Show encumbrance preview when trading (Fixes #1793)

apps/openmw/mwgui/inventorywindow.cpp

@@ -493,6 +493,7 @@ namespace MWGui
 
         float capacity = player.getClass().getCapacity(player);
         float encumbrance = player.getClass().getEncumbrance(player);
+        mTradeModel->adjustEncumbrance(encumbrance);
         mEncumbranceBar->setValue(encumbrance, capacity);
     }
 

apps/openmw/mwgui/tradeitemmodel.cpp

@@ -93,6 +93,21 @@ namespace MWGui
         unborrowImpl(item, count, mBorrowedFromUs);
     }
 
+    void TradeItemModel::adjustEncumbrance(float &encumbrance)
+    {
+        for (std::vector<ItemStack>::iterator it = mBorrowedToUs.begin(); it != mBorrowedToUs.end(); ++it)
+        {
+            MWWorld::Ptr item = it->mBase;
+            encumbrance += item.getClass().getWeight(item) * it->mCount;
+        }
+        for (std::vector<ItemStack>::iterator it = mBorrowedFromUs.begin(); it != mBorrowedFromUs.end(); ++it)
+        {
+            MWWorld::Ptr item = it->mBase;
+            encumbrance -= item.getClass().getWeight(item) * it->mCount;
+        }
+        encumbrance = std::max(0.f, encumbrance);
+    }
+
     void TradeItemModel::abort()
     {
         mBorrowedFromUs.clear();

apps/openmw/mwgui/tradeitemmodel.hpp

@@ -34,6 +34,10 @@ namespace MWGui
         /// Aborts trade
         void abort();
 
+        /// Adjusts the given encumbrance by adding weight for items that have been lent to us,
+        /// and removing weight for items we've lent to someone else.
+        void adjustEncumbrance (float& encumbrance);
+
         std::vector<ItemStack> getItemsBorrowedToUs();
 
     private: