Bug report: Exception when closing a workbench with status bar

[greschd]

Environment

OS: Windows
Python version: 3.10
Toolkit: Wx

Description

When creating a Workbench with a status_bar, the following exception is raised when closing the window:

Traceback (most recent call last):
  File "D:\ANSYSDev\thirdparty_sources\pyface\pyface\dock\dock_sizer.py", line 4022, in CalcMin
    dx, dy = self._contents.calc_min()
  File "D:\ANSYSDev\thirdparty_sources\pyface\pyface\dock\dock_sizer.py", line 3190, in calc_min
    dx, dy = item.calc_min(use_size)
  File "D:\ANSYSDev\thirdparty_sources\pyface\pyface\dock\dock_sizer.py", line 2402, in calc_min
    theme = self.theme
  File "D:\ANSYSDev\thirdparty_sources\pyface\pyface\dock\dock_sizer.py", line 503, in _get_theme
    return self.control.GetParent().owner.theme
RuntimeError: wrapped C/C++ object of type TraitsUIPanel has been deleted

Steps to Reproduce

• Run the following script (adapted and minimized from the workbench example):

  from traits.etsconfig.api import ETSConfig
  ETSConfig.toolkit = 'wx'
  
  from traits.api import HasTraits, Int, Str
  from pyface.api import GUI
  from pyface.action.api import StatusBarManager
  from pyface.workbench.api import WorkbenchWindow, Workbench
  
  
  class ExampleWorkbenchWindow(WorkbenchWindow):
      def _status_bar_manager_default(self):
          return StatusBarManager(messages=['', ''])
  
  
  class Person(HasTraits):
      name = Str()
      age = Int()
  
      def __str__(self):
          return self.name
  
  if __name__ == "__main__":
      gui = GUI()
      fred = Person(name="fred", age=42)
      workbench = Workbench(state_location=gui.state_location, window_factory=ExampleWorkbenchWindow)
      window = workbench.create_window()
      window.open()
      window.edit(fred)
  
      gui.start_event_loop()

• Close the application

Other observations

The exception does not occur if the window tab (fred) is closed before closing the Application.

Changing the toolkit to 'qt' also makes the exception disappear.

[greschd]

A crude way to get rid of the error is by removing

pyface/pyface/i_application_window.py

Lines 132 to 133 in 85fd544

	if self.status_bar_manager is not None:
	self.status_bar_manager.destroy()

added in #1141. I suspect this is not the correct solution though, and #1141 simply exposed the underlying issue.

[corranwebster]

Possibly related to this recent PR: #1192

[greschd]

Directly reverting #1192 (and passing self.control as parent) doesn't fix the issue, but it might indeed be related to why parent was maybe used at some earlier point.

Also note: I've noticed this particular repro doesn't produce an error on Linux, but have seen the same error in a more complex application. If desired, I can try and find a version that fails on both platforms.

[corranwebster]

I have a hypothesis that this is because the status bar is not being removed from the owning window before it is destroyed.