Auto shielding for t Addresses

src/mainwindow.cpp

@@ -387,6 +387,9 @@ void MainWindow::setupSettingsModal() {
         // Custom fees
         settings.chkCustomFees->setChecked(Settings::getInstance()->getAllowCustomFees());
 
+        // Auto shielding
+        settings.chkAutoShield->setChecked(Settings::getInstance()->getAutoShield());
+
         // Connection Settings
         QIntValidator validator(0, 65535);
         settings.port->setValidator(&validator);
@@ -426,6 +429,9 @@ void MainWindow::setupSettingsModal() {
             if (!customFees)
                 ui->minerFeeAmt->setText(Settings::getDecimalString(Settings::getMinerFee()));
 
+            // Auto shield
+            Settings::getInstance()->setAutoShield(settings.chkAutoShield->isChecked());
+
             if (zcashConfLocation.isEmpty()) {
                 // Save settings
                 Settings::getInstance()->saveSettings(
@@ -567,6 +573,7 @@ void MainWindow::postToZBoard() {
         auto toAddr = topics[zb.topicsList->currentText()];
         tx.toAddrs.push_back(ToFields{ toAddr, Settings::getZboardAmount(), memo, memo.toUtf8().toHex() });
         tx.fee = Settings::getMinerFee();
+        tx.sendChangeToSapling = false;
 
         json params = json::array();
         rpc->fillTxJsonParams(params, tx);

src/mainwindow.h

@@ -23,6 +23,7 @@ struct Tx {
     QString         fromAddr;
     QList<ToFields> toAddrs;
     double          fee;
+    bool            sendChangeToSapling;
 };
 
 namespace Ui {

src/sendtab.cpp

@@ -363,17 +363,26 @@ void MainWindow::maxAmountChecked(int checked) {
 // Create a Tx from the current state of the send page. 
 Tx MainWindow::createTxFromSendPage() {
     Tx tx;
+
+    bool sendChangeToSapling = Settings::getInstance()->getAutoShield();
+
     // Gather the from / to addresses 
     tx.fromAddr = ui->inputsCombo->currentText();
+    sendChangeToSapling = sendChangeToSapling && Settings::isTAddress(tx.fromAddr);
 
     // For each addr/amt in the sendTo tab
     int totalItems = ui->sendToWidgets->children().size() - 2;   // The last one is a spacer, so ignore that        
+    double totalAmt = 0;
     for (int i=0; i < totalItems; i++) {
         QString addr = ui->sendToWidgets->findChild<QLineEdit*>(QString("Address") % QString::number(i+1))->text().trimmed();
         // Remove label if it exists
         addr = AddressBook::addressFromAddressLabel(addr);
+        
+        // If address is sprout, then we can't send change to sapling, because of turnstile.
+        sendChangeToSapling = sendChangeToSapling && !Settings::getInstance()->isSproutAddress(addr);
 
         double  amt  = ui->sendToWidgets->findChild<QLineEdit*>(QString("Amount")  % QString::number(i+1))->text().trimmed().toDouble();        
+        totalAmt += amt;
         QString memo = ui->sendToWidgets->findChild<QLabel*>(QString("MemoTxt")  % QString::number(i+1))->text().trimmed();
         
         tx.toAddrs.push_back( ToFields{addr, amt, memo, memo.toUtf8().toHex()} );
@@ -381,10 +390,34 @@ Tx MainWindow::createTxFromSendPage() {
 
     if (Settings::getInstance()->getAllowCustomFees()) {
         tx.fee = ui->minerFeeAmt->text().toDouble();
-    } else {
+    }
+    else {
         tx.fee = Settings::getMinerFee();
     }
 
+    if (sendChangeToSapling) {
+        auto saplingAddr = std::find_if(rpc->getAllZAddresses()->begin(), rpc->getAllZAddresses()->end(), [=](auto i) -> bool { 
+            // We're finding a sapling address that is not one of the To addresses, because zcash doesn't allow duplicated addresses
+            bool isSapling = Settings::getInstance()->isSaplingAddress(i); 
+            if (!isSapling) return false;
+
+            // Also check all the To addresses
+            for (auto t : tx.toAddrs) {
+                if (t.addr == i)
+                    return false;
+            }
+
+            return true;
+        });
+        if (saplingAddr != rpc->getAllZAddresses()->end()) {
+            tx.sendChangeToSapling = sendChangeToSapling;
+            double change = rpc->getAllBalances()->value(tx.fromAddr) - totalAmt - tx.fee;
+
+            QString changeMemo = "change from " + tx.fromAddr;
+            tx.toAddrs.push_back( ToFields{*saplingAddr, change, changeMemo, changeMemo.toUtf8().toHex()} );
+        }
+    }
+    
     return tx;
 }
 

src/settings.cpp

@@ -66,6 +66,10 @@ bool Settings::isZAddress(QString addr) {
     return addr.startsWith("z");
 }
 
+bool Settings::isTAddress(QString addr) {
+    return addr.startsWith("t");
+}
+
 bool Settings::isSyncing() {
     return _isSyncing;
 }
@@ -91,6 +95,14 @@ double Settings::getZECPrice() {
     return zecPrice; 
 }
 
