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Re: [CSS3 Text] shadow stacking levels

From: fantasai <fantasai.lists@inkedblade.net>
Date: Tue, 22 Jan 2008 17:05:51 -0500
Message-ID: <479668BF.5040809@inkedblade.net>
To: David Hyatt <hyatt@apple.com>
CC: www-style@w3.org, "L. David Baron" <dbaron@dbaron.org>

David Baron wrote:
>
> It sounds like you want all the shadows for an element to be painted
> at the same layer, so you should say that the text shadow for an
> element is painted (for all the text within it, including text
> inside descendant elements) in a layer after (above) its border and
> background, but for each text by the parent element of the text (so
> that the shadow moves with relative positioning).

That would work if text-shadow, like text-decoration, didn't inherit.
But last time we discussed it, we decided to make it inherit. I guess
that makes it easier to understand and implement, but harder to get
the overlapping edge cases right.

David Hyatt wrote:
> 
> In WebKit, we don't really have any control over when the shadow 
> paints.  It is drawn as a side effect of another drawing operation (in 
> this case the drawing of the text itself).  Therefore it is not drawn by 
> the parent element for us.  It's drawn by the same operation that draws 
> the text glyphs.
> I'd kind of prefer that this paint order either match what we do or 
> remain unspecified, since we really don't have any choice here.
> 
> It's important to understand this concept that shadows are a byproduct, 
> cast by an actual drawing operation.   It's just sensible graphics API 
> to have the shadow drawn at the same time the actual drawing operation 
> occurs so that the antialiasing etc. can be handled smoothly where the 
> shadow meets the glyphs.
> 
> I think we might be able to clip out the glyphs and draw (i.e., the hack 
> we did for box-shadow), but that would probably look bad at the edges of 
> the clip (as box-shadow looks bad today in WebKit).

Ok, I've added the following text:

   # The shadow must be painted behind the element's text but in front of
   # its visible background. UAs should avoid painting text shadows over
   # text in adjacent elements belonging to the same stack level and stacking
   # context.

Does that make sense?

~fantasai
Received on Wednesday, 23 January 2008 06:47:25 GMT

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