Show error when settings cannot be restored or saved

* State the error type and location of the relevant file
* Help debugging problems related to settings

plasmoid/lib/syncthingapplet.cpp

@@ -40,6 +40,7 @@
 #include <QDesktopServices>
 #include <QGuiApplication>
 #include <QMap>
+#include <QMessageBox>
 #include <QNetworkReply>
 #include <QPalette>
 #include <QQmlEngine>
@@ -111,6 +112,19 @@ SyncthingApplet::~SyncthingApplet()
 #endif
 }
 
+void showErrorIfSet(const QString &errorMessage)
+{
+    if (errorMessage.isEmpty()) {
+        return;
+    }
+    auto msgBox = new QMessageBox();
+    msgBox->setWindowTitle(QStringLiteral(APP_NAME));
+    msgBox->setAttribute(Qt::WA_DeleteOnClose, true);
+    msgBox->setText(errorMessage);
+    msgBox->setIcon(QMessageBox::Critical);
+    msgBox->show();
+}
+
 void SyncthingApplet::init()
 {
     LOAD_QT_TRANSLATIONS;
@@ -170,9 +184,12 @@ void SyncthingApplet::init()
     if (settings.firstLaunch || settings.fakeFirstLaunch) {
         showWizard();
         settings.firstLaunch = false;
-        Settings::save();
+        saveSettings();
     }
 
+    // show error when settings cannot be restored
+    showErrorIfSet(settings.error);
+
     m_initialized = true;
 }
 
@@ -319,6 +336,12 @@ void SyncthingApplet::updateStatusIconAndTooltip()
     emit connectionStatusChanged();
 }
 
+void SyncthingApplet::saveSettings()
+{
+    Settings::save();
+    showErrorIfSet(Settings::values().error);
+}
+
 QIcon SyncthingApplet::loadForkAwesomeIcon(const QString &name, int size) const
 {
     const auto icon = QtForkAwesome::iconFromId(name);
@@ -348,7 +371,7 @@ void SyncthingApplet::showSettingsDlg()
         // save plasmoid specific settings to disk when applied
         connect(m_settingsDlg, &SettingsDialog::applied, this, &SyncthingApplet::configChanged);
         // save global/general settings to disk when applied
-        connect(m_settingsDlg, &SettingsDialog::applied, &Settings::save);
+        connect(m_settingsDlg, &SettingsDialog::applied, this, &SyncthingApplet::saveSettings);
     }
     centerWidget(m_settingsDlg);
     m_settingsDlg->show();

plasmoid/lib/syncthingapplet.h

@@ -139,6 +139,7 @@ public Q_SLOTS:
     void showDirectoryErrors(unsigned int directoryIndex);
     void copyToClipboard(const QString &text);
     void updateStatusIconAndTooltip();
+    void saveSettings();
     QIcon loadForkAwesomeIcon(const QString &name, int size = 32) const;
     QString formatFileSize(quint64 fileSizeInByte) const;
     QString substituteTilde(const QString &path) const;

tray/application/main.cpp

@@ -144,6 +144,9 @@ static void trigger(bool tray, bool webUi, bool wizard)
 void shutdownSyncthingTray()
 {
     Settings::save();
+    if (const auto &error = Settings::values().error; !error.isEmpty()) {
+        QMessageBox::critical(nullptr, QCoreApplication::applicationName(), error);
+    }
     Settings::Launcher::terminate();
 }
 
@@ -226,6 +229,9 @@ int runApplication(int argc, const char *const *argv)
             settings.enableWipFeatures = true;
         }
         LOAD_QT_TRANSLATIONS;
+        if (!settings.error.isEmpty()) {
+            QMessageBox::critical(nullptr, QCoreApplication::applicationName(), settings.error);
+        }
         SyncthingLauncher launcher;
         SyncthingLauncher::setMainInstance(&launcher);
 #ifdef LIB_SYNCTHING_CONNECTOR_SUPPORT_SYSTEMD

tray/gui/traywidget.cpp

@@ -253,7 +253,7 @@ SettingsDialog *TrayWidget::settingsDialog()
         // note: QCoreApplication::aboutToQuit() does not work reliably but terminating only at the
         //       end of the session is a common use-case for the tray application. So workaround this
         //       by simply saving the settings immediately.
-        connect(s_settingsDlg, &SettingsDialog::applied, &Settings::save);
+        connect(s_settingsDlg, &SettingsDialog::applied, this, &TrayWidget::saveSettings);
     }
     return s_settingsDlg;
 }
@@ -323,6 +323,14 @@ void TrayWidget::applySettingsChangesFromWizard()
     }
 }
 
