Title: CSS Animations Level 2 Status: ED Work Status: Exploring Shortname: css-animations-2 Level: 2 Group: csswg ED: https://drafts.csswg.org/css-animations-2/ Editor: L. David Baron, Mozilla https://www.mozilla.org/, https://dbaron.org/, w3cid 15393 Editor: Brian Birtles, Mozilla https://www.mozilla.org/, bbirtles@mozilla.com, w3cid 43194 !Issues List: In Bugzilla Abstract: This CSS module describes a way for authors to animate the values of CSS properties over time, using keyframes. The behavior of these keyframe animations can be controlled by specifying their duration, number of repeats, and repeating behavior. Ignored Vars: auto-rewind
urlPrefix: https://drafts.csswg.org/web-animations-1/; type: dfn; spec: web-animations
text: active duration
text: active phase
text: active time
text: after phase
text: animation
text: animation class
text: animation effect
text: animation playback rate
text: before phase
text: composite operation
text: current iteration
text: current time
text: fill mode
text: global animation list
text: idle play state
text: idle phase
text: iteration count
text: iteration duration
text: iteration start
text: keyframe
text: pause an animation
text: paused play state
text: pending play state
text: playback direction
text: play an animation
text: play state
text: sampling
text: start delay
text: target element
text: target effect
text: target effect end
text: timeline
text: unresolved
text: default document timeline
urlPrefix: https://drafts.csswg.org/css-writing-modes-4/; type: dfn; spec: css-writing-modes-4
text: equivalent physical property; url: logical-to-physical
urlPrefix: https://drafts.csswg.org/css-values-4/; spec:css-values-4; type:dfn; text:css identifier
This is a delta specification, meaning that it currently contains only the differences from CSS Animations Level 1 [[!CSS3-ANIMATIONS]]. Once the Level 1 specification is closer to complete, it will be merged with the additions here into a complete level 2 specification.
# Animations # {#animations} Changes to any of the animation properties defined in this specification cause the corresponding {{CSSAnimation}} object and its associated objects to be updated according to the correspondence between these properties and Web Animations concepts defined in [[#keyframes]]. However, if the author modifies the animation using the Web Animations programming interface, the changes from the programming interface take precedence as follows: * After a successful call to {{KeyframeEffect/setKeyframes()}} on the {{KeyframeEffect}} associated with a {{CSSAnimation}}, any subsequent change to matching ''@keyframes'' rules or the resolved value of the 'animation-timing-function' property for the target element will not be reflected in that animation. However, if the last matching ''@keyframes'' rule is removed the animation must still be canceled. * After a successful call to {{AnimationEffect/updateTiming()}} on the {{KeyframeEffect}} associated with a {{CSSAnimation}}, for each property included in the {{AnimationEffect/updateTiming(timing)/timing}} parameter, any subsequent change to a corresponding animation property will not be reflected in that animation. For example, callingcssAnimation.effect.updateTiming({ duration: 1000 })
would cause subsequent changes to 'animation-duration' to be ignored
whilst changes to 'animation-delay' would still be reflected
in the {{KeyframeEffect}}'s timing.
* After a successful call to {{Animation/play()}} or {{Animation/pause()}}
on a {{CSSAnimation}},
any subsequent change to the 'animation-play-state' will no longer
cause the {{CSSAnimation}} to be played or paused
as defined in [[#animation-play-state]].
* After a successful call to {{Animation/reverse()}} on a {{CSSAnimation}}
or after successfully setting the {{Animation/startTime}}
on a {{CSSAnimation}},
if, as a result of that call the [=play state=] of the
{{CSSAnimation}} changes to or from the [=paused play state=],
any subsequent change to the 'animation-play-state' will no longer
cause the {{CSSAnimation}} to be played or paused
as defined in [[#animation-play-state]].
The requirement for a change to or from the [=paused play state=]
ensures that even after calling
{{Animation/reverse()}} or setting the {{Animation/startTime}}
on a running animation,
the animation continues to observe changes in 'animation-play-state'.
* After successfully setting the {{Animation/effect}} of a {{CSSAnimation}}
to null
or some {{AnimationEffect}} other than the original {{KeyframeEffect}},
all subsequent changes to animation properties other than
'animation-name' or 'animation-play-state'
will not be reflected in that animation.
