child));
+      }
+    }
+    pt_root.add_child("files", pt_files);
+    if(auto view=Notebook::get().get_current_view())
+      pt_root.put("current_file", view->file_path.string());
+    boost::property_tree::write_json((Config::get().juci_home_path()/"last_session.json").string(), pt_root);
+  }
+  catch(const std::exception &) {}
+}
+
+bool Notebook::close(size_t index) {
+  if(auto view=get_view(index)) {
     if(view->get_buffer()->get_modified()){
-      if(!save_modified_dialog(page))
+      if(!save_modified_dialog(index))
         return false;
     }
-    auto index=get_index(page);
-    if(page==get_current_page()) {
+    if(view==get_current_view()) {
       if(last_index!=static_cast<size_t>(-1)) {
-        set_current_page(page_num(*hboxes.at(last_index)));
+        auto notebook_page=get_notebook_page(last_index);
+        focus_view(source_views[last_index]);
+        notebooks[notebook_page.first].set_current_page(notebook_page.second);
         last_index=-1;
       }
+      else {
+        auto notebook_page=get_notebook_page(get_index(view));
+        if(notebook_page.second>0)
+          focus_view(get_view(notebook_page.first, notebook_page.second-1));
+        else {
+          size_t notebook_index=notebook_page.first==0?1:0;
+          if(notebooks[notebook_index].get_n_pages()>0)
+            focus_view(get_view(notebook_index, notebooks[notebook_index].get_current_page()));
+        }
+      }
     }
     else if(index==last_index)
       last_index=-1;
     else if(index<last_index && last_index!=static_cast<size_t>(-1))
       last_index--;
     
-    remove_page(page);
+    auto notebook_page=get_notebook_page(index);
+    notebooks[notebook_page.first].remove_page(notebook_page.second);
 #if GTKSOURCEVIEWMM_MAJOR_VERSION > 2 & GTKSOURCEVIEWMM_MINOR_VERSION > 17
     source_maps.erase(source_maps.begin()+index);
 #endif
@@ -258,28 +346,99 @@ bool Notebook::close(int page) {
   return true;
 }
 
-bool Notebook::close_current_page() {
-  if(get_current_page()==-1)
-    return false;
-  return close(get_current_page());
+bool Notebook::close_current() {
+  return close(get_index(get_current_view()));
+}
+
+void Notebook::next() {
+  if(auto view=get_current_view()) {
+    auto notebook_page=get_notebook_page(get_index(view));
+    int page=notebook_page.second+1;
+    if(page>=notebooks[notebook_page.first].get_n_pages())
+      notebooks[notebook_page.first].set_current_page(0);
+    else
+      notebooks[notebook_page.first].set_current_page(page);
+  }
+}
+
+void Notebook::previous() {
+  if(auto view=get_current_view()) {
+    auto notebook_page=get_notebook_page(get_index(view));
+    int page=notebook_page.second-1;
+    if(page<0)
+      notebooks[notebook_page.first].set_current_page(notebooks[notebook_page.first].get_n_pages()-1);
+    else
+      notebooks[notebook_page.first].set_current_page(page);
+  }
+}
+
+void Notebook::toggle_split() {
+  if(!split) {
+    pack2(notebooks[1], true, true);
+    set_position(get_width()/2);
+    show_all();
+  }
+  else {
+    for(size_t c=size();c!=static_cast<size_t>(-1);--c) {
+      auto notebook_index=get_notebook_page(c).first;
+      if(notebook_index==1 && !close(c))
+        return;
+    }
+    remove(notebooks[1]);
+  }
+  split=!split;
 }
 
 boost::filesystem::path Notebook::get_current_folder() {
   if(!Directories::get().path.empty())
     return Directories::get().path;
-  else if(get_current_page()!=-1)
-    return get_current_view()->file_path.parent_path();
+  else if(auto view=get_current_view())
+    return view->file_path.parent_path();
   else
     return boost::filesystem::path();
 }
 
-bool Notebook::save_modified_dialog(int page) {
+size_t Notebook::get_index(Source::View *view) {
+  for(size_t c=0;c<size();++c) {
+    if(source_views[c]==view)
+      return c;
+  }
+  return -1;
+}
+
+Source::View *Notebook::get_view(size_t notebook_index, int page) {
+  if(notebook_index==static_cast<size_t>(-1) || notebook_index>=notebooks.size() ||
+     page<0 || page>=notebooks[notebook_index].get_n_pages())
+    return nullptr;
+  auto hbox=dynamic_cast<Gtk::HBox*>(notebooks[notebook_index].get_nth_page(page));
+  auto scrolled_window=dynamic_cast<Gtk::ScrolledWindow*>(hbox->get_children()[0]);
+  return dynamic_cast<Source::View*>(scrolled_window->get_children()[0]);
+}
+
+void Notebook::focus_view(Source::View *view) {
+  if(!view)
+    return;
+  view->grab_focus();
+}
+
+std::pair<size_t, int> Notebook::get_notebook_page(size_t index) {
+  if(index>=hboxes.size())
+    return {-1, -1};
+  for(size_t c=0;c<notebooks.size();++c) {
+    auto page_num=notebooks[c].page_num(*hboxes[index]);
+    if(page_num>=0)
+      return {c, page_num};
+  }
+  return {-1, -1};
+}
+
+bool Notebook::save_modified_dialog(size_t index) {
   Gtk::MessageDialog dialog(*static_cast<Gtk::Window*>(get_toplevel()), "Save file!", false, Gtk::MESSAGE_QUESTION, Gtk::BUTTONS_YES_NO);
   dialog.set_default_response(Gtk::RESPONSE_YES);
-  dialog.set_secondary_text("Do you want to save: " + get_view(page)->file_path.string()+" ?");
+  dialog.set_secondary_text("Do you want to save: " + get_view(index)->file_path.string()+" ?");
   int result = dialog.run();
   if(result==Gtk::RESPONSE_YES) {
-    save(page);
+    save(index);
     return true;
   }
   else if(result==Gtk::RESPONSE_NO) {
diff --git a/src/notebook.h b/src/notebook.h
index 1fad50d..2cb26b5 100644
--- a/src/notebook.h
+++ b/src/notebook.h
@@ -9,7 +9,7 @@
 #include <map>
 #include <sigc++/sigc++.h>
 
-class Notebook : public Gtk::Notebook {
+class Notebook : public Gtk::HPaned {
   class TabLabel : public Gtk::EventBox {
     Gtk::HBox hbox;
     Gtk::Button button;
@@ -26,29 +26,46 @@ public:
     return singleton;
   }
   
