RFR: 8323706: Remove SimpleSelector and CompoundSelector classes [v9]

[John Hendrikx]

On Mon, 2 Sep 2024 12:45:02 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:
> 
>   Reject CSS where compound selectors don't consist of simple selectors

I made the small change suggested in `BinarySerializer` and created a CSR.  I wasn't entirely sure on the "compatability" part and whether or not it should take into account removal of deprecated classes.  With the removal of `SimpleSelector` and `CompoundSelector` code that managed to use them (by casting) will no longer compile for sure.  I'm not 100% sure if it could possibly be binary compatible (ie. if a previously compiled class casts to these types) but I suspect it won't be.

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PR Comment: https://git.openjdk.org/jfx/pull/1333#issuecomment-2324677111