The setup of the input and output converters is fairly complex but was made harder to read by nearly-duplicating its logic for input and for output. Break out into a separate function to make clear what parts differ between the two and what parts don't. In the process, allow the search for a named converter to continue past a match that doesn't support the needed direction, on the off chance of a name collision. Make an error message more articulate in the process. Pick-to: 6.6 6.5 Task-number: QTBUG-111228 Change-Id: I2a9de8b406c538098076f388fc8a1980b91fe16b Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>