/// Creates a new <see cref="FontUsage"/> by applying adjustments to this <see cref="FontUsage"/>.
/// </summary>
/// <param name="usage">The base <see cref="FontUsage"/>.</param>
/// <param name="typeface">The font typeface. If null, the value is copied from this <see cref="FontUsage"/>.</param>
/// <param name="size">The text size. If null, the value is copied from this <see cref="FontUsage"/>.</param>
/// <param name="weight">The font weight. If null, the value is copied from this <see cref="FontUsage"/>.</param>
/// <param name="italics">Whether the font is italic. If null, the value is copied from this <see cref="FontUsage"/>.</param>
/// <param name="fixedWidth">Whether all characters should be spaced apart the same distance. If null, the value is copied from this <see cref="FontUsage"/>.</param>