Size text picts based on slide size

gistfile1.txt

#lang racket

(require racket/draw
         pict
         slideshow)

;; Create a text pict that fits in target pixels of the slide
(define (auto-text str [style null] [target (* 0.8 client-w)] [angle 0])
  (define initial-min 0)
  (define initial-max 1000)

  (define (close-enough? width target)
    (< (abs (- width target)) 10))

  (define (bin-search cur-min cur-max)
    (define next-size
      (exact-round (+ cur-min (/ (- cur-max cur-min) 2))))
    (define width (pict-width (text str style next-size angle)))
    (cond [(close-enough? width target)
           (text str style next-size angle)]
          [(> width target)
           (bin-search cur-min next-size)]
          [(< width target)
           (bin-search next-size cur-max)]))
  
  (bin-search initial-min initial-max))

(cc-superimpose (rectangle client-w client-h
                           #:border-color "black"
                           #:border-width 1)
                (auto-text "Hello world!"
                           (cons (make-color 50 50 50) "Helvetica")
                           ))

(cc-superimpose (rectangle client-w client-h
                           #:border-color "black"
                           #:border-width 1)
                (auto-text "Hello world!"
                           (cons (make-color 50 50 50) "Helvetica")
                           (* 0.5 client-w)))