fake duplex page reordering? [patch]

[Rob Mahurin <rob@xxxxxxx>]

Hello,

I have an HP Deskjet (693C, fwiw) in which the pages come out of the
printer face up and so wind up in reverse order relative to how the
were printed: the first page printed ends up on the bottom of the
stack, the last on the top.  I have been "fake duplex" printing using
a script like

<code snippet>
psselect -e $fname | lp
# surely there's a better way to determine the total number of pages
[ x$(( $(psselect -p_1 $fname 2>&1 > /dev/null\
        | tr "[]" " \n" | head -1 ) % 2 ))x == x1x ] && 
    echo "[0] Wrote (almost) blank page, 2 bytes" &&
    echo . | lp
echo -n "Press enter to print the odd pages ..."
read;
psselect -or $fname | lp
</code snippet>

i.e., print the even pages, print a blank page if there are more odds
than evens (giving me page 2 on the bottom, last even page on top or a
blank if need be), let me stuff that stack of paper back in the feeder
tray, and the print the odd pages in reverse order.  This give me a
properly-ordered document with page 1 at the top, ready to staple with
no reshuffling.  The problems are that I have to convert whatever it
is to Postscript, with honest page numbers.

I have just discovered apsfilter and its fake duplex option, which
does the conversion cruft for me and has a much nicer restarting
mechanism, which I like.  Unfortunately it doesn't reverse the odd
pages, which means that I have to reorder all of the pages twice
(once feeding them back in for the odd sides, and again before
stapling them).  I am lazy and dislike this.  :)  How to fix it?

I've poked around and not found any documentation for this, and
looking at the source (/usr/share/apsfilter/bin/apsfilter on my Debian
woody system, with apsfilter 6.1.1) it seems that the
print_ps_duplex() function works essentially the same way as mine
(always refreshing).  It seems that the way to change it would be 
to add a DUPLEX_REVERSE option to the option set (in apsfilterrc?) and
change print_ps_duplex() to print the extra blank page if
the last page is odd and reverse the odd pages if DUPLEX_REVERSE is
set. 

The first is a little tricky.  I don't really like my kludge for
discovering the parity of the last page, but can't think of a prettier
way to do so.  It looks like the code to add after the if statment
inside the even-printing subshell would be

  [ "$DUPLEX_REVERSE" -a \
      x$(( $(psselect -p_1 "$APS_TMPDIR/duplex.ps" 2>&1 > /dev/null\
      | tr "[]" " \n" | head -1 ) % 2 ))x == x1x ] && \
    echo . | print_ascii

but that breaks your non-dependence on psselect and I'm not sure that
the blank page would make it into the file copy-even.  In fact, I'm
sure not, since that gets done in print_data.  Would it be safe to
change the	tee "$APS_TMPDIR/copy-$SAVE_DUPLEX_COPY" | print_copy
in print_data to a tee --append?  or perhaps

  local flag; 
  [ "$DUPLEX_REVERSE" -a "SAVE_DUPLEX_COPY" ] &&
    flag=-a
  tee $flag "$APS_TMPDIR/copy-$SAVE_DUPLEX_COPY" | print_copy

I guess that's a question of how safely the temporary directories are
created.  

The second piece is straightforward to do: change the section
where the odd pages are printed to something like

  local flag
  if find_filter psselect; then
     [ "$DUPLEX_REVERSE" ] && flag=-r
     psselect -q -o $flag < "$APS_TMPDIR/duplex.ps"
  else
     # pstops exists, otherwise we wouldn't be here (see above)
     [ "$DUPLEX_REVERSE" ] && flag=-
     pstops -q 2:${flag}0 < "$APS_TMPDIR/duplex.ps"
  fi | print_ps

I have just implemented these changes on my own system and they seem
to work, so I'll dignify this message by calling it a "patch".  It's
not complete because you need to tell the user when to use
DUPLEX_REVERSE, but I don't think it's all that bad for a morning's
effort.  

Thanks for writing such clear code, by the way.  

Please CC: me on any replies, as I'm not on this list.

Rob

-- 
Honesty's the best policy.
		-- Miguel de Cervantes