Perspective Designer freeze opening views with embedded JRE on Kubuntu 20.04

Something in recent weeks' (or longer?) upgrades from Ubuntu broke the Perspective Designer for me on my daily driver. Switching to the system JVM makes it all work for me, across all versions I poked at:

$ java --version
openjdk 11.0.19 2023-04-18
OpenJDK Runtime Environment (build 11.0.19+7-post-Ubuntu-0ubuntu120.04.1)
OpenJDK 64-Bit Server VM (build 11.0.19+7-post-Ubuntu-0ubuntu120.04.1, mixed mode, sharing)

Interestingly, the embedded JRE 11.0.11 appears to still work (launching from a v8.1.7 instance).

Embedded launchers from v8.13, v8.1.17, v8.1.24, and v8.1.28 fail to open views. (Chromium sitting idle, too--not burning CPU like some older bugs.)

While stuck, nothing interesting shows up on the designer's text console, nor when running the designer process from a terminal.

It isn't hurting me to run the system java, but I though y'all should know.

{JxBrowser tests against Ubuntu 20.04, which is what prompted me to try the system java.}

Anything interesting show up in a thread dump?

Hadn't looked. (I failed to quickly figure out how to get such a dump from chromium.)

Let me add that the chromium debug port that it reports to the console opened just fine while the Perspective designer was stuck. It showed the basic structure of the view in question and was fully responsive. The designer itself was not otherwise stuck--I could still navigate to and work with Vision windows and other project resources.

A Java thread dump might show something obvious in JxBrowser's stack. It's worth a try at least.

Hmmm.

I just switched a couple of my designers back to the embedded JRE (to collect those thread dumps) and they work now.

I hate Heisenbugs.

:man_shrugging:

I'll leave this here for others to find.

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