====== text-orientation: sideways-left and sideways in CSS Writing Modes Level 3 ======

====== Background ======

  - [[http://dev.w3.org/csswg/css-writing-modes-3/#valdef-text-orientation-sideways-left|sideways-left]] is not implemented yet
    * sideways-left is for Latin and other non-East Asian vertical flow, while other values (mixed, upright, sideways-right) are important values for East Asian vertical flow.
  - [[http://dev.w3.org/csswg/css-writing-modes-3/#valdef-text-orientation-sideways|sideways]] has dependency on sideways-left, and thus is implemented differently from the spec by 3 implementations (AH, Blink, WebKit)
    * Mongolians must use sideways-right, not sideways, but the 3 implementations allow both.
  
====== Proposals ======

===== sideways-left =====

  - Keep as is
  - Mark at risk and put a note for attention not to implement the sideways value if you don't implement this value
  - Defer to Level 4

===== sideways =====

  - Keep as is
  - Mark at risk and put a note for attention not to implement this value differently from the spec
  - Change the spec to follow the interoperable 3 implementations (same behavior as sideways-right)
  - Defer to Level 4

====== Notes ======

  - [[https://lists.w3.org/Archives/Public/www-style/2015Jan/0130.html|www-style thread]]
  - Concerns of the value could prevent the property from being implemented because of its complexity.
  - IIUC, design concerns were raised 2-3 times before at F2F and offline, though I could not find them in the minutes.
  - IE is the only UA that supports the use case (though using the [[https://msdn.microsoft.com/en-us/library/ie/ms531187.aspx|writing-mode]] properly, not the text-orientation property.)
  - [[http://epub-revision.googlecode.com/svn/trunk/build/30/spec/epub30-contentdocs.html#sec-css-writing-modes|EPUB 3 CSS Profile]] refers to this property.