Moved the main event loop out of GUI so it's not so tightly coupled to everything else.

escape_turings_tarpit.cpp

@@ -4,11 +4,19 @@
 
 int main(int argc, char *argv[])
 {
-    GUI gui;
-    GameEngine game{100};
+  GUI gui;
+  GameEngine game{100};
+  auto backend = SFMLBackend(game);
+  auto builder = Builder(gui, game);
 
-    auto builder = Builder(gui, game);
-    gui.main_loop(game, builder);
+  backend.startup();
 
-    return 1;
+  while(backend.is_open()) {
+    builder.event(BuildEvent::GO);
+    gui.main_loop(backend);
+  }
+
+  builder.event(BuildEvent::QUIT);
+  backend.shutdown();
+  return 1;
 }

gui.cpp

@@ -31,22 +31,10 @@ void GUI::output(const string msg) {
   _lines.push_back(msg);
 }
 
-int GUI::main_loop(GameEngine &game, Builder &builder) {
-  auto gui = SFMLBackend(game);
-
-  gui.startup();
-
-  while(gui.is_open()) {
-    builder.event(BuildEvent::GO);
-    gui.handle_events();
-    gui.update_entities();
-    gui.update_log(_lines);
-  }
-
-  builder.event(BuildEvent::QUIT);
-
-  gui.shutdown();
-  return EXIT_SUCCESS;
+void GUI::main_loop(SFMLBackend &gui) {
+  gui.handle_events();
+  gui.update_entities();
+  gui.update_log(_lines);
 }
 
 void GUI::build_works() {

gui.hpp

@@ -20,12 +20,12 @@ class GUI {
 
   GUI();
 
-  // FOUND BUG: adding this found that I was accidentally copying the gui, really it shouldn't be copyable
+  // prevent copy
   GUI(GUI &g) = delete;
 
   void output(const string msg);
 
-  int main_loop(GameEngine &game, Builder &builder);
+  void main_loop(SFMLBackend &backend);
 
   void build_works();
   void build_failed(bool play_sound, const string &command);

sfmlbackend.hpp

@@ -47,6 +47,9 @@ class SFMLBackend {
 public:
   SFMLBackend(GameEngine &g);
 
+  // prevent copy
+  SFMLBackend(SFMLBackend &g) = delete;
+
   void startup();
 
   bool is_open();