[Rev 01] RFR: 8193800: TreeTableView selection changes on sorting

[Kevin Rushforth]

On Tue, 2 Jun 2020 18:02:50 GMT, Ambarish Rapte <arapte at openjdk.org> wrote:

>> Issue:
>> In TreeTableView, in case of Multiple selection mode, if nested items are selected, then TreeTableView does not
>> retain/update the selection correctly when the tree items are permuted(either by `sort()` or by reordering using
>> `setAll()`).  Cause:
>> 
>> 1. For permutation, the current implementation uses `TreeModificationEvent` to update the selection.
>> 2. The indices from these TreeModificationEvents are not reliable.
>> 3. It uses the non public `TreeTablePosition` constructor to create intermediate `TreeItem` positions, this constructor
>> results in another unexpected TreeModificationEvent while one for sorting is already being processed. 4. In case of
>> sorting, there can be multiple intermediate TreeModificationEvents generated, and for each TreeModificationEvent, the
>> selection gets updated and results in selection change events being generated. 5. Each time a TreeItem is expanded or
>> collapsed, the selection must be shifted, but shifting is not necessary in case of permutation. All these issues
>> combine in wrong update of the selection.  Fix:
>> 
>> 1. On each TreeModificationEvent for permutation, for updating the selection, use index of TreeItem from the
>> TreeTableView but not from the TreeModificationEvent. 2. Added a new non public TreeTablePosition constructor, which is
>> almost a copy constructor but accepts a different row. 3. In case of sorting, send out the set of selection change
>> events only once after the sorting is over. 4. In case of setAll, send out the set of selection change events same as
>> before.(setAll results in only one TreeModificationEvent, which effectively results in only one set of selection change
>> events). `shiftSelection()` should not be called in case of permutation i.e. call `if (shift != 0)`
>> Verification:
>> The change is very limited to updating of selection of TreeTableView items when the TreeItems are permuted, so the
>> change should not cause any other failures. Added unit tests which fail before and pass after the fix.
>
> Ambarish Rapte has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Change isSortingInProgress to package scope

The algorithm looks correct to me for sorting. How much regression testing have you done for cases where rows or
columns are inserted?

I left a few comments, and will complete my testing in parallel.

modules/javafx.controls/src/main/java/javafx/scene/control/TreeTableView.java line 1822:

> 1821:     public void sort() {
> 1822:         sortingInProgress = true;
> 1823:         final ObservableList<TreeTableColumn<S,?>> sortOrder = getSortOrder();

I presume that sorting cannot be called recursively?

modules/javafx.controls/src/main/java/javafx/scene/control/TreeTableView.java line 1807:

> 1806:
> 1807:     boolean sortingInProgress;
> 1808:     boolean isSortingInProgress() {

Minor: the field itself can be private.

modules/javafx.controls/src/main/java/javafx/scene/control/TreeTablePosition.java line 82:

> 81:     // This causes issue by triggering a new TreeModificationEvent while one TreeModificationEvent
> 82:     // is being handled currently.
> 83:     // This is kind of a copy constructor with different value for row.

The first three lines of added comments don't really belong here. I would just document the new constructor as a
copy-like constructor (with a different row) and mention that it is used by the TreeTableView::sort method.

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PR: https://git.openjdk.java.net/jfx/pull/244