RFR: 8263322: Deadlock when calling Application.launch in the FXThread after Platform.startup [v2]

[Kevin Rushforth]

On Wed, 10 Mar 2021 17:00:41 GMT, Florian Kirmaier <fkirmaier at openjdk.org> wrote:

> Initalize the FX runtime via Platform.startup and then launch an Application on another thread (should succeed)
I don't think that should succeed. I would expect it to throw an exception. If that would be the case, then both startup-methods would result in different states, which wouldn't be so good.

No, this really should succeed. Internally, it is a similar case to what the special Java launcher method does when launching a Java class that extends `Application` and which may have a main method that calls `Application.launch`. We check the various cases of launching an application with/without it extending `Application` in the tests under [tests/system/src/test/java/test/launchertest/](https://github.com/openjdk/jfx/tree/master/tests/system/src/test/java/test/launchertest/).

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PR: https://git.openjdk.java.net/jfx/pull/421