-  Source::View* get_view(int page);
-  size_t get_index(int page);
-  int size();
+  //Source::View* get_view(int page);
+  size_t size();
+  Source::View* get_view(size_t index);
   Source::View* get_current_view();
-  bool close(int page);
-  bool close_current_page();
-  void open(const boost::filesystem::path &file_path);
-  bool save(int page);
+  std::vector<Source::View*> &get_views();
+  
+  void open(const boost::filesystem::path &file_path, size_t notebook_index=-1);
+  void configure(size_t index);
+  bool save(size_t index);
   bool save_current();
-  void configure(int view_nr);
+  void save_session();
+  bool close(size_t index);
+  bool close_current();
+  void next();
+  void previous();
+  void toggle_split();
   boost::filesystem::path get_current_folder();
 
-  std::vector<Source::View*> source_views; //Is NOT freed in destructor, this is intended for quick program exit.
-
   Gtk::Label info;
   Gtk::Label status;
+  
+  std::function<void()> on_switch_page;
+  std::function<void()> on_page_removed;
 private:
-  bool save_modified_dialog(int page);
+  size_t get_index(Source::View *view);
+  Source::View *get_view(size_t notebook_index, int page);
+  void focus_view(Source::View *view);
+  std::pair<size_t, int> get_notebook_page(size_t index);
+  
+  std::vector<Gtk::Notebook> notebooks;
+  std::vector<Source::View*> source_views; //Is NOT freed in destructor, this is intended for quick program exit.
   std::vector<std::unique_ptr<Gtk::Widget> > source_maps;
   std::vector<std::unique_ptr<Gtk::ScrolledWindow> > scrolled_windows;
   std::vector<std::unique_ptr<Gtk::HBox> > hboxes;
   std::vector<std::unique_ptr<TabLabel> > tab_labels;
   
-  size_t last_index;
+  bool split=false;
+  size_t last_index=-1;
+  Source::View* last_focused_view=nullptr;
+  
+  bool save_modified_dialog(size_t index);
 };
 #endif  // JUCI_NOTEBOOK_H_
diff --git a/src/project.cc b/src/project.cc
index 43dc663..ca817ac 100644
--- a/src/project.cc
+++ b/src/project.cc
@@ -25,9 +25,7 @@ Gtk::Label &Project::debug_status_label() {
 }
 
 void Project::save_files(const boost::filesystem::path &path) {
-  if(Notebook::get().get_current_page()==-1)
-    return;
-  for(int c=0;c<Notebook::get().size();c++) {
+  for(size_t c=0;c<Notebook::get().size();c++) {
     auto view=Notebook::get().get_view(c);
     if(view->get_buffer()->get_modified()) {
       if(filesystem::file_in_path(view->file_path, path))
@@ -36,10 +34,10 @@ void Project::save_files(const boost::filesystem::path &path) {
   }
 }
 
-void Project::on_save(int page) {
-  if(page>=Notebook::get().size())
+void Project::on_save(size_t index) {
+  auto view=Notebook::get().get_view(index);
+  if(!view)
     return;
-  auto view=Notebook::get().get_view(page);
   if(view->language && view->language->get_id()=="cmake") {
     boost::filesystem::path cmake_path;
     if(view->file_path.filename()=="CMakeLists.txt")
@@ -54,7 +52,7 @@ void Project::on_save(int page) {
         if(boost::filesystem::exists(build->get_debug_path()))
           build->update_debug(true);
         
-        for(int c=0;c<Notebook::get().size();c++) {
+        for(size_t c=0;c<Notebook::get().size();c++) {
           auto source_view=Notebook::get().get_view(c);
           if(auto source_clang_view=dynamic_cast<Source::ClangView*>(source_view)) {
             if(filesystem::file_in_path(source_clang_view->file_path, build->project_path))
@@ -84,7 +82,7 @@ void Project::debug_update_status(const std::string &debug_status) {
 }
 
 void Project::debug_update_stop() {
-  for(int c=0;c<Notebook::get().size();c++) {
+  for(size_t c=0;c<Notebook::get().size();c++) {
     auto view=Notebook::get().get_view(c);
     if(view->file_path==debug_last_stop_file_path) {
       view->get_source_buffer()->remove_source_marks(view->get_buffer()->begin(), view->get_buffer()->end(), "debug_stop");
@@ -92,7 +90,7 @@ void Project::debug_update_stop() {
     }
   }
   //Add debug stop source mark
-  for(int c=0;c<Notebook::get().size();c++) {
+  for(size_t c=0;c<Notebook::get().size();c++) {
     auto view=Notebook::get().get_view(c);
     if(view->file_path==debug_stop.first) {
       if(debug_stop.second.first-1<view->get_buffer()->get_line_count()) {
@@ -102,15 +100,14 @@ void Project::debug_update_stop() {
       break;
     }
   }
-  if(Notebook::get().get_current_page()!=-1)
-    Notebook::get().get_current_view()->get_buffer()->place_cursor(Notebook::get().get_current_view()->get_buffer()->get_insert()->get_iter());
+  if(auto view=Notebook::get().get_current_view())
+    view->get_buffer()->place_cursor(view->get_buffer()->get_insert()->get_iter());
 }
 
 std::unique_ptr<Project::Base> Project::create() {
   std::unique_ptr<Project::Build> build;
   
-  if(Notebook::get().get_current_page()!=-1) {
-    auto view=Notebook::get().get_current_view();
+  if(auto view=Notebook::get().get_current_view()) {
     build=Build::create(view->file_path);
     if(view->language) {
       auto language_id=view->language->get_id();
@@ -167,7 +164,8 @@ std::pair<std::string, std::string> Project::Clang::get_run_arguments() {
     arguments=run_arguments_it->second;
   
   if(arguments.empty()) {
-    auto executable=build->get_executable(Notebook::get().get_current_page()!=-1?Notebook::get().get_current_view()->file_path:"").string();
+    auto view=Notebook::get().get_current_view();
+    auto executable=build->get_executable(view?view->file_path:"").string();
     
     if(executable!="") {
       size_t pos=executable.find(project_path);
@@ -210,7 +208,8 @@ void Project::Clang::compile_and_run() {
     arguments=run_arguments_it->second;
   
   if(arguments.empty()) {
-    arguments=build->get_executable(Notebook::get().get_current_page()!=-1?Notebook::get().get_current_view()->file_path:"").string();
+    auto view=Notebook::get().get_current_view();
+    arguments=build->get_executable(view?view->file_path:"").string();
     if(arguments.empty()) {
       Terminal::get().print("Warning: could not find executable.\n");
       Terminal::get().print("Solution: either use Project Set Run Arguments, or open a source file within a directory where add_executable is set.\n", true);
@@ -250,7 +249,8 @@ std::pair<std::string, std::string> Project::Clang::debug_get_run_arguments() {
     arguments=run_arguments_it->second;
   
