RFR: 8332895: Support interpolation for backgrounds and borders [v18]

[John Hendrikx]

On Sat, 10 Aug 2024 11:24:34 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> I also think that we're probably dealing with two different things that are mixed up in `StyleConverter`. But instead of having this discussion here, it probably makes more sense to have it in the context of [JDK-8333121](https://bugs.openjdk.org/browse/JDK-8333121) because it seems relevant to eventually support both short-hand and long-hand property notations.
>> 
>> I've renamed `WithReconstructionSupport` to `SubPropertyConverter` and moved it to an internal package for now. Since both `BackgroundConverter` and `BorderConverter` are not public, we can change it any way we want at a later time.
>
> Yes, that's a good idea, I was mainly worried about introducing a new public API that we can't remove later when we haven't figured out yet what the best direction would be.  With this API removed, I think we can get this merged.

One more thing.  You introduced `transition` short hand version.  Is it maybe a good idea to not do this yet until we have a better idea how to deal with them?  Shorthand properties are just a convenience; the feature will work without them.  If it was already released, then can ignore this as we're too late.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1522#discussion_r1712628315