- From: Boris Zbarsky <bzbarsky@mit.edu>
- Date: Thu, 12 Mar 2015 23:06:43 -0400
- To: Nat Duca <nduca@chromium.org>
- CC: "public-web-perf@w3.org" <public-web-perf@w3.org>
On 3/12/15 10:29 PM, Nat Duca wrote: > We can know in some extreme cases: minimizing, for instance. And even then, maybe not: there are Linux windowmanagers that don't necessarily notify the app when minimizing, and there are others that so notify but keep showing it... > The page visibility spec is, I recall, crafted carefully, to allow false > positives for "visible" but not false negatives. Some of the drafts were, but the final REC clearly says (<http://www.w3.org/TR/2013/REC-page-visibility-20131029/> here): On getting, the hidden attribute MUST return true if the Document contained by the top level browsing context (root window in the browser's viewport) [HTML5] is not visible at all. with the following statement afterwards (contradicting the above, yay): To accommodate accessibility tools that are typically full screen but still show a view of the page, when applicable, this attribute MAY return false when the User Agent is not minimized but is fully obscured by other applications. Depending on which of those mutually contradictory normative statements (because MUST was used instead of SHOULD) you decide is more normative, you might be able to do something that makes sense... > But, "page is not visible" means "the page is definitely not visible to > the user." This is the very important one for us to get right. Sadly, the spec doesn't make that all that clear. -Boris
Received on Friday, 13 March 2015 03:07:13 UTC