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2.5.4 New markup list command definition
Markup list commands are defined with the
define-markup-list-command Scheme macro, which is similar to the
define-markup-command macro described in
New markup command definition, except that where the latter returns
a single stencil, the former returns a list of stencils.
In a similar vein, interpret-markup-list is used instead of
interpret-markup for converting a markup list into a list
of stencils.
In the following example, a \paragraph markup list command is
defined, which returns a list of justified lines, the first one being
indented. The indent width is taken from the props argument.
#(define-markup-list-command (paragraph layout props args) (markup-list?)
#:properties ((par-indent 2))
(interpret-markup-list layout props
#{\markuplist \justified-lines { \hspace #par-indent #args } #}))
The version using just Scheme is more complex:
#(define-markup-list-command (paragraph layout props args) (markup-list?)
#:properties ((par-indent 2))
(interpret-markup-list layout props
(make-justified-lines-markup-list (cons (make-hspace-markup par-indent)
args))))
Besides the usual layout and props arguments, the
paragraph markup list command takes a markup list argument, named
args. The predicate for markup lists is markup-list?.
First, the function gets the indent width, a property here named
par-indent, from the property list props. If the
property is not found, the default value is 2. Then, a
list of justified lines is made using the built-in markup list command
\justified-lines, which is related to the
make-justified-lines-markup-list function. A
horizontal space is added at the beginning using \hspace (or the
make-hspace-markup function). Finally, the markup list is
interpreted using the interpret-markup-list function.
This new markup list command can be used as follows:
\markuplist {
\paragraph {
The art of music typography is called \italic {(plate) engraving.}
The term derives from the traditional process of music printing.
Just a few decades ago, sheet music was made by cutting and stamping
the music into a zinc or pewter plate in mirror image.
}
\override-lines #'(par-indent . 4) \paragraph {
The plate would be inked, the depressions caused by the cutting
and stamping would hold ink. An image was formed by pressing paper
to the plate. The stamping and cutting was completely done by
hand.
}
}
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