Re: [css3-writing-modes] inconsistent handling of 'Tr' codepoints in 'text-orientation'

On Tuesday, October 1, 2013, John Daggett wrote:

> But to some degree, proper vertical text rendering
> will always be dependent upon font resources, starting with
> appropriate vertical metrics through appropriate support for vertical
> alternates.  The reason I don't see OpenType feature fallback like
> this as compelling is that fonts intended to support vertical text
> generally *do* provide these alternates.


You have convinced me.

The way I would state it is that UTR#50 compliance should be treated as a
property of the layout engine together with the font, rather than of the
layout engine alone.  It is better to have an architecture where there is a
clear allocation of responsibility between subsystems.  When you have an
OpenType font that declares support for vertical alternates, it is better
to allocate responsibility for providing appropriate alternate glyphs to
the font alone rather than splitting it between the layout engine and the
font.

James