Re: goals for 3.1

[Daniel J Sebald]

Shai Ayal wrote:

> an oct-file is a compiled c++ function file for octave, and is used
> to define octave functions as an alternative to using an m-file with
> the m(?) language. Practically what this means is that the current
> drawnow function just has to be renamed to something more
> gnuplot_specific, (e.g. __gnuplot_drawnow)  and can be used along
> with other drawnow functions ( e.g. __newbackend_drawnow). I propose
> that each figure will have a property named "backend" which can have
> one of several values -- "gnuplot","newbackend", "jhandles", ....).
> Using this value, the appropriate backend will be called, vie the
> appropriate drawnow function to render the figure. This way you can
> have co-existence of many backends, and specifically, we will not 
> have to abandon gnuplot. Each of these back-ends can have specific
> functions, but these functions should not be in core-octave, and
> should be used with care since they would break inter-oparability.

I see.  In theory then, John's code for building the __plot_stream__ fid's and 
opening the pipes could be moved to some cc file called __gnuplot_drawnow__.cc. 
 Rather than __plot_stream__ being part of the figure properties, it could be a 
linked list of (term, __plot_stream__).  Then how about a similar Oct file 
routine __gnuplot_f2s__(term) that returns the associated plot stream?  Those 
two would both need to be .oct files for __gnuplot_f2s__ to access the C++ 
variables inside __gnuplot_drawnow__.oct.

So, bundled in the package would be:

__gnuplot_drawnow__.oct
__gnuplot_f2s__.oct
__gnuplot_version__.m
__gnuplot_close_all__.m    (currently called __go_close_all__.m)
__gnuplot_draw_axes__.m    (currently called __go_draw_axes__.m)
__gnuplot_draw_figure__.m  (currently called __go_draw_figure__.m)

The m-scripts would require minor tweaks.  Pass in the term number and first 
line be

__plot_stream__ = __gnuplot_f2s__(term);
if (__plot_stream__ < -1)
   return;

I replaced the "go" in the files with "gnuplot" because I think, from the 
previous discussion, that there won't ever be a need for __go_draw_figure__ other than for gnuplot.

Now, to switch the graphics engine, would all that is required be to simply 
create an operating system link:

drawnow.oct -> __gnuplot_drawnow__.oct

?

Would that move in the desired direction John?

Dan