add pangocairo variant for gnuplot

[ejtttje@…]

Adds cairo-based terminals for pdf and png targets. Works around ticket #27892. May also enable features in combination with wxWidgets variant? (wxt terminal: ​http://lwn.net/Articles/224753/)

(Or is Cairo already included in the wxWidgets dependancy? Not sure how the wxWidgets variant is working otherwise.)

[ryandesign (Ryan Carsten Schmidt)]

Is there any reason why we shouldn't just include the pango/cairo dependency in the port proper, and not add a variant -- Is there any reason why users wouldn't want this extra functionality?

[ejtttje@…]

Well Pango/Cairo carry a fair amount of dependencies with them. Further, gnuplot also has interfaces to libpng and pdflib which provide alternate png and pdf functionality, so cairo is kind of superfluous. So my motivation is really just that it's nice to have a backup route, in particular because pdflib is currently broken (or at least the universal build is)...

I haven't tried the wxWidgets angle on this though, not sure if maybe these should be registered as dependencies for that target...

[jpo@…]

+1 to include the cairo dependency in the port (and not as a variant)

<pdf biased> If you have to run gnuplot in heterogeneous systems, and in particular macosx and linux ones, this makes a lot of sense as most common linux distros don't have pdflib-lite in their main repos due to licensing problems. This meant that the gnuplot packages avaialble in their main repos didn't supported the pdf terminal. But more recently, gnuplot 4.4 is able to offer a pdf terminal via the cairo library (pdfcairo), which enables more recent linux distros (e.g. Fedora 14) to ship a gnuplot with a pdf terminal built-in. </pdf biased>

[marix@…]

Cc Me!

[jmroot (Joshua Root)]

r86746