User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:77.0) Gecko/20100101 Firefox/77.0

Steps to reproduce:

I have 2 monitors, one on top of the other, on the bottom I have a 1920x1080 monitor and on the top a 1440x900 monitor. My GPU is a Nvidia GTX 1060 FE 6Gb.

I just updated my Windows 10 Pro to version 2004 and Firefox to 77.0.1 and now I got an annoying bug (don't know who's fault is Firefox or Windows or both).

Actual results:

I have 2 Firefox windows, when I maximize one of them on the bottom screen I get a white bar on the bottom of the top screen (see attached image).

As you can see on the image attached there's a white bar appearing on top of the tabs, in fact that's the limit between both monitors, so the tabs are flush (maximized) with the bottom monitor and the white bar starts on the top monitor. The reason the white bar stops on the right side is because the top monitor has a smaller resolution than the bottom one (1440 vs 1920 pixels in width).

I only get this when I maximize the windows.

Expected results:

There shouldn't have any white bars on the bottom of the top monitor, just as it was before I updated my Windows and Firefox.

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Can you attach a copy of your about:support?

I attached it, copying it as a data structure.

Thanks. If you change gfx.webrender.all to true does that make the problem go away?

No, it doesn't change anything.

After you enabled that pref and restarted about:support listed Webrender next to "Compositing"? Just want to make sure that webrender did indeed get enabled.

Yes it is next to Compositing.

The easiest way to determine if this is the result of a Firefox change or a Windows change is to run an older version of Firefox.

Using https://mozilla.github.io/mozregression/ is probably the easiest way to do that.

will I lose my tabs?

mozregression will use a completely separate profile from your main profile, so your main profile should be completely unaffected. You shouldn't even need to close your main Firefox.

I will try to test this on a Virtual Machine before, give me some time as this might take a while since I would have to update Windows there.

I can confirm this is a bug relating Windows 10 version 2004 + Firefox 77.0.1.

I tested the following scenarios:

Firefox 76 - Win 10 1903 - OK
Firefox 77.0.1 - Win 10 1903 - OK
Firefox 77.0.1 - Win 10 1909 - OK
Firefox 77.0.1 - Win 10 2004 - ERROR

So I would say something changed on Windows 10 2004 and Firefox isn't compatible with it. I would bet on the APIs Firefox uses to hide the Windows Title Bar.

Since my tests were under a virtual machine, I don't think this is related to my GPU.

If someone wants to test this but Windows Update isn't showing the May 2020 (2004) update, you can get it using the Windows Update Assistant

(or maybe that's a bug on the May 2020 Update, braking previous APIs for Window configuration. Then someone from Firefox would have to contact Microsoft on this, as I am sure you guys should have the means for it).

Bug 1638709 might also related to Windows version 2004.

Apparently Window 10 May 2020 Update (2004) introduced WDDM 2.7 (Windows Display Driver Model) and "should improve multi-monitor support" (you know, 2 steps forward, 1 step backwards... the more features you add, the more bugs comes along). So here are my suppositions on what might be going on:

1 - WDDM 2.7 breaks previous functionality intentionally and documented this.
2 - WDDM 2.7 breaks previous functionality intentionally and didn't document this.
3 - WDDM 2.7 breaks previous functionality unintentionally (a bug on Windows so not Firefox fault).
4 - Some internal component of Windows that manages multi-monitors wasn't upgraded properly to deal with WDDM 2.7. That would include the Windows Title rendering of windows (a bug on Windows so not Firefox fault).

I am not a Windows developer so I might be totally wrong on this, just following a feeling on what could be the root of this.

According to this article "WDDM 2.7 in Windows 10 version 2004 requires Nvidia drivers 450.12, Intel driver 27.20.100.7859 and above." But Nvidia is only servicing 446.14 for my GTX 1060 so this might be a corner case while the new drives don't go mainstream? Don't know, just another wild guess.

