Re: Align bracket not to notes but to enclosing bars

[David Nalesnik]

Hi Urs,

On Mon, Feb 4, 2019 at 6:12 AM Urs Liska <address@hidden> wrote:
>
> I have created a command that uses \startGroup and \stopGroup to print 
> annotated horizontal brackets:
>
> % Create a horizontal bracket with included text.
> % If no text is desired an empty string has to be given.
> % By default the bracket is above the staff, otherwise
> % #DOWN has to be given as optional argument.
>
> \layout {
>   \context {
>     \Voice
>     \consists "Horizontal_bracket_engraver"
>     \override HorizontalBracket.bracket-flare = #'(0 . 0)
>     \override HorizontalBracket.staff-padding = 4.5
>   }
> }
>
> startBracket =
> #(define-event-function (direction text)((ly:dir? UP) markup?)
>    #{
>      -\tweak HorizontalBracketText.text #text
>      -\tweak HorizontalBracketText.direction #(* -1 direction)
>      -\tweak HorizontalBracketText.Y-offset #(if (= direction UP) -2.5 1)
>      -\tweak direction #direction
>      \startGroup
>    #})
>
> stopBracket = \stopGroup
>
> \relative {
>   g'4 g e d
>   c \startBracket "Hello" d e f |
>   g1 \stopBracket
> }
>
> (results attached as document.png).
>
> However, in addition to that I need a way to align the start and end of that 
> bracket not to the notes like in the example but to the enclosing measures, 
> and optionally the whole staffline.
>
> Is there any reasonable approach to doing that short of custom-printing a 
> stencil by searching the current staff to find the neighbouring barlines (it 
> is guaranteed that there are no line breaks)? The only advantage of going 
> that way would be to have more control over how it actually looks like ...
>

I believe you will need to look for the bar lines (or the containing
NonMusicalPaperColumns). Here's a (still-working as of 2.19.82)
example which uses the MeasureCounter and a custom stencil:
http://lists.gnu.org/archive/html/lilypond-user/2014-10/msg00446.html.
It may be usable as a source of code for your task.  At the moment I
unfortunately can't devote time to a more thorough-going
recommendation!

(I do have an old patch which actually creates a
MeasureAttachedSpanner which I held off submitting until after a new
major release.  If I can get it to apply to current master I could
send it to you.  It does what you want without "co-opting" other
spanners, and has the ability to align endpoints in different ways.
This will give me a LilyPond task to get me back going after a long
hiatus!)

Best,
David