First cut of pulling out the relevant parts of my original game to make a little framework.

src/gui/event_router.hpp

@@ -0,0 +1,49 @@
+#pragma once
+#include "events.hpp"
+#include "events.hpp"
+#include "algos/simplefsm.hpp"
+#include <SFML/Graphics.hpp>
+
+namespace gui {
+  namespace routing {
+    enum class State {
+      START,
+      IDLE,
+      MOUSE_ACTIVE,
+      MOUSE_MOVING,
+      MOUSE_DRAGGING
+    };
+
+    enum class Event {
+      STARTED=0,
+      MOUSE_DOWN=1,
+      MOUSE_UP=2,
+      MOUSE_MOVE=3,
+      KEY_PRESS=4
+    };
+
+    class Router : public DeadSimpleFSM<State, Event> {
+      public:
+        sf::Vector2i position;
+        sf::Keyboard::Scancode scancode;
+        game::Event $next_event = game::Event::TICK;
+        int move_count = 0;
+        bool left_button = true;
+        int $drag_tolerance = 4;
+
+        void event(Event ev);
+
+        void START(Event ev);
+        void IDLE(Event ev);
+        void MOUSE_ACTIVE(Event ev);
+        void MOUSE_MOVING(Event ev);
+        void MOUSE_DRAGGING(Event ev);
+
+        game::Event process_event(std::optional<sf::Event> ev);
+
+        void set_event(game::Event ev) {
+          $next_event = ev;
+        }
+    };
+  }
+}