typesetting/quad/quadwriter/layout.rkt

#lang debug racket/base
(require racket/promise
         racket/match
         racket/list
         sugar/list
         txexpr/base
         racket/date
         pitfall
         quad
         racket/unsafe/ops
         hyphenate
         "attrs.rkt"
         "param.rkt"
         "font.rkt")
(provide (all-defined-out))


(define-quad string-quad quad ())
 
(define (q:string-draw q doc)
  ;; draw with pdf text routine
  (when (pair? (quad-elems q))
    (font doc (path->string (quad-ref q font-path-key default-font-face)))
    (font-size doc (quad-ref q :font-size default-font-size))
    (fill-color doc (quad-ref q :font-color default-font-color))
    (define str (unsafe-car (quad-elems q)))
    (match-define (list x y) (quad-origin q))
    (text doc str x y
          #:tracking (quad-ref q :character-tracking 0)
          #:bg (quad-ref q :bg)
          #:features '((#"tnum" . 1))
          #:link (quad-ref q :link))))

(define (q:string-draw-end q doc)
  (when (draw-debug-string?)
    (draw-debug q doc "#99f" "#ccf")))

(define (q:string-printable? q [sig #f])
  ;; printable unless single space, which is not printable at start or end
  (match (quad-elems q)
    [(cons elem _)
     (case elem
       [(" " #\space) (not (memq sig '(start end)))]
       [else #true])]
    [_ #true]))

(define q:string (q #:type string-quad
                    #:from 'bo
                    #:to 'bi
                    #:id 'str
                    #:printable q:string-printable?
                    #:draw q:string-draw
                    #:draw-end q:string-draw-end))

(define (make-size-promise q [str-arg #f])
  (delay
    (define pdf (current-pdf))
    (define str
      (cond
        [str-arg]
        [(pair? (quad-elems q)) (unsafe-car (quad-elems q))]
        [else #false]))
    (define string-size
      (cond
        [str
         (font-size pdf (quad-ref q :font-size default-font-size))
         (font pdf (path->string (quad-ref q font-path-key default-font-face)))
         (+ (string-width pdf str
                          #:tracking (quad-ref q :character-tracking 0))
            ;; add one more dose because `string-width` only adds it intercharacter,
            ;; and this quad will be adjacent to another
            ;; (so we need to account for the "inter-quad" space
            (quad-ref q :character-tracking 0))]
        [else 0]))
    (list string-size (quad-ref q :line-height (current-line-height pdf)))))

(define (->string-quad q)
  (cond
    [(q:line-break? q) q]
    [else
     (struct-copy
      quad q:string
      [attrs (let ([attrs (quad-attrs q)])
               (hash-ref! attrs :font-size default-font-size)
               attrs)]
      [elems (quad-elems q)]
      [size (make-size-promise q)])]))


(define (draw-debug q doc [fill-color "#f99"] [stroke-color "#fcc"] [stroke-width 0.5])
  ;; ostensibly it would be possible to control draw-debug with a quad attribute
  ;; but that would potentially mess up unit tests (because something has to be inserted in the data)
  ;; therefore controlling debug state with a parameter is cleaner.
  (when (draw-debug?)
    (save doc)
    ;; draw layout box
    (line-width doc stroke-width)
    ; subtracting stroke-width keeps adjacent boxes from overlapping
    (save doc)
    (apply rect doc (append (pt+ (quad-origin q)) (map (λ (x) (- x 0.5)) (size q))))
    (clip doc)
    (define pt (to-point q))
    (circle doc (pt-x pt) (pt-y pt) (+ 3 stroke-width))
    (fill doc fill-color)
    (restore doc)
    (apply rect doc (append (pt+ (quad-origin q)) (map (λ (x) (- x 0.5)) (size q))))
    (stroke doc stroke-color)
    (restore doc)))


