When I build SheepShaver in Xcode 10 under Mojave, fonts and graphics look slightly fuzzy compared to the way they look when I build in Xcode 9 under High Sierra. The solution to this seems to be this:

Copy the macOS SDK from a copy of Xcode 9 to the desktop; rename it macOS10.13.SDK; move it into the macOS SDKs folder in Xcode 10. In Xcode 10, change the Base SDK in SheepShaver from "no SDK" to "macOS 10.13." Build. the output will be as sharp as it was under Xcode 9.

The same applies to BasiliskII, presumably.

Out of curiosity, does anyone know if you can use this trick to get XCode 10 to build against older SDKs, like, 10.6?

(and I wonder what Apple's reasoning is for fuzzing things up...?)

You can extract the Command Line Tools or Xcode for older versions of macOS and use xcode-select to make them the active toolchain.

Find them here: https://developer.apple.com/download/more/

Apple has been making quite a few changes to macOS Mojave. Frame pacing is messed up, different layered rendering causes some programs to display blank screens, support for compiling 32-bit is removed...

Thanks! I have yet to figure out how to cleanly build any of my emulation-related projects under the 10.14 SDK. Seems like 10.6 and 10.10 are my go-tos that provide a stable environment, and it'll be nice to be able to build from my host instead of firing up VMs to do the compilations.

If you are trying to build SheepShaver or BasiliskII, one key thing to do is under File, Project Settings, under Build System, switch the option from the default setting to Legacy Build System (or some similar term).

I couldn't build at all in Mojave until kanjitalk755 pointed this out.

My main one is Mini vMac, but that's probably the main problem there as well, now that I think of it.