public bool Underline { get; set; } = false;
public float UnderlineStrokeWidth { get; set; } = 1;
public float UnderlineOffset { get; set; } = 2f;

if (LabelStyle.RTLSupport)
{
    using (var shaper = new SKShaper(paint.Typeface))
    {
        float shapedWidth = shaper.Shape(lines[i], paint).Width;
        canvas.DrawShapedText(shaper, lines[i], xPx, yPx, paint);

        if (Underline)
        {
            float underlineY = yPx + UnderlineOffset;

            using var underlinePaint = new SKPaint
            {
                Color = paint.Color,
                StrokeWidth = UnderlineStrokeWidth,
                IsStroke = true,
                IsAntialias = paint.IsAntialias
            };

            canvas.DrawLine(xPx, underlineY, xPx + shapedWidth, underlineY, underlinePaint);
        }
    }
}
else
{
    canvas.DrawText(lines[i], xPx, yPx, paint);

    if (Underline)
    {
        float underlineY = yPx + UnderlineOffset;
        float textWidth = paint.MeasureText(lines[i]);

        using var underlinePaint = new SKPaint
        {
            Color = paint.Color,
            StrokeWidth = UnderlineStrokeWidth,
            IsStroke = true,
            IsAntialias = paint.IsAntialias
        };
        canvas.DrawLine(xPx, underlineY, xPx + textWidth, underlineY, underlinePaint);
    }
}

public bool LabelUnderline { get => LabelStyle.Underline; set => LabelStyle.Underline = value; }
public float LabelUnderlineStrokeWidth { get => LabelStyle.UnderlineStrokeWidth; set => LabelStyle.UnderlineStrokeWidth = value; }
public float LabelUnderlineOffset { get => LabelStyle.UnderlineOffset; set => LabelStyle.UnderlineOffset = value; }