I think if an ebuild links to a library, then it should be included as a dependency - unlisted dependencies can lead to chaos. There is a projectM plugin included in media-plugins/audacious-plugins-1.3.0_alpha2, which is compiled if libprojectm-0.99 is present. I added libprojectm as a conditional dependency: If the opengl USE flag is set, audacious-plugins-1.3.0_alpha2-r1 will depend on libprojectm.
Created attachment 108130 [details] audacious-plugins-1.3.0_alpha2-r2.ebuild
It can't be conditional if there's no way to disable the feature in configure; you can't just add a flag and do nothing with it but adding dependencies. http://www.gentoo.org/proj/en/qa/automagic.xml
-alpha2 is no longer current, any development will happen on the -alpha3 ebuild. I will see whenever projectm can be controlled conditionally. If not, I'll add it upstream. In that case, you'll have to wait until alpha4 or the final version comes out before this bug can be resolved. I will not apply patches to developer releases as they are too short-lived in nature.
Created attachment 108136 [details] audacious-plugins-1.3.0_alpha2-r2.ebuild (fixed) Thanks for the correction, the projectm plugin CAN be disabled in configure, so I added a few lines to disable it in case of building with USE="-opengl". This way it's a real conditional dependency.
This is in the alpha4 ebuild. Please note that I have used use_enable instead of the old-style if-statement. Although functionally equivalent, I hope you agree that this is much more readable. Thank you for your bug report :)
