Close QWebEngineProcess.exe - c++

Question

I have a problem that, after closing a QDialog with web content, the QWebEngineProcess.exe process is not closing.
Here is a minimal example:
#include <QApplication>
#include <QWebEngineView>
#include <QWebEngineSettings>
#include <QDialog>
#include <QMainWindow>
#include <QLayout>
#include <QtGui>
#include <QPushButton>
class Dialog : public QDialog
{
public:
Dialog() : QDialog(nullptr)
{
resize(512, 512);
setAttribute(Qt::WA_DeleteOnClose);
auto verticalLayout = new QVBoxLayout(this);
verticalLayout->setSpacing(0);
verticalLayout->setContentsMargins(0, 0, 0, 0);
m_webView = new QWebEngineView(this);
verticalLayout->addWidget(m_webView);
}
void openPage(const QUrl& url)
{
m_webView->setUrl(url);
}
private:
QWebEngineView* m_webView;
};
class MainWindow : public QMainWindow
{
public:
MainWindow() : QMainWindow(nullptr)
{
resize(512, 512);
QPushButton* btn = new QPushButton("open web dialog", this);
connect(btn, &QPushButton::clicked, [this] ()
{
if (m_dialog == nullptr)
{
m_dialog = new Dialog();
m_dialog->openPage(QUrl("https://www.qt.io"));
m_dialog->show();
}
});
}
private:
QPointer<Dialog> m_dialog;
};
int main(int argc, char *argv[])
{
QCoreApplication::setOrganizationName("QtExamples");
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QApplication app(argc, argv);
MainWindow window;
window.show();
return app.exec();
}
I'm expecting that, after the dialog is closed, QWebEngineProcess.exe will be closed too, because I'm not using webengine anymore.
P.S. During opening WebPage, I have 2 QWebEngineProcess.exe. One is disappearing, but the second one left.

Answer 1

For any QObject instances (such as QDialog and QWebEngineView), the destructor of a parent object destroys all child objects. This means, for every object you new, it must either have a parent, or you must delete it manually, otherwise you are creating a leak and objects will remain open (not deleted).
You are creating a QWebEngineView object with the correct parent, but the parent (the Dialog) doesn't have a parent (you initialize the parent to nullptr). This means the Dialog would delete the QWebEngineView, except it never is deleted itself.
To fix it, either delete the Dialog (stored in m_dialog) manually in the MainWindow destructor (not recommended), or initialize it correctly with the MainWindow as its parent.
This may also be related to a bug in Qt 5.11 and 5.12. If this is the problem, the recommended solution is to add QCoreApplication::setAttribute(Qt::AA_UseOpenGLES); at the top of your main() function (before declaring the QApplication).