other trill-spanner stuff

[David Bobroff]

I have three questions about the trill extender.

In the example below I have set the #'edge-height = #'(4 . 0) in order
to show the vertical dash that appears at the beginning of the trill
extender.  If I put a non-zero value in the other position I get a
similar vertical dash at the ending point of the extender.  What is
this?  Bug?

Also, should the beginning of the trill extender actually touch the
\trill the way it does (assuming it has not been set so far above or
below the \trill)?

What is the usual height placement of such trill extenders?  Placing it
level with the top half of the 'r' *looks* about right to me but I don't
have engraved examples at my disposal for comparison.

-David

\score {
    \notes \relative c'{   
    \override TextSpanner #'style = #'trill
    \override TextSpanner #'edge-height = #'(4 . 0 )
    \override TextSpanner #'edge-text 
    = #'((line (music "scripts-trill") " ") . "")
    c1-\trill-\startTextSpan ~
    c8-\stopTextSpan r8 r4 r2
        }
    \paper { linewidth = 8 \cm }
}