change how attr-keys are printed

quad2/layout.rkt

@@ -53,6 +53,7 @@
   (for/fold ([posn0 ($point 0 0)]
              #:result qs)
             ([q (in-list qs)])
+    #RRR q
     (define first-posn-on-next-line ($point 0 (add1 ($point-y posn0))))
     (define other-possible-posns (list first-posn-on-next-line))
     (define posn1 (for/first ([posn (in-list (cons posn0 other-possible-posns))]

quad2/struct.rkt

@@ -1,5 +1,6 @@
 #lang racket/base
-(require (for-syntax racket/base racket/syntax))
+(require (for-syntax racket/base racket/syntax)
+         racket/struct)
 (provide (all-defined-out))
 
 (struct $drawing-inst () #:transparent)
@@ -9,7 +10,10 @@
 (struct $doc $drawing-inst (inst) #:transparent)
 (struct $page $drawing-inst (inst) #:transparent)
 
-(struct attr-key (name mandatory? default) #:transparent)
+(struct attr-key (name mandatory? default) #:transparent
+  #:methods gen:custom-write
+  [(define (write-proc val out mode)
+     (fprintf out (format ":~a" (attr-key-name val))))])
 
 (define (make-attr-key name [mandatory? #false] [default #false])
   (attr-key name mandatory? default))