Changing the opacity of the toolbar switched Firefox to dark mode

[tfpf]

Closely related to https://github.com/mozilla/FirefoxColor/issues/1007, but I have more to report, so I thought I'd create a new issue.

Normally, Firefox displays the 'Minimise', 'Restore Down' and 'Close' buttons, as well as the right-click context menu, and everything else using the OS theme. However, if a custom background is added (using the 'Custom backgrounds' tab of Firefox Color), the 'Minimise', 'Restore Down' and 'Close' buttons are suddenly rendered using the Adwaita-Dark theme. Prior to Firefox 89.0.2, it would continue using the OS-themed buttons.

If the opacity of the 'Toolbar Color' (under the 'Custom colors' tab) is changed to any number below 100, even right-click context menus and download prompts start using Adwaita-Dark. Increase the opacity back to 100, and Firefox starts using the OS-themed colours again.

Firefox version: 99.0.1 OS: Manjaro Linux on KDE

[tfpf]

Closing this issue because it is a problem (some people are calling it a feature) with Firefox, and not with this extension.

• https://support.mozilla.org/gu-IN/questions/1365222
• https://support.mozilla.org/en-US/questions/1363945
• https://support.mozilla.org/en-US/questions/1360389?page=2#answer-1479952

On a fresh installation, if I enable dark mode in Firefox, it starts using the Adwaita-Dark theme. This is a clear indication that the problem is in Firefox itself.