Merge bitcoin-core/gui#556: refactor: Make BitcoinUnits::Unit a scoped enum

0e5dedbc9eb54105ab9b0c4ce1f57afa55bcb5b6 qt/wallettests: sort includes (William Casarin)
0554251d660caa1c3f5f44ae1d9fa3c23d2aac18 qt: Skip displayUnitChanged signal if unit is not actually changed (Hennadii Stepanov)
ffbc2fe459034024cb2fce9fd94bff457b7a7d49 qt, refactor: Remove default cases for scoped enum (Hennadii Stepanov)
152d5bad50f145af922011f6ec1fd9afd9076ceb qt, refactor: Remove BitcoinUnits::valid function (Hennadii Stepanov)
aa23960fdf1deff321ecea435026c87db78498fb qt, refactor: Make BitcoinUnits::Unit a scoped enum (Hennadii Stepanov)
75832fdc37ea3fe9cf515bd1946e220fe07a440b qt: Use QVariant instead of int for BitcoinUnit in QSettings (Hennadii Stepanov)

Pull request description:

  This is a rebased version of #60

  Since Qt 5.5 there are [means](https://doc.qt.io/qt-5/qobject.html#Q_ENUM) to register an enum type with the meta-object system (such enum still lacks an ability to interact with [QSettings::setValue()](https://doc.qt.io/qt-5/qsettings.html#setValue) and [QSettings::value()](https://doc.qt.io/qt-5/qsettings.html#value) without defined stream operators).

  In order to reduce global namespace polluting and to force strong type checking, this PR makes BitcoinUnits::Unit a scoped enum (typedef BitcoinUnits::Unit BitcoinUnit;).

  No behavior change.

ACKs for top commit:
  jonatack:
    ACK 0e5dedbc9eb54105ab9b0c4ce1f57afa55bcb5b6, review and debug build of each commit after rebase on current master, lightly tested running the GUI, changing units a few times, and verifying persistence after restarting
  promag:
    Code review ACK 0e5dedbc9eb54105ab9b0c4ce1f57afa55bcb5b6

Tree-SHA512: 39ec0d7e4f0b9b25be287888121a8db6b282339674e37ec3a3554da63a9e22d6fe079e8310ca289b2a0356a19b3c7e55afa17d09dd34e0f222177f603bb053a3

19 files changed, 188 insertions, 157 deletions

diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index c6b884e40a..8cac28400f 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -95,6 +95,8 @@ static void RegisterMetaTypes()
     qRegisterMetaType<std::function<void()>>("std::function<void()>");
     qRegisterMetaType<QMessageBox::Icon>("QMessageBox::Icon");
     qRegisterMetaType<interfaces::BlockAndHeaderTipInfo>("interfaces::BlockAndHeaderTipInfo");
+
+    qRegisterMetaTypeStreamOperators<BitcoinUnit>("BitcoinUnit");
 }
 
 static QString GetLangTerritory()
diff --git a/src/qt/bitcoinamountfield.cpp b/src/qt/bitcoinamountfield.cpp
index a257e250e0..527a8cd84b 100644
--- a/src/qt/bitcoinamountfield.cpp
+++ b/src/qt/bitcoinamountfield.cpp
@@ -14,6 +14,9 @@
 #include <QHBoxLayout>
 #include <QKeyEvent>
 #include <QLineEdit>
+#include <QVariant>
+
+#include <cassert>
 
 /** QSpinBox that uses fixed-point numbers internally and uses our own
  * formatting/parsing functions.
@@ -96,7 +99,7 @@ public:
         setValue(val);
     }
 
-    void setDisplayUnit(int unit)
+    void setDisplayUnit(BitcoinUnit unit)
     {
         bool valid = false;
         CAmount val = value(&valid);
@@ -122,7 +125,7 @@ public:
 
             const QFontMetrics fm(fontMetrics());
             int h = lineEdit()->minimumSizeHint().height();
-            int w = GUIUtil::TextWidth(fm, BitcoinUnits::format(BitcoinUnits::BTC, BitcoinUnits::maxMoney(), false, BitcoinUnits::SeparatorStyle::ALWAYS));
+            int w = GUIUtil::TextWidth(fm, BitcoinUnits::format(BitcoinUnit::BTC, BitcoinUnits::maxMoney(), false, BitcoinUnits::SeparatorStyle::ALWAYS));
             w += 2; // cursor blinking space
 
             QStyleOptionSpinBox opt;
@@ -148,7 +151,7 @@ public:
     }
 
 private:
-    int currentUnit{BitcoinUnits::BTC};
+    BitcoinUnit currentUnit{BitcoinUnit::BTC};
     CAmount singleStep{CAmount(100000)}; // satoshis
     mutable QSize cachedMinimumSizeHint;
     bool m_allow_empty{true};
@@ -326,14 +329,14 @@ void BitcoinAmountField::unitChanged(int idx)
     unit->setToolTip(unit->itemData(idx, Qt::ToolTipRole).toString());
 
     // Determine new unit ID
-    int newUnit = unit->itemData(idx, BitcoinUnits::UnitRole).toInt();
-
-    amount->setDisplayUnit(newUnit);
+    QVariant new_unit = unit->currentData(BitcoinUnits::UnitRole);
+    assert(new_unit.isValid());
+    amount->setDisplayUnit(new_unit.value<BitcoinUnit>());
 }
 
