Implement enum support in CachedSettingValue

Enums are stored as strings, that improves configuration file
readability and maintainability. String values are obtained via
QMetaEnum, and since with Qt 5.5 QMetaEnum::fromType() includes a
static_assert, this has to be a safe method.

src/base/settingvalue.h

@@ -30,7 +30,10 @@
 #define SETTINGVALUE_H
 
 #include <functional>
+#include <type_traits>
+#include <QMetaEnum>
 #include <QString>
+#include <QVariant>
 
 #include "settingsstorage.h"
 
@@ -42,16 +45,14 @@ class CachedSettingValue
 public:
     explicit CachedSettingValue(const char *keyName, const T &defaultValue = T())
         : m_keyName(QLatin1String(keyName))
-        , m_value(SettingsStorage::instance()->loadValue(
-                                m_keyName, defaultValue).template value<T>())
+        , m_value(loadValue(defaultValue))
     {
     }
 
     explicit CachedSettingValue(const char *keyName, const T &defaultValue
             , const ProxyFunc &proxyFunc)
         : m_keyName(QLatin1String(keyName))
-        , m_value(proxyFunc(SettingsStorage::instance()->loadValue(
-                                m_keyName, defaultValue).template value<T>()))
+        , m_value(proxyFunc(loadValue(defaultValue)))
     {
     }
 
@@ -68,11 +69,45 @@ public:
     CachedSettingValue<T> &operator=(const T &newValue)
     {
         m_value = newValue;
-        SettingsStorage::instance()->storeValue(m_keyName, m_value);
+        storeValue(m_value);
         return *this;
     }
 
 private:
+    // regular load/save pair
+    template <typename U, typename std::enable_if<!std::is_enum<U>::value, int>::type = 0>
+    U loadValue(const U &defaultValue)
+    {
+        return SettingsStorage::instance()->loadValue(m_keyName, defaultValue).template value<T>();
+    }
+
+    template <typename U, typename std::enable_if<!std::is_enum<U>::value, int>::type = 0>
+    void storeValue(const U &value)
+    {
+        SettingsStorage::instance()->storeValue(m_keyName, value);
+    }
+
+    // load/save pair for enum
+    // saves literal value of the enum constant, obtained from QMetaEnum
+    template <typename U, typename std::enable_if<std::is_enum<U>::value, int>::type = 0>
+    U loadValue(const U &defaultValue)
+    {
+        static_assert(std::is_same<int, typename std::underlying_type<U>::type>::value,
+                      "Enumeration underlying type has to be int");
+
+        bool ok = false;
+        const U res = static_cast<U>(QMetaEnum::fromType<U>().keyToValue(
+            SettingsStorage::instance()->loadValue(m_keyName, QString()).toString().toLatin1().constData(), &ok));
+        return ok ? res : defaultValue;
+    }
+
+    template <typename U, typename std::enable_if<std::is_enum<U>::value, int>::type = 0>
+    void storeValue(const U &value)
+    {
+        SettingsStorage::instance()->storeValue(m_keyName,
+            QString::fromLatin1(QMetaEnum::fromType<U>().valueToKey(static_cast<int>(value))));
+    }
+
     const QString m_keyName;
     T m_value;
 };

src/base/torrentfileguard.cpp

@@ -28,15 +28,9 @@
 
 #include "torrentfileguard.h"
 
-#include <QMetaEnum>
-#include "settingsstorage.h"
+#include "settingvalue.h"
 #include "utils/fs.h"
 
-namespace
-{
-    const QLatin1String KEY_AUTO_DELETE_ENABLED ("Core/AutoDeleteAddedTorrentFile");
-}
-
 FileGuard::FileGuard(const QString &path)
     : m_path {path}
     , m_remove {true}
@@ -79,18 +73,17 @@ void TorrentFileGuard::markAsAddedToSession()
 
