glitch fix and cosmetic improvement

[sonofevil]

fix: rule briefly failed to apply when opening new tab improvement: divider alignment

[sonofevil]

Uncertain whether the cosmetic fix will look good in all themes. The dividers are weird .tab-stack::before pseudo-elements, not actual dividers. Whether they look centered depends on the default padding. I tried directly styling them with userChrome.css, but it seems to get ignored.

[MrOtherGuy]

What dividers are you talking about? Tabs don't have any dividers in Firefox normally. I don't think that the margin-right: -5px rule is ever going to be applied anyway, because tabs.css line 86 defines margin for .tabbrowser-tab which is always going to override that rule. The link is for mozilla-central (nightly), but release Firefox also has a similar rule.

Applying zero-padding also overflowing pinned tabs might be a good idea though. Both are kinda janky, but I guess this is less janky than pinned tabs suddenly getting wider when overflow happens.

[sonofevil]

The theme with the dividers is "System theme — auto 1.3", the default theme on my installation but they also appear in other themes I've tried. It's possible that this is somehow Linux-specific.

The rule is

  @supports -moz-bool-pref("userChrome.tab.static_separator")
.tab-stack::before, .tab-stack::after {
  display: block;
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  z-index: 1;
  width: 0px;
  height: 100%;
  border-right: 1px solid var(--toolbarseparator-color);
}

It's in chrome://browser/skin/userChrome.css.

It looks like this:

You are right that there is another rule overriding it. On my first test it worked but after reload it doesn't. Is there any reason not to use !important here?

[sonofevil]

Hm, I need to tweak this, it looks pretty bad. I'll take it out of the pull request.

[MrOtherGuy]

Yeah, maybe you have old Firefox version like ESR or something, because @supports -moz-bool-pref(some_pref) hasn't worked since Firefox 120 - there is a media-query version of it nowadays. That would also explain why you see different behavior. Or perhaps your package-manager uses modified Firefox.

The target is Firefox built by Mozilla, which indeed also has some OS specific rules, but I don't think that's the case here.

[MrOtherGuy]

Right, but let's indeed make also overflowing pinned tabs get smaller, I think that's good. Thanks!