   if(arguments.empty()) {
-    auto executable=build->get_executable(Notebook::get().get_current_page()!=-1?Notebook::get().get_current_view()->file_path:"").string();
+    auto view=Notebook::get().get_current_view();
+    auto executable=build->get_executable(view?view->file_path:"").string();
     
     if(executable!="") {
       size_t pos=executable.find(project_path);
@@ -277,7 +277,8 @@ void Project::Clang::debug_start() {
     run_arguments=run_arguments_it->second;
   
   if(run_arguments.empty()) {
-    run_arguments=build->get_executable(Notebook::get().get_current_page()!=-1?Notebook::get().get_current_view()->file_path:"").string();
+    auto view=Notebook::get().get_current_view();
+    run_arguments=build->get_executable(view?view->file_path:"").string();
     if(run_arguments.empty()) {
       Terminal::get().print("Warning: could not find executable.\n");
       Terminal::get().print("Solution: either use Debug Set Run Arguments, or open a source file within a directory where add_executable is set.\n", true);
@@ -290,7 +291,7 @@ void Project::Clang::debug_start() {
   }
   
   auto breakpoints=std::make_shared<std::vector<std::pair<boost::filesystem::path, int> > >();
-  for(int c=0;c<Notebook::get().size();c++) {
+  for(size_t c=0;c<Notebook::get().size();c++) {
     auto view=Notebook::get().get_view(c);
     if(filesystem::file_in_path(view->file_path, project_path)) {
       auto iter=view->get_buffer()->begin();
@@ -361,10 +362,10 @@ void Project::Clang::debug_step_out() {
 }
 
 void Project::Clang::debug_backtrace() {
-  if(debugging && Notebook::get().get_current_page()!=-1) {
+  auto view=Notebook::get().get_current_view();
+  if(view && debugging) {
     auto backtrace=Debug::Clang::get().get_backtrace();
     
-    auto view=Notebook::get().get_current_view();
     auto iter=view->get_iter_for_dialog();
     view->selection_dialog=std::unique_ptr<SelectionDialog>(new SelectionDialog(*view, view->get_buffer()->create_mark(iter), true, true));
     auto rows=std::make_shared<std::unordered_map<std::string, Debug::Clang::Frame> >();
@@ -392,9 +393,7 @@ void Project::Clang::debug_backtrace() {
       auto frame=rows->at(selected);
       if(!frame.file_path.empty()) {
         Notebook::get().open(frame.file_path);
-        if(Notebook::get().get_current_page()!=-1) {
-          auto view=Notebook::get().get_current_view();
-          
+        if(auto view=Notebook::get().get_current_view()) {
           Debug::Clang::get().select_frame(frame.index);
           
           view->place_cursor_at_line_index(frame.line_nr-1, frame.line_index-1);
@@ -407,10 +406,10 @@ void Project::Clang::debug_backtrace() {
 }
 
 void Project::Clang::debug_show_variables() {
-  if(debugging && Notebook::get().get_current_page()!=-1) {
+  auto view=Notebook::get().get_current_view();
+  if(debugging && view) {
     auto variables=Debug::Clang::get().get_variables();
     
-    auto view=Notebook::get().get_current_view();
     auto iter=view->get_iter_for_dialog();
     view->selection_dialog=std::unique_ptr<SelectionDialog>(new SelectionDialog(*view, view->get_buffer()->create_mark(iter), true, true));
     auto rows=std::make_shared<std::unordered_map<std::string, Debug::Clang::Variable> >();
@@ -428,9 +427,7 @@ void Project::Clang::debug_show_variables() {
       auto variable=rows->at(selected);
       if(!variable.file_path.empty()) {
         Notebook::get().open(variable.file_path);
-        if(Notebook::get().get_current_page()!=-1) {
-          auto view=Notebook::get().get_current_view();
-          
+        if(auto view=Notebook::get().get_current_view()) {
           Debug::Clang::get().select_frame(variable.frame_index, variable.thread_index_id);
           
           view->place_cursor_at_line_index(variable.line_nr-1, variable.line_index-1);
@@ -449,8 +446,7 @@ void Project::Clang::debug_show_variables() {
         debug_variable_tooltips.hide();
         return;
       }
-      if(Notebook::get().get_current_page()!=-1) {
-        auto view=Notebook::get().get_current_view();
+      if(auto view=Notebook::get().get_current_view()) {
         debug_variable_tooltips.clear();
         auto create_tooltip_buffer=[this, rows, view, selected]() {
           auto variable=rows->at(selected);
diff --git a/src/project.h b/src/project.h
index f12556d..831eb87 100644
--- a/src/project.h
+++ b/src/project.h
@@ -14,7 +14,7 @@
 namespace Project {
   Gtk::Label &debug_status_label();
   void save_files(const boost::filesystem::path &path);
-  void on_save(int page);
+  void on_save(size_t index);
   
   extern boost::filesystem::path debug_last_stop_file_path;
   extern std::unordered_map<std::string, std::string> run_arguments;
diff --git a/src/terminal.cc b/src/terminal.cc
index 98d9bfa..176b6d3 100644
--- a/src/terminal.cc
+++ b/src/terminal.cc
@@ -365,8 +365,7 @@ bool Terminal::on_button_press_event(GdkEventButton* button_event) {
           path=boost::filesystem::canonical(path_str, ec);
         if(!ec && boost::filesystem::is_regular_file(path)) {
           Notebook::get().open(path);
-          if(Notebook::get().get_current_page()!=-1) {
-            auto view=Notebook::get().get_current_view();
+          if(auto view=Notebook::get().get_current_view()) {
             try {
               int line = std::stoi(sm[3].str())-1;
               int index = std::stoi(sm[4].str())-1;
diff --git a/src/window.cc b/src/window.cc
index a8b67f5..fca4488 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -23,18 +23,19 @@ namespace sigc {
 #endif
 }
 
