[pdftex] Problem with hlines in pdftex

[Gregory Collins]

Hans Hagen <pragma at wxs.nl> writes:

> Gregory Collins wrote:
> 
> >Hi,
> >
> >I am having a problem with the .pdf files being generated by
> >pdflatex. I am using the longtable package to make documents with
> >tables having rules in them. When viewing the resulting .pdf files
> >in Acrobat Reader, I'm seeing what look like rounding errors: the
> >vertical and horizontal rules in the tables appear and disappear at
> >random, and sometimes lines end up being wider on-screen than
> >others.
> >
> >I (obviously) would like these lines to be at least a pixel wide
> >even when the document is zoomed-out. Changing the anti-aliasing
> >settings in Acrobat Reader doesn't help. Is there anything that I
> >can do to make this problem go away?
> >
> each version of acrobat reader does it differently; version 5 was
> pretty good, 6 is worse (there are more places where accuracy is a
> problem; to me it seems that smoothing/cooltype, caching, rounding
> and transparency (when used) are somehow interacting)

We've traced the problem to the "colortbl" package; when the \rowcolor
command is used, the color fill rectangle painted (which is white in
this case) is painted after the table rules, and it's a rounding error
THERE which is causing Acrobat to paint over the rules. Is anyone
familiar enough with the colortbl package to suggest how it could be
altered to force the rowcolor command to paint the row background
BEFORE any table lines?

Gregory Collins <greg at subrosa.ca>