Mapping engravings to MIDI output

[Dan Grover]

Hi all,

I'm working on a project that requires pre-rendered engravings of music being
synced up with MIDIs.

I've managed to get Lilypond to output a single line of a song (e.g.
http://files.dangrover.com/moonlight-oneimage.png), but now I need to produce
a mapping between the MIDI event and the x coordinate within such output.

I've got Lilypond building finally and have been reading up on libguile and
reading all the lilypond headers and trying to figure out how it all fits
together.

I'm not asking for any hand-holding, but I would be grateful if someone could
give me some quick high-level advice on what I'll need to accomplish this.

The somewhat vague approach/plan I've got in my head right now is:

1) to intercept the note engraver and have it print out a mapping of: some
identifier for the note/smob it's printing -> absolute x coordinate (I assume
that i can get the absolute x coordinate by traversing up the hierarchy and
adding up the x-extents until I get to the top level object)

2) to intercept the midi performer and have it print a mapping of: some
identifier for the note -> event index

...then to take those two pieces of output and merge them together so I get
event index -> x coordinate.

Am I on the right path?

Thanks a lot!

Dan Grover