<Swing Dev> [9] Review Request: 8048887 SortingFocusTraversalPolicy throws IllegalArgumentException from the sort method

[Anton V. Tarasov]

Hello,

Please review a fix:

bug: https://bugs.openjdk.java.net/browse/JDK-8048887
webrev: http://cr.openjdk.java.net/~ant/JDK-8048887/webrev.0

The problem is that SortingFocusTraversalPolicy uses ROW_TOLERANCE 
conception to alter a disposition of components in a focus cycle for the 
sake of visually more appropriate traversal order. This however breaks 
the transitivity rule, which in case of using the default tim-sort algo 
leads to an exception.

We've got a number of complaints filed against this issue, so I 
eventually agreed to use reflection as suggested in JDK-7075600.

I've tested performance in the following way. In a jframe I was adding 
up to 10.000 components a) at random location (with frame's null Layout) 
so that to completely untie traversal order from container order (hard 
case for the sort), and b) sequentially, so that to have the traversal 
order pre-sorted. Then I counted time spent in the sorting procedure. 
The results of the legacy merge-sort and the default tim-sort were 
pretty close. So, the fallback to the legacy sorting algo shouldn't hit 
performance for Swing.

Just for the case of any unpredictable issue (and for the testing 
purpose), I left an ability to switch to the default tim-sort via 
setting the (undocumented) "swing.legacySortingFTPEnabled" property to 
false.

Regards,
Anton.