JavaFX Launch Failure on Ubuntu from JNI

[Michael Hall]

> On Jan 19, 2022, at 11:40 AM, Steve Hannah <steve at weblite.ca> wrote:
> 
> com.sun.javafx.application.PlatformImpl startup
> Exception in thread "Thread-5" java.lang.IllegalStateException: This
> operation is permitted on the event thread only; currentThread =
> Thread-5

Searching on…
com.sun.javafx.application.PlatformImpl startup Exception in java.lang.IllegalStateException: This operation is permitted on the event thread only;

Gets some hits. Somewhat interestingly given…

> They are included in the classpath.  I'm not using modules.

This one https://stackoverflow.com/questions/67854139/javafx-warning-unsupported-javafx-configuration-classes-were-loaded-from-unna <https://stackoverflow.com/questions/67854139/javafx-warning-unsupported-javafx-configuration-classes-were-loaded-from-unna>
Says…

The Warning

JavaFX only supports being loaded as named modules. In other words, JavaFX only supports being loaded from the module-path, not the class-path.

With…

> java.lang.IllegalStateException: Not on FX application thread;
> currentThread = Thread-31
>        at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:295)

Searching only on 
checkFxUserThread 
gets a number of similar sounding issues. Mostly they seem to suggest timing issues or taking various steps to ensure you are on the correct thread. 

e.g.
https://stackoverflow.com/questions/29449297/java-lang-illegalstateexception-not-on-fx-application-thread-currentthread-t <https://stackoverflow.com/questions/29449297/java-lang-illegalstateexception-not-on-fx-application-thread-currentthread-t>
https://github.com/sarxos/webcam-capture/issues/469 <https://github.com/sarxos/webcam-capture/issues/469>