RFR: JDK-8323706 Move SimpleSelector and CompoundSelector to internal packages [v2]

[Kevin Rushforth]

On Fri, 19 Jan 2024 10:21:05 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> Moves `SimpleSelector` and `CompoundSelector` to internal packages.
>> 
>> This can be done with only a minor API break, as `SimpleSelector` and `CompoundSelector` were public before.  However, these classes could not be constructed by 3rd parties.  The only way to access them was by doing a cast (generally they're accessed via `Selector` not by their sub types).  The reason they were public at all was because the CSS engine needs to be able to access them from internal packages.
>> 
>> This change fixes a mistake (or possibly something that couldn't be modelled at the time) when the CSS API was first made public. The intention was always to have a `Selector` interface/abstract class, with private implementations (`SimpleSelector` and `CompoundSelector`).
>> 
>> This PR as said has a small API break.  The other changes are (AFAICS) source and binary compatible:
>> 
>> - Made `Selector` `sealed` only permitting `SimpleSelector` and `CompoundSelector` -- as `Selector` had a package private constructor, there are no concerns with pre-existing subclasses
>> - `Selector` has a few more methods that are now `protected` -- given that the class is now sealed, these modified methods are not accessible (they may still require rudimentary documentation I suppose)
>> - `Selector` now has a `public` default constructor -- as the class is sealed, it is inaccessible
>> - `SimpleSelector` and `CompoundSelector` have a few more `public` methods, but they're internal now, so it is irrelevant
>> - `createMatch` was implemented directly in `Selector` to avoid having to expose package private fields in `Match` for use by `CompoundSelector`
>> - No need anymore for the `SimpleSelectorShim`
>
> John Hendrikx has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add since tags

Hmm. This suggests taking a step back. I think there are only two choices that make sense (there are a couple others, but I don't think they are useful).

1. Abandon the notion of making an incompatible change to `SimpleSelector` and `CompoundSelector`. This means that PR #1316 will need to preserve the existing `SimpleSelector` method `List<String> getStyleClasses()` and `Set<StyleClass> getStyleClassSet()`, deprecating them with simple deprecation (not for removal).
2. Make an incompatible change, meaning that at some point, the existing SceneBuilder binaries will break. We could make the transition a little less painful by providing replacement API in a release that still has the existing API (in fact, I think if we go with this option, then we _must_ do that), but the fact remains that there will then be no way to have a single binary that runs on JavaFX 21 and JavaFX 23 short of a multi-release jar file, which really isn't a good solution for this sort of problem.

Preserving the existing `SimpleSelector` methods is fairly easy and already done. So, is there any real drawback to doing this? I can't think of any.

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PR Comment: https://git.openjdk.org/jfx/pull/1333#issuecomment-1900861894