Order of callback function calls

[Urs Liska]

Hi,

I'm thinking about collecting some (and hopefully a growing corpus) of 
the functions that help dealing with grobs in callback functions and 
make them accessible in an openLilyLib package. For example for so many 
applications it is necessary to find a grob's system, then get all 
objects within that and find specific ones within that list. Or find the 
NoteColumn's at the two ends of a spanner, etc. I think making such 
patterns more accessible with functions is a way for me to become more 
comfortable with this type of grob manipulation, and maybe it will be 
useful to make this area somewhat more accessible for an (even if only 
slightly) wider audience.

I know that some functions can only be called before or after certain 
points in the engraving process. For example all information about the 
absolute positioning of grobs is only available after-line-breaking, 
while some actions (e.g. setting properties like 'X-offset) will only 
have an effect before-line-breaking (whereas one can set the 'color 
property at any time).

I have two questions about this for now:

1. Is there a list somewhere detailing *all* available callbacks?

2. Is there anything general to say about when callbacks for regular 
properties like e.g. 'direction  or 'X-offset. I mean, if I say 
\override DynamicText.X-offset = #my-custom-callback, when will that be 
called?

Best
Urs