diff --git a/src/kleo/enum.cpp b/src/kleo/enum.cpp
index 15ea1fd..829d4fd 100644
--- a/src/kleo/enum.cpp
+++ b/src/kleo/enum.cpp
@@ -1,335 +1,338 @@
 /*
     kleo/enum.cpp
 
     This file is part of libkleopatra, the KDE keymanagement library
     Copyright (c) 2004 Klarälvdalens Datakonsult AB
 
     Libkleopatra is free software; you can redistribute it and/or
     modify it under the terms of the GNU General Public License as
     published by the Free Software Foundation; either version 2 of the
     License, or (at your option) any later version.
 
     Libkleopatra is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.
 
     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 
     In addition, as a special exception, the copyright holders give
     permission to link the code of this program with any edition of
     the Qt library by Trolltech AS, Norway (or with modified versions
     of Qt that use the same license as Qt), and distribute linked
     combinations including the two.  You must obey the GNU General
     Public License in all respects for all of the code used other than
     Qt.  If you modify this file, you may extend this exception to
     your version of the file, but you are not obligated to do so.  If
     you do not wish to do so, delete this exception statement from
     your version.
 */
 
 #include "enum.h"
 #include "libkleo_debug.h"
 #include "models/keycache.h"
+
+#include <functional>
+
 #include <KLocalizedString>
 
 #include <gpgme++/key.h>
 #include <gpgme++/tofuinfo.h>
 
 #include <QString>
 #include <QStringList>
 #include <QEventLoop>
 
 static const struct {
     Kleo::CryptoMessageFormat format;
     const char *displayName;
     const char *configName;
 } cryptoMessageFormats[] = {
     {
         Kleo::InlineOpenPGPFormat,
         I18N_NOOP("Inline OpenPGP (deprecated)"),
         "inline openpgp"
     },
     {
         Kleo::OpenPGPMIMEFormat,
         I18N_NOOP("OpenPGP/MIME"),
         "openpgp/mime"
     },
     {
         Kleo::SMIMEFormat,
         I18N_NOOP("S/MIME"),
         "s/mime"
     },
     {
         Kleo::SMIMEOpaqueFormat,
         I18N_NOOP("S/MIME Opaque"),
         "s/mime opaque"
     },
 };
 static const unsigned int numCryptoMessageFormats
     = sizeof cryptoMessageFormats / sizeof * cryptoMessageFormats;
 
 const char *Kleo::cryptoMessageFormatToString(Kleo::CryptoMessageFormat f)
 {
     if (f == AutoFormat) {
         return "auto";
     }
     for (unsigned int i = 0; i < numCryptoMessageFormats; ++i)
         if (f == cryptoMessageFormats[i].format) {
             return cryptoMessageFormats[i].configName;
         }
     return nullptr;
 }
 
 QStringList Kleo::cryptoMessageFormatsToStringList(unsigned int f)
 {
     QStringList result;
     for (unsigned int i = 0; i < numCryptoMessageFormats; ++i)
         if (f & cryptoMessageFormats[i].format) {
             result.push_back(QLatin1String(cryptoMessageFormats[i].configName));
         }
     return result;
 }
 
 QString Kleo::cryptoMessageFormatToLabel(Kleo::CryptoMessageFormat f)
 {
     if (f == AutoFormat) {
         return i18n("Any");
     }
     for (unsigned int i = 0; i < numCryptoMessageFormats; ++i)
         if (f == cryptoMessageFormats[i].format) {
             return i18n(cryptoMessageFormats[i].displayName);
         }
     return QString();
 }
 
 Kleo::CryptoMessageFormat Kleo::stringToCryptoMessageFormat(const QString &s)
 {
     const QString t = s.toLower();
     for (unsigned int i = 0; i < numCryptoMessageFormats; ++i)
         if (t == QLatin1String(cryptoMessageFormats[i].configName)) {
             return cryptoMessageFormats[i].format;
         }
     return AutoFormat;
 }
 
 unsigned int Kleo::stringListToCryptoMessageFormats(const QStringList &sl)
 {
     unsigned int result = 0;
     for (QStringList::const_iterator it = sl.begin(); it != sl.end(); ++it) {
         result |= stringToCryptoMessageFormat(*it);
     }
     return result;
 }
 
 // For the config values used below, see also kaddressbook/editors/cryptowidget.cpp
 
 const char *Kleo::encryptionPreferenceToString(EncryptionPreference pref)
 {
     switch (pref) {
     case UnknownPreference:
         return nullptr;
     case NeverEncrypt:
         return "never";
     case AlwaysEncrypt:
         return "always";
     case AlwaysEncryptIfPossible:
         return "alwaysIfPossible";
     case AlwaysAskForEncryption:
         return "askAlways";
     case AskWheneverPossible:
         return "askWhenPossible";
     }
     return nullptr; // keep the compiler happy
 }
 
 Kleo::EncryptionPreference Kleo::stringToEncryptionPreference(const QString &str)
 {
     if (str == QLatin1String("never")) {
         return NeverEncrypt;
     }
     if (str == QLatin1String("always")) {
         return AlwaysEncrypt;
     }
     if (str == QLatin1String("alwaysIfPossible")) {
         return AlwaysEncryptIfPossible;
     }
     if (str == QLatin1String("askAlways")) {
         return AlwaysAskForEncryption;
     }
     if (str == QLatin1String("askWhenPossible")) {
         return AskWheneverPossible;
     }
     return UnknownPreference;
 }
 
