1. I know this may seem odd (especially as I'm the one who submitted the original ebuild, a few years back) but AFAICT fireflies 2.06 does not depend on fltk, and does not need all those fltk-config options passed to it. (At least: it compiles and works fine without fltk installed and the fltk options removed from the ebuild) 2. the --with-configdir=/usr/share/xscreensaver/config/ option should be --with-confdir 3. I don't think "dobin add-screensaver" and the related pkg_postinst message are needed, as xscreensaver will pick up on the existence of fireflies from its xscreensaver config file. I will post an ebuild patch.
Created attachment 64464 [details, diff] fireflies-2.06-r1.ebuild.patch
fixed. thanks for the patch