For gaming, I'd generally recommend using wine-staging, since it is more bleeding-edge and includes some GPU-related features wine currently does not have.
I run wine-staging 2.8 on -current without any problems.
For the full feature-set of wine-staging you need:
- Multilib from AlienBOB including all of his converted -compat32 packages
- OpenAL (32bit and 64bit version)
- converted -compat32 packages that AlienBOB does not provide in his repo - you can get the i486 versions from packages.slackware.com and convert them with convertpkg-compat32 before installing. As of now, these packages are:
at-spi2-atk-compat32
at-spi2-core-compat32
gtk+3-compat32
libunistring-compat32
After you've got everything built, test again with Witcher 3.
Edit: Put my SlackBuild for wine-staging
up here.
Edit #2: To get rid of the preloader errors you need to create/edit /etc/sysctl.conf and add the line:
vm.mmap_min_addr = 0