[pdftex] Include pdfcolmk in xcolor? (was: problem with color.sty in pdflatex)

[Heiko Oberdiek]

On Mon, Jul 05, 2004 at 06:36:49PM +0200, Uwe Kern wrote:

> Dear all,
> 
> I did think about including pdfcolmk in xcolor myself before since every other week there is
> a thread on this list, asking for help with respect to colors and pagebreaks.
> 
> Given that in pdfcolmk.sty it is said:
> 
> % Limitations: * mark limitations: page breaks in math
> %              * LaTeX's output routine is redefinded.
> %                * Changes in the output routine of newer versions
> %                  of LaTeX are not detected.
> %                * Packages that change the output routine are not
> %                  supported.

A color stack such as in dvips avoid many of the limitations, especially
the ones meantioned above. Thus pdfcolmk.sty was written to show,
what is possible at TeX macro language level and to have something
until a color stack is implemented in pdfTeX.
  Some time ago (sorry, years ago) I started to implement a color
stack and finished it as extension to \pdfliteral. Because of a
request I started to move it to an extension to \special to let
\pdfliteral unchanged. Also then it can be possible to support
some of the syntax of color specials from dvips (useful or useless?).
At that time I hadn't the time for finishing it. But I will now
try to resume my work the next weeks.

> before I start to work on that inclusion, I would like to ask the pdftex experts:
> 
> 1) Does every user of colored text automatically want pdfcolmk to be employed?

If it works (see limitations), then it would be useful.

> 2) Are the cited limitations a problem for `normal' users?

Yes, eg. package multicol is not supported.

> 3) Is there any other harm to be expected from loading pdfcolmk as a default?

In most cases where the output routine is changed I would not expect harm,
but the intended color corrections by pdfcolmk will not be available.

> 4) What is the role of eTeX vs. TeX here?

With eTeX pdfcolmk uses a separate mark register for its work.
This is the safe solution. Without eTeX there is only one mark
register. LaTeX uses it already, so the macros have to be overloaded
to add the informations that are needed by pdfcolmk --> potentially
dangerous.

> 5) Is there, perhaps, some work going on to implement a color stack in pdftex itself
>     (making pdfcolmk and the like superfluous)?

See above.

> Any comments and suggestions are welcome.

My favorite solution would be:
* color stack in pdfTeX, updated pdftex.def and obsolete pdfcolmk.sty
* the mechanism of pdfcolmk can be used in circumstances, where the
  color stack is not sufficient (perhaps broken footnotes across
  columns/pages, column breaking, ...).

Yours sincerely
  Heiko <oberdiek at uni-freiburg.de>
--