Add a pretitle style property for nested flows. (#94)

* Add a pretitle style property for nested flows.

This allows us to raise nested flows above the title. So that we do
things like raise the abstract above the title:

```
\begin{abstract}
Abstract text
\end{abstract}
\titleCommand{...}
```

This style is required by the acmart style guide.

* Paragraphs and nested flows extracted in the same order

* Fix `scribble/acmart`'s abstract form so that it gets lifted above `maketitle`, where it should be.

scribble-doc/scribblings/scribble/core.scrbl

@@ -729,6 +729,8 @@ The following @tech{style properties} are currently recognized:
  @item{@racket[alt-tag] structure --- Generates the indicated HTML tag
        instead of @tt{<blockquote>}.}
 
+ @item{@racket['pretitle] --- For Latex, raises the contents
+   of the flow to above the title.}
 ]}
 
 
@@ -1115,7 +1117,7 @@ reverse order):
        any number or lists element, while @racket[""] is used in place
        of all non-empty strings.}
 
-]}
+]
 
 @history[#:changed "6.4" @elem{Added @racket[(list/c string? string?)]
                                number items for

scribble-lib/scribble/acmart.rkt

@@ -141,7 +141,7 @@
 ;; ----------------------------------------
 ;; Abstracts:
 
-(define abstract-style (make-style "abstract" acmart-extras))
+(define abstract-style (make-style "abstract" (cons 'pretitle acmart-extras)))
 
 (define command-props (cons 'command acmart-extras))
 (define multicommand-props (cons 'multicommand acmart-extras))

scribble-lib/scribble/base-render.rkt

@@ -251,25 +251,42 @@
                     (document-date-text v)))
              (style-properties (part-style d))))
 
-    (define/private (extract-pre-paras d sym)
+    (define/private (extract-content d lift-proc)
       (let loop ([l (part-blocks d)])
-        (cond
+        (apply append
-         [(null? l) null]
+               (for/list ([b (in-list l)])
-         [else (let ([v (car l)])
+                 (define lifted (lift-proc b loop))
+                 lifted))))
+
+    (define/private (extract-pre-paras-proc sym)
+      (λ (v loop)
         (cond
           [(and (paragraph? v)
                 (eq? sym (style-name (paragraph-style v))))
-                   (cons v (loop (cdr l)))]
+           (list v)]
           [(compound-paragraph? v)
-                   (append (loop (compound-paragraph-blocks v))
+           (loop (compound-paragraph-blocks v))]
-                           (loop (cdr l)))]
+          [else '()])))
-                  [else (loop (cdr l))]))])))
+  
+    (define/private (extract-pre-content-proc sym)
+      (λ (v loop)
+        (define pre-para ((extract-pre-paras-proc sym) v loop))
+        (cond
+          [(not (null? pre-para)) pre-para]
+          [(and (nested-flow? v)
+                (member sym (style-properties (nested-flow-style v))))
+           (list v)]
+          [else '()])))
+
 
     (define/public (extract-authors d)
-      (extract-pre-paras d 'author))
+      (extract-content d (extract-pre-paras-proc 'author)))
     
     (define/public (extract-pretitle d)
-      (extract-pre-paras d 'pretitle))
+      (extract-content d (extract-pre-paras-proc 'pretitle)))
+
+    (define/public (extract-pretitle-content d)
+      (extract-content d (extract-pre-content-proc 'pretitle)))
     
     ;; ----------------------------------------
 

scribble-lib/scribble/latex-render.rkt

@@ -81,7 +81,7 @@
              extract-version
              extract-date
              extract-authors
-             extract-pretitle)
+             extract-pretitle-content)
 
     (define/public (extract-short-title d)
       (ormap (lambda (v)
@@ -150,14 +150,19 @@
           (when (part-title-content d)
             (let ([vers (extract-version d)]
                   [date (extract-date d)]
-                  [pres (extract-pretitle d)]
+                  [pres (extract-pretitle-content d)]
                   [auths (extract-authors d)]
                   [short (extract-short-title d)])
               (for ([pre (in-list pres)])
                 (printf "\n\n")
-                (do-render-paragraph pre d ri #t #f))
+                (cond
+                  [(paragraph? pre)
+                   (do-render-paragraph pre d ri #t #f)]
+                  [(nested-flow? pre)
+                   (do-render-nested-flow pre d ri #t #f #t)]))
               (when date (printf "\\date{~a}\n" date))
               (printf "\\titleAnd~aVersionAnd~aAuthors~a{"
+                      
                       (if (equal? vers "") "Empty" "")
                       (if (null? auths) "Empty" "")
                       (if short "AndShort" ""))
@@ -187,7 +192,7 @@
                          (and d (positive? d)))))
           (when (eq? (style-name (part-style d)) 'index)
             (printf "\\twocolumn\n\\parskip=0pt\n\\addcontentsline{toc}{section}{Index}\n"))
-          (let ([pres (extract-pretitle d)])
+          (let ([pres (extract-pretitle-content d)])
             (for ([pre (in-list pres)])
               (printf "\n\n")
               (do-render-paragraph pre d ri #t #f)))
@@ -645,6 +650,7 @@
                part 
                ri
                #t
+               #f
                #f)
               (when (string? s-name)
                 (printf "\\end{~a}" s-name)))
@@ -848,7 +854,7 @@
        [(table? p)
         (render-table* p part ri #f (format "[~a]" mode))]
        [(nested-flow? p)
-        (do-render-nested-flow p part ri #f mode)]
+        (do-render-nested-flow p part ri #f mode #f)]
        [(paragraph? p)
         (do-render-paragraph p part ri #f mode)]))
 
@@ -879,7 +885,7 @@
         (printf "\\end{~a}" mode)
         null))
 
-    (define/private (do-render-nested-flow t part ri single-column? as-box-mode)
+    (define/private (do-render-nested-flow t part ri single-column? as-box-mode show-pre?)
       (let* ([props (style-properties (nested-flow-style t))]
              [kind (or (and as-box-mode
                             (or
@@ -900,6 +906,8 @@
              [multicommand? (memq 'multicommand props)]
              [command? (or (and as-box-mode (not multicommand?))
                            (memq 'command props))])
+        (unless (and (not show-pre?)
+                     (member 'pretitle props))
           (cond
             [command? (printf "\\~a{" kind)]
             [multicommand? (printf "\\~a" kind)]
@@ -919,10 +927,10 @@
             [command? (printf "}")]
             [multicommand? (void)]
             [else (printf "\\end{~a}" kind)])
-        null))
+          null)))
 
     (define/override (render-nested-flow t part ri starting-item?)
-      (do-render-nested-flow t part ri #f #f))
+      (do-render-nested-flow t part ri #f #f #f))
 
     (define/override (render-compound-paragraph t part ri starting-item?)
       (let ([kind (style-name (compound-paragraph-style t))]