[whatwg] Questions about ::backdrop

Anne van Kesteren annevk at annevk.nl
Fri Jun 28 02:48:04 PDT 2013

On Fri, Jun 28, 2013 at 9:46 AM, Matt Falkenhagen <falken at chromium.org> wrote:
> I'm working on implementing the ::backdrop pseudo-element[1] for top
> layer elements such as modal <dialog> and have some questions.


> 1. Should ::backdrop have the same properties as a real top layer
> element, such as "Its containing block is the initial containing block."
> and "Ancestor elements with overflow, opacity, masks, etc. cannot affect
> it."?  It seems weird if a dialog is not affected by overflow, etc. and
> its ::backdrop is. It also may be convenient to position and size the
> backdrop relative to the ICB, like <dialog>. On the other hand, perhaps
> it's convenient in some use cases for ::backdrop to be positioned and
> sized relative to the <dialog>.

Clarified: https://github.com/whatwg/fullscreen/commit/319aea6ffe996ac97f49701075aa233966765e81

Hopefully in due course this will be properly part of CSS instead of
some hack on top, but we've been waiting on that for a while now so
don't get your hopes up :-)

> 2. Clicking on a pseudo-element causes a click event to be dispatched to
> its parent element. But this will make it unwieldy to implement
> behaviors like dismissing a modal dialog or "bouncing" it for attention
> when the area outside the dialog is clicked. Ideally you can easily
> determine whether the dialog or its ::backdrop was clicked. Can we
> perhaps use event.relatedTarget for this information?

Simon, Tab, what does CSSOM / CSS / hit testing say about this?
(Harhar, I know half of that is not defined, get on it!) (I'm assuming
this would also apply to e.g. ::before.)

> [1] http://fullscreen.spec.whatwg.org/#::backdrop-pseudo-element


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