Re: exposing cairo context from gnuplot

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

On Thu, 10 Sep 2009, Ethan Merritt wrote:

> On Thursday 10 September 2009 02:34:07 Richard Henwood wrote:
> > there is a useful post provided by the author of the extcairo driver:
> > http://www.mail-archive.com/plp...@li.../msg01273.html
> > and example usage:
> > http://plplot.sourcearchive.com/documentation/5.9.2/ext-cairo-test_8c-source.html
>
> Hmm.
> Their use of the word "external" doesn't match mine, if that's
> an example of it. In the URL you point to, it's just that a
> routine in plplot itself initializes cairo and then passes it to
> the driver.  What we would be looking for is an example of one
> process initializing a cairo context and then passing a handle
> to another process entirely.  Which may or may not be possible -
> I just dont know.

"Back to basics".  The only sort of thing you can literally "pass
to" gnuplot (as an executable program) is a string, as in the argv
array or as part of a "set foo ..." statement.

However, strings can be interpreted in various ways.  If we're
really talking about passing a pre-allocated cairo context to
gnuplot, the only way I can envisage of doing this would be saying
something like

set cairo_t "0x818a400"

(to a hypothetical gnuplot "raw_cairo" terminal).

It seems this would offer (depending on one's black-hat skill
level) a good way of crashing gnuplot or turning it into a
rootkit; but I suppose that in the right hands it could do what
Richard is (I think) talking about -- i.e. get gnuplot to write
into an area of memory rather than a file.

Allin Cottrell