Bugzilla

(In reply to Petruta Horea [:phorea] from comment #9)
> - This issue reproduces now with High Contrast Black and Firefox Light theme. Since this is an unusual combination, should I file it as follow-up?

Yes, there is still a bug here, and I think it's due to missing a -moz-proton check around  this rule https://searchfox.org/mozilla-central/rev/fa48ebee58d59fa846919c3e2c3122b08db57c9c/browser/themes/shared/urlbar-searchbar.inc.css#462-465
As you said this is a not so common case, so I don't think we'll fix it, considered it would require an uplift and would become pointless with the release of Proton. I'd prefer to concentrate on ensuring HC is right in Proton, since we handled the most common case here.
Thus I'd suggest to not file a bug and accept that bug exists.

> - With High Contrast Black and Firefox Dark theme, I notice that address bar panel highlights are grey (Proton like), as opposed to blue (default text selection in HCM). In this case, should the highlight follow OS's direction or browser's?

I think High Contrast users should use the Default theme and if they really want to pick a theme, they'll hopefully pick an LWT theme that satisfies their need, rather than a broken. LWT themes, like Dark, hardcode various colors and may not be a good choice for HC users, in general, but again it's their choice. I don't think that's a bug, the user requested that theme, and the theme may hardcode some colors by choice.

(In reply to Petruta Horea [:phorea] from comment #9)
> - This issue reproduces now with High Contrast Black and Firefox Light theme. Since this is an unusual combination, should I file it as follow-up?

Yes, there is still a bug here, and I think it's due to missing a -moz-proton check around  this rule https://searchfox.org/mozilla-central/rev/fa48ebee58d59fa846919c3e2c3122b08db57c9c/browser/themes/shared/urlbar-searchbar.inc.css#462-465
As you said this is a not so common case, so I don't think we'll fix it, considered it would require an uplift and would become pointless with the release of Proton. I'd prefer to concentrate on ensuring HC is right in Proton, since we handled the most common case here.
Thus I'd suggest to not file a bug and accept that bug exists.

> - With High Contrast Black and Firefox Dark theme, I notice that address bar panel highlights are grey (Proton like), as opposed to blue (default text selection in HCM). In this case, should the highlight follow OS's direction or browser's?

I think High Contrast users should use the Default theme and if they really want to pick a theme, they'll hopefully pick an LWT theme that satisfies their need, rather than a broken one. LWT themes, like Dark, hardcode various colors and may not be a good choice for HC users, in general, but again it's their choice. I don't think that's a bug, the user requested that theme, and the theme may hardcode some colors by choice.