How to Mask Multiple Keys in Swift 3

When you need to use CGEvent to create Quartz Event to mimic keyboard input for your macOS program, if you need to mimic the function of shift, control, command, option, then you need to set flag for CGEvent instance’s flag property. Meanwhile, if you want to set more than one flag, then you should or the rawvalue of flag together.

The example is shown here:

let opt1d = CGEvent(keyboardEventSource: src, virtualKey: kVK_Option), keyDown: true)
let opt1u = CGEvent(keyboardEventSource: src, virtualKey: kVK_Option), keyDown: false)
let opt2d = CGEvent(keyboardEventSource: src, virtualKey: kVK_Command), keyDown: true)
let opt2u = CGEvent(keyboardEventSource: src, virtualKey: kVK_Command), keyDown: false)
let opt3d = CGEvent(keyboardEventSource: src, virtualKey: kVK_ANSI_D), keyDown: true)
let opt3u = CGEvent(keyboardEventSource: src, virtualKey: kVK_ANSI_D), keyDown: false)

var flagRaw : UInt64 = 0

switch keys[0] {
    case "kVK_Command":
        flagRaw = CGEventFlags.maskCommand.rawValue
    case "kVK_Shift":
        flagRaw = CGEventFlags.maskShift.rawValue
    case "kVK_Control":
        flagRaw = CGEventFlags.maskControl.rawValue
    case "kVK_Option":
        flagRaw = CGEventFlags.maskAlternate.rawValue
    default:
        break
    }
switch keys[1] {
    case "kVK_Command":
        opt3d?.flags = CGEventFlags(rawValue: CGEventFlags.maskCommand.rawValue | flagRaw)
    case "kVK_Shift":
        opt3d?.flags = CGEventFlags(rawValue: CGEventFlags.maskShift.rawValue | flagRaw)
    case "kVK_Control":
        opt3d?.flags = CGEventFlags(rawValue: CGEventFlags.maskControl.rawValue | flagRaw)
    case "kVK_Option":
        opt3d?.flags = CGEventFlags(rawValue: CGEventFlags.maskAlternate.rawValue | flagRaw)
    default:
        break
}

opt1d?.post(tap: loc)
opt2d?.post(tap: loc)
opt3d?.post(tap: loc)
opt3u?.post(tap: loc)
opt2u?.post(tap: loc)
opt1u?.post(tap: loc)