Add GetNewDestination to CWallet to fetch new destinations

Instead of having the same multiple lines of code everywhere
that new destinations are fetched, introduce GetNewDestination as
a member function of CWallet which does the key fetching, label
setting, script generation, and destination generation.

src/qt/addresstablemodel.cpp

@@ -358,12 +358,15 @@ QString AddressTableModel::addRow(const QString &type, const QString &label, con
                 return QString();
             }
         }
+
+        // Add entry
+        walletModel->wallet().setAddressBook(DecodeDestination(strAddress), strLabel, "send");
     }
     else if(type == Receive)
     {
         // Generate a new address to associate with given label
-        CPubKey newKey;
-        if(!walletModel->wallet().getKeyFromPool(false /* internal */, newKey))
+        CTxDestination dest;
+        if(!walletModel->wallet().getNewDestination(address_type, strLabel, dest))
         {
             WalletModel::UnlockContext ctx(walletModel->requestUnlock());
             if(!ctx.isValid())
@@ -372,23 +375,18 @@ QString AddressTableModel::addRow(const QString &type, const QString &label, con
                 editStatus = WALLET_UNLOCK_FAILURE;
                 return QString();
             }
-            if(!walletModel->wallet().getKeyFromPool(false /* internal */, newKey))
+            if(!walletModel->wallet().getNewDestination(address_type, strLabel, dest))
             {
                 editStatus = KEY_GENERATION_FAILURE;
                 return QString();
             }
         }
-        walletModel->wallet().learnRelatedScripts(newKey, address_type);
-        strAddress = EncodeDestination(GetDestinationForKey(newKey, address_type));
+        strAddress = EncodeDestination(dest);
     }
     else
     {
         return QString();
     }
-
-    // Add entry
-    walletModel->wallet().setAddressBook(DecodeDestination(strAddress), strLabel,
-                           (type == Send ? "send" : "receive"));
     return QString::fromStdString(strAddress);
 }
 

src/qt/paymentserver.cpp

@@ -666,16 +666,14 @@ void PaymentServer::fetchPaymentACK(WalletModel* walletModel, const SendCoinsRec
     payment.add_transactions(transaction.data(), transaction.size());
 
     // Create a new refund address, or re-use:
-    CPubKey newKey;
-    if (walletModel->wallet().getKeyFromPool(false /* internal */, newKey)) {
+    CTxDestination dest;
+    const OutputType change_type = walletModel->wallet().getDefaultChangeType() != OutputType::CHANGE_AUTO ? walletModel->wallet().getDefaultChangeType() : walletModel->wallet().getDefaultAddressType();
+    if (walletModel->wallet().getNewDestination(change_type, "", dest)) {
         // BIP70 requests encode the scriptPubKey directly, so we are not restricted to address
         // types supported by the receiver. As a result, we choose the address format we also
         // use for change. Despite an actual payment and not change, this is a close match:
         // it's the output type we use subject to privacy issues, but not restricted by what
         // other software supports.
-        const OutputType change_type = walletModel->wallet().getDefaultChangeType() != OutputType::CHANGE_AUTO ? walletModel->wallet().getDefaultChangeType() : walletModel->wallet().getDefaultAddressType();
-        walletModel->wallet().learnRelatedScripts(newKey, change_type);
-        CTxDestination dest = GetDestinationForKey(newKey, change_type);
         std::string label = tr("Refund from %1").arg(recipient.authenticatedMerchant).toStdString();
         walletModel->wallet().setAddressBook(dest, label, "refund");