QDockWidget with QML crash

Vsevolod

Hi. I have simple app from this forum with QDockWidget and qml. Every time i try to undock the QDockWidget, the application crash.

Environment: Ubuntu 18.04, Qt Creator 4.7.2, Qt 5.10.1

The code below:

main.cpp:

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    QApplication app(argc, argv);

    QMainWindow mainWindow;
    {
        auto centalWidget = new QWidget(&mainWindow);
        mainWindow.setCentralWidget(centalWidget);
    }

    {
        auto dockWidget = new QDockWidget("One", &mainWindow);
        dockWidget->setAllowedAreas(Qt::LeftDockWidgetArea | Qt::RightDockWidgetArea);
        auto view = new QQuickWidget(dockWidget);
        view->setResizeMode(QQuickWidget::SizeRootObjectToView);
        dockWidget->setWidget(view);
        view->setSource(QUrl("qrc:/main1.qml"));
        mainWindow.addDockWidget(Qt::LeftDockWidgetArea, dockWidget);
    }

    mainWindow.showMaximized();
    return app.exec();
}

main1.qml:

import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3

Rectangle {
    id: main
    color: "orange"
    Text {
        anchors.horizontalCenter: parent.horizontalCenter
        text: "one"
        SequentialAnimation on font.pixelSize {
            loops: Animation.Infinite
            PropertyAnimation { to: 200 }
            PropertyAnimation { to: 0 }
        }
        SequentialAnimation on y {
            loops: Animation.Infinite
            PropertyAnimation { duration: 1000; to: 1000 }
            PropertyAnimation { duration: 1000; to: 0 }
        }
    }
}

Here the callstack:

1  QSGDefaultDistanceFieldGlyphCache::~QSGDefaultDistanceFieldGlyphCache()
2  QSGDefaultDistanceFieldGlyphCache::~QSGDefaultDistanceFieldGlyphCache()
3  QSGDefaultRenderContext::invalidate()
4  QQuickRenderControl::invalidate()
5  ??
6  ??
7  QQuickWidget::event(QEvent *)
8  QApplicationPrivate::notify_helper(QObject *, QEvent *)
9  QApplication::notify(QObject *, QEvent *)
10 QCoreApplication::notifyInternal2(QObject *, QEvent *)
11 ??
12 ?? 
13 QWidget::setParent(QWidget *, QFlags<Qt::WindowType>)
14 QWidgetPrivate::setWindowFlags(QFlags<Qt::WindowType>)
15 ??
16 ??
17 ??
18 ??
19 ??
20 QDockWidget::event(QEvent *)
21 QApplicationPrivate::notify_helper(QObject *, QEvent *)
22 QApplication::notify(QObject *, QEvent *)
23 QCoreApplication::notifyInternal2(QObject *, QEvent *)
24 QApplicationPrivate::sendMouseEvent(QWidget *, QMouseEvent *, QWidget *, QWidget *, QWidget * *, QPointer<QWidget>&, bool)
25 ??
26 ??
27 QApplicationPrivate::notify_helper(QObject *, QEvent *)
28 QApplication::notify(QObject *, QEvent *)
29 QCoreApplication::notifyInternal2(QObject *, QEvent *)
30 QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent *)
31 QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent *)
32 QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>)
33 ??
34 QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>)
35 QCoreApplication::exec()
36 main

SGaist

Hi and welcome to devnet,

Do you have the same crash if you use your distribution provided Qt ?

Vsevolod

Hi! Thank you for your question. Yes, if I rebuild the project with the system qt 5.9.5, i have the same behavior : application crashed after i try to detach QDockWidget. Here is the callstack:

1  ??
2  QSGDefaultDistanceFieldGlyphCache::~QSGDefaultDistanceFieldGlyphCache()
3  QSGDefaultDistanceFieldGlyphCache::~QSGDefaultDistanceFieldGlyphCache()
4  QSGDistanceFieldGlyphCacheManager::~QSGDistanceFieldGlyphCacheManager()
5  QSGDefaultRenderContext::invalidate()
6  QQuickRenderControl::invalidate()
7  ??
8  ??
9  QQuickWidget::event(QEvent *)
10 QApplicationPrivate::notify_helper(QObject *, QEvent *)
11 QApplication::notify(QObject *, QEvent *)
12 QCoreApplication::notifyInternal2(QObject *, QEvent *)
13 ??
14 ??
15 QWidget::setParent(QWidget *, QFlags<Qt::WindowType>)
16 QWidgetPrivate::setWindowFlags(QFlags<Qt::WindowType>)
17 ??
18 ??
19 ??
20 ??
21 ??
22 QDockWidget::event(QEvent *)
23 QApplicationPrivate::notify_helper(QObject *, QEvent *)
24 QApplication::notify(QObject *, QEvent *)
25 QCoreApplication::notifyInternal2(QObject *, QEvent *)
26 QApplicationPrivate::sendMouseEvent(QWidget *, QMouseEvent *, QWidget *, QWidget *, QWidget * *, QPointer<QWidget>&, bool)
27 ??
28 ??
29 QApplicationPrivate::notify_helper(QObject *, QEvent *)
30 QApplication::notify(QObject *, QEvent *)
31 QCoreApplication::notifyInternal2(QObject *, QEvent *)
32 QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent *)
33 QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent *)
34 QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>)
35 ??
36 g_main_context_dispatch
37 ??
38 g_main_context_iteration
39 QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>)
40 QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>)
41 QCoreApplication::exec()
42 main                         main.cpp 38

SGaist

I tested your application with Qt 5.11.2 on macOS and it's working properly.

Vsevolod

I am sorry, it must be something wrong with my installation. This problem exist in KDE desktop, but after i switched to Gnome, all works fine. Thank you.