Comment 115 for bug 1446865

For a KMainWindow solution, one should not require a nasty global eventfilter on the application - handling KMainWindow::closeEvent() should be sufficient, but there might be an additional pitfall on modal windows (ie. if there's already a save dialog, we might have to forcefully activate that to cause user interaction)

However, as long as QGuiApplication cancels the session lougout as long as any close event is ignored, this cannot be applied either (ie. still requires your new patch to Qt) and, of course, this doesn't provide a solution for Qt5 either - session management on Qt5 will remain broken forever and just some KDE applications work around that. That's a pretty crappy situation :-(