RFR: 8366201: RichTextArea: remove allowUndo parameter [v5]

[Kevin Rushforth]

On Thu, 30 Oct 2025 15:39:06 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> Original user feedback (see https://mail.openjdk.org/pipermail/openjfx-discuss/2025-August/000267.html ) called for adding an `allowUndo` parameter to `applyStyle()` and `setStyle()` methods similarly to `replaceText()`.
>> 
>> Upon further analysis, the `allowUndo` parameter was a mistake: allowing the application code to disable creating undo/redo entries messes up the internal undo/redo stack.
>> There is an internal need (`UndoableChange`), but it should not be exposed via public API.
>> 
>> This PR also adds `isUndoRedoEnabled()` and `setUndoRedoEnabled()` to the `StyledTextModel`, as well as its forwarding aliases to `RichTextArea` to allow for the application to disable undo/redo temporarily, for example, when building a document from multiple segments.
>> 
>> WARNING this is an incompatible change, permitted because of the incubator.
>> 
>> There remains a possible issue with currently unlimited size of the undo/redo stack - perhaps we should limit its depth to maybe 100-200 entries, see https://bugs.openjdk.org/browse/JDK-8370447 .
>
> Andy Goryachev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   the

LGTM

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Marked as reviewed by kcr (Lead).

PR Review: https://git.openjdk.org/jfx/pull/1941#pullrequestreview-3400410798