[Bug]: macOS backend run by non-logged-in user crashes in Ventura #26292

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1. jklymak commented on Jul 12, 2023

   

   jklymak

   on Jul 12, 2023

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   I'm not sure I completely understand but I can imagine it doesn't make sense to use any gui backend if the user is not logged in and hence has no display.

   👍React with 👍1Reacted by Theodore Ni
2. tacaswell

   added this to the v3.9.0 milestone on Jul 12, 2023
3. tacaswell commented on Jul 12, 2023

   

   tacaswell

   on Jul 12, 2023

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   The quick fix is for nix to set the MPLBACKEND=agg env for those packages when running tests.

   For linux we have a helper to detect if we have a usable display and if not, the auto-backend selection falls back to a non-interactive backend. I suspect that something similar is possible for OSX to detect if we have a usable GUI display.

   I tried to reproduce this by sshing into a mac without being logged in, but that failed in other ways (blocking show() blocked...forever and there was no window even after I logged in).

   I think this is a good first issue because it will be adding a private helper function + one or two calls to it in the backend selection logic and/or the backend start up code.

   Tasks:

   • sort out if there is a way (could be in objective-c) to detect if we can actually make a window
   • skip GUI backends on OSX if we do not have a functioning display
   • work out a way to test this (we do have OSX CI jobs and standard ways of running tests in sub-processes) or make a good case as to why we can not test this under CI / developer machines (e.g. we need elevated privileges / to make a new user / log the user out to drive the system to a broken state)

   I would say this is medium difficulty as it is possible that there is a call in the OSX SDK that just answers this question, but might require research to find it. You will also have to understand the auto backend selection logic.
4. tacaswell

   added

   GUI: MacOSX

   Difficulty: Mediumhttps://matplotlib.org/devdocs/devel/contribute.html#good-first-issueshttps://matplotlib.org/devdocs/devel/contribute.html#good-first-issues

   🌱 Good first issueOpen a pull request against these issues if there are no active ones!Open a pull request against these issues if there are no active ones!

   on Jul 12, 2023
5. github-actions commented on Jul 12, 2023

   

   github-actionsBot

   on Jul 12, 2023

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   Good first issue - notes for new contributors

   This issue is suited to new contributors because it does not require understanding of the Matplotlib internals. To get started, please see our contributing guide.

   We do not assign issues. Check the Development section in the sidebar for linked pull requests (PRs). If there are none, feel free to start working on it. If there is an open PR, please collaborate on the work by reviewing it rather than duplicating it in a competing PR.

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6. tacaswell commented on Jul 12, 2023

   

   tacaswell

   on Jul 12, 2023

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   I labeled this as 3.9 to keep it out of our 3.8 wrap up workstream for now. If this ends up being simple no problem in backporting it to 3.8.x .

   👍React with 👍1Reacted by Theodore Ni
7. tjni commented on Jul 12, 2023

   

   tjni

   on Jul 12, 2023

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   Thank you for responding! I cobbled together these reproduction steps on my macOS 13.4.1 M1 machine:

   1. Suppose we are currently logged in with username me.
   2. Set up test directory:

   cd ~
   mkdir matplotlib-test
   cd matplotlib-test
   python -m venv env
   source env/bin/activate
   pip install matplotlib
   

   3. Create a script test.py:

   import matplotlib.pyplot as plt
   
   figure = plt.figure()
   

   4. Verify that python test.py does not crash.
   5. Create a new user named someuser:

   sudo dscl . -create /Users/someuser
   sudo dscl . -create /Users/someuser UserShell /bin/bash
   sudo dscl . -create /Users/someuser RealName "Some User"
   sudo dscl . -create /Users/someuser UniqueID "1010"
   sudo dscl . -create /Users/someuser PrimaryGroupID 80
   sudo dscl . -create /Users/someuser NFSHomeDirectory /Users/someuser
   sudo dscl . -passwd /Users/someuser password
   sudo mkdir /Users/someuser
   

   6. Temporarily give access to me's home directory:

   sudo chmod 777 /Users/me
   

   7. Become someuser (password is password):

   su - someuser
   cd /Users/me/matplotlib-test
   source env/bin/activate
   

   8. Verify that python test.py crashes:

   (env) -bash-3.2$ python test.py
   Matplotlib created a temporary cache directory at /tmp/matplotlib-m4igy099 because the default path (/Users/someuser/.matplotlib) is not a writable directory; it is highly recommended to set the MPLCONFIGDIR environment variable to a writable directory, in particular to speed up the import of Matplotlib and to better support multiprocessing.
   2023-07-12 09:53:30.523 Python[87901:57870394] XType: Using static font registry.
   Trace/BPT trap: 5
   

   9. Restore everything:

   sudo chmod 750 /Users/me
   sudo dscl . -delete /Users/someuser
   sudo rm -rf /Users/someuser
   
8. tacaswell commented on Jul 12, 2023

   

   tacaswell

   on Jul 12, 2023

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   Thank you for the reproduction examples but that is not something we can put in the test suite!
9. QuLogic commented on Jan 20, 2024

   

   QuLogic

   on Jan 20, 2024

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   I wonder if we look at the list of screens, it would be empty in this case?
10. QuLogic

    modified the milestones: v3.9.0, 3.9.1 on Apr 2, 2024
11. tacaswell

    modified the milestones: v3.9.1, v3.10.0 on Jun 26, 2024
12. tacaswell

    modified the milestones: v3.10.0, future releases on Oct 30, 2024
13. tacaswell

    closed this as completedin #27761on Oct 16, 2026
14. QuLogic

    modified the milestones: future releases, v3.12.0 on Oct 16, 2026