Note: There are a few cases of duplicates in user autocompletion which are being worked on.

Black bar on top of FireFox on 4k screen, width issue




Graphics: Layers
2 years ago
a year ago


(Reporter: Kjetil, Unassigned, NeedInfo)



41 Branch
Mac OS X

Firefox Tracking Flags

(Not tracked)


(Whiteboard: [gfx-noted])


(7 attachments)



2 years ago
Created attachment 8659801 [details]
Skjermbilde 2015-09-11 kl. 11.22.29.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.85 Safari/537.36

Steps to reproduce:

Use Firefox on a external 4k monitor, make the reader the full width of the screen. If you make the browser smaller, like 2/3 of the complete width, the black bar dissapears, and you instead see it to the right (see screenshot). There is clearly some bad coding with the scaling here that makes this problem occur. It seems the browser only scales the top bar with URL etc to a certain width, then it stops and a black line is added instead.

Actual results:

Black bar at the top of the reader that covers the tabs

Expected results:

No black bar


2 years ago
Component: Untriaged → Widget: Cocoa
OS: Unspecified → Mac OS X
Product: Firefox → Core

Comment 1

2 years ago
For clarification, the black line that causes the issue is the thin black line on the top, not the thicker black line below, that has something with the graphic on the web page I'm on to do.

Comment 2

2 years ago
Have you tried if you see this issue in a new profile, too? You can find details on how to create a new profile (without changing anything in your regular profile!) at .

Have you tried if you see this issue in Firefox's safe mode, too? You can restart Firefox into safe mode by using the 'Restart Firefox with add-ons disabled' entry in the 'Help' menu. This will also disable graphics hardware acceleration and some JS engine optimizations, not just extensions and plugins. See .
Flags: needinfo?(kjetil.kiran)
Keywords: in-triage

Comment 3

2 years ago
Created attachment 8659836 [details]
Safe Mode

This is a screenshot from Safe Mode. As you can see the issue still occurs, but instead of getting the line on top, it is on the right side in Safe Mode.
Flags: needinfo?(kjetil.kiran)

Comment 4

2 years ago
When I make a new profile, the problem seems to dissapear, and the browser scales normal.

Comment 5

2 years ago
(In reply to Kjetil from comment #4)
> When I make a new profile, the problem seems to dissapear, and the browser
> scales normal.

Can you post the contents of about:support here, from the broken profile?
Flags: needinfo?(kjetil.kiran)

Comment 6

2 years ago

Navn: Firefox
Versjon: 41.0b8
Bygg-ID: 20150907144446
Oppdateringskanal: beta
Brukeragent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:41.0) Gecko/20100101 Firefox/41.0
Multiprosess-vinduer: 0/1 (standard: false)

Krasjrapporter de siste 3 dagene

Alle krasjrapporter


Navn: LastPass
Versjon: 3.2.16
Påslått: true


Asynkron pan/zoom: ingen
Enhet-ID: 0x162b
GPU-akselererte vinduer: 0/1 Basic (OMTC)
Leverandør-ID: 0x8086
Støtter maskinvare H264-dekoding: false
WebGL-renderer: Intel -- Intel(R) Iris(TM) Graphics 6100
windowLayerManagerRemote: true
AzureCanvasBackend: skia
AzureContentBackend: quartz
AzureFallbackCanvasBackend: none
AzureSkiaAccelerated: 0

Viktige endrede innstillinger

accessibility.typeaheadfind.flashBar: 0
browser.cache.disk.capacity: 358400
browser.cache.disk.filesystem_reported: 1
browser.cache.disk.hashstats_reported: 1
browser.cache.disk.smart_size.first_run: false
browser.cache.disk.smart_size.use_old_max: false
browser.cache.frecency_experiment: 1 true false
browser.places.smartBookmarksVersion: 7
browser.sessionstore.upgradeBackup.latestBuildID: 20150907144446
browser.startup.homepage_override.buildID: 20150907144446
browser.startup.homepage_override.mstone: 41.0
dom.apps.reset-permissions: true
dom.mozApps.used: true
extensions.lastAppVersion: 41.0
font.internaluseonly.changed: true
gfx.blacklist.direct2d: 3
layers.acceleration.disabled: true
media.gmp-gmpopenh264.lastUpdate: 1431331106
media.gmp-gmpopenh264.version: 1.4
media.gmp-manager.buildID: 20150907144446
media.gmp-manager.lastCheck: 1441969530
network.cookie.prefsMigrated: true
network.predictor.cleaned-up: true
places.database.lastMaintenance: 1441364613
places.history.expiration.transient_current_max_pages: 104858
plugin.disable_full_page_plugin_for_types: application/pdf
plugin.importedState: true
privacy.sanitize.migrateFx3Prefs: true
security.disable_button.openCertManager: false
storage.vacuum.last.index: 1
storage.vacuum.last.places.sqlite: 1441266102

