Refactored the GUECS system to have its own namespace then got Meter to work.

tests/guecs.cpp

@@ -0,0 +1,34 @@
+#include <catch2/catch_test_macros.hpp>
+#include <fmt/core.h>
+#include "constants.hpp"
+#include "guecs.hpp"
+#include "texture.hpp"
+
+using namespace guecs;
+
+TEST_CASE("prototype one gui", "[ecs-gui]") {
+  guecs::UI gui;
+
+  TexturePack textures;
+  textures.load_sprites();
+
+  gui.position(0, 0, 1000, 500);
+  gui.layout("[test1|test2|test3][test4|_|test5]");
+
+  for(auto& [name, cell] : gui.cells()) {
+    auto& world = gui.world();
+    auto button = gui.entity(name);
+    world.set<lel::Cell>(button, cell);
+    world.set<Rectangle>(button, {});
+    world.set<Clickable>(button, {});
+    world.set<Textual>(button, {name});
+  }
+
+  gui.init(textures);
+
+  // at this point it's mostly ready but I'd need to render it to a window real quick
+  sf::RenderWindow window;
+  window.setSize({SCREEN_WIDTH, SCREEN_HEIGHT});
+  gui.render(window);
+  window.display();
+}