Wt

This happens when the call to display comes from the server.

Application::Application(const Wt::WEnvironment& env)
  : Wt::WApplication(env)
{
  auto le = root()->addWidget(std::make_unique<Wt::WLineEdit>());
  auto button = root()->addWidget(std::make_unique<Wt::WPushButton>("Show popup"));

  Wt::WSuggestionPopup::Options simpleOptions;
  simpleOptions.highlightBeginTag = "<b>";
  simpleOptions.highlightEndTag = "</b>";
  simpleOptions.listSeparator = 0;

  auto popup = root()->addChild(std::make_unique<Wt::WSuggestionPopup>(simpleOptions));
  popup->addSuggestion("one");
  popup->setDropDownIconUnfiltered(true); // commenting out avoids the error
  popup->forEdit(le, Wt::PopupTrigger::Editing | Wt::PopupTrigger::DropDownIcon);

  button->clicked().connect([=]() { popup->showAt(le); });
}