Ok, this should do it.
The intention is to provide extra functionality to text spanners. By using
this code, you have all the functionality of normal text spanners, but you
are able to have multiple spanners per voice.
You simply need to swap the regular engraver for this one in a layout
block, and use the commands I've defined: \startTextSpanOne, and the like.
(You can change the names, of course, and add more. This is crying out
for a better interface, I know,)
Regarding difficulties mentioned earlier in the thread:
The spanners should nest properly and maintain their orientation across
line breaks. Here this is achieved by assigning minute variations of
outside-staff-priority behind the scenes. (Turns out you can use
outside-staff-priorities like 350.0001 ....) You can still override and
tweak outside-staff-priority of TextSpanner if you want.
I believe that this manipulation may be avoided by inventing a new
alignment grob "to bind them all." but I'm not sure. Since the attached
seems sufficient, this could wait until time came (if ever) to add this to
the code base.
DN
%%%%%%%%%%%
\version "2.19"
%% Incorporating some code from the rewrite in Scheme of
%% Text_spanner_engraver in input/regression/scheme-text-spanner.ly
#(define (add-bound-item spanner item)
(if (null? (ly:spanner-bound spanner LEFT))
(ly:spanner-set-bound! spanner LEFT item)
(ly:spanner-set-bound! spanner RIGHT item)))
#(define (axis-offset-symbol axis)
(if (eq? axis X) 'X-offset 'Y-offset))
#(define (set-axis! grob axis)
(if (not (number? (ly:grob-property grob 'side-axis)))
(begin
(set! (ly:grob-property grob 'side-axis) axis)
(ly:grob-chain-callback
grob
(if (eq? axis X)
ly:side-position-interface::x-aligned-side
side-position-interface::y-aligned-side)
(axis-offset-symbol axis)))))
#(define (assign-spanner-index spanner orig-ls)
"Determine the position of a new spanner in an ordered sequence
of spanners. The goal is for the sequence to begin with zero and
contain no gaps. Return the index representing the spanner's position."
(if (null? orig-ls)
0
(let loop ((ls orig-ls) (insert? #t) (result 0))
(cond
((null? ls) result)
;; position at head of list
((and insert? (> (caar orig-ls) 0))
(loop ls #f 0))
;; no gaps, put at end of list
((and insert? (null? (cdr ls)))
(loop (cdr ls) #f (1+ (caar ls))))
;; fill lowest position of gap
((and insert?
(> (caadr ls) (1+ (caar ls))))
(loop (cdr ls) #f (1+ (caar ls))))
(else (loop (cdr ls) insert? result))))))
alternateTextSpannerEngraver =
#(lambda (context)
(let (;; a list of pairs comprising a spanner index
;; (not spanner-id) and a spanner which has been begun
(spanners '())
(finished '()) ; list of spanners in completion stage
(start-events '()) ; list of START events
(stop-events '())) ; list of STOP events
(make-engraver
;; \startTextSpan, \stopTextSpan, and the like create events
;; which we collect here.
(listeners
((text-span-event engraver event)
(if (= START (ly:event-property event 'span-direction))
(set! start-events (cons event start-events))
(set! stop-events (cons event stop-events)))))
;; Populate 'note-columns property of spanners. Bounds are
;; set to note columns, and each spanner keeps a record of
;; the note columns it traverses.
(acknowledgers
((note-column-interface engraver grob source-engraver)
(for-each (lambda (s)
(ly:pointer-group-interface::add-grob
(cdr s) 'note-columns grob)
(add-bound-item (cdr s) grob))
spanners)
;; finished only contains spanners, no indices
(for-each (lambda (f)
(ly:pointer-group-interface::add-grob
f 'note-columns grob)
(add-bound-item f grob))
finished)))
((process-music trans)
;; Move begun spanners from 'span' to 'finished'. We do this
;; on the basis of 'spanner-id. If we find a match--either
;; the strings are the same, or both are unset--a transfer
;; can be made. Return a warning if we find no match: spanner
;; hasn't been properly begun.
(for-each
(lambda (es)
(let ((es-id (ly:event-property es 'spanner-id)))
(let loop ((sp spanners))
(if (null? sp)
(ly:warning "No spanner to end!!")
(let ((sp-id (ly:event-property
(event-cause (cdar sp)) 'spanner-id)))
(cond
((or
(and
(string? sp-id)
(string? es-id)
(string=? sp-id es-id))
;; deal with \startTextSpan, \stopTextSpan
(and
(null? sp-id)
(null? es-id)))
(set! finished (cons (cdar sp) finished))
(set! spanners (remove (lambda (s) (eq? s (car sp))) spanners)))
(else (loop (cdr sp)))))))))
stop-events)
;; The end of our spanners can be acknowledged by other engravers.
