Returns the range of characters originally requested to fill the frame.
- iOS 3.2+
- macOS 10.5+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
- Core Text
The frame whose character range is returned.
CFRange structure containing the backing store range of characters that were originally requested to fill the frame, or, if the function call is not successful, an empty range.