(define-quad q:line-break quad ())
(define lbr (make-q:line-break #:printable #f
                               #:id 'lbr))
;; treat paragraph break as special kind of line break
(define-quad q:para-break q:line-break ())
(define pbr (make-q:para-break #:printable #f
                               #:id 'pbr))
(define-quad q:hr-break q:line-break ())
(define hrbr (make-q:hr-break #:printable #t
                              #:id 'hrbr))

(define-quad q:col-break q:line-break ())
(define colbr (make-q:col-break #:printable #f #:id 'colbr))

(define-quad q:page-break q:line-break ())
(define pgbr (make-q:page-break #:printable #f #:id 'pgbr))

(define q:line (q #:size (pt 0 default-line-height)
                  #:from 'sw
                  #:to 'nw
                  #:printable #true
                  #:id 'line
                  #:draw-start (if draw-debug-line? draw-debug void)))

(struct line-spacer q:line-break () #:transparent)
(define q:line-spacer (q #:type line-spacer
                         #:size (pt 20 (* default-line-height 0.6))
                         #:from 'sw
                         #:to 'nw
                         #:printable (λ (q sig) (not (memq sig '(start end))))
                         #:draw-start (if (draw-debug-line?) draw-debug void)))

(define softies (map string '(#\space #\- #\u00AD)))

(define (soft-break-for-line? q)
  (and (pair? (quad-elems q))
       (member (unsafe-car (quad-elems q)) softies)))

(define (consolidate-runs pcs ending-q)
  (let loop ([runs empty][pcs pcs])
    (match pcs
      [(? empty?) (reverse runs)]
      [(cons (? string-quad? strq) rest)
       (define-values (run-pcs rest) (splitf-at pcs (λ (p) (same-run? strq p))))
       (define new-run (struct-copy quad q:string
                                    [attrs (quad-attrs strq)]
                                    [elems (merge-adjacent-strings (apply append (for/list ([pc (in-list run-pcs)])
                                                                                   (quad-elems pc))))]
                                    [size (delay (pt (for/sum ([pc (in-list run-pcs)])
                                                       (pt-x (size pc)))
                                                     (pt-y (size strq))))]))
       (loop (cons new-run runs) rest)]
      [(cons first rest) (loop (cons first runs) rest)])))

(define (render-hyphen qs ending-q)
  ;; naive handling of soft hyphen:
  ;; if soft hyphen cause the break, then append a printing hyphen to the end of the run.
  ;; this assumes that there is room for the hyphen on the line
  ;; and does not take into account hyphen-break transformations found in other languages.
  ;; However we do want the hyphen joined into the string so the final shaping / positioning is correct
  ;; for instance, kerning between last letter and hyphen.
  (match (and ending-q (equal? (quad-elems ending-q) '("\u00AD")) qs)
    [(list head ... last-q)
     (define str (car (quad-elems last-q)))
     (define str+hyphen (string-append str "-"))
     (append head
             (list (struct-copy quad last-q
                                [elems (list str+hyphen)]
                                [size (make-size-promise last-q str+hyphen)])))]
    [_ qs]))


(module+ test
  (require rackunit)
  (check-true (q:line-break? (second (quad-elems (q "foo" pbr "bar")))))
  (check-true (q:line-break? (second (atomize (q "foo" pbr "bar"))))))

(define (handle-hyphenate qs)
  ;; find quads that want hyphenation and split them into smaller pieces
  ;; do this before ->string-quad so that it can handle the sizing promises
  (apply append
         (for/list ([q (in-list qs)])
           (match (quad-ref q :hyphenate)
             [(or #false "false") (list q)]
             [_ (for*/list ([str (in-list (quad-elems q))]
                            [hyphen-char (in-value #\u00AD)]
                            [hstr (in-value (hyphenate str hyphen-char
                                                       #:min-left-length 3
                                                       #:min-right-length 3))]
                            [substr (in-list (regexp-match* (regexp (string hyphen-char)) hstr #:gap-select? #t))])
                  (struct-copy quad q [elems (list substr)]))]))))

