Re: [ft-devel] FT_LOAD_VERTICAL_LAYOUT?

[Werner LEMBERG]

> freetype.h (and the online documentation) contains the following for
> FT_LOAD_VERTICAL_LAYOUT
>
>    *   FT_LOAD_VERTICAL_LAYOUT ::
>    *     Load the glyph for vertical text layout.  _Don't_ use it as
>    *     it is problematic currently.
>
> Is the warning still valid?
>
> If it is, in what ways is FT_LOAD_VERTICAL_LAYOUT "problematic"?

A good question.  I think it works now as expected.  Maybe it's best
to remove the warning and to wait for bug reports...

> And how should FreeType be used for vertical writing mode?

It should be the same as with horizontal mode under the assumption
that you apply both `advance.x' and `advance.y'.

A fundamental issue which has been discussed recently was the meaning
of the vertical component of the advance width in PostScript fonts.
The conclusion was to handle the x and y values given by the `sbw' (or
`hsbw') operator for the horizontal writing direction only; the PS
file itself is treated as if it never contains metric values for the
vertical writing direction.  You need an AFM file for that, containing
individual glyph metrics with `W1' or `W1Y' keys, for example.  Note,
however, that FreeType only gets kerning values from AFM files,
ignoring advance widths completely; IIRC, until now noone has ever
requested that we should handle the latter.


    Werner