Within my application I want to show a screensaver/lock screen after a time out. To keep it separate from application a plugin would be nice. (I have already a virtual keyboard plugin). I have seen the class Qt4.8 QWSScreenSaver but it seems it is not available in Qt5.
Is an screensaver / lock screen interface available?
Do you mean in an embedded device ?
when you are on desktop platforms you can use the QtSystems module. It contains a QScreenSaver class.
It is managed officially by Qt team but not (yet?) released. So you need to download and build it yourself.
Note: i haven't tested it myself yet.