(use cairo data-structures srfi-13)

(define s (cairo-image-surface-create-from-png "gazette-chicken.png"))

(define c (cairo-create s))

(define text (string-append "\"" (string-upcase (second (argv))) "\""))

(define (text-width ctxt text)
  (let ((ex (make-cairo-text-extents-type)))
    (cairo-text-extents ctxt text ex)
    (cairo-text-extents-width ex)))

(define (text->rows ctxt text max-width)
  (let* ((w (text-width ctxt text))
         (f (inexact->exact (floor (* (string-length text) (/ max-width w))))))
    (let loop ((s text)
               (r '()))
      (cond ((string-null? s) (reverse r))
            ((< (text-width ctxt s) max-width)
             (loop "" (cons s r)))
            ((string-index s #\space (if (< f (string-length s)) f 0))
             => (lambda (i)
                  (loop (string-drop s (add1 i))
                        (cons (string-take s (add1 i))
                              r))))
            (else (loop "" (cons s r)))))))



(cairo-select-font-face c "Impact" CAIRO_FONT_SLANT_NORMAL CAIRO_FONT_WEIGHT_NORMAL)
(cairo-set-font-size c 30)

(cairo-move-to c 20 50)
(cairo-set-source-rgba c 1 0 0 1)
(cairo-show-text c "The chicken says:")

(cairo-set-font-size c 20)

(let ((rs (text->rows c text 220.0)))
  (when (> (length rs) 4)
    (error (sprintf "String too long by ~a chars." (string-length (last rs)))))
  (for-each (lambda (t o)
              (cairo-move-to c 20 (+ 100 (* o 30)))
              (cairo-show-text c t))
            rs '(0 1 2 3)))

(cairo-surface-write-to-png s "foo.png")