1219638 - [e10s] Tab separator flashes when opening a new tab

Status: RESOLVED WORKSFORME

(Firefox :: Theme, defect, P5)

Description

[(Currently slow to respond) Philipp Sackl [:phlsa] (Firefox UX) please use needinfo]

Attachment: Screen_Shot_2015-10-29_at_11_40_52.png

When opening a new tab, the tab separator briefly flashes and overlays the new tab button. It shouldn't do that.

Tested on OS X and Windows 10.

Comment 1

[:Gijs (he/him)]

Can you still reproduce this? I just tried, and I don't see it, on either beta or current nightly (tested on OS X and Windows 8.1)

Comment 2

[(Currently slow to respond) Philipp Sackl [:phlsa] (Firefox UX) please use needinfo]

I was still able to reproduce it in todays Nightly on Windows 10 but it seems to be really dependent on how busy the machine is. Looks like there are a few frames when the overlapping happens, and when the machine is busy, those are the frames that freeze quite often.

Comment 3

[:Gijs (he/him)]

Rakhi, can you reproduce this on your windows 10 machine if you try a few times?

Comment 4

[Rakhi(:rakhisharma)]

Yes! I am able to reproduce it.

Comment 5

[Rakhi(:rakhisharma)]

So, I am able to reproduce the bug, but still not able to find out how to fix this tab separator overlap. I noticed few things while trying:

1. I was not able to inspect it because overlap appears for a second only. I try to increase transition time so that I can inspect but no! overlap still appears for a second.
2.The selector that depends on [visuallyselected] not being set here, which is causing the separator to get shown here. This is different in e10s vs non-e10s because that attribute doesn't get set immediately. By disabling e10s, tab separator overlap doesn't happened(probably because in e10s we switch tabs asynchronously).

Any idea about how fix this?

Comment 6

[Dão Gottwald [:dao]]

Sounds like more fallout from bug 1009628.

Comment 7

[Mike Conley (:mconley) (:⚙️)]

I wonder if it makes sense to hide the tab separators before and after a tab that is animating? That'd maybe sidestep this a little.

Can you think of any problems with that solution, shorlander?

Comment 8

[:Gijs (he/him)]

(In reply to Mike Conley (:mconley) - (Needinfo me!) from comment #7)
> I wonder if it makes sense to hide the tab separators before and after a tab
> that is animating? That'd maybe sidestep this a little.
> 
> Can you think of any problems with that solution, shorlander?

Then you can't see the tab at all, right? You'd only see the [+] button moving with no separator before it. It'd also be weird for e.g. closing tabs in the middle of other tabs - you'd see a continuous blurb of the text of 3 tabs with no separators between them for a bit. Am I misunderstanding what you're proposing, Mike?

Orthogonally, it doesn't really make sense to me that the tab separator ever displays *on top of* the new tab button. That shouldn't even be 'physically' possible in terms of the margins/paddings involved. Feels like we're missing something.

Comment 9

[Mike Conley (:mconley) (:⚙️)]

(In reply to :Gijs Kruitbosch from comment #8)
> Then you can't see the tab at all, right? You'd only see the [+] button
> moving with no separator before it. It'd also be weird for e.g. closing tabs
> in the middle of other tabs - you'd see a continuous blurb of the text of 3
> tabs with no separators between them for a bit. Am I misunderstanding what
> you're proposing, Mike?

Yeah, that's accurate - I think my idea was a little half-baked.

> 
> Orthogonally, it doesn't really make sense to me that the tab separator ever
> displays *on top of* the new tab button. That shouldn't even be 'physically'
> possible in terms of the margins/paddings involved. Feels like we're missing
> something.

Do we know that the separator is actually appearing on top of the newtab button? The screenshot doesn't make it super clear - since (from what I remember) the new tab button has a transparent background (and just shows an outline when hovered), perhaps we're seeing a tab separator leaking through that transparency?

Comment 10

[Stephen Horlander [:shorlander]]

(In reply to Mike Conley (:mconley) - (Needinfo me!) from comment #9)

> Do we know that the separator is actually appearing on top of the newtab
> button? The screenshot doesn't make it super clear - since (from what I
> remember) the new tab button has a transparent background (and just shows an
> outline when hovered), perhaps we're seeing a tab separator leaking through
> that transparency?

I made the new tab button background opaque and I still the separator appearing. So it appears to be on top of it.

Comment 11

[Gregory Pappas [:gregp]]

Unable to reproduce