Have flagged this for Microsoft.

michelfeinstein, when you get a minute, could you file a bug with Microsoft using their Feedback hub? https://support.microsoft.com/en-ca/help/4021566/windows-10-send-feedback-to-microsoft-with-feedback-hub-app - this is at their request. This helps them track incoming issues.

We can also reach out to Nvidia so they are aware and we can see if there is a workaround.

Sure, I didn't do it before because I thought it would get lost in the middle of hundreds of thousands of feedbacks they must receive everyday.

Done: https://aka.ms/AA8myqx, please forward this feedback to them.

I agree that Nvidia should be aware of this as well as WDDM 2.7 needs new drivers from their part.

Thank you - feedback has been forwarded to both MSFT and Nvidia. We will keep folks updated.

michelfeinstein: Does setting gfx.webrender.compositor to false makes the issue stop happening?

My question is inspired by https://bugzilla.mozilla.org/show_bug.cgi?id=1638709, since you're also running Windows 10 version 2004.
I'm not sure (can someone at Mozilla confirm?), but I believe gfx.webrender.compositor indicates whether the DirectComposition API is used.
Knowing whether DirectComposition use is associated with the bug would help me file an internal NVIDIA bug to the appropriate team.

@aleino I upgraded my driver to Game Ready 451.48 and set gfx.webrender.compositor to false, the bug persists.

michelfeinstein: Thanks, I'll file an nvidia bug to see if someone can reproduce this. (I don't have access to similar hardware and windows 10 version at the moment, myself.)

Also, please provide the following information for each display:

• The interface (HDMI/DP?)
• The model.

From your attached about:support I can see the refresh rates: 1920x1080@60Hz, 1440x900@75Hz.

I've filed NVIDIA bug 3036665 to investigate this.

Have 2 stacked displays here are their details:

Top Monitor: Samsung SyncMaster 931bw - DVI
Bottom Monitor: Samsung SyncMaster PX2370 - HDMI

Those are pretty old but I guess Nvidia has a storage with the museum pieces somewhere.

Thanks! I've updated the internal NVIDIA bug with this information.
Maybe we don't have those exact displays, but I think we ought to be able to match resolution, refresh rate and interface.

If possible give us an update here as things are solved on Nvidia's side, thanks in advance.

Will do!
I follow both the internal Nvidia bug and this one, so if you add any new information here, I'll also update the Nvidia bug.

Hello, since we are at a point where it seems we are looking for possible causes, I also have the same issue. It also started right after 2004 update.

Hopefully my about:support and monitor setup can somehow help.
Top monitor: Iiyama Proline XB2483HSU - HDMI
Bottom monitor: Dell P2417H - HDMI

Let me know if there's anything I can check or try to help.

obacz.krzysztof: Thanks. Can you share some more details?
For each monitor: I'd like to know the refresh rate and resolution.

From the attached about:support, I see:
GPU: NVIDIA GeForce RTX 2080 SUPER
Driver: 26.21.14.4614 (So that translates to 446.14.)

Yes, GPU and driver version are correct. Both monitors have 1920x1080 at 60Hz.
I'm not sure if it would be relevant in any way but I also have a 3rd monitor snapped to the lower left corner of the bottom monitor. It's LG 27gl850 with resolution 2048x1080 at 144Hz, connected via Display Port.

obacz.krzysztof: Thanks, I've added this information to the corresponding internal Nvidia bug.

One more thing came to mind:
Driver version 451.48 recently became available for the 2080 SUPER (and probably for other GPUs as well).
It can be found here https://www.nvidia.com/download/index.aspx?lang=en-us.

There is/was some reason to believe this newer driver may fix certain issues with Windows 10 version 2004.
michelfeinstein did not have any luck, though. (https://bugzilla.mozilla.org/show_bug.cgi?id=1643260#c23)
Still, if you have time, it would be helpful to find out whether driver 451.48 resolves your issue.
If the issue persists, that's just a bit more verification that you're seeing the same issue.

(In reply to aleino from comment #33)

obacz.krzysztof: Thanks, I've added this information to the corresponding internal Nvidia bug.

