Function char_col_for_visual_offset 

pub fn char_col_for_visual_offset(
    line: &str,
    seg: (usize, usize),
    visual_offset: usize,
) -> usize

Inverse of the per-char accounting wrap_segments uses to find where a segment breaks: map a visual x offset (visual_offset, cells counted from the segment’s OWN left edge — i.e. 0 at seg.0, matching how the renderer paints each wrapped row starting at its text area’s left column regardless of seg.0) to the char index within seg = [start, end) it lands on.

Uses the exact same per-char width formula wrap_segments sums to find segment boundaries (char::width().unwrap_or(1).max(1)), so a click that wrap_segments would consider inside this segment resolves to the same character wrap_segments wrapped around. This does NOT reproduce the renderer’s real tab-stop expansion (wrap_segments itself counts a tab as 1 cell, not tabstop cells) — that mismatch predates this function and is wrap_segments’ own documented simplification; mouse click mapping mirrors it for round-trip consistency with the wrap engine rather than inventing a different tab model for wrapped rows.

Clamps to end (one past the segment’s last char) once cumulative width reaches or exceeds visual_offset — vim’s “past EOL on this visual row” landing spot.