RFR: 8332895: Support interpolation for backgrounds and borders

[Florian Kirmaier]

On Sun, 2 Jun 2024 18:50:20 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

> This PR completes the CSS Transitions story (see #870) by adding interpolation support for backgrounds and borders, making them targetable by transitions.
> 
> More specifically, the following types will now implement `Interpolatable`.
> 
> - `Insets`
> - `Background`
> - `BackgroundFill`
> - `BackgroundImage`
> - `BackgroundPosition`
> - `BackgroundSize`
> - `Border`
> - `BorderImage`
> - `BorderStroke`
> - `BorderWidths`
> - `CornerRadii`
> - `ImagePattern`
> - `LinearGradient`
> - `RadialGradient`
> - `Stop`
> 
> Note that this PR also changes the specification of `Interpolatable` to make users aware that they shouldn't assume any particular identity of the object returned from the `interpolate()` method. This allows the implementation to re-use objects and reduce the number of object allocations.

First, Thank you for working on these transitions!

> Note that this PR also changes the specification of Interpolatable to make users aware that they shouldn't assume any particular identity of the object returned from the interpolate() method. This allows the implementation to re-use objects and reduce the number of object allocations.

Can you elaborate on this?
Are changes in the Region.background still trigger change events?
If not, is there a mechanism to get them? Like Transform.onTransformChanged?
Are the previous immutable objects like Background and Border now mutable?

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PR Comment: https://git.openjdk.org/jfx/pull/1471#issuecomment-2144762597