(for-each
(lambda (f)
(ly:engraver-announce-end-grob trans f (event-cause f)))
finished)
;; Make spanners in response to START events.
;;
;; Each new spanner is assigned an index denoting its position relative to
;; other active spanners. This is enforced (for the moment) by adding
;; a small amount to the spanner's 'outside-staff-priority proportional to
;; this index. This is unlikely to result in conflicts, though a better
;; solution may be to organize the spanners by a new alignment grob.
;;
;; Also, add any existing spanners to the 'side-support-elements array of
;; the new spanner. This ensures correct ordering over line breaks when
;; 'outside-staff-priority is set to #f (which means that it is no longer
;; an outside-staff-object--not the default).
(for-each
(lambda (es)
(let* ((new (ly:engraver-make-grob trans 'TextSpanner es))
(new-idx (assign-spanner-index new spanners))
(new-osp (ly:grob-property new 'outside-staff-priority))
(new-osp (if (number? new-osp)
(+ new-osp (/ new-idx 1000.0))
new-osp)))
(set! (ly:grob-property new 'outside-staff-priority) new-osp)
(set-axis! new Y)
;; Add spanners with a lower index than new spanner to
;; its 'side-support-elements. This allows new spanners
;; to fill gaps under the topmost spanner.
(for-each
(lambda (sp)
(if (< (car sp) new-idx)
(ly:pointer-group-interface::add-grob new
'side-support-elements (cdr sp))))
spanners)
(set! spanners (cons (cons new-idx new) spanners))
(set! spanners
(sort spanners (lambda (x y) (< (car x) (car y)))))))
start-events)
;; Events have served their purpose for this timestep. Clear
;; the way for new events in later timesteps.
(set! start-events '())
(set! stop-events '()))
((stop-translation-timestep trans)
;; Set bounds of spanners to PaperColumns if they haven't been set.
;; This allows spanners to be drawn between spacers. Other uses?
;; Doesn't appear to affect whether spanners can de drawn between
;; rests.
(for-each
(lambda (s)
(if (null? (ly:spanner-bound (cdr s) LEFT))
(ly:spanner-set-bound! (cdr s) LEFT
(ly:context-property context 'currentMusicalColumn))))
spanners)
(for-each
(lambda (f)
(if (null? (ly:spanner-bound f RIGHT))
(ly:spanner-set-bound! f RIGHT
(ly:context-property context 'currentMusicalColumn))))
finished)
(set! finished '()))
((finalize trans)
;; If spanner ends on spacer at end of context?
(for-each
(lambda (f)
(if (null? (ly:spanner-bound f RIGHT))
(ly:spanner-set-bound! f RIGHT
(ly:context-property context 'currentMusicalColumn))))
finished)
(set! finished '())
;; User didn't end spanner.
(for-each
(lambda (sp)
(ly:warning "incomplete spanner removed!")
(ly:grob-suicide! (cdr sp)))
spanners)
(set! spanners '())))))
startTextSpanOne =
#(make-music 'TextSpanEvent 'span-direction START 'spanner-id "1")
stopTextSpanOne =
#(make-music 'TextSpanEvent 'span-direction STOP 'spanner-id "1")
startTextSpanTwo =
#(make-music 'TextSpanEvent 'span-direction START 'spanner-id "2")
stopTextSpanTwo =
#(make-music 'TextSpanEvent 'span-direction STOP 'spanner-id "2")
startTextSpanThree =
#(make-music 'TextSpanEvent 'span-direction START 'spanner-id "3")
stopTextSpanThree =
#(make-music 'TextSpanEvent 'span-direction STOP 'spanner-id "3")
%%%%%%%%%%%%%%%%%%%%%%%%%%%%% EXAMPLE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\layout {
\context {
\Voice
\remove #"Text_spanner_engraver"
\consists \alternateTextSpannerEngraver
}
}
\relative c' {
\override TextSpanner.style = ##f
\override TextSpanner.thickness = 10
%\override TextSpanner.to-barline = ##t
a4
-\tweak color #red
\startTextSpan
b
-\tweak color #green
\startTextSpanOne
c
-\tweak color #blue
\startTextSpanTwo
d
\startTextSpanThree
a4\stopTextSpan
b
\stopTextSpanOne
-\tweak color #red
\startTextSpan
c
\stopTextSpanTwo
-\tweak color #green
\startTextSpanOne
d
\stopTextSpanThree
-\tweak color #blue
\startTextSpanTwo
a4
\startTextSpanThree
b c d
\break
a4 b c d
a1\stopTextSpan\stopTextSpanOne\stopTextSpanTwo\stopTextSpanThree
}
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