Text spanner associated start and end notes

[Andrew Bernard]

Greetings All,

This is a Scheme question. We are trying to make a callback function for a customised text spanner that centres the left and right markup text exactly over the centre of the first and last notes the spanner covers. I am doing this in Scheme, and all is working, but so far I am unable to determine the actual grob for the note that the \startTexSpan is associated with. It appears that the left bound of the spanner is a paper column object, not a note. I do not know how to go from that to find the note. Why do I want to find the note? So that I can find its half width and use that as the offset for the text, the point being that different note values have different widths – long white notes are wider, for example.

I would very much like to post code here, but it is difficult to post code to ask for assistance in this case where I simply have idea no how to proceed. I apologise for this. Somewhat problematical. I am looking for conceptual guidance on this matter, rather than code assistance.

I have searched LSR a dozen times with many keywords. I have read and reread the Scheme function list. I have googled as deeply as I know how. I have written many pages of exploratory code in Scheme. I am unable to believe that we are the first and only people to want to do this, as I am unable to find any examples similar. What am I not understanding or missing? Any help would be most appreciated.

Andrew