-Window::Window() : notebook(Notebook::get()) {
+Window::Window() {
   set_title("juCi++");
   set_events(Gdk::POINTER_MOTION_MASK|Gdk::FOCUS_CHANGE_MASK|Gdk::SCROLL_MASK|Gdk::LEAVE_NOTIFY_MASK);
   
   set_menu_actions();
-    
   configure();
+  activate_menu_items(false);
+  
   set_default_size(Config::get().window.default_size.first, Config::get().window.default_size.second);
   
   directories_scrolled_window.add(Directories::get());
   directory_and_notebook_panes.pack1(directories_scrolled_window, Gtk::SHRINK);
-  notebook_vbox.pack_start(notebook);
+  notebook_vbox.pack_start(Notebook::get());
   notebook_vbox.pack_end(EntryBox::get(), Gtk::PACK_SHRINK);
   directory_and_notebook_panes.pack2(notebook_vbox, Gtk::SHRINK);
   directory_and_notebook_panes.set_position(static_cast<int>(0.2*Config::get().window.default_size.first));
@@ -44,7 +45,7 @@ Window::Window() : notebook(Notebook::get()) {
   terminal_scrolled_window.add(Terminal::get());
   terminal_vbox.pack_start(terminal_scrolled_window);
     
-  info_and_status_hbox.pack_start(notebook.info, Gtk::PACK_SHRINK);
+  info_and_status_hbox.pack_start(Notebook::get().info, Gtk::PACK_SHRINK);
   
 #if GTK_VERSION_GE(3, 12)
   info_and_status_hbox.set_center_widget(Project::debug_status_label());
@@ -52,7 +53,7 @@ Window::Window() : notebook(Notebook::get()) {
   Project::debug_status_label().set_halign(Gtk::Align::ALIGN_CENTER);
   info_and_status_hbox.pack_start(Project::debug_status_label());
 #endif
-  info_and_status_hbox.pack_end(notebook.status, Gtk::PACK_SHRINK);
+  info_and_status_hbox.pack_end(Notebook::get().status, Gtk::PACK_SHRINK);
   terminal_vbox.pack_end(info_and_status_hbox, Gtk::PACK_SHRINK);
   vpaned.pack2(terminal_vbox, true, true);
   
@@ -77,7 +78,7 @@ Window::Window() : notebook(Notebook::get()) {
   Info::get().hide();
 
   Directories::get().on_row_activated=[this](const boost::filesystem::path &path) {
-    notebook.open(path);
+    Notebook::get().open(path);
   };
 
   //Scroll to end of terminal whenever info is printed
@@ -98,14 +99,12 @@ Window::Window() : notebook(Notebook::get()) {
     notebook_vbox.unset_focus_chain();
   });
   EntryBox::get().signal_hide().connect([this]() {
-    if(notebook.get_current_page()!=-1) {
-      notebook.get_current_view()->grab_focus();
-    }
+    if(auto view=Notebook::get().get_current_view())
+      view->grab_focus();
   });
 
-  notebook.signal_switch_page().connect([this](Gtk::Widget* page, guint page_num) {
-    if(notebook.get_current_page()!=-1) {
-      auto view=notebook.get_current_view();
+  Notebook::get().on_switch_page=[this] {
+    if(auto view=Notebook::get().get_current_view()) {
       if(search_entry_shown && EntryBox::get().labels.size()>0) {
         view->update_search_occurrences=[this](int number){
           EntryBox::get().labels.begin()->update(0, std::to_string(number));
@@ -127,10 +126,10 @@ Window::Window() : notebook(Notebook::get()) {
       view->set_status(view->status);
       view->set_info(view->info);
     }
-  });
-  notebook.signal_page_removed().connect([this](Gtk::Widget* page, guint page_num) {
+  };
+  Notebook::get().on_page_removed=[] {
     EntryBox::get().hide();
-  });
+  };
   
   about.signal_response().connect([this](int d){
     about.hide();
@@ -175,14 +174,14 @@ void Window::set_menu_actions() {
     about.present();
   });
   menu.add_action("preferences", [this]() {
-    notebook.open(Config::get().juci_home_path()/"config"/"config.json");
+    Notebook::get().open(Config::get().juci_home_path()/"config"/"config.json");
   });
   menu.add_action("quit", [this]() {
     close();
   });
   
   menu.add_action("new_file", [this]() {
-    boost::filesystem::path path = Dialog::new_file(notebook.get_current_folder());
+    boost::filesystem::path path = Dialog::new_file(Notebook::get().get_current_folder());
     if(path!="") {
       if(boost::filesystem::exists(path)) {
         Terminal::get().print("Error: "+path.string()+" already exists.\n", true);
@@ -191,7 +190,7 @@ void Window::set_menu_actions() {
         if(filesystem::write(path)) {
           if(Directories::get().path!="")
             Directories::get().update();
-          notebook.open(path);
+          Notebook::get().open(path);
           Terminal::get().print("New file "+path.string()+" created.\n");
         }
         else
@@ -201,7 +200,7 @@ void Window::set_menu_actions() {
   });
   menu.add_action("new_folder", [this]() {
     auto time_now=std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
-    boost::filesystem::path path = Dialog::new_folder(notebook.get_current_folder());
+    boost::filesystem::path path = Dialog::new_folder(Notebook::get().get_current_folder());
     if(path!="" && boost::filesystem::exists(path)) {
       boost::system::error_code ec;
       auto last_write_time=boost::filesystem::last_write_time(path, ec);
@@ -216,7 +215,7 @@ void Window::set_menu_actions() {
     }
   });
   menu.add_action("new_project_cpp", [this]() {
-    boost::filesystem::path project_path = Dialog::new_folder(notebook.get_current_folder());
+    boost::filesystem::path project_path = Dialog::new_folder(Notebook::get().get_current_folder());
     if(project_path!="") {
       auto project_name=project_path.filename().string();
       for(size_t c=0;c<project_name.size();c++) {
@@ -239,7 +238,7 @@ void Window::set_menu_actions() {
       std::string cpp_main="#include <iostream>\n\nint main() {\n  std::cout << \"Hello World!\\n\";\n}\n";
       if(filesystem::write(cmakelists_path, cmakelists) && filesystem::write(cpp_main_path, cpp_main)) {
         Directories::get().open(project_path);
-        notebook.open(cpp_main_path);
+        Notebook::get().open(cpp_main_path);
         Directories::get().update();
         Terminal::get().print("C++ project "+project_name+" created.\n");
       }
@@ -249,43 +248,41 @@ void Window::set_menu_actions() {
   });
   
   menu.add_action("open_file", [this]() {
-    auto path=Dialog::open_file(notebook.get_current_folder());
+    auto path=Dialog::open_file(Notebook::get().get_current_folder());
     if(path!="")
-      notebook.open(path);
+      Notebook::get().open(path);
   });
   menu.add_action("open_folder", [this]() {
-    auto path = Dialog::open_folder(notebook.get_current_folder());
+    auto path = Dialog::open_folder(Notebook::get().get_current_folder());
     if (path!="" && boost::filesystem::exists(path))
       Directories::get().open(path);
   });
   
