Affected versions

• Firefox 70.0a1
• Firefox 69.0b8
• Firefox 68.0.1esr

Affected platforms

• Windows 10 (x64)
• Ubuntu 18.04 (x64)
• macOS 10.14

Steps to reproduce

1. Start Firefox.
2. Access https://www.justareflektor.com/.
3. Click on fullscreen button from the down right corner.
4. Click again on fullscreen button to exit the fullscreen mode.

Expected result

• The browser will return to normal window.

Actual result

• Fullscreen button is not working.

Regression range

• Not sure if this is a regression. It reproduces way back on Firefox 59.0a1 too.

Additional notes

• Please see the attachment for the actual issue.

This seems a bug in the website. Their fullscreen code is doing this.isFullScreen() ? this.cancel() : this.enter(target) or such, but isFullScreen is bogus because it's using the wrong WebIDL name:

>> FullScreenController.getInstance()
<< Object { isPropertyName: "mozfullScreen", requestFunctionName: "mozRequestFullScreen", cancelFunctionName: "mozCancelFullScreen" }

Instead of using mozFullScreen they're using mozfullScreen (note the case difference). So getting the property always returns undefined rather than a boolean.

Also, unprefixed fullscreen API doesn't seem to help, since they also mispell it there (the property is fullscreen, not fullScreen. The case difference is odd, but...

construct:function(){var e=this;document.documentElement.requestFullScreen?(this.isPropertyName="fullScreen",this.requestFunctionName="requestFullScreen",this.cancelFunctionName="cancelFullScreen"):document.documentElement.webkitRequestFullScreen?(this.isPropertyName="webkitIsFullScreen",this.requestFunctionName="webkitRequestFullScreen",this.cancelFunctionName="webkitCancelFullScreen"):document.documentElement.mozRequestFullScreen?(this.isPropertyName="mozfullScreen",this.requestFunctionName="mozRequestFullScreen",this.cancelFunctionName="mozCancelFullScreen"):document.documentElement.mozRequestFullScreen&&(this.requestFunctionName="mozRequestFullScreen",this.cancelFunctionName="mozCancelFullScreen")

Thanks for the analysis -- given that this is a Chrome experiment site made for Arcade Fire's Reflektor album (that came out in 2013), I don't hold out much hope for being able to get anyone to fix this. Usually these things are made by agencies and the half-life on being able to get them fixed is super short.

If someone would like to try, go ahead! Traffic is also very low, the current alexa ranking is #2,494,116.

This is still an issue.

Tested with:
Browser / Version: Firefox Nightly 103.0a1 (2022-06-22)
Operating System: Windows 10 Pro

Tested with:

Browser / Version: Firefox Nightly 111.0a1 (2023-01-16) (64-bit) /Chrome Version 109.0.5414.75 (Official Build) (64-bit)
Operating System: Windows 10 PRO x64

Notes:

1. Reproducible regardless of the status of ETP.
2. Reproducible on the latest build of Firefox Nightly and Release.
3. Works as expected using Chrome.