Octave (3.4.0) native graphics on Linux with FLTK 2 and libGL

[John A. Murdie]

I've just built Octave 3.4.0 on 64-bit Slackware Linux 13.1, not having 
built it for a while.  I always seem to have trouble with native 
graphics!  First I tried just './configure', but although our OpenGL 
Mesa (7.8.1) library was found that didn't find FLTK, so I then tried 
'./configure --with-fltk-prefix=/usr' and FLTK was then found - but I 
saw the message:

"configure: WARNING: FLTK does not have OpenGL support.  Native graphics 
will be disabled."

We have 64-bit FLTK 2.2.0 installed - the configuration reporting script 
is fltk2-config.

I appreciate that the Octave developers are working hard to improve and 
extend the program, but I can't find a 'HOWTO' for native graphics 
(though there are several postings in the mailing lists - most recently 
http://octave.1599824.n4.nabble.com/how-to-enable-native-graphics-td2969416.html#a2969547 
- though, alas, the HTML links there are broken).

I wish I had the knowledge to write something for the Octave FAQ answers 
on this subject. Can anyone suggest how I can make progress with 
building Octave 3.4.0 with native graphics, please?