One more thing came to mind:
Driver version 451.48 recently became available for the 2080 SUPER (and probably for other GPUs as well).
It can be found here https://www.nvidia.com/download/index.aspx?lang=en-us.

There is/was some reason to believe this newer driver may fix certain issues with Windows 10 version 2004.
michelfeinstein did not have any luck, though. (https://bugzilla.mozilla.org/show_bug.cgi?id=1643260#c23)
Still, if you have time, it would be helpful to find out whether driver 451.48 resolves your issue.
If the issue persists, that's just a bit more verification that you're seeing the same issue.

Forgot to request information.

I've installed drivers in version 451.48 - sadly no luck. I've even tried performing a clean installation by removing my drivers using Guru3D DDU.
It doesn't seem to matter which monitor is at the top. I get the same thing on all 3 monitors when I move them to the top. Interface also doesn't seem to matter but I can only test Display Port and HDMI.

@aleino are you sure this a bug on Nvidia's side? My guess would be Microsoft's fault as the displays work just fine and this bar only appear when the window is maximized, which AFAIK is a Windows feature unrelated to the GPU or drivers.

(In reply to michelfeinstein from comment #36)

@aleino are you sure this a bug on Nvidia's side? My guess would be Microsoft's fault as the displays work just fine and this bar only appear when the window is maximized, which AFAIK is a Windows feature unrelated to the GPU or drivers.

I've considered it might be a Microsoft-bug, but it doesn't change much until we know for sure.
I'd still be interested in reproducing and investigating it.

I also don't think this is a bug on Nvidia's end. I was able to test this on a laptop with Intel graphics and some connected monitors. The only common thing between my PC and this laptop is Firefox and Windows versions.

(In reply to obacz.krzysztof from comment #38)

I also don't think this is a bug on Nvidia's end. I was able to test this on a laptop with Intel graphics and some connected monitors. The only common thing between my PC and this laptop is Firefox and Windows versions.

Just to clarify: you reproduced the bug on an Intel GPU?
Note: many laptops have two GPU's: an integrated Intel GPU and a discrete Nvidia GPU.
Are you sure you don't have a discrete Nvidia GPU on the laptop?

The laptop where I've replicated this issue has only Intel UHD 620. No Nvidia nor AMD at all.

(In reply to obacz.krzysztof from comment #40)

The laptop where I've replicated this issue has only Intel UHD 620. No Nvidia nor AMD at all.

obacz.krzysztof: Thanks for confirming.

everyone: That means it seems unlikely that this is a Nvidia bug, but rather a Microsoft bug. If any evidence to the contrary comes up, please feel free to send me email about this issue again.

@aleino I appreciate the help and effort. I don't know if you are in contact with Microsoft already, but forwarding this to them from Nvidia's end could help them speed things up.

michelfeinstein: No problem!

It's a good idea for both end users and Nvidia to let Microsoft know about this.
So far I've only raised the idea of contacting Microsoft. (Just to ensure we're not already talking to Microsoft about this.)
I'll follow up on that.

Jessie already flagged this for Microsoft and they asked that I opened an issue into their Feedback system, as previous messages here say. I just thought that Microsoft being contacted by multiple industry leaders would speed things up with them.

(In reply to michelfeinstein from comment #20)

Done: https://aka.ms/AA8myqx, please forward this feedback to them.

I agree that Nvidia should be aware of this as well as WDDM 2.7 needs new drivers from their part.

Is that link supposed to take me to some Microsoft issue report?

For me it just leads to a page that says "Opening the feedback hub", and then nothing further happens.
When I click on the button to open the feedback hub manually, it opens and gives me a blank feedback input form.

Yeah, it used to work, now I also get nothing.

Maybe this URI link works: feedback-hub:?contextid=1012&feedbackid=f691dcd0-5928-4909-b6ea-1e3f86a0c983&form=1&src=1

(In reply to michelfeinstein from comment #46)

Yeah, it used to work, now I also get nothing.

