1752942 - Viewport paints half-blank for Bugzilla tabs that have been in the background for a while

Status: RESOLVED DUPLICATE of bug 1742241

(Core :: Panning and Zooming, defect, P3)

Description

[Daniel Holbert [:dholbert]]

Attachment: screenshot

[I unfortunately don't have concrete STR here, but this is something that I've been hitting once a week or so that I figured I should finally file...]

Occasionally when I swap through my tabs, I'll come across a Bugzilla tab where half of the viewport is unexpectedly blank. As soon as I interact with it, it fully paints.

See attached screenshot. In this case, it was for a pinned tab; I think in some cases it happens for other tabs as well, though I don't recall for sure.

I'm using Firefox 98.0a1 (2022-01-31) on Ubuntu 21.10. I also have 225% pixel scaling configured in my Ubuntu display settings; it seems possible that's involved, though I don't know for sure.

Comment 1

[Daniel Holbert [:dholbert]]

One other possible-shot-in-the-dark: the blank area might be about the size that devtools would be if I had devtools open (though I don't have devtools open).

If I do open devtools, then of course the bug goes away (but I did notice that devtools nicely filled the blank area, which might be a clue or might not be).

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: screenshot with area between top-header and top of page

Sometimes this bug (I think it's the same bug?) manifests as Bugzilla's header-bar rendering a little ways down the page, as shown here (there's a ~1-2em-tall strip of blank space between the header bar and the top of the viewport).

I can actually reproduce this issue 100% reliably right now by
(1) Ensuring this particular pinned Bugzilla tab is not my foreground tab
(2) Restart Firefox
(3) Once this tab has finished loading (as can be seen via the favicon on its tab-title), focus the tab.

Right now, this 100% reliably gives me this blank space at the top as shown in this screenshot.

I can't reproduce in a fresh Firefox profile (even if I log in to Bugzilla) so there's something more about my regular browsing profile or my restored session that is involved here. I'll see if I can isolate the requisite factor(s) later on...

Comment 3

[Daniel Holbert [:dholbert]]

I dug further into the issue shown in comment 2 (the top header being mispositioned down a bit) since I had a reliable repro of that, and I spun off bug 1753279 for that.

I'm not sure if comment 0 is the same thing or not; it looks more severe and potentially like a distinct problem. I'll mark comment 2 as obsolete for now, and I'll add bug 1753279 as a see-also here.

Comment 4

[Daniel Holbert [:dholbert]]

Pretty confident this is a dupe of bug 1742241 (thanks tnikkel for noticing the connection), based on the screencast there (which shows a more-severe version of this).

I never had got STR for the half-blank viewport here, so I can't retest to tell for sure; I'll reopen if I happen to hit this again after the patch lands over there.

Comment 5

[mix5003]

after Bug1742241 fixed, this bug still exists. (for me i use windows 10, and no pixel scaling)
but i have no step to reproduce.

Comment 6

[Timothy Nikkel (:tnikkel)]

Can you file a new bug for that? Does the problem go away if you scroll? Can you post a screen shot? Is it bugzilla tabs? Or other websites? Can you share some urls where you seen it happen? And you're testing in a nightly with bug 1742241 fixed, right?

Comment 7

[mix5003]

i use latest nightly and STR in bug 1742241 can not reproduce now, so i think i test on nightly that include bug 1742241 fixed.
and like that bug if i scroll a little bit everything work fine.
i found this bug on bugzilla and other site too.

this is the screenshot
https://imgur.com/a/ZTEOlTz

example site that i just found.
https://docs.sentry.io/platforms/go/guides/gin/
https://bugzilla.mozilla.org/show_bug.cgi?id=1742241 (i restart firefox to make sure that i use latest firefox. and now i found that it may completely blank too.)

Comment 8

[Timothy Nikkel (:tnikkel)]

Okay thanks for that.

Are you willing to try a build with a potential fix?

Go to https://treeherder.mozilla.org/jobs?repo=try&revision=795bc914e204166608faf9fe21d4a611b51e333f then click on the green B next to Windows 2012 x64 opt (the green B will show up in the next 30 minutes or so). Then on the bottom bar click "Artifacts and Debugging Tools" and then scroll down to target.zip. Download target.zip. This is a build like Firefox Nightly but I have added one change to it that might fix your problem. You can unzip the build and run it with your main profile for a while until you either reproduce the bug or are pretty sure the bug is fixed in that build.

Comment 9

[mix5003]

i think that build fix this bug now. i restart firefox around 10 times in my main profile and i can not reproduce in that build.

Comment 10

[Timothy Nikkel (:tnikkel)]

Thanks for testing, sounds like we'll need a fix like bug 1753881 to fix all the cases where this can happen.

Comment 11

[Timothy Nikkel (:tnikkel)]

Would you mind testing one more build? I have a different fix that I want to see if it fixes your problem.

Same instructions as before, goto
https://treeherder.mozilla.org/jobs?repo=try&revision=d76c41dbd0e0a3662dfa2f70e698f872e1b660dc
click the green B next to Windows 2012 x64 opt. Then on the bottom bar click "Artifacts and Debugging Tools" and then scroll down to target.zip. Download target.zip.

Comment 12

[mix5003]

i think this should fixed it too. around 10 times in my main profile, i can not reproduce this bug. (current nightly i can reproduce this bug by restart firefox 2-3 times)