[XeTeX] c.t.t. post re: \mag

[Andreas Matthias]

Jonathan Kew wrote:

> 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.

Yes, I see. (I didn't try that before posting my original message.)

> With pdfTeX, on the other hand, the origin does move according to  
> \mag, as you noted.

I wasn't aware that this caused controversial discussions before.
I just read the links Bruno and Will posted and the following links
from there. It seems to be a highly emotional topic.

> So there seems to be a discrepancy or incompatibility between the  
> existing engines/paths already. Let the user beware!

So far I used \mag only once to produce a poster. I created the
poster in A3 and then \mag'ed it to A0. In this situation it was
nice that pdftex scaled everything, including the origin and
therefor all margins.

Are there other useful applications for \mag? (I really mean it.
I used \mag just once and didn't need it elsewhere.)

> 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.

Makes much sense.


Ciao
Andreas