Re: support for advanced gnuplot features (was: Plotting semi-trasnparent patches?)

[John W. Eaton]

On 26-Jan-2009, Ben Abbott wrote:

| I agree, we are missing the checkout date, but I'm not sure about checking 
for it. As it would only be useful for developers of octave/gnuplot, I think it 
is safe to assume those running 4.3 (developers sources) are able to keep their 
gnuplot up to date.
| 
| >I think we should require the most recent release version of gnuplot
| >(4.2.4) for the octave development tree. If we can *safely* determine
| >features of the gnuplot development tree (4.3), those could be supported
| >too. But I would do this on case-by-case basis.
| 
| My understanding is that 4.2.4 is required for the developers sources ... 
4.2.3 will work but not display 3D plots correctly with shading("interp").
| 
| >I think it is o.k. to require for a new octave release the most recent
| >release of gnuplot (4.2.4 at the moment). But others might see this
| >different.
| >
| >Kai
| 
| I'd also like see the conditional support for these improvements (figure 
position and facealpha) added to the gnuplot backend.
| 
| Is there a reason why we wouldn' t want to do that?

I think it would be best to check for individual features, not version
numbers.  Even if you can't find a reliable way to check for features,
please consider writing something like this in the code that needs to
do different things depending on what features are available:

  if (gnuplot_has_foobar ())
    ...
  else
    ...
  endif

  ...

  function retval = gnuplot_has_foobar ()
    persistent retval = compare_versions (__gnuplot_version__ (), "4.2.2", 
">=");
  endfunction


This way I think it will be easier to read the code, and simpler to
remove specific checks when/if it is safe to assume that everyone will
have a version of gnuplot that supports a given feature.

jwe