RFR: 8238954: Improve performance of tiled snapshot rendering [v15]

[Kevin Rushforth]

On Wed, 1 Jul 2020 09:44:05 GMT, Frederic Thevenet <github.com+7450507+fthevenet at openjdk.org> wrote:

>> Issue JDK-8088198, where an exception would be thrown when trying to capture a snapshot whose final dimensions would be
>> larger than the running platform's maximum supported texture size, was addressed in openjfx14. The fix, based around
>> the idea of capturing as many tiles of the maximum possible size and re-compositing the final snapshot out of these, is
>> currently only attempted after the original, non-tiled, strategy has already failed. This was decided to avoid any risk
>> of regressions, either in terms of performances and correctness, while still offering some relief to the original
>> issue.  This follow-on issue aims to propose a fix to the original issue, that is able to correctly decide on the best
>> snapshot strategy (tiled or not) to adopt before applying it and ensure best performances possible when tiling is
>> necessary while still introducing no regressions compared to the original solution.
>
> Frederic Thevenet has updated the pull request incrementally with one additional commit since the last revision:
> 
>   - Removed unused imports in Snapshot2Test
>   - Fixed comments in QuantumToolkit
>   - Only initialize RTT cache if needed

Marked as reviewed by kcr (Lead).

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PR: https://git.openjdk.java.net/jfx/pull/112