Maybe this URI link works: feedback-hub:?contextid=1012&feedbackid=f691dcd0-5928-4909-b6ea-1e3f86a0c983&form=1&src=1

Thanks. I figured out that explorer and Edge can open this type of URI.
It'll take you to a blank feedback hub input form like before, but there is a message bout logging into the feedback hub.
When you log in, it still doesn't take you to the issue.
However, after logging in, you can open the URI again using Edge or explorer, and then when the feedback hub opens I can see your issue report.

I'll share this feedback URI (and procedure for viewing it) with my colleagues so they have a report to point to when contacting Microsoft.

Maybe we should open a feedback regarding the feedback itself :P

Jokes apart, I appreciate the help!

(In reply to Jessie [:jbonisteel] pls NI from comment #18)

Have flagged this for Microsoft.

michelfeinstein, when you get a minute, could you file a bug with Microsoft using their Feedback hub? https://support.microsoft.com/en-ca/help/4021566/windows-10-send-feedback-to-microsoft-with-feedback-hub-app - this is at their request. This helps them track incoming issues.

We can also reach out to Nvidia so they are aware and we can see if there is a workaround.

Hi Jessie. How did you flag it with Microsoft?
Is there a link to some public issue, or did you contact them via email, or something else?

(In reply to michelfeinstein from comment #48)

Maybe we should open a feedback regarding the feedback itself :P

Jokes apart, I appreciate the help!

No problem!

It makes things easier for me to be in the loop about graphical issues that are not caused by our driver/cards, so it's a good idea for me to be in contact with Microsoft anyway.

I reached out to one of our contacts at MSFT, last week they told us:

" we have fixed it in a future release, and we are now looking at porting that fix back to 2004. No promises, but the ball is rolling."

Not sure when that future release might happen or whether it will apply to 2004 but it looks like they have tried to address it. I will keep folks posted if I hear more about timing

(In reply to Jessie [:jbonisteel] pls NI from comment #51)

I reached out to one of our contacts at MSFT, last week they told us:

" we have fixed it in a future release, and we are now looking at porting that fix back to 2004. No promises, but the ball is rolling."

Not sure when that future release might happen or whether it will apply to 2004 but it looks like they have tried to address it. I will keep folks posted if I hear more about timing

Sounds good. Let me know if I can help out more. I'll leave myself CC'd on the bug.

I used Windows 10 Game Bar Capture to record Firefox and the final recording had a green bar on the bottom, this doesn't happen on other programs, so I think it might be related to this issue.

(In reply to aleino from comment #47)

(In reply to michelfeinstein from comment #46)

Yeah, it used to work, now I also get nothing.

Maybe this URI link works: feedback-hub:?contextid=1012&feedbackid=f691dcd0-5928-4909-b6ea-1e3f86a0c983&form=1&src=1

Thanks. I figured out that explorer and Edge can open this type of URI.
It'll take you to a blank feedback hub input form like before, but there is a message bout logging into the feedback hub.
When you log in, it still doesn't take you to the issue.
However, after logging in, you can open the URI again using Edge or explorer, and then when the feedback hub opens I can see your issue report.

I'll share this feedback URI (and procedure for viewing it) with my colleagues so they have a report to point to when contacting Microsoft.

Did they remove it? I can't access it. Get "Your account doesn't have access to this feedback".
Wanted to add "me too" comment. Is it on Miscrosoft radar finally?

Since upgrade to Win 2004 seeing this issue on Chrome, Brave and Firefox.

(In reply to voldemarz from comment #54)

(In reply to aleino from comment #47)

(In reply to michelfeinstein from comment #46)

Yeah, it used to work, now I also get nothing.

Maybe this URI link works: feedback-hub:?contextid=1012&feedbackid=f691dcd0-5928-4909-b6ea-1e3f86a0c983&form=1&src=1

Thanks. I figured out that explorer and Edge can open this type of URI.
It'll take you to a blank feedback hub input form like before, but there is a message bout logging into the feedback hub.
When you log in, it still doesn't take you to the issue.
However, after logging in, you can open the URI again using Edge or explorer, and then when the feedback hub opens I can see your issue report.