(define-quad filler quad ())

(define (sum-of-widths qss)
  (for*/sum ([qs (in-list qss)]
             [q (in-list qs)])
    (pt-x (size q))))

(define (space-quad? q) (equal? (quad-elems q) (list " ")))

(define (fill-wrap qs ending-q line-q)
  (match (and (pair? qs) (quad-ref (car qs) (if ending-q
                                                :line-align
                                                :line-align-last) "left"))
    [align-value
     ;; words may still be in hyphenated fragments
     ;; (though soft hyphens would have been removed)
     ;; so group them (but no need to consolidate — that happens elsewhere)
     (define-values (word-space-sublists word-sublists) (partition* space-quad? qs))
     (match (length word-sublists)
       [1 #:when (equal? align-value "justify") qs] ; can't justify single word
       [word-count
        (match-define (list line-width line-height) (quad-size line-q))
        (define hung-word-sublists
          (match word-sublists
            [(list sublists ... (list prev-qs ... last-q))
             (define last-char-str (regexp-match #rx"[.,:;’-]$" (car (quad-elems last-q))))
             (match last-char-str
               [#false word-sublists]
               [_ (define hanger-q (struct-copy quad last-q
                                                [elems null]
                                                [size (let ([p (make-size-promise last-q (car last-char-str))])
                                                        (delay
                                                          (match-define (list x y) (force p))
                                                          (pt (- x) y)))]))
                  (define last-sublist (append prev-qs (list last-q hanger-q)))
                  (append sublists (list last-sublist))])]))
        (define word-width (sum-of-widths hung-word-sublists))
        (define word-space-width (sum-of-widths word-space-sublists))
        (define empty-hspace (- line-width
                                (quad-ref (car qs) :inset-left 0)
                                word-width
                                (quad-ref (car qs) :inset-right 0)))
        (define line-overfull? (negative? (- empty-hspace word-space-width)))

        (cond
          [(or (equal? align-value "justify")
               ;; force justification upon overfull lines
               (and line-overfull? (> word-count 1)))
           (define justified-space-width (/ empty-hspace (sub1 word-count)))
           (apply append (add-between hung-word-sublists (list (make-quad
                                                                #:from 'bo
                                                                #:to 'bi
                                                                #:draw-end q:string-draw-end
                                                                #:size (pt justified-space-width line-height)))))]
          
          [(equal? align-value "left") qs] ; no filling needed 
          [else
           (define space-multiplier (match align-value
                                      ["center" 0.5]
                                      ["right" 1]))
           ;; subtact space-width because that appears between words
           ;; we only care about redistributing the space on the ends
           (define end-hspace (- empty-hspace word-space-width))
           ; make filler a leading quad, not a parent / grouping quad,
           ;; so that elements can still be reached by consolidate-runs
           (list* (make-quad #:type filler
                             #:from-parent (quad-from-parent (car qs))
                             #:from 'bo
                             #:to 'bi
                             #:size (pt (* end-hspace space-multiplier) 0)
                             #:attrs (quad-attrs (car qs)))
                  (struct-copy quad (car qs) [from-parent #f])
                  (cdr qs))])])]))

(define-quad offsetter quad ())

(define (hr-draw dq doc)
  (match-define (list left top) (quad-origin dq))
  (match-define (list right bottom) (size dq))
  (save doc)
  (translate doc left (+ top (/ bottom 2)))
  (move-to doc 0 0)
  (line-to doc right 0)
  (line-width doc 0.5)
  (stroke doc "black")
  (restore doc))

(define (make-hr-quad line-q)
  (struct-copy quad line-q [draw-start hr-draw]))

(define bullet-quad '(q ((special "bullet"))))

