Function sliceWithWidth

packages/pi-tui/src/utils.ts:1088–1133

(
	line: string,
	startCol: number,
	length: number,
	strict = false,
)

/** Like sliceByColumn but also returns the actual visible width of the result. */
export function sliceWithWidth(
	line: string,
	startCol: number,
	length: number,
	strict = false,
): { text: string; width: number } {
	if (length <= 0) return { text: "", width: 0 };
	const endCol = startCol + length;
	let result = "",
		resultWidth = 0,
		currentCol = 0,
		i = 0,
		pendingAnsi = "";

	while (i < line.length) {
		const ansi = extractAnsiCode(line, i);
		if (ansi) {
			if (currentCol >= startCol && currentCol < endCol) result += ansi.code;
			else if (currentCol < startCol) pendingAnsi += ansi.code;
			i += ansi.length;
			continue;
		}

		let textEnd = i;
		while (textEnd < line.length && !extractAnsiCode(line, textEnd)) textEnd++;

		for (const { segment } of graphemeSegmenter.segment(line.slice(i, textEnd))) {
			const w = graphemeWidth(segment);
			const inRange = currentCol >= startCol && currentCol < endCol;
			const fits = !strict || currentCol + w <= endCol;
			if (inRange && fits) {
				if (pendingAnsi) {
					result += pendingAnsi;
					pendingAnsi = "";
				}
				result += segment;
				resultWidth += w;
			}
			currentCol += w;
			if (currentCol >= endCol) break;
		}
		i = textEnd;
		if (currentCol >= endCol) break;
	}
	return { text: result, width: resultWidth };
}

// Pooled tracker instance for extractSegments (avoids allocation per call)
const pooledStyleTracker = new AnsiCodeTracker();