Missing 'from' selector on @keyframes works erratically

• Component: Animations
• Status: RESOLVED WORKSFORME

When @keyframes rules are used to animate elements and the 'from' selector is missing, the animation behaves erratically.
See this example:

https://stackblitz.com/edit/web-platform-vmalvc?file=styles.css

styles.css contains this @keyframes rule:

@keyframes dash {
  to {
    stroke-dashoffset: 0;
  }
}

Running the project in Safari Technology Preview, I find that the line is animated erratically: anywhere from 20-60% of the time. If I add the 'from' keyword:

@keyframes dash {
  from {
    stroke-dashoffset: 14.7;
  }
  to {
    stroke-dashoffset: 0;
  }
}

The animation seems to happen consistently.

W3C says that 'If a 0% or from keyframe is not specified, then the user agent constructs a 0% keyframe using the computed values of the properties being animated.' That computation does not seem to be happening consistently. (Other browsers like Chrome work fine.)

(Reference: https://www.w3.org/TR/css-animations-1/)

[Radar WebKit Bug Importer]

<rdar://problem/84903751>

[Antoine Quint]

Can you still reproduce the issue with Safari Technology Preview 139? I'm not able to reproduce it myself.

Verified: no longer reproduces.

[Antoine Quint]

Great! Thanks for checking.