2061066 - Embeded YouTube video on Google search has gray sidebar in fullscreen

Status: NEW

(Web Compatibility :: Site Reports, defect, P2)

Description

[Jeff Muizelaar [:jrmuizel]]

Attachment: Screenshot 2026-08-05 at 10.52.45 PM.png

STR:

• Load https://www.google.com/search?client=firefox-b-d&hs=3QOq&sca_esv=f7245e0a63eedf28&sxsrf=APpeQnseE7Hs5qiMBNTtAU1nXrzPrErEsQ:1785984482182&udm=7&fbs=ABfTbFVyMZGZf1hfvX9uKjN_-G8cqCQj_06QnZs315LoFmPf5bBLHMJ0vMQmTbuI72DM7jnxvATrUU2Yg9dwuUGnsUHcXPuOM0_k1dPPnMiKJgy16dZbzxEzLfw8wuRMswCXrs8RnrM5_piPyuLg1-_LQAE92ad1fZ-qK1FCpvbuQCj2oVGAmluL385MBmH-GXGJSIp0KmSpSJ5ZouKtlsdTwkrdl0Legg&q=The+Royal+Tenenbaums&sa=X&ved=2ahUKEwiwmonV_oqWAxW7oisGHTstDsIQtKgLegQIHBAB&biw=1718&bih=894&dpr=2&sei=ivZzatWgGNDjmLQPiq-ZWA#fpstate=ive&vld=cid:044a8a63,vid:caMgokYWboU,st:0
• Enter fullscreen

Comment 1

[Emilio Cobos Álvarez [:emilio]]

Jeff confirmed that "Always Show Scrollbars" off "fixes" it.

Comment 2

[Emilio Cobos Álvarez [:emilio]]

Attachment: Reduced test-case.

Comment 3

[Jeff Muizelaar [:jrmuizel]]

Safari has the same behaviour as Chrome on the reduced test case

Comment 4

[Emilio Cobos Álvarez [:emilio]]

Attachment: Fixed-pos with scrollbar-gutter: stable.

Comment 5

[Emilio Cobos Álvarez [:emilio]]

Attachment: Fixed-pos with scrollbar-gutter: stable + fullscreen

Comment 6

[Emilio Cobos Álvarez [:emilio]]

Attachment: test-case that more clearly illustrates the behavior

So Chrome's video is also the wrong size, but they paint black instead of white. Looking a bit more into it, I think this test-case shows the root cause of the disagreement:

• Chrome: backdrop covering the scrollbar gutter, iframe constrained by the gutter.
• Safari: backdrop covering the scrollbar gutter, iframe also covering the gutter.
• Gecko: backdrop and iframe both constrained by the gutter.

So it seems like Chrome's backdrop (but not the fixed-pos) is covering the scrollbar gutter... I'm not sure what really justifies that behavior spec-wise... Ting-Yu, do you know?

If not, it might be worth filing an issue. At least for a fullscreen <iframe> constraining it to the scrollbar gutter seems a bit unfortunate...

Comment 7

[Emilio Cobos Álvarez [:emilio]]

Oh, actually safari has the backdrop not covering the gutter, but the iframe covering it.

Comment 8

[Ting-Yu Lin [:TYLin] (PST, UTC-7)]

This is a variant of bug 1874091. Previous solution is:

RESOLVED: (top layer or fullscreen) elements with 'position: fixed' cover the scrollbars/gutters

But the spec didn't say what to do for top layer (::backdrop) elements without position:fixed.

Also, Chromium has a bug https://issues.chromium.org/issues/346550123

Comment 9

[Emilio Cobos Álvarez [:emilio]]

But ::backdrop is fixed right? https://searchfox.org/firefox-main/rev/ee8e457ae20efb27313476fed0bed50571c1199f/layout/style/res/ua.css#409

So I think this is effectively bug 1874091 indeed.

Comment 10

[Emilio Cobos Álvarez [:emilio]]

(And all browsers are broken in different ways, amazingly)

Comment 11

[Ting-Yu Lin [:TYLin] (PST, UTC-7)]

But ::backdrop is fixed right? https://searchfox.org/firefox-main/rev/ee8e457ae20efb27313476fed0bed50571c1199f/layout/style/res/ua.css#409

You're right. I must have mixed it with something else ...

Comment 12

[Daniel Holbert [:dholbert]]

(In reply to Emilio Cobos Álvarez [:emilio] from comment #9)

So I think this is effectively bug 1874091 indeed.

Let's consider this diagnosed as that platform-bug then. --> Adjusting keywords.