QWebEngine not cleaning up Chromium processes and get a warning

[raulgd]

Hi all,

I have an app with QtWebEngineWidgets, I have a QMainWindow subclass called WrapperWindow where I add a QWebEngineView, then I add a custom QWebEnginePage to that view that implements the createWindow method so, when a user selects the "Open link in new window" item from the context menu, it creates a new WrapperWindow with the QWebEngineView.
If I open a couple of windows, and then I start closing them, I see on the Windows Task Manager that the chromium processes are not being cleaned up, and when I close the application, on the Qt Creator application output, I get a bunch of warnings stating:

Release of profile requested but WebEnginePage still not deleted. Expect troubles !

Do any of you know how to get QWebEngineView to correctly clean up Chromium?

Here is the code from my Window to create the QWebEngineView and Page:

WrapperWindow::WrapperWindow(QWidget *parent) : QMainWindow(parent)
{
    WrapperWindow(parent, Q_NULLPTR);
}

WrapperWindow::WrapperWindow(QWidget *parent, EventAwareWebEnginePage *page) : QMainWindow(parent)
{
    //setup the window main widget
    mainWidget = new QStackedWidget();
    QWidget* layoutWidget = new QWidget();
    QHBoxLayout* layout = new QHBoxLayout();

    //setup the web view with the system events aware web page
    webView = new QWebEngineView();

    if (page == Q_NULLPTR)
    {
        EventAwareWebEnginePage *enginePage = new EventAwareWebEnginePage();
        webView->setPage(enginePage);
        webView->setUrl(QUrl("https://www.google.com"));
    }
    else
        webView->setPage(page);
    layout->addWidget(webView);

    //make the layout cover the whole window
    layout->setContentsMargins(0,0,0,0);
    layout->setSpacing(0);

    //layout widgets
    layoutWidget->setLayout(layout);
    mainWidget->addWidget(layoutWidget);
    setCentralWidget(mainWidget);
    this->setMinimumSize(QSize(800,600));
}

void WrapperWindow::setPageUrl(const QUrl &url) {
    webView->setUrl(url);
}

And here is the createWindow function from the custom WebEnginePage class called EventAwareWebEnginePage:

QWebEnginePage *EventAwareWebEnginePage::createWindow(WebWindowType type)
{
    if (type == WebWindowType::WebBrowserWindow)
    {
        EventAwareWebEnginePage *page = new EventAwareWebEnginePage();
        connect(page, &QWebEnginePage::urlChanged, [page](const QUrl &url) {
            WrapperWindow *w = new WrapperWindow(Q_NULLPTR, page);
            w->setPageUrl(url);
            w->show();
        });
        return page;
    }
    return Q_NULLPTR;
}

[JonB]

@raulgd said in QWebEngine not cleaning up Chromium processes and get a warning:

Release of profile requested but WebEnginePage still not deleted. Expect troubles

It is worth Googling for that, there are a couple of hits which are worth reading to get some possible ideas.

This is off the wall: does it make any difference if you get rid of your lambda in the connect() and replace with an explicitly coded method? It may not matter from C++, but from Python it cannot release/clean up references properly if there is a lambda.

I also found problems with QWebEngine pages not being released properly/processes hanging around from Python code, though I did not get an error message like you. I found that QWebEngines once closed/deleted did not get correctly deallocated/deleted till I hit the main Qt loop again (e.g. deleteLater()), though that may not be an issue for you.

Food for thought :)

[raulgd]

Thanks for the reply @JonB

The lambdas don't work the same way in C++ as in Python, in C++ they are generic functions referenced through a function pointer so there is no dangling object reference causing Qt reference counting cleanup to stay hanging (AFAIK, maybe some C++ expert could clarify this reasoning).

Also, if you notice, I reference the page pointer to the lambda as well, if I did a "traditional" signal/slot, I wouldn't be able to do so directly, which would make the implementation harder to read, I guess that's why Qt 5 added lambda support in the first place, to make things cleaner/simpler to implement.

But still, thanks for your time on this.

