Check whether the system is set to a Dark Mode style

This checks a global system default. It is intended for headless tools or programs that can't access their windows. It may not be accurate when specific screens or applications have a different theme set. If you control your GUI, please check window-specific properties instead (on macOS that is NSAppearance protocol).

On macOS this crate uses Core Foundation to read a AppleInterfaceStyle global setting, which is equivalent of:

defaults read -g AppleInterfaceStyle

On other platforms only None is returned. Please submit pull requests for more OSes!