Re: Access a tie from a slur

[Urs Liska]

Hi David,

thank you for now. This is proof that one can at least *get* to the
right information, and when the use-case is clearer one may also find a
more efficient approach if possible.

Just one more question (a simple "yes" or "no" or a pointer to a
function name will do, no need to write a solution): The control-points
in tie-cps are of course relative to the tie's notehead. Is it possible
to determine the offset of the f' from the c'? This seems necessary to
make use of tie-cps to modify the slur.

Urs

Am 03.01.2017 um 02:33 schrieb David Nalesnik:
> Hi Urs,
>
> On Mon, Jan 2, 2017 at 6:33 PM, Urs Liska <address@hidden> wrote:
>> Hi all,
>>
>> the message title may be misleading, but it names the only idea I have
>> for my current issue.
>>
>> I am asked to create a strange slur configuration similar to the
>> attached example. The coloring is only for better referencing in the
>> email, and please don't question the notational use of the challenge -
>> it's asked for and I have to provide a solution (well, actually, right
>> now I'm only investigating if there *is* a proper solution I can offer).
>>
>> The task is to have the blue slur reliably point to the middle of the
>> magenta tie. For the example I have simply used \shape with the slur to
>> make it demonstrate the goal. But I am after a proper solution.
>>
>> My question is if it is somehow possible to access the control points of
>> the magenta tie while still being able to set the control points of the
>> blue slur. I would imagine to have the slur end at the magenta f', then
>> have some function implicitly create the tie there and use the tie's
>> control points to set the slur's control points. (In this constellation
>> the tie wouldn't actually be entered explicitly.)
>>
>> Does this sound plausible from the perspective of when which properties
>> can be retrieved and when changed?
>>
> Not much time to work on this, but I can get you to the Tie's
> control-points from the Slur.
>
> This is a bit inefficient since it filters all the grobs in the line
> to get at the Tie, since there's no pointer that I know of which could
> connect the Slur and Tie.
>
> It's also tailored to the use-case you give.
>
> Anyway...
>
> %%%%%
>
> \version "2.19.53"
>
> #(define slur-touches-tie
>    (lambda (grob)
>      (let* ((rb (ly:spanner-bound grob RIGHT))
>             (sys (ly:grob-system grob))
>             (when (grob::when rb))
>             (elts (ly:grob-array->list
>                    (ly:grob-object sys 'all-elements)))
>             (my-tie (filter (lambda (g)
>                            (and (grob::has-interface g 'tie-interface)
>                                 (equal? (grob::when g) when)))
>                          elts))
>             (tie-cps (ly:tie::calc-control-points (car my-tie))))
>        (display my-tie)
>        (newline)
>        (display tie-cps)
>        (ly:slur::calc-control-points grob))))
>
> {
>   \override Slur.control-points = #slur-touches-tie
>   c'4( d' e' f')~
>   f'1
> }

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