Flashing the screen in Swift. Sticking this here because it took me a while to work out the right variable types and casting.

flashScreen.swift

 func flashScreen() {
        let inDuration: CGDisplayFadeInterval = 0.0
        let outDuration: CGDisplayFadeInterval = 1.0
        let color = NSColor.white

        var fadeToken: CGDisplayFadeReservationToken = 0
        let colorToUse = color.usingColorSpaceName(NSColorSpaceName.calibratedRGB)!
        let err = CGAcquireDisplayFadeReservation(inDuration + outDuration, &fadeToken)
        
        if err != CGError.success {
            DDLogError("Error acquiring fade reservation")
            return
        }
        
        CGDisplayFade(fadeToken, inDuration,
                      0.0 as CGDisplayBlendFraction, 0.2 as CGDisplayBlendFraction,
                      Float(colorToUse.redComponent), Float(colorToUse.greenComponent), Float(colorToUse.blueComponent),
                      boolean_t(1))
        CGDisplayFade(fadeToken, outDuration,
                      0.2 as CGDisplayBlendFraction, 0.0 as CGDisplayBlendFraction,
                      Float(colorToUse.redComponent), Float(colorToUse.greenComponent), Float(colorToUse.blueComponent),
                      boolean_t(1))
    }