Fix bag bar drag/drop with container bags

Allow equipped bags to be moved through the shared inventory pickup/drop flow, including dragging from bag contents to bag bar and back from bag bar into bag/backpack slots.

Changes:

- Add InventoryScreen APIs to begin pickup from an equipment slot and drop held item into a target equipment slot.

- Treat inventory type 18 (bags) as valid drops on BAG1-BAG4 during slot validation.

- Route equipment placement in online mode through swapContainerItems with explicit src/dst addressing for deterministic bag slot moves.

- Update bag bar hover-drop path to use InventoryScreen drop API instead of direct local slot mutation.

- On bag bar drag start, hand off to inventory held-item drag when inventory/character UI is open so drops into bag/backpack slots work.

include/ui/inventory_screen.hpp

@@ -166,8 +166,13 @@ public:
     bool isHoldingItem() const { return holdingItem; }
     /// Returns the item being held (only valid when isHoldingItem() is true).
     const game::ItemDef& getHeldItem() const { return heldItem; }
+    /// Begin pickup from an equipment slot (e.g., bag bar slot) into held cursor.
+    bool beginPickupFromEquipSlot(game::Inventory& inv, game::EquipSlot slot);
     /// Cancel the pickup, returning the item to its original slot.
     void returnHeldItem(game::Inventory& inv) { cancelPickup(inv); }
+    /// Drop the currently held item into a specific equipment slot.
+    /// Returns true if the drop was accepted and consumed.
+    bool dropHeldItemToEquipSlot(game::Inventory& inv, game::EquipSlot slot);
 };
 
 } // namespace ui

src/ui/game_screen.cpp

@@ -3670,10 +3670,10 @@ void GameScreen::renderBagBar(game::GameHandler& gameHandler) {
             // Accept dragged item from inventory
             if (hovered && inventoryScreen.isHoldingItem()) {
                 const auto& heldItem = inventoryScreen.getHeldItem();
-                if (heldItem.bagSlots > 0 && ImGui::IsMouseReleased(ImGuiMouseButton_Left)) {
+                if ((heldItem.inventoryType == 18 || heldItem.bagSlots > 0) &&
+                    ImGui::IsMouseReleased(ImGuiMouseButton_Left)) {
                     auto& inventory = gameHandler.getInventory();
-                    inventory.setEquipSlot(bagSlot, heldItem);
+                    inventoryScreen.dropHeldItemToEquipSlot(inventory, bagSlot);
-                    inventoryScreen.returnHeldItem(inventory);
                 }
             }
 
@@ -3685,9 +3685,21 @@ void GameScreen::renderBagBar(game::GameHandler& gameHandler) {
         // releasing completes swap or click
         if (bagBarDragSource_ >= 0) {
             if (ImGui::IsMouseDragging(ImGuiMouseButton_Left, 3.0f) && bagBarPickedSlot_ < 0) {
+                // If an inventory window is open, hand off drag to inventory held-item
+                // so the bag can be dropped into backpack/bag slots.
+                if (inventoryScreen.isOpen() || inventoryScreen.isCharacterOpen()) {
+                    auto equip = static_cast<game::EquipSlot>(
+                        static_cast<int>(game::EquipSlot::BAG1) + bagBarDragSource_);
+                    if (inventoryScreen.beginPickupFromEquipSlot(inv, equip)) {
+                        bagBarDragSource_ = -1;
+                    } else {
+                        bagBarPickedSlot_ = bagBarDragSource_;
+                    }
+                } else {
                     // Mouse moved enough — start visual drag
                     bagBarPickedSlot_ = bagBarDragSource_;
                 }
+            }
             if (ImGui::IsMouseReleased(ImGuiMouseButton_Left)) {
                 if (bagBarPickedSlot_ >= 0) {
                     // Was dragging — check for drop target

src/ui/inventory_screen.cpp

@@ -395,6 +395,13 @@ game::EquipSlot InventoryScreen::getEquipSlotForType(uint8_t inventoryType, game
         case 26: // Ranged
             return game::EquipSlot::RANGED;
         case 16: return game::EquipSlot::BACK;
+        case 18: {
+            for (int i = 0; i < game::Inventory::NUM_BAG_SLOTS; ++i) {
+                auto slot = static_cast<game::EquipSlot>(static_cast<int>(game::EquipSlot::BAG1) + i);
+                if (inv.getEquipSlot(slot).empty()) return slot;
+            }
+            return game::EquipSlot::BAG1;
+        }
         case 19: return game::EquipSlot::TABARD;
         case 20: return game::EquipSlot::CHEST; // Robe
         default: return game::EquipSlot::NUM_SLOTS;
@@ -518,40 +525,56 @@ void InventoryScreen::placeInBag(game::Inventory& inv, int bagIndex, int slotInd
 
 void InventoryScreen::placeInEquipment(game::Inventory& inv, game::EquipSlot slot) {
     if (!holdingItem) return;
-    if (gameHandler_) {
-        if (heldSource == HeldSource::BACKPACK && heldBackpackIndex >= 0) {
-            gameHandler_->autoEquipItemBySlot(heldBackpackIndex);
-            cancelPickup(inv);
-            return;
-        }
-        if (heldSource == HeldSource::BAG) {
-            gameHandler_->autoEquipItemInBag(heldBagIndex, heldBagSlotIndex);
-            cancelPickup(inv);
-            return;
-        }
-        if (heldSource == HeldSource::EQUIPMENT) {
-            cancelPickup(inv);
-            return;
-        }
-    }
 