-void BitcoinAmountField::setDisplayUnit(int newUnit)
+void BitcoinAmountField::setDisplayUnit(BitcoinUnit new_unit)
 {
-    unit->setValue(newUnit);
+    unit->setValue(QVariant::fromValue(new_unit));
 }
 
 void BitcoinAmountField::setSingleStep(const CAmount& step)
diff --git a/src/qt/bitcoinamountfield.h b/src/qt/bitcoinamountfield.h
index 366a6fc4b5..a40cd38332 100644
--- a/src/qt/bitcoinamountfield.h
+++ b/src/qt/bitcoinamountfield.h
@@ -6,6 +6,7 @@
 #define BITCOIN_QT_BITCOINAMOUNTFIELD_H
 
 #include <consensus/amount.h>
+#include <qt/bitcoinunits.h>
 
 #include <QWidget>
 
@@ -52,7 +53,7 @@ public:
     bool validate();
 
     /** Change unit used to display amount. */
-    void setDisplayUnit(int unit);
+    void setDisplayUnit(BitcoinUnit new_unit);
 
     /** Make field empty and ready for new input. */
     void clear();
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index be0d33d667..81b0e711b2 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -1245,7 +1245,7 @@ void BitcoinGUI::showEvent(QShowEvent *event)
 }
 
 #ifdef ENABLE_WALLET
-void BitcoinGUI::incomingTransaction(const QString& date, int unit, const CAmount& amount, const QString& type, const QString& address, const QString& label, const QString& walletName)
+void BitcoinGUI::incomingTransaction(const QString& date, BitcoinUnit unit, const CAmount& amount, const QString& type, const QString& address, const QString& label, const QString& walletName)
 {
     // On new transaction, make an info balloon
     QString msg = tr("Date: %1\n").arg(date) +
@@ -1496,11 +1496,10 @@ UnitDisplayStatusBarControl::UnitDisplayStatusBarControl(const PlatformStyle *pl
 {
     createContextMenu();
     setToolTip(tr("Unit to show amounts in. Click to select another unit."));
-    QList<BitcoinUnits::Unit> units = BitcoinUnits::availableUnits();
+    QList<BitcoinUnit> units = BitcoinUnits::availableUnits();
     int max_width = 0;
     const QFontMetrics fm(font());
-    for (const BitcoinUnits::Unit unit : units)
-    {
+    for (const BitcoinUnit unit : units) {
         max_width = qMax(max_width, GUIUtil::TextWidth(fm, BitcoinUnits::longName(unit)));
     }
     setMinimumSize(max_width, 0);
@@ -1530,8 +1529,8 @@ void UnitDisplayStatusBarControl::changeEvent(QEvent* e)
 void UnitDisplayStatusBarControl::createContextMenu()
 {
     menu = new QMenu(this);
-    for (const BitcoinUnits::Unit u : BitcoinUnits::availableUnits()) {
-        menu->addAction(BitcoinUnits::longName(u))->setData(QVariant(u));
+    for (const BitcoinUnit u : BitcoinUnits::availableUnits()) {
+        menu->addAction(BitcoinUnits::longName(u))->setData(QVariant::fromValue(u));
     }
     connect(menu, &QMenu::triggered, this, &UnitDisplayStatusBarControl::onMenuSelection);
 }
@@ -1552,7 +1551,7 @@ void UnitDisplayStatusBarControl::setOptionsModel(OptionsModel *_optionsModel)
 }
 
 /** When Display Units are changed on OptionsModel it will refresh the display text of the control on the status bar */
-void UnitDisplayStatusBarControl::updateDisplayUnit(int newUnits)
+void UnitDisplayStatusBarControl::updateDisplayUnit(BitcoinUnit newUnits)
 {
     setText(BitcoinUnits::longName(newUnits));
 }
diff --git a/src/qt/bitcoingui.h b/src/qt/bitcoingui.h
index d2b29ba27b..5d9a978695 100644
--- a/src/qt/bitcoingui.h
+++ b/src/qt/bitcoingui.h
@@ -9,6 +9,7 @@
 #include <config/bitcoin-config.h>
 #endif
 
+#include <qt/bitcoinunits.h>
 #include <qt/guiutil.h>
 #include <qt/optionsdialog.h>
 
@@ -260,7 +261,7 @@ public Q_SLOTS:
     bool handlePaymentRequest(const SendCoinsRecipient& recipient);
 
     /** Show incoming transaction notification for new transactions. */
-    void incomingTransaction(const QString& date, int unit, const CAmount& amount, const QString& type, const QString& address, const QString& label, const QString& walletName);
+    void incomingTransaction(const QString& date, BitcoinUnit unit, const CAmount& amount, const QString& type, const QString& address, const QString& label, const QString& walletName);
 #endif // ENABLE_WALLET
 
 private:
@@ -341,7 +342,7 @@ private:
 
 private Q_SLOTS:
     /** When Display Units are changed on OptionsModel it will refresh the display text of the control on the status bar */
-    void updateDisplayUnit(int newUnits);
+    void updateDisplayUnit(BitcoinUnit newUnits);
     /** Tells underlying optionsModel to update its current display unit. */
     void onMenuSelection(QAction* action);
 };
diff --git a/src/qt/bitcoinunits.cpp b/src/qt/bitcoinunits.cpp
index 69caf64d5c..fe3eb3240b 100644
--- a/src/qt/bitcoinunits.cpp
+++ b/src/qt/bitcoinunits.cpp
@@ -18,94 +18,75 @@ BitcoinUnits::BitcoinUnits(QObject *parent):
 {
 }
 
