RFR: 8377426: Adjust scene background to color scheme

[Michael Strauß]

On Sun, 8 Feb 2026 03:30:51 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

> When a non-opaque scene fill color is used with a stage style other than `StageStyle.TRANSPARENT`, the actual fill color is always white. This doesn't work well when the scene uses a dark color scheme. A practical solution is to allow non-opaque scene fill colors, and blend them on top of a white or black background (depending on color scheme) to derive an opaque color that adapts intuitively to the color scheme.
> 
> To test this, simply create a scene that uses a non-opaque fill color and observe the scene background when the color scheme is changed.
> 
> This PR includes a system test, run it with:
> 
> ./gradlew -PFULL_TEST=true -PUSE_ROBOT=true :systemTests:test --tests test.robot.javafx.scene.SceneFillTest.testSceneFill

It seems like the sampled color is off by a tiny bit. Are you running the test on macOS? I wonder why the rendered colors would _almost_ match, but be ever-so-slightly different compared to Windows.

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PR Comment: https://git.openjdk.org/jfx/pull/2068#issuecomment-3880514478