Even better API, but still not the best organization. This will let me implement both sides, then I can pull it out and try to generalize it into a few guecs components.

gui/fsm.cpp

@@ -135,12 +135,9 @@ namespace gui {
       case LOOT_SELECT: {
           $grab_source = std::any_cast<DinkyECS::Entity>(data);
 
-          if(auto world_entity = $loot_ui.start_grab(*$grab_source)) {
-            auto& source = $loot_ui.get_grab_source(*$grab_source);
-            source.grab($window);
-            source.move($router.position);
-
-            $status_ui.start_drop(*world_entity);
+          if(auto world_entity = $loot_ui.begin_grab(*$grab_source)) {
+            $window.setMouseCursorVisible(false);
+            $status_ui.begin_drop(*world_entity);
           } else {
             // BUG: need a cancel operation here
             $window.setMouseCursorVisible(true);
@@ -149,11 +146,10 @@ namespace gui {
         } break;
       case INV_SELECT: {
           auto gui_id = std::any_cast<DinkyECS::Entity>(data);
-          if($grab_source) {
-            auto& drop = $status_ui.get_drop_target(gui_id);
 
-            if(drop.commit()) {
-              $loot_ui.commit_drop(*$grab_source);
+          if($grab_source) {
+            if($status_ui.commit_drop(gui_id)) {
+              $loot_ui.commit_grab(*$grab_source);
               $grab_source = std::nullopt;
             }
 

gui/guecstra.cpp

@@ -21,8 +21,7 @@ namespace guecs {
   }
 
 
-  void GrabSource::grab(sf::RenderWindow& window) {
-    window.setMouseCursorVisible(false);
+  void GrabSource::grab() {
     sprite->setOrigin({128, 128});
   }
 

gui/guecstra.hpp

@@ -9,7 +9,7 @@ namespace guecs {
   Clickable make_action(DinkyECS::World& target, Events::GUI event, std::any data);
 
   struct GrabSource : public Sprite {
-    void grab(sf::RenderWindow& window);
+    void grab();
     void move(sf::Vector2i position);
   };
 

gui/loot_ui.cpp

@@ -46,15 +46,17 @@ namespace gui {
     update();
   }
 
-  std::optional<DinkyECS::Entity> LootUI::start_grab(DinkyECS::Entity slot_id) {
+  std::optional<DinkyECS::Entity> LootUI::begin_grab(DinkyECS::Entity slot_id) {
     if(contents.contains(slot_id)) {
+      auto& source = get_grab_source(slot_id);
+      source.grab();
       return contents.at(slot_id);
     } else {
       return std::nullopt;
     }
   }
 
-  void LootUI::commit_drop(DinkyECS::Entity slot_id) {
+  void LootUI::commit_grab(DinkyECS::Entity slot_id) {
     contents.erase(slot_id);
     update();
   }
@@ -103,4 +105,8 @@ namespace gui {
   bool LootUI::mouse(float x, float y, bool hover) {
     return $gui.mouse(x, y, hover);
   }
+
+  guecs::DropTarget& LootUI::get_drop_target(DinkyECS::Entity gui_id) {
+    return $gui.get<guecs::DropTarget>(gui_id);
+  }
 }

gui/loot_ui.hpp

@@ -21,9 +21,16 @@ namespace gui {
       void render(sf::RenderWindow& window);
       void update_level(GameLevel &level);
       bool mouse(float x, float y, bool hover);
-      std::optional<DinkyECS::Entity> start_grab(DinkyECS::Entity slot);
+
       guecs::GrabSource& get_grab_source(DinkyECS::Entity entity);
       bool has_grab_source(DinkyECS::Entity gui_id);
-      void commit_drop(DinkyECS::Entity slot_id);
+
+      std::optional<DinkyECS::Entity> begin_grab(DinkyECS::Entity slot);
+      void commit_grab(DinkyECS::Entity slot_id);
+
+
+      guecs::DropTarget& get_drop_target(DinkyECS::Entity gui_id);
+      void begin_drop(DinkyECS::Entity entity);
+      void commit_drop(DinkyECS::Entity entity);
   };
 }

gui/status_ui.cpp

@@ -83,10 +83,6 @@ namespace gui {
     init();
   }
 
-  void StatusUI::start_drop(DinkyECS::Entity entity) {
-    $selected_entity = entity;
-  }
-
   bool StatusUI::place_slot(DinkyECS::Entity gui_id) {
     if($level.world->has<components::Sprite>($selected_entity)) {
       auto& sprite = $level.world->get<components::Sprite>($selected_entity);
@@ -103,4 +99,33 @@ namespace gui {
   guecs::DropTarget& StatusUI::get_drop_target(DinkyECS::Entity gui_id) {
     return $gui.get<guecs::DropTarget>(gui_id);
   }
+
+  void StatusUI::begin_drop(DinkyECS::Entity entity) {
+    $selected_entity = entity;
+  }
+
+  bool StatusUI::commit_drop(DinkyECS::Entity gui_id) {
+    auto& drop = get_drop_target(gui_id);
+
+    return drop.commit();
+  }
+
+  bool StatusUI::has_grab_source(DinkyECS::Entity gui_id) {
+    return $gui.has<guecs::Sprite>(gui_id);
+  }
+
+  guecs::GrabSource& StatusUI::get_grab_source(DinkyECS::Entity gui_id) {
+    dbc::check(has_grab_source(gui_id), "invalid GrabSource requested, entity isn't in the GUI.");
+
+    return static_cast<guecs::GrabSource&>($gui.get<guecs::Sprite>(gui_id));
+  }
+
+  std::optional<DinkyECS::Entity> StatusUI::begin_grab(DinkyECS::Entity slot_id) {
+    (void)slot_id;
+    return std::nullopt;
+  }
+
+  void StatusUI::commit_grab(DinkyECS::Entity slot_id) {
+    (void)slot_id;
+  }
 }

gui/status_ui.hpp

@@ -23,8 +23,16 @@ namespace gui {
       void init();
       void render(sf::RenderWindow &window);
       void update();
-      void start_drop(DinkyECS::Entity entity);
       bool place_slot(DinkyECS::Entity gui_id);
+
+      guecs::GrabSource& get_grab_source(DinkyECS::Entity entity);
+      bool has_grab_source(DinkyECS::Entity gui_id);
+
+      std::optional<DinkyECS::Entity> begin_grab(DinkyECS::Entity slot);
+      void commit_grab(DinkyECS::Entity slot_id);
+
       guecs::DropTarget& get_drop_target(DinkyECS::Entity gui_id);
+      void begin_drop(DinkyECS::Entity entity);
+      bool commit_drop(DinkyECS::Entity entity);
   };
 }