Break out screenshot into a function that can be used by itself

defs.rkt

@@ -28,14 +28,18 @@
                            (string-append (number->string howmany) " nodes"))
                      properties))))
 
-(define (instructionstep step #:screenshot [screenshot #f] . body)
+(define (screenshot path)
+  (let* ([fullpath (string-append "screenshots/" path)]
+         [b (make-object bitmap% fullpath)]
+         [width (send b get-width)]
+         [scale-factor (/ screenshot-width width)])
+    (list (image #:scale scale-factor fullpath fullpath) (linebreak))))
+
+(define (instructionstep step #:screenshot [screenshot-path #f] . body)
   (item (bold (decode-content (list step)))
         (linebreak)
-        (if screenshot
-          (let* ([path (string-append "screenshots/" screenshot)]
-                 [b (make-object bitmap% path)]
-                 [width (send b get-width)]
-                 [scale-factor (/ screenshot-width width)])
-            (list (image #:scale scale-factor path screenshot) (linebreak)))
+        (if screenshot-path
+          (screenshot  screenshot-path)
           (void))
         (decode-content body)))
+