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".
Looks like hyatt tried to rename to -webkit-overlay in 2006: http://trac.webkit.org/changeset/14968 . We should histogram and try again.
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
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.
> 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.
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.
(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/ .
I wonder if we can try to make it -webkit again, or remove it.
There's talk of standardizing some variation of this:
CSSWG standardized this behavior by add a scrollbar-gutter property:
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.