Access Mac OS Displays

macOSDisplays.swift

private func getActiveDisplays() -> [CGDirectDisplayID] {
    var displayCount: UInt32 = 0

    // get the number of active displays
    guard CGGetActiveDisplayList(0, nil, &displayCount) == .success else {
        return []
    }
    
    // get the active displays
    let allocated = Int(displayCount)
    let activeDisplays = UnsafeMutablePointer<CGDirectDisplayID>.allocate(capacity: allocated)
    
    guard CGGetActiveDisplayList(displayCount, activeDisplays, &displayCount) == .success else {
        return []
    }
    
    debugPrint("display count: \(displayCount)")
    debugPrint("displays: \(activeDisplays)")
    
    // transform unsafe mutable pointer
    var displays = [CGDirectDisplayID]()
    for i in 0..<allocated {
        let display = activeDisplays[i]
        
        // get display brightness
        let model = CGDisplayModelNumber(display)
        debugPrint("display: \(display), model: \(model)")
        displays.append(display)
    }
    
    // deallocate
    activeDisplays.deallocate(capacity: allocated)
    
    return displays
}