Re: bug in terminals affected by 'set size'

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

On Tuesday 04 October 2005 12:54 pm, Don Taber wrote:
> > > Various terminals the size of whose output can be changed with
> > > 'set size' have a bug in current cvs.  When the size is increased
> > > by setting the size with factors greater than one, 
> > 
> > So don't do that.
> > 
> 
> It's not that easy for several reasons.
> 
> 1. This resizing technique *used* to work and there are scripts out there
> (some of which are mine) that rely on it.

Several of gnuplot's terminal drivers have been entirely replaced
or re-written, for good reason.  I can believe that the old (5 years+)
png driver used to behave differently, but it's now dead and buried.


> 2. For 'set term pbm' there is no size argument and a subsequent
> 'set size' command is the only way to change the size.  Try
> 'help set term pbm' and you will find that you are advised to
> use size > 1. 

OK. So let's fix the pbm terminal. That sounds easy.

> 3. For other terminals, the documentation specifically states
> that the size may be changed with 'set size'.  No warning that
> size > 1 won't work.  

That also can be fixed.

> And it still *does* work for the plots.   
> It is only reasonable that it should work for the labels too.

I can assure you that it does not work reliably (in the sense
of working for all terminals) for the plots either.

> I did not try to fix this myself because I am not sufficiently
> familiar with the terminal driver code.  But my suspicion
> is that it would be easier to restore the previous behavior
> than to fix all the documentation to reflect the new behavior.

No. It is not fixable in either png or pdf drivers, since it is
the underlying library rather than any gnuplot code that causes
a problem.  pdflib in particular is ridiculously prone to segfaults
if you try to draw or write outside of the pre-defined plot
boundaries.  I have not looked in detail at other drivers, but 
I think it's only luck that size>1 ever worked.

My [one] vote would be to fix the terminal drivers that have no
separate size option, and then limit the global size parameter
to the range 0<size<1.


-- 
Ethan A Merritt       merritt@u.washington.edu
Biomolecular Structure Center
Mailstop 357742
University of Washington, Seattle, WA 98195