1327271 - It's possible to accidentally scroll tabs toolbar to the empty space after closing some tabs

Status: NEW

(Toolkit :: UI Widgets, defect, P3)

Description

[arni2033]

>>>   My Info:   Win7_64, Nightly 53, 32bit, ID 20161219030207 (2016-12-19)
STR_1:
1. Open many tabs to cause overflow in tabs toolbar, close several tabs to get empty space in the end
2. Scroll tabs strip to the beginning, then to the end

AR:  Empty space in the end of tabs strip
ER:  No empty space


STR_1_detailed:
1. Open many tabs to cause overflow in tabs toolbar (N tabs). Open N more tabs.
2. Switch to the last tab.
3. Hover mouse over the (2N-3)th tab, middle-click 3 times to close 3 tabs
4. Rotate mouse wheel up twice.
5. Rotate mouse wheel down twice

AR:  Step 4 - Empty space becomes invisible.  Step 5 - There's still empty space in the end
ER:  Step 5 - there should be no empty space

Comment 1

[Emil Pasca [:emilpasca]]

User Agent:  Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:53.0) Gecko/20100101 Firefox/53.0

I have tested this issue on Windows 10 x64 with the latest Firefox release (50.1.0) and the latest Nightly (53.0a1-20170116030326) and managed to reproduce it on the latest Nightly, on the latest Firefox release (50.1.0) the issue is not reproducible.

I have performed a regression, here are the results:

Narrowed inbound regression window from [7065b2e2, f4f6a59b] (4 revisions) to [75174a72, f4f6a59b] (2 revisions) (~1 steps left)
Oh noes, no (more) inbound revisions :(
Last good revision: 75174a724d6516bb643710498862a44feeedde6d
First bad revision: f4f6a59b53106e9ff550b18e374a401ecea78e2a
Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=75174a724d6516bb643710498862a44feeedde6d&tochange=f4f6a59b53106e9ff550b18e374a401ecea78e2a

Looks like the following bug has the changes which introduced the regression:
https://bugzilla.mozilla.org/show_bug.cgi?id=1316505

Comment 2

[Randell Jesup [:jesup] (needinfo me)]

Masayuki, can you look at this?

Comment 3

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Hmm, looks like that this is not a new regression.

Starting with fixing bug 1316505, Windows and Linux start to use same path as Mac. So, perhaps, this must have already existed on mac even before fixing bug 1316505.

In tabbar, there is a dummy tab, "using-closing-tabs-spacer", at the end. When tab is closed by mouse, this is expanded to fill the space caused by closed tab. Therefore, if we should prevent to scroll to it, we need to ignore it at handling wheel events. I still don't have a smart idea how to ignore it in scrollbox element.

Comment 4

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Ah, but the spacer isn't included in <children> of the scrollbox (then, _getScrollableElements() shouldn't include the spacer). Hmm, I'm really confused by what causes the space and cannot detect the space.

Comment 5

[Randell Jesup [:jesup] (needinfo me)]

any ideas on how to address this?  We'll want to get a fix and uplift to 53 soon

Comment 6

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

No. And I don't think that this is not so important because this doesn't a bug hiding necessary UI and this is not recent regression on macOS (bug 1316505 makes Firefox for Windows and Linux use same path as macOS).

Comment 7

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Oops, I meant "I don't think that this is so important".

Comment 8

[Nathan Froyd [:froydnj]]

Neil, do you agree with comment 6?

Comment 9

[Neil Deakin]

Better to ask Dao I think.

Comment 10

[Dão Gottwald [:dao]]

Weird but not severe. I'm not even sure how this worked before bug 1316505. Perhaps tabbrowser should just call _unlockTabSizing for the wheel event?

Comment 11

[Dão Gottwald [:dao]]

(In reply to Dão Gottwald [::dao] from comment #10)
> Weird but not severe. I'm not even sure how this worked before bug 1316505.
> Perhaps tabbrowser should just call _unlockTabSizing for the wheel event?

What do you think?

Comment 12

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Could be. However, I have another concern.

When you close tabs with wheel-clicks (middle-clicks), it may be possible to scroll a little bit _accidentally_ because some mice's wheel is very sensitive. In such case, when you close a lot of tabs with wheel-clicks, it might cause closing unexpected tab accidentally.

So, marking this as INVA might be better than fixing the visual issue.

Comment 13

[Liz Henry (:lizzard) (relman/hg->git project)]

Dropping this bug from regression tracking as it seems like an edge case even if we accept it as a valid bug.

Comment 14

[Firefox Bug Husbandry Bot]

https://wiki.mozilla.org/Bug_Triage/Projects/Bug_Handling/Bug_Husbandry#Move_fix-optionals