Returns the amount of space to add to the end of a line.
- iOS 7.0+
- macOS 10.11+
- Mac Catalyst 13.0+
- tvOS 9.0+
The layout manager doing the layout.
The index of the glyph at the end of the line.
The proposed line fragment rectangle for the current line.
The line spacing after the current line.
This message is sent while each line is laid out to enable the layout manager delegate to customize the shape of line.