A generic QWebEngineUrlSchemeHandler which takes data from KIO::storedGet has been added and is now used also for man and info URLs. The old WebEnginePartHtmlMimetypeHandler has been changed into a class which only embeds the content of file URLs in the HTML code.
I found out that several calls to QWebEngineUrlSchemeHandler::requestStarted may happen before the previous one has replied (it happened for the help protocol where the HTML code produced by KIO in turn contained help URLs). Because of this, I needed to implement a queuing mechanism in the new handler.
The new handler can be used as a base class if special processing of data produced by KIO is needed