I updated the project to work with Xcode 11.3.
This is a demo app I've built as an experiment in using SwiftUI with AppKit, as described in this blog post: https://mackuba.eu/2019/06/17/swiftui-appkit-dark-mode-switcher/.
The app lets you force any other app to use a light mode when the whole desktop uses a dark mode. Unfortunately there doesn't seem to be any way now to do the opposite (use dark mode only in specific apps).
This isn't really a great app, it's mostly useful as sample code - it works pretty slowly because of the constant AutoLayout constraint errors, which I don't know how to fix. So I'm not providing any binaries - if you really want to try it, just download the code and build it.
Copyright © 2019 Kuba Suder. The entire code of the app is licensed under WTFPL License - this is intended to be example code after all, so feel free to take whatever parts you need and use them for anything you need.