I'll share this feedback URI (and procedure for viewing it) with my colleagues so they have a report to point to when contacting Microsoft.

Did they remove it? I can't access it. Get "Your account doesn't have access to this feedback".
Wanted to add "me too" comment. Is it on Miscrosoft radar finally?

Since upgrade to Win 2004 seeing this issue on Chrome, Brave and Firefox.

I can still see it. Here is what I have to do:

1. first I paste "feedback-hub:?contextid=1012&feedbackid=f691dcd0-5928-4909-b6ea-1e3f86a0c983&form=1&src=1" into the "address bar" of the regular file explorer in Windows.
2. That takes me to some page that has a link I can click to login, but I can't see the bug.
3. I click on that link, which takes me to some other page where I also can't see the bug.
4. I close the file explorer and do step 1 again, which takes me straight to the bug.

Hope that helps.

This link might take you straight to the MS issue: https://aka.ms/AA8myqx

I can still see it. Here is what I have to do:

1. first I paste "feedback-hub:?contextid=1012&feedbackid=f691dcd0-5928-4909-b6ea-1e3f86a0c983&form=1&src=1" into the "address bar" of the regular file explorer in Windows.
2. That takes me to some page that has a link I can click to login, but I can't see the bug.
3. I click on that link, which takes me to some other page where I also can't see the bug.
4. I close the file explorer and do step 1 again, which takes me straight to the bug.

Hope that helps.

Doesn't work for me. I know hot to open FB hub from links, have tried when sharing my own feedback around. Can you shar the title of the ticket? Will try to find it that way.

(In reply to voldemarz from comment #57)

I can still see it. Here is what I have to do:

1. first I paste "feedback-hub:?contextid=1012&feedbackid=f691dcd0-5928-4909-b6ea-1e3f86a0c983&form=1&src=1" into the "address bar" of the regular file explorer in Windows.
2. That takes me to some page that has a link I can click to login, but I can't see the bug.
3. I click on that link, which takes me to some other page where I also can't see the bug.
4. I close the file explorer and do step 1 again, which takes me straight to the bug.

Hope that helps.

Doesn't work for me. I know hot to open FB hub from links, have tried when sharing my own feedback around. Can you shar the title of the ticket? Will try to find it that way.

The title is "May 2020 Update Bug with Stacked Multi-Monitors: White bar on the bottom of top monitor for windows with no title like Firefox".

Hmm. Can't find it even by title. Odd. I guess wil have to ask MS about that.

@ale(In reply to aleino from comment #58)
Are you using an insider build?

I contacted Microsoft and they said that feedback item is about insider build. I supposed that is why I can't access it (MS agent wasn't sure). I am MS insider though, just use regular build.

@michelfeinstein Did you submit the MS Feedback from insider build?

No, I am not an insider and avoid beta builds as much as possible.

(In reply to michelfeinstein from comment #61)

No, I am not an insider and avoid beta builds as much as possible.

Oh.. Apparently another bug in Windows. Colour me surprised.
Can you drop online in imgur etc a screenshot of how that feedback looks?

MS support ended up being useless and suggested to create post anwers.microsoft.com as apparently "specialists there have deeper knowledge". Want add that sceenshot in there.

Sorry for commenting on this after so long. I'm just wondering if there's been any updates to this situation as I just updated to windows 2004 and am having this particular issue.

It happens with windows 2004 and 20h2, Firefox is currently 88.0.1. The issue only seems to occur on the top monitor in a vertical layout when the titlebar is hidden and the program is in fullscreen.

(In reply to Coolishy from comment #63)

Sorry for commenting on this after so long. I'm just wondering if there's been any updates to this situation as I just updated to windows 2004 and am having this particular issue.

