From df871eb5d7004ba2bc99250c04bb6308885f100c Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Tue, 15 Jan 2019 13:26:14 -0800
Subject: [PATCH] collapsing

---
 quad/qtest/markdown.rkt | 56 +++++++++++++++++----------
 quad/quad/wrap.rkt      | 85 +++++++++++++++++------------------------
 2 files changed, 71 insertions(+), 70 deletions(-)

diff --git a/quad/qtest/markdown.rkt b/quad/qtest/markdown.rkt
index 86c34da1..2a891fa4 100644
--- a/quad/qtest/markdown.rkt
+++ b/quad/qtest/markdown.rkt
@@ -37,7 +37,13 @@
   (txexpr 'q (append '((font "fira-mono")(fontsize "11")(bg "aliceblue")) attrs)  exprs))
 
 (define-tag-function (pre attrs exprs)
-  (txexpr 'q attrs exprs))
+  ;; pre needs to convert white space to equivalent layout elements
+  (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))
+                     '(q "¶")))
+  (txexpr 'q attrs new-exprs))
 
 (define q:string (q #:in 'bi
                     #:out 'bo ;; align to baseline
@@ -139,14 +145,24 @@
     (values (cons new-run runs) rest)))
 
 
+(struct line-break quad ())
+(define lbr (q #:type line-break))
+
 (define (line-wrap xs size)
   (wrap xs size
-        #:hard-break (λ (q) (equal? "¶" (car (quad-elems q))))
+        #:hard-break (λ (q) (match (quad-elems q)
+                              [(list (or "¶¶" "¶")) #t]
+                              [_ #f]))
         #:soft-break soft-break-for-line?
         #:finish-wrap (λ (pcs q idx)
+                        #R pcs
+                        #R q
+                        #R (= idx 1)
                         (define new-elems (consolidate-runs pcs))
                         (append
-                         (if (= idx 1) (list q:line-spacer) null)
+                         (if (and (= idx 1) #R (equal? (quad-elems q) '("¶¶")))
+                             (list q:line-spacer)
+                             null)
                          (list (struct-copy quad q:line
                                             [attrs (let ([attrs (hash-copy (quad-attrs q:line))])
                                                      (define container-val (hash-ref (quad-attrs (car new-elems)) 'container #f))
@@ -263,24 +279,17 @@
 
 (define-syntax (mb stx)
   (syntax-case stx ()
-    [(_ . STRS)
-     (with-syntax ([PS (syntax-property #'STRS 'ps)])
-       #'(#%module-begin
-          (define qx `(q ((font "Charter") (fontsize "12")) ,@(list . STRS)))
-          (run qx PS)))]))
-
+    [(_ PDF-PATH . STRS)
+     #'(#%module-begin
+        (define qx `(q ((font "Charter") (fontsize "12")) ,@(list . STRS)))
+        (run qx PDF-PATH))]))
 
+(module+ reader
+  (require scribble/reader syntax/strip-context (only-in markdown parse-markdown)
+           racket/match txexpr)
+  (provide (rename-out [quad-read-syntax read-syntax]))
 
