Function getSelectedText

packages/core/src/widgets/codeEditor.ts:450–474

(lines: readonly string[], selection: EditorSelection)

 * @returns Selected text
 */
export function getSelectedText(lines: readonly string[], selection: EditorSelection): string {
  const [start, end] = normalizeSelection(selection);

  if (start.line === end.line) {
    const line = lines[start.line] ?? "";
    return line.slice(start.column, end.column);
  }

  const result: string[] = [];

  // First line
  const firstLine = lines[start.line] ?? "";
  result.push(firstLine.slice(start.column));

  // Middle lines
  for (let i = start.line + 1; i < end.line; i++) {
    result.push(lines[i] ?? "");
  }

  // Last line
  const lastLine = lines[end.line] ?? "";
  result.push(lastLine.slice(0, end.column));

  return result.join("\n");
}

/**
 * Compute scroll position to ensure cursor is visible.