-QList<BitcoinUnits::Unit> BitcoinUnits::availableUnits()
+QList<BitcoinUnit> BitcoinUnits::availableUnits()
 {
-    QList<BitcoinUnits::Unit> unitlist;
-    unitlist.append(BTC);
-    unitlist.append(mBTC);
-    unitlist.append(uBTC);
-    unitlist.append(SAT);
+    QList<BitcoinUnit> unitlist;
+    unitlist.append(Unit::BTC);
+    unitlist.append(Unit::mBTC);
+    unitlist.append(Unit::uBTC);
+    unitlist.append(Unit::SAT);
     return unitlist;
 }
 
-bool BitcoinUnits::valid(int unit)
+QString BitcoinUnits::longName(Unit unit)
 {
-    switch(unit)
-    {
-    case BTC:
-    case mBTC:
-    case uBTC:
-    case SAT:
-        return true;
-    default:
-        return false;
-    }
-}
-
-QString BitcoinUnits::longName(int unit)
-{
-    switch(unit)
-    {
-    case BTC: return QString("BTC");
-    case mBTC: return QString("mBTC");
-    case uBTC: return QString::fromUtf8("µBTC (bits)");
-    case SAT: return QString("Satoshi (sat)");
-    default: return QString("???");
-    }
+    switch (unit) {
+    case Unit::BTC: return QString("BTC");
+    case Unit::mBTC: return QString("mBTC");
+    case Unit::uBTC: return QString::fromUtf8("µBTC (bits)");
+    case Unit::SAT: return QString("Satoshi (sat)");
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
 }
 
-QString BitcoinUnits::shortName(int unit)
+QString BitcoinUnits::shortName(Unit unit)
 {
-    switch(unit)
-    {
-    case uBTC: return QString::fromUtf8("bits");
-    case SAT: return QString("sat");
-    default: return longName(unit);
-    }
+    switch (unit) {
+    case Unit::BTC: return longName(unit);
+    case Unit::mBTC: return longName(unit);
+    case Unit::uBTC: return QString("bits");
+    case Unit::SAT: return QString("sat");
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
 }
 
-QString BitcoinUnits::description(int unit)
+QString BitcoinUnits::description(Unit unit)
 {
-    switch(unit)
-    {
-    case BTC: return QString("Bitcoins");
-    case mBTC: return QString("Milli-Bitcoins (1 / 1" THIN_SP_UTF8 "000)");
-    case uBTC: return QString("Micro-Bitcoins (bits) (1 / 1" THIN_SP_UTF8 "000" THIN_SP_UTF8 "000)");
-    case SAT: return QString("Satoshi (sat) (1 / 100" THIN_SP_UTF8 "000" THIN_SP_UTF8 "000)");
-    default: return QString("???");
-    }
+    switch (unit) {
+    case Unit::BTC: return QString("Bitcoins");
+    case Unit::mBTC: return QString("Milli-Bitcoins (1 / 1" THIN_SP_UTF8 "000)");
+    case Unit::uBTC: return QString("Micro-Bitcoins (bits) (1 / 1" THIN_SP_UTF8 "000" THIN_SP_UTF8 "000)");
+    case Unit::SAT: return QString("Satoshi (sat) (1 / 100" THIN_SP_UTF8 "000" THIN_SP_UTF8 "000)");
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
 }
 
-qint64 BitcoinUnits::factor(int unit)
+qint64 BitcoinUnits::factor(Unit unit)
 {
-    switch(unit)
-    {
-    case BTC: return 100000000;
-    case mBTC: return 100000;
-    case uBTC: return 100;
-    case SAT: return 1;
-    default: return 100000000;
-    }
+    switch (unit) {
+    case Unit::BTC: return 100'000'000;
+    case Unit::mBTC: return 100'000;
+    case Unit::uBTC: return 100;
+    case Unit::SAT: return 1;
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
 }
 
-int BitcoinUnits::decimals(int unit)
+int BitcoinUnits::decimals(Unit unit)
 {
-    switch(unit)
-    {
-    case BTC: return 8;
-    case mBTC: return 5;
-    case uBTC: return 2;
-    case SAT: return 0;
-    default: return 0;
-    }
+    switch (unit) {
+    case Unit::BTC: return 8;
+    case Unit::mBTC: return 5;
+    case Unit::uBTC: return 2;
+    case Unit::SAT: return 0;
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
 }
 
-QString BitcoinUnits::format(int unit, const CAmount& nIn, bool fPlus, SeparatorStyle separators, bool justify)
+QString BitcoinUnits::format(Unit unit, const CAmount& nIn, bool fPlus, SeparatorStyle separators, bool justify)
 {
     // Note: not using straight sprintf here because we do NOT want
     // localized number formatting.
-    if(!valid(unit))
-        return QString(); // Refuse to format invalid unit
     qint64 n = (qint64)nIn;
     qint64 coin = factor(unit);
     int num_decimals = decimals(unit);
@@ -147,19 +128,19 @@ QString BitcoinUnits::format(int unit, const CAmount& nIn, bool fPlus, Separator
 // Please take care to use formatHtmlWithUnit instead, when
 // appropriate.
 
