Re: Weird behaviour with after-line-breaking and minimum-length-after-break

[Jean Abou Samra]

Le 02/04/2021 à 10:28, Thomas Morley a écrit :
> Hi,
>
> consider the following code:
>
> \version "2.23.1"
>
> \paper { ragged-right = ##t }
>
> {
>    \override TrillSpanner.springs-and-rods = #ly:spanner::set-spacing-rods
>    \override TrillSpanner.minimum-length-after-break = 60
>    \override TrillSpanner.minimum-length = 60
>    \override TrillSpanner.after-line-breaking = ##t
>
>    b1\startTrillSpan \break b\stopTrillSpan
> }
>
> I see two bugs here:
> (1)
> Setting after-line-breaking = ##t should enable printing the
> TrillSpanner on second line.
> It does not - for every tested version, starting with 2.12.3.
>
> (2) minimum-length-after-break takes affect on second line although
> TrillSpanner is not continued there.
> If minimum-length-after-break is unset, minimum-length is applied to
> the not printed part of the broken TrillSpanner.
> This happens even if after-line-breaking = ##f
>
> We currently have seven grobs with after-line-breaking set to
> ly:spanner::kill-zero-spanned-time:
> DurationLine, Glissando, Hairpin, LyricHyphen, TrillSpanner,
> VoiceFollower and VowelTransition
>
> TrillSpanner is the only one with bug (1)
> All of them suffer from bug (2)
>
> Cheers,
>    Harm

Hi Harm, Regarding bug (1): maybe this is because there is not enough 
room for the TrillSpanner? Looking at the output of

\version "2.22.0" \paper { ragged-right = ##t } {   \override 
TrillSpanner.springs-and-rods = #ly:spanner::set-spacing-rods   
\override TrillSpanner.minimum-length-after-break = 100   \override 
TrillSpanner.minimum-length = 100   b1\startTrillSpan \break b b 
b\stopTrillSpan } I can see that the "Tr" mark is placed just above the 
note. I applied the following diff:

diff --git a/lily/line-spanner.cc b/lily/line-spanner.cc index 
cc848d4cc7..48679448f2 100644 --- a/lily/line-spanner.cc +++ 
b/lily/line-spanner.cc @@ -331,9 +331,11 @@ Line_spanner::print (SCM 
smob)    Offset dz_dir = dz.direction ();    if (gaps[LEFT] + 
gaps[RIGHT] > dz.length ())      { +      message ("Not enough room for 
line spanner.");        return SCM_EOL;      } +  message ("About to 
print line spanner");    Stencil line;    for (LEFT_and_RIGHT (d))      {

Then, on the example

\version "2.22.0" \paper { ragged-right = ##t } {   \override 
TrillSpanner.springs-and-rods = #ly:spanner::set-spacing-rods   
\override TrillSpanner.minimum-length-after-break = 50   \override 
TrillSpanner.minimum-length = 50   \override 
TrillSpanner.after-line-breaking = ##t   b1\startTrillSpan \break 
b\stopTrillSpan } I get the log:

Drawing systems...

Refusing to print line spanner because it is too short.

About to print line spanner

Not sure if something can be done about this.

Bug (2) is clearly unexpected. Though, I can see that VowelTransition 
does ignore minimum-distance-after-break when invisible, at least in 
this test case:

\version "2.23.2" { c1 1 } \addlyrics { Ah \tweak 
minimum-length-after-break 100 %\tweak after-line-breaking ##t 
\vowelTransition \break oh }

There is code in lily/vowel-transition.cc that accesses 
after-line-breaking. ly:spanner::set-spacing-rods should probably do 
something along the same lines.

Best regards, Jean