(this is a follow up from #8914 (comment))

While we have the ability to specify a precise angle of oblique fonts (thanks to font-style: normal | italic | oblique <angle [-90deg,90deg]>?), we don't seem to have a system to specify left vs right leaning italic or oblique fonts, which are desirable for i18n reasons (see w3c/afrlreq#17).

How about something like this:

• Expand the font-style descriptor in font-face letting you know if a (non-variable) oblique or italics font face is left or right leaning.
  Maybe: font-style: auto | normal | italic [left | right]? | oblique [left | right | <angle>{1,2}]?

  When you don't specify left nor right (on a non variable font), the ua should probably generally assume right, unless the font technology has some built in indicator.

• Expand the font-style property to let authors ask for a particular slant direction:
  Maybe: font-style: normal | italic [left | right]? | oblique [left | right | <angle>]?

  Then, if you've got italics (or oblique), but they're leaning the opposite way of what was requested, you don't use the provided font-face, and synthesize instead (if font-synthesis allows).