title: Round corners on a borderless NSWindow
body: <p>I'm creating an application and <a href="http://www.usabilitypost.com/2010/10/22/no-title-bar/" rel="noreferrer">I don't want a title bar</a>:</p>
  
  <blockquote>
    <p>If the title remains the same all the time, does it make sense to show it? For example, if an app doesn’t show the names of documents, or any other assets that it opens, and there is plenty of space at the top around other controls to grab onto if you want to move the window around, does the title serve much purpose?
    <img src="https://i.stack.imgur.com/C9mTo.png" alt="http://i.stack.imgur.com/C9mTo.png"></p>
  </blockquote>
  
  <p>The problem is: how do I do this? I tried using <code>[mainWindow setStyleMask:NSBorderlessWindowMask];</code> but I can't make it have round corners. I really don't know how to make round corners. Next to that, I can't make it have a resize control. If I use <code>[mainWindow setStyleMask:NSBorderlessWindowMask | NSResizableWindowMask];</code> it's not borderless anymore. Can anyone help me? Thanks.</p>