conversion factor for \pt

[Thomas Morley]

Hi,

in the following markup I want draw-line to have the same Y-length as the brace.

\version "2.16.2"

factor = #0.175  % a rough estimation, and for default-staff-size only
size = #40

\markup {
        \left-brace #size
        \translate #`(0 . ,(/ (* size factor) -2))
        \draw-line #`(0 . ,(* size factor))
}

The size of \left-brace is measured in pts according to it's
definition in /scm/define-markup-commands, "feta brace in point size",
and is absolute.
\draw-line uses staff-spaces, afaik.

I need the conversion factor for default and non-default-staff-size.

Well, there is
http://lilypond.org/doc/v2.17/Documentation/notation/distances-and-measurements

But I couldn't figure it out.

How to do it?


Regards,
  Harm