Markup module patch (Issue 2026)

[Ian Hulin]

Hi all,
The patch had to get pulled from staging as although it passed reg.
tests it wouldn't compile the doc.  I can easily fix the snippet in
/Documentation/snippets/three-sided-box.ly, but this leaves one more
problem in the docs, this time in /extending/.

I pulled out and tested the examples in separate .ly file and the
format that fails is
#(define-markup-command (double-box layout props text) (markup?)
  "Draw a double box around text."
  (interpret-markup layout props
    #{\markup \override #'(box-padding . 0.4) \box
            \override #'(box-padding . 0.6) \box { $text }#}))
\markup \double-box A

but
#(define-markup-command (double-box layout props text) (markup?)
  "Draw a double box around text."
  (interpret-markup layout props
    (markup #:override '(box-padding . 0.4) #:box
            #:override '(box-padding . 0.6) #:box text)))
\markup \double-box A

works fine.  This is not restricted to the double-box thing, it's
general to doing
interpret-markup #{ \markup \markup-command #'par ... #} within a
#(define-markup-command ...  ) block.  I'd like to deprecate this as I
think it's nasty, smelly, evil and kludgy and ask that users use

interpret-markup ( markup #:markup-command 'par ... ) instead.

We'd mark this as such in NEWS, meanwhile taking out the offending
examples from /extending/.

WDYT?

Cheers,

Ian