-QString BitcoinUnits::formatWithUnit(int unit, const CAmount& amount, bool plussign, SeparatorStyle separators)
+QString BitcoinUnits::formatWithUnit(Unit unit, const CAmount& amount, bool plussign, SeparatorStyle separators)
 {
     return format(unit, amount, plussign, separators) + QString(" ") + shortName(unit);
 }
 
-QString BitcoinUnits::formatHtmlWithUnit(int unit, const CAmount& amount, bool plussign, SeparatorStyle separators)
+QString BitcoinUnits::formatHtmlWithUnit(Unit unit, const CAmount& amount, bool plussign, SeparatorStyle separators)
 {
     QString str(formatWithUnit(unit, amount, plussign, separators));
     str.replace(QChar(THIN_SP_CP), QString(THIN_SP_HTML));
     return QString("<span style='white-space: nowrap;'>%1</span>").arg(str);
 }
 
-QString BitcoinUnits::formatWithPrivacy(int unit, const CAmount& amount, SeparatorStyle separators, bool privacy)
+QString BitcoinUnits::formatWithPrivacy(Unit unit, const CAmount& amount, SeparatorStyle separators, bool privacy)
 {
     assert(amount >= 0);
     QString value;
@@ -171,10 +152,11 @@ QString BitcoinUnits::formatWithPrivacy(int unit, const CAmount& amount, Separat
     return value + QString(" ") + shortName(unit);
 }
 
-bool BitcoinUnits::parse(int unit, const QString &value, CAmount *val_out)
+bool BitcoinUnits::parse(Unit unit, const QString& value, CAmount* val_out)
 {
-    if(!valid(unit) || value.isEmpty())
+    if (value.isEmpty()) {
         return false; // Refuse to parse invalid unit or empty string
+    }
     int num_decimals = decimals(unit);
 
     // Ignore spaces and thin spaces when parsing
@@ -210,14 +192,9 @@ bool BitcoinUnits::parse(int unit, const QString &value, CAmount *val_out)
     return ok;
 }
 
-QString BitcoinUnits::getAmountColumnTitle(int unit)
+QString BitcoinUnits::getAmountColumnTitle(Unit unit)
 {
-    QString amountTitle = QObject::tr("Amount");
-    if (BitcoinUnits::valid(unit))
-    {
-        amountTitle += " ("+BitcoinUnits::shortName(unit) + ")";
-    }
-    return amountTitle;
+    return QObject::tr("Amount") + " (" + shortName(unit) + ")";
 }
 
 int BitcoinUnits::rowCount(const QModelIndex &parent) const
@@ -240,7 +217,7 @@ QVariant BitcoinUnits::data(const QModelIndex &index, int role) const
         case Qt::ToolTipRole:
             return QVariant(description(unit));
         case UnitRole:
-            return QVariant(static_cast<int>(unit));
+            return QVariant::fromValue(unit);
         }
     }
     return QVariant();
@@ -250,3 +227,40 @@ CAmount BitcoinUnits::maxMoney()
 {
     return MAX_MONEY;
 }
+
+namespace {
+qint8 ToQint8(BitcoinUnit unit)
+{
+    switch (unit) {
+    case BitcoinUnit::BTC: return 0;
+    case BitcoinUnit::mBTC: return 1;
+    case BitcoinUnit::uBTC: return 2;
+    case BitcoinUnit::SAT: return 3;
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
+}
+
+BitcoinUnit FromQint8(qint8 num)
+{
+    switch (num) {
+    case 0: return BitcoinUnit::BTC;
+    case 1: return BitcoinUnit::mBTC;
+    case 2: return BitcoinUnit::uBTC;
+    case 3: return BitcoinUnit::SAT;
+    }
+    assert(false);
+}
+} // namespace
+
+QDataStream& operator<<(QDataStream& out, const BitcoinUnit& unit)
+{
+    return out << ToQint8(unit);
+}
+
+QDataStream& operator>>(QDataStream& in, BitcoinUnit& unit)
+{
+    qint8 input;
+    in >> input;
+    unit = FromQint8(input);
+    return in;
+}
diff --git a/src/qt/bitcoinunits.h b/src/qt/bitcoinunits.h
index 9fedec0d4f..b3b5a8fc18 100644
--- a/src/qt/bitcoinunits.h
+++ b/src/qt/bitcoinunits.h
@@ -8,6 +8,7 @@
 #include <consensus/amount.h>
 
 #include <QAbstractListModel>
+#include <QDataStream>
 #include <QString>
 
 // U+2009 THIN SPACE = UTF-8 E2 80 89
@@ -38,13 +39,13 @@ public:
     /** Bitcoin units.
       @note Source: https://en.bitcoin.it/wiki/Units . Please add only sensible ones
      */
-    enum Unit
-    {
+    enum class Unit {
         BTC,
         mBTC,
         uBTC,
         SAT
     };
+    Q_ENUM(Unit)
 
     enum class SeparatorStyle
     {
@@ -59,30 +60,28 @@ public:
 
