input/regression/automatic-polyphony-context-id.ly

   1 \version "2.13.12"
   2
   3 \header {
   4   texidoc = "The bottom-level contexts in polyphony shorthand are
   5 allocated a context id in order of creation, starting with
   6 @code{\"1\"}.
   7 This snippet will fail to compile if either voice has an invalid
   8 @code{context-id} string.
   9 "
  10 }
  11
  12 assertContextId =
  13 #(define-music-function (parser location id) (string?)
  14    (let ((music (make-music 'ApplyContext
  15                             'procedure
  16                             (lambda (ctx)
  17                               (and
  18                                (not (string=? (ly:context-id ctx) id))
  19                                (ly:error "context-id mismatch found: expecting ~s, got ~s"
  20                                          id
  21                                          (ly:context-id ctx)))))))
  22      music))
  23
  24 \relative c'' {
  25   <<
  26     {
  27       \assertContextId "1"
  28       c4 d e2
  29     }
  30     \\
  31     {
  32       \assertContextId "2"
  33       a,4 b c2
  34     }
  35   >>
  36 }