[whatwg] Proposal for a tab visibility API
glenn at zewt.org
Tue Jan 4 15:50:04 PST 2011
On Tue, Jan 4, 2011 at 6:20 PM, Alex Komoroske <komoroske at chromium.org> wrote:
> A read-only property that returns a string, one of the values described in
> the next section. Developers can use the existence of this property to know
> that they can rely on the rest of this API, too.
> Values returned by all conforming implementations
> * “visible” : the full-size page content is at least partially
> visible on at least one screen.
> * “hidden” : the full-size page content is not visible to the
> user at all.
This leaves very little up to the implementation, which might be
For example, my alt-tab overlay in Windows might be large, and
entirely cover up a browser window. The browser would be required to
treat this as "hidden". That's not necessarily optimal, since it's a
transient state that will go away when the user selects a window. It
may also be difficult to implement correctly. It seems like, although
the window is technically not visible, the decision of whether to
treat this as a hidden or visible state should be left to the
The earlier condition that I think you mentioned seemed reasonable:
never say the page is "hidden" when it's not, eg. no false positives.
It's more harmful to tell a visible page that it's invisible, than to
tell an invisible page that it's visible:
* “visible” : the full-size page content may be at least partially
visible on at least one screen.
* “hidden” : the full-size page content is not visible to the user at all.
This gives implementations some latitude to decide whether a condition
should be treated as hidden, and doesn't require figuring out
precisely whether a window is visible in every case.
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