Function checkIsTerminalField

src/document/forms/field-tree.ts:265–298

* Check if a field dictionary represents a terminal field. * * A field is terminal if: * - It has no /Kids, OR * - Its /Kids contain widgets (no /T) rather than child fields (have /T)

(dict: PdfDict, registry: ObjectRegistry)

 * - Its /Kids contain widgets (no /T) rather than child fields (have /T)
 */
function checkIsTerminalField(dict: PdfDict, registry: ObjectRegistry): boolean {
  const resolve = registry.resolve.bind(registry);
  const kids = dict.getArray("Kids", resolve);

  if (!kids || kids.length === 0) {
    return true;
  }

  // Check the first kid - if it has /T, these are child fields (non-terminal)
  // If it has no /T, these are widgets (terminal)
  let firstKid = kids.at(0);

  if (!firstKid) {
    return true;
  }

  let firstKidDict: PdfDict | null = null;

  if (firstKid instanceof PdfRef) {
    firstKid = registry.resolve(firstKid) ?? undefined;
  }

  if (firstKid instanceof PdfDict) {
    firstKidDict = firstKid;
  }

  if (!firstKidDict) {
    return true;
  }

  // If first kid has /T, it's a child field → parent is non-terminal
  // If first kid has no /T, it's a widget → parent is terminal
  return !firstKidDict.has("T");
}