[XeTeX] c.t.t. post re: \mag
Jonathan Kew
jonathan_kew at sil.org
Tue Feb 19 15:43:46 CET 2008
On 19 Feb 2008, at 2:12 pm, Andreas Matthias wrote:
> Jonathan Kew wrote:
>
> [ \mag ]
>
>> I have just checked in corrections to both xetex and xdvipdfmx, and I
>> believe this stuff is now working correctly.
>
> I just spotted that the left and top margins (the origin of TeX's
> coordinate system) are not scaled by \mag. This is in contrast to
> pdftex. I'm not sure which one is correct.
Hmmm. Neither am I.
Experimenting with plain TeX + dvips + ghostscript, it seems that
\mag does *not* affect the top and left margins; the origin of a \mag-
nified page remains at (1in, 1in) from the corner of the sheet.
With pdfTeX, on the other hand, the origin does move according to
\mag, as you noted.
So there seems to be a discrepancy or incompatibility between the
existing engines/paths already. Let the user beware!
Thinking it over, I don't recall a completely explicit statement in
The TeXbook about the relationship between \mag and the page origin,
but I think we can deduce that Knuth did not expect it to shift, if
we consider his \magnification macro (in plain.tex). This changes the
\mag parameter so as to scale fonts, skips, etc., and then explicitly
resets \hsize and \vsize using "true" dimensions so that the text
area remains 6.5" x 8.9", but it does NOT touch \hoffset and
\voffset. Nevertheless, The TeXbook tells the reader: "There will be
an inch of margin at both left and right, assuming that the paper is
8 1/2 inches wide." (p.60) This is only true if the default origin is
unaffected by \mag.
JK
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