NSWindow main thread error when trying to setup Gymnasium (openapi gym)

[eoliphan]

Hi, im trying to run some simple gymnasium stuff and getting the following error:

(require-python '[gymnasium :as gym])
(def env (gym/make "LunarLander-v2" :render_mode "human"))

; error (Temurin java 17) or crash (correto java 17)
(py. env reset :seed 42)

Execution error at libpython-clj2.python.ffi/check-error-throw (ffi.clj:707).
Traceback (most recent call last):
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/wrappers/time_limit.py", line 75, in reset
    return self.env.reset(**kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/wrappers/order_enforcing.py", line 61, in reset
    return self.env.reset(**kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/wrappers/env_checker.py", line 57, in reset
    return env_reset_passive_checker(self.env, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/utils/passive_env_checker.py", line 186, in env_reset_passive_checker
    result = env.reset(**kwargs)
             ^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/envs/box2d/lunar_lander.py", line 461, in reset
    self.render()
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/envs/box2d/lunar_lander.py", line 699, in render
    self.screen = pygame.display.set_mode((VIEWPORT_W, VIEWPORT_H))
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pygame.error: NSWindow should only be instantiated on the main thread!

I'm on OSX Sonoma (silicon), python 3.11.6, Clojure 1.11.1 and java 17. I was actually about to write this as a crash report, but decided to try another Java 17 jvm and was able to get the error output instead.

In any case, is there something one can do with libpython-clj to setup the call such that it's on the main thread?

[eoliphan]

Ok so i missed this #10 (comment) when i was looking through the issues. So i just tried putting the code in a -main and ran it with clojure -m but still seeing the error.

But based on that comment is this something that even can be addressed on the clj-python side?

[cnuernber]

Most likely you have to run in embedded mode. I am surprised clojure -m didn't solve the issue but especially with windowing systems there is a lot going on such as signal handling callbacks that the JVM does when it is the main process that potentially other systems do not work well with.

[eoliphan]

Embedded mode is this? https://clj-python.github.io/libpython-clj/embedded.html

[jjtolton]

I think there might be something else going on:

I was able to run this fine from repl w/o embedded.

Clojure 1.11.1, Java 17.0.9, Ubuntu 22. I'm not sure if the silicon has something to do with it or could be local install issues.

[jjtolton]

@eoliphan did you try the equivalent code in Python? I tend to find that's a pretty good troubleshooting step for some of these issues.

Make sure this works out for you from the directory where you are running your code:

env/bin/python <(cat << eof 
import gymnasium as gym
env = gym.make("LunarLander-v2", render_mode="human")
env.reset(seed=42)
eof
)

# should return 0
echo "$?"