From dc898971b0a71389dbcc2c5aeccd63ed57a14006 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Fri, 18 Jan 2019 15:58:19 -0800
Subject: [PATCH] cracks

---
 quad/qtest/markdown.rkt | 42 ++++++++++++++++++++++++++---------------
 quad/quad/atomize.rkt   |  2 +-
 quad/quad/quad.rkt      |  5 +++++
 3 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/quad/qtest/markdown.rkt b/quad/qtest/markdown.rkt
index 6a10cb2f..91b5cc74 100644
--- a/quad/qtest/markdown.rkt
+++ b/quad/qtest/markdown.rkt
@@ -39,7 +39,7 @@
   (define new-exprs (add-between
                      (for*/list ([expr (in-list exprs)]
                                  [str (in-list (string-split (car (get-elements expr)) "\n"))])
-                                `(,(get-tag expr) ,(get-attrs expr) ,str))
+                       `(,(get-tag expr) ,(get-attrs expr) ,str))
                      lbr))
   (qexpr attrs new-exprs))
 
@@ -139,19 +139,31 @@
     (define new-run (struct-copy quad q:string
                                  [attrs (quad-attrs (car pcs))]
                                  [elems (merge-adjacent-strings (apply append (for/list ([pc (in-list run-pcs)])
-                                                                                        (quad-elems pc))))]
+                                                                                (quad-elems pc))))]
                                  [size (delay (pt (for/sum ([pc (in-list run-pcs)])
-                                                           (pt-x (size pc)))
+                                                    (pt-x (size pc)))
                                                   (pt-y (size (car pcs)))))]))
     (values (cons new-run runs) rest)))
 
 
 (struct line-break quad () #:transparent)
+(define (line-break-copy x as es)
+  (struct-copy line-break x
+               [attrs #:parent quad as]
+               [elems #:parent quad es]))
 (define lbr (q #:type line-break
-               #:printable #f))
+               #:copier line-break-copy
+               #:printable #f
+               #:elems '("foo bar")))
 (struct para-break line-break () #:transparent)
+(define (para-break-copy x as es)
+  (struct-copy para-break x
+               [attrs #:parent quad as]
+               [elems #:parent quad es]))
 (define pbr (q #:type para-break
-               #:printable #f))
+               #:copier para-break-copy
+               #:printable #f
+               #:elems '("¶¶")))
 
 (module+ test
   (check-true (line-break? (second (quad-elems (q "foo" pbr "bar")))))
@@ -169,8 +181,8 @@
                                                      (define container-val (hash-ref (quad-attrs (car new-elems)) 'container #f))
                                                      (when (and container-val
                                                                 (for/and ([elem (in-list (cdr new-elems))])
-                                                                         (equal? (hash-ref (quad-attrs elem) 'container #f)
-                                                                                 container-val)))
+                                                                  (equal? (hash-ref (quad-attrs elem) 'container #f)
+                                                                          container-val)))
                                                        (hash-set! attrs 'container container-val))
                                                      attrs)]
                                             [size (let ()
@@ -213,7 +225,7 @@
      #:elems pcs
      #:size (delay (pt (pt-x (size (car pcs)))
                        (for/sum ([pc (in-list pcs)])
-                                (pt-y (size pc)))))
+                         (pt-y (size pc)))))
      #:draw-start (λ (q doc)
                     (save doc)
                     (match-define (list left top) (quad-origin q))
@@ -260,13 +272,13 @@
   ;; iow, the lines within a container may be split over multiple pages, each of which should be drawn
   ;; as a separate container
   (for/list ([page (in-list pages)])
-            (define lns (quad-elems page))             
-            (define groups (contiguous-group-by (λ (x) (hash-ref (quad-attrs x) 'container #f)) lns))
-            (define lns-and-containers (append* (for/list ([grp (in-list groups)])
-                                                          (match (hash-ref (quad-attrs (car grp)) 'container #f)
-                                                            ["bq" (list (make-blockquote grp))]
-                                                            [_ grp]))))
-            (struct-copy quad page [elems lns-and-containers])))
+    (define lns (quad-elems page))             
+    (define groups (contiguous-group-by (λ (x) (hash-ref (quad-attrs x) 'container #f)) lns))
+    (define lns-and-containers (append* (for/list ([grp (in-list groups)])
+                                          (match (hash-ref (quad-attrs (car grp)) 'container #f)
+                                            ["bq" (list (make-blockquote grp))]
+                                            [_ grp]))))
+    (struct-copy quad page [elems lns-and-containers])))
 
 (define (run xs path)
   (define pdf (time-name make-pdf (make-pdf #:compress #t
diff --git a/quad/quad/atomize.rkt b/quad/quad/atomize.rkt
index 1bfc0884..27d1b02a 100644
--- a/quad/quad/atomize.rkt
+++ b/quad/quad/atomize.rkt
@@ -74,7 +74,7 @@
                      ;; also, they will not have any run keys embedded
                      ;; (but they shouldn't need it because they're not part of text runs)
                      ;; overall I am persuaded that `atomize` is very texty and needs a name befitting that role.
-                     (list (make-quad #:attrs next-attrs #:elems (list elem)))]
+                     (list ((quad-copier x) x next-attrs (list elem)))]
                     [_ (loop elem next-attrs next-key)])))]
       [_ (list x)])))
 
diff --git a/quad/quad/quad.rkt b/quad/quad/quad.rkt
index 379e28f8..8b55bfdf 100644
--- a/quad/quad/quad.rkt
+++ b/quad/quad/quad.rkt
@@ -35,6 +35,7 @@
    (hashes-equal? (quad-attrs q1) (quad-attrs q2))))
 
 (struct quad (type
+              copier
               attrs
               elems
               size
@@ -72,6 +73,9 @@
 ;; todo: convert immutable hashes to mutable on input?
 (define (make-quad
          #:type [type quad]
+         #:copier [copier (λ (x as es) (struct-copy quad x
+                                                    [attrs as]
+                                                    [elems es]))]
          #:attrs [attrs (make-hasheq)]
          #:elems [elems null]
          #:size [size '(0 0)]
@@ -94,6 +98,7 @@
     [(list elems ..1) (make-quad #:elems elems)]
     ;; all cases end up below
     [null (type type
+                copier
                 attrs
                 elems
                 size