collision of rehearsal marks, y-parent

[Werner LEMBERG]

While working on a big score together with proper parts extraction I
find that vertical positioning of rehearsal marks needs manual
adjustments most often.

Is it possible to add a collision resolver for rehearsal marks?  The
`padding' option doesn't work well since it is important that
rehearsal marks are as near as possible to the staff lines.

BTW, how can I find out in lilypond-internals.info the `parent' of a
grob?  For example, this is for RehearsalMark objects:

  `Y-offset' (number):
       `ly:side-position-interface::y-aligned-side'

       The vertical amount that this object is moved relative to its
       Y-parent

But what is the `Y-parent'?  It would be great if this information
could be added there.


    Werner