Function split_into_lines_fontdue 

pub fn split_into_lines_fontdue<F: Fn(usize) -> Pt>(
    txt: &str,
    font: &Font,
    font_size: f32,
    max_width: F,
    cache: &mut HashMap<char, f32>,
) -> Vec<(String, f32)>

Uses the fontdue text rasterizer to split text into lines less than the max_width