On 5/29/2024 8:58 PM, Linas Stonys wrote:
Hi,
I'm sure that for lua gurus it is known behavior that user_defined whatsit
clears the \lastskip but for me it was a big surprise.
little example:
aa
\vskip11.1pt
\showthe\lastskip
\directlua{%
local x = node.new('whatsit', 'user_defined')
x.type=115
x.value="TEXT"
node.write(x)
}%
\showthe\lastskip
\bye
log:
> 11.1pt.
l.4 \showthe\lastskip
?
> 0.0pt.
l.13 \showthe\lastskip
I just accidentally noticed that I messed up output trying to markup
document.
I was sure that luatex will step over these whatsits.
Why? We also have \lastpenalty etc and if would become confusing if last
means "last seen" instead of last on the list. It's not a register but a
'reference to a stored state'.
You could check the lastskip before you write the whatsit, maybe
backtrack i.e. remove it, insert the whatsit and then reinsert the glue
node or otherwise insert the whatsit before the last node if it's a skip
(you can mess with the current list)
Is there another way to write user_defined whatsits directly without
effecting \lastskip?
My goal is to mark text in DVI mode with user_defined whatsits and on
the shipout turn them
to postscript \special's for accessible pdf
I'd probably try to insert before the last glue in a list but it all
depends one the macro package and what it does with skips etc in various
places.
Hans
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