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

src/gui/overlay_ui.cpp

@@ -0,0 +1,63 @@
+#include "gui/overlay_ui.hpp"
+#include "gui/guecstra.hpp"
+#include "constants.hpp"
+#include "events.hpp"
+#include <optional>
+#include "game/level.hpp"
+
+namespace gui {
+  using namespace guecs;
+
+  OverlayUI::OverlayUI() {
+    $gui.position(RAY_VIEW_X, RAY_VIEW_Y, RAY_VIEW_WIDTH, RAY_VIEW_HEIGHT);
+    $gui.layout(
+        "[*%(100,300)left|=top|>(170,170)top_right]"
+        "[_|=middle|=middle_right]"
+        "[_|=bottom|=bottom_right]"
+        );
+    $gui.init();
+  }
+
+  inline void make_clickable_area(guecs::UI &gui, const std::string &name) {
+    auto area = gui.entity(name);
+
+    gui.set<Clickable>(area, {
+      [&](auto) {
+        auto world = GameDB::current_world();
+        world->send<game::Event>(game::Event::AIM_CLICK, area, {});
+      }
+    });
+  }
+
+  void OverlayUI::init() {
+    // gui.init is in the constructor
+    make_clickable_area($gui, "top");
+    make_clickable_area($gui, "middle");
+    make_clickable_area($gui, "bottom");
+  }
+
+  void OverlayUI::render(sf::RenderWindow& window) {
+    $gui.render(window);
+    // $gui.debug_layout(window);
+  }
+
+  void OverlayUI::show_sprite(string region, string sprite_name) {
+    $gui.show_sprite(region, sprite_name);
+  }
+
+  void OverlayUI::close_sprite(string region) {
+    $gui.close<Sprite>(region);
+  }
+
+  void OverlayUI::show_text(string region, wstring content) {
+    $gui.show_text(region, content);
+  }
+
+  void OverlayUI::close_text(string region) {
+    $gui.close<Text>(region);
+  }
+
+  void OverlayUI::update_level() {
+    init();
+  }
+}