The issue has been seen here by Simon Mainey.

Affected versions

• 89.0a1 (20210324084848)
• 88.0b2 (20210323190052)

Affected platforms

• Windows 7x64

Steps to reproduce

1. Open firefox set Dark/ Light theme.
2. Unfocus the browser.
3. Observe the top part of the browser.

Expected result

• No glitches are displayed.

Actual result

• Black/White line covering the buttons.

Regression range

• With the build before bug 1694734 the issue is immediately visible when setting a Dark/Light or a custom theme. After bug 1694734 the issue is visible on the Light/Dark theme when the browser is not focused.

Notes

• Attached a screen recording.
• With webrender disabled the line is displayed but is not covering the Minimize, Close, and Maximize buttons.
• The issue is reproducible on Firefox 89.0a1 (20210324160546) with proton as well if Dark/Light themes are used (not Proton Dark/Light themes).

Hi Harry! Can you please have another look at this? Thank you!

This regression was partially fixed in D106670. This sets the remaining window background properties on :root in Windows 7/8.

https://hg.mozilla.org/mozilla-central/rev/0ce7f89cbb8a

Backed out for causing light text on light background with Alpenglow theme.

Backout link: https://hg.mozilla.org/integration/autoland/rev/d4dfcdef9bf88b6edc169dd1b26d9b31a8684c47

Backout merged: https://hg.mozilla.org/mozilla-central/rev/544196bf45f8

I don't have a Windows 7 machine to test this bug. Could someone please try this build and check that both this bug and bug 1701436 are resolved?

64-bit build: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/BKx5nswmSXevpPWSun9_Aw/runs/0/artifacts/public/build/install/sea/target.installer.exe
Treeherder: https://treeherder.mozilla.org/jobs?repo=try&revision=cfce6ff7bb1ea001f0c2305828b098da3f248aa9

I've tried the test build on a fresh profile on Windows 10 and it shows the white background in the tab bar again, unfortunately.

Sebastian

Furthermore, I can also see the white line on the Dark theme on Windows 10. (Though there is no dark line on the Light theme.

Sebastian

Thanks for trying the build. I should have clarified that I didn't expect that build to work on Windows 10. I noticed a Windows 10 issue on it shortly after I posted it, but I didn't update the try run since I was looking for Windows 7/8 feedback.

Could you please try this build? It should have the correct behaviour on all versions of Windows.

https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/bDor1K_FRBKba3wt7uuaFA/runs/0/artifacts/public/build/install/sea/target.installer.exe

Treeherder: https://treeherder.mozilla.org/jobs?repo=try&revision=94cd87001f812e7c30d1c7cf25ccad9b7672cfd5&selectedTaskRun=bDor1K_FRBKba3wt7uuaFA.0

Hi Harry! I can confirm that using the build from comment 11 on Windows 7x64 the tab bar is properly displayed with Light/ Dark/ Alpenglow and a random theme when applied and when the browser is not focused.

On Windows 10x64 I saw that the white line is still visible in with Dark theme and Alpenglow theme when the browser is not focused. But there are two scenarios:

• White bar on the top of the browser when Dark theme is selected and browser not focused screenshot: Pushlog:
  https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=b3fd546349160dfa293982cace9ba0f289d7788f&tochange=e5ee2e40acc0271d1e6032ab7e6058469cd7eef9

• White bar on the top of the browser only when AlpenGlow theme is enabled browser not focused- this is an old regression and I think it was introduced with bug 1643776:
  Last good revision: 432e42cbbc4139efd2319952ec33efe8ff9add3c (2020-08-21)
  First bad revision: 369f72130f3604c85f73a3b03b2b48f33ad9b19e (2020-08-22)
  Pushlog:
  https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=432e42cbbc4139efd2319952ec33efe8ff9add3c&tochange=369f72130f3604c85f73a3b03b2b48f33ad9b19e

Also, I cannot reproduce bug 1701436 with the provided build on Windows 10x64.

Thanks. I can reproduce the white on today's Nightly on Windows 10, but I can't reproduce it with this patch applied on the latest central. I think that may be because the latest central includes Proton tabs by default, which change the composition of the tabs bar. Since that line isn't a regression from bug 1694734, I'm going to land this patch. If the white line is an issue in tomorrow's Nightly, I'll file a new bug and address it there.

https://hg.mozilla.org/mozilla-central/rev/8d64728a5c36

Comment on attachment 9211628 [details]
Bug 1700873 - Set all window background properties on :root instead of #navigator-toolbox on Windows 7/8. r?#desktop-theme-reviewers!

Beta/Release Uplift Approval Request

• User impact if declined: Fixes theme regression on windows 7/8 that hides the close/min/max buttons.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce: Build already tested by QA.
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): CSS-only change covered by tests.
• String changes made/needed:

Comment on attachment 9211628 [details]
Bug 1700873 - Set all window background properties on :root instead of #navigator-toolbox on Windows 7/8. r?#desktop-theme-reviewers!

Thanks for adding more test coverage. Approved for 88.0b6.

https://hg.mozilla.org/releases/mozilla-beta/rev/8962db2bf2be

Hello! Verified on Windows 7x64 and Windows 10x64 with Firefox 89.0a1 (20210405094633) and 88.0b7 (20210404185932) and there are
the results:
On windows7x64 - the issue is fixed - the Tab bar is properly displayed alongside with Close, Minimize and Maximize buttons when a random or default theme is selected and the browser is focused/unfocused.

On windows 10x64 - the white line is no longer displayed with Firefox 89.0a1 but unfortunately is displayed with 88.0b7 while using Dark theme. Harry, should we close this bug as verified and open another one for the remaining one on Firefox beta 88? Thank you!

Yes, please file a new bug for the Windows 10 88 beta issue. Thanks!

Thank you, Harry. Filled bug 1703546. Closing this as verified per comment 19 and comment 20.