RFR: 8370446: Support dialogs with StageStyle.EXTENDED [v3]

[Andy Goryachev]

On Fri, 7 Nov 2025 01:54:56 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> Adds the `DialogPane.headerBar` property, which allows developers to specify a custom `HeaderBar` when the dialog uses the `EXTENDED` stage style.
>
> Michael Strauß has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:
> 
>  - documentation
>  - Merge branch 'master' into feature/extended-dialog
>  - move HeaderBar to DialogPane
>  - document/verify preview feature
>  - Ensure that DialogPane is always attached to Scene
>  - Lazily initialize Dialog.headerBar
>  - Support dialogs with StageStyle.EXTENDED

looks good, thanks!

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Marked as reviewed by angorya (Reviewer).

PR Review: https://git.openjdk.org/jfx/pull/1943#pullrequestreview-3435151004