RFR: 8311895: CSS Transitions [v2]

[John Hendrikx]

On Mon, 31 Jul 2023 18:16:19 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> modules/javafx.graphics/src/main/java/javafx/css/TransitionEvent.java line 88:
>> 
>>> 86:      * @param eventType the event type
>>> 87:      * @param property the {@code StyleableProperty} that is targeted by the transition
>>> 88:      * @param elapsedTime the time that has elapsed since the transition has entered its active period
>> 
>> Can property be `null`?  Any restrictions on `elapsedTime`?
>
> Added a `@throws` tag.
> Interestingly, `Event` doesn't specify or assert that its `eventType` parameter is non-null. Maybe we should investigate this further.

`eventType` is not used for a lot of things, aside from deciding which list of handlers to pick.  In theory, you could have a `null` `EventType`, and register an event handler on the `null` type; except that most `addEventHandler` methods don't allow this -- they check that the event type is not `null`.

It probably would be good to reject `null` when creating an `Event`, but that's not for this PR.

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PR Review Comment: https://git.openjdk.org/jfx/pull/870#discussion_r1280688688