Adds the outline attribute to the selected text attributes if absent; removes the attribute if present.
The control that sent the message; may be nil.
If there is a selection and the first character of the selected range has a non-zero stroke width, or if there is no selection and the typing attributes have a non-zero stroke width, then the stroke width is removed; otherwise the value of NSStrokeWidthAttributeName is set to the default value for outline (3.0).
Operates on the selected range if the receiver contains rich text. For plain text the range is the entire contents of the receiver.