diff --git a/README.md b/README.md
index de5d0181b..57672f3a3 100644
--- a/README.md
+++ b/README.md
@@ -30,9 +30,7 @@ You can download source tarballs or binaries for some platforms in [Downloads](d
 
 * [stable releases](http://software.opensuse.org/download.html?project=home%3Askunkos&package=rssguard),
 * [development releases](http://software.opensuse.org/download.html?project=home%3Askunkos&package=rssguard-git) (compiled from the master branch of RSS Guard Git repository),
-* [Archlinux AUR stable package (compiled with Qt 5)](https://aur.archlinux.org/packages/rssguard/),
-* [Archlinux AUR stable package (compiled with Qt 4)](https://aur.archlinux.org/packages/rssguard-qt4/),
-* [Archlinux AUR development package (compiled with Qt 5)](https://aur.archlinux.org/packages/rssguard-git/).
+* Archlinux AUR package ([stable-qt5](https://aur.archlinux.org/packages/rssguard/), [stable-qt4](https://aur.archlinux.org/packages/rssguard-qt4/), [development-qt5](https://aur.archlinux.org/packages/rssguard-git/)].
 - - -
 Features
 --------
diff --git a/resources/text/CHANGELOG b/resources/text/CHANGELOG
index e73d7a40b..dfc9482cb 100644
--- a/resources/text/CHANGELOG
+++ b/resources/text/CHANGELOG
@@ -8,7 +8,7 @@ Fixed:
 
 Added:
 <ul>
-<li>Application is now able to self-update itself on OS/2 and Windows. Currently, this is EXPERIMENTAL support. Please, report any bugs.</li>
+<li>Application is now able to self-update itself on OS/2 and Windows. Currently, this is EXPERIMENTAL support. Please, report any bugs. Authors take no responsibility for removed files or lost application settings.</li>
 <li>Added option to adjust icons/buttons displayed in toolbars. See Settings/User interface/Toolbars dialog for more information.</li>
 <li>Added option to search messages via regular expression.</li>
 <li>Added option to highlight particular messages - unread, important, none.</li>
diff --git a/src/application.cpp b/src/application.cpp
index b346e3efc..e307a99b6 100644
--- a/src/application.cpp
+++ b/src/application.cpp
@@ -1,8 +1,25 @@
+// This file is part of RSS Guard.
+//
+// Copyright (C) 2011-2014 by Martin Rotter <rotter.martinos@gmail.com>
+//
+// RSS Guard 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 3 of the License, or
+// (at your option) any later version.
+//
+// RSS Guard 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 RSS Guard. If not, see <http://www.gnu.org/licenses/>.
+
 #include "application.h"
 
 
-Application::Application(int &argc, char **argv)
-  : QtSingleApplication(argc, argv) {
+Application::Application(const QString &id, int &argc, char **argv)
+  : QtSingleApplication(id, argc, argv) {
 }
 
 Application::~Application() {
diff --git a/src/application.h b/src/application.h
index 4c9c5ae87..fb9b88182 100644
--- a/src/application.h
+++ b/src/application.h
@@ -1,8 +1,30 @@
+// This file is part of RSS Guard.
+//
+// Copyright (C) 2011-2014 by Martin Rotter <rotter.martinos@gmail.com>
+//
+// RSS Guard 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 3 of the License, or
+// (at your option) any later version.
+//
+// RSS Guard 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 RSS Guard. If not, see <http://www.gnu.org/licenses/>.
+
 #ifndef APPLICATION_H
 #define APPLICATION_H
 
 #include "qtsingleapplication/qtsingleapplication.h"
 
+#if defined(qApp)
+#undef qApp
+#endif
+#define qApp (Application::instance())
+
 
 // TODO: presunout nektery veci sem, settings atp
 class Application : public QtSingleApplication {
@@ -10,7 +32,7 @@ class Application : public QtSingleApplication {
 
   public:
     // Constructors and destructors.
-    explicit Application(int &argc, char **argv);
+    explicit Application(const QString &id, int &argc, char **argv);
     virtual ~Application();
 
     // Returns pointer to "GOD" application singleton.
diff --git a/src/core/feeddownloader.cpp b/src/core/feeddownloader.cpp
index 596be3355..9a3330e04 100644
--- a/src/core/feeddownloader.cpp
+++ b/src/core/feeddownloader.cpp
@@ -21,7 +21,6 @@
 
