New Firefox Nova UI causes several themes to have a white border below the toolbar (v157.0)

Add-ons Themes
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firefox white line
firefox white line737×593 212 KB

This seems to be related to the toolbar_bottom_separator theme property no longer functioning the way it used to in the latest version (Firefox v157.0). I have noticed several themes that have this issue, including themes that I created as well. These work fine when Proton UI (old UI) is used. This does somewhat ruin the aesthetic of these themes, so I hope a fix is available.

Examples of Themes impacted by this issue:

https://addons.mozilla.org/en-US/firefox/addon/dark-green-3d/

https://addons.mozilla.org/en-US/firefox/addon/stripes-x3/

https://addons.mozilla.org/en-US/firefox/addon/dark-wood-by-matze/

https://addons.mozilla.org/en-US/firefox/addon/keqing-card-genshin-impact/

https://addons.mozilla.org/en-US/firefox/addon/morning-in-the-forest/

This issue seems to arise if toolbar_bottom_separator is set to a semi-transparent color, which is the case by default in Firefox Color. Solid colors might not have this issue. As a result, even the Preset themes provided within Firefox Color seem to have this issue in v157.0 as well.

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Hi Nightfire, that’s a great catch, thank’s for reporting!

This comes from toolbar_bottom_separator. With Nova, that property no longer only colors the bottom edge of the toolbar. It now acts as a separator next to or below the toolbar and around the page.

My understanding is that the lighter background behind the separator shows through, which is why it looks like a white line.

For your own themes, the quickest fix should be to set toolbar_bottom_separator to a solid (fully opaque) color, for example, the same color as your toolbar or frame. If that doesn’t clear it up, please let me know here.

I am sharing this with the team working on Nova themes so they can look at the semi-transparent case. I will update this thread once I know more. Firefox Color is outdated and unmaintained, so we should really unpublish it until we have a new version.

Thank you!

-Christos