[XeTeX] Redefining the footnotes in XeTeX

[Brian Anderson]

Hello,

I'm working on a file, and I want to change the layout of the  
footnotes. I've looked at this several times, but haven't found  
anything, or even where to start.

What I'm trying to do is change the footnotes at the bottom of the  
page from this:

1) first note
2) second note
..
6) sixth note

to this:

1) first note 2) second note
3) this is a long footnote, so it is on its own line
4) short note 5) short note 6) short note

I'd like to find a way to have XeTeX determine whether there is enough  
space on the line for 2 or more footnotes, or whether there should  
only be one.

Any suggestions or ideas of where to start welcome.

Thanks.

Brian