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Document how style traits can be derived

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Anthony Ramine 2017-08-28 09:37:25 +02:00
parent 41c3be54ea
commit ba4136b5a8
4 changed files with 44 additions and 3 deletions
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23
components/style/values/animated/mod.rs
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@ -28,7 +28,19 @@ use values::specified::url::SpecifiedUrl;
pub mod color;
pub mod effects;
/// Animating from one value to another.
/// Animate from one value to another.
///
/// This trait is derivable with `#[derive(Animate)]`. The derived
/// implementation uses a `match` expression with identical patterns for both
/// `self` and `other`, calling `Animate::animate` on each fields of the values.
/// If a field is annotated with `#[animation(constant)]`, the two values should
/// be equal or an error is returned.
///
/// If a variant is annotated with `#[animation(error)]`, the corresponding
/// `match` arm is not generated.
///
/// If the two values are not similar, an error is returned unless a fallback
/// function has been specified through `#[animate(fallback)]`.
pub trait Animate: Sized {
/// Animate a value towards another one, given an animation procedure.
fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()>;
@ -51,6 +63,8 @@ pub enum Procedure {
/// Conversion between computed values and intermediate values for animations.
///
/// Notably, colors are represented as four floats during animations.
///
/// This trait is derivable with `#[derive(ToAnimatedValue)]`.
pub trait ToAnimatedValue {
/// The type of the animated value.
type AnimatedValue;
@ -66,6 +80,13 @@ pub trait ToAnimatedValue {
pub trait AnimatedValueAsComputed {}
/// Returns a value similar to `self` that represents zero.
///
/// This trait is derivable with `#[derive(ToAnimatedValue)]`. If a field is
/// annotated with `#[animation(constant)]`, a clone of its value will be used
/// instead of calling `ToAnimatedZero::to_animated_zero` on it.
///
/// If a variant is annotated with `#[animation(error)]`, the corresponding
/// `match` arm is not generated.
pub trait ToAnimatedZero: Sized {
/// Returns a value that, when added with an underlying value, will produce the underlying
/// value. This is used for SMIL animation's "by-animation" where SMIL first interpolates from