bug#46827: Broken initial size of GTK3 frame

[Juri Linkov]

>>>> It seems tab-bar.el already updates only between 0 and 1.
>>>
>>> That's not what I've seen.
>>
>> There are no other values used in source code of tab-bar.el.
>> But maybe sometimes the value of tab-bar-lines
>> becomes more than 1?
>
> It's 2 after the tab bar has been produced for the first time by the
> display code.  And that is what's been causing trouble for you.  The
> value was oscillating between 1 and 2.

Very strange indeed, I can't find the constant 2 in the source code.