 #include <QThread>
 #include <QDebug>
-#include <QApplication>
 
 
 FeedDownloader::FeedDownloader(QObject *parent) : QObject(parent) {
diff --git a/src/core/feedsmodelcategory.h b/src/core/feedsmodelcategory.h
index 2b2bc3b3e..0b90c09b9 100755
--- a/src/core/feedsmodelcategory.h
+++ b/src/core/feedsmodelcategory.h
@@ -21,7 +21,7 @@
 #include "core/feedsmodelrootitem.h"
 
 #include <QSqlRecord>
-#include <QApplication>
+#include <QCoreApplication>
 
 
 class FeedsModelFeed;
diff --git a/src/core/feedsmodelfeed.h b/src/core/feedsmodelfeed.h
index 89a336dd0..69fc1960f 100755
--- a/src/core/feedsmodelfeed.h
+++ b/src/core/feedsmodelfeed.h
@@ -25,12 +25,11 @@
 #include <QSqlRecord>
 #include <QPair>
 #include <QNetworkReply>
-#include <QApplication>
+#include <QCoreApplication>
 
 
 class Message;
 
-
 // Represents BASE class for feeds contained in FeedsModel.
 // NOTE: This class should be derived to create PARTICULAR feed types.
 class FeedsModelFeed : public FeedsModelRootItem {
diff --git a/src/core/feedsmodelrootitem.cpp b/src/core/feedsmodelrootitem.cpp
index 8842d37cf..1396561c4 100755
--- a/src/core/feedsmodelrootitem.cpp
+++ b/src/core/feedsmodelrootitem.cpp
@@ -17,7 +17,7 @@
 
 #include "core/feedsmodelrootitem.h"
 
-#include "qtsingleapplication/qtsingleapplication.h"
+#include "application.h"
 
 #include <QVariant>
 
@@ -35,7 +35,7 @@ FeedsModelRootItem::~FeedsModelRootItem() {
 }
 
 void FeedsModelRootItem::setupFonts() {
-  m_normalFont = QtSingleApplication::font("FeedsView");
+  m_normalFont = Application::font("FeedsView");
   m_boldFont = m_normalFont;
   m_boldFont.setBold(true);
 }
diff --git a/src/core/messagesmodel.cpp b/src/core/messagesmodel.cpp
index c90aaa5d9..2618feb4e 100644
--- a/src/core/messagesmodel.cpp
+++ b/src/core/messagesmodel.cpp
@@ -21,7 +21,7 @@
 #include "miscellaneous/textfactory.h"
 #include "miscellaneous/databasefactory.h"
 #include "miscellaneous/iconfactory.h"
-#include "qtsingleapplication/qtsingleapplication.h"
+#include "application.h"
 
 #include <QSqlRecord>
 #include <QSqlError>
@@ -62,7 +62,7 @@ void MessagesModel::fetchAll() {
 }
 
 void MessagesModel::setupFonts() {
-  m_normalFont = QtSingleApplication::font("MessagesView");
+  m_normalFont = Application::font("MessagesView");
   m_boldFont = m_normalFont;
   m_boldFont.setBold(true);
 }
diff --git a/src/gui/feedmessageviewer.cpp b/src/gui/feedmessageviewer.cpp
index 4d40c3cc5..bb8f815ff 100644
--- a/src/gui/feedmessageviewer.cpp
+++ b/src/gui/feedmessageviewer.cpp
@@ -38,7 +38,6 @@
 #include <QSplitter>
 #include <QToolBar>
 #include <QDebug>
-#include <QApplication>
 #include <QLineEdit>
 #include <QAction>
 #include <QToolButton>
diff --git a/src/gui/formmain.cpp b/src/gui/formmain.cpp
index 2c1bac752..6c961587b 100755
--- a/src/gui/formmain.cpp
+++ b/src/gui/formmain.cpp
@@ -33,7 +33,7 @@
 #include "gui/statusbar.h"
 #include "gui/feedmessageviewer.h"
 #include "gui/formupdate.h"
-#include "qtsingleapplication/qtsingleapplication.h"
+#include "application.h"
 
 #include <QCloseEvent>
 #include <QSessionManager>
@@ -219,7 +219,7 @@ void FormMain::display() {
   raise();
 
   // Raise alert event. Check the documentation for more info on this.
-  QtSingleApplication::alert(this);
+  Application::alert(this);
 }
 
 void FormMain::onCommitData(QSessionManager &manager) {
diff --git a/src/gui/formsettings.cpp b/src/gui/formsettings.cpp
index 5f9f2805d..111fc5152 100755
--- a/src/gui/formsettings.cpp
+++ b/src/gui/formsettings.cpp
@@ -38,8 +38,8 @@
 #include "gui/messagebox.h"
 #include "gui/basetoolbar.h"
 #include "gui/messagestoolbar.h"
-#include "qtsingleapplication/qtsingleapplication.h"
 #include "dynamic-shortcuts/dynamicshortcuts.h"
+#include "application.h"
 
