Vizkit3DWidget tries to swapBuffers on non-exposed windows, resulting in message on stderr

[pierrewillenbrockdfki]

This happens when running rock-display_bin, using my qt5 branches. Vizkit3DWidget is only changed in minor ways, so the underlying problem imo also exists using qt4.

rock-display does not show() the Vizkit3DWidget by default, but Vizkit3DWidget still does setup its _timer to start calling osgviz::update(), which goes on to osgviz::WindowManager::frame() and then to osgViewer::CompositeViewer::frame(), and finally calling QOpenGLContext::swapBuffers().

Vizkit3DWidget uses an osgviz::Window that extends osgViewer::CompositeViewer with additional data and functionality. The osgviz::Window is created in a way that automatically registers it with the osgviz::WindowManager and cannot be unregistered and registered again without changing its state.

The actual message is

QOpenGLContext::swapBuffers() called with non-exposed window, behavior is undefined

Backtrace from osgviz::WindowManager::frame()

#0  osgviz::WindowManager::frame() (this=0x555555c116d0) at rock/gui/osgviz/src/windows/WindowManager.cpp:68
#1  0x00007ffff55a631e in osgviz::OsgViz::update() (this=0x555555c11640) at rock/gui/osgviz/src/OsgViz.cpp:92
#2  0x00007ffff7067eac in void doActivate<false>(QObject*, int, void**) () at /usr/lib64/libQt5Core.so.5
#3  0x00007ffff706b52a in QTimer::timeout(QTimer::QPrivateSignal) () at /usr/lib64/libQt5Core.so.5
#4  0x00007ffff70605a5 in QObject::event(QEvent*) () at /usr/lib64/libQt5Core.so.5
#5  0x00007ffff62f1c9f in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib64/libQt5Widgets.so.5
#6  0x00007ffff62fad90 in QApplication::notify(QObject*, QEvent*) () at /usr/lib64/libQt5Widgets.so.5
#7  0x00007ffff70351ee in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib64/libQt5Core.so.5
#8  0x00007ffff7088598 in QTimerInfoList::activateTimers() () at /usr/lib64/libQt5Core.so.5
#9  0x00007ffff7088e5c in idleTimerSourceDispatch(_GSource*, int (*)(void*), void*) () at /usr/lib64/libQt5Core.so.5
#10 0x00007ffff0527e4b in g_main_context_dispatch () at /usr/lib64/libglib-2.0.so.0
#11 0x00007ffff05280f8 in g_main_context_iterate.constprop () at /usr/lib64/libglib-2.0.so.0
#12 0x00007ffff05281af in g_main_context_iteration () at /usr/lib64/libglib-2.0.so.0
#13 0x00007ffff70892a0 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#14 0x00007ffff703409b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#15 0x00007ffff703be42 in QCoreApplication::exec() () at /usr/lib64/libQt5Core.so.5
#16 0x000055555555ac64 in main(int, char**) (argc=<optimized out>, argv=0x7fffffffb268) at rock/gui/rock-display/src/Main.cpp:54

A simple solution would be to check for isVisible() before the call to osgviz::update(), but that only works for applications that have no other calls to osgviz::update() and a single Vizkit3DWidget(or all Vizkit3DWidget being shown/hidden at the same time). A more involved solution could stop using osgviz::Window and osgviz::WindowManager and include the necessary bits directly(with -20+23 lines changes; i can try to rebase that patch off of my qt5 work on request).

[planthaber]

That would be nice, i already tried to check isVisible(), but it seems like the main window is unable to complete show(), when frame() is not called (the Graphicscontext coming from QT)

[pierrewillenbrockdfki]

Find the two changes here: https://github.com/pierrewillenbrockdfki/gui-vizkit3d/tree/fix-calling-frame-on-hidden-window

(That was a lot easier than expected, but not even compile tested, lacking qt4)

[planthaber]

I tested it in my envire_visualizer setup (that used vizkit3d directly) and it works.

Still needs to be tested in a plain rock gui/vizkit (rock-display, debug drawings) context though.