Forces the receiver to generate glyphs for the specified character range, if it has not already done so.
- iOS 7.0+
- macOS 10.5+
- tvOS 9.0+
The character range for which glyphs are generated.
The layout manager reserves the right to perform glyph generation for larger ranges. If noncontiguous layout is disabled, then the affected range is always effectively extended to start at the beginning of the text.