Add OSUtils for platform-specific functionality.

Moves MacUtils into a separate sub folder and adds
WinUtils, NixUtils, and OSUtils for platform-native
code on Windows, Unix-like, and generic/all systems.

src/gui/osutils/macutils/MacUtils.cpp

@@ -0,0 +1,87 @@
+/*
+ *  Copyright (C) 2012 Felix Geyer <debfx@fobos.de>
+ *  Copyright (C) 2018 KeePassXC Team <team@keepassxc.org>
+ *
+ *  This program 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 or (at your option)
+ *  version 3 of the License.
+ *
+ *  This program 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "MacUtils.h"
+#include <QApplication>
+
+QPointer<MacUtils> MacUtils::m_instance = nullptr;
+
+MacUtils::MacUtils(QObject* parent)
+    : OSUtils(parent)
+    , m_appkit(new AppKit())
+{
+    connect(m_appkit.data(), SIGNAL(lockDatabases()), SIGNAL(lockDatabases()));
+}
+
+MacUtils::~MacUtils()
+{
+}
+
+MacUtils* MacUtils::instance()
+{
+    if (!m_instance) {
+        m_instance = new MacUtils(qApp);
+    }
+
+    return m_instance;
+}
+
+WId MacUtils::activeWindow()
+{
+    return m_appkit->activeProcessId();
+}
+
+bool MacUtils::raiseWindow(WId pid)
+{
+    return m_appkit->activateProcess(pid);
+}
+
+bool MacUtils::raiseOwnWindow()
+{
+    return m_appkit->activateProcess(m_appkit->ownProcessId());
+}
+
+bool MacUtils::raiseLastActiveWindow()
+{
+    return m_appkit->activateProcess(m_appkit->lastActiveProcessId());
+}
+
+bool MacUtils::hideOwnWindow()
+{
+    return m_appkit->hideProcess(m_appkit->ownProcessId());
+}
+
+bool MacUtils::isHidden()
+{
+    return m_appkit->isHidden(m_appkit->ownProcessId());
+}
+
+bool MacUtils::isDarkMode()
+{
+    return m_appkit->isDarkMode();
+}
+
+bool MacUtils::enableAccessibility()
+{
+    return m_appkit->enableAccessibility();
+}
+
+bool MacUtils::enableScreenRecording()
+{
+    return m_appkit->enableScreenRecording();
+}