RFR: JDK-8302355: Public API for Toolkit.canStartNestedEventLoop()

[Marius Hanl]

On Wed, 15 Feb 2023 16:06:59 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> Also, please provide a test.

I was thinking of writing a simple unit test and implementing some kind of dummy nested event loop mechanism inside the `StubToolkit`, which will follow the real implementation.
But then I still only test the `StubToolkit` instead of the real `QuantumToolkit`.
Does this make sense or is a system test the right way here?

> modules/javafx.graphics/src/main/java/javafx/application/Platform.java line 396:
> 
>> 394:     /**
>> 395:      * Indicates whether a nested event loop can be started from the current thread in the current state.
>> 396:      * Note that a nested event loop is not allowed outside an event handler.
> 
> You need to be explicit about whether or not this method must be called on the JavaFX thread. The two logical choices are:
> 1. Add a statement indicating that this method must be called on the JavaFX Application thread. The toolkit method would then call `checkFxUserThread()`, as do the other nested event loop methods.
> 2. Add a statement indicating that this method may be called on any thread (and that it will return false if not on the JavaFX application thread). The toolkit method would then first call `isFxUserThread()` and return  false if not.
> 
> I might lean towards option 2, but don't have a strong preference.

Should I also adjust the `Toolkit` javadoc or only the `Platform` one?

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PR: https://git.openjdk.org/jfx/pull/1031