Re: [css-overflow] A question about overflow-x and overflow-y

Thanks Florian.

Any one of overflow-x and overflow-y being `hidden` will trigger BFC, which
don't have to break anything of spec. "BFC in one dimension" doesn't have
to exist here. So I don't think it's something prevents `visible` +
`hidden`.

As you said, scrollbars actually don't break `visible` + `hidden` either
(in this combination, we don't need scrollbars).

So I assume it's more of a history and compatibility issue?


On Tue, May 31, 2016 at 9:10 AM, Florian Rivoal <florian@rivoal.net> wrote:

>
> > On May 30, 2016, at 18:24, Justice <justice360@gmail.com> wrote:
> >
> > Hi,
> >
> > According the spec, for the same element, the computed values of these
> two props cannot be visible+hidden at the same time. Does anybody know why
> it is designed this way? Or it's just because of compatibilities?
>
> Besides history and compatibility requirements, I think the two main
> reasons are:
>
> * overflow: hidden does more than just hide the overflow, it also makes
> turns the element into a Block Formatting Context (Floats don't escape,
> margins of children don't collapse with margins of parents...). Being a BFC
> in one dimension only is not a thing that exists.
>
> * if an element could be overflow-x: visible and overflow-y: scroll, you
> would have a vertical scrollbar on the right (typically) side of the
> element, overlapping with the visibly overflowing content in the inline
> direction, which is terrible. Same for visible + auto. This isn't
> necessarily a problem for visible+hidden, but at least it explains why the
> other values cannot be combined with visible.
>
>  - Florian