1425201 - Vimeo videos are not correctly displayed in full screen mode

Status: RESOLVED DUPLICATE of bug 1396732

(Core :: CSS Parsing and Computation, defect)

Description

[roxleitan]

Mozilla/5.0 (X11; Linux x86_64; rv:59.0) Gecko/20100101 Firefox/59.0
Build ID:20171213220121

[Affected versions]:
Nightly 59.0a1, Firefox Beta 58.0b11, Firefox Release 57.0.1

[Affected platforms]:
All platforms: Windows 10, Mac OS X 10.12, Ubuntu 16.04 x64

[Steps to reproduce]:
1.Launch Nightly 59.0a1 with a new profile
2.Open https://vimeo.com/26179832
3.Scroll the page down
4.Click "Enter full screen" button from the video located in the upper left corner

[Expected result]:
The video should be displayed in full screen mode

[Actual result]:
The content located in the upper right corner of the page is displayed in full screen mode

Comment 1

[Ralph Giles (:rillian)]

I see the expected result in Safari and Chrome. It's not a stylo regression either; reproduces on ESR.

I think this is a css issue. If I look at the playing fullscreen <video> element in devtools, it has `z-index: auto` while the `div.outro` which is actually visible has `z-index: 10`. If I set that to `-10` instead the video become visible.

So likely vimeo could work around, but we're doing something different from how we default the z of the video element.

Redirecting to CSS for more analysis.