[ttml2] http://www.w3.org/ns/ttml/profile/imsc1/extension/#linePadding is not supported

palemieux has just created a new issue for 
https://github.com/w3c/ttml2:

== http://www.w3.org/ns/ttml/profile/imsc1/extension/#linePadding is 
not supported ==
To the extent that IMSC2 is intended to be subset of TTML2, TTML2 
needs to support 
`http://www.w3.org/ns/ttml/profile/imsc1/extension/#linePadding`.

While TTML2 adds support for padding on `span`, it is not equivalent 
to `#linePadding`. Specifically, `#linePadding` requires that the 
background of the first/last character of each line
be extended, regardless of whether the line was wrapped explicitly 
using `br`.

In contrast, `padding`, in the CSS/XSL sense, adds padding to the 
edges of the `span` regardless of whether the edge is actually on the 
start or end of a line. This means that additional gaps and color 
mismatch will be introduced if nested spans are used, even if 
`box-decoration-break: clone` is used.

See examples at https://codepen.io/palemieux/pen/vyzbqW.

Please view or discuss this issue at 
https://github.com/w3c/ttml2/issues/237 using your GitHub account

Received on Thursday, 26 January 2017 17:39:48 UTC