property OnFormFieldEnter;
Fired when the form-fill engine gains focus on a form field.
Use to highlight the field in your own UI or to log form interaction analytics.
Wraps the corresponding PDFium API and exposes it as a TPdf instance member so consumers do not have to manage FPDF_DOCUMENT handles directly.
Pdf1.Active before calling page-scoped operations; methods that require an open document raise EPdfError otherwise.SaveToFile to persist.
procedure TForm1.PdfOnFormFieldEnter(Sender: TObject);
begin
// react to OnFormFieldEnter
end;