4 Typesetting Racket Code
The slideshow/code library
provides utilities for typesetting Racket code as a pict.
Produces a pict for code in the given syntax object
source-location information of the syntax object determines the line
breaks, line indenting, and space within a row. Empty rows are
Beware that if you use read-syntax on a file port, you may
have to turn on line counting via port-count-lines! for the
code to typeset properly. Also beware that when a source file
containing a syntax or quote-syntax form is
compiled, source location information is omitted from the compiled
Normally, typeset-code is used through the code
syntactic form, which works properly with compilation, and that
escapes to pict-producing code via unsyntax. See also
Embedded picts within stx are used directly. Row elements are
combined using and operator like htl-append, so use
code-align (see below) as necessary to add an ascent to
ascentless picts. More precisely, creation of a line of code uses
pict-last to determine the end point of the element most
recently added to a line; the main effect is that closing parentheses
are attached in the right place when a multi-line pict is embedded in
An identifier that starts with _ is italicized in the pict,
and the _ is dropped, unless the
code-italic-underscore-enabled parameter is set to
#f. Also, unless code-scripts-enabled is set to
#f, _ and ^ in the middle of a word
create superscripts and subscripts, respectively (like TeX); for
example foo^4_ok is displayed as the identifier
foo with a 4 superscript and an
Further, uses of certain identifiers in stx typeset
code:blank — produces a space.
(code:comment s ...)
— produces a comment block, with each s on its own line,
where each s must be a string or a pict.
(code:line datum ...)
— typesets the datum sequence, which is mostly useful for
the top-level sequence, since typeset-code accepts only one
(code:contract datum ...) — like code:line, but every datum
is colored as a comment, and a ; is prefixed to every line.
(code:template datum ...) — like code:line, but a ; is
prefixed to every line.
$ — typesets as a vertical bar (for no
particularly good reason).
For more information, see typeset-code and
define-code, since code is defined as
(define-code code typeset-code)
Parameter for a base font used to typeset text. The default is
`(bold . modern)
. For even more control, see
Parameter for a one-argument procedure to turn a
string into a pict, used to typeset text. The default is
(lambda (s) (text s (current-code-font) (current-font-size)))
This procedure is not used to typeset subscripts or other items that
require font changes, where current-code-font is used
A parameter that determines the spacing between lines of typeset code.
The default is 2.
A parameter for the color of comments.
A parameter for the color of identifiers that are not syntactic form
names or constants.
A parameter for the color of literal values, such as strings and
numbers. See also current-literal-list
A parameter for the color of everything else.
Parameter for a list of symbols indicating which built-in reader forms
should be used. The default is ''quasiquote.
Remove a symbol to suppress the corresponding reader output.
Adjusts the ascent of pict so that its bottom aligns with the
baseline for text; use this function when pict has no
A list of strings to color as syntactic-form names. The default
includes all of the forms provided by racket/base
and all of the forms provided by mzscheme
A list of strings to color as constant names. The default is
A list of strings to color as literals, in addition to literals such
as strings. The default is null
A parameter to enable or disable all code coloring. The default is
A parameter to control whether under a quote
is colorized as
a literal (as in this documentation). The default is #t
A parameter to control whether _-prefixed identifiers are
italicized (dropping the _). The default is #t.
A parameter to control whether TeX-style subscripts and subscripts are
recognized in an identifier.
as a macro that uses
, which is a function with the same input as
. The escape-id
form defaults to
The resulting code-id syntactic form takes a sequence of
(code-id datum ...)
It produces a pict that typesets the sequence. Source-location
information for the datum determines the layout of code in
the resulting pict. The code-id is expanded in such a way
that source location is preserved during compilation (so
typeset-code-id receives a syntax object with source
If a datum contains (escape-id expr)—perhaps as
#,expr when escape-id is unsyntax—then
the expr is evaluated and the result datum is spliced in
place of the escape-id form in datum. If the result
is not a syntax object, it is given the source location of the
escape-id form. A pict value intected this way as a
datum is rendered as itself.
to the result of (code datum ...)
except that if an identifier _
appears anywhere in a
, then the identifier and the following expression are
not included for code
Meanwhile, runnable-id is bound to a syntax object that wraps
the datums in a begin. In this case,
_s are removed from the datums, but not the
following expression. Thus, an _ identifier is used to
comment out an expression from the pict, but have it present in the
syntax object for evaluation.
The string-id is bound to a string representation of the code
that is in the pict. This string is useful for copying to the
clipboard with (send the-clipboard set-clipboard-string string-id 0).
The same as pict-last
, provided for backward compatibility.
Mainly for backward compatibility: returns (if bl-pict (use-last pict (or (pict-last bl-pict) bl-pict)))