QToolButton with QMenu stops working after switching tabs (QWebEngineView involved)

soumyaniljana

Hi, everyone,
I'm working on a Qt6/C++ Qt Widgets application using QMainWindow and QTabWidget.

One tab embeds a QWebEngineView (in a tab named "Browser").
Another tab (called "Vocabulary") displays custom CardWidgets.
Each of which includes a QToolButton with a QMenu.

Issue:
When the app starts (the Vocabulary tab is active), everything works fine — the menu shows as expected when the button is clicked.
But after I switch to the Browser tab (with QWebEngineView) and then return to Vocabulary, the QToolButton click is detected but the menu no longer appears.
There are no crashes or warnings, and the QToolButton is still visible and responsive — just no menu.

CardWidget constructor snippet:

CardWidget::CardWidget(const QVariantList& data, QWidget *parent)
    : QWidget(parent), expanded(false), currentRating(0)
{
    this->id = data[0].toInt();
    this->word = data[1].toString();
    setCursor(Qt::PointingHandCursor); // Cursor on hover
    setStyleSheet(R"(
        QWidget {
            border: 1px solid transparent;
            border-radius: 8px;
            padding: 8px;
        }
        QWidget:hover {
            border: 2px solid #3498db;
        }
    )");

    QVBoxLayout* mainLayout = new QVBoxLayout(this);

    // Top Layout
    QHBoxLayout* topLayout = new QHBoxLayout();
    titleLabel = new QLabel(data[1].toString());
    titleLabel->setStyleSheet("font-weight: bold; font-size: 16px;");
    topLayout->addWidget(titleLabel);

    menuButton = new QToolButton();
    menuButton->setText("⋮");
    menuButton->setPopupMode(QToolButton::InstantPopup);
    menuButton->installEventFilter(this);

    QMenu* menu = new QMenu();
    QAction* editAction = menu->addAction("Edit");
    QAction* deleteAction = menu->addAction("Delete");
    menuButton->setMenu(menu);
    menuButton->setFocus();
    topLayout->addWidget(menuButton);

    connect(editAction, &QAction::triggered, this, [this](){
        emit CardWidget::editRequested(this->id);
    });
    connect(deleteAction, &QAction::triggered, this, [this](){
        emit CardWidget::deleteRequested(this->id);
    });

    mainLayout->addLayout(topLayout);

    // Expandable area
    expandableArea = new QWidget();
    QVBoxLayout* expandLayout = new QVBoxLayout(expandableArea);

    QStringList labels = { "Part of Speech", "Meaning", "Example", "Synonyms", "Antonyms", "Notes" };
    for (int i = 2; i < 8 && i < data.size(); ++i) {
        QLabel* label = new QLabel(QString("<b>%1:</b> %2").arg(labels[i - 2], data[i].toString()));
        label->setWordWrap(true);
        expandLayout->addWidget(label);
    }

    expandableArea->setVisible(false);
    mainLayout->addWidget(expandableArea);

    // Star Rating
    int rating = data[8].toInt();
    QHBoxLayout* starsLayout = new QHBoxLayout();
    for (int i = 0; i < 5; ++i) {
        QPushButton* star = new QPushButton("☆");
        star->setFlat(true);
        star->setStyleSheet("font-size: 20px; color: gold;");
        starButtons.append(star);
        starsLayout->addWidget(star);
        setRating(rating);

        connect(star, &QPushButton::clicked, this, [this, i]() {
            setRating(i+1);
        });
    }
    mainLayout->addLayout(starsLayout);
}

In MainWindow

DictionaryApp::DictionaryApp(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::DictionaryApp)
{
    ui->setupUi(this);
    ui->statusBar->hide();
    browser = new QWebEngineView();
    QVBoxLayout *layout = qobject_cast<QVBoxLayout *>(ui->browser_container->layout());
    if(layout)
    {
        layout->insertWidget(1, browser);
    }

    pool = new QThreadPool();
    initDB();
    full_refresh_vocabTab();
}

full_refresh_vocabTab function:

void DictionaryApp::full_refresh_vocabTab()
{
    QList<QVariantList> records = loadFromDB();
    QVBoxLayout* layout = qobject_cast<QVBoxLayout*>(ui->vocabListContainer->layout());
    if (!layout) {
        qDebug() << "Error: No layout set for vocabListContainer";
        return;
    }

    // Clear previous cards if needed
    QLayoutItem* item;
    while ((item = layout->takeAt(0)) != nullptr) {
        if (item->widget()) delete item->widget();
        delete item;
    }

    // Add new cards
    for (const QVariantList& row : records) {
        CardWidget* card = new CardWidget(row);
        cards.append(card);
        layout->addWidget(card);

        connect(card, &CardWidget::editRequested, this, &DictionaryApp::onEditRequested);
        connect(card, &CardWidget::deleteRequested, this, &DictionaryApp::onDeleteRequested);
        connect(card, &CardWidget::ratingChanged, this, &DictionaryApp::full_refresh_vocabTab);
    }
}

What I've Tried

eventFilter() confirms that the button is receiving mouse clicks even after the tab switch.
The menu works only until I visit the QWebEngineView tab. Returning to the Vocabulary tab causes the menu to stop opening.
There are no errors in the debug output.
Tried removing/re-adding the widget — no change.