     //! Get list of units, for drop-down box
     static QList<Unit> availableUnits();
-    //! Is unit ID valid?
-    static bool valid(int unit);
     //! Long name
-    static QString longName(int unit);
+    static QString longName(Unit unit);
     //! Short name
-    static QString shortName(int unit);
+    static QString shortName(Unit unit);
     //! Longer description
-    static QString description(int unit);
+    static QString description(Unit unit);
     //! Number of Satoshis (1e-8) per unit
-    static qint64 factor(int unit);
+    static qint64 factor(Unit unit);
     //! Number of decimals left
-    static int decimals(int unit);
+    static int decimals(Unit unit);
     //! Format as string
-    static QString format(int unit, const CAmount& amount, bool plussign = false, SeparatorStyle separators = SeparatorStyle::STANDARD, bool justify = false);
+    static QString format(Unit unit, const CAmount& amount, bool plussign = false, SeparatorStyle separators = SeparatorStyle::STANDARD, bool justify = false);
     //! Format as string (with unit)
-    static QString formatWithUnit(int unit, const CAmount& amount, bool plussign=false, SeparatorStyle separators=SeparatorStyle::STANDARD);
+    static QString formatWithUnit(Unit unit, const CAmount& amount, bool plussign = false, SeparatorStyle separators = SeparatorStyle::STANDARD);
     //! Format as HTML string (with unit)
-    static QString formatHtmlWithUnit(int unit, const CAmount& amount, bool plussign=false, SeparatorStyle separators=SeparatorStyle::STANDARD);
+    static QString formatHtmlWithUnit(Unit unit, const CAmount& amount, bool plussign = false, SeparatorStyle separators = SeparatorStyle::STANDARD);
     //! Format as string (with unit) of fixed length to preserve privacy, if it is set.
-    static QString formatWithPrivacy(int unit, const CAmount& amount, SeparatorStyle separators, bool privacy);
+    static QString formatWithPrivacy(Unit unit, const CAmount& amount, SeparatorStyle separators, bool privacy);
     //! Parse string to coin amount
-    static bool parse(int unit, const QString &value, CAmount *val_out);
+    static bool parse(Unit unit, const QString& value, CAmount* val_out);
     //! Gets title for amount column including current display unit if optionsModel reference available */
-    static QString getAmountColumnTitle(int unit);
+    static QString getAmountColumnTitle(Unit unit);
     ///@}
 
     //! @name AbstractListModel implementation
@@ -107,8 +106,11 @@ public:
     static CAmount maxMoney();
 
 private:
-    QList<BitcoinUnits::Unit> unitlist;
+    QList<Unit> unitlist;
 };
 typedef BitcoinUnits::Unit BitcoinUnit;
 
+QDataStream& operator<<(QDataStream& out, const BitcoinUnit& unit);
+QDataStream& operator>>(QDataStream& in, BitcoinUnit& unit);
+
 #endif // BITCOIN_QT_BITCOINUNITS_H
diff --git a/src/qt/coincontroldialog.cpp b/src/qt/coincontroldialog.cpp
index 07c3e62a03..bd9a90a890 100644
--- a/src/qt/coincontroldialog.cpp
+++ b/src/qt/coincontroldialog.cpp
@@ -507,7 +507,7 @@ void CoinControlDialog::updateLabels(CCoinControl& m_coin_control, WalletModel *
     }
 
     // actually update labels
-    int nDisplayUnit = BitcoinUnits::BTC;
+    BitcoinUnit nDisplayUnit = BitcoinUnit::BTC;
     if (model && model->getOptionsModel())
         nDisplayUnit = model->getOptionsModel()->getDisplayUnit();
 
@@ -590,7 +590,7 @@ void CoinControlDialog::updateView()
     QFlags<Qt::ItemFlag> flgCheckbox = Qt::ItemIsSelectable | Qt::ItemIsEnabled | Qt::ItemIsUserCheckable;
     QFlags<Qt::ItemFlag> flgTristate = Qt::ItemIsSelectable | Qt::ItemIsEnabled | Qt::ItemIsUserCheckable | Qt::ItemIsAutoTristate;
 
-    int nDisplayUnit = model->getOptionsModel()->getDisplayUnit();
+    BitcoinUnit nDisplayUnit = model->getOptionsModel()->getDisplayUnit();
 
     for (const auto& coins : model->wallet().listCoins()) {
         CCoinControlWidgetItem* itemWalletAddress{nullptr};
diff --git a/src/qt/guiutil.cpp b/src/qt/guiutil.cpp
index ca0b8c20f0..6fb5fce5b3 100644
--- a/src/qt/guiutil.cpp
+++ b/src/qt/guiutil.cpp
@@ -178,8 +178,7 @@ bool parseBitcoinURI(const QUrl &uri, SendCoinsRecipient *out)
         {
             if(!i->second.isEmpty())
             {
-                if(!BitcoinUnits::parse(BitcoinUnits::BTC, i->second, &rv.amount))
-                {
+                if (!BitcoinUnits::parse(BitcoinUnit::BTC, i->second, &rv.amount)) {
                     return false;
                 }
             }
@@ -211,7 +210,7 @@ QString formatBitcoinURI(const SendCoinsRecipient &info)
 
     if (info.amount)
     {
-        ret += QString("?amount=%1").arg(BitcoinUnits::format(BitcoinUnits::BTC, info.amount, false, BitcoinUnits::SeparatorStyle::NEVER));
+        ret += QString("?amount=%1").arg(BitcoinUnits::format(BitcoinUnit::BTC, info.amount, false, BitcoinUnits::SeparatorStyle::NEVER));
         paramCount++;
     }
 
diff --git a/src/qt/optionsmodel.cpp b/src/qt/optionsmodel.cpp
index 52bda59748..40b9ed5483 100644
--- a/src/qt/optionsmodel.cpp
+++ b/src/qt/optionsmodel.cpp
@@ -24,6 +24,7 @@
 #include <QLatin1Char>
 #include <QSettings>
 #include <QStringList>
+#include <QVariant>
 
 const char *DEFAULT_GUI_PROXY_HOST = "127.0.0.1";
 
