Function hit_test_line 

pub fn hit_test_line<F>(
    click_pos: Pos2,
    values: &[f64],
    visible_range: Range<usize>,
    coords: &ChartMapping,
    price_to_y: F,
    tolerance: f32,
) -> Option<SeriesHitResult>
where
    F: Fn(f64) -> f32,

Hit test a line series