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Matthew Butterick 6 years ago
parent 9d3e7913f1
commit c18e2c2b19
1 changed files with 38 additions and 38 deletions
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76
quad/quad/wrap.rkt
Unescape Escape View File

@ -15,7 +15,6 @@
[else 0]))
(define+provide/contract (wrap xs
[target-size (current-wrap-distance)]
[debug #f]
@ -76,6 +75,8 @@
(append (if break-before? (list break-val) empty) (cleanup-wraplist wraps) (if break-after? (list break-val) empty)))
(define (nonprinting-at-start? x) (if (quad? x) (not (printable? x 'start)) #t))
(define (nonprinting-at-end? x) (if (quad? x) (not (printable? x 'end)) #t))
(define (wrap-optionals xs
target-size
debug
@ -83,10 +84,10 @@
optional-break?
finish-wrap-proc)
(define start-signal (gensym))
(define (nonprinting-at-start? x) (if (quad? x) (not (printable? x 'start)) #t))
(define (nonprinting-at-end? x) (if (quad? x) (not (printable? x 'end)) #t))
(define last-optional-break-k #f)
(define (capture-optional-break-k!) (when debug (report 'capturing-break)) (let/cc k (set! last-optional-break-k k) #f))
(define (capture-optional-break-k!)
(when debug (report 'capturing-break))
(let/cc k (set! last-optional-break-k k) #f))
(call/prompt ;; continuation boundary for last-optional-break-k
(thunk
(let loop ([wraps null][wrap-pieces null][dist-so-far start-signal][xs xs])
@ -107,14 +108,7 @@
(define x (car xs))
(define at-start? (eq? dist-so-far start-signal))
(define underflow? (and (not at-start?) (<= (+ dist-so-far (if (and (quad? x) (printable? x 'end)) (distance x) 0)) target-size)))
(define (add-to-current-wrap)
(define printable (and (quad? x) (printable? x (and at-start? 'start))))
(define dist (and printable (distance x)))
(loop wraps
(if (and (quad? x) (not printable)) wrap-pieces (cons x wrap-pieces)) ; omit nonprinting quad
(if at-start? (or dist start-signal) (+ dist-so-far (or dist 0)))
(cdr xs)))
(define (insert-break [before? #f])
(define (values-for-insert-break [before? #f])
;; a break can be inserted before or after the current quad.
;; At an ordinary break (mandatory or optional) it goes after the wrap point.
;; The wrap signal consumes the break if it's nonprinting (e.g., word space or hard break)
@ -124,36 +118,38 @@
;; (we do this by resetting next-xs to the whole xs list)
;; In both cases, the `finish-wrap` proc will strip off any trailing white breaks from the new segment.
(set! last-optional-break-k #f) ;; prevents continuation loop
(define-values (pieces-for-this-wrap next-xs)
(if before?
(values wrap-pieces xs)
(values (if (and (quad? x) (nonprinting-at-end? x)) wrap-pieces (cons x wrap-pieces)) (cdr xs)))) ; omit nonprinting quad
(loop (list* (list break-val) pieces-for-this-wrap wraps)
null
start-signal
next-xs))
(define (skip) (loop wraps null dist-so-far (cdr xs)))
(if before?
(values wrap-pieces xs)
; omit nonprinting quad
(values (if (and (quad? x) (nonprinting-at-end? x)) wrap-pieces (cons x wrap-pieces)) (cdr xs))))
(cond
[(and at-start? (optional-break? x) (nonprinting-at-start? x))
(when debug (report x 'skipping-optional-break-at-beginning))
(skip)]
;; skip it
(loop wraps null dist-so-far (cdr xs))]
[(and underflow? (optional-break? x) (capture-optional-break-k!))
(when debug (report x 'resuming-break-from-continuation))
(insert-break)]
[underflow? ; the easy case of accumulating quads in the middle of a wrap
(when debug (report x 'add-underflow))
(add-to-current-wrap)]
[at-start? ;; assume printing (nonprinting were handled in first case)
;; this branch reached if the first quad on the line causes an overflow
;; That sounds weird, but maybe it's just really big.
(when debug (report x 'add-at-start))
(add-to-current-wrap)]
[(and (optional-break? x) (nonprinting-at-end? x))
;; we do want to accumulate nonprinting optional breaks (like wordspaces and soft hyphens) in the middle.
;; in case we eventually encounter a printing quad that fits on the line.
;; if we don't (ie. the line overflows) then they will get stripped by `finish-wrap`
(when debug (report x 'add-nonprinting-optional-break))
(add-to-current-wrap)]
(define-values (pieces-for-this-wrap next-xs) (values-for-insert-break))
(loop (list* (list break-val) pieces-for-this-wrap wraps)
null
start-signal
next-xs)]
;; the easy case of accumulating quads in the middle of a wrap
[(or (and underflow? (when debug (report x 'add-underflow)) #t)
;; assume printing (nonprinting were handled in first case)
;; this branch reached if the first quad on the line causes an overflow
;; That sounds weird, but maybe it's just really big.
(and at-start? (when debug (report x 'add-at-start)) #t)
;; we do want to accumulate nonprinting optional breaks (like wordspaces and soft hyphens) in the middle.
;; in case we eventually encounter a printing quad that fits on the line.
;; if we don't (ie. the line overflows) then they will get stripped by `finish-wrap`
(and (optional-break? x) (nonprinting-at-end? x) (when debug (report x 'add-nonprinting-optional-break)) #t))
(define printable (and (quad? x) (printable? x (and at-start? 'start))))
(define dist (and printable (distance x)))
(loop wraps
(if (and (quad? x) (not printable)) wrap-pieces (cons x wrap-pieces)) ; omit nonprinting quad
(if at-start? (or dist start-signal) (+ dist-so-far (or dist 0)))
(cdr xs))]
;; the previous branch will catch all `underflow?` cases
;; therefore, in these last two cases, we have overflow
[last-optional-break-k ;; overflow implied
@ -166,7 +162,11 @@
;; we insert the break `before` so that the current quad is moved to the next wrap
;; no, it's not going to look good, but if we reach this point, we are in weird conditions
(when debug (report x 'falling-back))
(insert-break 'before)])])))))
(define-values (pieces-for-this-wrap next-xs) (values-for-insert-break 'before))
(loop (list* (list break-val) pieces-for-this-wrap wraps)
null
start-signal
next-xs)])])))))
(define x (q (list 'size (pt 1 1)) #\x))

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