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

[Ben Abbott]

On Jan 27, 2009, at 2:19 AM, Daniel J Sebald wrote:

> John W. Eaton wrote:
>> 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.
>
> Good idea.  Were you thinking to make it generic, like:
>
> gnuplot_has_feature('xyz')
>
> so there is only one function rather than possibly many?  If there  
> were some feedback, one could even send a test script over to  
> gnuplot to check whether is understand a particular syntax.
>
> Dan

I see value in both suggestions. I've tried to merge both into one  
function.

The function, __gnuplot_has_feature__(), supports four conditional  
gnuplot features I'm aware of.

	"x11_respects_figure_position" - to be used in gnuplot_drawnow.m

	"transparency_of_patches" - to be used in __go_draw_axes__.m

	"epslatex_implies_eps_filesuffix": conditional exists in print.m

	"epslatexstandalone_terminal": conditional exists in print.m

A changeset is attached.

Ben

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