Update barter offer for all items when another item is added (Fixes #1935)

apps/openmw/mwgui/inventorywindow.cpp

@@ -278,14 +278,14 @@ namespace MWGui
         if (item.mType == ItemStack::Type_Barter)
         {
             // this was an item borrowed to us by the merchant
-            MWBase::Environment::get().getWindowManager()->getTradeWindow()->returnItem(mSelectedItem, count);
             mTradeModel->returnItemBorrowedToUs(mSelectedItem, count);
+            MWBase::Environment::get().getWindowManager()->getTradeWindow()->returnItem(mSelectedItem, count);
         }
         else
         {
             // borrow item to the merchant
-            MWBase::Environment::get().getWindowManager()->getTradeWindow()->borrowItem(mSelectedItem, count);
             mTradeModel->borrowItemFromUs(mSelectedItem, count);
+            MWBase::Environment::get().getWindowManager()->getTradeWindow()->borrowItem(mSelectedItem, count);
         }
 
         mItemView->update();

apps/openmw/mwgui/tradewindow.cpp

@@ -480,24 +480,38 @@ namespace MWGui
         mMerchantGold->setCaptionWithReplacing("#{sSellerGold} " + boost::lexical_cast<std::string>(getMerchantGold()));
     }
 
-    void TradeWindow::sellToNpc(const MWWorld::Ptr& item, int count, bool boughtItem)
+    void TradeWindow::updateOffer()
     {
-        int diff = MWBase::Environment::get().getMechanicsManager()->getBarterOffer(mPtr, getEffectiveValue(item, count), boughtItem);
+        TradeItemModel* playerTradeModel = MWBase::Environment::get().getWindowManager()->getInventoryWindow()->getTradeModel();
 
-        mCurrentBalance += diff;
-        mCurrentMerchantOffer += diff;
+        int merchantOffer = 0;
+
+        std::vector<ItemStack> playerBorrowed = playerTradeModel->getItemsBorrowedToUs();
+        for (std::vector<ItemStack>::const_iterator it = playerBorrowed.begin(); it != playerBorrowed.end(); ++it)
+        {
+            merchantOffer -= MWBase::Environment::get().getMechanicsManager()->getBarterOffer(mPtr, getEffectiveValue(it->mBase, it->mCount), true);
+        }
+
+        std::vector<ItemStack> merchantBorrowed = mTradeModel->getItemsBorrowedToUs();
+        for (std::vector<ItemStack>::const_iterator it = merchantBorrowed.begin(); it != merchantBorrowed.end(); ++it)
+        {
+            merchantOffer += MWBase::Environment::get().getMechanicsManager()->getBarterOffer(mPtr, getEffectiveValue(it->mBase, it->mCount), false);
+        }
 
+        int diff = merchantOffer - mCurrentMerchantOffer;
+        mCurrentMerchantOffer = merchantOffer;
+        mCurrentBalance += diff;
         updateLabels();
     }
 
-    void TradeWindow::buyFromNpc(const MWWorld::Ptr& item, int count, bool soldItem)
+    void TradeWindow::sellToNpc(const MWWorld::Ptr& item, int count, bool boughtItem)
     {
-        int diff = MWBase::Environment::get().getMechanicsManager()->getBarterOffer(mPtr, getEffectiveValue(item, count), !soldItem);
-
-        mCurrentBalance -= diff;
-        mCurrentMerchantOffer -= diff;
+        updateOffer();
+    }
 
-        updateLabels();
+    void TradeWindow::buyFromNpc(const MWWorld::Ptr& item, int count, bool soldItem)
+    {
+        updateOffer();
     }
 
     void TradeWindow::onReferenceUnavailable()

apps/openmw/mwgui/tradewindow.hpp

@@ -72,6 +72,8 @@ namespace MWGui
             void sellToNpc(const MWWorld::Ptr& item, int count, bool boughtItem); ///< only used for adjusting the gold balance
             void buyFromNpc(const MWWorld::Ptr& item, int count, bool soldItem); ///< only used for adjusting the gold balance
 
+            void updateOffer();
+
             void onItemSelected (int index);
             void sellItem (MyGUI::Widget* sender, int count);