RFR: 8354943: [Linux] Simplify and update glass gtk backend: window sizing, positioning, and state management issues [v60]

[Thiago Milczarek Sayao]

On Wed, 17 Sep 2025 18:01:47 GMT, Martin Fox <mfox at openjdk.org> wrote:

> > I've been going through the review and tests here, I still have some more code to review but I did notice there are some test failures on Windows:
> 
> I've tracked down one issue with these tests. Some of them try to verify where the top stage is by sampling from a fixed location in screen coordinates, typically calling `getColor(100, 100)`. Depending on the platform and stage style this might sample a pixel from the Label in the middle of the top stage's scene. This happens on Windows when the top stage's style is EXTENDED. This doesn't happen on macOS because the top stage gets shifted down to avoid the menu bar (the test tries to position the top stage at y = 0 but it ends up at y = 25 instead).

Moved the label to the bottom right. Another cause of this "shifting" behavior are desktop panels.

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PR Comment: https://git.openjdk.org/jfx/pull/1789#issuecomment-3306536408