quarter tones in tablature

issue 4643

micro-tones in TabStaff are now printable.  Unless the chosen
string-tuning will allow it, this feature is disabled for
FretBoards.
- changing determine-frets (adding an optional argument) and
  fret-number-tablature-format
- adding a regtest with quarter-tone-string-tuning
- documenting it in Documentation/notation/fretted-strings.itely
  and Documentation/changes.tely

1 files changed, 42 insertions, 0 deletions

diff --git a/input/regression/tablature-micro-tone.ly b/input/regression/tablature-micro-tone.ly
new file mode 100644
index 0000000000..ff02d79bdb
--- /dev/null
+++ b/input/regression/tablature-micro-tone.ly
@@ -0,0 +1,42 @@
+\version "2.19.31"
+
+\header {
+  texidoc = "The @code{TabStaff} will print micro-tones as mixed numbers of
+fret-number and a fraction.
+@code{noteToFretFunction = #(my-determine-frets #t)} needs to be set in Score.
+@code{FretBoards} will print those micro-tones only if they can be found in the
+chosen settings for @code{stringTunings}, otherwise a warning (surpressed here)
+will be printed and an empty @code{FretBoard} returned.  Which should be the
+case here for the first pitch: @code{gih}"
+}
+
+#(ly:set-option 'warning-as-error #f)
+#(ly:expect-warning (_ "No string for pitch ~a (given frets ~a)") #{ gih #} '())
+
+\layout {
+  \context {
+    \Score
+    noteToFretFunction = #(determine-frets #t)
+  }
+}
+
+custom-tuning = \stringTuning <e, a, d ges beh eeh'>
+
+mus = \relative {
+  gih4
+  eeses'
+  eeseh
+  ees
+  eeh
+  e
+  eih
+  eis
+  eisih
+  eisis
+}
+
+<<
+  \new Staff << \clef "G_8" \mus >>
+  \new FretBoards \with { stringTunings = \custom-tuning } \mus
+  \new TabStaff \with { stringTunings = \custom-tuning } \mus
+>>