Function draw_vertical_line_at_time 

pub(crate) fn draw_vertical_line_at_time(
    time: &BigInt,
    ctx: &mut DrawingContext<'_>,
    stroke: impl Into<Stroke>,
    max_timestamp: &BigInt,
    viewport: &Viewport,
    time_offset: &BigInt,
)

Draw a vertical line at the given time with the specified stroke.