Mostly refactored out the common things for drag/drop so now just to refine how it's used and bring back moving the sprite around.

gui/fsm.cpp

@@ -145,7 +145,7 @@ namespace gui {
             auto& grab = $loot_ui.get_grab_source(*$grab_source);
 
             if(drop.commit(grab.world_entity)) {
-              $loot_ui.commit_grab(*$grab_source);
+              grab.commit();
               $grab_source = std::nullopt;
             }
 
@@ -193,7 +193,7 @@ namespace gui {
             auto& grab = $status_ui.get_grab_source(*$grab_source);
 
             if(drop.commit(grab.world_entity)) {
-              $status_ui.commit_grab(*$grab_source);
+              grab.commit();
               $grab_source = std::nullopt;
             }
 

gui/guecstra.hpp

@@ -9,7 +9,8 @@ namespace guecs {
   Clickable make_action(DinkyECS::World& target, Events::GUI event, std::any data);
 
   struct GrabSource {
-    DinkyECS::Entity world_entity = 0;
+    DinkyECS::Entity world_entity;
+    std::function<void()> commit;
 
     DinkyECS::Entity grab();
     void move(sf::Vector2i position);

gui/loot_ui.cpp

@@ -46,7 +46,7 @@ namespace gui {
     update();
   }
 
-  void LootUI::commit_grab(DinkyECS::Entity slot_id) {
+  void LootUI::remove_slot(DinkyECS::Entity slot_id) {
     contents.erase(slot_id);
     update();
   }
@@ -67,7 +67,8 @@ namespace gui {
             "item in inventory UI doesn't exist in world. New level?");
         auto& sprite = $level.world->get<components::Sprite>(item);
         $gui.set_init<guecs::Sprite>(id, {sprite.name});
-        $gui.set<guecs::GrabSource>(id, {item});
+        $gui.set<guecs::GrabSource>(id, {
+            item, [&, id]() { return remove_slot(id); }});
       } else {
         $gui.set<guecs::DropTarget>(id, {
            [&, id](DinkyECS::Entity world_entity) -> bool { return place_slot(id, world_entity); }

gui/loot_ui.hpp

@@ -24,7 +24,7 @@ namespace gui {
       guecs::GrabSource& get_grab_source(DinkyECS::Entity entity);
 
       std::optional<DinkyECS::Entity> begin_grab(DinkyECS::Entity slot);
-      void commit_grab(DinkyECS::Entity slot_id);
+      void remove_slot(DinkyECS::Entity slot_id);
 
       guecs::DropTarget& get_drop_target(DinkyECS::Entity gui_id);
       bool place_slot(DinkyECS::Entity gui_id, DinkyECS::Entity world_entity);

gui/status_ui.cpp

@@ -89,7 +89,8 @@ namespace gui {
     if($level.world->has<components::Sprite>(world_entity)) {
       auto& sprite = $level.world->get<components::Sprite>(world_entity);
       $gui.set_init<guecs::Sprite>(gui_id, {sprite.name});
-      $gui.set<guecs::GrabSource>(gui_id, {world_entity});
+      $gui.set<guecs::GrabSource>(gui_id, {world_entity,
+          [&, gui_id]() { return remove_slot(gui_id); }});
       contents.insert_or_assign(gui_id, world_entity);
       return true;
     } else {
@@ -107,9 +108,11 @@ namespace gui {
     return $gui.get<guecs::GrabSource>(gui_id);
   }
 
-  void StatusUI::commit_grab(DinkyECS::Entity slot_id) {
+  void StatusUI::remove_slot(DinkyECS::Entity slot_id) {
+    if(contents.contains(slot_id)) {
       contents.erase(slot_id);
       $gui.remove<guecs::GrabSource>(slot_id);
       $gui.remove<guecs::Sprite>(slot_id);
     }
+  }
 }

gui/status_ui.hpp

@@ -23,9 +23,8 @@ namespace gui {
       void update();
       bool mouse(float x, float y, bool hover);
 
-
       guecs::GrabSource& get_grab_source(DinkyECS::Entity entity);
-      void commit_grab(DinkyECS::Entity slot_id);
+      void remove_slot(DinkyECS::Entity slot_id);
 
       guecs::DropTarget& get_drop_target(DinkyECS::Entity gui_id);
       bool place_slot(DinkyECS::Entity gui_id, DinkyECS::Entity world_entity);