 #include <QProcess>
 #include <QNetworkProxy>
diff --git a/src/gui/locationlineedit.cpp b/src/gui/locationlineedit.cpp
index f2aa96e4d..84185eff2 100644
--- a/src/gui/locationlineedit.cpp
+++ b/src/gui/locationlineedit.cpp
@@ -17,13 +17,7 @@
 
 #include "gui/locationlineedit.h"
 
-#include "definitions/definitions.h"
-#include "miscellaneous/settings.h"
-
-#include <QPaintEvent>
-#include <QStyleOptionFrameV2>
-#include <QPainter>
-#include <QApplication>
+#include <QMouseEvent>
 
 
 LocationLineEdit::LocationLineEdit(QWidget *parent)
diff --git a/src/gui/messagebox.cpp b/src/gui/messagebox.cpp
index 440e8355e..5324ded57 100644
--- a/src/gui/messagebox.cpp
+++ b/src/gui/messagebox.cpp
@@ -18,13 +18,14 @@
 #include "gui/messagebox.h"
 
 #include "miscellaneous/iconfactory.h"
+#include "application.h"
 
-#include <QDialogButtonBox>
 #include <QtGlobal>
+#include <QDialogButtonBox>
 #include <QPushButton>
 #include <QDialogButtonBox>
 #include <QStyle>
-#include <QApplication>
+
 
 MessageBox::MessageBox(QWidget *parent) : QMessageBox(parent) {
 }
diff --git a/src/gui/systemtrayicon.cpp b/src/gui/systemtrayicon.cpp
index fde662880..9a626b223 100644
--- a/src/gui/systemtrayicon.cpp
+++ b/src/gui/systemtrayicon.cpp
@@ -21,7 +21,7 @@
 #include "miscellaneous/settings.h"
 #include "gui/formmain.h"
 #include "gui/formsettings.h"
-#include "qtsingleapplication/qtsingleapplication.h"
+#include "application.h"
 
 #include <QPainter>
 #include <QTimer>
@@ -36,7 +36,7 @@ TrayIconMenu::~TrayIconMenu() {
 }
 
 bool TrayIconMenu::event(QEvent *event) {
-  if (QtSingleApplication::activeModalWidget() != NULL &&
+  if (Application::activeModalWidget() != NULL &&
       event->type() == QEvent::Show) {
     QTimer::singleShot(0, this, SLOT(hide()));
     SystemTrayIcon::instance()->showMessage(APP_LONG_NAME,
diff --git a/src/gui/tabwidget.cpp b/src/gui/tabwidget.cpp
index dbebac8ac..8185cc42e 100644
--- a/src/gui/tabwidget.cpp
+++ b/src/gui/tabwidget.cpp
@@ -26,8 +26,8 @@
 #include "gui/formmain.h"
 #include "gui/feedmessageviewer.h"
 #include "gui/plaintoolbutton.h"
+#include "application.h"
 
-#include <QApplication>
 #include <QMenu>
 #include <QToolButton>
 
diff --git a/src/main.cpp b/src/main.cpp
index c277cebae..bc17476f3 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -27,7 +27,7 @@
 #include "gui/systemtrayicon.h"
 #include "gui/feedmessageviewer.h"
 #include "gui/feedsview.h"
-#include "qtsingleapplication/qtsingleapplication.h"
+#include "application.h"
 
 // Needed for setting ini file format on Mac OS.
 #ifdef Q_OS_MAC
@@ -66,8 +66,8 @@ int main(int argc, char *argv[]) {
 #endif
 
   // Instantiate base application object.
-  QtSingleApplication application(APP_LOW_NAME, argc, argv);
-  qDebug("Instantiated QtSingleApplication class.");
+  Application application(APP_LOW_NAME, argc, argv);
+  qDebug("Instantiated Application class.");
 
   // Check if another instance is running.
   if (application.sendMessage(APP_IS_RUNNING)) {
@@ -85,11 +85,11 @@ int main(int argc, char *argv[]) {
   Localization::instance()->load();
 
   // These settings needs to be set before any QSettings object.
-  QtSingleApplication::setApplicationName(APP_NAME);
-  QtSingleApplication::setApplicationVersion(APP_VERSION);
-  QtSingleApplication::setOrganizationName(APP_AUTHOR);
-  QtSingleApplication::setOrganizationDomain(APP_URL);
-  QtSingleApplication::setWindowIcon(QIcon(APP_ICON_PATH));
+  Application::setApplicationName(APP_NAME);
+  Application::setApplicationVersion(APP_VERSION);
+  Application::setOrganizationName(APP_AUTHOR);
+  Application::setOrganizationDomain(APP_URL);
+  Application::setWindowIcon(QIcon(APP_ICON_PATH));
 
   qDebug().nospace() << "Creating main application form in thread: \'" <<
                         QThread::currentThreadId() << "\'.";
@@ -126,5 +126,5 @@ int main(int argc, char *argv[]) {
                    &main_window, SLOT(processExecutionMessage(QString)));
 
