RFR: 8321722: Tab header flickering when dragging slowly other tabs and reordering uncompleted

[Andy Goryachev]

On Mon, 11 Dec 2023 18:36:35 GMT, Jose Pereda <jpereda at openjdk.org> wrote:

> This PR prevents changes in direction when dragging a tab header over a TabPane control, if delta value is zero, which can happen with slow drag events, in order to prevent starting and stopping too frequently the animation of the target tab header in opposite directions.

the fix works on macOS 14.1.1

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Marked as reviewed by angorya (Reviewer).

PR Review: https://git.openjdk.org/jfx/pull/1304#pullrequestreview-1775972862