Firefox Customs @fedia.io mrqwerky @fedia.io 12mo ago

Vertical tabs on right

Hi. I've been experimenting with MrOtherGuy's vertical tabs script. I found that the tab bar could be moved to the right side of the window with just two simple changes:

change line 19 from: margin-left: var(--uc-vertical-tabs-width); to margin-right: var(--uc-vertical-tabs-width);
and

change line 31 from: left: 0; to right: 0;
Works for me.

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That's what I suspected. Is it just possible that a boolean preference can be tested to be true or tested to be false?
- Well, boolean cannot have any other values except for true and false - it wouldn't be a boolean if it did. Although there's sort of a third option as "pref doesn't exist" but the false category includes that.
  
  So, a @supports can query whether a preference is true. Can it also query whether a preference is false (or doesn't exist)? So, could we have a block that executes only when a preference is false (or doesn't exist)?
  
  Yes, simply using not operator with the condition:
  
  @supports not -moz-bool-pref("userchrome.my-pref.enabled"){ #nav-bar{ background: #f00 !important; } }
  
  Small caveat though, since @supports tests whether the condition is supported, it also resolves to false if the browser doesn't support the condition type. So if -moz-bool-pref() function is not supported (as is with Firefox 120 and above) then the condition is false. And thus, if you use negation then whole expression resolves to true.
  
  That means that the above expression will always apply red background to nav-bar in Firefox 120 but in older Firefox version only apply it if that pref doesn't exist or exists but is set to false
  
  You can read all about @supports at MDN although it doesn't list the Firefox internal-only -moz-bool-pref condition.
  
  Yikes! So -moz-bool-pref() has been removed in FF 120? Why would they do that? Is there are replacement?
  
  So in FF < 120, one could effectively create an IF-THEN-ELSE with @supports -moz-bool-pref(test_condition) and @supports not -moz-bool-pref(test_condition)?
  
  @supports based -moz-pref is indeed removed. But it is replaced with a media query based method, which is much nicer since it can then among other things respond to pref changes without having to restart Firefox.
  
  Oh, that's much better--to be able, for example, to toggle the vertical tabs left or right side without restarting!
  
  Thanks for the explanation and the link. That resource should prove very helpful.

13 comments