Re: [Page Visibility] Spec Updates

On Fri, May 13, 2011 at 5:42 PM, Kyle Simpson <getify@gmail.com> wrote:

>  Is "hidden" state issued if the window is only partially obscured (that
> is, a "keep on top" type window is partially, whether just a few pixels or a
> whole lot of pixels) on top of the window in question? Or, what if the
> window is still active but is completely obscured by such another window?
>
> Also, what if a window is active and not obscured, but appears partially
> off screen (or entirely off screen)?
>
> What if a browser has some "chrome" element (like a menu, dialog, plugin
> UI, etc) that is displaying partially (or entirely) obscuring the page?
>
> What if a window exists partially or entirely on a second screen, and that
> second screen is turned off? (I realize that's a stretch, but just wanted to
> bring it up for completeness/posterity sake).
>

Those situations are all "visible".


>
> --------------
> In the spirit of this type of functionality, should there be a PAGE_IDLE
> type of state/event?
>

That seems orthogonal.

- James

>
> --Kyle
>
>
>
>
>  *From:* Jatinder Mann <jmann@microsoft.com>
> *Sent:* Friday, May 13, 2011 11:14 PM
> *To:* public-web-perf@w3.org
> *Subject:* RE: [Page Visibility] Spec Updates
>
>  Based on feedback from the mailing list and action items from the last
> conference call, I’ve made the following updates to the Page Visibility
> spec,
> http://dvcs.w3.org/hg/webperf/raw-file/tip/specs/PageVisibility/Overview.html
> :
>
>
>
> -          *Interface exposed on Document instead of Window*
>
> I have updated the Page Visibility properties to be exposed on Document
> instead of Window to reduce (undeclared) global variable collisions.
>
> * *
>
> -          *Feature detection*
>
> Using if (document.visible) for feature detection has the downside that the
> undefined case, which legacy browsers would hit, is equal to the not visible
> case; meaning legacy browsers will get the behavior defined for the hidden
> page. An alternative test is to check whether document.visibilityState
> exists, even if a web developer is only interested in document.visible.
> Instead, a simpler approach may be to define the boolean as document.hidden.
> Doing feature detection on document.hidden will ensure that the undefined
> case is equal to the visible page case; legacy browsers will get the page
> with the visible behavior. I have updated references to document.visible to
> document.hidden. Please review this change.
>
>
>
> I’ve also updated the example section to use feature detection with
> document.hidden. **
>
> * *
>
> -          *PAGE_PRERENDER and PAGE_PREVIEW are optional*
>
> Considering these two states may not always make sense for a user agent,
> they have been defined as optional. E.g., a mobile user agent may not have
> the concept of a preview. **
>
> * *
>
> -          *Removed PAGE_OTHER state*
>
> If a user agent wants to provide an experimental implementation, they can
> do so with a prefixed state. The PAGE_OTHER state doesn’t provide any
> additional benefit. As per agreement on the conference call, I have removed
> this state.
>
> * *
>
> -          *Constants changed to DOMStrings*
>
> Based on feedback, I have changed the constants from unsigned shorts to
> strings.
>
> * *
>
> -          *Fully obscured case.*
>
> Based on feedback on the mailing list, determining whether the page is
> visible when the user agent is fully obscured by another application is
> difficult. Further, most accessibility tools, like magnifier, require to be
> full screen. Returning PAGE_HIDDEN in this case will always give the hidden
> page behavior to accessibility tools. I have added such text to clarify that
> this scenario may be treated as visible:**
>
> “To accommodate accessibility tools that are typically full screen but
> still show a view of the page, when applicable, document.hidden may return
> false when the User Agent is not minimized but is fully obscured by other
> applications.”
>
> Please review these changes and provide additional feedback.
>
>
>
> Thanks,
>
> Jatinder
>
>
>