   // Enter global event loop.
-  return QtSingleApplication::exec();
+  return Application::exec();
 }
diff --git a/src/miscellaneous/databasefactory.cpp b/src/miscellaneous/databasefactory.cpp
index 11a0be88a..fffc608f7 100644
--- a/src/miscellaneous/databasefactory.cpp
+++ b/src/miscellaneous/databasefactory.cpp
@@ -19,8 +19,8 @@
 
 #include "definitions/definitions.h"
 #include "miscellaneous/settings.h"
+#include "application.h"
 
-#include <QApplication>
 #include <QDir>
 #include <QSqlQuery>
 #include <QSqlError>
diff --git a/src/miscellaneous/debugging.cpp b/src/miscellaneous/debugging.cpp
index bf57b6abe..84112f4d2 100644
--- a/src/miscellaneous/debugging.cpp
+++ b/src/miscellaneous/debugging.cpp
@@ -18,8 +18,8 @@
 #include "miscellaneous/debugging.h"
 
 #include "definitions/definitions.h"
+#include "application.h"
 
-#include <QApplication>
 #include <QDir>
 
 #include <cstdio>
diff --git a/src/miscellaneous/iconfactory.h b/src/miscellaneous/iconfactory.h
index 1fa1c6cc9..c440686a4 100644
--- a/src/miscellaneous/iconfactory.h
+++ b/src/miscellaneous/iconfactory.h
@@ -18,15 +18,17 @@
 #ifndef ICONFACTORY_H
 #define ICONFACTORY_H
 
+#include <QObject>
+
+#include "definitions/definitions.h"
+#include "application.h"
+
 #include <QString>
 #include <QIcon>
 #include <QPointer>
 #include <QHash>
-#include <QApplication>
 #include <QDir>
 
-#include "definitions/definitions.h"
-
 
 class IconFactory : public QObject {
   public:
diff --git a/src/miscellaneous/localization.cpp b/src/miscellaneous/localization.cpp
index 33e73bcc1..291610320 100644
--- a/src/miscellaneous/localization.cpp
+++ b/src/miscellaneous/localization.cpp
@@ -19,10 +19,9 @@
 
 #include "definitions/definitions.h"
 #include "miscellaneous/settings.h"
-#include "qtsingleapplication/qtsingleapplication.h"
+#include "application.h"
 
 #include <QPointer>
-#include <QApplication>
 #include <QTranslator>
 #include <QDir>
 #include <QFileInfoList>
@@ -61,7 +60,7 @@ void Localization::load() {
   if (app_translator->load(QString("rssguard-%1.qm").arg(desired_localization),
                            APP_LANG_PATH,
                            "-")) {
-    QApplication::installTranslator(app_translator);
+    Application::installTranslator(app_translator);
     qDebug("Application localization '%s' loaded successfully.",
            qPrintable(desired_localization));
   }
@@ -74,7 +73,7 @@ void Localization::load() {
   if (qt_translator->load(QString("qt-%1.qm").arg(desired_localization),
                           APP_LANG_PATH,
                           "-")) {
-    QApplication::installTranslator(qt_translator);
+    Application::installTranslator(qt_translator);
     qDebug("Qt localization '%s' loaded successfully.",
            qPrintable(desired_localization));
   }
diff --git a/src/miscellaneous/settings.cpp b/src/miscellaneous/settings.cpp
index 0200511ab..f30a87e43 100644
--- a/src/miscellaneous/settings.cpp
+++ b/src/miscellaneous/settings.cpp
@@ -18,8 +18,8 @@
 #include "miscellaneous/settings.h"
 
 #include "definitions/definitions.h"
+#include "application.h"
 
-#include <QApplication>
 #include <QDebug>
 #include <QDir>
 #include <QPointer>
diff --git a/src/miscellaneous/settings.h b/src/miscellaneous/settings.h
index 0c9df77d5..dc825d874 100644
--- a/src/miscellaneous/settings.h
+++ b/src/miscellaneous/settings.h
@@ -19,6 +19,7 @@
 #define SETTINGS_H
 
