Check whether active window is in fullscreen mode on macOS / Cocoa

gistfile1.txt

/// Check whether active window is in fullscreen mode.
/// - Parameter processIdentifier: the pid given by "NSWorkspace.shared.frontmostApplication?.processIdentifier"
/// - Returns: true if fullscreen, false if windowed
func isFullScreen(processIdentifier: pid_t) -> Bool {
    if let winArray: CFArray = CGWindowListCopyWindowInfo(.excludeDesktopElements, kCGNullWindowID) {
        for i in 0..<CFArrayGetCount(winArray) {
            if let window: [String : Any] = unsafeBitCast(CFArrayGetValueAtIndex(winArray, i), to: CFDictionary.self) as? [String : Any] {
                if let pid = window["kCGWindowOwnerPID"] as? Int32 {
                    if pid == processIdentifier {
                        if let bounds: [String : Any] = window["kCGWindowBounds"] as? [String : Any], let boundsWidth = bounds["Width"] as? CGFloat, let boundsHeight = bounds["Height"] as? CGFloat {
                            if boundsWidth == NSScreen.main?.frame.width && boundsHeight == NSScreen.main?.frame.height {
                                return true
                            }
                        }
                    }
                }
            }
        }
    }
    return false
}