Re: Issue 3491: Add \displayMarkup command. (issue 12732043)

[ianhulin44]

Use David's wording for EM with some tweaks.

Re \displayMarkup \displayScheme:
Markup needs some special-casing as we have our own home-brew
customisable/extensible interpreter in there for interpreting \markup
arguments.  The markup interpreter sometimes does some surprising things
under the bonnet - like implicitly wrapping markup commands in #:line.
Would \displayScheme make debugging markups easier or more difficult?
Should we have a \display <class> <expression> or \dump <class>
<expression> API to part-interpret a LilyPond expression to
scheme-primitives, display these to the console and/or file and *never*
affect the output document?  We now have \displayMusic,
\displayLilyMusic, \displayMarkup (and potentially \displayScheme), so
perhaps we need a one-stop shop function to interpret
Music/Markup/Scheme? E.g. \dump 'Music {c'4 e f g},
\dump 'Markup {\italic { "Hello " \bold {"Pond!"}}},
\dump 'Scheme #(reverse (list "Pond!" "the " "from " "Hello ")
These are good ideas but maybe stuff for another issue, given that
Mark's original fix was to clarify obtuse wording in the EM.

Ian


https://codereview.appspot.com/12732043/diff/7001/Documentation/extending/programming-interface.itely
File Documentation/extending/programming-interface.itely (right):

https://codereview.appspot.com/12732043/diff/7001/Documentation/extending/programming-interface.itely#newcode650
Documentation/extending/programming-interface.itely:650: To prevent the
markup from printing on the page, use
"By default, @code{\displayMarkup} displays the markup and also returns
it for use in the document.  This allows you to insert
@code{\displayMarkup} before a markup expression in the document without
changing the resulting document.
If you only want the markup to be displayed but not used in the
document, use @code{\void \displayMarkup} instead."

https://codereview.appspot.com/12732043/