Function split_line_intervals 

pub fn split_line_intervals<'a>(
    line_len: usize,
    spans: &'a [StyleSpan],
    selection_range: Option<(usize, usize)>,
) -> Vec<StyledSegment<'a>>

Core buffer, syntax, movement, and hook primitives. Computes disjoint, sorted styled segments for a line by splitting across syntax span and selection boundaries.