(define ((finish-line-wrap line-q) pcs-in opening-q ending-q idx)
  ;; we curry line-q so that the wrap size can be communicated to this operation
  ;; remove unused soft hyphens so they don't affect final shaping
  (define pcs-printing (for/list ([pc (in-list pcs-in)]
                                  #:unless (equal? (quad-elems pc) '("\u00AD")))
                         pc))
  (define new-lines
    (cond
      [(empty? pcs-printing) null]
      [(q:hr-break? ending-q) (list (make-hr-quad line-q))]
      [else
       ;; render hyphen first so that all printable characters are available for size-dependent ops.
       (define pcs-with-hyphen (render-hyphen pcs-printing ending-q))
       ;; fill wrap so that consolidate-runs works properly
       ;; (justified lines won't be totally consolidated)
       (define pcs (fill-wrap pcs-with-hyphen ending-q line-q))
       (match (consolidate-runs pcs ending-q)
         [(? pair? elems)
          (define elem (unsafe-car elems))
          (match-define (list line-width line-height) (quad-size line-q))
          (define new-size (let ()
                             (define line-heights
                               (filter-map (λ (q) (quad-ref q :line-height)) pcs))
                             (pt line-width (if (empty? line-heights) line-height (apply max line-heights)))))
          (list
           (struct-copy
            quad line-q
            ;; move block attrs up, so they are visible in col wrap
            [attrs (copy-block-attrs (quad-attrs elem)
                                     (hash-copy (quad-attrs line-q)))]
            ;; line width is static
            ;; line height is the max 'line-height value or the natural height of q:line
            [size new-size]
            ;; handle list indexes. drop new quad into line to hold list index
            ;; could also use this for line numbers
            [elems
             ;; we assume here that a list item has already had extra inset-left
             ;; with room for a bullet
             ;; which we just insert at the front.
             ;; this is safe because line has already been filled.
             (append
              ;; only put bullet into line if we're at the first line of the list item
              (match (and (eq? idx 1) (quad-ref elem :list-index))
                [#false null]
                [bullet
                 (define bq (struct-copy
                             quad q:string ;; copy q:string to get draw routine
                             ;; borrow attrs from elem
                             [attrs (quad-attrs elem)]
                             ;; use bullet as elems
                             [elems (list (if (number? bullet) (format "~a." bullet) bullet))]
                             ;; size doesn't matter because nothing refers to this quad
                             ;; just for debugging box
                             [size (pt 15 (pt-y (size line-q)))]))
                 (from-parent (list bq) 'sw)])
              (from-parent
               (match (quad-ref elem :inset-left 0)
                 [0 elems]
                 [inset-val
                  (cons (make-quad
                         #:draw-end q:string-draw-end
                         #:to 'sw
                         #:size (pt inset-val 5)
                         #:type offsetter)
                        elems)]) 'sw))]))]
         [_ null])]))
  (append new-lines (cond
                      [(q:page-break? ending-q) (list ending-q)] ; hard page break
                      [ending-q null] ; hard line break
                      [else (list (struct-copy quad q:line-spacer
                                               [attrs (hash-copy (quad-attrs q:line-spacer))]))]))) ; paragraph break

(define (line-wrap qs wrap-size)
  (match qs
    [(? pair?)
     (unless (positive? wrap-size)
       (raise-argument-error 'line-wrap "positive number" wrap-size))
     (define line-q (struct-copy
                     quad q:line
                     [size (pt wrap-size (pt-y (size q:line)))]))
     (define justify-factor (match (quad-ref (car qs) :line-align #f)
                              ;; allow justified lines to go wider,
                              ;; and then fill-wrap will tighten the word spaces
                              ;; this makes justified paragraphs more even, becuase
                              ;; some lines are a little tight, as opposed to all of them being loose
                              ["justify" 1.04]
                              [_ 1]))
     (apply append
            ;; next line removes all para-break? quads as a consequence
            (for/list ([qs (in-list (filter-split qs q:para-break?))])
              (wrap qs
                    (λ (q idx) (* (- wrap-size
                                     (quad-ref (car qs) :inset-left 0)
                                     (quad-ref (car qs) :inset-right 0))
                                  justify-factor))
                    #:nicely (match (or (current-line-wrap) (quad-ref (car qs) 'line-wrap))
                               [(or "best" "kp") #true]
                               [_ #false])
                    #:hard-break q:line-break?
                    #:soft-break soft-break-for-line?
                    #:finish-wrap (finish-line-wrap line-q))))]
    [_ null]))

