If the text range has a length, it indicates the currently selected text. If it has zero length, it indicates the caret (insertion point). If the text-range object is nil, it indicates that there is no current selection.
A Boolean value that indicates whether the range of text represented by the receiver is zero-length.
This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.