   menu.add_action("save", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      if(notebook.save_current()) {
-        if(notebook.get_current_page()!=-1) {
-          if(notebook.get_current_view()->file_path==Config::get().juci_home_path()/"config"/"config.json") {
-            configure();
-            for(int c=0;c<notebook.size();c++) {
-              notebook.get_view(c)->configure();
-              notebook.configure(c);
-            }
+    if(auto view=Notebook::get().get_current_view()) {
+      if(Notebook::get().save_current()) {
+        if(view->file_path==Config::get().juci_home_path()/"config"/"config.json") {
+          configure();
+          for(size_t c=0;c<Notebook::get().size();c++) {
+            Notebook::get().get_view(c)->configure();
+            Notebook::get().configure(c);
           }
         }
       }
     }
   });
   menu.add_action("save_as", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto path = Dialog::save_file_as(notebook.get_current_view()->file_path);
+    if(auto view=Notebook::get().get_current_view()) {
+      auto path = Dialog::save_file_as(view->file_path);
       if(path!="") {
         std::ofstream file(path);
         if(file) {
-          file << notebook.get_current_view()->get_buffer()->get_text();
+          file << view->get_buffer()->get_text();
           file.close();
           if(Directories::get().path!="")
             Directories::get().update();
-          notebook.open(path);
-          Terminal::get().print("File saved to: " + notebook.get_current_view()->file_path.string()+"\n");
+          Notebook::get().open(path);
+          Terminal::get().print("File saved to: " + Notebook::get().get_current_view()->file_path.string()+"\n");
         }
         else
           Terminal::get().print("Error saving file\n");
@@ -294,8 +291,7 @@ void Window::set_menu_actions() {
   });
   
   menu.add_action("print", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto view=notebook.get_current_view();
+    if(auto view=Notebook::get().get_current_view()) {
       auto print_operation=Gtk::PrintOperation::create();
       auto print_compositor=Gsv::PrintCompositor::create(*view);
       
@@ -315,20 +311,20 @@ void Window::set_menu_actions() {
   });
   
   menu.add_action("edit_undo", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto undo_manager = notebook.get_current_view()->get_source_buffer()->get_undo_manager();
+    if(auto view=Notebook::get().get_current_view()) {
+      auto undo_manager = view->get_source_buffer()->get_undo_manager();
       if (undo_manager->can_undo()) {
         undo_manager->undo();
-        notebook.get_current_view()->scroll_to(notebook.get_current_view()->get_buffer()->get_insert());
+        view->scroll_to(view->get_buffer()->get_insert());
       }
     }
   });
   menu.add_action("edit_redo", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto undo_manager = notebook.get_current_view()->get_source_buffer()->get_undo_manager();
+    if(auto view=Notebook::get().get_current_view()) {
+      auto undo_manager = view->get_source_buffer()->get_undo_manager();
       if(undo_manager->can_redo()) {
         undo_manager->redo();
-        notebook.get_current_view()->scroll_to(notebook.get_current_view()->get_buffer()->get_insert());
+        view->scroll_to(view->get_buffer()->get_insert());
       }
     }
   });
@@ -337,8 +333,8 @@ void Window::set_menu_actions() {
     auto widget=get_focus();
     if(auto entry=dynamic_cast<Gtk::Entry*>(widget))
       entry->cut_clipboard();
-    else if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->get_buffer()->cut_clipboard(Gtk::Clipboard::get());
+    else if(auto view=Notebook::get().get_current_view())
+      view->get_buffer()->cut_clipboard(Gtk::Clipboard::get());
   });
   menu.add_action("edit_copy", [this]() {
     auto widget=get_focus();
@@ -351,8 +347,8 @@ void Window::set_menu_actions() {
     auto widget=get_focus();
     if(auto entry=dynamic_cast<Gtk::Entry*>(widget))
       entry->paste_clipboard();
-    else if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->paste();
+    else if(auto view=Notebook::get().get_current_view())
+      view->paste();
   });
   
   menu.add_action("edit_find", [this]() {
@@ -360,41 +356,39 @@ void Window::set_menu_actions() {
   });
   
   menu.add_action("source_spellcheck", [this]() {
-    if(notebook.get_current_page()!=-1)
-        notebook.get_current_view()->spellcheck();
+    if(auto view=Notebook::get().get_current_view())
+      view->spellcheck();
   });
   menu.add_action("source_spellcheck_clear", [this]() {
-    if(notebook.get_current_page()!=-1)
-        notebook.get_current_view()->remove_spellcheck_errors();
+    if(auto view=Notebook::get().get_current_view())
+      view->remove_spellcheck_errors();
   });
   menu.add_action("source_spellcheck_next_error", [this]() {
-    if(notebook.get_current_page()!=-1)
-        notebook.get_current_view()->goto_next_spellcheck_error();
+    if(auto view=Notebook::get().get_current_view())
+      view->goto_next_spellcheck_error();
   });
   
   menu.add_action("source_indentation_set_buffer_tab", [this]() {
     set_tab_entry();
   });
   menu.add_action("source_indentation_auto_indent_buffer", [this]() {
-    if(notebook.get_current_page()!=-1 && notebook.get_current_view()->auto_indent)
-      notebook.get_current_view()->auto_indent();
+    auto view=Notebook::get().get_current_view();
+    if(view && view->auto_indent)
+      view->auto_indent();
   });
   
   menu.add_action("source_goto_line", [this]() {
     goto_line_entry();
   });
   menu.add_action("source_center_cursor", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto view=notebook.get_current_view();
-      
+    if(auto view=Notebook::get().get_current_view())
       view->scroll_to_cursor_delayed(view, true, false);
-    }
   });
   
   menu.add_action("source_find_documentation", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      if(notebook.get_current_view()->get_token_data) {
-        auto data=notebook.get_current_view()->get_token_data();        
+    if(auto view=Notebook::get().get_current_view()) {
+      if(view->get_token_data) {
+        auto data=view->get_token_data();        
         if(data.size()>0) {
           auto documentation_search=Config::get().source.documentation_searches.find(data[0]);
           if(documentation_search!=Config::get().source.documentation_searches.end()) {
@@ -433,17 +427,17 @@ void Window::set_menu_actions() {
   });
   