(define (make-nobreak! q) (quad-set! q :no-colbr "true")) ; cooperates with col-wrap

(define (do-keep-with-next! reversed-lines)
  ;; paints nobreak onto spacers that follow keep-with-next lines
  ;; (we are iterating backward, so the geometrically previous ln follows the spacer)
  (cond
    [(null? reversed-lines) null]
    [else
     (for ([this-ln (in-list reversed-lines)]
           [prev-ln (in-list (cdr reversed-lines))]
           #:when (and (line-spacer? this-ln)
                       (quad-ref prev-ln :keep-with-next)))
       (make-nobreak! this-ln)
       (make-nobreak! prev-ln))]))

(define (apply-keeps lines)
  (define groups-of-lines (contiguous-group-by (λ (x) (quad-ref x :display)) lines))
  (for*/fold ([reversed-lines null]
              #:result (begin
                         (do-keep-with-next! reversed-lines)
                         (reverse reversed-lines)))
             ([group (in-list groups-of-lines)]
              [group-len (in-value (length group))]
              [(ln idx0) (in-indexed group)])
    (define idx (add1 idx0))
    ;; always catch last line of block in this case
    ;; so later cases are guaranteed to have earlier lines.
    (unless (eq? idx group-len)
      (cond
        ;; if we have :keep-all we can skip :keep-first and :keep-last cases
        [(quad-ref ln :keep-all-lines) (make-nobreak! ln)]
        ;; to keep n lines, we only paint the first n - 1
        ;; (because each nobr line sticks to the next)
        [(let ([keep-first (quad-ref ln :keep-first-lines)])
           (and (number? keep-first) (< idx keep-first)))
         (make-nobreak! ln)]
        [(let ([keep-last (quad-ref ln :keep-last-lines)])
           (and (number? keep-last) (< (- group-len keep-last) idx)))
         (make-nobreak! ln)]))
    (cons ln reversed-lines)))

(define zoom-mode? #f)
(define zoom-scale 2)

(define (page-draw-start q doc)
  (add-page doc)
  (scale doc (zoom-factor) (zoom-factor))
  (draw-debug q doc "aliceblue" "aliceblue" 3))

(define (draw-page-footer q doc)
  (match-define (list x y) (quad-origin q))
  (font-size doc (* .8 default-font-size))
  (font doc default-font-face)
  (fill-color doc default-font-color)
  (text doc (format "~a · ~a at ~a" (quad-ref q :page-number 0)
                    (quad-ref q :doc-title "untitled")
                    (date->string (current-date) #t))
        x y))

(define q:footer (q #:size (pt 50 default-line-height)
                    #:from-parent 'sw
                    #:to 'nw
                    #:shift (pt 0 (* 1.5 default-line-height))
                    #:printable #true
                    #:draw-start (λ (q doc)
                                   (when draw-debug-line?
                                     (draw-debug q doc "goldenrod" "goldenrod"))
                                   (unless (quadwriter-test-mode)
                                     (draw-page-footer q doc)))))

(define q:column (q
                  #:id 'col
                  #:from 'ne
                  #:to 'nw))

(struct column-spacer quad () #:transparent)
(define q:column-spacer (q #:type column-spacer
                           #:from 'ne
                           #:to 'nw
                           #:printable (λ (q sig) (not (memq sig '(start end))))))

