[ttml2] Sideways shouldn't be tied to tblr vs tbrl

r12a has just created a new issue for https://github.com/w3c/ttml2:

== Sideways shouldn't be tied to tblr vs tbrl ==
10.2.46 tts:textOrientation
http://w3c.github.io/ttml2/spec/ttml2.html#style-attribute-textOrientation

At the bottom of the section about textOrientation it says that 

> The semantics of the style property represented by this attribute are based upon that defined by [CSS Writing Modes], § 5.1.

but i think the CSS Writing Modes spec is now significantly different in approach, so TTML needs to be brought up to date with those changes.  

Note also that in CSS sideways applies to the 'vertical script' characters as well as the horizontal ones.

> If the value of this attribute is sideways, then, in vertical writing modes, glyphs from horizontal scripts are set sideways, either 90° clockwise or 90° counter-clockwise, according to whether the writing mode is tbrl or tblr, respectively. Glyphs from vertical scripts are not affected.

It's not clear to me why the tbrl and tblr settings should systematically trigger this difference in orientation unless this behaviour is intended to be used only for vertical lines of horizontal scripts.  For that, see my other recommendation that new values for writing-mode would be more appropriate, since just changing the orientation of characters doesn't address issues related to where the line start is or how to make, say, Latin text progress in the right direction along the line when tblr is the writing-mode value.

Please view or discuss this issue at https://github.com/w3c/ttml2/issues/280 using your GitHub account

Received on Monday, 13 March 2017 20:04:19 UTC