Bug 32388 – Remove or rename overlay overflow values

• Component: CSS
• Status: RESOLVED WONTFIX

[Erik Arvidsson]

WebKit currently has a proprietary CSS overflow value called "overlay" which is undocumented and as far as I can tell from reading the code works exactly like "auto".

We should either remove it or rename it to "-webkit-overlay".

[Tony Chang]

Looks like hyatt tried to rename to -webkit-overlay in 2006: http://trac.webkit.org/changeset/14968 .  We should histogram and try again.

[Tony Chang]

10:05 < tony^work> dhyatt: What was overflow: overlay?
10:06 < tony^work> dhyatt: It looks like it's the same as overflow: auto now.
10:06 < dhyatt> a way for scrollbars to overlay the content instead of taking 
                up space
10:06 < dhyatt> now all scrollbars on OS X overlay content
10:06 < dhyatt> so on OS X at least it's not that relevant
10:06 < dhyatt> still applies to say Windows though

Looks like it used in a few places on the web (also in the WebKit Web Inspector).  Ojan says we should probably to try standardize it.

[Julien Chaffraix]

> Looks like it used in a few places on the web (also in the WebKit Web Inspector).  Ojan says we should probably to try standardize it.

I am pretty sure I asked about removing it at some point last year, the answer was that it was used internally by Apple (I can't recall the exact wording and lost my logs of this conversation). It may also make sense for mobile as overflow: overlay scrollbars don't trigger a layout.

[Tab Atkins]

Okay, so it's identical to "auto" in behavior, but just forces the scrollbars (if created) to be overlay rather than space-filling?

This sounds like an okay kind of thing to standardize, and I can try to do so if my above description is correct.

[Tony Chang]

(In reply to comment #4)
> Okay, so it's identical to "auto" in behavior, but just forces the scrollbars (if created) to be overlay rather than space-filling?

Yes, that's right.  Here's an example: http://jsfiddle.net/rNxgD/ .

[Simon Fraser (smfr)]

I wonder if we can try to make it -webkit again, or remove it.

[Chris Rebert]

There's talk of standardizing some variation of this:
https://github.com/w3c/csswg-drafts/issues/92

[Fuqiao Xue]

CSSWG standardized this behavior by add a scrollbar-gutter property:

* https://drafts.csswg.org/css-overflow-4/#scollbar-gutter-property
* https://github.com/w3c/csswg-drafts/issues/92#issuecomment-272567887

[Simon Fraser (smfr)]

I'm making 'overlay' a synonym for 'auto': bug 189811. I'd prefer to remove it, but that causes sites that use it to fall back to overflow:auto, which would be a breaking behavior change.

[Brent Fulgham]

We can revisit removing 'overlay' entirely once the web has moved on.