Re: Help needed to update our use of OpenGL

[Pantxo]

Hi,

Yes, among what we use, the so called fixed pipeline is deprecated and won't
be necessarily part of future implementations. At best, those functions will
get no attention and stay there but become more and more buggy without a
hope for a fix.
The GL_FEEDBACK mode, on which we rely for printing, is also deprecated and
I have no hope that e.g. the bug below will get fixed:
https://savannah.gnu.org/bugs/?func=detailitem&item_id=48689

VTK is already using modern OpenGL so it may be worth looking at their code.
For printing, they directly feed gl2ps with primitives they fetched in a
transform feedback buffer(see [1] and [2]).
 
I never programmed anything in modern OpenGL, so I can't really help, but if
such restructuring should happen I'd be happy to discuss the opportunity of
abstracting our current opengl_renderer into something more general, say
base_render. The latter would be "rendering technology agnostic" (actual
drawing and property changes are done in pure virtual functions) and would
serve as a base for the opengl_renderer and eventually for any kind of 2D-3D
renderer someone may want to implement (I was thinking about qt_renderer,
cairo_renderer for 2D printing).

Pantxo

[1] http://www.geuz.org/pipermail/gl2ps/2016/000424.html
[2]
https://www.vtk.org/doc/release/7.1/html/classvtkOpenGLGL2PSHelperImpl.html



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