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Browser window shows black squares and lines, toolbar diappears when resizing

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  • 5 have this problem
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  • Last reply by Basicsman

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Since updating to Firefox 40.0 (in OS X 10.9.5) browser windows and the toolbar show strange black lines and squares when the window is resized. Websites are messed up with black backgrounds or disappear beneath a black layer. The toolbar often disappears too, except for the three Mac resize buttons. It renders Firefox completely unusable.

It’s similar to what is described here: https://support.mozilla.org/nl/questions/1071126 and the bug described here: https://bugzilla.mozilla.org/show_bug.cgi?id=1032769

None of the offered solutions or workarounds seems to help. Disabling all add-ons and extensions doesn’t help either. I only use the Default theme.

Solution To my own surprise the issue disappeared completely when I installed and started to use another theme (Simple White)…

So it seems that Firefox’s Default theme has a serious bug?

Chosen solution

The default theme works on my computer and the bug you referenced was for a Windows machine. Safe Mode would disable hardware acceleration and determine if that was the issue.

OMTC you can try that work around here in about:config to false to determine it it is OMTC, however this should only affect the webpage, not the Firefox interface.

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I've called the big guys to help you. Good luck.

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You can try to disable hardware acceleration in Firefox.

  • Firefox > Preferences > Advanced > General > Browsing: "Use hardware acceleration when available"

You need to close and restart Firefox after toggling this setting.

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

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Hi, thanks for your response, but I already tried troubleshooting as explained in those articles, except for the 'Refresh'.

Hardware acceleration enabled or disabled doesn’t make any difference. I’ve tried disabling all plug-ins and extensions manually, as well as a restart in safe mode. I’ve tried disabling WebGL. As far as I know there are no updates for my graphics display driver. My other browsers (Safari 7.1.8 , Chrome 44), or other apps don’t show problems of this kind. It’s not related to specific websites and it also occurs in blank windows.

If the issue seems to be fixed with the use of another theme, wouldn’t the logical conclusion be that there must be something wrong with the Default theme? Or can a theme get corrupted in the course of time, even when it's updated?

The only thing I haven’t tried is to ‘Refresh’ Firefox (because of the pain of having to reinstall all add ons when I do). Could this help in a case like this?

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These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences

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Chosen Solution

The default theme works on my computer and the bug you referenced was for a Windows machine. Safe Mode would disable hardware acceleration and determine if that was the issue.

OMTC you can try that work around here in about:config to false to determine it it is OMTC, however this should only affect the webpage, not the Firefox interface.

Modified by guigs

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Thanks, guigs - setting OMTC to false worked!

I remember trying it before (after reading this post https://support.mozilla.org/nl/questions/1071126), but (foolishly) must have forgotten to restart then…

This time, after a restart, it works :-)