RFR: 8177945: Single cell selection flickers when adding data to TableView

[Jose Pereda]

On Fri, 6 Nov 2020 23:33:08 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> As discussed in the JBS [issue](https://bugs.openjdk.java.net/browse/JDK-8177945), there are some inconsistencies in the use of `VirtualContainerBase::requestRebuildCells` from `VirtualContainerBase::updateItemCount()`, which is implemented in the different skin classes for virtualised controls `TableViewSkinBase`, `ListViewSkin` or `TreeTableViewSkin`.
>> 
>> The latter already commented out this call (related to JDK-8155798 and JDK-8147483). 
>> 
>> This PR removes now the calls to `VirtualContainerBase::requestRebuildCells` from `TableViewSkinBase`  (except for the case `itemCount = 0` based on JDK-8118897 and JDK-8098235) and `ListViewSkin`.
>> 
>> A test is provided for TableView, that verifies that the `selected` pseudo-class state remains set for the selected cell while adding more items. Without this fix, as the cells are rebuilt, the pseudo-class states are clean and set all over again, thus the flickering.
>> 
>> For ListView, the test rt_35395 (JDK-8091726) is updated, as now there are way less calls to updateItem.
>
> modules/javafx.controls/src/main/java/javafx/scene/control/skin/ListViewSkin.java line 359:
> 
>> 357: 
>> 358:         updatePlaceholderRegionVisibility();
>> 359:         if (newCount == oldCount) {
> 
> Does this also need the same `else if (oldCount == 0)` test that you added to `TableViewSkinBase`?

`TableViewSkinBase` has an `itemsChangeListener` that triggers the `rowCountListener`, which sets `itemCount = 0` when an item has been replaced. `ListViewSkin` uses a different approach via `listViewItemsListener` -> `flow::setCellDirty`.

However, the same approach (`itemCount = 0`) is used in both cases when the list of items is cleared, so I'll add it here as well.

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PR: https://git.openjdk.java.net/jfx/pull/348