[whatwg] Proposal for a tab visibility API

[Boris Zbarsky]

On 12/8/10 5:29 PM, Markus Ernst wrote:
> Thus, I'd consider an api for detecting the visibility state of every
> HTML element useful (totally visible, partially visible, hidden - or a
> percentage value).

This is pretty hard to implement, in general.  For example, if I put 
another window over the browser window then whether the content in the 
browser is visible depends on the exact app running in that window, and 
on the parts of it overlapping the browser content, right?

-Boris