RFR: JDK-8090647: Mnemonics : on windows we should cancel the underscore latch when an app loses focus.

[Kevin Rushforth]

On Sun, 12 Feb 2023 22:13:41 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

> This fix hides mnemonics when the Scene's Window loses focus.
> 
> Before integration, we need to make sure this is correct behavior for Mac and Linux as well. It is correct for Windows.
> 
> How to test:
> 
> - Create a control with a mnemonic
> - Alt-tab to another window (mnemonics appear when alt is pressed)
> 
> Before:
> - Window shows visible mnemonic still and reacts on them when returning
> 
> After:
> - Window hides mnemonics when focus is lost and doesn't react on them when returning

Can you provide a unit test?

Reviewers: @aghaisas @andy-goryachev-oracle

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PR: https://git.openjdk.org/jfx/pull/1030