@@ -71,9 +72,16 @@ void OptionsModel::Init(bool resetSettings)
     fMinimizeOnClose = settings.value("fMinimizeOnClose").toBool();
 
     // Display
-    if (!settings.contains("nDisplayUnit"))
-        settings.setValue("nDisplayUnit", BitcoinUnits::BTC);
-    nDisplayUnit = settings.value("nDisplayUnit").toInt();
+    if (!settings.contains("DisplayBitcoinUnit")) {
+        settings.setValue("DisplayBitcoinUnit", QVariant::fromValue(BitcoinUnit::BTC));
+    }
+    QVariant unit = settings.value("DisplayBitcoinUnit");
+    if (unit.canConvert<BitcoinUnit>()) {
+        m_display_bitcoin_unit = unit.value<BitcoinUnit>();
+    } else {
+        m_display_bitcoin_unit = BitcoinUnit::BTC;
+        settings.setValue("DisplayBitcoinUnit", QVariant::fromValue(m_display_bitcoin_unit));
+    }
 
     if (!settings.contains("strThirdPartyTxUrls"))
         settings.setValue("strThirdPartyTxUrls", "");
@@ -376,7 +384,7 @@ QVariant OptionsModel::data(const QModelIndex & index, int role) const
             return m_sub_fee_from_amount;
 #endif
         case DisplayUnit:
-            return nDisplayUnit;
+            return QVariant::fromValue(m_display_bitcoin_unit);
         case ThirdPartyTxUrls:
             return strThirdPartyTxUrls;
         case Language:
@@ -584,16 +592,13 @@ bool OptionsModel::setData(const QModelIndex & index, const QVariant & value, in
     return successful;
 }
 
-/** Updates current unit in memory, settings and emits displayUnitChanged(newUnit) signal */
-void OptionsModel::setDisplayUnit(const QVariant &value)
+void OptionsModel::setDisplayUnit(const QVariant& new_unit)
 {
-    if (!value.isNull())
-    {
-        QSettings settings;
-        nDisplayUnit = value.toInt();
-        settings.setValue("nDisplayUnit", nDisplayUnit);
-        Q_EMIT displayUnitChanged(nDisplayUnit);
-    }
+    if (new_unit.isNull() || new_unit.value<BitcoinUnit>() == m_display_bitcoin_unit) return;
+    m_display_bitcoin_unit = new_unit.value<BitcoinUnit>();
+    QSettings settings;
+    settings.setValue("DisplayBitcoinUnit", QVariant::fromValue(m_display_bitcoin_unit));
+    Q_EMIT displayUnitChanged(m_display_bitcoin_unit);
 }
 
 void OptionsModel::setRestartRequired(bool fRequired)
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
index bb9a8c1f8c..510ebb5cfd 100644
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -6,6 +6,7 @@
 #define BITCOIN_QT_OPTIONSMODEL_H
 
 #include <cstdint>
+#include <qt/bitcoinunits.h>
 #include <qt/guiconstants.h>
 
 #include <QAbstractListModel>
@@ -55,7 +56,7 @@ public:
         ProxyUseTor,            // bool
         ProxyIPTor,             // QString
         ProxyPortTor,           // int
-        DisplayUnit,            // BitcoinUnits::Unit
+        DisplayUnit,            // BitcoinUnit
         ThirdPartyTxUrls,       // QString
         Language,               // QString
         UseEmbeddedMonospacedFont, // bool
@@ -79,14 +80,14 @@ public:
     int rowCount(const QModelIndex & parent = QModelIndex()) const override;
     QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const override;
     bool setData(const QModelIndex & index, const QVariant & value, int role = Qt::EditRole) override;
-    /** Updates current unit in memory, settings and emits displayUnitChanged(newUnit) signal */
-    void setDisplayUnit(const QVariant &value);
+    /** Updates current unit in memory, settings and emits displayUnitChanged(new_unit) signal */
+    void setDisplayUnit(const QVariant& new_unit);
 