 TorrentFileGuard::AutoDeleteMode TorrentFileGuard::autoDeleteMode()
 {
-    QMetaEnum meta {modeMetaEnum()};
-    return static_cast<AutoDeleteMode>(meta.keyToValue(SettingsStorage::instance()->loadValue(
-                                                           KEY_AUTO_DELETE_ENABLED, meta.valueToKey(Never)).toByteArray()));
+    return autoDeleteModeSetting();
 }
 
 void TorrentFileGuard::setAutoDeleteMode(TorrentFileGuard::AutoDeleteMode mode)
 {
-    QMetaEnum meta {modeMetaEnum()};
-    SettingsStorage::instance()->storeValue(KEY_AUTO_DELETE_ENABLED, meta.valueToKey(mode));
+    autoDeleteModeSetting() = mode;
 }
 
-QMetaEnum TorrentFileGuard::modeMetaEnum()
+CachedSettingValue<TorrentFileGuard::AutoDeleteMode> &TorrentFileGuard::autoDeleteModeSetting()
 {
-    return QMetaEnum::fromType<AutoDeleteMode>();
+    static CachedSettingValue<AutoDeleteMode> setting("Core/AutoDeleteAddedTorrentFile", AutoDeleteMode::Never);
+    return setting;
 }
+

src/base/torrentfileguard.h

@@ -29,10 +29,11 @@
 #ifndef TOFFENTFILEGURAD_H
 #define TOFFENTFILEGURAD_H
 
+#include <QObject>
 #include <QString>
-#include <QMetaType>
 
-class QMetaEnum;
+template <typename T> class CachedSettingValue;
+
 /// Utility class to defer file deletion
 class FileGuard
 {
@@ -62,7 +63,7 @@ public:
     void markAsAddedToSession();
     using FileGuard::setAutoRemove;
 
-    enum AutoDeleteMode     // do not change these names: they are stored in config file
+    enum AutoDeleteMode: int     // do not change these names: they are stored in config file
     {
         Never,
         IfAdded,
@@ -74,9 +75,8 @@ public:
     static void setAutoDeleteMode(AutoDeleteMode mode);
 
 private:
-    static QMetaEnum modeMetaEnum();
-
     TorrentFileGuard(const QString &path, AutoDeleteMode mode);
+    static CachedSettingValue<AutoDeleteMode> &autoDeleteModeSetting();
 
     Q_ENUM(AutoDeleteMode)
     AutoDeleteMode m_mode;

src/gui/search/searchtab.cpp

@@ -31,7 +31,6 @@
 #include <QApplication>
 #include <QDir>
 #include <QMenu>
-#include <QMetaEnum>
 #include <QTreeView>
 #include <QStandardItemModel>
 #include <QHeaderView>
@@ -43,7 +42,7 @@
 
 #include "base/utils/misc.h"
 #include "base/preferences.h"
-#include "base/settingsstorage.h"
+#include "base/settingvalue.h"
 #include "guiiconprovider.h"
 #include "searchsortmodel.h"
 #include "searchlistdelegate.h"
@@ -51,13 +50,6 @@
 #include "searchtab.h"
 #include "ui_searchtab.h"
 
-namespace
-{
-#define SETTINGS_KEY(name) "Search/" name
-
-    const QString KEY_FILTER_MODE_SETTING_NAME = SETTINGS_KEY("FilteringMode");
-}
-
 SearchTab::SearchTab(SearchWidget *parent)
     : QWidget(parent)
     , m_ui(new Ui::SearchTab())
@@ -216,15 +208,14 @@ void SearchTab::updateFilter()
 {
     using Utils::Misc::SizeUnit;
     SearchSortModel* filterModel = getCurrentSearchListProxy();
-    filterModel->enableNameFilter(filteringMode() == OnlyNames);
+    filterModel->enableNameFilter(filteringMode() == NameFilteringMode::OnlyNames);
     // we update size and seeds filter parameters in the model even if they are disabled
     filterModel->setSeedsFilter(m_ui->minSeeds->value(), m_ui->maxSeeds->value());
     filterModel->setSizeFilter(
         sizeInBytes(m_ui->minSize->value(), static_cast<SizeUnit>(m_ui->minSizeUnit->currentIndex())),
         sizeInBytes(m_ui->maxSize->value(), static_cast<SizeUnit>(m_ui->maxSizeUnit->currentIndex())));
 
