Re: Bug in image code ?

[Daniel J S. <dan...@ie...>]

Ethan Merritt wrote:
> On Thursday 18 August 2005 10:26 am, Daniel J Sebald wrote:
> 
>>You agree that PostScript should be allowed to have negative numbers for 
>>an image location then?  
> 
> 
> The PostScript language itself allows negative numbers, if that's what you're
> asking.

Yeah, I suppose that is why I used a %d rather than a %u in the fprintf() for the PostScript driver.  If the core only sends "small" unsigned numbers, having %d there shouldn't hurt anything.

> Whether the gnuplot core routines should ever send negative coordinates
> to a terminal driver is a rather different question.

Actually it is a rather similar question.  As far as a frame of reference, it seems to me that when laying out a plot (as with drawing on a piece of paper) you want to leave room on all sides to work with.  The following would be equivalent:

1) allow signed coordinates, choose plot area origin near 0
2) allow unsigned coordinates, choose plot area origin way out (halfway?) in the allowable number range

By going with option 2 and then setting axis_array[axis].term_lower to zero in the following formula

#define AXIS_MAP(axis, variable)        \
 (int) ((axis_array[axis].term_lower)        \
     + ((variable) - axis_array[axis].min)    \
     * axis_array[axis].term_scale + 0.5)

it is like starting a drawing on the corner edge of one's piece of paper.

Dan