Similarly, any change to matching ''@keyframes'' rules will not be reflected
in that animation.
However, if the last matching ''@keyframes'' rule is removed
the animation must still be canceled.
Note, the reference to a successful call in the above rules
is necessary to ensure that
when an exception is thrown by any of these methods,
the override behavior is not applied.
## Owning element ## {#owning-element-section}
The owning element of an animation refers to the element or
pseudo-element to which the 'animation-name' property was applied that generated
the animation.
If an animation generated using the markup defined in this specification is
later disassociated from that markup by an update to the computed value of the
'animation-name' property on the owning element, the animation is
disassociated from its owning element (that is, it has no owning
element from that point forwards).
animation's initial owning element
is elem. animation is disassociated from
element through an update to the computed value of
elem's 'animation-name' property.
elem.style.animation = 'spin 1s'; let animation = elem.getAnimations()[0]; // animation's owning element is elem elem.style.animation = ''; // animation no longer has an owning elementNote that although the owning element is often equal to the target element of an animation's target effect, this is not always the case. The following example demonstrates some of the situations where these two elements may differ.
elem.style.animation = 'move 1s'; let animation = elem.getAnimations()[0]; // animation.effect.target == elem == animation's owning element animation.effect.target = elem2; // animation.effect.target == elem2 != animation's owning element animation.effect = null; // animation.effect?.target is undefined != animation's owning element
Name: animation-composition Value: <<single-animation-composition> = replace | add | accumulate The values of 'animation-composition' have the meaning defined for the corresponding values of the composite operation defined in Web Animations [[!WEB-ANIMATIONS]]. When specified in a keyframe, 'animation-composition' defines the composite operation to use for each property specified in that keyframe until the next keyframe specifying each property.># Initial: replace Applies to: all elements Inherited: no Percentages: N/A Computed value: list, each item a keyword as specified Animation type: not animatable Canonical order: per grammar
@keyframes heartbeat {
from {
scale: 1;
animation-timing-function: ease-out;
}
30% {
scale: 1.3;
}
}
.heartbeat {
animation: heartbeat 0.3s 2s infinite;
}
@keyframes throb {
50% {
scale: 1.8;
}
}
.icon:mouseover {
animation: throb 0.4s add;
}
If these two animations are applied to the same element, normally only
one animation would apply, but by specifying ''add'' as the
'animation-composition' on the second animation, the result of the two
animations will be combined.
Since CSS Transitions [[CSS3-TRANSITIONS]] have a lower composite
order, it is possible to use 'animation-composition' to combine CSS
Animations with underlying transitions as in the following example.
.icon {
filter: blur(20px);
transition: filter 0.5s;
}
.icon:hover {
filter: blur(0px);
animation: brightness-pulse 3s infinite add;
}
@keyframes pulse {
0% {
scale: 1.1;
filter: brightness(130%);
}
10% {
scale: 1;
filter: brightness(100%);
}
}
Issue: Create pictures of these examples and verify they make sense.
Name: animation-timeline Value: <># Initial: auto Applies to: all elements Inherited: no Percentages: N/A Computed value: list, each item either a case-sensitive [=css identifier=] or the keywords ''single-animation-timeline/none'', ''single-animation-timeline/auto''. Canonical order: per grammar Animatable: no
<single-animation-timeline> = auto | none | <The 'animation-timeline' property is similar to properties like 'animation-name' and 'animation-duration' in that it can have one or more values, each one imparting additional behavior to a corresponding [=animation=] on the element, with the timelines matched up with animations as described [[css-animations-1#animation-name|here]]. Each value has type <>
<timeline-name> = <> | <>
Issue: Make it easier to use 'animation-name' to select the timeline when
'animation-timeline' is not specified. Allowing 'animation-name' to be used for
selecting timeline enables most common animations to have to use a single name
for both their keyframes and timeline which is simple and ergonomics. The
'animation-timeline' property gives authors additional control to independently
select keyframes and timeline if necessary.