 #include <QSettings>
+
 #include <QPointer>
 
 
diff --git a/src/miscellaneous/skinfactory.cpp b/src/miscellaneous/skinfactory.cpp
index ee60e17c9..3958428d8 100644
--- a/src/miscellaneous/skinfactory.cpp
+++ b/src/miscellaneous/skinfactory.cpp
@@ -19,8 +19,8 @@
 
 #include "definitions/definitions.h"
 #include "miscellaneous/settings.h"
+#include "application.h"
 
-#include <QApplication>
 #include <QDir>
 #include <QStyleFactory>
 #include <QDomDocument>
diff --git a/src/miscellaneous/skinfactory.h b/src/miscellaneous/skinfactory.h
index 7c293847b..0d244ece5 100644
--- a/src/miscellaneous/skinfactory.h
+++ b/src/miscellaneous/skinfactory.h
@@ -19,6 +19,7 @@
 #define SKINFACTORY_H
 
 #include <QObject>
+
 #include <QPointer>
 #include <QStringList>
 #include <QMetaType>
diff --git a/src/miscellaneous/systemfactory.cpp b/src/miscellaneous/systemfactory.cpp
index 4e21c5f55..0bb0df299 100644
--- a/src/miscellaneous/systemfactory.cpp
+++ b/src/miscellaneous/systemfactory.cpp
@@ -19,16 +19,14 @@
 
 #include "definitions/definitions.h"
 #include "network-web/networkfactory.h"
+#include "application.h"
 
 #if defined(Q_OS_WIN)
-#include "qtsingleapplication/qtsingleapplication.h"
-
 #include <QSettings>
 #endif
 
 #include <QString>
 #include <QFile>
-#include <QApplication>
 #include <QDomDocument>
 #include <QDomElement>
 #include <QDomAttr>
@@ -55,7 +53,7 @@ SystemFactory::AutoStartStatus SystemFactory::getAutoStartStatus() {
   bool autostart_enabled = registry_key.value(APP_LOW_NAME,
                                               "").toString().replace('\\',
                                                                      '/') ==
-                           QtSingleApplication::applicationFilePath();
+                           Application::applicationFilePath();
 
   if (autostart_enabled) {
     return SystemFactory::Enabled;
@@ -138,8 +136,8 @@ bool SystemFactory::setAutoStartStatus(const AutoStartStatus &new_status) {
   switch (new_status) {
     case SystemFactory::Enabled:
       registry_key.setValue(APP_LOW_NAME,
-                            QtSingleApplication::applicationFilePath().replace('/',
-                                                                               '\\'));
+                            Application::applicationFilePath().replace('/',
+                                                                       '\\'));
       return true;
     case SystemFactory::Disabled:
       registry_key.remove(APP_LOW_NAME);
diff --git a/src/miscellaneous/systemfactory.h b/src/miscellaneous/systemfactory.h
index 31168e8ce..8b23355a1 100644
--- a/src/miscellaneous/systemfactory.h
+++ b/src/miscellaneous/systemfactory.h
@@ -19,6 +19,7 @@
 #define SYSTEMFACTORY_H
 
 #include <QObject>
+
 #include <QPointer>
 #include <QMutex>
 #include <QMetaType>
diff --git a/src/network-web/networkfactory.h b/src/network-web/networkfactory.h
index c6707ca2d..d45c50b47 100644
--- a/src/network-web/networkfactory.h
+++ b/src/network-web/networkfactory.h
@@ -19,7 +19,7 @@
 #define NETWORKFACTORY_H
 
 #include <QNetworkReply>
-#include <QApplication>
+#include <QCoreApplication>
 
 
 class NetworkFactory {
diff --git a/src/network-web/silentnetworkaccessmanager.cpp b/src/network-web/silentnetworkaccessmanager.cpp
index 05ea2bd4f..e8f5d504c 100644
--- a/src/network-web/silentnetworkaccessmanager.cpp
+++ b/src/network-web/silentnetworkaccessmanager.cpp
@@ -19,7 +19,6 @@
 
 #include <QNetworkReply>
 #include <QAuthenticator>
-#include <QApplication>
 
 
 SilentNetworkAccessManager::SilentNetworkAccessManager(QObject *parent)
diff --git a/src/network-web/webbrowsernetworkaccessmanager.cpp b/src/network-web/webbrowsernetworkaccessmanager.cpp
index 4b2db15ed..567eed16a 100644
--- a/src/network-web/webbrowsernetworkaccessmanager.cpp
+++ b/src/network-web/webbrowsernetworkaccessmanager.cpp
@@ -17,8 +17,9 @@
 
 #include "network-web/webbrowsernetworkaccessmanager.h"
 