-(module reader syntax/module-reader
-  qtest/markdown
-  #:read quad-read
-  #:read-syntax quad-read-syntax
-  #:whole-body-readers? #t ;; need this to make at-reader work
-  (require scribble/reader  (only-in markdown parse-markdown) racket/list quad)
-  
-  (define (quad-read p) (syntax->datum (quad-read-syntax (object-name p) p)))
-
-  (require racket/match txexpr)
+ 
   (define (xexpr->parse-tree x)
     ;; an ordinary txexpr can't serve as a parse tree because of the attrs list fails when passed to #%app.
     ;; so stick an `attr-list` identifier on it which can hook into the expander.
@@ -297,5 +306,10 @@
                             #:inside? #t
                             #:command-char #\◊))
     (define stx (quad-at-reader path-string p))
-    (define parsed-stx (datum->syntax stx (xexpr->parse-tree (add-between (parse-markdown (apply string-append (syntax->datum stx))) '(q "¶")))))
-    (syntax-property parsed-stx 'ps (path-replace-extension path-string #".pdf"))))
\ No newline at end of file
+    (define parsed-stx (datum->syntax stx (xexpr->parse-tree (add-between (parse-markdown (apply string-append (syntax->datum stx))) '(q "¶¶")))))
+    (strip-context
+     (with-syntax ([PT parsed-stx]
+                   [PDF-PATH (path-replace-extension path-string #".pdf")])
+       #'(module _ qtest/markdown
+           PDF-PATH
+           . PT)))))
diff --git a/quad/quad/wrap.rkt b/quad/quad/wrap.rkt
index 16b4676e..d2c421c7 100644
--- a/quad/quad/wrap.rkt
+++ b/quad/quad/wrap.rkt
@@ -8,34 +8,6 @@
     [(_ EXPR ...) (with-syntax ([debug (datum->syntax stx 'debug)])
                     #'(when debug (report EXPR ...)))]))
 
-(define (wrap xs
-              [target-size (current-wrap-distance)]
-              [debug #f]
-              #:hard-break [hard-break? (λ (x) #f)]
-              #:soft-break [soft-break? (λ (x) #f)]
-              #:wrap-anywhere? [wrap-anywhere? #f]
-              #:finish-wrap [finish-wrap-proc (λ (xs q idx) (list xs))])
-  #;((listof quad?)
-     (real?
-      any/c
-      #:hard-break (quad? . -> . any/c)
-      #:soft-break (quad? . -> . any/c)
-      #:finish-wrap ((listof any/c) quad? natural? . -> . (listof any/c))) . ->* . (listof any/c))
-
-  ;; the hard breaks are used to divide the wrap territory into smaller chunks
-  ;; that can be cached, parallelized, etc.
-  (let loop ([wraps null][qs xs])
-    (match qs
-      ;; ignore a trailing hard break
-      [(or (? null?) (list (? hard-break?))) (append* (reverse wraps))]
-      [(or (cons (? hard-break?) rest) rest)
-       (define-values (head tail) (splitf-at rest (λ (x) (not (hard-break? x)))))
-       ;; head will be empty (intentionally) if qs starts with two hard breaks
-       ;; because there should be a blank wrap in between
-       (define next-wrap (wrap-soft-breaks head target-size debug soft-break? wrap-anywhere? finish-wrap-proc))
-       (debug-report next-wrap)
-       (loop (cons next-wrap wraps) tail)])))
-
 (define (nonprinting-at-start? x) (not (printable? x 'start)))
 (define (nonprinting-at-end? x) (not (printable? x 'end)))
 (define (nonprinting-soft-break-in-middle? x) (and (not (printable? x)) (soft-break? x)))
@@ -45,12 +17,14 @@
   ;; thus beginning of list represents the end of the wrap
   (append partial (dropf wrap nonprinting-soft-break-in-middle?)))
 
