Better meaning API on both sides for the drag-n-drop operations, but I _swear_ there's a way to do this in the GrabSource/DropTarget instead.

gui/status_ui.cpp

@@ -46,7 +46,7 @@ namespace gui {
             guecs::make_action(*$level.world, Events::GUI::INV_SELECT, {button})
           });
           $gui.set<DropTarget>(button, {
-              [&, button]() -> bool { return place_slot(button); }
+              .commit=[&, button]() -> bool { return place_slot(button); }
           });
         }
       }
@@ -83,7 +83,7 @@ namespace gui {
     init();
   }
 
-  void StatusUI::select_slot(DinkyECS::Entity entity) {
+  void StatusUI::start_drop(DinkyECS::Entity entity) {
     $selected_entity = entity;
   }
 
@@ -99,4 +99,8 @@ namespace gui {
       return false;
     }
   }
+
+  guecs::DropTarget& StatusUI::get_drop_target(DinkyECS::Entity gui_id) {
+    return $gui.get<guecs::DropTarget>(gui_id);
+  }
 }