1858405 - Private tab displays the old background theme during site loading

Status: VERIFIED FIXED

(Firefox :: Private Browsing, defect, P1)

Description

[Simona Badau, Desktop QA]

Attachment: Screen Recording 2023-10-11 at 3.26.56 PM.mov

Found in

• Nightly 120.0a1

Affected versions

• Nightly 120.0a1

Tested platforms

• Affected platforms: Windows 11, macOS 12, Ubuntu 22.04 x64

Preconditions

• In about:config - set "browser.privatebrowsing.felt-privacy-v1" to true

Steps to reproduce

1. Open a new private window.
2. Visit any website and pay attention to the tab's background during the page loading process.

Expected result

• The tab's background color should align with the new theme while the site is loading.

Actual result

• The tab's background color displays the old background during site loading. Please see the screencast for more details.

Regression range

• Not a regression.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

:sbadau, if you think that's a regression, could you try to find a regression range using for example mozregression?

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1847102

Comment 3

[:cmkm]

Attachment: Bug 1858405 - Prevent PBM new tab background color flash when loading a webpage r?mhowell

Comment 4

[:cmkm]

Attachment: bug_1858405_removed.mov

Behavior with rule removed (bug_1858405_removed.mov)

Comment 5

[:cmkm]

Attachment: bug_1858405_gradient.mov

Behavior with new gradient set (bug_1858405_gradient.mov)

See comment #4 for a recording of the rule removed for comparison. Dão, would you mind confirming this is the desired behavior?

Comment 6

[Dão Gottwald [:dao]]

(In reply to Cieara Meador [:cmkm] (she/her) from comment #5)

Created attachment 9364512 [details]
bug_1858405_gradient.mov

Behavior with new gradient set (bug_1858405_gradient.mov)

See comment #4 for a recording of the rule removed for comparison. Dão, would you mind confirming this is the desired behavior?

Yeah, that doesn't look great. Could you find out where the transient dark gray background (before the gradient shows up) comes from? I don't see that in Nightly (without "felt-privacy-v1" enabled).

Comment 7

[:cmkm]

I was able to repro on Nightly, so I ran through mozregression and it pointed me at the patch for Bug 1859945. Emilio, do you know what might be going on here in regards to the grey flash that was introduced when opening a new tab?

Comment 8

[Emilio Cobos Álvarez (:emilio)]

To be clear, that's with felt-privacy-v1=true? I can't see that on current nightly. Also presumably that'd be an issue before bug 1845779 as well?

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1847102

Comment 10

[:cmkm]

(In reply to Emilio Cobos Álvarez (:emilio) from comment #8)

To be clear, that's with felt-privacy-v1=true? I can't see that on current nightly. Also presumably that'd be an issue before bug 1845779 as well?

Sorry, no - the pref isn't necessary to see the behavior. The grey flash Dão mentioned in Comment #6 appears with or without the felt privacy pref. I'm on macOS with the system light/dark theme and I'm able to see the behavior on current Nightly.

Comment 11

[Ryan VanderMeulen [:RyanVM]]

Did bug 1865868 improve this?

Comment 12

[:cmkm]

Yes it did, this is on track to land this week after review, so it should also be upliftable

Comment 13

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/73e866e79c97
Prevent PBM new tab background color flash when loading a webpage r=mhowell,desktop-theme-reviewers,dao

Comment 14

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/73e866e79c97

Comment 15

[BugBot [:suhaib / :marco/ :calixte]]

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

• If yes, please nominate the patch for beta approval.
• If no, please set status-firefox121 to wontfix.

For more information, please visit BugBot documentation.

Comment 16

[:cmkm]

Comment on attachment 9364226 [details]
Bug 1858405 - Prevent PBM new tab background color flash when loading a webpage r?mhowell

Beta/Release Uplift Approval Request

• User impact if declined: Annoyance of a flash of the old PBM background color as pages load, if user's in the Felt Privacy experiment
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: 1. Set browser.privatebrowsing.felt-privacy-v1 to true

2. Open a private window
3. Navigate to any page and pay attention to the tab's background during the page loading process

Expected result: The tab's background color should align with the new theme while the site is loading.

• List of other uplifts needed: Bug 1865868
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): This fix is styling-only and affects only PBM in the Felt Privacy experiment; the patch it's dependent on affects only temporary about:blank documents during page loading
• String changes made/needed: n/a
• Is Android affected?: No

Comment 17

[Simona Badau, Desktop QA]

Verified as fixed on the latest Nightly 122.0a1 - tested on macOS 13, Ubuntu 22.04 x64 and Windows 10 x64.

Comment 18

[Ryan VanderMeulen [:RyanVM]]

Comment on attachment 9364226 [details]
Bug 1858405 - Prevent PBM new tab background color flash when loading a webpage r?mhowell

Approved for 121.0b9.

Comment 19

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/fe848ad8162b

Comment 20

[Simona Badau, Desktop QA]

Verified as fixed on Firefox 121.0b9 (Build ID: 20231208091859) - tested on macOS 13, Ubuntu 22.04 x64 and Windows 10.