[XeTeX] \botmark and \firstmark not working for me ...

[Philip Taylor (Webmaster, Ret'd)]

Ron Aaron wrote:
> On Saturday 31 July 2010 23:25:24 Philip Taylor (Webmaster, Ret'd) wrote:
>
>> I would start by looking at your comparison with \null, Ron :
>> if you look at TB, p.~351, you will see that \null is defined
>> as \hbox {}, which is a pretty unlikely value for a null mark.
>
> Hi, Phil --
>
> That turns out to be a red-herring -- since even:
>
> \message{marks are \firstmark,\botmark^^J}
>
> gives no joy...

Yes, the other clue is in your preceding message :

> Yes, absolutely sure. I wonder if my problem stems from the "mark" being
> inside a vbox?  If that's the problem, I don't know how I would get around it

See TB p.~259 : "Similarly. a \mark that occurs in internal vertical mode
goes into a \vbox, and it is not accessible in the main vertical list."

** Phil.