     // Validate: check if the held item can go in this slot
     if (heldItem.inventoryType > 0) {
+        bool valid = false;
+        if (heldItem.inventoryType == 18) {
+            valid = (slot >= game::EquipSlot::BAG1 && slot <= game::EquipSlot::BAG4);
+        } else {
             game::EquipSlot validSlot = getEquipSlotForType(heldItem.inventoryType, inv);
             if (validSlot == game::EquipSlot::NUM_SLOTS) return;
 
-        bool valid = (slot == validSlot);
+            valid = (slot == validSlot);
             if (!valid) {
                 if (heldItem.inventoryType == 11)
                     valid = (slot == game::EquipSlot::RING1 || slot == game::EquipSlot::RING2);
                 else if (heldItem.inventoryType == 12)
                     valid = (slot == game::EquipSlot::TRINKET1 || slot == game::EquipSlot::TRINKET2);
             }
+        }
         if (!valid) return;
     } else {
         return;
     }
 
+    if (gameHandler_) {
+        uint8_t dstBag = 0xFF;
+        uint8_t dstSlot = static_cast<uint8_t>(slot);
+        uint8_t srcBag = 0xFF;
+        uint8_t srcSlot = 0;
+        if (heldSource == HeldSource::BACKPACK && heldBackpackIndex >= 0) {
+            srcSlot = static_cast<uint8_t>(23 + heldBackpackIndex);
+        } else if (heldSource == HeldSource::BAG && heldBagIndex >= 0 && heldBagSlotIndex >= 0) {
+            srcBag = static_cast<uint8_t>(19 + heldBagIndex);
+            srcSlot = static_cast<uint8_t>(heldBagSlotIndex);
+        } else if (heldSource == HeldSource::EQUIPMENT && heldEquipSlot != game::EquipSlot::NUM_SLOTS) {
+            srcSlot = static_cast<uint8_t>(heldEquipSlot);
+        } else {
+            cancelPickup(inv);
+            return;
+        }
+
+        if (srcBag == dstBag && srcSlot == dstSlot) {
+            cancelPickup(inv);
+            return;
+        }
+
+        gameHandler_->swapContainerItems(srcBag, srcSlot, dstBag, dstSlot);
+        cancelPickup(inv);
+        return;
+    }
+
     const auto& target = inv.getEquipSlot(slot);
     if (target.empty()) {
         inv.setEquipSlot(slot, heldItem);
@@ -657,6 +680,20 @@ void InventoryScreen::renderHeldItem() {
     }
 }
 
+bool InventoryScreen::dropHeldItemToEquipSlot(game::Inventory& inv, game::EquipSlot slot) {
+    if (!holdingItem) return false;
+    placeInEquipment(inv, slot);
+    return !holdingItem;
+}
+
+bool InventoryScreen::beginPickupFromEquipSlot(game::Inventory& inv, game::EquipSlot slot) {
+    if (holdingItem) return false;
+    const auto& eq = inv.getEquipSlot(slot);
+    if (eq.empty()) return false;
+    pickupFromEquipment(inv, slot);
+    return holdingItem;
+}
+
 // ============================================================
 // Bags window (B key) — bottom of screen, no equipment panel
 // ============================================================
@@ -1392,6 +1429,9 @@ void InventoryScreen::renderItemSlot(game::Inventory& inventory, const game::Ite
         if (kind == SlotKind::BACKPACK && (backpackIndex >= 0 || isBagSlot)) {
             validDrop = true;
         } else if (kind == SlotKind::EQUIPMENT && heldItem.inventoryType > 0) {
+            if (heldItem.inventoryType == 18) {
+                validDrop = (equipSlot >= game::EquipSlot::BAG1 && equipSlot <= game::EquipSlot::BAG4);
+            } else {
                 game::EquipSlot validSlot = getEquipSlotForType(heldItem.inventoryType, inventory);
                 validDrop = (equipSlot == validSlot);
                 if (!validDrop && heldItem.inventoryType == 11)
@@ -1400,6 +1440,7 @@ void InventoryScreen::renderItemSlot(game::Inventory& inventory, const game::Ite
                     validDrop = (equipSlot == game::EquipSlot::TRINKET1 || equipSlot == game::EquipSlot::TRINKET2);
             }
         }
+    }
 
     if (isEmpty) {
         ImU32 bgCol = IM_COL32(30, 30, 30, 200);