RFR: 8193800: TreeTableView selection changes on sorting

[Kevin Rushforth]

On Tue, 2 Jun 2020 17:00:28 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.

modules/javafx.controls/src/main/java/javafx/scene/control/TreeTableView.java line 1808:

> 1807:     boolean sortingInProgress;
> 1808:     protected boolean isSortingInProgress() {
> 1809:         return sortingInProgress;

This is an implementation detail. By making it `protected` it becomes public API. You will need to make it
package-scope instead

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