scribble/manual: add `current-display-width' parameter

collects/scribble/manual.rkt

@@ -11,11 +11,13 @@
          "private/manual-class.rkt"
          "private/manual-unit.rkt"
          "private/manual-vars.rkt"
-         "private/manual-bind.rkt")
+         "private/manual-bind.rkt"
+         "private/manual-utils.rkt")
 
 (provide unsyntax
          make-binding-redirect-elements
          defidentifier
+         current-display-width
          (all-from-out "base.rkt"
                        "private/manual-style.rkt"
                        "private/manual-scheme.rkt"

collects/scribble/private/manual-proc.rkt

@@ -140,6 +140,7 @@
 (define (*defproc mode within-id
                   stx-ids prototypes arg-contractss arg-valss result-contracts
                   content-thunk)
+  (define max-proto-width (current-display-width))
   (define ((arg->elem show-opt-start?) arg)
     (let* ([e (cond [(not (arg-special? arg))
                      (if (arg-kw arg)
@@ -561,6 +562,7 @@
 (define (*defstruct stx-id name alt-cname-id extra-cname?
                     fields field-contracts immutable? transparent? prefab?
                     content-thunk)
+  (define max-proto-width (current-display-width))
   (define (field-name f) ((if (pair? (car f)) caar car) f))
   (define (field-view f)
     (if (pair? (car f)) (make-shaped-parens (car f) #\[) (car f)))

collects/scribble/private/manual-utils.rkt

@@ -14,7 +14,7 @@
  [flow-spacer flow?]
  [flow-empty-line flow?]
  [make-table-if-necessary (content? list? . -> . (list/c (or/c omitable-paragraph? table?)))]
- [max-proto-width exact-nonnegative-integer?])
+ [current-display-width (parameter/c exact-nonnegative-integer?)])
 
 (define spacer (hspace 1))
 
@@ -31,4 +31,4 @@
         (list (make-table style content))))
     (list (make-table style content))))
 
-(define max-proto-width 65)
+(define current-display-width (make-parameter 65))

collects/scribblings/scribble/manual.scrbl

@@ -620,7 +620,9 @@ description, references to @svar[arg-id]s using @racket[racket],
 
 The typesetting of all information before the @racket[pre-flow]s
 ignores the source layout, except that the local formatting is
-preserved for contracts and default-values expressions.}
+preserved for contracts and default-values expressions. The information
+is formatted to fit (if possible) in the number of characters specified
+by the @racket[current-display-width] parameter.}
 
 
 @defform[(defproc* ([prototype
@@ -881,6 +883,11 @@ the mouse hovers over the identifier).}
 
 Compatibility aliases for @racket[racketgrammar] and @racket[racketgrammar*].}
 
+@defparam[current-display-width w exact-nonnegative-integer?]{
+
+Specifies the target maximum width in characters for the output of
+@racket[defproc] and @racket[defstruct].}
+
 
 @; ------------------------------------------------------------------------
 @section[#:tag "doc-classes"]{Documenting Classes and Interfaces}