[Xcb] question about iterator/length generation

[Thomas Hunger]

Hello,

I have (hopefully) simple question which I cannot figure out: What are 
the rules for generating iterator access and _length functions?

So far I believe:

* Generate an iterator for every struct.
* Generate iterator for every list which is member of a struct.
* Generate iterator for lists in replies?
* Generate simple accessor for lists with fixed-length-type (just 
  return an array of pointers) but no iterator.

I cannot figure out when the xxx_length accessor has to be generated.

Any pointers to relevant mails etc. would be very nice! 

Tom