It happens with windows 2004 and 20h2, Firefox is currently 88.0.1. The issue only seems to occur on the top monitor in a vertical layout when the titlebar is hidden and the program is in fullscreen.

The last information on this as far as I know is in comment 51.
If you find anything contrary to that, get in contact with Microsoft, perhaps via Jessie who wrote comment 51.

(In reply to Coolishy from comment #63)

Sorry for commenting on this after so long. I'm just wondering if there's been any updates to this situation as I just updated to windows 2004 and am having this particular issue.

It happens with windows 2004 and 20h2, Firefox is currently 88.0.1. The issue only seems to occur on the top monitor in a vertical layout when the titlebar is hidden and the program is in fullscreen.

It's happening to me too, Windows 10 Pro 21H1 and firefox 89.0.2.
Laptop under monitor and the white bar only appears at the bottom of the monitor, when firefox is in fullscreen.

Can reproduce with 89.0.2 and 21H1. Not just limited to 2004.

Hey, I was following this thread for a while because we only use Firefox at work and I have my monitors stacked vertically at home.
I was recently upgrading my private client to Windows 11 and it seems that the Bug is not longer occuring on Windows 11.
Hopefully this also works for everyone else.

I can confirm that this bug is still happening with Windows 10 20H2 & Firefox 96.0.2 (64-Bit).

As https://bugzilla.mozilla.org/show_bug.cgi?id=1643260#c67 says this issue is fixed in Windows 11. Would there be a possibility that Microsoft will port the fix back to a coming Windows 10 version? Anyone still in touch with Microsoft regarding this bug?

(In reply to konradwilhelm93 from comment #68)

I can confirm that this bug is still happening with Windows 10 20H2 & Firefox 96.0.2 (64-Bit).

As https://bugzilla.mozilla.org/show_bug.cgi?id=1643260#c67 says this issue is fixed in Windows 11. Would there be a possibility that Microsoft will port the fix back to a coming Windows 10 version? Anyone still in touch with Microsoft regarding this bug?

I meant Windows 10 version 21H1 (build 19043.1466)

I need to correct my statement.
The error just seemed to be gone in Windows 11. If I just start Firefox, there is no bar visible on my upper screen. As soon as I use fullscreen (e.g. watch a YouTube video), and return to normal mode, the bar on my upper screen becomes visible again until I restart Firefox.
As I don't use fullscreen too often, it doesn't really bother me, but its still not fixed.

I was having this issue too and found that the issue went away after applying a userChrome.css fix I found off the firefox subreddit. I'm on Firefox 97.0b9 and Windows 10 21H2.

(In reply to j_shum55 from comment #71)

I was having this issue too and found that the issue went away after applying a userChrome.css fix I found off the firefox subreddit. I'm on Firefox 97.0b9 and Windows 10 21H2.

For the sake of documenting it here, the fix proposed by the user panoptigram is to Add the following to the userChrome.css:

:root[tabsintitlebar][sizemode="maximized"] {
appearance: -moz-win-glass;
}

unfortunately, this didn't work for me. I'm running an AMD GPU, Win10 21H2 and Firefox Nightly v99.

@EekaDroid
As this was also my first time using the userChrome.css and I have no further experience with it, I found out that it was only working for me if I remove the first line I got from the manual:
@namespace url("http://mozilla.org/keymaster/gatekeeper/there.is.only.xul");

Beware that I have no clue if it has any other side effects to remove this line. Until now, I haven't found any issues.
Maybe this also works for you.

(In reply to simon.baeuerle27 from comment #73)

@EekaDroid
As this was also my first time using the userChrome.css and I have no further experience with it, I found out that it was only working for me if I remove the first line I got from the manual:
@namespace url("http://mozilla.org/keymaster/gatekeeper/there.is.only.xul");

Beware that I have no clue if it has any other side effects to remove this line. Until now, I haven't found any issues.
Maybe this also works for you.

Thanks for the tip Simon, it works now!

I was using some tweaks to adjust the sidebar as well, they doesn't seem to be affected by removing that first line