RFR: 8187309: TreeCell must not change tree's data

[Ajit Ghaisas]

On Wed, 2 Feb 2022 14:18:18 GMT, Jeanette Winzenburg <fastegal at openjdk.org> wrote:

> Issue was TreeView commit editing implementation violated the spec'ed mechanism:
> 
> - no default commit handler on TreeView
> - TreeCell modifying the data directly
> 
> Fix is to move the saving of the edited value from cell into a default commit handler in tree and set that handler in the constructor.
> 
> Added tests that failed/passed before/after the fix (along with a sanity test for default commit that passed also before). Also fixed a test bug (incorrect registration of custom commit handler, see [JDK-8280951)](https://bugs.openjdk.java.net/browse/JDK-8280951) in TreeViewTest.test_rt_29650 to keep it passing.

modules/javafx.controls/src/main/java/javafx/scene/control/TreeView.java line 341:

> 339:         setFocusModel(new TreeViewFocusModel<T>(this));
> 340: 
> 341:         setOnEditCommit(DEFAULT_EDIT_COMMIT_HANDLER);

You are adding the default edit commit handler to TreeView. Although it seems to be correct, this default handler is likely to be overwritten if the user code already has a setOnEditCommit() call. This is shown by the test_rt_29650() failure in TreeviewTest.java which you have corrected.

The changes done in this PR makes TreeView similar to ListView and TableView in terms of having the default edit commit handler.

Unfortunately, I do not see how can we avoid user code accidentally overwriting the default edit commit handler. Documenting this possibility seems to be the only way ahead.
Any other idea?

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PR: https://git.openjdk.java.net/jfx/pull/724