     /* Explicit getters */
     bool getShowTrayIcon() const { return m_show_tray_icon; }
     bool getMinimizeToTray() const { return fMinimizeToTray; }
     bool getMinimizeOnClose() const { return fMinimizeOnClose; }
-    int getDisplayUnit() const { return nDisplayUnit; }
+    BitcoinUnit getDisplayUnit() const { return m_display_bitcoin_unit; }
     QString getThirdPartyTxUrls() const { return strThirdPartyTxUrls; }
     bool getUseEmbeddedMonospacedFont() const { return m_use_embedded_monospaced_font; }
     bool getCoinControlFeatures() const { return fCoinControlFeatures; }
@@ -112,7 +113,7 @@ private:
     bool fMinimizeToTray;
     bool fMinimizeOnClose;
     QString language;
-    int nDisplayUnit;
+    BitcoinUnit m_display_bitcoin_unit;
     QString strThirdPartyTxUrls;
     bool m_use_embedded_monospaced_font;
     bool fCoinControlFeatures;
@@ -127,7 +128,7 @@ private:
     // Check settings version and upgrade default values if required
     void checkAndMigrate();
 Q_SIGNALS:
-    void displayUnitChanged(int unit);
+    void displayUnitChanged(BitcoinUnit unit);
     void coinControlFeaturesChanged(bool);
     void showTrayIconChanged(bool);
     void useEmbeddedMonospacedFontChanged(bool);
diff --git a/src/qt/overviewpage.cpp b/src/qt/overviewpage.cpp
index 7127706463..820bcbf3cd 100644
--- a/src/qt/overviewpage.cpp
+++ b/src/qt/overviewpage.cpp
@@ -34,9 +34,9 @@ class TxViewDelegate : public QAbstractItemDelegate
 {
     Q_OBJECT
 public:
-    explicit TxViewDelegate(const PlatformStyle *_platformStyle, QObject *parent=nullptr):
-        QAbstractItemDelegate(parent), unit(BitcoinUnits::BTC),
-        platformStyle(_platformStyle)
+    explicit TxViewDelegate(const PlatformStyle* _platformStyle, QObject* parent = nullptr)
+        : QAbstractItemDelegate(parent), unit(BitcoinUnit::BTC),
+          platformStyle(_platformStyle)
     {
         connect(this, &TxViewDelegate::width_changed, this, &TxViewDelegate::sizeHintChanged);
     }
@@ -125,7 +125,7 @@ public:
         return {DECORATION_SIZE + 8 + minimum_text_width, DECORATION_SIZE};
     }
 
-    int unit;
+    BitcoinUnit unit;
 
 Q_SIGNALS:
     //! An intermediate signal for emitting from the `paint() const` member function.
@@ -197,7 +197,7 @@ OverviewPage::~OverviewPage()
 
 void OverviewPage::setBalance(const interfaces::WalletBalances& balances)
 {
-    int unit = walletModel->getOptionsModel()->getDisplayUnit();
+    BitcoinUnit unit = walletModel->getOptionsModel()->getDisplayUnit();
     m_balances = balances;
     if (walletModel->wallet().isLegacy()) {
         if (walletModel->wallet().privateKeysDisabled()) {
diff --git a/src/qt/psbtoperationsdialog.cpp b/src/qt/psbtoperationsdialog.cpp
index 6880c157c0..333766ce21 100644
--- a/src/qt/psbtoperationsdialog.cpp
+++ b/src/qt/psbtoperationsdialog.cpp
@@ -181,7 +181,7 @@ std::string PSBTOperationsDialog::renderTransaction(const PartiallySignedTransac
         ExtractDestination(out.scriptPubKey, address);
         totalAmount += out.nValue;
         tx_description.append(tr(" * Sends %1 to %2")
-            .arg(BitcoinUnits::formatWithUnit(BitcoinUnits::BTC, out.nValue))
+            .arg(BitcoinUnits::formatWithUnit(BitcoinUnit::BTC, out.nValue))
             .arg(QString::fromStdString(EncodeDestination(address))));
         tx_description.append("<br>");
     }
@@ -193,7 +193,7 @@ std::string PSBTOperationsDialog::renderTransaction(const PartiallySignedTransac
         tx_description.append(tr("Unable to calculate transaction fee or total transaction amount."));
     } else {
         tx_description.append(tr("Pays transaction fee: "));
-        tx_description.append(BitcoinUnits::formatWithUnit(BitcoinUnits::BTC, *analysis.fee));
+        tx_description.append(BitcoinUnits::formatWithUnit(BitcoinUnit::BTC, *analysis.fee));
 
         // add total amount in all subdivision units
         tx_description.append("<hr />");
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index c924789796..fd8eccb86d 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -380,8 +380,7 @@ bool SendCoinsDialog::PrepareSendText(QString& question_string, QString& informa
     question_string.append("<hr />");
     CAmount totalAmount = m_current_transaction->getTotalTransactionAmount() + txFee;
     QStringList alternativeUnits;
-    for (const BitcoinUnits::Unit u : BitcoinUnits::availableUnits())
-    {
+    for (const BitcoinUnit u : BitcoinUnits::availableUnits()) {
         if(u != model->getOptionsModel()->getDisplayUnit())
             alternativeUnits.append(BitcoinUnits::formatHtmlWithUnit(u, totalAmount));
     }
diff --git a/src/qt/test/wallettests.cpp b/src/qt/test/wallettests.cpp
index 6ab534764b..c4cd0f4cd1 100644
--- a/src/qt/test/wallettests.cpp
+++ b/src/qt/test/wallettests.cpp
@@ -7,24 +7,25 @@
 
 #include <interfaces/chain.h>
 #include <interfaces/node.h>
+#include <key_io.h>
 #include <qt/bitcoinamountfield.h>
+#include <qt/bitcoinunits.h>
 #include <qt/clientmodel.h>
 #include <qt/optionsmodel.h>
+#include <qt/overviewpage.h>
 #include <qt/platformstyle.h>
 #include <qt/qvalidatedlineedit.h>
+#include <qt/receivecoinsdialog.h>
+#include <qt/receiverequestdialog.h>
+#include <qt/recentrequeststablemodel.h>
 #include <qt/sendcoinsdialog.h>
 #include <qt/sendcoinsentry.h>
 #include <qt/transactiontablemodel.h>
 #include <qt/transactionview.h>
 #include <qt/walletmodel.h>
-#include <key_io.h>
 #include <test/util/setup_common.h>
 #include <validation.h>
 #include <wallet/wallet.h>
-#include <qt/overviewpage.h>
-#include <qt/receivecoinsdialog.h>
-#include <qt/recentrequeststablemodel.h>
-#include <qt/receiverequestdialog.h>
 