(define q:page (q
                #:id 'page
                #:from-parent 'nw
                #:draw-start page-draw-start))

(define q:doc (q #:draw-start (λ (q doc) (start-doc doc))
                 #:draw-end (λ (q doc) (end-doc doc))))

(define ((block-draw-start first-line) q doc)
  ;; adjust drawing coordinates for border inset
  (match-define (list bil bit bir bib)
    (for/list ([k (in-list (list :border-inset-left :border-inset-top :border-inset-right :border-inset-bottom))])
      (quad-ref first-line k 0)))
  (match-define (list left top) (pt+ (quad-origin q) (list bil bit)))
  (match-define (list width height) (pt- (size q) (list (+ bil bir) (+ bit bib))))
  ;; fill rect
  (cond 
    [(quad-ref first-line :background-color)
     => (λ (bgcolor)
          (rect doc left top width height)
          (fill doc bgcolor))])
  ;; draw border
  (match-define (list bw-left bw-top bw-right bw-bottom)
    (map (λ (k) (max 0 (quad-ref first-line k 0))) (list
                                                    :border-width-left
                                                    :border-width-top
                                                    :border-width-right
                                                    :border-width-bottom)))
  ;; adjust start and end points based on adjacent border width
  ;; so all borders overlap rectangularly
  (define (half x) (/ x 2.0))
  (define right (+ left width))
  (define bottom (+ top height))
  (define (box-side x1 y1 x2 y2 color stroke-width)
    (when (positive? stroke-width)
      (move-to doc x1 y1)
      (line-to doc x2 y2)
      (stroke doc (or color "black") stroke-width)))
  (box-side (- left (half bw-left)) top (+ right (half bw-right)) top
            (quad-ref first-line :border-color-top) bw-top)
  (box-side right (- top (half bw-top)) right (+ bottom (half bw-bottom))
            (quad-ref first-line :border-color-right) bw-right)
  (box-side (+ right (half bw-right)) bottom (- left (half bw-left)) bottom
            (quad-ref first-line :border-color-bottom) bw-bottom)
  (box-side left (+ bottom (half bw-bottom)) left (- top (half bw-top))
            (quad-ref first-line :border-color-left) bw-left)
  (case (quad-ref first-line :block-clip #false)
    [(#true "true")
     (save doc)
     (rect doc left top width height)
     (clip doc)]))

(define ((block-draw-end first-line) q doc)
  (case (quad-ref first-line :block-clip #false)
    [(#true "true") (restore doc)])
  (when (draw-debug-block?)
    (draw-debug q doc "#6c6" "#9c9")))

(define (block-wrap lines)
  (define first-line (car lines)) 
  (q #:from 'sw
     #:to 'nw
     #:elems (from-parent lines 'nw)
     #:id 'block
     #:attrs (quad-attrs first-line)
     #:size (delay (pt (pt-x (size first-line)) ; 
                       (+ (for/sum ([line (in-list lines)])
                            (pt-y (size line)))
                          (quad-ref first-line :inset-top 0)
                          (quad-ref first-line :inset-bottom 0))))
     #:shift-elems (pt 0 (+ (quad-ref first-line :inset-top 0)))
     #:draw-start (block-draw-start first-line)
     #:draw-end (block-draw-end first-line)))

(define/match (from-parent qs [where #f])
  ;; doesn't change any positioning. doesn't depend on state. can happen anytime.
  ;; can be repeated without damage.
  [((? null?) _) null]
  [((cons q rest) where)
   (cons (struct-copy quad q
                      [from-parent (or where (quad-from q))]) rest)])


(define ((col-finish-wrap col-quad) lns . _)
  (list (struct-copy quad col-quad
                     ;; move block attrs up, so they are visible in page wrap
                     [attrs (copy-block-attrs (quad-attrs (car lns))
                                              (hash-copy (quad-attrs col-quad)))]
                     [elems (from-parent (insert-blocks lns) 'nw)])))