Viktige låste innstillinger


Inkrementell GC: true


Aktivert: false
Forhindre tilgjengelighet: 0


Forventet minimumsversjon: 4.10.8
Versjon i bruk: 4.10.8

Forventet minimumsversjon: 3.19.2 Basic ECC
Versjon i bruk: 3.19.2 Basic ECC

Forventet minimumsversjon: 3.19.2 Basic ECC
Versjon i bruk: 3.19.2 Basic ECC

Forventet minimumsversjon: 3.19.2 Basic ECC
Versjon i bruk: 3.19.2 Basic ECC

Forventet minimumsversjon: 3.19.2
Versjon i bruk: 3.19.2

Eksperimentelle funksjoner
Flags: needinfo?(kjetil.kiran)

Comment 7

2 years ago
Looks like the broken profile has layers.acceleration.disabled set to true, disabling hardware acceleration. You can toggle this in the preferences. I presume doing so fixes the issue?
Component: Widget: Cocoa → Graphics: Layers
Flags: needinfo?(kjetil.kiran)

Comment 8

2 years ago
Created attachment 8659845 [details]
Skjermbilde 2015-09-11 kl. 13.43.23.png

This screenshot shows how it looks like when I open Firefox with a to "big" width.
Flags: needinfo?(kjetil.kiran)

Comment 9

2 years ago
Created attachment 8659846 [details]
Skjermbilde 2015-09-11 kl. 13.43.30.png

This is when I make it smaller, as you can see the black line dissapears.

Comment 10

2 years ago
Created attachment 8659848 [details]
Skjermbilde 2015-09-11 kl. 13.43.41.png

When I Make it bigger again after having made it smaller, it works as it should

Comment 11

2 years ago
All these screenshots are after activating hardware acceleration.

Comment 12

2 years ago
(In reply to Kjetil from comment #11)
> All these screenshots are after activating hardware acceleration.

OK. I assume this is after restarting Firefox (after enabling hardware acceleration) ?

And to be clear, you said in comment #4 that the new profile worked, by which I presume that the clean profile doesn't have those initial artifacts?

Milan, do you have ideas about what's going on here?
Flags: needinfo?(milan)
Flags: needinfo?(kjetil.kiran)

Comment 13

2 years ago
The new profile has the same issue. I just didn't open it with a big width when I check the first time. So the bug does not seem to have anything with my profile to do.
Flags: needinfo?(kjetil.kiran)

Comment 14

2 years ago
On my iMac 5k this is not an issues, so it has something to do with using an external 4k screen on a MBP, it seems like.
Whiteboard: [gfx-noted]

Comment 15

2 years ago
I am also experiencing this issue on my mid 2015 MBP connected to a Dell 4K P2715Q on OS X 10.11.1. I am seeing this behavior in 42, 43.0.1, and on my inbound build (@277023).  There is also some odd scaling happening to the chrome when full screen, that may be a separate bug.

Comment 16

2 years ago
Created attachment 8700350 [details]
Screen Shot 2015-12-19 at 3.07.57 PM.png

Comment 17

2 years ago
Exactly the same as me, but I think they just gave up fixing it ... I would think this would be SUPER easy to fix, and the problem will only grow when people start using 4K screens.
Nico or Kjetil, could you please check to see how far back this issue goes? To do this you'll need to try progressively older releases until the issue stops reproducing, starting with Firefox 42. You can find our release installers at

If this is a regression then I'll need you to use to narrow it down further, but first try to find the release version so we can use that as a starting point.

If this isn't a regression then that's a whole other ball of wax.

Comment 19

2 years ago
I have never had a FF where it has not been an issue. One of you guys probably has a Macbook and a 4K screen so you can reproduce this yourself?
(In reply to Kjetil from comment #19)
> I have never had a FF where it has not been an issue. One of you guys
> probably has a Macbook and a 4K screen so you can reproduce this yourself?

