Glissando line, follow Staff

[Rune Zedeler]

I would like an a bit more sophisticated routine for calculating the
glissando lines.
Now, the line is just drawn from horisontally right of the first note to
horisontally left of the last note.
This is quite ugly especially when the notes are almost above each other
(sometimes the line is actually drawn backwards, argh). I would rather
like the line to be a part of the line connecting the CENTRE OF THE NOTE
HEADS.
followStaff is also a bit unintelligent; it should not draw a line if
the staff switch is already connected by a knee.
And a small bug: If you set \showStaffSwitch where no staff switch takes
place, a line is drawn between the two current notes.

By the way: How do you change the staff switch line to dashed?
I tried

\property Thread.Glisssando \set #'type = #'dashed-line

and

        \translator {
          \ThreadContext
          Glissando \override #'type = #'dashed-line
         }

but nothing happens.

-Rune