Description

The loading screen draws a greeting logo beside the run summary, picked at random from two bundled pairs. On consoles that cannot encode box-drawing characters it already switches the summary box to ASCII, but it never checked the logos. Three of the four bundled logos (LOGO_WIDE, LOGO_NVIDIA, LOGO_NVIDIA_WIDE) use block or box-drawing characters.

On a cp1252 console, such as Windows output redirected to a file, LoadingScreen.summary() raised UnicodeEncodeError, and isaaclab train exited before building the environment. It failed in two cases:

• about half of redirected launches, whenever the NVIDIA pair was drawn;
• any launch on a cp1252 console 130 or more columns wide, where the wide robot logo is chosen.

Reproduced on release/3.0.0 (Windows 11) with uv run --extra isaacsim isaaclab train ... > train.log 2>&1 from Git Bash:

  File "...\isaaclab\app\loading_screen.py", line 393, in summary
    self._write(f"\n{summary}\n\n")
  ...
UnicodeEncodeError: 'charmap' codec can't encode characters in position 92-106: character maps to <undefined>

The fix

• The loading screen now keeps only the bundled logos the console can encode, and drops a pair that has none left, so a cp1252 console gets the ASCII robot greeting.
• UTF-8 consoles draw from both pairs as before.
• The check reuses the encoding test the ASCII box fallback already ran, now factored out as _can_encode.
• Remote seasonal greetings already check their own encoding and are unchanged.

Until this lands, setting PYTHONIOENCODING=utf-8 avoids the crash. The same bug is on release/3.0.0, where its simpler __init__ should take this fix as a backport.

No issue was filed for this.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Screenshots

Not applicable (console output).

Testing

• New test: test_summary_prints_on_console_that_cannot_encode_greeting_art (kitless) writes the summary to a cp1252 stream in two cases: the NVIDIA logo at standard width, and the robot pair's wide logo at 130 columns. Both cases fail on main with the UnicodeEncodeError above and pass with the fix.
• Existing tests: test_loading_screen.py and test_remote_greetings.py pass on Windows (Python 3.12, rich 14.3.4), with one exception. test_live_lifecycle_restores_normal_screen finds no alternate-screen escape, and it fails the same way on unmodified main in that shell, most likely because rich treats a process without a VT console as legacy Windows.

Checklist

Docker and GPU tests run on demand. Push the commits you want tested, then
comment run-ci on the pull request.

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with uv run isaaclab --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have validated the changed behavior with focused coverage and applied the test-audit criteria to any test changes
• I have added a changelog fragment under source/<pkg>/changelog.d/ for every touched package (do not edit CHANGELOG.rst or bump package versions — CI handles that)
• I have added my name to the CONTRIBUTORS.md or my name already exists there