Something broke since 2015, but I don’t know what. See:
    https://stackoverflow.com/questions/57994601/noclassdeffounderror-when-running-a-scala-swing-program-with-sbt

(The default window size does not adapt to its contents anymore, but it seems
impossible in Swing to do that while having a fixed width…)

window is full in order to take its content’s size into account).