Hi Kieren,
I've never seen such list but it would be helpful.
Apparently, StaffSymbol.thickness affects spanners (not all of them) proportionally:
http://www.lilypond.org/doc/v2.19/Documentation/notation/spannersbut also ledger lines, stem thickness, beam length fraction, beam attachment... (others for sure) in a less predictable multiplier:
\version "2.19.35"
\score {
{
\new GrandStaff <<
\new Staff { c'''16 c' c''' c' c''' c' }
\new Staff { c'''16 c' c''' c' c''' c' }
>>
}
}
\markup\vspace #2
\score {
{
\new GrandStaff <<
\new Staff { c'''16\< c'\glissando c''' c'\startTrillSpan c''' c'\!\stopTrillSpan }
\new Staff { c'''16\startTextSpan c'~ c' c' c''' c'\stopTextSpan }
>>
}
\layout {
\context {
\Staff
\override StaffSymbol.thickness = 5
\override StaffSymbol.ledger-line-thickness = #'(0.13 . 0.13)
\override Stem.thickness = #0.25
\override Beam.length-fraction = #0.8
}
}
}
Not sure if that helps though... :(
Cheers,
Pierre