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[ttml2] Add support for rounded borders

From: Glenn Adams via GitHub <sysbot+gh@w3.org>
Date: Fri, 09 Sep 2016 00:02:19 +0000
To: public-tt@w3.org
Message-ID: <issues.opened-175894712-1473379337-sysbot+gh@w3.org>
skynavga has just created a new issue for 

== Add support for rounded borders ==
The use of rounded borders (or backgrounds) on caption/subtitle 
regions is becoming prominent. With the addition of ``tts:border`` in 
TTML2, we should also add support for rounded borders basing this 
support on features defined by CSS Backgrounds and Border Level 3 [1].
 Note that this feature may also be used to indicate the use of 
rounding with background coloration applied to regions or content 
elements, even when no border is drawn (since the default clip region 
for the _background painting area_ is the border region).

[1] https://drafts.csswg.org/css-backgrounds-3/#the-border-radius

The proposal is to add an optional ``<border-radii>`` component to the
 value syntax for ``tts:border`` as follows:

  : [ &lt;border-thickness&gt; || &lt;border-style&gt; || 
&lt;border-color&gt; || &lt;border-radii&gt; ]

  : 'radii(' &lt;length&gt; ( ',' &lt;length&gt; )? ')'

where, if two lengths are specified, then the first length corresponds
 to the quarter ellipse radius for the inline progression dimension 
(for content) or horizontal direction (for regions), while the second 
length, if present, corresponds to the quarter ellipse radius for the 
block progression dimension (for content) or vertical direction (for 
regions), or, if only one length is present, then it is interpreted as
 if two lengths were specified with the same value.

If a percentage value is used for a ``<length>``, then it is resolved 
with respect to the appropriate dimension of the border box's extent.

Please view or discuss this issue at 
https://github.com/w3c/ttml2/issues/176 using your GitHub account
Received on Friday, 9 September 2016 00:02:27 UTC

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