-    SettingsStorage::instance()->storeValue(KEY_FILTER_MODE_SETTING_NAME,
-                                            m_ui->filterMode->itemData(m_ui->filterMode->currentIndex()));
+    nameFilteringModeSetting() = filteringMode();
 
     filterModel->invalidate();
     updateResultsCount();
@@ -255,14 +246,10 @@ void SearchTab::fillFilterComboBoxes()
 
     m_ui->filterMode->clear();
 
-    QMetaEnum nameFilteringModeEnum =
-        this->metaObject()->enumerator(this->metaObject()->indexOfEnumerator("NameFilteringMode"));
+    m_ui->filterMode->addItem(tr("Torrent names only"), static_cast<int>(NameFilteringMode::OnlyNames));
+    m_ui->filterMode->addItem(tr("Everywhere"), static_cast<int>(NameFilteringMode::Everywhere));
 
-    m_ui->filterMode->addItem(tr("Torrent names only"), nameFilteringModeEnum.valueToKey(OnlyNames));
-    m_ui->filterMode->addItem(tr("Everywhere"), nameFilteringModeEnum.valueToKey(Everywhere));
-
-    QVariant selectedMode = SettingsStorage::instance()->loadValue(
-                KEY_FILTER_MODE_SETTING_NAME, nameFilteringModeEnum.valueToKey(OnlyNames));
+    QVariant selectedMode = static_cast<int>(nameFilteringModeSetting().value());
     int index = m_ui->filterMode->findData(selectedMode);
     m_ui->filterMode->setCurrentIndex(index == -1 ? 0 : index);
 }
@@ -305,9 +292,7 @@ QString SearchTab::statusIconName(SearchTab::Status st)
 
 SearchTab::NameFilteringMode SearchTab::filteringMode() const
 {
-    QMetaEnum metaEnum =
-        this->metaObject()->enumerator(this->metaObject()->indexOfEnumerator("NameFilteringMode"));
-    return static_cast<NameFilteringMode>(metaEnum.keyToValue(m_ui->filterMode->itemData(m_ui->filterMode->currentIndex()).toByteArray()));
+    return static_cast<NameFilteringMode>(m_ui->filterMode->itemData(m_ui->filterMode->currentIndex()).toInt());
 }
 
 void SearchTab::loadSettings()
@@ -355,3 +340,9 @@ void SearchTab::displayToggleColumnsMenu(const QPoint&)
         saveSettings();
     }
 }
+
+CachedSettingValue<SearchTab::NameFilteringMode> &SearchTab::nameFilteringModeSetting()
+{
+    static CachedSettingValue<NameFilteringMode> setting("Search/FilteringMode", NameFilteringMode::OnlyNames);
+    return setting;
+}

src/gui/search/searchtab.h

@@ -31,7 +31,6 @@
 #ifndef SEARCHTAB_H
 #define SEARCHTAB_H
 
-#include <QVariant> // I don't know why <QMetaType> is not enought for Qt's 4.8.7 moc
 #include <QWidget>
 
 #define ENGINE_URL_COLUMN 4
@@ -44,6 +43,8 @@ class QHeaderView;
 class QStandardItemModel;
 class QVBoxLayout;
 
+template <typename T> class CachedSettingValue;
+
 class SearchSortModel;
 class SearchListDelegate;
 class SearchWidget;
@@ -59,13 +60,13 @@ class SearchTab: public QWidget
 
 public:
 
-    enum NameFilteringMode
+    enum class NameFilteringMode
     {
         Everywhere,
         OnlyNames
     };
 
-    Q_ENUMS(NameFilteringMode)
+    Q_ENUM(NameFilteringMode)
 
     explicit SearchTab(SearchWidget *parent);
     ~SearchTab();
@@ -106,6 +107,8 @@ private:
     static QString statusText(Status st);
     static QString statusIconName(Status st);
 
+    static CachedSettingValue<NameFilteringMode>& nameFilteringModeSetting();
+
     Ui::SearchTab *m_ui;
     QTreeView *m_resultsBrowser;
     QStandardItemModel *m_searchListModel;