input/regression/stencil-hacking.ly

   1
   2 \version "2.12.0"
   3
   4 \header { texidoc=" You can write stencil callbacks in Scheme, thus
   5 providing custom glyphs for notation elements.  A simple example is
   6 adding parentheses to existing stencil callbacks.
   7
   8 The parenthesized beam is less successful due to implementation of the
   9 Beam. The note head is also rather naive, since the extent of the
  10 parens are also not seen by accidentals.
  11 "
  12
  13 }
  14
  15 #(define (parenthesize-callback callback)
  16    "Construct a function that will do CALLBACK and add parentheses.
  17 Example usage:
  18
  19   \\property NoteHead \\override #'print-function
  20                    =
  21                       #(parenthesize-callback ly:note-head::print)
  22
  23 "
  24
  25
  26    (define (parenthesize-stencil grob)
  27      "This function adds parentheses to the original callback for
  28 GROB.  The dimensions of the stencil is not affected.
  29 "
  30
  31      (let* ((fn (ly:grob-default-font grob))
  32             (pclose (ly:font-get-glyph fn "accidentals.rightparen"))
  33             (popen (ly:font-get-glyph fn "accidentals.leftparen"))
  34             (subject (callback grob))
  35
  36             ; remember old size
  37             (subject-dim-x (ly:stencil-extent subject 0))
  38             (subject-dim-y (ly:stencil-extent subject 1)))
  39
  40         ;; add parens
  41         (set! subject
  42              (ly:stencil-combine-at-edge
  43               (ly:stencil-combine-at-edge subject 0 1 pclose 0.2)
  44               0 -1 popen  0.2))
  45
  46         ; revert old size.
  47        (ly:make-stencil
  48         (ly:stencil-expr subject) subject-dim-x subject-dim-y)))
  49    parenthesize-stencil)
  50
  51
  52 \layout { ragged-right = ##t }
  53 \relative c' {
  54     c4 e
  55
  56     \override NoteHead  #'stencil
  57     =
  58     #(parenthesize-callback ly:note-head::print)
  59     g bes
  60     \revert NoteHead #'stencil
  61
  62     \override Beam  #'stencil
  63     =
  64     #(parenthesize-callback ly:beam::print)
  65
  66     a8 gis8 a2.
  67
  68 }
  69
  70
  71