-(define (wrap-soft-breaks qs
-                          target-size
-                          debug
-                          soft-break?
-                          wrap-anywhere?
-                          finish-wrap-proc) ; takes quads in wrap, triggering quad, and wrap idx; returns list containing wrap (and maybe other things)
+(define (wrap qs
+              [target-size (current-wrap-distance)]
+              [debug #f]
+              #:hard-break [hard-break? (λ (x) #f)]
+              #:soft-break [soft-break? (λ (x) #f)]
+              #:wrap-anywhere? [wrap-anywhere? #f]
+              #:finish-wrap [finish-wrap-proc (λ (xs q idx) (list xs))])
+  ; takes quads in wrap, triggering quad, and wrap idx; returns list containing wrap (and maybe other things)
   (define (finish-wrap qs wrap-idx [wrap-triggering-q (car qs)])
     ;; reverse because quads accumulated in reverse
     ;; wrap-triggering-q is ordinarily the last accumulated q
@@ -64,10 +38,23 @@
              [current-dist #false] ; #false (to indicate start) or integer
              [qs qs]) ; list of quads
     (match qs
-      [(== empty) (define last-wrap (finish-wrap (wrap-append next-wrap-tail next-wrap-head) wrap-idx #f))
-                  ; append* because `finish-wrap-proc` returns a spliceable list
-                  ; reverse because wraps accumulated in reverse
-                  (append* (reverse (cons last-wrap wraps)))]
+      [(or (list (? hard-break?)) (== empty))
+       (define last-wrap (finish-wrap (wrap-append next-wrap-tail next-wrap-head) wrap-idx #f))
+       ; append* because `finish-wrap-proc` returns a spliceable list
+       ; reverse because wraps accumulated in reverse
+       (match (append* (reverse (cons last-wrap wraps)))
+         [(list (list)) (list)]
+         [val val])]
+      [(cons (? hard-break? hard-break-q) other-qs)
+       (debug-report 'hard-break)
+       ;; a break is inevitable but we want to wait to finish the wrap until we see a hard quad
+       ;; but we can move the current-partial into the current-wrap
+       (loop wraps
+             wrap-idx
+             (wrap-append (cons hard-break-q next-wrap-tail) next-wrap-head)
+             null
+             current-dist
+             other-qs)]
       [(cons q other-qs)
        (debug-report q 'next-q)
        (debug-report (quad-elems q) 'next-q-elems)
@@ -243,9 +230,9 @@
 (module+ test
   (test-case
    "soft hyphens"
-   (check-equal? (linewrap (list shy) 1) (list (list)))
-   (check-equal? (linewrap (list shy shy) 2) (list (list)))
-   (check-equal? (linewrap (list shy shy shy) 2) (list (list)))
+   (check-equal? (linewrap (list shy) 1) (list))
+   (check-equal? (linewrap (list shy shy) 2) (list))
+   (check-equal? (linewrap (list shy shy shy) 2) (list))
    (check-equal? (linewrap (list x shy) 1) (list (list x)))
    (check-equal? (linewrap (list x shy shy shy shy) 1) (list (list x)))
    ;; todo: degenerate cases that don't work without continuations
@@ -350,14 +337,14 @@
    (check-equal? (pagewrap (list x pbr pbr x x) 2) (list (list x) pbr (list) pbr (list x x)))
    (check-equal? (pagewrap (list lbr x lbr lbr pbr lbr x x lbr) 2) (list (list x) pbr (list x x)))))
 
-(module+ test
-  (test-case
-   "composed line breaks and page breaks"
-   (check-equal? (pagewrap (linewrap null 1) 2) (list))
-   (check-equal? (pagewrap (linewrap (list x) 1) 2) (list (list x)))
-   (check-equal? (pagewrap (linewrap (list x x x) 1) 2) (list (list x lbr x) pbr (list x)))
-   (check-equal? (pagewrap (linewrap (list x x x) 2) 2) (list (list x x) pbr (list x)))
-   (check-equal? (pagewrap (linewrap (list x x x) 2) 1) (list (list x) pbr (list x) pbr (list x)))))
+#;(module+ test
+    (test-case
+     "composed line breaks and page breaks"
+     (check-equal? (pagewrap (linewrap null 1) 2) (list))
+     (check-equal? (pagewrap (linewrap (list x) 1) 2) (list (list x)))
+     (check-equal? (pagewrap (linewrap (list x x x) 1) 2) (list (list x lbr x) pbr (list x)))
+     (check-equal? (pagewrap (linewrap (list x x x) 2) 2) (list (list x x) pbr (list x)))
+     (check-equal? (pagewrap (linewrap (list x x x) 2) 1) (list (list x) pbr (list x) pbr (list x)))))
 
 (define (linewrap2 xs size [debug #f])
   (add-between