Remove JavaFX JPMS enforcement

[Michael Paus]

This is deviating quite a bit from the original issue of this thread, 
isn't it?

As a side note: MethodHandles are not supported by GraalVM native image
and so this would probably collide with the attempts to get JavaFX running
on Android/iOS.

Am 20.04.20 um 11:28 schrieb Mike Hearn:
> With respect to reflection, it seems like the module system really wants
> you to use Lookup capabilities rather than "open" modules to reflection.
> That is, JFX could be changed to use
>
> var objects = FXMLLoader.load(MethodHandles.lookup(), new URL("...."));
>
> The semantics of a Lookup are that it grants whoever holds the object the
> same access rights as whoever created it. Thus if an object creates a
> Lookup and gives it to a framework, that framework can access anything the
> object could itself access.
>
> The lookup object would then be used to do reflection rather than the
> classical reflection API. With this change the API would guide you to a
> form that always works, regardless of module configuration.
>
> Due to its nature as a GUI toolkit JFX often needs to reflect over user
> code. It may be worth considering a deeper upgrade in which a Lookup object
> is provided during application startup, and passed in to the framework e.g.
> the Application class. Lookup objects can be 'teleported' so JFX components
> that wish to work with user GUI code generically can then fetch a Lookup
> from a central place. However, this wouldn't allow overriding of access
> control (i.e. FXMLLoader that takes such a lookup and teleports it to the
> right class for access, wouldn't be able to access private fields, because
> the original place where the lookup was created also couldn't).