WebKit is the engine behind Safari on both MacOS and iOS, and the open source project is no secret why it goes without saying that it will eventually point to future iOS and macOS features. The new code, which was implemented in March 2018, according to Guilherme Rambo, seems to indicate that macOS will receive a kind of system-wide darkmode as of 10.14.
The code in question was developed to portray a web site Adapt WebKit to the appearance of the application. This refers to the way macOS can change the appearance of UI components, such as buttons, based on system-provided assets.
Since El Capitan there is already a “darkmode” on macOS, which is only used if the app developer decides to use it explicitly. The user can not activate it system-wide and expect all apps to obey. Apple now seems to be working on a way that can change the look of applications globally. According to Guilherme Rambo, dark mode is the most likely reason for such an API.
Unfortunately, he could not find similar references for iOS 12. Would you like to have a DarkMode in iOS and macOS that affects all applications? Let us know in the comments section of the article or on Facebook.