Word wrap for variable width fonts.

Can provide split lines or positions for each character.

Lines Split

use ttf_parser::Face;
use ttf_word_wrap::{TTFParserMeasure, WhiteSpaceWordWrap, Wrap};

// Load a TrueType font using `ttf_parser`
let font_data = std::fs::read("./test_fonts/Roboto-Regular.ttf").expect("TTF should exist");
let font_face = Face::from_slice(&font_data, 0).expect("TTF should be valid");
let measure = TTFParserMeasure::new(&font_face);

// Set up wrapping options, split on whitespace:
let word_wrap = WhiteSpaceWordWrap::new(20000, &measure);

// Use the `Wrap` trait and split the `&str`
let poem = "Mary had a little lamb whose fleece was white as snow";
let lines: Vec<&str> = poem.wrap(&word_wrap).collect();
assert_eq!(lines[0], "Mary had a little lamb");

Positions for each character

use ttf_parser::Face;
use ttf_word_wrap::{WrapWithPosition, WhiteSpaceWordWrap, TTFParserMeasure, CharPosition,
Position};

// Load a TrueType font using `ttf_parser`
let font_data = std::fs::read("./test_fonts/Roboto-Regular.ttf").expect("TTF should exist");
let font_face = Face::from_slice(&font_data, 0).expect("TTF should be valid");
let measure = TTFParserMeasure::new(&font_face);

// Set up wrapping options, split on whitespace:
let word_wrap = WhiteSpaceWordWrap::new(20000, &measure);

// Use the `Wrap` trait and split the `&str`
let poem = "Mary had a little lamb whose fleece was white as snow";
let positions: Vec<CharPosition> = poem.wrap_with_position(&word_wrap).collect();

// offset is in the unit (em) of the TTFParserMeasure.
// If the font does not have the given char, `CharPosition::Unknown('M')` is returned.
assert!(matches!(positions[0], CharPosition::Known(Position { ch: 'M', line: 0, offset: 0, width: 1788 })));