Question:
What might cause a QToolButton's QMenu to stop appearing after switching to a tab containing a QWebEngineView and then returning?

Versions:

Qt6.9
Qt Creator 13.0.0
OS: Fedora

SGaist

Hi and welcome to devnet,

Does it also happen if you delete the QWebEngineView ?

soumyaniljana

Hi, thanks for the response,
I tested it by explicitly deleting QWebEngineView when switching tabs. The qDebug() output confirms the deletion is happening, but issue still persists. Any ideas on what might be causing this?

Axel Spoerl

Can you boil this down to a small, compilable reproducer, which can be posted here?
A web view is a complex beast. I've used it myself in a widgets application, in a dialog as a toplevel window of its own. At least there, it doesn't cause any trouble. I'll gladly have a look. Maybe it's even a bug, who knows.

soumyaniljana

Hi, @Axel-Spoerl
Thanks for your willingness to take a look!

Unfortunately, I’m currently unable to post the code or zip file directly here as I don't currently have the privileges to upload a .zip file directly and it’s being flagged as spam due to its length or format. To work around that, I’ve uploaded the minimal, compilable reproducer as a GitHub Gist instead:
https://gist.github.com/sjana0/9a022d41d3b050236779fdfba2a10088
The project is self-contained and demonstrates the issue where the QToolButton menu stops opening after switching tabs with a QWebEngineView.

Please let me know if you run into any issues running it or need a different format. I appreciate your help!

Axel Spoerl

Hi @soumyaniljana,

please post the code here explicitly, using the </> code tags. No zip files, no links.
The community should see the code and not be referred to an external page, that might change over time.
Cheers
Axel

soumyaniljana

Hi @Axel-Spoerl ,

Thanks again for your patience and help.

I've been trying to post the minimal reproducible example using the </> code formatting as requested, but unfortunately, my post keeps getting flagged by Akismet as spam — even though I'm not including any links or external files. It seems the amount of code or structure might be triggering it.

Would it be alright if I posted the code across a few smaller replies in the thread instead? Or if there’s another approach you’d recommend, I’d be happy to follow that.

Really appreciate your time and support.

Kind regards,
soumyanil

soumyaniljana

This post is deleted!

Axel Spoerl

@soumyaniljana That looks incomplete.

soumyaniljana

#include "mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent),
      webView(new QWebEngineView),
      menuButton(new QToolButton),
      tabs(new QTabWidget)
{
    // Browser Tab
    QWidget *browserTab = new QWidget;
    QVBoxLayout *browserLayout = new QVBoxLayout(browserTab);
    browserLayout->addWidget(webView);


	// if you dont initialize the webView, the QMenu dropdown works.
	// and same if you switch tab without initializing it and come back
	// vocabulary tab it again stops working.
    webView->setUrl(QUrl("https://www.google.com"));

    
	// Vocabulary Tab
    QWidget *vocabTab = new QWidget;
    QVBoxLayout *vocabLayout = new QVBoxLayout(vocabTab);

    QMenu *menu = new QMenu;
    menu->addAction("Edit");
    menu->addAction("Delete");

    menuButton->setText("Menu");
    menuButton->setMenu(menu);
    menuButton->setPopupMode(QToolButton::InstantPopup);

    vocabLayout->addWidget(menuButton);

    // Add tabs to QTabWidget
    tabs->addTab(vocabTab, "Vocabulary");
    tabs->addTab(browserTab, "Browser");

    // Set central widget
    setCentralWidget(tabs);
}

soumyaniljana

#pragma once

#include <QMainWindow>

class QWebEngineView;
class QToolButton;
class QTabWidget;

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *parent = nullptr);

private:
    QWebEngineView *webView;
    QToolButton *menuButton;
    QTabWidget *tabs;
};

soumyaniljana

Please include QTabWidget, QWebEngineView, QVBoxLayout, QToolButton, QMenu, QWidget
And that should now be the complete minimal example! Please let me know if it’s still missing anything or if there’s anything you'd like me to simplify further. I really appreciate your time and guidance.

Kind regards,
Soumyanil

soumyaniljana

Hi @Axel-Spoerl,
Just checking in to see if you had a chance to look at the code I posted earlier. I'd really appreciate any insights or suggestions when you get a moment.
Thanks again for your time and guidance.
Regards,
Soumyanil