Prevent post-compilation Qt downgrades (#2576)

* Abort the app if a Qt downgrade is detected

The app will now exit immediately if it was compiled with a Qt version
higher than the one present on the machine.

* Add function for checking the Qt version at runtime

* Re-register global D-Bus menu only if DE is Unity

src/core/Tools.h

@@ -41,8 +41,10 @@ namespace Tools
     void sleep(int ms);
     void wait(int ms);
     QString uuidToHex(const QUuid& uuid);
-    QRegularExpression convertToRegex(const QString& string, bool useWildcards = false,
-                                      bool exactMatch = false, bool caseSensitive = false);
+    QRegularExpression convertToRegex(const QString& string,
+                                      bool useWildcards = false,
+                                      bool exactMatch = false,
+                                      bool caseSensitive = false);
 
     template <typename RandomAccessIterator, typename T>
     RandomAccessIterator binaryFind(RandomAccessIterator begin, RandomAccessIterator end, const T& value)
@@ -83,6 +85,20 @@ namespace Tools
         void clear();
         QByteArray content() const;
     };
+
+    inline int qtRuntimeVersion()
+    {
+        // Cache the result since the Qt version can't change during
+        // the execution, computing it once will be enough
+        const static int version = []() {
+            const auto sq = QString::fromLatin1(qVersion());
+            return (sq.section(QChar::fromLatin1('.'), 0, 0).toInt() << 16)
+                   + (sq.section(QChar::fromLatin1('.'), 1, 1).toInt() << 8)
+                   + (sq.section(QChar::fromLatin1('.'), 2, 2).toInt());
+        }();
+
+        return version;
+    }
 } // namespace Tools
 
 #endif // KEEPASSX_TOOLS_H

src/gui/MainWindow.cpp

@@ -33,6 +33,7 @@
 #include "core/FilePath.h"
 #include "core/InactivityTimer.h"
 #include "core/Metadata.h"
+#include "core/Tools.h"
 #include "gui/AboutDialog.h"
 #include "gui/DatabaseWidget.h"
 #include "gui/SearchWidget.h"
@@ -1017,11 +1018,14 @@ void MainWindow::toggleWindow()
         // see https://github.com/keepassxreboot/keepassxc/issues/271
         // and https://bugreports.qt.io/browse/QTBUG-58723
         // check for !isVisible(), because isNativeMenuBar() does not work with appmenu-qt5
-        if (!m_ui->menubar->isVisible()) {
-            QDBusMessage msg = QDBusMessage::createMethodCall("com.canonical.AppMenu.Registrar",
-                                                              "/com/canonical/AppMenu/Registrar",
-                                                              "com.canonical.AppMenu.Registrar",
-                                                              "RegisterWindow");
+        const static auto isDesktopSessionUnity = qgetenv("XDG_CURRENT_DESKTOP") == "Unity";
+
+        if (isDesktopSessionUnity && Tools::qtRuntimeVersion() < QT_VERSION_CHECK(5, 9, 0)
+            && !m_ui->menubar->isVisible()) {
+            QDBusMessage msg = QDBusMessage::createMethodCall(QStringLiteral("com.canonical.AppMenu.Registrar"),
+                                                              QStringLiteral("/com/canonical/AppMenu/Registrar"),
+                                                              QStringLiteral("com.canonical.AppMenu.Registrar"),
+                                                              QStringLiteral("RegisterWindow"));
             QList<QVariant> args;
             args << QVariant::fromValue(static_cast<uint32_t>(winId()))
                  << QVariant::fromValue(QDBusObjectPath("/MenuBar/1"));

src/main.cpp

@@ -46,6 +46,8 @@ Q_IMPORT_PLUGIN(QXcbIntegrationPlugin)
 
 int main(int argc, char** argv)
 {
+    QT_REQUIRE_VERSION(argc, argv, QT_VERSION_STR)
+
 #if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
     QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
 #endif