/// * `letterSpacing`: The amount of space (in logical pixels) to add between each letter.
/// * `wordSpacing`: The amount of space (in logical pixels) to add at each sequence of white-space (i.e. between each word).
/// * `textBaseline`: The common baseline that should be aligned between this text span and its parent text span, or, for the root text spans, with the line box.
/// * `height`: The height of this text span, as a multiple of the font size.
/// * `height`: The height of this text span, as a multiple of the sum of font size and leading.
/// * `leading`: Custom leading to use instead of the font-provided leading as a multiple of font size. When null, default font leading will be used. Leading is the additional spacing between lines.
/// * `locale`: The locale used to select region-specific glyphs.
/// * `background`: The paint drawn as a background for the text.
/// * `foreground`: The paint used to draw the text. If this is specified, `color` must be null.