+bool Settings::getAutoShield() {
+    // Load from Qt settings
+    return QSettings().value("options/autoshield", false).toBool();
+}
+
+void Settings::setAutoShield(bool allow) {
+    QSettings().setValue("options/autoshield", allow);
+}
 
 bool Settings::getAllowCustomFees() {
     // Load from the QT Settings. 

src/settings.h

@@ -27,7 +27,6 @@ public:
             
     bool    isSaplingAddress(QString addr);
     bool    isSproutAddress(QString addr);
-    bool    isZAddress(QString addr);
             
     bool    isSyncing();
     void    setSyncing(bool syncing);
@@ -40,7 +39,10 @@ public:
             
     bool    getSaveZtxs();
     void    setSaveZtxs(bool save);
-            
+
+    bool    getAutoShield();
+    void    setAutoShield(bool allow);
+
     bool    getAllowCustomFees();
     void    setAllowCustomFees(bool allow);
             
@@ -57,6 +59,9 @@ public:
     
     static void saveRestore(QDialog* d);
 
+    static bool    isZAddress(QString addr);
+    static bool    isTAddress(QString addr);
+
     static QString getDecimalString(double amt);
     static QString getUSDFormat(double bal);
     static QString getZECDisplayFormat(double bal);

src/settings.ui

@@ -139,19 +139,6 @@
        <string>Options</string>
       </attribute>
       <layout class="QGridLayout" name="gridLayout">
-       <item row="2" column="0">
-        <spacer name="horizontalSpacer">
-         <property name="orientation">
-          <enum>Qt::Horizontal</enum>
-         </property>
-         <property name="sizeHint" stdset="0">
-          <size>
-           <width>40</width>
-           <height>20</height>
-          </size>
-         </property>
-        </spacer>
-       </item>
        <item row="1" column="0" colspan="2">
         <widget class="QLabel" name="label_5">
          <property name="text">
@@ -169,6 +156,19 @@
          </property>
         </widget>
        </item>
+       <item row="2" column="0">
+        <spacer name="horizontalSpacer">
+         <property name="orientation">
+          <enum>Qt::Horizontal</enum>
+         </property>
+         <property name="sizeHint" stdset="0">
+          <size>
+           <width>40</width>
+           <height>20</height>
+          </size>
+         </property>
+        </spacer>
+       </item>
        <item row="0" column="0" colspan="2">
         <widget class="QCheckBox" name="chkSaveTxs">
          <property name="text">
@@ -176,7 +176,14 @@
          </property>
         </widget>
        </item>
-       <item row="6" column="0" colspan="2">
+       <item row="8" column="0" colspan="2">
+        <widget class="Line" name="line_2">
+         <property name="orientation">
+          <enum>Qt::Horizontal</enum>
+         </property>
+        </widget>
+       </item>
+       <item row="9" column="0" colspan="2">
         <spacer name="verticalSpacer_2">
          <property name="orientation">
           <enum>Qt::Vertical</enum>
@@ -189,13 +196,6 @@
          </property>
         </spacer>
        </item>
-       <item row="5" column="0" colspan="2">
-        <widget class="Line" name="line_2">
-         <property name="orientation">
-          <enum>Qt::Horizontal</enum>
-         </property>
-        </widget>
-       </item>
        <item row="3" column="0">
         <widget class="QCheckBox" name="chkCustomFees">
          <property name="text">
@@ -213,6 +213,30 @@
          </property>
         </widget>
        </item>
+       <item row="7" column="0" colspan="2">
+        <widget class="QLabel" name="label_7">
+         <property name="text">
+          <string>Normally, change from t-Addresses goes to another t-Address. Checking this option will send the change to your shielded Sapling address instead. Check this option to increase your privacy.</string>
+         </property>
+         <property name="wordWrap">
+          <bool>true</bool>
+         </property>
+        </widget>
+       </item>
+       <item row="6" column="0" colspan="2">
+        <widget class="QCheckBox" name="chkAutoShield">
+         <property name="text">
+          <string>Shield change from t-Addresses to your Sapling addresses</string>
+         </property>
+        </widget>
+       </item>
+       <item row="5" column="0">
+        <widget class="QLabel" name="label_8">
+         <property name="text">
+          <string/>
+         </property>
+        </widget>
+       </item>
       </layout>
      </widget>
     </widget>

src/turnstile.cpp

@@ -304,7 +304,7 @@ void Turnstile::executeMigrationStep() {
         }
 
         // Create the Tx
-        auto tx = Tx{ nextStep->fromAddr, { to }, Settings::getMinerFee() };
+        auto tx = Tx{ nextStep->fromAddr, { to }, Settings::getMinerFee(), false };
 
         // And send it
         doSendTx(tx, [=] () {
@@ -339,7 +339,7 @@ void Turnstile::executeMigrationStep() {
         QList<ToFields> to = { ToFields{ nextStep->destAddr, sendAmt, "", "" } };
 
         // Create the Tx
-        auto tx = Tx{ nextStep->intTAddr, to, Settings::getMinerFee() };
+        auto tx = Tx{ nextStep->intTAddr, to, Settings::getMinerFee(), false };
 
         // And send it
         doSendTx(tx, [=] () {