Start work on adding annotations for horizontal paper variables.

[xmichael-k]

Nice work, very helpful!
Don't worry if my comments are stupid... ;))


http://codereview.appspot.com/143071/diff/1/2
File scm/page.scm (right):

http://codereview.appspot.com/143071/diff/1/2#newcode38
Line 38: (define (annotate-x? layout)
What about
(define (annotate? layout . dir)
  (eq? #t (case dir
            (('X) (ly:output-def-lookup layout 'annotate-x-spacing))
            (('Y) (ly:output-def-lookup layout 'annotate-y-spacing))
            (('()) (or (annotate? layout X) (annotate? layout Y)))
            (else #f)))

http://codereview.appspot.com/143071/diff/1/2#newcode126
Line 126: (add-x-stencil (lambda (x)
Again, this seems to me a little redundant. Maybe one add-stencil
procedure would do it?

http://codereview.appspot.com/143071/diff/1/2#newcode134
Line 134: (if (annotate-y? layout)
I would prefer to put the items to annotate in an alist and do a
(for-each)

http://codereview.appspot.com/143071