RFR: 8320232: Cells duplicated when table collapsed and expanded

[Marius Hanl]

On Mon, 29 Jul 2024 22:00:39 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> This PR fixes a bug where a `TableView` inside a `TitledPane` may 'duplicate' the cells. This actually has nothing to do with the `TitledPane`, but it triggered the bug easily due to its nature to change the size of his content when collapsing.
>> 
>> The expansion change of a `TitledPane` triggered an event where the underlying `VirtualFlow` was adding cells to the pile (for reuse) and later cleaning them all up without resetting the index to -1. 
>> This led to a bug where two cells had the same index and therefore received an edit event, although just one should (and is visible, the other cell has no parent -> orphan node).
>> 
>> The fix is to always reset the index to -1. This was already done before, just not everywhere, for all cells.
>> So before we clear the pile (or cells), we always reset the index to -1.
>> Added a bunch of tests, some pass before and after.
>
> modules/javafx.controls/src/main/java/javafx/scene/control/skin/VirtualFlow.java line 808:
> 
>> 806:             vertical = new BooleanPropertyBase(true) {
>> 807:                 @Override protected void invalidated() {
>> 808:                     resetIndex(cells);
> 
> minor: [cells|pile]clear() can be combined with resetIndex(), something like
> 
> 
>     private void clear(ArrayLinkedList<T> cells) {
>         for (T cell : cells) {
>             cell.updateIndex(-1);
>         }
>         cells.clear();
>     }
> 
> 
> as these operations seem to be called in pairs

Unfortunately not in the `needsRebuildCells` if condition, where we only reset the index and add all cells to the pile

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PR Review Comment: https://git.openjdk.org/jfx/pull/1521#discussion_r1696422974