RFR: 8343336: Add reducedScrollBars preference

[Michael Strauß]

On Thu, 31 Oct 2024 03:56:30 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

> This PR adds another accessibility preference that is available on all supported desktop platforms:
> 
> 1. **Windows**: Settings -> Accessibility -> Visual Effects -> Always show scroll bars
> 2. **macOS**: System Settings -> Appearance -> Show scroll bars
> 3. **Ubuntu**: Settings -> Accessibility -> Seeing -> Always show scroll bars
> 
> When the OS setting is changed, all platforms report updates that can be observed in JavaFX.
> The manual test application `test/manual/events/PlatformPreferencesChangedTest` can be used to test the feature.

My thinking is that a particular preference should be useful and almost universally supported on the desktop platforms to make it into JavaFX API. The number of preferences we might consider are pretty limited, so I don't expect `Platform.Preferences` to explode in size and scope.

I think this is a minor addition that doesn't change anything substantial about `Platform.Preferences`, and as such doesn't need a major discussion since the arguments are basically the same since the introduction of platform preferences. However, if you or others are interested in having a discussion, we can of course do that.

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PR Comment: https://git.openjdk.org/jfx/pull/1618#issuecomment-2450541522