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Re: [css3-backgrounds] Should a non-zero border-radius create a new stacking context ?

From: Robert O'Callahan <robert@ocallahan.org>
Date: Mon, 22 Nov 2010 12:58:36 +1300
Message-ID: <AANLkTinrnU7uULyuY_vaxOFtrFtTY-khdcnT_gCD8qOv@mail.gmail.com>
To: Sylvain Galineau <sylvaing@microsoft.com>
Cc: Brad Kemper <brad.kemper@gmail.com>, "www-style@w3.org" <www-style@w3.org>
I think it should be relatively easy to implement this without a major code
complexity penalty and without a performance penalty for pages that do not
use border-radius with non-visible 'overflow'. You already have to track
clip rects for the children of the element with non-visible 'overflow'. So
extend the abstraction from 'clip rect' to 'clip rect or the intersection of
a list of clip paths'.

I disagree with the argument that we should ease the implementation burden
by inducing a stacking context because we did for opacity < 1. I think we
induce a stacking context for opacity < 1 not because of implementation
issues, but because group opacity is meaningless if the elements in the
group are not contiguous in z-order ... at least, I don't know of any
rational way it could be defined.

I agree that making non-visible 'overflow' induce a stacking context would
have been a good idea, but it's too late now. Given we have to deal with
interleaving of clipped and non-clipped content, generalizing the clipping
shapes without adding strange new side effects seems the most reasonable
thing to do.

Rob
-- 
"Now the Bereans were of more noble character than the Thessalonians, for
they received the message with great eagerness and examined the Scriptures
every day to see if what Paul said was true." [Acts 17:11]
Received on Sunday, 21 November 2010 23:59:04 GMT

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