Crash using OpenGL widget

[zyrkiel]

Hello,

I am facing a different issues when handling OpenGL widgets inside the ads::CDockWidget.
I have been able to reproduce a crash with a light example: https://github.com/zyrkiel/Qt-Advanced-Docking-System/tree/Add-OpenGl-example

Screencast.from.2025-02-20.12-16-59.mp4

What I try to do, in this example, is to undock then dock my ads::CDockWidget that handles an OpenGL widget (here a chart with an GPU accelerated series). In that case, the MainWindow crashes when docking back the CDockWidget.
(In my project, I am using QVTKOpenGLStereoWidget that creates a different situation where the CDockWidget disappears if it is undocked from the area it has been added to)

Here is the callstack:

libQt6Core.so.6!QMetaObject::cast(const QMetaObject * const this, const QObject * obj) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/corelib/kernel/qmetaobject.cpp:395)
libQt6Widgets.so.6!QMetaObject::cast(const QMetaObject * const this, QObject * obj) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/corelib/kernel/qobjectdefs.h:241)
libQt6Widgets.so.6!qobject_cast<QWidgetWindow*>(QObject * object) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/corelib/kernel/qobject.h:419)
libQt6Widgets.so.6!QApplicationPrivate::notifyActiveWindowChange(QApplicationPrivate * const this, QWindow * previous) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/widgets/kernel/qapplication.cpp:1935)
libQt6Gui.so.6!QGuiApplicationPrivate::processFocusWindowEvent(QWindowSystemInterfacePrivate::FocusWindowEvent * e) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/gui/kernel/qguiapplication.cpp:2566)
libQt6Gui.so.6!QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent * e) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/gui/kernel/qguiapplication.cpp:2092)
libQt6Gui.so.6!QWindowSystemInterface::sendWindowSystemEvents(QEventLoop::ProcessEventsFlags flags) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/gui/kernel/qwindowsysteminterface.cpp:1114)
libQt6XcbQpa.so.6!QXcbUnixEventDispatcher::processEvents(QXcbUnixEventDispatcher * const this, QEventLoop::ProcessEventsFlags flags) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/plugins/platforms/xcb/qxcbeventdispatcher.cpp:27)
libQt6Core.so.6!QEventLoop::processEvents(QEventLoop * const this, QEventLoop::ProcessEventsFlags flags) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/corelib/kernel/qeventloop.cpp:100)
libQt6Core.so.6!QEventLoop::exec(QEventLoop * const this, QEventLoop::ProcessEventsFlags flags) (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/corelib/kernel/qeventloop.cpp:182)
libQt6Core.so.6!QCoreApplication::exec() (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/corelib/kernel/qcoreapplication.cpp:1486)
libQt6Gui.so.6!QGuiApplication::exec() (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/gui/kernel/qguiapplication.cpp:1926)
libQt6Widgets.so.6!QApplication::exec() (/home/tgeffroy/GitRepo/git/vcpkg/buildtrees/qtbase/src/here-src-6-ac50939fe7.clean/src/widgets/kernel/qapplication.cpp:2555)
main(int argc, char ** argv) (/home/tgeffroy/GitRepo/git/Qt-Advanced-Docking-System/examples/openGL/main.cpp:16)

---

My config is:
Qt: 6.7.2 (through vcpkg official ports but it should not matter)
ADS: 4.4.0
OS: Ubuntu 24.04
Debug & Release

[zyrkiel]

I have done a similar test by replacing the ads::CDockWidget by a QDockWidget. In that case, undocking and docking the dock widget containing the OpenGL chart doesn't meet the issue.

[zyrkiel]

A colleague has tested it on Windows and cannot reproduce what happens on Ubuntu...

[githubuser0xFFFF]

Please have a look into #281

[zyrkiel]

It's not the same as #281...

I have a first solution for the chart using openGL; floating dock container are aliens on Linux. Non native widgets doesn't have the ritght winid and that has consequences on the SurfaceType that doesn't match the OpenGLSurface forcing the widget to be recreated while dropped back in the area.
The best solution for this is to use the winid function in the DockSplitter class constructor (according to this doc:https://doc.qt.io/qt-6/qwidget.html#native-widgets-vs-alien-widgets). Others solutions proposed by the documentation are not working properly.

I am improving the example to fix the use of QOpenGLWidget and QOpenGLWindow included in a QWidget. I need more time to investigate the associated issues. Once all is working, I will propose you a MR with the example and the fix.

[githubuser0xFFFF]

Great - thank you very much.

[zyrkiel]

Hello,

I finally achieved my OpenGL example and added several fix in the code.
I hope it's ok for you that I open a PR: #727

Do not hesitate to test it and send your remarks.

Regards,