+#include "application.h"
+
 #include <QNetworkReply>
-#include <QApplication>
 
 
 QPointer<WebBrowserNetworkAccessManager> WebBrowserNetworkAccessManager::s_instance;
diff --git a/src/network-web/webfactory.cpp b/src/network-web/webfactory.cpp
index 13941bc71..b02d590e2 100644
--- a/src/network-web/webfactory.cpp
+++ b/src/network-web/webfactory.cpp
@@ -2,8 +2,8 @@
 
 #include "definitions/definitions.h"
 #include "miscellaneous/settings.h"
+#include "application.h"
 
-#include <QApplication>
 #include <QRegExp>
 #include <QWebSettings>
 #include <QProcess>
diff --git a/src/network-web/webview.cpp b/src/network-web/webview.cpp
index 03b2f9eb1..a0276ff4a 100644
--- a/src/network-web/webview.cpp
+++ b/src/network-web/webview.cpp
@@ -54,7 +54,7 @@ void WebView::onLoadFinished(bool ok) {
 }
 
 void WebView::copySelectedText() {
-  QApplication::clipboard()->setText(selectedText());
+  Application::clipboard()->setText(selectedText());
 }
 
 void WebView::openLinkInNewTab() {
diff --git a/src/updater/formupdater.cpp b/src/updater/formupdater.cpp
index 8180eb95d..f96c1ce2b 100644
--- a/src/updater/formupdater.cpp
+++ b/src/updater/formupdater.cpp
@@ -1,9 +1,25 @@
+// This file is part of RSS Guard.
+//
+// Copyright (C) 2011-2014 by Martin Rotter <rotter.martinos@gmail.com>
+//
+// RSS Guard 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 3 of the License, or
+// (at your option) any later version.
+//
+// RSS Guard 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 RSS Guard. If not, see <http://www.gnu.org/licenses/>.
+
 #include "updater/formupdater.h"
 
 #include "definitions/definitions.h"
 #include "qtsingleapplication/qtsingleapplication.h"
 
-#include <QApplication>
 #include <QDesktopWidget>
 #include <QIcon>
 #include <QDir>
@@ -19,12 +35,17 @@
 #include <QTimer>
 
 
+FormUpdater *FormUpdater::s_instance;
+
 FormUpdater::FormUpdater(QWidget *parent)
   : QMainWindow(parent, Qt::Dialog | Qt::WindowStaysOnTopHint),
     m_state(NoState),
     m_txtOutput(new QTextEdit(this)),
     m_parsedArguments(QHash<QString, QString>())  {
 
+  // Initialize singleton.
+  s_instance = this;
+
   m_txtOutput->setAutoFormatting(QTextEdit::AutoNone);
   m_txtOutput->setAcceptRichText(true);
   m_txtOutput->setFontPointSize(10.0);
@@ -41,16 +62,21 @@ FormUpdater::FormUpdater(QWidget *parent)
   setWindowIcon(QIcon(APP_ICON_PATH));
 
   moveToCenterAndResize();
+
+  connect(this, SIGNAL(debugMessageProduced(QtMsgType,QString)),
+          this, SLOT(consumeDebugMessage(QtMsgType,QString)));
 }
 
 FormUpdater::~FormUpdater() {
 }
 
 void FormUpdater::startUpgrade() {
+  qDebug("Started...");
+
   printHeading("Welcome to RSS Guard updater");
   printText("Analyzing updater arguments.");
 
-  if (QApplication::arguments().size() != 5) {
+  if (QtSingleApplication::arguments().size() != 5) {
     printText("Insufficient arguments passed. Update process cannot proceed.");
     printText("\nPress any key to exit updater...");
 
@@ -70,23 +96,14 @@ void FormUpdater::startUpgrade() {
   }
 
   doFinalCleanup();
-
-  printText("Application was upgraded without serious errors.");
-
-  if (!QProcess::startDetached(m_parsedArguments["rssguard_executable_path"])) {
-    printText("RSS Guard was not started successfully. Start it manually.");
-    m_state = ExitError;
-  }
-  else {
-    m_state = ExitNormal;
-  }
+  executeMainApplication();
 
   printText("\nPress any key to exit updater...");
 }
 
 void FormUpdater::saveArguments() {
   // Obtain parameters.
-  QStringList arguments = QApplication::arguments();
+  QStringList arguments = QtSingleApplication::arguments();
 
   m_parsedArguments["updater_path"] = QDir::toNativeSeparators(qApp->applicationFilePath());
   m_parsedArguments["current_version"] = arguments.at(1);
@@ -98,6 +115,70 @@ void FormUpdater::saveArguments() {
   m_parsedArguments["output_temp_path"] = m_parsedArguments["temp_path"] + QDir::separator() + APP_LOW_NAME;
 }
 
