[css3-fonts] Synthesizing oblique, to which direction in RTL and vertical flow?

In the font-style property[1], it says:

  A value of 'italic' selects a font that is labeled 'italic',
  or, if that is not available, one labeled 'oblique'. If no
  italic or oblique faces is available, an oblique face can
  by synthesized by rendering the normal face with a
  sloping transformation applied.

But it does not state to which direction the slope should be.

There is no question for slope direction in LTR scripts, but is controversial for RTL and for vertical flow. Could this be clarified?

For RTL, there was a post to www-style in 1999[2], and there are some discussions on the web[3]. It looks to me that back-slant is the right way to go but I'm no experts here.

For vertical flow, there are several possibly right answers as in the picture here[4], and my investigation concluded that it varies by who you ask to:
a. Most word processor users consider #6 is the right answer.
b. Professional printers and font designers think differently by context; #2 or #6 for primarily Latin context such as citations, and #3 for primarily Japanese context. In addition, for primarily Japanese context, authors would like to specify directions and angles.
c. WebKit renders #8 today, and IE10 renders #6.

Thoughts?

[1] http://dev.w3.org/csswg/css3-fonts/#font-style-prop
[2] http://lists.w3.org/Archives/Public/www-style/1999Mar/0106.html
[3] http://typophile.com/node/49385?page=2
[4] http://koji.ec/archives/7

/koji

Received on Monday, 4 February 2013 06:39:00 UTC