Subtract fee from amount

src/core.h

@@ -174,7 +174,7 @@ class CTxOut
 
     uint256 GetHash() const;
 
-    bool IsDust(CFeeRate minRelayTxFee) const
+    int64_t GetDustThreshold(CFeeRate& minRelayTxFee) const
     {
         // "Dust" is defined in terms of CTransaction::minRelayTxFee,
         // which has units satoshis-per-kilobyte.
@@ -185,7 +185,12 @@ class CTxOut
         // so dust is a txout less than 546 satoshis 
         // with default minRelayTxFee.
         size_t nSize = GetSerializeSize(SER_DISK,0)+148u;
-        return (nValue < 3*minRelayTxFee.GetFee(nSize));
+        return 3*minRelayTxFee.GetFee(nSize);
+    }
+
+    bool IsDust(CFeeRate minRelayTxFee) const
+    {
+        return (nValue < GetDustThreshold(minRelayTxFee));
     }
 
     friend bool operator==(const CTxOut& a, const CTxOut& b)

src/qt/coincontroldialog.cpp

@@ -31,6 +31,7 @@
 using namespace std;
 QList<qint64> CoinControlDialog::payAmounts;
 CCoinControl* CoinControlDialog::coinControl = new CCoinControl();
+bool CoinControlDialog::fSubtractFeeFromAmount = false;
 
 CoinControlDialog::CoinControlDialog(QWidget *parent) :
     QDialog(parent),
@@ -528,6 +529,11 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
         // Voluntary Fee
         nPayFee = payTxFee.GetFee(max((unsigned int)1000, nBytes));
 
+        // in the subtract fee from amount case, we can tell if zero change already and subtract the bytes, so that fee calculation afterwards is accurate
+        if (CoinControlDialog::fSubtractFeeFromAmount)
+            if (nAmount - nPayAmount == 0)
+                nBytes -= 34;
+
         // Min Fee
         if (nPayFee == 0)
         {
@@ -543,20 +549,27 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
 
         if (nPayAmount > 0)
         {
-            nChange = nAmount - nPayFee - nPayAmount;
+            nChange = nAmount - nPayAmount;
+            if (!CoinControlDialog::fSubtractFeeFromAmount)
+                nChange -= nPayFee;
 
             // Never create dust outputs; if we would, just add the dust to the fee.
             if (nChange > 0 && nChange < CENT)
             {
                 CTxOut txout(nChange, (CScript)vector<unsigned char>(24, 0));
                 if (txout.IsDust(::minRelayTxFee))
                 {
-                    nPayFee += nChange;
-                    nChange = 0;
+                    if (CoinControlDialog::fSubtractFeeFromAmount) // dust-change will be raised until no dust
+                        nChange = txout.GetDustThreshold(::minRelayTxFee);
+                    else
+                    {
+                        nPayFee += nChange;
+                        nChange = 0;
+                    }
                 }
             }
 
-            if (nChange == 0)
+            if (nChange == 0 && !CoinControlDialog::fSubtractFeeFromAmount)
                 nBytes -= 34;
         }
 
@@ -599,7 +612,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     {
         l3->setText("~" + l3->text());
         l4->setText("~" + l4->text());
-        if (nChange > 0)
+        if (nChange > 0 && !CoinControlDialog::fSubtractFeeFromAmount)
             l8->setText("~" + l8->text());
     }
 

src/qt/coincontroldialog.h

@@ -37,6 +37,7 @@ class CoinControlDialog : public QDialog
 
     static QList<qint64> payAmounts;
     static CCoinControl *coinControl;
+    static bool fSubtractFeeFromAmount;
 
 private:
     Ui::CoinControlDialog *ui;

src/qt/forms/sendcoinsentry.ui

@@ -139,7 +139,21 @@
      </widget>
     </item>
     <item row="2" column="1">
-     <widget class="BitcoinAmountField" name="payAmount"/>
+     <layout class="QHBoxLayout" name="horizontalLayoutAmount" stretch="0,1">
+      <item>
+       <widget class="BitcoinAmountField" name="payAmount"/>
+      </item>
+      <item>
+       <widget class="QCheckBox" name="checkboxSubtractFeeFromAmount">
+        <property name="toolTip">
+         <string>The fee will be deducted from the amount being sent. The recipient will receive less bitcoins than you enter in the amount field. If multiple recipients are selected, the fee is split equally.</string>
+        </property>
+        <property name="text">
+         <string>S&amp;ubtract fee from amount</string>
+        </property>
+       </widget>
+      </item>
+     </layout>
     </item>
     <item row="3" column="0">
      <widget class="QLabel" name="messageLabel">

