Move now works better, and the API is a lot cleaner. Now just need to make it not crash.

gui/guecstra.cpp

@@ -21,11 +21,20 @@ namespace guecs {
   }
 
   DinkyECS::Entity GrabSource::grab() {
-    fmt::println("grab! {}", world_entity);
     return world_entity;
   }
 
-  void GrabSource::move(sf::Vector2i position) {
-    fmt::println("move! {} to {},{}", world_entity, position.x, position.y);
+  void GrabSource::setSprite(guecs::UI& gui, DinkyECS::Entity gui_id) {
+    dbc::check(gui.has<guecs::Sprite>(gui_id), "GrabSource given sprite gui_id that doesn't exist");
+
+    auto& sp = gui.get<guecs::Sprite>(gui_id);
+    sprite = sp.sprite;
+  }
+
+  void GrabSource::move(sf::Vector2i pos) {
+    if(sprite) {
+      sprite->setPosition({
+          float(pos.x), float(pos.y)});
+    }
   }
 }