I think the actual map drawing is more of a view thing than in the system, so I've moved it to the MapViewUI out of system.

gui.cpp

@@ -84,10 +84,48 @@ MapViewUI::MapViewUI(DinkyECS::World& world, LightRender& lights, Map& game_map)
   $world(world), $lights(lights), $game_map(game_map)
 {}
 
+void MapViewUI::draw_map() {
+  const auto& debug = $world.get_the<Debug>();
+  const auto& player = $world.get_the<Player>();
+  const auto& player_position = $world.get<Position>(player.entity);
+  Point start = $game_map.center_camera(player_position.location, width, height);
+  auto &tiles = $game_map.tiles();
+  auto &paths = $game_map.paths();
+  auto &lighting = $lights.lighting();
+
+  // WARN: this is exploiting that -1 in size_t becomes largest
+  size_t end_x = std::min(size_t(width), $game_map.width() - start.x);
+  size_t end_y = std::min(size_t(height), $game_map.height() - start.y);
+
+  for(size_t y = 0; y < end_y; ++y) {
+    for(size_t x = 0; x < end_x; ++x) {
+      const TileCell& tile = tiles.at(start.x+x, start.y+y);
+      // light value is an integer that's a percent
+      float light_value = debug.LIGHT ? 80 * PERCENT : lighting[start.y+y][start.x+x] * PERCENT;
+      int dnum = debug.PATHS ? paths[start.y+y][start.x+x] : WALL_PATH_LIMIT;
+
+      if(debug.PATHS && dnum != WALL_PATH_LIMIT) {
+        string num = dnum > 15 ? "*" : format("{:x}", dnum);
+
+        $canvas.DrawText(x * 2, y * 4, num, [dnum, tile, light_value](auto &pixel) {
+           pixel.foreground_color = Color::HSV(dnum * 20, 150, 200);
+           pixel.background_color = Color::HSV(30, 20, tile.bg_v * 50 * PERCENT);
+        });
+      } else {
+        $canvas.DrawText(x * 2, y * 4, tile.display, [tile, light_value](auto &pixel) {
+          pixel.foreground_color = Color::HSV(tile.fg_h, tile.fg_s, tile.fg_v * light_value);
+          pixel.background_color = Color::HSV(tile.bg_h, tile.bg_s, tile.bg_v * light_value);
+        });
+      }
+    }
+  }
+
+  System::draw_entities($world, $game_map, lighting, $canvas, start, width, height);
+}
 
 void MapViewUI::create_render() {
   set_renderer(Renderer([&] {
-    System::draw_map($world, $game_map, $lights.lighting(), $canvas, width, height);
+    draw_map();
     return canvas($canvas);
   }));
 }