RFR: 8343398: Add reducedData preference [v12]

[Andy Goryachev]

On Fri, 20 Dec 2024 18:24:29 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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 17 additional commits since the last revision:
> 
>  - Merge branch 'master' into feature/reduced-data
>  - release macOS PlatformSupport instance
>  - change enum constant names
>  - only update preferences that may have changed
>  - method name
>  - smaller diff
>  - typo
>  - store the app delegate reference in MacApplication
>  - formatting
>  - changed formatting
>  - ... and 7 more: https://git.openjdk.org/jfx/compare/cccc3ba6...b1635719

More on jerky animation: it's unrelated to the platform preferences change (which is good, for this PR anyway).

It seems the jerky movement appears after HelloJFXPanel loses focus to some other window.  Switch back, mouse over and the jerkiness starts.  Happens even with the second external monitor disconnected.

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PR Comment: https://git.openjdk.org/jfx/pull/1656#issuecomment-2557622302