Values for the k attribute controlling the visual style for character edges.
Framework
A value other than k indicates that text should be drawn using an alternative shape for edges of characters. These correspond to text edge styles available with Media Accessibility preferences (see Media Accessibility Function).
let kSpecifies no edge style.
let kSpecifies a raised edge style.
let kSpecifies a depressed edge style.
let kSpecifies a uniform border around the character.
let kSpecifies a drop shadow.