NSWindow screenshot, best method found (objc)

NSView+Screenshot.m

// ref: https://stackoverflow.com/a/22967912/344591

@implementation NSView (Screenshot)
  
/// Returns an image that contains the entire window contents, including window background color and traffic lights.
/// Resembles the product of taking a screenshot using Preview.app
- (NSImage *)screenshotOfWindow {
    CGWindowID winID = (CGWindowID) self.window.windowNumber;
    CGImageRef ref = CGWindowListCreateImage(CGRectNull, kCGWindowListOptionIncludingWindow, winID, kCGWindowImageBoundsIgnoreFraming);
    return [[NSImage alloc] initWithCGImage:ref size:self.bounds.size];
}

@end