1932917 - composited transition discrepancies

Status: NEW

(Core :: CSS Transitions and Animations, defect)

Description

[Kevin Doughty]

Attachment: screencast.mp4

Steps to reproduce:

Experiments related to https://bugzilla.mozilla.org/show_bug.cgi?id=1928801 using Firefox 132 on Ubuntu, using code similar to https://searchfox.org/mozilla-central/source/layout/style/test/test_transitions_replacement_on_busy_frame.html with artificial lag while (performance.now() - startTime < lag); after changes. Unsatisfactory patches D229556 and D229614 for bug 1928801 were not applied.

Actual results:

1. Compositor transition triggered on first mousedown does not start immediately and jumps when it does.
2. Return transition after interrupt and retarget on second mousedown ends prematurely, with element jumping to final position.
3. Return transition after interrupt and retarget on fourth mousedown jumps ahead after mouse move.

Expected results:

1. First transition should start normally without a jump after the lag.
2. Second transition should end normally without a jump at the end.
3. Mouse move should not affect timing progress of fourth transition.

Comment 1

[Kevin Doughty]

Attachment: transition toggle

Comment 2

[Kevin Doughty]

Attachment: Chromium behavior

Chromium doesn't bother with adjusting start value to accomate for lag, resulting in a visual jump

Comment 3

[Kevin Doughty]

#3 might be https://bugzilla.mozilla.org/show_bug.cgi?id=1632957