CenterOfMass: FreeCAD hangs if you try to take the centre of mass of a centre of mass

[jes]

Example video: https://www.youtube.com/watch?v=IgP_59iBCRo

• Make any object in FreeCAD
• Calculate its centre of mass and tick the eye icon to make it visible
• Close the centre of mass panel
• Select the CenterOfMass object and click the CenterOfMass toolbar button
• FreeCAD hangs

The full output in my terminal window is:

jes@longjohn:~$ freecad
FreeCAD 0.21.2, Libs: 0.21.2R33771 (Git)
© Juergen Riegel, Werner Mayer, Yorik van Havre and others 2001-2023
FreeCAD is free and open-source software licensed under the terms of LGPL2+ license.
FreeCAD wouldn't be possible without FreeCAD community.
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Adding snap-specific PYTHONPATH to sys.path: /home/jes/snap/freecad/common/.local/lib/python3.8/site-packages:/snap/freecad/908/lib/python3.8/site-packages:/snap/freecad/908/usr/lib/python3/dist-packages
Qt: Session management error: Could not open network socket
connect failed: No such file or directory
Loading CenterOfMass 0.7.6 ...
/home/jes/snap/freecad/common/CenterOfMass.FCMacro:307: DeprecationWarning: an integer is required (got type PySide2.QtCore.Qt.AlignmentFlag).  Implicit conversion to integers using __int__ is deprecated, and may be removed in a future version of Python.
  label_comboUnit.setAlignment(QtCore.Qt.AlignRight | QtCore.Qt.AlignVCenter)
/home/jes/snap/freecad/common/CenterOfMass.FCMacro:320: DeprecationWarning: an integer is required (got type PySide2.QtCore.Qt.AlignmentFlag).  Implicit conversion to integers using __int__ is deprecated, and may be removed in a future version of Python.
  label_defaultDensity.setAlignment(QtCore.Qt.AlignRight | QtCore.Qt.AlignVCenter)
Looking for material cards according to User parameter:BaseApp/Preferences/Mod/Material/Resources
  /snap/freecad/908/usr/share/Mod/Material/StandardMaterial
  /home/jes/snap/freecad/common/Material
Loading CenterOfMass 0.7.6 ...
Ignored invalid object from selection
/home/jes/snap/freecad/common/CenterOfMass.FCMacro:307: DeprecationWarning: an integer is required (got type PySide2.QtCore.Qt.AlignmentFlag).  Implicit conversion to integers using __int__ is deprecated, and may be removed in a future version of Python.
  label_comboUnit.setAlignment(QtCore.Qt.AlignRight | QtCore.Qt.AlignVCenter)
/home/jes/snap/freecad/common/CenterOfMass.FCMacro:320: DeprecationWarning: an integer is required (got type PySide2.QtCore.Qt.AlignmentFlag).  Implicit conversion to integers using __int__ is deprecated, and may be removed in a future version of Python.
  label_defaultDensity.setAlignment(QtCore.Qt.AlignRight | QtCore.Qt.AlignVCenter)
Looking for material cards according to User parameter:BaseApp/Preferences/Mod/Material/Resources
  /snap/freecad/908/usr/share/Mod/Material/StandardMaterial
  /home/jes/snap/freecad/common/Material
Traceback (most recent call last):
  File "/home/jes/snap/freecad/common/CenterOfMass.FCMacro", line 1253, in <module>
    myWidget = CenterofmassDock()
  File "/home/jes/snap/freecad/common/CenterOfMass.FCMacro", line 111, in __init__
    self.child = CenterofmassWidget(self)
  File "/home/jes/snap/freecad/common/CenterOfMass.FCMacro", line 269, in __init__
    self.init_solids(objs)
  File "/home/jes/snap/freecad/common/CenterOfMass.FCMacro", line 517, in init_solids
    self.find_all_centerOfMass(objs)
  File "/home/jes/snap/freecad/common/CenterOfMass.FCMacro", line 810, in find_all_centerOfMass
    if hasattr(objs[sol], 'CenterOfGravity'):
<class 'RuntimeError'>: Cannot get center of gravity
^C^C^C^C^CTraceback (most recent call last):
  File "/home/jes/snap/freecad/common/CenterOfMass.FCMacro", line 544, in on_focusChanged
    def on_focusChanged(self, oldWidget, nowWidget):
KeyboardInterrupt
Program received signal SIGSEGV, Segmentation fault.
#0  /lib/x86_64-linux-gnu/libc.so.6(+0x43090) [0x7466e0c5e090]
#1  0x7466de5a0390 in QV4::MemoryManager::allocString(unsigned long) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Qml.so.5+0x20
#2  0x7466de60f7c2 in QV4::ExecutionEngine::newString(QString const&) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Qml.so.5+0x42
#3  0x7466de619364 in QV4::ExecutionEngine::throwError(QString const&) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Qml.so.5+0x14
#4  0x7466dfedd882 in PySide::SignalManager::qt_metacall(QObject*, QMetaObject::Call, int, void**) from /snap/freecad/908/usr/lib/x86_64-linux-gnu/libpyside2.cpython-38-x86_64-linux-gnu.so.5.14+0x272
#5  /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Core.so.5(+0x2ec37c) [0x7466e130b37c]
#6  0x7466e1e5d5af in QApplication::focusChanged(QWidget*, QWidget*) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5+0x4f
#7  0x7466e1e653c8 in QApplicationPrivate::setFocusWidget(QWidget*, Qt::FocusReason) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5+0x108
#8  0x7466e1e9bfdf in QWidget::setFocus(Qt::FocusReason) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5+0x12f
#9  0x7466e1e659c2 in QApplication::setActiveWindow(QWidget*) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5+0x482
#10  0x7466e1e65a43 in QApplicationPrivate::notifyActiveWindowChange(QWindow*) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5+0x43
#11  0x7466e16f6115 in QGuiApplicationPrivate::processActivatedEvent(QWindowSystemInterfacePrivate::ActivatedWindowEvent*) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Gui.so.5+0x385
#12  0x7466e16fadbc in QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Gui.so.5+0x19c
#13  0x7466e16d16dc in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Gui.so.5+0xac
#14  /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/../../../libQt5XcbQpa.so.5(+0x79e5e) [0x7466dad45e5e]
#15  /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0(g_main_context_dispatch+0x27d) [0x7466dec9317d]
#16  /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0(+0x52400) [0x7466dec93400]
#17  /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0(g_main_context_iteration+0x33) [0x7466dec934a3]
#18  0x7466e132ef82 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Core.so.5+0x62
#19  0x7466e12d2bab in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Core.so.5+0x12b
#20  0x7466e12dad54 in QCoreApplication::exec() from /snap/freecad/908/kf5/usr/lib/x86_64-linux-gnu/libQt5Core.so.5+0x94
#21  0x7466e37c0af1 in Gui::Application::runApplication() from /snap/freecad/908/usr/lib/libFreeCADGui.so+0x1b51
#22  /snap/freecad/908/usr/bin/FreeCAD(+0xa380) [0x6231b22f7380]
#23  /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3) [0x7466e0c3f083]
#24  /snap/freecad/908/usr/bin/FreeCAD(+0xa72e) [0x6231b22f772e]

[galou]

@s-quirin you should not be responsible for a FreeCAD crash but there may be a way to avoid it.