Manual volta repeat commands [was Re: Quoted text]

[John Mandereau]

On 2008/05/29, Risto Vääräniemi wrote:
> I noticed that the LP front page states that "LilyPond now allows all
> text context properties to be markups". This does not yet cover volta
> brackets, though. That is Score.repeatCommands, which only accepts
> plain text. If you try to enter a markup the volta bracket disappears
> completely. I guess this is a bit more difficult to fix/change because
> to get some normal text inside volta brackets you have make some
> special overrides, i.e., font encoding, font family etc.

The volta text can already be a markup actually, but as this markup is
the second element of a list, which is itself contained in the
repeatCommands list, it's not obvious to set it.  BTW I fixed the
misleading description of repeatCommands in the Internals Reference.


>         \set Score.repeatCommands = #'((volta \markup {"markup"} ))

This won't work, because \markup is a LilyPond command, so it doesn't
work within Scheme; you should use something like
(markup #:line (#:simple "blablah"))
and as a consequence, you cannot use a list of constants (the first
quote character after the Scheme mark '#'), because you call Scheme
function markup.  You could use

\set Score.repeatCommands =
#(list (list 'volta (markup #:line (#:simple "blablah"))))

but it's cumbersome to write markups in Scheme syntax [1], so it's
easier to define the markup as a variable first:

myVoltaMarkup = \markup { bla \roman baz }
\set Score.repeatCommands = #(list (list 'volta myVoltaMarkup))

[1] if you still prefer to write a particular markup in Scheme, write it
first with a note and call \displayMusic on it:

foo = \displayMusic c'1^\markup { bla \roman baz }

then you can read Scheme code that could be used to generate this music
expression on standard output.


Maybe this example helps understanding how to set repeatCommands to a
list containing variables:
- expression of a list of constants: '((volta "93") end-repeat)
- an equivalent expression in a "developed" form, where you can replace
constants with variables:
(list (list 'volta "93") 'end-repeat)

Ralph, would you like to update the ly snippet in "Manual repeat marks"
with an example of setting a markup within repeatCommands, and add a
cross-reference to Volta_engraver?

Maybe something like

\set Score.repeatCommands = #(list (list 'volta (markup
  #:line (#:simple "1.2.3..." #:roman (#:italic "ad lib.")))) 'end-repeat)

or an equivalent form

voltaAdLib = \markup { "1.2.3..." \roman \italic "ad lib." }
\set Score.repeatCommands = #(list (list 'volta voltaAdLib) 'end-repeat)

is more realistic.  However, I can't make it work with Lily 2.11.46 (see
the end of this email for a complete input file), I got this:

Drawing systems.../usr/local/share/lilypond/2.11.46/scm/markup.scm:549:24: In 
procedure + in expression (+ space (cdr #)):
/usr/local/share/lilypond/2.11.46/scm/markup.scm:549:24: Wrong type argument in 
position 1: #f

Is it a bug or a missing feature?  It seems that using any markup more
complex than \markup { "foo" } doesn't work here, and the description in
repeat-commands doesn't mention markup can be used instead of a string.


Maybe explaining Scheme language features used in this example is
probably not relevant in the ly code or in the Repeats section.  I think
such explanation should be added to the Scheme tutorial; I add it to my
TODO list, but don't expect changes for this from me within one week.
Graham, may I freely edit the Scheme tutorial, or is it to be revised
soon under GDP?  IIRC this section has not a high priority in GDP, but
updating docs as questions from users arise is a good thing too.

Cheers,
John

%%% BEGIN LY %%%
\version "2.11.46"

voltaAdLib = \markup { "1.2.3..." \roman \italic "ad lib."}

\relative c'' {
c4
\set Score.repeatCommands = #(list (list 'volta voltaAdLib) 'end-repeat)
c4 b
d4 e
\set Score.repeatCommands = #'((volta #f))
}
%%% END LY %%%