Bug 1913322. That style requires the slot element to not have it's own box - previously that was already the case since <slot>s have display: contents by default, but with that style that specific slot was given display: flex and thus have its own box. Thus, we remove it.

Which reminds me, by making it have display: contents the tabs cannot overflow to scrollable box anymore. Instead they just overflow invisibly, which is no bueno.

Doesn't really sound like a company that I would want to do any business with then.

But if you’re using the built-in auto-updater (like people tend to do on Windows and macOS), then it happens automatically in the background, unless you tell the auto-updater to not update automatically.

Definitely does not work that way on my Windows 10 installation. When update is available, Firefox will have a "Restart to install updates" in menu button notification - but the files are not replaced on disk until you actually close (or restart) Firefox and thus Firefox continues to work normally.

What can happen though is that if you run another instance (ie. another profile) of Firefox while the first one has "staged" the update then that another instance can trigger the files to actually be replaced on disk but you would very deliberately do that.

Firefox shouldn't force you to restart and update like that unless something else, such as your package manager, has already replaced the executable files on your disk. In such a scenario Firefox doesn't have any option except to inform you to restart it (well I guess it could choose to crash). But the mechanism that forced the update is the package manager.

The non-standard :-moz-lwtheme is now considered invalid syntax, so using that invalidates the whole ruleset it's used in. Featurewise the equivalent would be to check for existense of lwtheme attribute on root element. But the way you have written your rules the you have never even needed :-moz-lwtheme selector to begin with since you are applying the same rules when that matches and doesn't match. So you can just write this to get your desired selection color in urlbar:

#urlbar ::-moz-selection{
  background-color: #3040cf !important; /*it's green again; want to fix this too*/
  color: white !important;
}

There's also a checkbox in settings > general section.

Felix Mikolasch, data protection lawyer at noyb: “Mozilla has just bought into the narrative that the advertising industry has a right to track users by turning Firefox into an ad measurement tool. While Mozilla may have had good intentions, it is very unlikely that 'privacy preserving attribution' will replace cookies and other tracking tools. It is just a new, additional means of tracking users.”

Sigh... I cannot for the life of me figure how anyone could think that enabling PPA (even by default) means that advertising industry has somehow right to track folks. Like dude, the entire point of PPA is that advertisers could then get to know if/when their adverts are working without tracking people.

The argument that "It is just a new, additional means of tracking users" also doesn't really make sense - even if we assume that this is new means of tracking. I mean, sure it technically is new addition, but it's like infinity+1 is still infinity - it doesn't make a difference. The magnitude of this one datapoint is about the same as addition of any new web api (I mean there are lots that shouldn't exist - looking at you chromium.. but that's besides the point).

File a complaint over use of third-party cookies and actual tracking if you want to be useful - this complaint just makes you look like an idiot.

At first glance that sounds like for some reason the tab selection is super slow occasionally. The selected attribute on .tabbrowser-tab happens very soon after you click the tab, but the other stuff happens and eventually the .tab-background gets its selected styling. Sounds like that would sometime take several frames during which the background-color is not covered by normal selected-tab styling.

You can try to replace [selected] there with [visuallyselected] which gets added a bit later, but if there's some weird latency going on then that might still be too soon.

In horizontal tabs the tab is really removed only after its closing animation is done - in that case when its width reaches 0px. I have not looked what the closing transition is in vertical tabs - but it stands to reason that it might be its height. If that is the case (which again is just a guess) then you should make sure that you aren't setting min-/max-/height for tabs anywhere that then would prevent the tab from being getting to 0px height.

I'm not sure if we're talking about the same thing, but the first thing I noticed from that video is that it seems as if tabs aren't closing properly. Same kind of deal happens with horizontal tabs if you unconditionally force min-width or max-width for tabs.

That being said, I wouldn't put too much effort into supporting vertical tabs yet because it's constantly changing still.

Also, Servo was originally more or less a testbed for new rendering pathway (webrender) which, when ready, was then integrated into Firefox.

The main window has a [inDOMFullscreen] attribute when a video or other website element is being shown in fullscreen mode. So use that instead of [sizemode="fullscreen"]

True, and I agree - for this feature to be effective the site-specific rules need to be maintained properly.

All I'm saying is that it leaving some query parameters unremoved is not indicative of the feature not working. If you want to add more query parameters to the removed list then feel free to open a bug about it.

That feature removes parameters that are known to be used for tracking. It does not remove all query parameters willy-nilly. For example on youtube it should remove si, feature and kw parameters as well as a set of parameters on a list that applies to all websites. However, pp parameter is not in that to-be-removed list.

As an example v parameter is for video id on youtube, it would be kinda silly if that was removed, so the feature kinda has to do some site specific action.

Something like this should work:

#navigator-toolbox::after{
  height: 1px;
  background-image: linear-gradient(to right, blue, yellow, cyan, magenta, red);
  order: 1000;
  content: "";
  display: flex !important;
}

It is, but like it says you need to get window_control_placeholder_support.css for window controls to show properly at the top.

What exactly did you do to do what you did?

Reader mode can show images as well though. I mean, it isn't always successful in doing so - probably because there's about a million different ways a random website could show an image - but reader mode can show images that it thinks are part of the actual content.

Indeed. Also, the auto-open PiP is super nice feature I've been using a lot.