[pdftex] pdfsavepos

[Hans Hagen]

At 16:55 15/04/2003 +0200, Andre Wobst wrote:

>Fine. But I want to be able to insert some position markers in the
>string (here it is "Hello, world!"). I want to be able to print out
>the position of that markers. Unfortunately I can't use specials in
>the dvi output, because after the shipout the dvi output for that page
>isn't available immediately. There seems to be some dvi write caching
>in TeX (at least, that's what I observed). On the other hand, by
>pdfsavepos, I have immediately access to the positions once the
>shipout is performed. As I understood the topic, with builtin TeX
>facilities I can't access any information about relative positions
>within a box even when the box is completely ready before the shipout
>as you can see in my example above.

due to tex's dynamic character you only have access to the position at 
shipout time (or in a second pass); unfortunately you cannot so a fake 
shipout without losing that info, well, you could do something:

open temp file
shipout and save positions
read them file

but as said, there is still this shipped out page (ok, there are means to 
discard it in a second run, or to put it 10 meters in the margin and 
correct the positions for that); even worse, there is no nice way (only 
dirty ones) to hide writes embedded in such a page so you end up with 
multipls refs and toc entries and alike (for that purpose we need a switch 
to enable/disable writes, but so far no-one was willing to implement that 
for me; we also need that kind of control for page imposition and content 
reuse -)

(since this is not that much related to pdftex, we can discuss this of list)

Hans
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