Graphics, Figures & Tables ⇒ tabu | Dynamic long Table Headings

[GerlofVito]

I would like to create a 'longtabu' with dynamic headers. 'Longtabu' uses 'longtable', so I think the problem/solution applies to both.

I am using 'datatool' to create a database in the LaTeX file, and then I output the database in a 'longtabu' using \DTLforeach (from the 'datatool' package). I want to display one of the columns of the first row that appears after the page break in the header of the table on that new page.

But I can't figure how to code LaTeX to identify which row appears directly after the page break. I tried using \IfEq (in 'xstring') and \thepage to check if the previous page does not equal the current page, but within the 'longtable'/'longtabu' environment the page number is always the same as the page number that the table starts on. That is, it only knows the page that the table starts on; it doesn't know the page number for each individual row.

And then I tried looking at the commands/macros in the 'longtable' package to see if I could redefine the page breaking command to record the row number before or after the break, but I couldn't figure it out.

I also searched around for other solutions but haven't had any luck.

Any help? MWE attached.

In the MWE, I create the database in the TeX file. In reality, I pull from a CSV file using \DTLloaddb, but I don't think that makes any practical difference.

I use XeLaTeX to typeset, running on Mac OSX in case that matters.

[cgnieder]

I want to display one of the columns of the first row that appears after the page break in the header of the table on that new page.

I can't follow can you maybe explain with an example what exactly you're trying to achieve? In the case of your MWE: do you want »I want this to be the category of the row that follows on this page« to be replaced with »category 2«?

Regards

[cgnieder]

After looking into longtable.sty I doubt that dynamic headers can be done easily. The head is stored in a box once and then reinserted every time it is needed. I believe one would have to rewrite some parts of longtable...

[GerlofVito]

do you want »I want this to be the category of the row that follows on this page« to be replaced with »category 2«

Yes, exactly. In the case of the MWE, I want the header on the second page to say "category 2".

The head is stored in a box once and then reinserted every time it is needed.

So this table is not going to span three pages. At most, it will start on one and continue on to the next.

Would it be possible to redefine the command that creates the header on subsequent pages (\endhead) to save the row number where the break occurs? (Whether it's the row number before or after the break doesn't matter, since I can calculate the row number that I want from either.) Or to redefine another command (like the page break command) to store a variable like the category itself or the row number (which I can then use to get the category)? Or is 'longtable' totally unaware of the contents of the rows when it decides to make the page break?

Thanks for any help/ideas.

[cgnieder]

The main problem here is that all heads are stored before the table is typeset. You would need to know the specific row number at the beginning of the table.

After trying out a few things that all failed I'm out of ideas right now. Maybe someone else will have an idea.

Regards

[GerlofVito]

The main problem here is that all heads are stored before the table is typeset.

I had an example that seemed to be setting a variable in the header with information after the body, but I've overwritten it since then and can't reproduce it now. So ... not sure if/how I managed that.

Thanks for your help. I'll wait and see if anyone else has ideas and figure out a workaround in the meantime.