On Sun, 8 Sep 2024 20:55:53 GMT, Michael Strauß <mstra...@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.
>>
>> `Background` and `Border` objects are deeply immutable, but not
>> interpolatable. Consider the following `Background`, which describes the
>> background of a `Region`:
>>
>>
>> Background {
>> fills = [
>> BackgroundFill {
>> fill = Color.RED
>> }
>> ]
>> }
>>
>>
>> Since backgrounds are deeply immutable, changing the region's background to
>> another color requires the construction of a new `Background`, containing a
>> new `BackgroundFill`, containing the new `Color`.
>>
>> Animating the background color using a CSS transition therefore requires the
>> entire Background object graph to be interpolatable in order to generate
>> intermediate backgrounds.
>>
>> More specifically, the following types will now implement `Interpolatable`.
>>
>> - `Insets`
>> - `Background`
>> - `BackgroundFill`
>> - `BackgroundImage`
>> - `BackgroundPosition`
>> - `BackgroundSize`
>> - `Border`
>> - `BorderImage`
>> - `BorderStroke`
>> - `BorderWidths`
>> - `CornerRadii`
>> - `Stop`
>> - `Paint` and all of its subclasses
>> - `Margins` (internal type)
>> - `BorderImageSlices` (internal type)
>>
>> ## Interpolation of composite objects
>>
>> As of now, only `Color`, `Point2D`, and `Point3D` are interpolatable. Each
>> of these classes is an aggregate of `double` values, which are combined
>> using linear interpolation. However, many of the new interpolatable classes
>> comprise of not only `double` values, but a whole range of other types. This
>> requires us to more precisely define what we mean by "interpolation".
>>
>> Mirroring the CSS specification, the `Interpolatable` interface defines
>> several types of component interpolation:
>>
>> | Interpolation type | Description |
>> |---|---|
>> | default | Component types that implement `Interpolatable` are interpolated
>> by calling the `interpolate(Object, double)}` method. |
>> | linear | Two components are combined by linear interpolation such that `t
>> = 0` produces the start value, and `t = 1` produces the end value. This
>> interpolation type is usually applicable for numeric components. |
>> | discrete | If two components cannot be meaningfully combined, the
>> intermediate component value is equal to the start value for `t < 0.5` and
>> equal to the end value for `t >= 0.5`. |
>> | pairwise | Two lists are combined by pairwise interpolation. If the start
>> list has fewer elements than the target list, the...
>
> Michael Strauß has updated the pull request incrementally with one additional
> commit since the last revision:
>
> small doc changes, copyright header
I went over the API and some of the implementation, looks good.
One sore thumb I saw were the private constructors with the `ignored` parameter
to avoid name clash. I think there could have been a better way to do that, but
since it's in the implementation I won't get into it here.
modules/javafx.graphics/src/main/java/javafx/animation/Interpolatable.java line
54:
> 52: * <td>Two lists are combined by pairwise interpolation. If
> the start list has fewer elements than
> 53: * the target list, the missing elements are copied from
> the target list. If the start list has
> 54: * more elements than the target list, the excess
> elements are discarded.
Are the elements within the lists interpolated as well? For example, if one
list is `[red, blue]` and the other is `[green]`, then `blue` is discarded as
excess, but will `red` be linearly interpolated to `green`?
modules/javafx.graphics/src/main/java/javafx/animation/Interpolatable.java line
73:
> 71: * to 1 (inclusive).
> 72: * <p>
> 73: * The returned value may not be a new instance; the implementation
> might also return one of the
"might not be a new instance". "may not" can mean that it's disallowed.
modules/javafx.graphics/src/main/java/javafx/css/TransitionEvent.java line 109:
> 107: public TransitionEvent(EventType<? extends Event> eventType,
> 108: StyleableProperty<?> property,
> 109: String propertyName,
Does this break backwards compatibility?
modules/javafx.graphics/src/main/java/javafx/scene/layout/Background.java line
292:
> 290: private Background(List<BackgroundFill> fills, List<BackgroundImage>
> images, int ignored) {
> 291: Objects.requireNonNull(fills, "fills cannot be null");
> 292: Objects.requireNonNull(images, "images cannot be null");
Are these reached if there is an interpolation from/to null with a non-null?
-------------
PR Review: https://git.openjdk.org/jfx/pull/1522#pullrequestreview-2300363858
PR Review Comment: https://git.openjdk.org/jfx/pull/1522#discussion_r1756900815
PR Review Comment: https://git.openjdk.org/jfx/pull/1522#discussion_r1759655761
PR Review Comment: https://git.openjdk.org/jfx/pull/1522#discussion_r1756906715
PR Review Comment: https://git.openjdk.org/jfx/pull/1522#discussion_r1759665107