 #include <chrono>
 #include <memory>
@@ -196,7 +197,7 @@ void TestGUI(interfaces::Node& node)
         // Check balance in send dialog
         QLabel* balanceLabel = sendCoinsDialog.findChild<QLabel*>("labelBalance");
         QString balanceText = balanceLabel->text();
-        int unit = walletModel.getOptionsModel()->getDisplayUnit();
+        BitcoinUnit unit = walletModel.getOptionsModel()->getDisplayUnit();
         CAmount balance = walletModel.wallet().getBalance();
         QString balanceComparison = BitcoinUnits::formatWithUnit(unit, balance, false, BitcoinUnits::SeparatorStyle::ALWAYS);
         QCOMPARE(balanceText, balanceComparison);
@@ -222,7 +223,7 @@ void TestGUI(interfaces::Node& node)
     overviewPage.setWalletModel(&walletModel);
     QLabel* balanceLabel = overviewPage.findChild<QLabel*>("labelBalance");
     QString balanceText = balanceLabel->text().trimmed();
-    int unit = walletModel.getOptionsModel()->getDisplayUnit();
+    BitcoinUnit unit = walletModel.getOptionsModel()->getDisplayUnit();
     CAmount balance = walletModel.wallet().getBalance();
     QString balanceComparison = BitcoinUnits::formatWithUnit(unit, balance, false, BitcoinUnits::SeparatorStyle::ALWAYS);
     QCOMPARE(balanceText, balanceComparison);
diff --git a/src/qt/transactiondesc.cpp b/src/qt/transactiondesc.cpp
index 142db592ab..9e92f89543 100644
--- a/src/qt/transactiondesc.cpp
+++ b/src/qt/transactiondesc.cpp
@@ -75,7 +75,7 @@ bool GetPaymentRequestMerchant(const std::string& pr, QString& merchant)
     return false;
 }
 
-QString TransactionDesc::toHTML(interfaces::Node& node, interfaces::Wallet& wallet, TransactionRecord *rec, int unit)
+QString TransactionDesc::toHTML(interfaces::Node& node, interfaces::Wallet& wallet, TransactionRecord* rec, BitcoinUnit unit)
 {
     int numBlocks;
     interfaces::WalletTxStatus status;
diff --git a/src/qt/transactiondesc.h b/src/qt/transactiondesc.h
index 91c257e519..803e41b699 100644
--- a/src/qt/transactiondesc.h
+++ b/src/qt/transactiondesc.h
@@ -5,6 +5,8 @@
 #ifndef BITCOIN_QT_TRANSACTIONDESC_H
 #define BITCOIN_QT_TRANSACTIONDESC_H
 
+#include <qt/bitcoinunits.h>
+
 #include <QObject>
 #include <QString>
 
@@ -24,7 +26,7 @@ class TransactionDesc: public QObject
     Q_OBJECT
 
 public:
-    static QString toHTML(interfaces::Node& node, interfaces::Wallet& wallet, TransactionRecord *rec, int unit);
+    static QString toHTML(interfaces::Node& node, interfaces::Wallet& wallet, TransactionRecord* rec, BitcoinUnit unit);
 
 private:
     TransactionDesc() {}
diff --git a/src/qt/transactiontablemodel.cpp b/src/qt/transactiontablemodel.cpp
index 6b0495f5a8..7b932890cf 100644
--- a/src/qt/transactiontablemodel.cpp
+++ b/src/qt/transactiontablemodel.cpp
@@ -5,6 +5,7 @@
 #include <qt/transactiontablemodel.h>
 
 #include <qt/addresstablemodel.h>
+#include <qt/bitcoinunits.h>
 #include <qt/clientmodel.h>
 #include <qt/guiconstants.h>
 #include <qt/guiutil.h>
@@ -232,7 +233,7 @@ public:
         return nullptr;
     }
 
-    QString describe(interfaces::Node& node, interfaces::Wallet& wallet, TransactionRecord *rec, int unit)
+    QString describe(interfaces::Node& node, interfaces::Wallet& wallet, TransactionRecord* rec, BitcoinUnit unit)
     {
         return TransactionDesc::toHTML(node, wallet, rec, unit);
     }
diff --git a/src/qt/walletview.h b/src/qt/walletview.h
index 2f9d344bc8..301084ffa9 100644
--- a/src/qt/walletview.h
+++ b/src/qt/walletview.h
@@ -6,6 +6,7 @@
 #define BITCOIN_QT_WALLETVIEW_H
 
 #include <consensus/amount.h>
+#include <qt/bitcoinunits.h>
 
 #include <QStackedWidget>
 
@@ -115,7 +116,7 @@ Q_SIGNALS:
     /** Encryption status of wallet changed */
     void encryptionStatusChanged();
     /** Notify that a new transaction appeared */
-    void incomingTransaction(const QString& date, int unit, const CAmount& amount, const QString& type, const QString& address, const QString& label, const QString& walletName);
+    void incomingTransaction(const QString& date, BitcoinUnit unit, const CAmount& amount, const QString& type, const QString& address, const QString& label, const QString& walletName);
     /** Notify that the out of sync warning icon has been pressed */
     void outOfSyncWarningClicked();
 };