   menu.add_action("source_goto_declaration", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      if(notebook.get_current_view()->get_declaration_location) {
-        auto location=notebook.get_current_view()->get_declaration_location(notebook.source_views);
+    if(auto view=Notebook::get().get_current_view()) {
+      if(view->get_declaration_location) {
+        auto location=view->get_declaration_location(Notebook::get().get_views());
         if(location) {
           boost::filesystem::path declaration_file;
           boost::system::error_code ec;
           declaration_file=boost::filesystem::canonical(location.file_path, ec);
           if(ec)
             return;
-          notebook.open(declaration_file);
-          auto view=notebook.get_current_view();
+          Notebook::get().open(declaration_file);
+          auto view=Notebook::get().get_current_view();
           auto line=static_cast<int>(location.line)-1;
           auto index=static_cast<int>(location.index)-1;
           view->place_cursor_at_line_index(line, index);
@@ -453,18 +447,17 @@ void Window::set_menu_actions() {
     }
   });
   menu.add_action("source_goto_implementation", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto view=notebook.get_current_view();
+    if(auto view=Notebook::get().get_current_view()) {
       if(view->get_implementation_location) {
-        auto location=view->get_implementation_location(notebook.source_views);
+        auto location=view->get_implementation_location(Notebook::get().get_views());
         if(location) {
           boost::filesystem::path implementation_path;
           boost::system::error_code ec;
           implementation_path=boost::filesystem::canonical(location.file_path, ec);
           if(ec)
             return;
-          notebook.open(implementation_path);
-          auto view=notebook.get_current_view();
+          Notebook::get().open(implementation_path);
+          auto view=Notebook::get().get_current_view();
           auto line=static_cast<int>(location.line)-1;
           auto index=static_cast<int>(location.index)-1;
           view->place_cursor_at_line_index(line, index);
@@ -476,10 +469,9 @@ void Window::set_menu_actions() {
   });
 
   menu.add_action("source_goto_usage", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto view=notebook.get_current_view();
+    if(auto view=Notebook::get().get_current_view()) {
       if(view->get_usages) {
-        auto usages=view->get_usages(notebook.source_views);
+        auto usages=view->get_usages(Notebook::get().get_views());
         if(!usages.empty()) {
           auto iter=view->get_iter_for_dialog();
           view->selection_dialog=std::unique_ptr<SelectionDialog>(new SelectionDialog(*view, view->get_buffer()->create_mark(iter), true, true));
@@ -504,8 +496,8 @@ void Window::set_menu_actions() {
             declaration_file=boost::filesystem::canonical(offset.file_path, ec);
             if(ec)
               return;
-            notebook.open(declaration_file);
-            auto view=notebook.get_current_view();
+            Notebook::get().open(declaration_file);
+            auto view=Notebook::get().get_current_view();
             view->place_cursor_at_line_index(offset.line, offset.index);
             view->scroll_to(view->get_buffer()->get_insert(), 0.0, 1.0, 0.5);
             view->delayed_tooltips_connection.disconnect();
@@ -516,10 +508,9 @@ void Window::set_menu_actions() {
     }
   });
   menu.add_action("source_goto_method", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto view=notebook.get_current_view();
+    if(auto view=Notebook::get().get_current_view()) {
       if(view->get_methods) {
-        auto methods=notebook.get_current_view()->get_methods();
+        auto methods=Notebook::get().get_current_view()->get_methods();
         if(!methods.empty()) {
           auto iter=view->get_iter_for_dialog();
           view->selection_dialog=std::unique_ptr<SelectionDialog>(new SelectionDialog(*view, view->get_buffer()->create_mark(iter), true, true));
@@ -544,15 +535,14 @@ void Window::set_menu_actions() {
   });
   
   menu.add_action("source_goto_next_diagnostic", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      if(notebook.get_current_view()->goto_next_diagnostic) {
-        notebook.get_current_view()->goto_next_diagnostic();
+    if(auto view=Notebook::get().get_current_view()) {
+      if(view->goto_next_diagnostic) {
+        view->goto_next_diagnostic();
       }
     }
   });
   menu.add_action("source_apply_fix_its", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      auto view=notebook.get_current_view();
+    if(auto view=Notebook::get().get_current_view()) {
       if(view->get_fix_its) {
         auto buffer=view->get_buffer();
         auto fix_its=view->get_fix_its();
@@ -648,7 +638,7 @@ void Window::set_menu_actions() {
     EntryBox::get().entries.emplace_back(last_run_command, [this](const std::string& content){
       if(content!="") {
         last_run_command=content;
-        auto run_path=notebook.get_current_folder();
+        auto run_path=Notebook::get().get_current_folder();
         Terminal::get().async_print("Running: "+content+'\n');
   
         Terminal::get().async_process(content, run_path, [this, content](int exit_status){
@@ -760,8 +750,7 @@ void Window::set_menu_actions() {
     EntryBox::get().show();
   });
   menu.add_action("debug_toggle_breakpoint", [this](){
-    if(notebook.get_current_page()!=-1) {
-      auto view=notebook.get_current_view();
+    if(auto view=Notebook::get().get_current_view()) {
       auto line_nr=view->get_buffer()->get_insert()->get_iter().get_line();
       
       if(view->get_source_buffer()->get_source_marks_at_line(line_nr, "debug_breakpoint").size()>0) {
@@ -782,10 +771,8 @@ void Window::set_menu_actions() {
   menu.add_action("debug_goto_stop", [this](){
     if(Project::debugging) {
       if(!Project::debug_stop.first.empty()) {
-        notebook.open(Project::debug_stop.first);
-        if(notebook.get_current_page()!=-1) {
-          auto view=notebook.get_current_view();
-          
+        Notebook::get().open(Project::debug_stop.first);
+        if(auto view=Notebook::get().get_current_view()) {
           int line=Project::debug_stop.second.first-1;
           int index=Project::debug_stop.second.second-1;
           view->place_cursor_at_line_index(line, index);
@@ -800,36 +787,32 @@ void Window::set_menu_actions() {
 #endif
   
   menu.add_action("next_tab", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      notebook.open(notebook.get_view((notebook.get_current_page()+1)%notebook.size())->file_path);
-    }
+    Notebook::get().next();
   });
   menu.add_action("previous_tab", [this]() {
-    if(notebook.get_current_page()!=-1) {
-      int previous_page=notebook.get_current_page()-1;
-      if(previous_page<0)
-        previous_page=notebook.size()-1;
-      notebook.open(notebook.get_view(previous_page)->file_path);
-    }
+    Notebook::get().previous();
   });
   menu.add_action("close_tab", [this]() {
-    notebook.close_current_page();
-    if(notebook.get_current_page()!=-1) {
-      notebook.get_current_view()->set_status(notebook.get_current_view()->status);
-      notebook.get_current_view()->set_info(notebook.get_current_view()->info);
+    Notebook::get().close_current();
+    if(auto view=Notebook::get().get_current_view()) {
+      view->set_status(view->status);
+      view->set_info(view->info);
     }
     else {
-      notebook.status.set_text("");
-      notebook.info.set_text("");
+      Notebook::get().status.set_text("");
+      Notebook::get().info.set_text("");
       