 QString Kleo::encryptionPreferenceToLabel(EncryptionPreference pref)
 {
     switch (pref) {
     case NeverEncrypt:
         return i18n("Never Encrypt");
     case AlwaysEncrypt:
         return i18n("Always Encrypt");
     case AlwaysEncryptIfPossible:
         return i18n("Always Encrypt If Possible");
     case AlwaysAskForEncryption:
         return i18n("Ask");
     case AskWheneverPossible:
         return i18n("Ask Whenever Possible");
     default:
         return xi18nc("no specific preference", "<placeholder>none</placeholder>");
     }
 }
 
 const char *Kleo::signingPreferenceToString(SigningPreference pref)
 {
     switch (pref) {
     case UnknownSigningPreference:
         return nullptr;
     case NeverSign:
         return "never";
     case AlwaysSign:
         return "always";
     case AlwaysSignIfPossible:
         return "alwaysIfPossible";
     case AlwaysAskForSigning:
         return "askAlways";
     case AskSigningWheneverPossible:
         return "askWhenPossible";
     }
     return nullptr; // keep the compiler happy
 }
 
 Kleo::SigningPreference Kleo::stringToSigningPreference(const QString &str)
 {
     if (str == QLatin1String("never")) {
         return NeverSign;
     }
     if (str == QLatin1String("always")) {
         return AlwaysSign;
     }
     if (str == QLatin1String("alwaysIfPossible")) {
         return AlwaysSignIfPossible;
     }
     if (str == QLatin1String("askAlways")) {
         return AlwaysAskForSigning;
     }
     if (str == QLatin1String("askWhenPossible")) {
         return AskSigningWheneverPossible;
     }
     return UnknownSigningPreference;
 }
 
 QString Kleo::signingPreferenceToLabel(SigningPreference pref)
 {
     switch (pref) {
     case NeverSign:
         return i18n("Never Sign");
     case AlwaysSign:
         return i18n("Always Sign");
     case AlwaysSignIfPossible:
         return i18n("Always Sign If Possible");
     case AlwaysAskForSigning:
         return i18n("Ask");
     case AskSigningWheneverPossible:
         return i18n("Ask Whenever Possible");
     default:
         return i18nc("no specific preference", "<none>");
     }
 }
 
 Kleo::TrustLevel Kleo::trustLevel(const GpgME::Key &key)
 {
     TrustLevel maxTl = Level0;
     for (int i = 0, c = key.numUserIDs(); i < c; ++i) {
         const auto tl = trustLevel(key.userID(i));
         maxTl = qMax(maxTl, tl);
         if (maxTl == Level4) {
             break;
         }
     }
 
     return maxTl;
 }
 
 namespace {
 
 bool hasTrustedSignature(const GpgME::UserID &uid)
 {
     // lazily intialized cache
     static std::shared_ptr<const Kleo::KeyCache> keyCache;
     if (!keyCache) {
         keyCache = Kleo::KeyCache::instance();
     }
     if (!keyCache->initialized()) {
         QEventLoop el;
         QObject::connect(keyCache.get(), &Kleo::KeyCache::keyListingDone,
                          &el, &QEventLoop::quit);
         el.exec();
     }
 
     const auto signatures = uid.signatures();
     std::vector<std::string> sigKeyIDs;
     std::transform(signatures.cbegin(), signatures.cend(),
                    std::back_inserter(sigKeyIDs),
                    std::bind(&GpgME::UserID::Signature::signerKeyID, std::placeholders::_1));
 
     const auto keys = keyCache->findByKeyIDOrFingerprint(sigKeyIDs);
     return std::any_of(keys.cbegin(), keys.cend(),
                        [](const GpgME::Key &key) {
                            return key.ownerTrust() == GpgME::Key::Ultimate;
                        });
 }
 
 }
 
 Kleo::TrustLevel Kleo::trustLevel(const GpgME::UserID &uid)
 {
     // Modelled after https://wiki.gnupg.org/EasyGpg2016/AutomatedEncryption,
     // but modified to cover all cases, unlike the pseudocode in the document.
     //
     // TODO: Check whether the key comes from a trusted source (Cert/PKA/DANE/WKD)
 
     switch (uid.validity()) {
     case GpgME::UserID::Unknown:
     case GpgME::UserID::Undefined:
     case GpgME::UserID::Never:
         // Not enough trust -> level 0
         return Level0;
 
     case GpgME::UserID::Marginal:
         // Marginal trust without TOFU data means the key is still trusted
         // through the Web of Trust -> level 2
         if (uid.tofuInfo().isNull()) {
             return Level2;
         }
         // Marginal trust with TOFU, level will depend on TOFU history
         switch (uid.tofuInfo().validity()) {
         case GpgME::TofuInfo::ValidityUnknown:
         case GpgME::TofuInfo::Conflict:
         case GpgME::TofuInfo::NoHistory:
             // Marginal trust, but not enough history -> level 0
             return Level0;
         case GpgME::TofuInfo::LittleHistory:
             // Marginal trust, but too little history -> level 1
             return Level1;
         case GpgME::TofuInfo::BasicHistory:
         case GpgME::TofuInfo::LargeHistory:
             // Marginal trust and enough history -> level 2
             return Level2;
         }
 
     case GpgME::UserID::Full:
         // Full trust, trust level depends whether the UserID is signed with
         // at least one key with Ultimate ownertrust.
         return hasTrustedSignature(uid) ? Level4 : Level3;
 
     case GpgME::UserID::Ultimate:
         // Ultimate trust -> leve 4
         return Level4;
     }
 
     Q_UNREACHABLE();
 }