src/qt/sendcoinsdialog.cpp

@@ -139,8 +139,6 @@ void SendCoinsDialog::on_sendButton_clicked()
     }
 
     fNewRecipientAllowed = false;
-
-
     WalletModel::UnlockContext ctx(model->requestUnlock());
     if(!ctx.isValid())
     {
@@ -170,7 +168,7 @@ void SendCoinsDialog::on_sendButton_clicked()
 
     // Format confirmation message
     QStringList formatted;
-    foreach(const SendCoinsRecipient &rcp, recipients)
+    foreach(const SendCoinsRecipient &rcp, currentTransaction.getRecipients())
     {
         // generate bold amount string
         QString amount = "<b>" + BitcoinUnits::formatHtmlWithUnit(model->getOptionsModel()->getDisplayUnit(), rcp.amount);
@@ -284,6 +282,7 @@ SendCoinsEntry *SendCoinsDialog::addEntry()
     ui->entries->addWidget(entry);
     connect(entry, SIGNAL(removeEntry(SendCoinsEntry*)), this, SLOT(removeEntry(SendCoinsEntry*)));
     connect(entry, SIGNAL(payAmountChanged()), this, SLOT(coinControlUpdateLabels()));
+    connect(entry, SIGNAL(subtractFeeFromAmountChanged()), this, SLOT(coinControlUpdateLabels()));
 
     updateTabsAndLabels();
 
@@ -585,11 +584,17 @@ void SendCoinsDialog::coinControlUpdateLabels()
 
     // set pay amounts
     CoinControlDialog::payAmounts.clear();
+    CoinControlDialog::fSubtractFeeFromAmount = false;
     for(int i = 0; i < ui->entries->count(); ++i)
     {
         SendCoinsEntry *entry = qobject_cast<SendCoinsEntry*>(ui->entries->itemAt(i)->widget());
         if(entry)
-            CoinControlDialog::payAmounts.append(entry->getValue().amount);
+        {
+            SendCoinsRecipient rcp = entry->getValue();
+            CoinControlDialog::payAmounts.append(rcp.amount);
+            if (rcp.fSubtractFeeFromAmount)
+                CoinControlDialog::fSubtractFeeFromAmount = true;
+        }
     }
 
     if (CoinControlDialog::coinControl->HasSelected())

src/qt/sendcoinsentry.cpp

@@ -37,6 +37,7 @@ SendCoinsEntry::SendCoinsEntry(QWidget *parent) :
 
     // Connect signals
     connect(ui->payAmount, SIGNAL(valueChanged()), this, SIGNAL(payAmountChanged()));
+    connect(ui->checkboxSubtractFeeFromAmount, SIGNAL(toggled(bool)), this, SIGNAL(subtractFeeFromAmountChanged()));
     connect(ui->deleteButton, SIGNAL(clicked()), this, SLOT(deleteClicked()));
     connect(ui->deleteButton_is, SIGNAL(clicked()), this, SLOT(deleteClicked()));
     connect(ui->deleteButton_s, SIGNAL(clicked()), this, SLOT(deleteClicked()));
@@ -87,6 +88,7 @@ void SendCoinsEntry::clear()
     ui->payTo->clear();
     ui->addAsLabel->clear();
     ui->payAmount->clear();
+    ui->checkboxSubtractFeeFromAmount->setCheckState(Qt::Unchecked);
     ui->messageTextLabel->clear();
     ui->messageTextLabel->hide();
     ui->messageLabel->hide();
@@ -158,6 +160,7 @@ SendCoinsRecipient SendCoinsEntry::getValue()
     recipient.label = ui->addAsLabel->text();
     recipient.amount = ui->payAmount->value();
     recipient.message = ui->messageTextLabel->text();
+    recipient.fSubtractFeeFromAmount = (ui->checkboxSubtractFeeFromAmount->checkState() == Qt::Checked);
 