## The 'animation' shorthand property ## {#animation-shorthand}
The 'animation' shorthand property syntax is as follows:
<single-animation> = <
# Animation Events # {#events}
## Event dispatch ## {#event-dispatch}
Note, this is a more general description of event dispatch than that of CSS
Animations Level 1 [[CSS3-ANIMATIONS]] since it must account for the
possibility of animations being seeked or reversed using the Web Animations API
[[WEB-ANIMATIONS]].
For the purpose of determining which events to dispatch, the
[[web-animations#animation-effect-phases-and-states|phases]] defined in
the Web Animations model are used. These definitions apply to an animation
effect, however, for the purpose of dispatching events, we consider a
CSS Animation to have the same phase as its target effect. For example,
a CSS Animation is in the before phase if its target effect
is in the before phase.
A CSS Animation that does not have a target effect is considered to be in
the idle phase if its current time is unresolved, in the
before phase if its current time is less than zero, and in the
after phase otherwise.
Similarly, subsequent references to the start delay, active
duration, current iteration, iteration start, and
iteration duration of a CSS animation should be understood to refer
to the corresponding properties of the animation's target effect.
For calculating the {{AnimationEvent/elapsedTime}} of each event, the following
definitions are used:
* interval start =
max(min(-start delay, active duration), 0)
* interval end =
max(min(target effect end - start delay,
active duration), 0)
Each time an animation is sampled and is not pending, the events to dispatch are determined by
comparing the animation's phase before and after the sample as follows:
| Change | Events dispatched | Elapsed time (ms) |
|---|---|---|
| idle or before → active | {{animationstart}} | interval start |
| idle or before → after ٭ | {{animationstart}} | interval start |
| {{animationend}} | interval end | |
| active → before | {{animationend}} | interval start |
| active → active and the current iteration of the animation's target effect has changed since the previous sample | {{animationiteration}} | (See below) † |
| active → after | {{animationend}} | interval end |
| after → active | {{animationstart}} | interval end |
| after → before ٭ | {{animationstart}} | interval end |
| {{animationend}} | interval start | |
| not idle and not after→ idle | {{animationcancel}} | The active time of the animation at the moment it was cancelled calculated using a fill mode of both. |
٭ Where multiple events are listed for a state change, all events are dispatched in the order listed and in immediate succession.
† The elapsed time for an {{animationiteration}} event is defined as follows:
1. Let previous current iteration be the current iteration from the previous sample. 1. If previous current iteration is greater than current iteration, let iteration boundary becurrent
iteration + 1, otherwise let it be current iteration.
1. The elapsed time is the result of evaluating
(iteration boundary - iteration start) ×
iteration duration).
Since the elapsed time defined in the table and procedure above is
expressed in milliseconds, it must be divided by 1,000 to produce a value in
seconds before being assigned to the {{AnimationEvent/elapsedTime}} member of
the {{AnimationEvent}}.
# DOM Interfaces # {#interface-dom}
## The CSSAnimation interface ## {#the-CSSAnimation-interface}
[Exposed=Window]
interface CSSAnimation : Animation {
readonly attribute CSSOMString animationName;
};
: animationName
:: The key used to find matching keyframes rules that define target
effect at the point when the animation was created.
This is the value of the 'animation-name' property that caused this
object to be generated.
## Requirements on pending style changes ## {#requirements-on-pending-style-changes}
Various operations may affect the computed values of
properties on elements. User agents may, as an optimization, defer recomputing
these values until it becomes necessary.
However, all operations included in programming interface defined in this
specification, as well as those operations defined in Web Animations
[[!WEB-ANIMATIONS]] that may return objects or animation state defined by this
specification, must produce a result consistent with having fully processed
any such pending changes to computed values.
elem is initially updated, a user agent may defer recalculating
the computed value of the 'animation' property.
However, the {{Animatable/getAnimations()}} method called on elem
is specified by Web Animations and can return {{CSSAnimation}} objects as
defined in this specification.
Hence, as result of the requirements in this section, the user agent must
calculate the updated value of elem's 'animation' property and
create the requested {{CSSAnimation}} object before returning its result.
elem.style.animation = 'fadeOut 1s'; elem.getAnimations()[0].pause();
elem.style.animation = 'fadeOut 1s paused'; const anim = elem.getAnimations()[0]; elem.style.animationPlayState = 'running'; console.log(anim.playState); // Should be 'running'.