Affected versions

• 100.0a1
• 99.0

Affected platforms

• Ubuntu 20.04

Steps to reproduce

1. Set the Alpenglow theme from about:addons#themes
2. Open the Hamburger menu - More tools - Customize toolbar…
3. Observe the background of the Customize page

Expected result

• The background of the page is opaque.

Actual result:

• The background of the page is transparent, the files/folders behind can be spotted.

Regression range

• Last good revision: e3ed61b61357e78f89a316d68dd5cc69ffd099ac
• First bad revision: eb8c23dda78d3ed4bf244c3e72c76e81833086ff
• Pushlog:
  https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=e3ed61b61357e78f89a316d68dd5cc69ffd099ac&tochange=eb8c23dda78d3ed4bf244c3e72c76e81833086ff
• Potential regressor: 1509931

Other notes

• The Title bar check fixes the transparency problem.
• I can’t reproduce it on other platforms.
• Reproducible both with light and dark themes set at the OS level.

Set release status flags based on info from the regressing bug 1509931

:emilio, since you are the author of the regressor, bug 1509931, could you take a look?
For more information, please visit auto_nag documentation.

I don't see this on Fedora, neither on Wayland or X11... Anca, can you attach the about:support information on your machine?

Anything illuminating in the comment 4 about:support?

Not really, that's a regular XWayland setup which I did test... :/

Set release status flags based on info from the regressing bug 1509931

Same issue reproduces on Ubuntu 20.4 using build 100.0b5 (20220412185818) and theme https://addons.mozilla.org/de/firefox/addon/tiger-eyes-turquoise/

Pretty sure this will be fixed by bug 1765685.