[csswg-drafts] [css-overflow][css21] overflow:hidden SHOULD or MUST not be scrollable?

frivoal has just created a new issue for 
https://github.com/w3c/csswg-drafts:

== [css-overflow][css21] overflow:hidden SHOULD or MUST not be 
scrollable? ==
Via language that was carried over from css2, `overflow: hidden` is 
[specified in css-overflow 
as](https://drafts.csswg.org/css-overflow/#valdef-overflow-hidden) 
(emphasis mine):
>This value indicates that the content is clipped and that no 
scrolling user interface **should** be provided by the UA to view the 
content outside the clipping region. However, the content may still be
 scrolled programatically, for example using the mechanisms defined in
 [CSSOM-VIEW]. 

I do not believe that this **should** is intentional, so we ought to 
replace it with **must**. `overflow: hidden` isn't meant to be 
scrollable except via script. Or is it?

I'm asking because iOS has a bug where it is scrollable in some corner
 cases. But if we have **should** rather than **must**, then maybe it 
is not a bug.

References:
* [demo of the 
bug](https://bug-153852-attachments.webkit.org/attachment.cgi?id=270644)
* [webkit bug](https://bugs.webkit.org/show_bug.cgi?id=153852)
* [proposed test case](https://github.com/w3c/csswg-test/pull/1079)

Please view or discuss this issue at 
https://github.com/w3c/csswg-drafts/issues/666 using your GitHub 
account

Received on Monday, 31 October 2016 01:49:37 UTC