Re: exposing cairo context from gnuplot

[Allin C. <cot...@wf...>]

On Tue, 8 Sep 2009, Richard Henwood wrote:

> On Mon, 2009-09-07 at 17:49 -0400, Allin Cottrell wrote:
> > On Mon, 7 Sep 2009, Ethan Merritt wrote:
> >
> > > On Monday 07 September 2009, Richard Henwood wrote:
> > > > Hi All,
> > > >
> > > > I've been using Cairo (cairographics.org) a fair bit recently. I have
> > > > not found a plotting library which is as mature as gnuplot.
> > > >
> > > > I understand that the wxWidgets terminal uses cairo.
> > > >
> > > > Has anyone considered the possibility of exposing the cairo context from
> > > > within gnuplot/wxWidgets to the outside world?
> > >
> > > The development version has two new drivers - pngcairo and pdfcairo,
> > > the use the cairo library.  Not sure if that's what you meant.
> > > Both drivers will be in the version 4.4 release candidate, which I
> > > hope we can put out soonish.
> >
> > I think what Richard was asking is whether the "cairo drawing
> > context" struct, or "cairo_t", that is used internally by gnuplot
> > could somehow be exposed programmatically.  But I don't see how
> > this could be done -- seems to me it would require building
> > gnuplot as a library, not a stand-alone executable.
> >
>
> This is indeed what I am curious about. As you comment: if the
> 'cairo drawing context' was exposed, it would then allow gnuplot
> to behave as a library. i.e. if one was writing a cairo widget
> for a (typically GTK) application, one may create a context
> (cairo_t), pass it to gnuplot (along with some commands to plot
> a graph on it), and then return it to the application for
> display.

I agree this would be very nice, but I'd put the conditionality
the other way round: if it were possible to build gnuplot as a
library, then it would be feasible to expose the relevant cairo_t
via a suitable API.

There are many programs that use gnuplot in "slave" mode and
having a "libgnuplot" would be very useful in that context.  But
so far as I know (Ethan can correct me if I'm wrong) this is not
on an active TODO list.

However, gnuplot's GPVAL* variables, which provide a means of
accessing internal data in text form, can be quite helpful if your
program functions as a "driver" of gnuplot.

Allin Cottrell