RFR: 8345348: CSS media feature queries [v21]

[Michael Strauß]

On Tue, 6 May 2025 19:26:11 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> That would be okay, except that `Scene` is allowed to be created on a background thread (it's in the class documentation), so we can't completely enforce it to be single-threaded. Once a scene is created, a user can also request its preferences. This is when we need some way to get the current platform preferences on a background thread, as otherwise users would potentially see the scene preferences suddenly change once the scene is shown.
>
> That's why I am against this background thread nonsense.  Create - yes (even though I am against this).  Access and modify properties, especially those that interact with other parts of the FX - no.
> 
> I think we should enforce the FX application thread access.

This would be a significant change, as currently `Scene` is explicitly allowed to be created _and modified_ on a background thread. This was probably always a very bad idea (because it makes the implementation so much more difficult), but how do you think we should change that?

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PR Review Comment: https://git.openjdk.org/jfx/pull/1655#discussion_r2076223572