Function splitAtVisual

internal/app/render.go:252–284

--- ANSI-aware string splicing ------------------------------------- splitAtVisual cuts `s` at visible cell column `col`. CSI escape sequences (`\x1b[...{letter}`) are passed through unchanged and don't count toward `col`.

(s string, col int)

// sequences (`\x1b[...{letter}`) are passed through unchanged and don't
// count toward `col`.
func splitAtVisual(s string, col int) (string, string) {
	visible := 0
	i := 0
	for i < len(s) {
		if s[i] == '\x1b' && i+1 < len(s) {
			j := i + 2 // skip ESC + next byte (usually '[')
			for j < len(s) {
				ch := s[j]
				if (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') {
					j++
					break
				}
				j++
			}
			if j <= len(s) {
				i = j
				continue
			}
			break
		}
		if visible >= col {
			break
		}
		_, size := utf8Decode(s[i:])
		if size == 0 {
			i++
			continue
		}
		i += size
		visible++
	}
	return s[:i], s[i:]
}

// visibleWidth returns the visible-cell width of a string, ignoring CSI.
func visibleWidth(s string) int {