Method undo

test/MockEditorInterface.cpp:608–617

}

void MockEditorInterface::undo() {
  auto doc = active_document();
  if (!doc)
    return;
  // For now redo is not supported
  if (!doc->past.empty()) {
    doc->cur = doc->past.back();
    doc->past.pop_back();
  }
}

bool MockEditorInterface::is_line_visible(TextPosition /*line*/) const {
  return true;