title: How to change the titlebar/toolbar and NSButtons to a dark theme?
body: <p>I am working on a project for macOS (OS X) where I want the window to be set to a dark theme instead of the default light theme, which has a light gray titlebar/toolbar with white buttons. </p>
  
  <p>How can I change the titlebar/toolbar to a black color and the buttons to a dark gray? </p>
  
  <p>I am coding in Swift but an answer in Objective-C would also be helpful. I have attached an image of what I am aiming to make it look like: </p>
  
  <p><a href="https://i.stack.imgur.com/Won9y.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Won9y.png" alt="What I want it to look like"></a></p>