More explanations to make-engraver available

[Urs Liska]

I'm wondering if there's any comprehensive write-up about the components 
of make-engraver available anywhere.

So far all my (rather few) engravers have been simply based on a 
template provided by someone else, but I would be really glad to become 
more independent about that.

I understand that a (Scheme) engraver is a lambda function that is 
passed a context, and that it (usually, always?) returns an object 
created with (make-engraver).

I further see that within make-engraver one defines a (subset of a) 
number of different elements (initialize, process-music etc.) that will 
then process the given context at different stages of the compilation 
process. I have also read the docstring of make-engraver in 
scm/output-lib.scm.

However, it is still unclear to me what exactly the different elements 
that can be defined in make-engraver are doing, in what order they are 
called, which information they are passed and what the "results" of 
these calls are.

Rather than having to resort to browsing through the LSR and getting the 
information by guessing from existing engravers I would really like to 
see this properly explained somewhere, either in a comprehensive 
tutorial or - better - in the official documentation.

Did I just not find that or is that actually missing information?

Urs