ottava spanners

[Werner LEMBERG]

I need the following properties to get nice ottava spanners (see
attached image):

  \property Voice.TextSpanner \set #'type = #'dashed-line
  \property Voice.TextSpanner \set #'dash-length = #0.3
  \property Voice.TextSpanner \set #'dash-period = #0.5
  \property Voice.TextSpanner \set #'edge-height = #'(0 . 1.3)
  \property Voice.TextSpanner \set #'thickness = #1.5
  \property Voice.TextSpanner \set #'edge-text = #'("8" . "")
  \property Voice.TextSpanner \set #'font-shape = #'italic
  \property Voice.TextSpanner \set #'font-series = #'bold
  \property Voice.TextSpanner \set #'extra-offset = #'(0 . -1)

  \property Staff.centralCPosition = #-13

  a\spanrequest \start "text" b c a \spanrequest \stop "text"

Some problems:

  . I want that the ottava line starts at the top of the `8', not in
    the middle.  How can I shift down the `8'?

  . As can be seen above, I have to use `extra-offset' to move the
    ottava line nearer to the note heads.  I suggest that the value
    of `edge-height' is not taken into account for computing the
    distance between the note head and the ottava line.  At least for
    ottava lines this is not the right thing IMHO.

  . Normally, `8' should be left from the note head.  How can I
    achieve that?

  . How can I do the following easily?  The accent is on *easily*, of
    course -- I could solve it with splitted voice and turning off the
    note heads, but this is uuuuugly.

       |  |  |
       O  O  O
         8_|

    Having an ottava line for just a single bass note occurs quite
    frequently in piano music.

  . Another needed feature:  The ottava line should end immediately
    after the note head, not after the corresponding time unit.:

    Wrong:

         |           |           |
         O           O           O
        8_______________________|

    Right:

         |           |           |
         O           O           O
        8_____________|


  . A bug: Ottava lines as constructed above which are broken across
    lines don't appear correct:

               ______________________
              8                      | < this shouldn't be here.

               __________
              8          |


Conclusion: We need a better interface for ottava lines.


      Werner