Session restore of graphics: self._positions is None

[chimerax-bug-report@…]

The following bug report has been submitted:
Platform:        Darwin-15.3.0-x86_64-i386-64bit
ChimeraX Version: 0.9 (2019-01-05)
Description
(Describe the actions that caused this problem to occur here)

Log:
UCSF ChimeraX version: 0.9 (2019-01-05)  
How to cite UCSF ChimeraX  

> open /Users/jliu/Desktop/T7-Ian/T7-BIN2/20190105-Figure.cxs

Unable to restore session, resetting.  
  
Traceback (most recent call last):  
File "/Volumes/ChimeraXInstaller
1/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-
packages/chimerax/core/session.py", line 593, in restore  
obj = sm.restore_snapshot(self, data)  
File "/Volumes/ChimeraXInstaller
1/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-
packages/chimerax/std_commands/view.py", line 214, in restore_snapshot  
for k,v in data['view attrs'].items():  
TypeError: 'NoneType' object is not subscriptable  
  
opened ChimeraX session  
Traceback (most recent call last):  
File "/Volumes/ChimeraXInstaller
1/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-
packages/chimerax/core/triggerset.py", line 130, in invoke  
return self._func(self._name, data)  
File "/Volumes/ChimeraXInstaller
1/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-
packages/chimerax/map/volume.py", line 3376, in _update_drawings  
if v.display:  
File "/Volumes/ChimeraXInstaller
1/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-
packages/chimerax/core/graphics/drawing.py", line 311, in get_display  
return self._any_displayed_positions and len(self._positions) > 0  
TypeError: object of type 'NoneType' has no len()  
  
Error processing trigger "graphics update": object of type 'NoneType' has no
len():  
TypeError: object of type 'NoneType' has no len()  
  
File "/Volumes/ChimeraXInstaller
1/ChimeraX.app/Contents/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-
packages/chimerax/core/graphics/drawing.py", line 311, in get_display  
return self._any_displayed_positions and len(self._positions) > 0  
  
See log for complete Python traceback.  
  




OpenGL version: 4.1 INTEL-10.12.13
OpenGL renderer: Intel(R) HD Graphics 6000
OpenGL vendor: Intel Inc.

[Tom Goddard]

NamedView.restore_snapshot(session, data) is being called with data = None. But the take_snapshot() method can never produce data = None. So I don't see how this can happen. I tested saving and restoring sessions with named views and did not get any error.

Are there circumstances where restore_snapshot() can be called with data = None? The take_snapshot() / restore_snapshot() code for named views is the same back to ChimeraX 0.7 and the session file the person opened has a date in the file name from a few days ago. So I don't think this is caused by writing the session in an old ChimeraX.

Greg, any ideas about how restore_snapshot() could be called with data = None?

[Greg Couch]

It is possible for restore_snapshot to be called with None. If there is a problem saving the session, then a warning is printed: 'Unable to save "%s". Session might not restore properly.' and None is saved for the object. That can happen if take_snapshot throws an exception, or if it returns None.

To see the problem use the "debug sdump" command to convert the session file to text.

[Tom Goddard]

Ok. Seems likely that there was an error on saving the session then. I don't think I will put in code to try to allow restoring the partially saved session unless I get more reports of the same problem.