Function decodeKittyPrintable

packages/pi-tui/src/keys.ts:1349–1382

(data: string)

 * @returns The printable character, or undefined if not a printable CSI-u sequence
 */
export function decodeKittyPrintable(data: string): string | undefined {
	const match = data.match(KITTY_CSI_U_REGEX);
	if (!match) return undefined;

	// CSI-u groups: <codepoint>[:<shifted>[:<base>]];<mod>[:<event>]u
	const codepoint = Number.parseInt(match[1] ?? "", 10);
	if (!Number.isFinite(codepoint)) return undefined;

	const shiftedKey = match[2] && match[2].length > 0 ? Number.parseInt(match[2], 10) : undefined;
	const modValue = match[4] ? Number.parseInt(match[4], 10) : 1;
	// Modifiers are 1-indexed in CSI-u; normalize to our bitmask.
	const modifier = Number.isFinite(modValue) ? modValue - 1 : 0;

	// Only accept printable CSI-u input for plain or Shift-modified text keys.
	// Reject unsupported modifier bits (e.g. Super/Meta) to avoid inserting
	// characters from modifier-only terminal events.
	if ((modifier & ~KITTY_PRINTABLE_ALLOWED_MODIFIERS) !== 0) return undefined;
	if (modifier & (MODIFIERS.alt | MODIFIERS.ctrl)) return undefined;

	// Prefer the shifted keycode when Shift is held.
	let effectiveCodepoint = codepoint;
	if (modifier & MODIFIERS.shift && typeof shiftedKey === "number") {
		effectiveCodepoint = shiftedKey;
	}
	effectiveCodepoint = normalizeKittyFunctionalCodepoint(effectiveCodepoint);
	// Drop control characters or invalid codepoints.
	if (!Number.isFinite(effectiveCodepoint) || effectiveCodepoint < 32) return undefined;

	try {
		return String.fromCodePoint(effectiveCodepoint);
	} catch {
		return undefined;
	}
}

function decodeModifyOtherKeysPrintable(data: string): string | undefined {
	const parsed = parseModifyOtherKeysSequence(data);