pub fn prepare(

        text: &str,

        font: &Font,

        size: Figure<f32, Scaled>,

        color: Color,

        scene: &Target,

    ) -> PreparedSpan {

        let size_in_pixels = size.to_pixels(scene.scale());

        let characters = text.chars().collect::<Vec<_>>();

        let mut caret = Figure::new(0.);

        let mut glyphs = Vec::with_capacity(characters.len());

        let mut last_glyph_id = None;

        for (source_offset, &c) in characters.iter().enumerate() {

            let base_glyph = font.glyph(c);

            if let Some(id) = last_glyph_id.take() {

                caret += Figure::new(font.pair_kerning(size_in_pixels.get(), id, base_glyph.id()));

            }

            last_glyph_id = Some(base_glyph.id());

            let glyph = base_glyph

                .scaled(Scale::uniform(size_in_pixels.get()))

                .positioned(rusttype::point(caret.get(), 0.0));

            caret += Figure::new(glyph.unpositioned().h_metrics().advance_width);

            glyphs.push(GlyphInfo {

                source_offset,

                source: c,

                glyph,

            });

        PreparedSpan::new(

            font.clone(),

            size_in_pixels,

            color,

            caret,

            characters,

            glyphs,

            font.metrics(size_in_pixels),

        )

    }