RE: [css3-writing-modes] text-orientation: upright (was RE: Minutes and Resolutions 2011-07-13

> From Koji Ishii
> (quoting the spec in [1])
>  * If the font and font system support mixed-orientation typesetting
>  (e.g. the Open >Type font used has the vrt2), the UA should rely on
> that feature to set 'vertical-right' text. Similarly if the font and font
>  system support upright typesetting (e.g. the OpenType font used
> has the vert feature) then the UA should rely on that feature to
> set 'upright' text.
It was for sure the intent of the original writing-mode spec in vertical mode to reproduce in its default value the behavior available on the Windows platform using the OpenType features and the '@font' selection in GDI. It works well in East Asian context with an East Asian font. 
>* If the UA needs to synthesize such features, then the settings in Appendix C are recommended.
> Appendix C is not easy, probably takes hours to review and understand.
>  I feel sorry about that, but it can't be helped because the feature isn't easy.

No doubt that emulating CJK vertical writing w/o OS and Font support is fiendishly hard. Many things need to be done right and typographic expectations are different between CJK constituencies that make that even harder. Using fonts dedicated to each market makes this easier.

Commenting on Annex C:
- East Asian width is a mere indicator of what should be wide or upright in vertical mode. The value is only an indication for symbols because it is not constant among East Asian fonts either through versions of the same font or across countries. In my last years as implementer I learnt to pretty much ignore the 'Ambiguous' value and override the other default value in many instances.
- The Unicode script value is vastly abused. It was never intended to be used straight as a mechanism to establish typographically correct layout. I don't mean it is not possible but you need to introduce a fairly large amount of analysis above it to make a decent job, especially when dealing with the common and inherit values.
- Same for the Unicode General Category property. 

Overall, I am glad that finally this part of the spec is coming to adoption after all these years. I am not active on this domain anymore but have kept interest in CSS work and I am following this list.

Michel Suignard


Received on Friday, 15 July 2011 16:53:00 UTC