[Bug 28460] New: Request fullscreen on both iframe and elements inside it could cause undesired result

https://www.w3.org/Bugs/Public/show_bug.cgi?id=28460

            Bug ID: 28460
           Summary: Request fullscreen on both iframe and elements inside
                    it could cause undesired result
           Product: WebAppsWG
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Fullscreen
          Assignee: annevk@annevk.nl
          Reporter: quanxunzhen@gmail.com
        QA Contact: public-webapps-bugzilla@w3.org
                CC: mike@w3.org, public-webapps@w3.org

In the current spec, the "collect ancestors" function returns a list of
documents whose fullscreen element stack consist of one element, and then those
documents exit from fullscreen in the last step of exitFullscreen() method.

I know it is defined this way so that iframes outside automatically exit when
we exit the only fullscreen element in it, just like how they were
automatically pushed to the stack.

But this could cause undesired problem if author explicitly calls
requestFullscreen() on an iframe element, then call the same method on some
element inside.

For example, if we have tree like:

iframe #a
|
+- div #b

and follow the steps:
1. call a.requestFullscreen()
2. call b.requestFullscreen()
3. call a.contentDocument.exitFullscreen()

This will cause the fullscreen be fully exited, because the only element in the
fullscreen element stack of document inside #a is being popped.

This could really surprise author, as they could sometimes want to make iframe
itself fullscreen.


To fix this issue, I propose we change the first step of requestFullscreen()
to: If the context object has nested browsing context, let pending be the
documentElement of the nested document, otherwise, let pending be the context
object.

This could make things a little surprising that calling requestFullscreen() on
an iframe then calling exitFullscreen() on its contentDocument could exit
fullscreen. But I think it should be fine as it doesn't add much complexity
while fixes a more significant undesired behavior.

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Received on Friday, 10 April 2015 05:03:28 UTC