     return recipient;
 }
@@ -167,7 +170,8 @@ QWidget *SendCoinsEntry::setupTabChain(QWidget *prev)
     QWidget::setTabOrder(prev, ui->payTo);
     QWidget::setTabOrder(ui->payTo, ui->addAsLabel);
     QWidget *w = ui->payAmount->setupTabChain(ui->addAsLabel);
-    QWidget::setTabOrder(w, ui->addressBookButton);
+    QWidget::setTabOrder(w, ui->checkboxSubtractFeeFromAmount);
+    QWidget::setTabOrder(ui->checkboxSubtractFeeFromAmount, ui->addressBookButton);
     QWidget::setTabOrder(ui->addressBookButton, ui->pasteButton);
     QWidget::setTabOrder(ui->pasteButton, ui->deleteButton);
     return ui->deleteButton;

src/qt/sendcoinsentry.h

@@ -51,6 +51,7 @@ public slots:
 signals:
     void removeEntry(SendCoinsEntry *entry);
     void payAmountChanged();
+    void subtractFeeFromAmountChanged();
 
 private slots:
     void deleteClicked();

src/qt/walletmodel.cpp

@@ -6,6 +6,7 @@
 
 #include "addresstablemodel.h"
 #include "guiconstants.h"
+#include "guiutil.h"
 #include "recentrequeststablemodel.h"
 #include "transactiontablemodel.h"
 
@@ -194,8 +195,9 @@ bool WalletModel::validateAddress(const QString &address)
 WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransaction &transaction, const CCoinControl *coinControl)
 {
     qint64 total = 0;
+    bool fSubtractFeeFromAmount = false;
     QList<SendCoinsRecipient> recipients = transaction.getRecipients();
-    std::vector<std::pair<CScript, int64_t> > vecSend;
+    std::vector<CRecipient> vecSend;
 
     if(recipients.empty())
     {
@@ -208,6 +210,9 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
     // Pre-check input data for validity
     foreach(const SendCoinsRecipient &rcp, recipients)
     {
+        if (rcp.fSubtractFeeFromAmount)
+            fSubtractFeeFromAmount = true;
+
         if (rcp.paymentRequest.IsInitialized())
         {   // PaymentRequest...
             int64_t subtotal = 0;
@@ -219,7 +224,9 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
                 subtotal += out.amount();
                 const unsigned char* scriptStr = (const unsigned char*)out.script().data();
                 CScript scriptPubKey(scriptStr, scriptStr+out.script().size());
-                vecSend.push_back(std::pair<CScript, int64_t>(scriptPubKey, out.amount()));
+                int64_t nAmount = out.amount();
+                CRecipient recipient = {scriptPubKey, nAmount, rcp.fSubtractFeeFromAmount};
+                vecSend.push_back(recipient);
             }
             if (subtotal <= 0)
             {
@@ -242,7 +249,8 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
 
             CScript scriptPubKey;
             scriptPubKey.SetDestination(CBitcoinAddress(rcp.address.toStdString()).Get());
-            vecSend.push_back(std::pair<CScript, int64_t>(scriptPubKey, rcp.amount));
+            CRecipient recipient = {scriptPubKey, rcp.amount, rcp.fSubtractFeeFromAmount};
+            vecSend.push_back(recipient);
 
             total += rcp.amount;
         }
@@ -264,16 +272,19 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
 
         transaction.newPossibleKeyChange(wallet);
         int64_t nFeeRequired = 0;
+        int nChangePosRet = -1;
         std::string strFailReason;
 
         CWalletTx *newTx = transaction.getTransaction();
         CReserveKey *keyChange = transaction.getPossibleKeyChange();
-        bool fCreated = wallet->CreateTransaction(vecSend, *newTx, *keyChange, nFeeRequired, strFailReason, coinControl);
+        bool fCreated = wallet->CreateTransaction(vecSend, *newTx, *keyChange, nFeeRequired, nChangePosRet, strFailReason, coinControl);
         transaction.setTransactionFee(nFeeRequired);
+        if (fSubtractFeeFromAmount && fCreated)
+            transaction.reassignAmounts(nChangePosRet);
 
