1964537 - testcase flickers blank on each view transition

Status: NEW

(Core :: CSS Transitions and Animations, defect)

Description

[Daniel Holbert [:dholbert]]

STR:

1. Load https://bugzilla.mozilla.org/attachment.cgi?id=9485210 (testcase 2 from bug 1964210)
2. Press "tab" to focus the button (or click the button)
3. Press spacebar repeatedly to press the button a bunch.

ACTUAL RESULTS:
Most of my spacebar-presses result in a flicker where the viewport goes blank for a moment.

EXPECTED RESULTS:
No such flicker.

Firefox 140.0a1 (2025-05-05) (64-bit) shows ACTUAL RESULTS.
Chrome 137 dev shows EXPECTED RESULTS (no flicker).

You can also see this in a more automated way with the original testcase from bug 1964210 -- just load that testcase, type "50" or any large number into the textbox, and hit the button. In Firefox Nightly, this makes the testcase start flickering to be blank/nonblank repeatedly.

Comment 1

[Daniel Holbert [:dholbert]]

(Note, in case anyone else trips this... the first time I was testing this, I was rapidly clicking the button in attachment 9485210 [details] and I happenedto trigger a crash - bp-e9561eb9-1555-4fe2-91cf-ca7060250505 . I'm pretty sure I hit the same crash last week when working with this same testcase. But I haven't managed to make that reproduce on-purpose/on-demand yet.)

Comment 2

[Daniel Holbert [:dholbert]]

Here's a profile of me performing the STR:
https://share.firefox.dev/3RPwJsk

If you mouse across the screenshots track, you can see it flickering blank every now and then. Here's one example, from zooming in on the profile -- the viewport is blank around the middle of this region:
https://share.firefox.dev/3RPzjOV

Comment 3

[Emilio Cobos Álvarez (:emilio)]

I think this is basically bug 1959648.