transparent measures

[Andrzej Kopeć]

Hi there,
during my adventure with lilypond I came across a problem of invisible 
measures.  I need to have some of bars in some staves quite transparent. 
To do so I moved the Staff_system_engraver form Staff context to Voice 
(in addition this manipulation causes barlines to disappear, but 
nevertheless...). Then I tried to make a bar (put in separate voice 
context) in one staff transparent by changing its "transparent" 
property, but it didn't work. But -- the same operation worked refering 
to "thickness" property. I don't know if my way of thinking is going in 
right way, but if someone has any idea, I would be greatful :)

And some code illustrating the problem:

\version "2.4.2"

%this doesn't seem to change anything
%staOFF = { \override Staff.StaffSymbol #'transparent = ##t }
%staON = { \revert Staff.StaffSymbol #'transparent }

%this does its work.
staOFF = { \override StaffSymbol #'thickness = 2 }
staON = { \revert StaffSymbol #'thickess }

vnTwo = \relative c' {
\context Voice ="Vn" { r1 | c4 r4 r2 }
\context Voice ="Vnt" { \staOFF s1 } 
\context Voice ="Vn" { |  c4 }
}

vn = \relative c' {
r1
| c4 d e f |
}

\layout {
 \context {
   \Staff
   \remove "Staff_symbol_engraver"
 }
 \context {
   \Voice
   \consists "Staff_symbol_engraver"
 }
}

\score { <<
 \context StaffGroup = "violiniI" <<
   \context Staff ="vnI" \vn
   \context Staff ="vnII" \vn
   \context Staff ="vnIII" \vnWithGap
   \context Staff ="vnIV" \vn
   \context Staff ="vnV" \vn
   >>
%here come other instrumental groups
>>
}


Sincerly yours,
Andrew

PS. I'm working on linux Gentoo (x86), but this should be of no 
importance, shouldn't it?