       activate_menu_items(false);
     }
   });
-  activate_menu_items(false);
+  menu.add_action("window_toggle_split", [this] {
+    Notebook::get().toggle_split();
+  });
 }
 
 void Window::activate_menu_items(bool activate) {
   auto &menu = Menu::get();
+  auto &notebook = Notebook::get();
   menu.actions["source_indentation_auto_indent_buffer"]->set_enabled(activate ? static_cast<bool>(notebook.get_current_view()->auto_indent) : false);
   menu.actions["source_find_documentation"]->set_enabled(activate ? static_cast<bool>(notebook.get_current_view()->get_token_data) : false);
   menu.actions["source_goto_declaration"]->set_enabled(activate ? static_cast<bool>(notebook.get_current_view()->get_declaration_location) : false);
@@ -840,8 +823,7 @@ void Window::activate_menu_items(bool activate) {
   menu.actions["source_goto_next_diagnostic"]->set_enabled(activate ? static_cast<bool>(notebook.get_current_view()->goto_next_diagnostic) : false);
   menu.actions["source_apply_fix_its"]->set_enabled(activate ? static_cast<bool>(notebook.get_current_view()->get_fix_its) : false);
 #ifdef JUCI_ENABLE_DEBUG
-  if(notebook.get_current_page()!=-1) {
-    auto view=notebook.get_current_view();
+  if(auto view=notebook.get_current_view()) {
     if(view->language && (view->language->get_id()=="c" || view->language->get_id()=="cpp" || view->language->get_id()=="objc" || view->language->get_id()=="chdr" || view->language->get_id()=="cpphdr"))
       menu.actions["debug_toggle_breakpoint"]->set_enabled(true);
     else
@@ -887,24 +869,11 @@ bool Window::on_key_press_event(GdkEventKey *event) {
 }
 
 bool Window::on_delete_event(GdkEventAny *event) {
-  try {
-    boost::property_tree::ptree pt_root, pt_files;
-    pt_root.put("folder", Directories::get().path.string());
-    for(int c=0;c<notebook.size();c++) {
-      boost::property_tree::ptree pt_child;
-      pt_child.put("", notebook.get_view(c)->file_path.string());
-      pt_files.push_back(std::make_pair("", pt_child));
-    }
-    pt_root.add_child("files", pt_files);
-    if(notebook.get_current_page()!=-1)
-      pt_root.put("current_file", notebook.get_current_view()->file_path.string());
-    boost::property_tree::write_json((Config::get().juci_home_path()/"last_session.json").string(), pt_root);
-  }
-  catch(const std::exception &) {}
+  Notebook::get().save_session();
   
-  auto size=notebook.size();
-  for(int c=0;c<size;c++) {
-    if(!notebook.close_current_page())
+  auto size=Notebook::get().size();
+  for(size_t c=0;c<size;c++) {
+    if(!Notebook::get().close_current())
       return true;
   }
   Terminal::get().kill_async_processes();
@@ -912,6 +881,7 @@ bool Window::on_delete_event(GdkEventAny *event) {
   if(Project::current)
     Project::current->debug_cancel();
 #endif
+
   return false;
 }
 
@@ -934,41 +904,41 @@ void Window::search_and_replace_entry() {
     }
   };
   EntryBox::get().entries.emplace_back(last_search, [this](const std::string& content){
-    if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->search_forward();
+    if(auto view=Notebook::get().get_current_view())
+      view->search_forward();
   });
   auto search_entry_it=EntryBox::get().entries.begin();
   search_entry_it->set_placeholder_text("Find");
-  if(notebook.get_current_page()!=-1) {
-    notebook.get_current_view()->update_search_occurrences=[label_it](int number){
+  if(auto view=Notebook::get().get_current_view()) {
+    view->update_search_occurrences=[label_it](int number){
       label_it->update(0, std::to_string(number));
     };
-    notebook.get_current_view()->search_highlight(search_entry_it->get_text(), case_sensitive_search, regex_search);
+    view->search_highlight(search_entry_it->get_text(), case_sensitive_search, regex_search);
   }
   search_entry_it->signal_key_press_event().connect([this](GdkEventKey* event){
     if(event->keyval==GDK_KEY_Return && (event->state&GDK_SHIFT_MASK)>0) {
-      if(notebook.get_current_page()!=-1)
-        notebook.get_current_view()->search_backward();
+      if(auto view=Notebook::get().get_current_view())
+        view->search_backward();
     }
     return false;
   });
   search_entry_it->signal_changed().connect([this, search_entry_it](){
     last_search=search_entry_it->get_text();
-    if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->search_highlight(search_entry_it->get_text(), case_sensitive_search, regex_search);
+    if(auto view=Notebook::get().get_current_view())
+      view->search_highlight(search_entry_it->get_text(), case_sensitive_search, regex_search);
   });
 
   EntryBox::get().entries.emplace_back(last_replace, [this](const std::string &content){
-    if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->replace_forward(content);
+    if(auto view=Notebook::get().get_current_view())
+      view->replace_forward(content);
   });
   auto replace_entry_it=EntryBox::get().entries.begin();
   replace_entry_it++;
   replace_entry_it->set_placeholder_text("Replace");
   replace_entry_it->signal_key_press_event().connect([this, replace_entry_it](GdkEventKey* event){
     if(event->keyval==GDK_KEY_Return && (event->state&GDK_SHIFT_MASK)>0) {
-      if(notebook.get_current_page()!=-1)
-        notebook.get_current_view()->replace_backward(replace_entry_it->get_text());
+      if(auto view=Notebook::get().get_current_view())
+        view->replace_backward(replace_entry_it->get_text());
     }
     return false;
   });
@@ -977,24 +947,24 @@ void Window::search_and_replace_entry() {
   });
   
