Score with `kern2mens` not vertically in sync

[WolfgangDrescher]

As mentioned in https://github.com/rism-digital/verovio/issues/2690 I have a problem where the score is no longer vertically in sync when combined with kern2mens filter.

When I use !!!filter: kern2mens notes are not aligned vertically to each other. The beginnings of each "bar" are always in sync (green), but within a "bar" notes do not match above the other staffs (red). Is there a way to get this in sync?

It seems to be especially problematic with tied notes. E.g. in the bassus in bar 5 (last bar in the screenshot).

You can find my example here: https://verovio.humdrum.org/?file=https://raw.githubusercontent.com/WolfgangDrescher/lassus-geistliche-psalmen/07acddbc759e9e7c7c396bb5bc4370add0752c71/kern/01-beatus-vir.krn&filter=kern2mens

[craigsapp]

You are adding the barlines by hand, I see (since they are not there by default):

But of course the misalignment still needs to be figured out...

Here are two tips:

I have a method for giving a shorter URL when coming from Github (but the general URL method you use is fine):

https://verovio.humdrum.org/?github=WolfgangDrescher/lassus-geistliche-psalmen/kern/01-beatus-vir.krn&filter=kern2mens

(I probably have to fix it for cases when the primary branch is not master).

For Github links, I have automatic detection of the actual data from the webpage for a score:

https://verovio.humdrum.org/?file=https://github.com/WolfgangDrescher/lassus-geistliche-psalmen/blob/master/kern/01-beatus-vir.krn

And I added as a demo:

!!!verovio: evenNoteSpacing 1

which turns on the evenNoteSpacing option in verovio, making mensural music prettier. The 1 is optional. To unset it you have to first change it to 0 and then delete the line (such options are currently persistent, but I will make them reset whenever verovio is called so that such options will not apply to a new different).

[craigsapp]

The first measure is correctly aligned, but then after that the following measures are incorrect:

Removing the first measure causes the second measure to align properly:

And removing the second measure causes the third one to align properly:

Removing the barline between the first and second measures causes the second measure to be aligned correctly:

Converting and displaying MEI data, which seems correct:

Removing one of the <barLine> elements (from bottom staff) yields correct alignment of the second measure:

So it seems to be a bug in verovio related to internally promoting of <barlines> into <measures> (which is needed for allowing system breaks in mensural music).

Here is the Humdrum test data:

**mens  **mens  **mens
*staff3 *staff2 *staff1
*Ivox   *Ivox   *Ivox
*I"Bassus   *I"Tenor    *I"Cantus
*clefC3 *clefC2 *clefG2
*M2/1   *M2/1   *M2/1
*k[]    *k[]    *k[]
*met(C|)    *met(C|)    *met(C|)
=1- =1- =1-
sir Sir sidd
sig .   Midd
.   .   Midd
=   =   =
Mig Sir sib
Mig .   .
Mie .   Micc
Mif .   Mia
=3  =3  =3
*-  *-  *-

Click to view MEI conversion

```xml