Some classes could be sealed

[Kevin Rushforth]

I agree that we should only seal existing classes that could not have 
been extended by application classes. The ones I listed in my previous 
email fit that bill, since an attempt to subclass them will throw an 
exception when it is used in a scene graph. Each documents that 
subclassing is disallowed.

Btw, we've already started making use of pattern-matching instanceof in 
the implementation anyway. It would be the first API change that relies 
on a JDK 17 feature, but for JavaFX 21, I see no problem in doing that.

-- Kevin


On 2/1/2023 9:06 AM, Philip Race wrote:
> In the JDK we've only sealed  existing classes which provably could 
> not have been extended by application classes,
> so I'm not sure about this ..
>
> also I think that might be the first change that absolutely means FX 
> 21 can only be built with JDK 17 and later ..
>
> -phil
>
> On 2/1/23 8:59 AM, Thiago Milczarek Sayão wrote:
>> Yes, sorry, I made the email title in plural, but I meant what 
>> Michael said, Node would be sealed permitting only what is needed for 
>> JavaFx internally.
>>
>>
>> -- Thiago
>>
>>
>> Em qua., 1 de fev. de 2023 às 13:48, Michael Strauß 
>> <michaelstrau2 at gmail.com> escreveu:
>>
>>     I don't think that's what Thiago is proposing. Only `Node` would
>>     be sealed.
>>     The following subclasses would be non-sealed: Parent, SubScene,
>>     Camera, LightBase, Shape, Shape3D, Canvas, ImageView.
>>     And then there are additional subclasses, which don't fit into this
>>     idea since they are in other modules: SwingNode (in javafx.swing),
>>     MediaView (in javafx.media), Printable (in javafx.web).
>>
>>
>>
>>     On Wed, Feb 1, 2023 at 5:39 PM John Hendrikx
>>     <john.hendrikx at gmail.com> wrote:
>>     >
>>     > I think this may be a bit unclear from this post, but you're
>>     proposing I think to make `Node`, `Shape` and `Shape3D` sealed. 
>>     For those unaware, you're not allowed to extend these classes
>>     (despite being public).  For example Node says in its documentation:
>>     >
>>     >    * An application should not extend the Node class directly.
>>     Doing so may lead to
>>     >    * an UnsupportedOperationException being thrown.
>>     >
>>     > Currently this is enforced at runtime in NodeHelper.
>>     >
>>     > --John
>>     >
>>     > On 01/02/2023 15:47, Thiago Milczarek Sayão wrote:
>>     >
>>     > Hi,
>>     >
>>     > NodeHelper.java has this:
>>     >
>>     > throw new UnsupportedOperationException(
>>     >         "Applications should not extend the "
>>     >         + nodeType + " class directly.");
>>     >
>>     >
>>     > I think it's replaceable with selead classes. Am I right?
>>     >
>>     > The benefit will be compile time error instead of runtime.
>>     >
>>     >
>>     > -- Thiago.
>>     >
>>
>
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