I think I've got my head around what ECS does and am slowly reshaping the engine to use it better.

gui.cpp

@@ -19,38 +19,14 @@
 #include "dbc.hpp"
 #include "gui.hpp"
 #include "rand.hpp"
+#include "components.hpp"
+#include "systems.hpp"
 
 using std::string;
 using namespace fmt;
 using namespace std::chrono_literals;
 using namespace ftxui;
 
-struct Player {
-  DinkyECS::Entity entity;
-};
-
-struct Position {
-  Point location;
-};
-
-struct Motion {
-  int dx;
-  int dy;
-};
-
-struct Combat {
-  int hp;
-  int damage;
-};
-
-struct Treasure {
-  int amount;
-};
-
-struct Tile {
-  std::string chr = "!";
-};
-
 std::array<sf::Color, 10> VALUES{
   sf::Color{1, 4, 2},  // black
   sf::Color{9, 29, 16}, // dark dark
@@ -121,10 +97,7 @@ void GUI::create_renderer() {
       }
     }
 
-    $world.system<Position, Tile>([&](const auto &ent, auto &pos, auto &tile) {
-      $canvas.DrawText(pos.location.x*2, pos.location.y*4, tile.chr);
-    });
-
+    System::draw_entities($world, $canvas);
     return canvas($canvas);
   });
 
@@ -164,42 +137,9 @@ void GUI::handle_events() {
 
       // COMPOSE system? You create a bunch of callbacks and then combine them into
       // a single run over the data?
-
-      // move enemies system
-      $world.system<Position, Motion>([&](const auto &ent, auto &position, auto &motion) {
-        if(ent != player.entity) {
-          Point out = position.location;
-          $game_map.neighbors(out, false);
-          motion = { int(out.x - position.location.x), int(out.y - position.location.y)};
-        }
-      });
-
-      // motion system
-      $world.system<Position, Motion>([&](const auto &ent, auto &position, auto &motion) {
-        Point move_to = {
-          position.location.x + motion.dx,
-          position.location.y + motion.dy
-        };
-        motion = {0,0}; // clear it after getting it
-
-        if($game_map.inmap(move_to.x, move_to.y) && !$game_map.iswall(move_to.x,move_to.y)) {
-          $game_map.clear_target(position.location);
-          position.location = move_to;
-        }
-      });
-
-      // combat system
-      auto combatSystem = [&]() {
-        const auto& player_position = $world.component<Position>(player.entity);
-        $world.system<Position, Combat>([&](const auto &ent, auto &pos, auto &combat) {
-            if(ent != player.entity && pos.location.x == player_position.location.x &&
-                pos.location.y == player_position.location.y) {
-                $burn_baby_burn = true;
-            }
-        });
-      };
-
-      combatSystem();
+      System::enemy_pathing($world, $game_map, player);
+      System::motion($world, $game_map);
+      System::combat($world, player);
     }
   }
 }
@@ -276,16 +216,6 @@ void GUI::render_scene() {
   std::wstring map_screen_utf8 = $converter.from_bytes($map_screenout);
   $map_text.setString(map_screen_utf8);
 
-  if($shake_it) {
-    shake();
-    $shake_it = false;
-  }
-
-  if($burn_baby_burn) {
-    burn();
-    $burn_baby_burn = false;
-  }
-
   draw_screen();
 }