RFR: 8351357: Add canary system test checking if Stage receives focus on show [v6]

[Lukasz Kostyra]

On Tue, 15 Jul 2025 17:43:33 GMT, Martin Fox <mfox at openjdk.org> wrote:

> I'm sure I ran MenuDoubleShortcutTest on Windows before submitting it.

This also started being a problem at some later point in time; on my machine tests used to do a full run with no failures with the Gradle daemon being enabled. I can't unfortunately pinpoint when the problems started happening, I only found out after the fact that `SetForegroundWindow()` enforces conditions mentioned in the PR description.

AFAIK `--no-daemon` consistently helps (I use MinGW on my Windows box). @kevinrushforth also mentioned offline that he disables the Gradle daemon in his machine-wide `gradle.properties` so he never encountered these problems.

I also submitted a (for now draft) PR for the `isFocused()` API fix - https://github.com/openjdk/jfx/pull/1849. It is independent from this test but the test was helpful with checking the behavior while writing the test. Feedback is welcome!

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PR Comment: https://git.openjdk.org/jfx/pull/1804#issuecomment-3077604344