qt: Use QVariant instead of int for BitcoinUnit in QSettings

This change improves type safety.

Author: hebasto

src/qt/bitcoin.cpp

@@ -85,6 +85,8 @@ 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()

src/qt/bitcoinunits.cpp

@@ -248,3 +248,39 @@ CAmount BitcoinUnits::maxMoney()
 {
     return MAX_MONEY;
 }
+
+namespace {
+qint8 ToQuint8(BitcoinUnit unit)
+{
+    switch (unit) {
+    case BitcoinUnits::BTC: return 0;
+    case BitcoinUnits::mBTC: return 1;
+    case BitcoinUnits::uBTC: return 2;
+    case BitcoinUnits::SAT: return 3;
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
+}
+
+BitcoinUnit FromQuint8(qint8 num)
+{
+    switch (num) {
+    case 3: return BitcoinUnits::SAT;
+    case 2: return BitcoinUnits::uBTC;
+    case 1: return BitcoinUnits::mBTC;
+    default: return BitcoinUnits::BTC;
+    }
+}
+} // namespace
+
+QDataStream& operator<<(QDataStream& out, const BitcoinUnit& unit)
+{
+    return out << ToQuint8(unit);
+}
+
+QDataStream& operator>>(QDataStream& in, BitcoinUnit& unit)
+{
+    quint8 input;
+    in >> input;
+    unit = FromQuint8(input);
+    return in;
+}

src/qt/bitcoinunits.h

@@ -8,6 +8,7 @@
 #include <amount.h>
 
 #include <QAbstractListModel>
+#include <QDataStream>
 #include <QString>
 
 // U+2009 THIN SPACE = UTF-8 E2 80 89
@@ -45,6 +46,7 @@ class BitcoinUnits: public QAbstractListModel
         uBTC,
         SAT
     };
+    Q_ENUM(Unit)
 
     enum class SeparatorStyle
     {
@@ -111,4 +113,7 @@ class BitcoinUnits: public QAbstractListModel
 };
 typedef BitcoinUnits::Unit BitcoinUnit;
 
+QDataStream& operator<<(QDataStream& out, const BitcoinUnit& unit);
+QDataStream& operator>>(QDataStream& in, BitcoinUnit& unit);
+
 #endif // BITCOIN_QT_BITCOINUNITS_H

src/qt/optionsmodel.cpp

@@ -23,6 +23,7 @@
 #include <QDebug>
 #include <QSettings>
 #include <QStringList>
+#include <QVariant>
 
 const char *DEFAULT_GUI_PROXY_HOST = "127.0.0.1";
 
@@ -70,9 +71,15 @@ 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("display_unit")) {
+        settings.setValue("display_unit", QVariant::fromValue(BitcoinUnit::BTC));
+    }
+    QVariant unit = settings.value("display_unit");
+    if (unit.isValid()) {
+        m_display_unit = unit.value<BitcoinUnit>();
+    } else {
+        m_display_unit = BitcoinUnit::BTC;
+    }
 
     if (!settings.contains("strThirdPartyTxUrls"))
         settings.setValue("strThirdPartyTxUrls", "");
@@ -321,7 +328,7 @@ QVariant OptionsModel::data(const QModelIndex & index, int role) const
             return settings.value("bSpendZeroConfChange");
 #endif
         case DisplayUnit:
-            return nDisplayUnit;
+            return QVariant::fromValue(m_display_unit);
         case ThirdPartyTxUrls:
             return strThirdPartyTxUrls;
         case Language:
@@ -501,12 +508,11 @@ bool OptionsModel::setData(const QModelIndex & index, const QVariant & value, in
 /** Updates current unit in memory, settings and emits displayUnitChanged(newUnit) signal */
 void OptionsModel::setDisplayUnit(const QVariant &value)
 {
-    if (!value.isNull())
-    {
+    if (!value.isNull()) {
         QSettings settings;
-        nDisplayUnit = value.toInt();
-        settings.setValue("nDisplayUnit", nDisplayUnit);
-        Q_EMIT displayUnitChanged(nDisplayUnit);
+        m_display_unit = value.value<BitcoinUnit>();
+        settings.setValue("display_unit", QVariant::fromValue(m_display_unit));
+        Q_EMIT displayUnitChanged(static_cast<int>(m_display_unit));
     }
 }
 

src/qt/optionsmodel.h

@@ -6,12 +6,13 @@
 #define BITCOIN_QT_OPTIONSMODEL_H
 
 #include <amount.h>
-#include <cstdint>
+#include <qt/bitcoinunits.h>
 #include <qt/guiconstants.h>
 
 #include <QAbstractListModel>
 
 #include <assert.h>
+#include <cstdint>
 
 namespace interfaces {
 class Node;
@@ -82,7 +83,7 @@ class OptionsModel : public QAbstractListModel
     bool getShowTrayIcon() const { return m_show_tray_icon; }
     bool getMinimizeToTray() const { return fMinimizeToTray; }
     bool getMinimizeOnClose() const { return fMinimizeOnClose; }
-    int getDisplayUnit() const { return nDisplayUnit; }
+    int getDisplayUnit() const { return static_cast<int>(m_display_unit); }
     QString getThirdPartyTxUrls() const { return strThirdPartyTxUrls; }
     bool getCoinControlFeatures() const { return fCoinControlFeatures; }
     const QString& getOverriddenByCommandLine() { return strOverriddenByCommandLine; }
@@ -105,7 +106,7 @@ class OptionsModel : public QAbstractListModel
     bool fMinimizeToTray;
     bool fMinimizeOnClose;
     QString language;
-    int nDisplayUnit;
+    BitcoinUnit m_display_unit;
     QString strThirdPartyTxUrls;
     bool fCoinControlFeatures;
     /* settings that were overridden by command-line */