Apple removed the /usr/bin/php binary in macOS 12 Monterey. This causes syntax highlighting to fail. However there is also a bug in the plaintext fallback path that causes the ruler to not get painted correctly.

Initially reported via the forum: https://groups.google.com/g/bluestatic/c/M4n0xN0bRpg

Fix for the plaintext view: https://src.bluestatic.org/?p=macgdbp.git;a=commitdiff;h=6eb345754cd9fc696fc1dd35bf98671bbaf47368;hp=26396882740c1a2460e54d773b155c396454df9f

Thank you for your bug report. This issue has been closed and fixed in git. This change will be available in a future release, but you can download the change at any time from the git repository, found at https://src.bluestatic.org/.