+void FormUpdater::executeMainApplication() {
+  printText("\nApplication was upgraded without serious errors.");
+
+  if (!QProcess::startDetached(m_parsedArguments["rssguard_executable_path"])) {
+    printText("RSS Guard was not started successfully. Start it manually.");
+    m_state = ExitError;
+  }
+  else {
+    m_state = ExitNormal;
+  }
+}
+
+void FormUpdater::triggerDebugMessageConsumption(QtMsgType type, const QString &message) {
+  emit debugMessageProduced(type, message);
+}
+
+void FormUpdater::consumeDebugMessage(QtMsgType type, const QString &message) {
+  switch (type) {
+    case QtDebugMsg:
+      s_instance->printText(QString("DEBUG: %1").arg(message));
+      break;
+
+    case QtWarningMsg:
+      s_instance->printText(QString("WARNING: %1").arg(message));
+      break;
+
+    case QtCriticalMsg:
+      s_instance->printText(QString("CRITICAL: %1").arg(message));
+      break;
+
+    case QtFatalMsg:
+      s_instance->printText(QString("FATAL: %1").arg(message));
+      qApp->exit(EXIT_FAILURE);
+
+    default:
+      break;
+  }
+}
+
+#if QT_VERSION >= 0x050000
+void FormUpdater::debugHandler(QtMsgType type,
+                               const QMessageLogContext &placement,
+                               const QString &message) {
+#ifndef QT_NO_DEBUG_OUTPUT
+  Q_UNUSED(placement)
+
+  s_instance->triggerDebugMessageConsumption(type, message);
+#else
+  Q_UNUSED(type)
+  Q_UNUSED(placement)
+  Q_UNUSED(message)
+#endif
+}
+#else
+void FormUpdater::debugHandler(QtMsgType type, const char *message) {
+#ifndef QT_NO_DEBUG_OUTPUT
+  s_instance->triggerDebugMessageConsumption(type, QString(message));
+#else
+  Q_UNUSED(type)
+  Q_UNUSED(message)
+#endif
+}
+#endif
+
 void FormUpdater::printArguments() {
   printNewline();
   printHeading("Arguments");
@@ -145,7 +226,7 @@ bool FormUpdater::doPreparationCleanup() {
 
     printText(QString("Check for running instances of RSS Guard, attempt %1.").arg(i));
 
-    if (static_cast<QtSingleApplication*>(qApp)->sendMessage(APP_QUIT_INSTANCE)) {
+    if (static_cast<QtSingleApplication*>(QCoreApplication::instance())->sendMessage(APP_QUIT_INSTANCE)) {
       printText("The main application is running. Quitting it.");
       printText("Waiting for 6000 ms for main application to finish.");
 
@@ -198,7 +279,7 @@ bool FormUpdater::doExtractionAndCopying() {
 
   extractor_arguments << "x" << "-r" << "-y" <<
                          QString("-o%1").arg(m_parsedArguments["output_temp_path"]) <<
-                         m_parsedArguments["update_file_path"];
+                                                                                       m_parsedArguments["update_file_path"];
 
   printText(QString("Calling extractor %1 with these arguments:").arg(APP_7ZA_EXECUTABLE));
 
@@ -209,13 +290,7 @@ bool FormUpdater::doExtractionAndCopying() {
   process_extractor.setEnvironment(QProcessEnvironment::systemEnvironment().toStringList());
   process_extractor.setWorkingDirectory(m_parsedArguments["rssguard_path"]);
 
-  QString prog_line = QString(APP_7ZA_EXECUTABLE) + " " +
-                      "x -r -y \"-o" + m_parsedArguments["output_temp_path"] +
-                      "\" \"" + m_parsedArguments["update_file_path"] + "\"";
-  printText(prog_line);
-
-  process_extractor.start(prog_line);
-  //process_extractor.start(APP_7ZA_EXECUTABLE, extractor_arguments);
+  process_extractor.start(APP_7ZA_EXECUTABLE, extractor_arguments);
 
   if (!process_extractor.waitForFinished()) {
     process_extractor.close();
@@ -252,13 +327,22 @@ bool FormUpdater::doExtractionAndCopying() {
 }
 
 bool FormUpdater::doFinalCleanup() {
+  bool result_file;
+  bool result_path;
+
   qApp->processEvents();
 
   printNewline();
   printHeading("Final cleanup");
 
