As you know, The first Witcher game was released for Mac on Steam a few days ago. It runs decently within a Wineskin wrapper, but it has been a polarizing issue for people who believed it should have been a native port rather than a "lazy" wrapped port.
In any case, I've been scouring the Internet for information on this game, and one particular post on the Inside Mac Games Forum stood out. Here is the link to the full post, but I've highlighted the important note here:
The Witcher: Mac Edition is using an older version of the Wineskin engine (WS8 1.3.7), so I swapped out the 1.3.7 engine with the very latest 1.5 engine and performance has improved SIGNIFICANTLY. I mean it.
I thought that was really interesting, so I searched around some more and found a few more links from other forums linking to the same post and asking how to do it. The poster actually went into some detail on the instructions, but assumes some pri