JavaFX Launch Failure on Ubuntu from JNI

[Kevin Rushforth]

Hard to say what's going on without more information. What are the JVM 
args you use for launching? Are the JavaFX modules jlink'ed into the JDK 
or loaded via --module-path? As a debugging aid, you might try setting 
the system property "javafx.verbose" to "true" before loading your 
MyApplication class.

-- Kevin


On 1/19/2022 9:40 AM, Steve Hannah wrote:
> The following issue only seems to occur on Linux (Ubuntu 20.04.1), and only
> when I try to launch the JVM from a custom C launcher using JNI.  It does
> not occur when launching the JVM as a separate process using the "java"
> binary.  It also does not occur on MacOS when using the same C launcher
> using JNI.
>
> When I call MyApplication.launch(args). (where MyApplication extends the
> JavaFX Application class), I get the following stack trace:
>
> Jan. 19, 2022 8:54:27 A.M. 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
>          at com.sun.glass.ui.Application.checkEventThread(Application.java:447)
>          at com.sun.glass.ui.Application.setName(Application.java:200)
>          at com.sun.javafx.application.PlatformImpl.lambda$setApplicationName$2(PlatformImpl.java:142)
>          at com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
>          at java.base/java.security.AccessController.doPrivileged(Native Method)
>          at com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
>          at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
> Exception in Application start method
> Exception in thread "Thread-31" Failed to show docs
> java.lang.IllegalStateException: Not on FX application thread;
> currentThread = Thread-31
>          at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:295)
>          at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(QuantumToolkit.java:458)
>          at com.sun.javafx.tk.quantum.QuantumToolkit.exit(QuantumToolkit.java:828)
>          at com.sun.javafx.application.PlatformImpl.lambda$tkExit$16(PlatformImpl.java:624)
>          at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
>          at com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
>          at java.base/java.security.AccessController.doPrivileged(Native Method)
>          at com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
>          at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
> java.lang.RuntimeException: Exception in Application start method
>          at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:901)
>          at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:196)
>          at java.base/java.lang.Thread.run(Thread.java:829)
> Caused by: java.lang.IllegalStateException: Not on FX application
> thread; currentThread = Thread-6
>          at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:295)
>          at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(QuantumToolkit.java:458)
>          at javafx.stage.Stage.<init>(Stage.java:254)
>          at javafx.stage.Stage.<init>(Stage.java:240)
>          at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:845)
>          at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
>          at com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
>          at java.base/java.security.AccessController.doPrivileged(Native Method)
>          at com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
>          at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
>
>
> I have tried a few different versions of JavaFX (11, 11.0.2, 17.0.1),
> running on a few different JDK installs (all JDK11).  Above stacktrace is
> from 17.0.1.
>
>  From the C application that launches the JVM, I have tried running directly
> on the main thread, and also launching it in a fresh thread using pthreads
> - but same issue.  I am running this inside an application written in Go
> but the JNI code is all in C.
>
> It appears as though JavaFX is unable to create its application thread for
> some reason.  Does anyone have any suggestions on reasons why this would be
> the case?  Are there some system properties that need to be there which
> would have been bootstrapped by the "java" binary, but would not when the
> JVM is launched via JNI?
>
> Any suggestions appreciated.  I've been banging my head on this for a while
> now.
>
> Best regards
>
> Steve