Memory leak in core.commands.cofr.PivotIndicator

[Tristan Croll]

... leading to one of the more initially head-scratching stack traces I've come across. Short story is that PivotIndicator.delete() doesn't call Drawing.delete().

Symptoms:

If, while running an ISOLDE simulation, I do cofr showpivot false in the command line, I get a stack trace with the following included:

Current thread 0x00007f62ef7fe700 (most recent call first):
  File "/home/tic20/apps/chimerax/lib/python3.6/site-packages/chimerax/core/graphics/opengl.py", line 1599 in delete_buffer
  File "/home/tic20/apps/chimerax/lib/python3.6/site-packages/chimerax/core/graphics/drawing.py", line 1475 in delete
  File "/home/tic20/apps/chimerax/lib/python3.6/site-packages/chimerax/core/graphics/drawing.py", line 1466 in __del__
  File "/home/tic20/apps/chimerax/lib/python3.6/site-packages/simtk/openmm/vec3.py", line 42 in __new__
  File "/home/tic20/apps/chimerax/lib/python3.6/site-packages/simtk/openmm/openmm.py", line 3919 in _getStateAsLists
  File "/home/tic20/apps/chimerax/lib/python3.6/site-packages/simtk/openmm/openmm.py", line 3969 in getState
  File "/home/tic20/.local/share/ChimeraX/0.1/site-packages/chimerax/isolde/openmm/sim_handler.py", line 677 in get_and_check_positions
  File "/home/tic20/.local/share/ChimeraX/0.1/site-packages/chimerax/isolde/openmm/sim_handler.py", line 669 in equil_step
  File "/home/tic20/.local/share/ChimeraX/0.1/site-packages/chimerax/isolde/openmm/sim_thread.py", line 322 in main_loop
  File "/home/tic20/.local/share/ChimeraX/0.1/site-packages/chimerax/isolde/openmm/sim_thread.py", line 101 in _sim_thread
  File "/home/tic20/apps/chimerax/lib/python3.6/multiprocessing/pool.py", line 119 in worker
  File "/home/tic20/apps/chimerax/lib/python3.6/threading.py", line 864 in run
  File "/home/tic20/apps/chimerax/lib/python3.6/threading.py", line 916 in _bootstrap_inner
  File "/home/tic20/apps/chimerax/lib/python3.6/threading.py", line 884 in _bootstrap

... which was confusing in all sorts of ways (not least of which is that this is the simulation thread, from which I've strictly excluded all ChimeraX objects). Memory leaks are fun. Anyway, amending the delete method to:

    def delete(self):
        self._session.triggers.remove_handler(self._update_handler)
        super().delete()

Fixes it.

[Tom Goddard]

Fixed.

[pett]

Milestone renamed