The old behavior most definitely has advantages. The FF built-in scrolling looks nice but as it is now it's necessary to have the left/right arrow buttons visible. I too used to do without them.
Thanks for looking into it
do you need to see part of the right most tab or also in part of the left most tab ?
I checked this stuff in my old FF 3.6.28 with TMP 0.3.8.7 when presumably the FF built-in scroll function was *not* used, as I understand it?
Depending a little on how the setting of min width of tabs fit with the current width of the browser window, the behaviour of the setting "When tabs don't fit width: Scrollable without buttons" is this:
1. When clicking on the rightmost visible tab, the bar will auto-scroll at least a part of a tab width leftwise, exposing approx half (or the whole) next tab to the right so it can be clicked easily. A.s.o. until one reaches the end of the tabbar.
2. The above does not apply to the leftmost visible tab, clicking it will not trigger any rightwise auto-scrolling, to (partially) expose the next tab to the left. I'm not sure if this was ever the case, but I seem to remember that it once was...
I for one would prefer it to work symmetrically like this, so that #2 would be analogous to #1.
how much width you need for left-side of the next tab
Minimum 33% of the current tab width is my suggestion. I'm ambivalent here, I usually have my tabs rather narrow to fit more of them, so for me 50% would be better... There may be some caveats here that I don't realise now, something that would look ugly or make the tabbar behaviour awkward.
i'm not sure all user will love this, so maybe i will add new option for the case tab bar is in single row
"Always show part of the left and right most tabs" or something like this.
i need your help with the proper wording for this
No, not "always show part of the left and right-most tabs". That's not what I want at least, I just want at least 33% of the next tab to appear (auto-scroll) whenever the current left- and rightmost tab is clicked [or rather made active]. What happens at the other end of the tabbar in this situation is irrelevant. It just becomes what it will.
Sure, some users might find this behaviour annoying (although it was like this at the right-most end of the tabbar previously!) so a new option could be appropriate. It should only be valid IMO if the setting is:
"When tabs don't fit width: Scrollable without buttons"
Because if the arrow buttons are there, then you have to use them, that's what they're for.
My suggestion for a wording of this potential new option:Auto-scroll when activating left-/rightmost visible tab