title: Why does my Qt app ignore the setting of applicationDisplayName?
body: <p>I am running a small app on KDE Plasma 5 created with Qt and the KDE framework. Almost everything works like a charm, just one part doesn't work. I just cannot set the application display name. I have the following code:</p>
  
  <pre>
  
      int main(int argc, char **argv) {
          QApplication application(argc, argv);
  
          KLocalizedString::setApplicationDomain("blender-render-control");
          KCrash::initialize();
  
          KAboutData aboutData(QStringLiteral("blender-render-control-center"),
                               i18n("Blender Render Control Center"),
                               QStringLiteral("1.0"),
                               i18n("A simple application to control the blender render control server"),
                               KAboutLicense::Custom,
                               i18n("Copyright 2019, Knerd "));
  
          aboutData.addAuthor(i18n("Knerd"), i18n("Author"), QStringLiteral("knerd@knerd.knerd"));
          aboutData.setOrganizationDomain("knerd.knerd");
          aboutData.setDesktopFileName(QStringLiteral("knerd.knerd.blender-render-control"));
  
          KAboutData::setApplicationData(aboutData);
          QApplication::setWindowIcon(QIcon::fromTheme(QStringLiteral("knerd.knerd.blender-render-control")));
          application.setApplicationDisplayName(i18n("Blender Render Control Center"));
          application.setApplicationName(i18n("Blender Render Control Center"));
  
          QCommandLineParser parser;
          aboutData.setupCommandLine(&parser);
  
          parser.process(application);
          aboutData.processCommandLine(&parser);
  
          auto *window = new MainWindow();
          window->show();
  
          return QApplication::exec();
      }
  
  </pre>
  
  <p>From reading the docs and checking some examples, this should set the application title in my KDE environment. But it doesn't, the application name is the name of the executable.</p>
  
  <p>Is this a bug in KDE or am I doing something wrong?</p>