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[DOM3 Events] Can a hidden element be a topmost event target?

From: Y. Nobuoka <nobuoka@r-definition.com>
Date: Sat, 15 Oct 2011 17:59:06 +0900
Message-ID: <CAHm8JXWtO0BD0eBzCp7SoD1QXwbYWMDD4ZWVCnCgeSK8yfZarQ@mail.gmail.com>
To: www-dom@w3.org
Hello,

I'm a web developer, and I read W3C DOM Specifications.
As I felt that the explanation of the topmost event target (in DOM3 Events) was
difficult to understand, I'd like to discuss it. Or please tell me the
meaning of
the explanation if my understanding is not good.

DOM3 Events Specification says (about topmost event target):
     Note that visibility of the element does not necessarily affect
its ability to
     be the topmost event target, since an element which is hidden by use of
     the CSS 'visibility' property can still receive pointer events
(though not one
     with a 'display' property of none), and the topmost event target may be
     completely obscured by another element which cannot receive pointer events.
( http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html#glossary-topmost-event-target
)

I see "an element which is hidden by use of the CSS 'visibility' property can
still receive pointer events" by using a following HTML code snippet:
 <div style="visibility: hidden;" onclick="alert( 'hidden elem' )">
   <div style="visibility: visible;" onclick="alert( 'clicked elem'
)">click here</div>
 </div>
When I clicked the text, "click here", the text of "clicked elem" was
alerted first,
and next, the text of "hidden elem" was alerted. So I agreed that the element
which is "visibility: hidden" can receive pointer events.
(I used Firefox 7)

However, I can't understand the description of "visibility of the
element does not
necessarily affect its ability to be the topmost event target".
Does it mean
- a hidden element ("visibility: hidden") is clickable? or
- a hidden element can't be clicked but can be the topmost event target?
If the latter is right, what is the case?

Thanks,
-- 
NOBUOKA Yu
Received on Saturday, 15 October 2011 09:38:45 GMT

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