Horizontal brackets: adjust start and end point

[Davide Liessi]

Hi everybody.

I'm using horizontal brackets in a piece I'm transcribing, with
bracket-flare set to 0.
I would like the bracket symbols to start a bit before the first note
and end a bit after the last (let's say a bit = about the length of
the head of a quarter note).

E.g. in the following piece i would like the bracket to start a
quarter-note-head-length before c' and end a quarter-note-head-length
after d'.

\new Voice \with {
    \consists Horizontal_bracket_engraver
    \override HorizontalBracket #'bracket-flare = #'(0 . 0)
} {
    c'2 \startGroup d'2\stopGroup
}

I played around with the properties of HorizontalBracket and its
interfaces, but I couldn't achieve the result I want.

I am using the latest stable version (2.14.2), but I can switch to
latest unstable if needed.

I would be grateful if anybody could help me.

Best wishes,
Davide Liessi


P.S. I should mention that I am also using the code provided by harm6 in
http://lists.gnu.org/archive/html/lilypond-user/2011-09/msg00196.html
because I had the same problem as Trevor Bača.
This is however irrelevant: I did my tests with and without harm6's solution.