RFR: 8345348: CSS media feature queries [v21]

[Andy Goryachev]

On Tue, 6 May 2025 19:20:04 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> I see.  The I suggest we enforce single-threaded nature of it: everything must happen in the FX Application Thread.  I don't think it's a good idea to start synchronizing things in FX now all of a sudden.
>> 
>> Any code that wants to access FX from a background thread must do so using a combination of `runLater` and a `CountDownLatch`.
>> 
>> What do you think?
>
> 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.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1655#discussion_r2076116995