Swift implementation to highlight Cocoa UI elements (http://stackoverflow.com/a/25984748/316803)

highlight.swift

NSColor.selectedMenuItemColor().set()
NSRectFillUsingOperation(dirtyRect, .CompositeSourceOver);

if (dirtyRect.size.height > 1) {
    let heightMinus1 = dirtyRect.size.height - 1
    let currentControlTint = NSColor.currentControlTint()
    var startingOpacity: CGFloat = 0.09
    
    if currentControlTint == .BlueControlTint {
        startingOpacity = 0.16
    }
    
    var gradient = NSGradient(startingColor: NSColor(white: CGFloat(1.0), alpha:startingOpacity), endingColor:NSColor(white: CGFloat(1.0), alpha: 0.0))
    let startPoint = NSMakePoint(dirtyRect.origin.x, dirtyRect.origin.y + heightMinus1)
    let endPoint = NSMakePoint(dirtyRect.origin.x, dirtyRect.origin.y + 1)
    gradient.drawFromPoint(startPoint, toPoint: endPoint, options:NSGradientDrawsBeforeStartingLocation)
    
    if currentControlTint == .BlueControlTint {
        NSColor(white: CGFloat(1.0), alpha: CGFloat(0.1)).set()
        
        let smallerRect = NSMakeRect(dirtyRect.origin.x, dirtyRect.origin.y + heightMinus1, dirtyRect.size.width, CGFloat(1.0))
        NSRectFillUsingOperation(smallerRect, .CompositeSourceOver)
    }
}

Thanks! - I tightened it up a bit to remove some vars - https://gist.github.com/orta/cfe35d71b8477ac20d02a4da11e7e0d2