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/52c2e2a0...b1635719

Looks good (macOS).

An observation: when running `HelloJFXPanel`, noticed that the FX animation restarts each time the appearance preference gets changed between light and dark modes.  This might be an existing issue since it can also be observed in the master branch.

I am not entirely sure this is expected, since neither the color of the animated rectangle nor the background color changes.  It's unrelated to the changes in this PR (but might be related to the way the platform notifications are being processed).

Another observation related to the same animation, and also can be observed with the master branch: when one runs the `HelloJFXPanel` app, the initial animation is smooth and is not affected by mouse over.  Once the platform light/dark mode preference gets changed, however, the movement becomes jerky on mouse over.

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Marked as reviewed by angorya (Reviewer).

PR Review: https://git.openjdk.org/jfx/pull/1656#pullrequestreview-2518158802