Feature request: Tuplet bracket style settings

[bruys .]

*The current situation*
a) Lilypond's default placement of tuplet brackets is from the stem of the
first note to the stem of the last note, if the bracket is on the stem side
(see second and fourth examples in the accompanying png file). If the tuplet
bracket is on the notehead side, the bracket extends from the left-hand edge
of the first notehead to the right-hand edge of the last notehead (see the
fourth example in the png file). It is possible to make the bracket extend
for the duration of the notes, so that it extends past the last notehead
(see the third example).

b) The numeral (here '3') is placed in the visual centre of the bracket (all
examples).

*The proposed features*
a) It is desired to be able to change the style of the bracket, without
reverting to ad hoc manual settings. In particular, a common style is for
the bracket to extend from the left-hand edge of the first notehead to the
right-hand edge of the last notehead, even when the bracket is on the stem
side (as in the fifth example). Although this is not a universally adopted
style, Elaine Gould in *Behind Bars* says *

*
*A bracket should extend from the left-hand edge of the first notehead or
rest, to the right-hand edge of the final notehead or rest. It does not
encompass accidentals, grace notes or an arpeggio line that precede the
first note. When a final note is up-stemmed and has a tail (end of bar 2 *[in
her figure, not reproduced here]*), the bracket still finishes with the stem
(i.e. the right-hand edge of the note), not with the tail *[figure
omitted]*In some editions brackets finish just after the tail: this
saves vertical
space, as the end notch can be lowered after the stem.*

In Gardner Read, *Music Notation*, this also seems to be the general
practice (although in my copy the bracket lengths are not consistent). The
figures in the current Wikipedia article on tuplets also uses this style,
http://en.wikipedia.org/wiki/Tuplet.

b) Although placement of the numeral in the visual centre of the bracket is
a good default, it is sometimes desirable to have the numeral placed at the
rhythmic centre of the tuplet. It is desired that changing a setting could
achieve this. Elaine Gould again:

*When one part of a beat is disproportionately long visually, traditionally
the numeral remains at the visual centre of the group. However, where there
are complex groups of tuplets, it is more helpful if the numeral moves to
the rhythmic centre of the group, even if this is visually
off-centre*[figure omitted, consisting of a triplet containing two
quaver rests and
four demisemiquavers, and another quintuplet containing four semiquavers, a
dotted minim, and a crotchet rest]


The examples are generated from the following:

%% triplet examples
\version "2.12.3"


notes = {
  %% Default behaviour
  \times 2/3 { b'8[
               \times 2/3 { b'16 b' b' }
               b'8]
             }

  %% With both tuplet brackets
  \override TupletBracket #'bracket-visibility = ##t
  \times 2/3 { b'8[
               \times 2/3 { b'16 b' b' }
               b'8]
             }

  %% With tuplet bracket extending to duration of notes
  \set tupletFullLength = ##t
  \times 2/3 { b'8[
               \times 2/3 { b'16 b' b' }
               b'8]
             }
  \set tupletFullLength = ##f

  %% With inner tuplet bracket on the upper, notehead, side
  \times 2/3 { b'8[
               \once \override TupletBracket #'direction = #UP
               \times 2/3 { b'16 b' b' }
               b'8]
             }

  %% With manual change to the lower bracket length
  \times 2/3 { \once \override Voice.TupletBracket #'shorten-pair = #'(-0.2
. -1.5)
             b'8[
               \once \override TupletBracket #'direction = #UP
               \times 2/3 { b'16 b' b' }
               b'8]
             }
}

\score {
  \notes
}

TripletExamples.png
Description: PNG image