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Re: Finding elements that are hidden due to overflow: hidden

From: Behrang Saeedzadeh <behrangsa@gmail.com>
Date: Thu, 03 Sep 2015 10:26:16 +0000
Message-ID: <CAERAJ+9DQyom-xWyZDJUebTHY+DHHuvEwegSTrS4Rjhivo4AgQ@mail.gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: W3C CSS Mailing List <www-style@w3.org>, EcmaScript Discuss Mailing List <es-discuss@mozilla.org>
Hi Tab,

My use case can already be implemented using JavaScript and some existing
properties on elements such as clientLeft and its cousins.

Here's a simplified version of my use case:
http://codepen.io/behrangsa/pen/PPozWj

But I thought it would be nicer if an element had a method that could be
used in such cases.

Regarding what to do with partially visible elements, rather than returning
true/false, the method/property -- for example visibleRect -- can return
the dimensions of the visible part of the element (e.g. x: 0, y: 0, w: 20,
h:10) or (0,0,0,0) if it is not visible at all.

I am not sure if this is technically feasible or not. But AFAIK some games
use various algorithms to determine the visibility of an object in a 3D
space. Or if a bullet fired in a direction will hit a given object or it
will get blocked by an obstacle in front of it. So it seemed to me it
probably should be feasible in HTML/CSS as well.

On Thu, Sep 3, 2015 at 8:42 AM Tab Atkins Jr. <jackalmage@gmail.com> wrote:

> On Tue, Aug 25, 2015 at 6:39 PM, Behrang Saeedzadeh <behrangsa@gmail.com>
> wrote:
> > Looks like at the moment DOM does not expose any properties that signify
> > whether an element has become hidden due to an overflow: hidden on their
> > parent element.
> >
> > Any chance of adding this feature to DOM?
>
> That's a result of CSS layout/rendering; it doesn't seem
> super-appropriate to add to the DOM.  It's also a bit troublesome; an
> element can be partially hidden, so when does this flag flip to true?
> It's also very specific; there are a ton of ways that an element can
> get hidden besides being clipped by an overflow:hidden ancestor.
> What's the actual use-case you're trying to address here?
>
> ~TJ
>
-- 
Best regards,
Behrang Saeedzadeh
Received on Thursday, 3 September 2015 10:26:53 UTC

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