ProtectedabstractProtectedalignmentProtectedboundingProtectedgraphicalProtectedgraphicalProtectedlyricProtectedlyricsProtectedmeasuresProtectedoctaveProtectedparentProtectedparentProtectedskyProtectedslursProtectedstaffFind the [[GraphicalStaffEntry]] closest to the given xPosition.
True iff [[StaffLine]] belongs to an [[Instrument]] with more than one [[Staff]].
A StaffLine contains the [[Measure]]s in one line of the music sheet (one instrument, one line, until a line break)