1977350 - Compositor animations use unzoomed values

Status: NEW

(Core :: CSS Transitions and Animations, defect, P3)

Description

[Nikita Chaykovsky]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36

Steps to reproduce:

1. Open CodePen: https://codepen.io/newfox79/pen/empNGVQ
2. Apply zoom property to elements with keyframe animations
3. Inspect animated elements in Firefox DevTools during animation
4. Observe the relationship between element bounding box and rendered content
5. Compare with Chrome behavior (see attached screencast)

Actual results:

Element content lags significantly behind the actual element bounding box during keyframe animations. DevTools shows the bounding box animating correctly, but the rendered element content appears far behind its actual position. The animated element completely disappears when the bounding box reaches the animation end position.

Expected results:

Element content should stay synchronized with its bounding box throughout the animation. The rendered element should follow the bounding box position exactly, as shown in Chrome. Element should remain visible when animation completes.

Comment 1

[Emilio Cobos Álvarez [:emilio]]

Animated values are unzoomed, see bug 1909153. I think we need to zoom them when sending them to the compositor. Bug 1927186 is related.

The relevant code is here.