gnuplot-beta

4.4-rc1: sticky x-axis reversal

[Hans-Bernhard B. <HBB...@t-...>]

Hello everyone,

I've just received a bug report from a German-speaking user.  4.4-rc1 
(and current 4.4 branch CVS) both fail on the following script:

set multiplot layout 1,2
plot [2:0] sin(x)
plot [0:2] sin(x)
unset multiplot

The problem is that the axis of the second plot is reversed, too.  Since 
it really only applies for the time of a plot command, specifying an 
inverted axis interval like this shouldn't set the 'reverse' option, but 
it does:

gnuplot> p [2:0] sin(x)
gnuplot> show xr

         set xrange [ * : * ] reverse nowriteback  # (currently 
2.00000:0.00000] )

'set xrange [2:0]' is supposed to have this effect, but a temporary 
override inside a plot command isn't.

Re: 4.4-rc1: sticky x-axis reversal

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

On Thursday 04 March 2010 11:30:59 Hans-Bernhard Bröker wrote:
> Hello everyone,
> 
> I've just received a bug report from a German-speaking user.  4.4-rc1 
> (and current 4.4 branch CVS) both fail on the following script:
> 
> set multiplot layout 1,2
> plot [2:0] sin(x)
> plot [0:2] sin(x)
> unset multiplot
> 
> The problem is that the axis of the second plot is reversed, too. 

Here is the ChangeLog entry for the commit that changed the behaviour:

2007-06-29  Ethan Merritt  <merritt@u.washington.edu>

        * src/axis.c (load_range): Revert change of 2004-03-15. This means
        that we do *not* clear the RANGE_REVERSE flag after applying the
        reversal. This is necessary for the upcoming "refresh" support, but
        also fixes a current bug:
        set xrange [*:*] reverse; plot <foo>;  <zoom; zoom; unzoom>
        flag is now clear, and subsequent plots are drawn backwards

So a simple reversion of the change would re-introduce a bug present in
4.2.anything:  
  zoom/unzoom flips the sign of an axis that was explicitly set to "reverse".

Not to say that this shouldn't be fixed, but it will require more than
simply reverting to the previous code.