RFR: JDK-8311983: ListView sometimes throws an IndexOutOfBoundsException [v2]

[Michael Strauß]

On Thu, 3 Aug 2023 15:13:09 GMT, Marius Hanl <mhanl at openjdk.org> wrote:

>> An IOOBE was thrown when scrolling up via the trough (-> `VirtualScrollBar#adjustValue`).
>> This happened only when it has bigger cells than the viewport. 
>> If the the uppermost cell with the index 0 is only visible (although not completely scrolled to the top) and then an attempt is made to scroll up again, the `VirtualFlow` will try to scroll to the next cell, subtracting index 0 by 1, resulting in -1 -> IOOBE.
>> 
>> The code now guards against any under or overflow.
>> 
>> This is technically a regression from https://bugs.openjdk.org/browse/JDK-8173321
>> 
>> Note: While testing with very big cells, I found out that scrolling via the trough may not work after the first time. 
>> This is because the `VirtualFlow` still creates 2 cells, although only one can be visible at a time (at least when scrolling to the next cell) (and `VirtualScrollBar` does this check, which will never be true then: `firstVisibleCell == lastVisibleCell`). This is unrelated to this fix. I can create a ticket when I have more information.
>
> Marius Hanl has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - JDK-8311983: remove JUnit5 import
>  - JDK-8311983: improve exception handling
>  - JDK-8311983: More tests

The solution is sound, as it constrains the index to a valid range. The tests work as expected.

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Marked as reviewed by mstrauss (Committer).

PR Review: https://git.openjdk.org/jfx/pull/1194#pullrequestreview-1579798358