[ttml1] Clarify the semantics of tts:fontSize="2em"

palemieux has just created a new issue for 
https://github.com/w3c/ttml1:

== Clarify the semantics of tts:fontSize="2em" ==
XSL, which TTML uses as a reference for 'em', states that "a relative 
length is a unit-based value that is measured against the current 
value of the font-size property" and "when the "font-size" property is
evaluated, the current font-size for use in evaluation is the 
font-size of the parent element"

While TTML does not specify a definition for the *current* value of 
tts:fontSize, using the computed value of tts:fontSize of the parent 
would be consistent with XSL and the definition of the percentage 
metric in TTML.

See also #206 

Please view or discuss this issue at 
https://github.com/w3c/ttml1/issues/214 using your GitHub account

Received on Monday, 19 September 2016 10:55:53 UTC