   EntryBox::get().buttons.emplace_back("↑", [this](){
-    if(notebook.get_current_page()!=-1)
-        notebook.get_current_view()->search_backward();
+    if(auto view=Notebook::get().get_current_view())
+        view->search_backward();
   });
   EntryBox::get().buttons.back().set_tooltip_text("Find Previous\n\nShortcut: Shift+Enter in the Find entry field");
   EntryBox::get().buttons.emplace_back("⇄", [this, replace_entry_it](){
-    if(notebook.get_current_page()!=-1) {
-      notebook.get_current_view()->replace_forward(replace_entry_it->get_text());
+    if(auto view=Notebook::get().get_current_view()) {
+      view->replace_forward(replace_entry_it->get_text());
     }
   });
   EntryBox::get().buttons.back().set_tooltip_text("Replace Next\n\nShortcut: Enter in the Replace entry field");
   EntryBox::get().buttons.emplace_back("↓", [this](){
-    if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->search_forward();
+    if(auto view=Notebook::get().get_current_view())
+      view->search_forward();
   });
   EntryBox::get().buttons.back().set_tooltip_text("Find Next\n\nShortcut: Enter in the Find entry field");
   EntryBox::get().buttons.emplace_back("Replace All", [this, replace_entry_it](){
-    if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->replace_all(replace_entry_it->get_text());
+    if(auto view=Notebook::get().get_current_view())
+      view->replace_all(replace_entry_it->get_text());
   });
   EntryBox::get().buttons.back().set_tooltip_text("Replace All");
   
@@ -1003,21 +973,21 @@ void Window::search_and_replace_entry() {
   EntryBox::get().toggle_buttons.back().set_active(case_sensitive_search);
   EntryBox::get().toggle_buttons.back().on_activate=[this, search_entry_it](){
     case_sensitive_search=!case_sensitive_search;
-    if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->search_highlight(search_entry_it->get_text(), case_sensitive_search, regex_search);
+    if(auto view=Notebook::get().get_current_view())
+      view->search_highlight(search_entry_it->get_text(), case_sensitive_search, regex_search);
   };
   EntryBox::get().toggle_buttons.emplace_back(".*");
   EntryBox::get().toggle_buttons.back().set_tooltip_text("Use Regex");
   EntryBox::get().toggle_buttons.back().set_active(regex_search);
   EntryBox::get().toggle_buttons.back().on_activate=[this, search_entry_it](){
     regex_search=!regex_search;
-    if(notebook.get_current_page()!=-1)
-      notebook.get_current_view()->search_highlight(search_entry_it->get_text(), case_sensitive_search, regex_search);
+    if(auto view=Notebook::get().get_current_view())
+      view->search_highlight(search_entry_it->get_text(), case_sensitive_search, regex_search);
   };
   EntryBox::get().signal_hide().connect([this]() {
-    for(int c=0;c<notebook.size();c++) {
-      notebook.get_view(c)->update_search_occurrences=nullptr;
-      notebook.get_view(c)->search_highlight("", case_sensitive_search, regex_search);
+    for(size_t c=0;c<Notebook::get().size();c++) {
+      Notebook::get().get_view(c)->update_search_occurrences=nullptr;
+      Notebook::get().get_view(c)->search_highlight("", case_sensitive_search, regex_search);
     }
     search_entry_shown=false;
   });
@@ -1027,8 +997,8 @@ void Window::search_and_replace_entry() {
 
 void Window::set_tab_entry() {
   EntryBox::get().clear();
-  if(notebook.get_current_page()!=-1) {
-    auto tab_char_and_size=notebook.get_current_view()->get_tab_char_and_size();
+  if(auto view=Notebook::get().get_current_view()) {
+    auto tab_char_and_size=view->get_tab_char_and_size();
     
     EntryBox::get().labels.emplace_back();
     auto label_it=EntryBox::get().labels.begin();
@@ -1049,7 +1019,7 @@ void Window::set_tab_entry() {
     entry_tab_char_it->set_placeholder_text("Tab char");
     
     const auto activate_function=[this, entry_tab_char_it, entry_tab_size_it, label_it](const std::string& content){
-      if(notebook.get_current_page()!=-1) {
+      if(auto view=Notebook::get().get_current_view()) {
         char tab_char=0;
         unsigned tab_size=0;
         try {
@@ -1064,7 +1034,7 @@ void Window::set_tab_entry() {
         catch(const std::exception &e) {}
 
         if(tab_char!=0 && tab_size>0) {
-          notebook.get_current_view()->set_tab_char_and_size(tab_char, tab_size);
+          view->set_tab_char_and_size(tab_char, tab_size);
           EntryBox::get().hide();
         }
         else {
@@ -1086,10 +1056,9 @@ void Window::set_tab_entry() {
 
 void Window::goto_line_entry() {
   EntryBox::get().clear();
-  if(notebook.get_current_page()!=-1) {
+  if(Notebook::get().get_current_view()) {
     EntryBox::get().entries.emplace_back("", [this](const std::string& content){
-      if(notebook.get_current_page()!=-1) {
-        auto view=notebook.get_current_view();
+      if(auto view=Notebook::get().get_current_view()) {
         try {
           view->place_cursor_at_line_index(stoi(content)-1, 0);
           view->scroll_to_cursor_delayed(view, true, false);
@@ -1109,8 +1078,7 @@ void Window::goto_line_entry() {
 
 void Window::rename_token_entry() {
   EntryBox::get().clear();
-  if(notebook.get_current_page()!=-1) {
-    auto view=notebook.get_current_view();
+  if(auto view=Notebook::get().get_current_view()) {
     if(view->get_token_spelling && view->rename_similar_tokens) {
       auto spelling=std::make_shared<std::string>(view->get_token_spelling());
       if(!spelling->empty()) {
@@ -1124,9 +1092,8 @@ void Window::rename_token_entry() {
         EntryBox::get().entries.emplace_back(*spelling, [this, view, spelling, iter](const std::string& content){
           //TODO: gtk needs a way to check if iter is valid without dumping g_error message
           //iter->get_buffer() will print such a message, but no segfault will occur
-          if(notebook.get_current_page()!=-1 && notebook.get_current_view()==view &&
-             content!=*spelling && iter->get_buffer() && view->get_buffer()->get_insert()->get_iter()==*iter) {
-            auto renamed_pairs=view->rename_similar_tokens(notebook.source_views, content);
+          if(Notebook::get().get_current_view()==view && content!=*spelling && iter->get_buffer() && view->get_buffer()->get_insert()->get_iter()==*iter) {
+            auto renamed_pairs=view->rename_similar_tokens(Notebook::get().get_views(), content);
             for(auto &renamed: renamed_pairs)
               Terminal::get().print("Replaced "+std::to_string(renamed.second)+" occurrence"+(renamed.second>1?"s":"")+" in file "+renamed.first.string()+"\n");
           }
diff --git a/src/window.h b/src/window.h
index 13fb024..2fb5c21 100644
--- a/src/window.h
+++ b/src/window.h
@@ -6,9 +6,7 @@
 #include <atomic>
 
 class Window : public Gtk::ApplicationWindow {
-private:
   Window();
-  Notebook &notebook; //convenience reference
 public:
   static Window &get() {
     static Window singleton;