Toolkit method to generate default expansion

[samuelbradshaw]

Is your feature request related to a problem? Please describe.
#4250 generates an expansion map automatically (based on repeats, endings, codas, etc. in the score) when importing a MusicXML file to Verovio.

Describe the solution you'd like
It would be helpful if there were a way to generate an expansion map for an existing MEI document, using similar logic as #4250, but without the need for a conversion from MusicXML. Most of the scores I'm working with start as MusicXML, but sometimes I'm modifying an MEI document that's already been converted, and it would be nice to generate a new expansion after those modifications.

Maybe it could be a toolkit method, such as AddDefaultExpansion() or GetDefaultExpansion()?

In addition to simply calculating the order of the expansion, #4250 also creates <section> elements that the expansion plist can refer to, and moves measures into those sections. I would hope that a new toolkit method would do the same.

[rettinghaus]

A rule of thumb is to not change the input file, which would happen with such a feature. Furthermore, this is really tricky to parse, and you would probably miss many things, like a repetition that should happen more than once.

[lpugin]

As for any rules, there are exceptions, and that is the case for --expand and some of the options in the "loading selectors and processing" section. So we certainly do not want this to happen by default, be having an option to trigger it explicitly would be OK.

It is true that this tricky, but for simple cases it should still be possible to do it in a fairly straight-forward manner. For more complicated cases, maybe a good starting point would be to use files exported from MuseScore? See measures and repeats. You will notice there is a whole set of @type attributes used for round-tripping. Eventually, these might be added to MEI if that makes sense.