Wt

The example shows that the first WSuggestionPopup appears behind the WDialog.

class MyComboBox : public Wt::WLineEdit
{
public:
  MyComboBox()
  {
    Wt::WSuggestionPopup::Options simpleOptions;
    simpleOptions.highlightBeginTag = "<b>";
    simpleOptions.highlightEndTag = "</b>";
    simpleOptions.listSeparator = 0;

    m_popup = std::make_unique<Wt::WSuggestionPopup>(simpleOptions);
    m_popup->setDropDownIconUnfiltered(true);
    m_popup->forEdit(this, Wt::PopupTrigger::Editing | Wt::PopupTrigger::DropDownIcon);

    m_popup->addSuggestion("Item 1");
    m_popup->addSuggestion("Item 2");
    m_popup->addSuggestion("Item 3");
  }

  std::unique_ptr<Wt::WSuggestionPopup> m_popup;
};

auto layout = std::make_unique<Wt::WVBoxLayout>();
layout->addWidget(std::make_unique<MyComboBox>());

auto dialog = std::make_unique<Wt::WDialog>();

layout->addWidget(std::make_unique<MyComboBox>());

dialog->contents()->setLayout(std::move(layout));
dialog->exec();