-  return removeDirectory(m_parsedArguments["output_temp_path"]) &&
-      QFile::remove(m_parsedArguments["update_file_path"]);
+  result_path = removeDirectory(m_parsedArguments["output_temp_path"]);
+  result_file = QFile::remove(m_parsedArguments["update_file_path"]);
+
+  printText(QString("Removing temporary files\n   -> %1 -> %2\n   -> %3 -> %4").arg(
+              m_parsedArguments["output_temp_path"], result_path ? "success" : "failure",
+            m_parsedArguments["update_file_path"], result_file ? "success" : "failure"));
+
+  return result_file && result_path;
 }
 
 void FormUpdater::keyPressEvent(QKeyEvent* event) {
diff --git a/src/updater/formupdater.h b/src/updater/formupdater.h
index 44ff4a1b2..35cff9480 100644
--- a/src/updater/formupdater.h
+++ b/src/updater/formupdater.h
@@ -1,8 +1,26 @@
+// This file is part of RSS Guard.
+//
+// Copyright (C) 2011-2014 by Martin Rotter <rotter.martinos@gmail.com>
+//
+// RSS Guard 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 3 of the License, or
+// (at your option) any later version.
+//
+// RSS Guard 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 RSS Guard. If not, see <http://www.gnu.org/licenses/>.
+
 #ifndef FORMUPDATER_H
 #define FORMUPDATER_H
 
 #include <QMainWindow>
 
+#include <QtGlobal>
 #include <QHash>
 
 
@@ -13,6 +31,7 @@ class FormUpdater : public QMainWindow {
     Q_OBJECT
 
   public:
+    // Describes the state of updater.
     enum UpdaterState {
       NoState,
       ExitNormal,
@@ -23,6 +42,11 @@ class FormUpdater : public QMainWindow {
     explicit FormUpdater(QWidget *parent = 0);
     virtual ~FormUpdater();
 
+    // Prints various texts.
+    void printText(const QString &text);
+    void printNewline();
+    void printHeading(const QString &header);
+
     // Starts the whole update process.
     void startUpgrade();
 
@@ -33,17 +57,34 @@ class FormUpdater : public QMainWindow {
     bool doPreparationCleanup();
     bool doExtractionAndCopying();
     bool doFinalCleanup();
+    void executeMainApplication();
+
+    // Used to trigger signal informaing about new debug message.
+    void triggerDebugMessageConsumption(QtMsgType type, const QString &message);
+
+    // Debug handlers for messages.
+#if QT_VERSION >= 0x050000
+    static void debugHandler(QtMsgType type,
+                             const QMessageLogContext &placement,
+                             const QString &message);
+#else
+    static void debugHandler(QtMsgType type,
+                             const char *message);
+#endif
+
+  public slots:
+    // Should be always called on GUI thread which is enforced
+    // by signal/slot auto connection.
+    void consumeDebugMessage(QtMsgType type, const QString &message);
+
+  signals:
+    // Emitted if new debug messaages is produced and should be printed.
+    void debugMessageProduced(QtMsgType type, QString message);
 
   protected:
     // Catch the "press any key event" to exit the updater.
     void keyPressEvent(QKeyEvent *event);
 
-  private:
-    // Prints various texts.
-    void printText(const QString &text);
-    void printNewline();
-    void printHeading(const QString &header);
-
     // Moves the window into the center of the screen and resizes it.
     void moveToCenterAndResize();
 
@@ -56,8 +97,9 @@ class FormUpdater : public QMainWindow {
   private:
     UpdaterState m_state;
     QTextEdit *m_txtOutput;
-
     QHash<QString, QString> m_parsedArguments;
+
+    static FormUpdater *s_instance;
 };
 
 #endif // FORMUPDATER_H
diff --git a/src/updater/main.cpp b/src/updater/main.cpp
index 5d9963eb2..9a638a8c1 100644
--- a/src/updater/main.cpp
+++ b/src/updater/main.cpp
@@ -26,8 +26,6 @@
 #include <QFileInfo>
 #include <QDir>
 
-#include <iostream>
-#include <limits>
 
 // Main entry point to "rssguard_updater.exe".
 // It expects 4 ARGUMENTS:
@@ -39,11 +37,17 @@
 int main(int argc, char *argv[]) {
   // Instantiate base application object.
   QtSingleApplication application(APP_LOW_NAME, argc, argv);
-
-  application.setQuitOnLastWindowClosed(true);
+  QtSingleApplication::setQuitOnLastWindowClosed(true);
 
   FormUpdater main_form;
 
+  // Setup debug output system.
+#if QT_VERSION >= 0x050000
+  qInstallMessageHandler(FormUpdater::debugHandler);
+#else
+  qInstallMsgHandler(FormUpdater::debugHandler);
+#endif
+
   main_form.show();
   main_form.startUpgrade();