I want to draw a custom NSWindow that allows me to add subviews even on top of the top bar ( where the traffic light buttons are and the title bar ).
When I use a transparent window and use a custom view to mimic a NSWindow I need to implement so many things by myself that I thought there should be a better way of achieving this.
Apple has two custom window sample projects: RoundTransparentWindow and FunkyOverlayWindow (this one is old, though!). Cocoa With Love has an tutorial article, and be sure to read the article linked at the bottom, about custom drawing in window frames.