Re: pngcairo: suggestion for additional option

[Ethan A M. <merritt@u.washington.edu>]

On Wednesday 19 December 2007 08:16, Allin Cottrell wrote:
> I'm attaching a new .tgz file with 3 small patches, to 
> term/cairo.trm, src/eval.c and src/term_api.h.  Jointly these 
> implement the writing of plot pixel bounds, with a possible scale 
> factor, using a new scalar variable rather than a new function 
> pointer.

I like the idea, but unfortunately this code isn't working.
If you look closely, you will find that the y coordinates being
reported by this code are off by 17 pixels in the default 640x480
ouput from either 'set term png' or 'set term pngcairo'.  This is
because the coordinate mapping is more complicated. In the case of
the png terminal:
     Y(coord) = (term->ymax - coord)

Other terminals, particularly postscript, are more complicated yet.
Postscript has to deal with landscape/portrait mode as well as
bounding box offsets. I suspect that the only way to do this properly
is to have each terminal report its own mapping.

As an aside, I realized while looking at the patch code that aside
from scaling these numbers are already available as
   axis_array[FIRST_X_AXIS].term_lower
   axis_array[FIRST_X_AXIS].term_upper
and so on.

	Ethan

-- 
Ethan A Merritt