1866738 - Devtools panels produce white flash when first opened in dark mode

Status: VERIFIED FIXED

(Core :: CSS Parsing and Computation, defect)

Description

[Kestrel]

Attachment: Devtools panel white flash when first opened

STR:

1. Enable the Dark theme.
2. Open devtools (Ctrl+Shift+I).
3. Click on each devtools tab.

Sometimes the first load of the panel content produces a white flash.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=caabab6fd2b88b34f1344af40c555fed0a039949&tochange=bf9ed368ad2f3faedb517c3352f431b9f7fdfb52

Regressed by Bug 1851906.

Comment 1

[BugBot [:suhaib / :marco]]

:emilio, since you are the author of the regressor, bug 1851906, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 2

[Emilio Cobos Álvarez [:emilio]]

Attachment: Bug 1866738 - Make initial about:blank docs always transparent, even in content docshells. r=jwatt,#layout

This implements the proposed fix to
https://github.com/w3c/csswg-drafts/issues/9624, and adds a tentative
test for it.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1dcc9b5526c2
Make initial about:blank docs always transparent, even in content docshells. r=jwatt

Comment 4

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/43415 for changes under testing/web-platform/tests

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e85c84028c44
Fix test reference link.

Comment 6

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/1dcc9b5526c2
https://hg.mozilla.org/mozilla-central/rev/e85c84028c44

Comment 7

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot

Comment 8

[BugBot [:suhaib / :marco]]

The patch landed in nightly and beta is affected.
:emilio, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval. Also, don't forget to request an uplift for the patches in the regression caused by this fix.
• If no, please set status-firefox121 to wontfix.

For more information, please visit BugBot documentation.

Comment 9

[Emilio Cobos Álvarez [:emilio]]

I'd rather let this ride the trains since it is a lot riskier and affects content.

Comment 10

[Ardelean Oana, Desktop Test Engineering [:oardelean]]

Reproducible on Firefox 121.0 on Windows 10.
Verified as fixed on Firefox 122.0b3 and Nightly 123.0a1 on Windows 10, Ubuntu 22, macOS 12.