I do not personally but I'm asking around. Even if we do track one down there is no guarantee that we'll be able to reproduce the issue. I'll continue to work on this but it would be great if you could help us in parallel. The fact that you can reproduce this issue means you're several steps ahead of us.

Comment 21

2 years ago
Not hard to reproduce when all you need is a Macbook, 4K screen and any version of FireFox. Seems like this always happens for everyone, just not that many that uses a macbook and FF with a 4K screen yet.
I can't reproduce this on my MacBook Pro (Retina, 15-inch, Late 2013) on 10.11.1 using an external 4k monitor (U28D590D).

My guess: Only happens with macbooks that don't have discrete GPU. The Iris GPU must have a smaller max texture.

Can you post the GL Info for Iris driver?

Spotlight -> OpenGL Driver Monitor -> (top menu) Monitors -> Renderer Info -> Save as Text. In bugzilla 'Add as an attachment' -> paste text as an attachment.

Comment 23

2 years ago
I dont have anything called that on my computer.

From system information:

Intel Iris Graphics 6100:

  Brikkesettmodell:	Intel Iris Graphics 6100
  Type:	GPU
  Buss:	Innebygd
  VRAM (dynamisk, maks):	1536 MB
  Leverandør:	Intel (0x8086)
  Enhets-ID:	0x162b
  Revisjons-ID:	0x0009
  Skjermtype:	Retina-LCD
  Oppløsning:	2560 x 1600 Retina
  Retina:	Ja
  Pikseldybde:	32-bits farge (ARGB8888)
  Hovedskjerm:	Ja
  Like skjermer:	Av
  Tilkoblet:	Ja
  Innebygd:	Ja

Comment 24

2 years ago
Created attachment 8700708 [details]

For future reference BenWa, OpenGL Driver Monitor is no longer included with Xcode, you have to download the "Graphics Tools for Xcode" from the Apple Developer website.
So the max texture is large enough, but the intel mac drivers have lied to us in the past about their max texture so I'm not sure.

I tried using the following with their Iris adapter:
macbook pro 13inch late2013 11,1 (using hdmi)
macbook air 6,2

Neither could reproduce the bug.

Comment 26

2 years ago
Connected to an external 4k monitor?
Yes, U28D590D @ 3840 x 2160

Comment 28

2 years ago
Hmm, im using displayport, not sure if that might mean something.

I'm using displayport as well when possible. Can you try to remove the content scaling on your external monitor (run it as 'more space')? This could be an issue if it's not a driver bug and just a firefox bug. But running here at 2x on my 4k doesn't reproduce.

Comment 30

2 years ago
I dont have the screen available before January, so not able to try it.
Only other difference is that im on Macbook 2015.

Comment 31

2 years ago
When turning off scaling, it does not happen to new windows, and already effected windows no longer display the black bar. I am also connected via DP.
Flags: needinfo?(milan)

Comment 32

a year ago
I also see this.  Macbook Pro 15" Mid 2014 model GeForce 750M, when connected to various 4k external displays (at least three different models), all over DP.

When scaling is turned off this isn't a problem.
When scaling is turned on and you create a new window at above a certain size (about 3/4 of the screen) you get the black bar. Resizing the window down to below that size removes the black bar. Resizing a window back up again doesn't get you the black bar back. So appears to only be new windows above a certain size.
Hmm, this could be caused by us failing to allocate the title bar texture in nsChildView if it exceeds the maximum texture size. The rest of the browser starts using tiled layers if necessary, but the title bar texture does not.

Comment 34

a year ago
(In reply to Markus Stange [:mstange] from comment #33)
> Hmm, this could be caused by us failing to allocate the title bar texture in
> nsChildView if it exceeds the maximum texture size. The rest of the browser
> starts using tiled layers if necessary, but the title bar texture does not.

Is there anything people seeing this can do to verify this potential diagnosis? Would enabling the titlebar (ie disabling tabs-in-titlebar) from customize mode work around this issue, for instance? It seems we (ie folks at Mozilla) have had trouble reproducing, and at least if we can verify this diagnosis that might get us closer to being able to fix it...
Flags: needinfo?(mstange)

Comment 35

a year ago
Have just tried this.  

browser.tabs.drawInTitlebar;false fixes the issue! No need to restart firefox, switch it back to true and the black bar is there again.

Incidentally I tried reproducing this on a colleagues 15" Pro but with only intergrated graphics (Iris Pro) and that doesn't have the black bar issue.

I've got access to another 15" Pro but with the AMD graphics card and will check it on there when I have a sec.
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