(define (col-wrap qs vertical-height col-gap [col-quad q:column])
  (unless (positive? vertical-height)
    (raise-argument-error 'col-wrap "positive number" vertical-height))
  
  ;; on timing of `insert-blocks`:
  ;; can't do it before because it depends on where columns are broken.
  ;; could do it after, but it would require going back inside each col quad
  ;; which seems overly interdependent, because `insert-blocks` is used to determine break locations.
  ;; `col-wrap` should emit quads that are complete.
  (define col-spacer (struct-copy quad q:column-spacer
                                  [size (pt col-gap 100)]))
  (add-between
   (wrap qs vertical-height
         #:soft-break (λ (q) #true)
         #:hard-break q:col-break?
         #:no-break (λ (q) (quad-ref q :no-colbr)) ; cooperates with make-nobreak
         #:distance (λ (q dist-so-far wrap-qs)
                      ;; do trial block insertions
                      (for/sum ([x (in-list (insert-blocks wrap-qs))])
                        (pt-y (size x))))                     
         #:finish-wrap (col-finish-wrap col-quad))
   col-spacer))

(define ((page-finish-wrap page-quad path) cols q0 q page-idx)
  (define elems
    (match (quad-ref (car cols) :footer-display "true")
      [(or "false" "none") (from-parent cols 'nw)]
      [_
       (define-values (dir name _) (split-path (path-replace-extension path #"")))
       (define footer (struct-copy quad q:footer
                                   [attrs (let ([h (hash-copy (quad-attrs q:footer))])
                                            (hash-set! h :page-number page-idx)
                                            (hash-set! h :doc-title (string-titlecase (path->string name)))
                                            h)]))
       (cons footer (from-parent cols 'nw))]))
  (list (struct-copy quad page-quad [elems elems])))

(define (page-wrap qs width [page-quad q:page])
  (unless (positive? width)
    (raise-argument-error 'page-wrap "positive number" width))
  (wrap qs width
        #:soft-break (λ (q) #true)
        #:hard-break q:page-break?
        #:no-break (λ (q) (quad-ref q :no-pbr))
        #:distance (λ (q dist-so-far wrap-qs)
                     (for/sum ([x (in-list wrap-qs)])
                       (pt-x (size x))))
        #:finish-wrap (page-finish-wrap page-quad (pdf-output-path (current-pdf)))))



(define (insert-blocks lines)
  (define groups-of-lines (contiguous-group-by (λ (x) (quad-ref x :display)) lines))
  (append* (for/list ([line-group (in-list groups-of-lines)])
             (if (quad-ref (car line-group) :display)
                 (list (block-wrap line-group))
                 line-group))))

(define (handle-cascading-attrs attrs)
  (resolve-font-path attrs)
  (resolve-font-size attrs))

(define-quad first-line-indent quad ())

(define (insert-first-line-indents qs-in)
  ;; first line indents are quads inserted at the beginning of a paragraph
  ;; (that is, just after a paragraph break)
  ;; they need to be installed before line wrap
  ;; to be compatible with first-fit and best-fit.

  ;; stick a pbr on the front if there isn't one already
  ;; because of the "lookahead" style of iteration
  (define qs (match qs-in
               [(list (? q:para-break?) _ ...) qs-in]
               [_ (cons pbr qs-in)]))
  (for/fold ([qs-out null]
             #:result (reverse qs-out))
            ([q (in-list qs)]
             [next-q (in-list (cdr qs))])
    (match (and (q:para-break? q) (quad-ref next-q :first-line-indent 0))
      [(or #false 0) (cons next-q qs-out)]
      [indent-val (list* next-q (make-quad #:from 'bo
                                           #:to 'bi
                                           #:draw-end q:string-draw-end
                                           #:type first-line-indent
                                           #:attrs (quad-attrs next-q)
                                           #:size (pt indent-val 10)) qs-out)])))