         if(!fCreated)
         {
-            if((total + nFeeRequired) > nBalance)
+            if(!fSubtractFeeFromAmount && (total + nFeeRequired) > nBalance)
             {
                 return SendCoinsReturn(AmountWithFeeExceedsBalance);
             }

src/qt/walletmodel.h

@@ -36,9 +36,9 @@ QT_END_NAMESPACE
 class SendCoinsRecipient
 {
 public:
-    explicit SendCoinsRecipient() : amount(0), nVersion(SendCoinsRecipient::CURRENT_VERSION) { }
+    explicit SendCoinsRecipient() : amount(0), fSubtractFeeFromAmount(false), nVersion(SendCoinsRecipient::CURRENT_VERSION) { }
     explicit SendCoinsRecipient(const QString &addr, const QString &label, quint64 amount, const QString &message):
-        address(addr), label(label), amount(amount), message(message), nVersion(SendCoinsRecipient::CURRENT_VERSION) {}
+        address(addr), label(label), amount(amount), message(message), fSubtractFeeFromAmount(false), nVersion(SendCoinsRecipient::CURRENT_VERSION) {}
 
     // If from an insecure payment request, this is used for storing
     // the addresses, e.g. address-A<br />address-B<br />address-C.
@@ -56,6 +56,8 @@ class SendCoinsRecipient
     // Empty if no authentication or invalid signature/cert/etc.
     QString authenticatedMerchant;
 
+    bool fSubtractFeeFromAmount; // memory only
+
     static const int CURRENT_VERSION = 1;
     int nVersion;
 

src/qt/walletmodeltransaction.cpp

@@ -41,6 +41,38 @@ void WalletModelTransaction::setTransactionFee(qint64 newFee)
     fee = newFee;
 }
 
+void WalletModelTransaction::reassignAmounts(int nChangePosRet)
+{
+    int i = 0;
+    for (QList<SendCoinsRecipient>::iterator it = recipients.begin(); it != recipients.end(); ++it)
+    {
+        SendCoinsRecipient& rcp = (*it);
+
+        if (rcp.paymentRequest.IsInitialized())
+        {
+            int64_t subtotal = 0;
+            const payments::PaymentDetails& details = rcp.paymentRequest.getDetails();
+            for (int j = 0; j < details.outputs_size(); j++)
+            {
+                const payments::Output& out = details.outputs(j);
+                if (out.amount() <= 0) continue;
+                if (i == nChangePosRet)
+                    i++;
+                subtotal += walletTransaction->vout[i].nValue;
+                i++;
+            }
+            rcp.amount = subtotal;
+        }
+        else // normal recipient (no payment request)
+        {
+            if (i == nChangePosRet)
+                i++;
+            rcp.amount = walletTransaction->vout[i].nValue;
+            i++;
+        }
+    }
+}
+
 qint64 WalletModelTransaction::getTotalTransactionAmount()
 {
     qint64 totalTransactionAmount = 0;

src/qt/walletmodeltransaction.h

@@ -34,8 +34,10 @@ class WalletModelTransaction
     void newPossibleKeyChange(CWallet *wallet);
     CReserveKey *getPossibleKeyChange();
 
+    void reassignAmounts(int nChangePosRet); // needed for the subtract-fee-from-amount feature
+
 private:
-    const QList<SendCoinsRecipient> recipients;
+    QList<SendCoinsRecipient> recipients;
     CWalletTx *walletTransaction;
     CReserveKey *keyChange;
     qint64 fee;

src/rpcclient.cpp

@@ -32,6 +32,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "getnetworkhashps", 0 },
     { "getnetworkhashps", 1 },
     { "sendtoaddress", 1 },
+    { "sendtoaddress", 4 },
     { "settxfee", 0 },
     { "getreceivedbyaddress", 1 },
     { "getreceivedbyaccount", 1 },
@@ -48,6 +49,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "move", 3 },
     { "sendfrom", 2 },
     { "sendfrom", 3 },
+    { "sendfrom", 6 },
     { "listtransactions", 1 },
     { "listtransactions", 2 },
     { "listtransactions", 3 },
@@ -59,6 +61,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "listsinceblock", 2 },
     { "sendmany", 1 },
     { "sendmany", 2 },
+    { "sendmany", 4 },
     { "addmultisigaddress", 0 },
     { "addmultisigaddress", 1 },
     { "createmultisig", 0 },