RFR: 8343398: Add reducedData preference [v10]

[Kevin Rushforth]

On Thu, 19 Dec 2024 21:03:58 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> The `reducedData` preference instructs applications to minimize internet traffic, as users might be on a metered network or a limited data plan.
>> 
>> This corresponds to the following OS settings:
>> 
>> Windows: Settings -> Network and Internet -> Ethernet/WiFi -> Metered connection
>> macOS: Settings -> Network -> Ethernet/WiFi -> Network Settings -> Low data mode
>> Ubuntu: Settings -> Network -> Wired/WiFi -> Metered connection
>> 
>> Change notifications work consistently on Windows and macOS. On my Ubuntu 24 system, the GIO `network-changed` signal is not sent when I only toggle the "metered connection" flag in network settings (and there's no signal specifically for low-data mode). The new value is only picked up when the connection changes by coming offline or going online.
>
> Michael Strauß has updated the pull request incrementally with one additional commit since the last revision:
> 
>   change enum constant names

The changes all look good now.

I did notice one thing in macOS while reviewing the changes in `PlatformSupport.m`. The PlatformSupport object stays around after the GlassApplication is terminated via finishTerminating. It will continue to process platform events, including making Java upcalls even after the FX toolkit is stopped. You would only see this with a Swing interop app that initializes FX and then later terminates it while keeping AWT alive. I think it is preexisting, and doesn't seem to be causing any problems. It might be worth a P4 follow-up issue to investigate.

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Marked as reviewed by kcr (Lead).

PR Review: https://git.openjdk.org/jfx/pull/1656#pullrequestreview-2517714143