+void TrayWidget::saveSettings()
+{
+    Settings::save();
+    if (const auto &error = Settings::values().error; !error.isEmpty()) {
+        QMessageBox::critical(nullptr, QCoreApplication::applicationName(), error);
+    }
+}
+
 void TrayWidget::showAboutDialog()
 {
     if (!s_aboutDlg) {

tray/gui/traywidget.h

@@ -78,6 +78,7 @@ public Q_SLOTS:
     void quitTray();
     void applySettings(const QString &connectionConfig = QString());
     void applySettingsChangesFromWizard();
+    void saveSettings();
 
 protected:
     bool event(QEvent *event) override;

widgets/CMakeLists.txt

@@ -89,7 +89,7 @@ find_package(${PACKAGE_NAMESPACE_PREFIX}c++utilities${CONFIGURATION_PACKAGE_SUFF
 use_cpp_utilities(VISIBILITY PUBLIC)
 
 # find qtutilities
-find_package(${PACKAGE_NAMESPACE_PREFIX}qtutilities${CONFIGURATION_PACKAGE_SUFFIX_QTUTILITIES} 6.10.0 REQUIRED)
+find_package(${PACKAGE_NAMESPACE_PREFIX}qtutilities${CONFIGURATION_PACKAGE_SUFFIX_QTUTILITIES} 6.11.0 REQUIRED)
 use_qt_utilities()
 
 # find backend libraries

widgets/settings/settings.cpp

@@ -265,11 +265,12 @@ static void setVarFromEnv(bool &var, const char *envVar)
     }
 }
 
-void restore()
+bool restore()
 {
     auto s = QtUtilities::getSettings(QStringLiteral(PROJECT_NAME));
     auto &v = values();
     auto &settings = *s;
+    v.error = QtUtilities::errorMessageForSettings(settings);
 
     const auto version = QVersionNumber::fromString(settings.value(QStringLiteral("v")).toString());
     settings.beginGroup(QStringLiteral("tray"));
@@ -417,13 +418,15 @@ void restore()
     // restore developer settings from environment variables
     setVarFromEnv(v.fakeFirstLaunch, PROJECT_VARNAME_UPPER "_FAKE_FIRST_LAUNCH");
     setVarFromEnv(v.enableWipFeatures, PROJECT_VARNAME_UPPER "_ENABLE_WIP_FEATURES");
+
+    return v.error.isEmpty();
 }
 
-void save()
+bool save()
 {
     auto s = QtUtilities::getSettings(QStringLiteral(PROJECT_NAME));
     auto &settings = *s;
-    const auto &v = values();
+    auto &v = values();
 
     settings.setValue(QStringLiteral("v"), QStringLiteral(APP_VERSION));
     settings.beginGroup(QStringLiteral("tray"));
@@ -530,6 +533,10 @@ void save()
 #endif
 
     v.qt.save(settings);
+
+    settings.sync();
+    v.error = QtUtilities::errorMessageForSettings(settings);
+    return v.error.isEmpty();
 }
 
 /*!

widgets/settings/settings.h

@@ -155,6 +155,7 @@ struct SYNCTHINGWIDGETS_EXPORT Settings {
     bool fakeFirstLaunch = false; // not persistent, for testing purposes only
     bool enableWipFeatures = false; // not persistent, for testing purposes only
     bool isPlasmoid = false; // not persistent, set by the Plasmoid
+    QString error; // not persistent, whether an error occured on last restore()/save()
     Connection connection;
     NotifyOn notifyOn;
 #ifdef QT_UTILITIES_SUPPORT_DBUS_NOTIFICATIONS
@@ -181,8 +182,8 @@ struct SYNCTHINGWIDGETS_EXPORT Settings {
 };
 
 SYNCTHINGWIDGETS_EXPORT Settings &values();
-SYNCTHINGWIDGETS_EXPORT void restore();
-SYNCTHINGWIDGETS_EXPORT void save();
+SYNCTHINGWIDGETS_EXPORT bool restore();
+SYNCTHINGWIDGETS_EXPORT bool save();
 } // namespace Settings
 
 #endif // SETTINGS_H