[Rev 03] RFR: 8238954: Improve performance of tiled snapshot rendering

[Frederic Thevenet]

On Tue, 17 Mar 2020 15:31:20 GMT, Frederic Thevenet <github.com+7450507+fthevenet at openjdk.org> wrote:

>>> 
>>> 
>>> Now that the tiling is done in the `QuantumRenderer` level, I'll bring back
>>> [JDK-8189082](https://bugs.openjdk.java.net/browse/JDK-8189082). Can't this tiling be used to fix that?
>> 
>> It won't help with things in their current state, as the `RenderToImage` method that is modified in this PR is
>> currently called only by the snapshot feature in `Scene` But of course I suspect the same technique could also be used
>> to solve [JDK-8189082](https://bugs.openjdk.java.net/browse/JDK-8189082) and now is indeed a good time to investigate
>> it further. I'll have a look to see if it is possible to factorize the tiling implementation for both classes of
>> issues, in which case it would make sense to do prior to merging this PR. If it is different enough that the
>> implementation cannot be shared but only the general idea, then I suggest we address it in a different PR.  What do you
>> all think ?
>
> At first glance, the NPE in [JDK-8189082](https://bugs.openjdk.java.net/browse/JDK-8189082) occurs in the Prism layer,
> which is one level _below_ Quantum where the tiling is currently implemented, so I'm not sure tit is reachable from
> there; if we want the code to be shared, it looks like it would need to be moved even further down (maybe in the
> `ResourceFactory`?)  Also, while reusing code is generally the way to go, in such lower layers, very closely
> intertwined with the actual rendering, I'm afraid that insisting on having a "one-size-fits-all" implementation might
> get in the way of necessary case-by-case optimizations, so I'd like to have someone with a deeper knowledge  of the
> code base to weight in before starting work in that direction. Maybe @kevinrushforth could advise?

Hi everyone,

This PR hasn't seen much activity in a while, so I though I would give it a gentle kick to hopefully get it moving
again ;) As explained above, I feel a little stalled at the moment, as we need to decide whether or not it is a good
idea to try and address all or part of  JDK-8189082 within the scope of this PR, and I don't feel like I can settle
that on my own.

Thanks.

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