[raulgd]

Ok, finally got it fixed, it was something stupid as expected... When closing a window, after going through the simplebrowser example, I wasn't calling the function deleteLater() from the QMainWindow on the closeEvent, so I implemented the closeEvent functions: event->accept and then deleteLater()

That did the trick, I hope that's helpful for anyone with the same issue.

Just as reference for anyone lost like me, here's how the project ended up looking:
wrapperwindow.cpp

#include "wrapperwindow.h"

#include <QApplication>
#include <QStackedWidget>
#include <QHBoxLayout>
#include <QWebEngineView>
#include <QMessageBox>
#include <QCloseEvent>

#include "eventawarewebenginepage.h"

WrapperWindow::WrapperWindow(QWidget *parent) : QMainWindow(parent)
{
    WrapperWindow(parent, Q_NULLPTR);
}

WrapperWindow::WrapperWindow(QWidget *parent, EventAwareWebEnginePage *page, const QUrl &url) : QMainWindow(parent)
{
    //Basic window setup
    setMinimumSize(QSize(1024,600));
    setWindowTitle(QString("Engineering Architecture IDE"));

    //setup the window main widget
    mainWidget = new QStackedWidget(this);
    QWidget* layoutWidget = new QWidget(mainWidget);
    QHBoxLayout* layout = new QHBoxLayout(layoutWidget);

    //setup the web view with the system events aware web page
    webView = new QWebEngineView(this);

    if (page == Q_NULLPTR)
    {
        EventAwareWebEnginePage *enginePage = new EventAwareWebEnginePage();
        webView->setPage(enginePage);
        webView->setUrl(QUrl("https://www.google.com"));
    }
    else
    {
        page->setParent(webView);
        webView->setPage(page);
    }
    layout->addWidget(webView);

    //make the layout cover the whole window
    layout->setContentsMargins(0,0,0,0);
    layout->setSpacing(0);

    //layout widgets
    mainWidget->addWidget(layoutWidget);
    setCentralWidget(mainWidget);

    //show window on page load
    connect(webView, &QWebEngineView::loadFinished, [this](bool ok) { this->show(); });
}

void WrapperWindow::markAsMainWindow() {
    isMainWindow = true;
}

void WrapperWindow::closeEvent(QCloseEvent *event) {
    if (isMainWindow)
    {
        QMessageBox::StandardButton reply;
        reply = QMessageBox::question(this, "Quit the IDE", "Are you sure you want to exit the Engineering Architecture IDE?", QMessageBox::Yes|QMessageBox::No);
        if (reply == QMessageBox::Yes)
        {
            event->accept();
            deleteLater();
            QApplication::quit();
        }
        else
            event->ignore();
    }
    else
    {
        event->accept();
        deleteLater();
    }
}

eventawarewebenginepage.cpp

#include <QWebEnginePage>

#include "eventawarewebenginepage.h"
#include "wrapperwindow.h"

EventAwareWebEnginePage::EventAwareWebEnginePage(QWidget *parent) : QWebEnginePage(parent)
{

}

QWebEnginePage *EventAwareWebEnginePage::createWindow(WebWindowType type)
{
    if (type == WebWindowType::WebBrowserWindow || type == WebWindowType::WebBrowserTab || type == WebWindowType::WebBrowserBackgroundTab)
    {
        EventAwareWebEnginePage *page = new EventAwareWebEnginePage();
        connect(page, &QWebEnginePage::urlChanged, [page](const QUrl &url) {
            new WrapperWindow(Q_NULLPTR, page, url);
        });
        return page;
    }
    return Q_NULLPTR;
}

[jimmyCAO]

thanks. I have got the same problem.
HzWindow::~HzWindow()
{
m_webEngineView->deleteLater(); // I try this , solved the problem
qApp->removeTranslator(m_curTranslator);
if (m_pPrintHandler)
{
delete m_pPrintHandler;
}
}

and initialize the page like this:
m_webEngineView->setPage(new HzWebEnginePage(m_profile, m_webEngineView));